upstream commit

adapt kex to sshbuf and struct ssh; ok djm@

24 files changed, 1704 insertions, 1156 deletions

diff --git a/auth.h b/auth.h
index c67e4a4d..60d1c335 100644
--- a/auth.h
+++ b/auth.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.h,v 1.79 2014/12/22 07:51:30 djm Exp $ */
+/* $OpenBSD: auth.h,v 1.80 2015/01/19 20:16:15 markus Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -42,6 +42,7 @@
 #include <krb5.h>
 #endif
 
+struct ssh;
 struct sshkey;
 
 typedef struct Authctxt Authctxt;
@@ -202,12 +203,12 @@ check_key_in_hostfiles(struct passwd *, Key *, const char *,
 
 /* hostkey handling */
 Key	*get_hostkey_by_index(int);
-Key	*get_hostkey_public_by_index(int);
-Key	*get_hostkey_public_by_type(int);
-Key	*get_hostkey_private_by_type(int);
-int	 get_hostkey_index(Key *);
+Key	*get_hostkey_public_by_index(int, struct ssh *);
+Key	*get_hostkey_public_by_type(int, struct ssh *);
+Key	*get_hostkey_private_by_type(int, struct ssh *);
+int	 get_hostkey_index(Key *, struct ssh *);
 int	 ssh1_session_key(BIGNUM *);
-void	 sshd_hostkey_sign(Key *, Key *, u_char **, u_int *, u_char *, u_int);
+int	 sshd_hostkey_sign(Key *, Key *, u_char **, size_t *, u_char *, size_t, u_int);
 
 /* debug messages during authentication */
 void	 auth_debug_add(const char *fmt,...) __attribute__((format(printf, 1, 2)));
diff --git a/clientloop.c b/clientloop.c
index 672d0698..5a018ac7 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.264 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: clientloop.c,v 1.265 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1413,8 +1413,7 @@ client_process_output(fd_set *writeset)
 static void
 client_process_buffered_input_packets(void)
 {
-	dispatch_run(DISPATCH_NONBLOCK, &quit_pending,
-	    compat20 ? active_state->kex : NULL);
+	dispatch_run(DISPATCH_NONBLOCK, &quit_pending, active_state);
 }
 
 /* scan buf[] for '~' before sending data to the peer */
@@ -1468,7 +1467,7 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id)
 {
 	fd_set *readset = NULL, *writeset = NULL;
 	double start_time, total_time;
-	int max_fd = 0, max_fd2 = 0, len, rekeying = 0;
+	int r, max_fd = 0, max_fd2 = 0, len, rekeying = 0;
 	u_int64_t ibytes, obytes;
 	u_int nalloc = 0;
 	char buf[100];
@@ -1598,7 +1597,9 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id)
 			if (need_rekeying || packet_need_rekeying()) {
 				debug("need rekeying");
 				active_state->kex->done = 0;
-				kex_send_kexinit(active_state->kex);
+				if ((r = kex_send_kexinit(active_state)) != 0)
+					fatal("%s: kex_send_kexinit: %s",
+					    __func__, ssh_err(r));
 				need_rekeying = 0;
 			}
 		}
diff --git a/dh.c b/dh.c
index 3331cda6..38ad615c 100644
--- a/dh.c
+++ b/dh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dh.c,v 1.53 2013/11/21 00:45:44 djm Exp $ */
+/* $OpenBSD: dh.c,v 1.54 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  *
@@ -39,6 +39,7 @@
 #include "pathnames.h"
 #include "log.h"
 #include "misc.h"
+#include "ssherr.h"
 
 static int
 parse_prime(int linenum, char *line, struct dhgroup *dhg)
@@ -107,10 +108,11 @@ parse_prime(int linenum, char *line, struct dhgroup *dhg)
 		goto fail;
 	}
 
-	if ((dhg->g = BN_new()) == NULL)
-		fatal("parse_prime: BN_new failed");
-	if ((dhg->p = BN_new()) == NULL)
-		fatal("parse_prime: BN_new failed");
+	if ((dhg->g = BN_new()) == NULL ||
+	    (dhg->p = BN_new()) == NULL) {
+		error("parse_prime: BN_new failed");
+		goto fail;
+	}
 	if (BN_hex2bn(&dhg->g, gen) == 0) {
 		error("moduli:%d: could not parse generator value", linenum);
 		goto fail;
@@ -128,7 +130,6 @@ parse_prime(int linenum, char *line, struct dhgroup *dhg)
 		error("moduli:%d: generator is invalid", linenum);
 		goto fail;
 	}
-
 	return 1;
 
  fail:
@@ -137,7 +138,6 @@ parse_prime(int linenum, char *line, struct dhgroup *dhg)
 	if (dhg->p != NULL)
 		BN_clear_free(dhg->p);
 	dhg->g = dhg->p = NULL;
-	error("Bad prime description in line %d", linenum);
 	return 0;
 }
 
@@ -200,9 +200,11 @@ choose_dh(int min, int wantbits, int max)
 		break;
 	}
 	fclose(f);
-	if (linenum != which+1)
-		fatal("WARNING: line %d disappeared in %s, giving up",
+	if (linenum != which+1) {
+		logit("WARNING: line %d disappeared in %s, giving up",
 		    which, _PATH_DH_PRIMES);
+		return (dh_new_group14());
+	}
 
 	return (dh_new_group(dhg.g, dhg.p));
 }
@@ -251,22 +253,22 @@ dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
 	return 0;
 }
 
-void
+int
 dh_gen_key(DH *dh, int need)
 {
 	int pbits;
 
-	if (need <= 0)
-		fatal("%s: need <= 0", __func__);
-	if (dh->p == NULL)
-		fatal("%s: dh->p == NULL", __func__);
-	if ((pbits = BN_num_bits(dh->p)) <= 0)
-		fatal("%s: bits(p) <= 0", __func__);
+	if (need < 0 || dh->p == NULL ||
+	    (pbits = BN_num_bits(dh->p)) <= 0 ||
+	    need > INT_MAX / 2 || 2 * need >= pbits)
+		return SSH_ERR_INVALID_ARGUMENT;
 	dh->length = MIN(need * 2, pbits - 1);
-	if (DH_generate_key(dh) == 0)
-		fatal("%s: key generation failed", __func__);
-	if (!dh_pub_is_valid(dh, dh->pub_key))
-		fatal("%s: generated invalid key", __func__);
+	if (DH_generate_key(dh) == 0 ||
+	    !dh_pub_is_valid(dh, dh->pub_key)) {
+		BN_clear_free(dh->priv_key);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	return 0;
 }
 
 DH *
@@ -275,13 +277,12 @@ dh_new_group_asc(const char *gen, const char *modulus)
 	DH *dh;
 
 	if ((dh = DH_new()) == NULL)
-		fatal("dh_new_group_asc: DH_new");
-
-	if (BN_hex2bn(&dh->p, modulus) == 0)
-		fatal("BN_hex2bn p");
-	if (BN_hex2bn(&dh->g, gen) == 0)
-		fatal("BN_hex2bn g");
-
+		return NULL;
+	if (BN_hex2bn(&dh->p, modulus) == 0 ||
+	    BN_hex2bn(&dh->g, gen) == 0) {
+		DH_free(dh);
+		return NULL;
+	}
 	return (dh);
 }
 
@@ -296,7 +297,7 @@ dh_new_group(BIGNUM *gen, BIGNUM *modulus)
 	DH *dh;
 
 	if ((dh = DH_new()) == NULL)
-		fatal("dh_new_group: DH_new");
+		return NULL;
 	dh->p = modulus;
 	dh->g = gen;
 
@@ -344,7 +345,7 @@ dh_new_group14(void)
  * from RFC4419 section 3.
  */
 
-int
+u_int
 dh_estimate(int bits)
 {
 	if (bits <= 112)
diff --git a/dh.h b/dh.h
index 48f7b68e..63a1b147 100644
--- a/dh.h
+++ b/dh.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: dh.h,v 1.11 2013/10/08 11:42:13 dtucker Exp $ */
+/* $OpenBSD: dh.h,v 1.12 2015/01/19 20:16:15 markus Exp $ */
 
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
@@ -38,10 +38,10 @@ DH	*dh_new_group(BIGNUM *, BIGNUM *);
 DH	*dh_new_group1(void);
 DH	*dh_new_group14(void);
 
-void	 dh_gen_key(DH *, int);
+int	 dh_gen_key(DH *, int);
 int	 dh_pub_is_valid(DH *, BIGNUM *);
 
-int	 dh_estimate(int);
+u_int	 dh_estimate(int);
 
 /* Min and max values from RFC4419. */
 #define DH_GRP_MIN	1024
diff --git a/kex.c b/kex.c
index 92ebaf73..9280dd3f 100644
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.101 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: kex.c,v 1.102 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -37,20 +37,22 @@
 #include <openssl/crypto.h>
 #endif
 
-#include "xmalloc.h"
 #include "ssh2.h"
-#include "buffer.h"
 #include "packet.h"
 #include "compat.h"
 #include "cipher.h"
-#include "key.h"
+#include "sshkey.h"
 #include "kex.h"
 #include "log.h"
 #include "mac.h"
 #include "match.h"
+#include "misc.h"
 #include "dispatch.h"
 #include "monitor.h"
 #include "roaming.h"
+
+#include "ssherr.h"
+#include "sshbuf.h"
 #include "digest.h"
 
 #if OPENSSL_VERSION_NUMBER >= 0x00907000L
@@ -62,12 +64,12 @@ extern const EVP_MD *evp_ssh_sha256(void);
 #endif
 
 /* prototype */
-static void kex_kexinit_finish(Kex *);
-static void kex_choose_conf(Kex *);
+static int kex_choose_conf(struct ssh *);
+static int kex_input_newkeys(int, u_int32_t, void *);
 
 struct kexalg {
 	char *name;
-	int type;
+	u_int type;
 	int ec_nid;
 	int hash_alg;
 };
@@ -99,7 +101,7 @@ static const struct kexalg kexalgs[] = {
 char *
 kex_alg_list(char sep)
 {
-	char *ret = NULL;
+	char *ret = NULL, *tmp;
 	size_t nlen, rlen = 0;
 	const struct kexalg *k;
 
@@ -107,7 +109,11 @@ kex_alg_list(char sep)
 		if (ret != NULL)
 			ret[rlen++] = sep;
 		nlen = strlen(k->name);
-		ret = xrealloc(ret, 1, rlen + nlen + 2);
+		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
+			free(ret);
+			return NULL;
+		}
+		ret = tmp;
 		memcpy(ret + rlen, k->name, nlen + 1);
 		rlen += nlen;
 	}
@@ -134,7 +140,8 @@ kex_names_valid(const char *names)
 
 	if (names == NULL || strcmp(names, "") == 0)
 		return 0;
-	s = cp = xstrdup(names);
+	if ((s = cp = strdup(names)) == NULL)
+		return 0;
 	for ((p = strsep(&cp, ",")); p && *p != '\0';
 	    (p = strsep(&cp, ","))) {
 		if (kex_alg_by_name(p) == NULL) {
@@ -149,56 +156,75 @@ kex_names_valid(const char *names)
 }
 
 /* put algorithm proposal into buffer */
-static void
-kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
+int
+kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
 {
 	u_int i;
+	int r;
+
+	sshbuf_reset(b);
 
-	buffer_clear(b);
 	/*
 	 * add a dummy cookie, the cookie will be overwritten by
 	 * kex_send_kexinit(), each time a kexinit is set
 	 */
-	for (i = 0; i < KEX_COOKIE_LEN; i++)
-		buffer_put_char(b, 0);
-	for (i = 0; i < PROPOSAL_MAX; i++)
-		buffer_put_cstring(b, proposal[i]);
-	buffer_put_char(b, 0);			/* first_kex_packet_follows */
-	buffer_put_int(b, 0);			/* uint32 reserved */
+	for (i = 0; i < KEX_COOKIE_LEN; i++) {
+		if ((r = sshbuf_put_u8(b, 0)) != 0)
+			return r;
+	}
+	for (i = 0; i < PROPOSAL_MAX; i++) {
+		if ((r = sshbuf_put_cstring(b, proposal[i])) != 0)
+			return r;
+	}
+	if ((r = sshbuf_put_u8(b, 0)) != 0 ||	/* first_kex_packet_follows */
+	    (r = sshbuf_put_u32(b, 0)) != 0)	/* uint32 reserved */
+		return r;
+	return 0;
 }
 
 /* parse buffer and return algorithm proposal */
-static char **
-kex_buf2prop(Buffer *raw, int *first_kex_follows)
+int
+kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp)
 {
-	Buffer b;
+	struct sshbuf *b = NULL;
+	u_char v;
 	u_int i;
-	char **proposal;
-
-	proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
-
-	buffer_init(&b);
-	buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
-	/* skip cookie */
-	for (i = 0; i < KEX_COOKIE_LEN; i++)
-		buffer_get_char(&b);
+	char **proposal = NULL;
+	int r;
+
+	*propp = NULL;
+	if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((b = sshbuf_fromb(raw)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */
+		goto out;
 	/* extract kex init proposal strings */
 	for (i = 0; i < PROPOSAL_MAX; i++) {
-		proposal[i] = buffer_get_cstring(&b,NULL);
+		if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0)
+			goto out;
 		debug2("kex_parse_kexinit: %s", proposal[i]);
 	}
 	/* first kex follows / reserved */
-	i = buffer_get_char(&b);
+	if ((r = sshbuf_get_u8(b, &v)) != 0 ||
+	    (r = sshbuf_get_u32(b, &i)) != 0)
+		goto out;
 	if (first_kex_follows != NULL)
 		*first_kex_follows = i;
-	debug2("kex_parse_kexinit: first_kex_follows %d ", i);
-	i = buffer_get_int(&b);
+	debug2("kex_parse_kexinit: first_kex_follows %d ", v);
 	debug2("kex_parse_kexinit: reserved %u ", i);
-	buffer_free(&b);
-	return proposal;
+	r = 0;
+	*propp = proposal;
+ out:
+	if (r != 0 && proposal != NULL)
+		kex_prop_free(proposal);
+	sshbuf_free(b);
+	return r;
 }
 
-static void
+void
 kex_prop_free(char **proposal)
 {
 	u_int i;
@@ -217,91 +243,103 @@ kex_protocol_error(int type, u_int32_t seq, void *ctxt)
 }
 
 static void
-kex_reset_dispatch(void)
+kex_reset_dispatch(struct ssh *ssh)
 {
-	dispatch_range(SSH2_MSG_TRANSPORT_MIN,
+	ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN,
 	    SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
-	dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
 }
 
-void
-kex_finish(Kex *kex)
+int
+kex_send_newkeys(struct ssh *ssh)
 {
-	kex_reset_dispatch();
+	int r;
 
-	packet_start(SSH2_MSG_NEWKEYS);
-	packet_send();
-	/* packet_write_wait(); */
+	kex_reset_dispatch(ssh);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		return r;
 	debug("SSH2_MSG_NEWKEYS sent");
-
 	debug("expecting SSH2_MSG_NEWKEYS");
-	packet_read_expect(SSH2_MSG_NEWKEYS);
-	packet_check_eom();
-	debug("SSH2_MSG_NEWKEYS received");
+	ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys);
+	return 0;
+}
+
+static int
+kex_input_newkeys(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	int r;
 
+	debug("SSH2_MSG_NEWKEYS received");
+	ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error);
+	if ((r = sshpkt_get_end(ssh)) != 0)
+		return r;
 	kex->done = 1;
-	buffer_clear(kex->peer);
-	/* buffer_clear(kex->my); */
+	sshbuf_reset(kex->peer);
+	/* sshbuf_reset(kex->my); */
 	kex->flags &= ~KEX_INIT_SENT;
 	free(kex->name);
 	kex->name = NULL;
+	return 0;
 }
 
-void
-kex_send_kexinit(Kex *kex)
+int
+kex_send_kexinit(struct ssh *ssh)
 {
-	u_int32_t rnd = 0;
 	u_char *cookie;
-	u_int i;
+	struct kex *kex = ssh->kex;
+	int r;
 
-	if (kex == NULL) {
-		error("kex_send_kexinit: no kex, cannot rekey");
-		return;
-	}
-	if (kex->flags & KEX_INIT_SENT) {
-		debug("KEX_INIT_SENT");
-		return;
-	}
+	if (kex == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	if (kex->flags & KEX_INIT_SENT)
+		return 0;
 	kex->done = 0;
 
 	/* generate a random cookie */
-	if (buffer_len(kex->my) < KEX_COOKIE_LEN)
-		fatal("kex_send_kexinit: kex proposal too short");
-	cookie = buffer_ptr(kex->my);
-	for (i = 0; i < KEX_COOKIE_LEN; i++) {
-		if (i % 4 == 0)
-			rnd = arc4random();
-		cookie[i] = rnd;
-		rnd >>= 8;
-	}
-	packet_start(SSH2_MSG_KEXINIT);
-	packet_put_raw(buffer_ptr(kex->my), buffer_len(kex->my));
-	packet_send();
+	if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
+		return SSH_ERR_INVALID_FORMAT;
+	if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	arc4random_buf(cookie, KEX_COOKIE_LEN);
+
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshpkt_putb(ssh, kex->my)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		return r;
 	debug("SSH2_MSG_KEXINIT sent");
 	kex->flags |= KEX_INIT_SENT;
+	return 0;
 }
 
 /* ARGSUSED */
 int
 kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
 {
-	const char *ptr;
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	const u_char *ptr;
 	u_int i;
 	size_t dlen;
-	Kex *kex = (Kex *)ctxt;
+	int r;
 
 	debug("SSH2_MSG_KEXINIT received");
 	if (kex == NULL)
-		fatal("kex_input_kexinit: no kex, cannot rekey");
+		return SSH_ERR_INVALID_ARGUMENT;
 
-	ptr = packet_get_raw(&dlen);
-	buffer_append(kex->peer, ptr, dlen);
+	ptr = sshpkt_ptr(ssh, &dlen);
+	if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
+		return r;
 
 	/* discard packet */
 	for (i = 0; i < KEX_COOKIE_LEN; i++)
-		packet_get_char();
+		if ((r = sshpkt_get_u8(ssh, NULL)) != 0)
+			return r;
 	for (i = 0; i < PROPOSAL_MAX; i++)
-		free(packet_get_string(NULL));
+		if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0)
+			return r;
 	/*
 	 * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported
 	 * KEX method has the server move first, but a server might be using
@@ -312,12 +350,47 @@ kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
 	 * for cases where the server *doesn't* go first. I guess we should
 	 * ignore it when it is set for these cases, which is what we do now.
 	 */
-	(void) packet_get_char();	/* first_kex_follows */
-	(void) packet_get_int();	/* reserved */
-	packet_check_eom();
+	if ((r = sshpkt_get_u8(ssh, NULL)) != 0 ||	/* first_kex_follows */
+	    (r = sshpkt_get_u32(ssh, NULL)) != 0 ||	/* reserved */
+	    (r = sshpkt_get_end(ssh)) != 0)
+			return r;
 
-	kex_kexinit_finish(kex);
-	return 0;
+	if (!(kex->flags & KEX_INIT_SENT))
+		if ((r = kex_send_kexinit(ssh)) != 0)
+			return r;
+	if ((r = kex_choose_conf(ssh)) != 0)
+		return r;
+
+	if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
+		return (kex->kex[kex->kex_type])(ssh);
+
+	return SSH_ERR_INTERNAL_ERROR;
+}
+
+int
+kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp)
+{
+	struct kex *kex;
+	int r;
+
+	*kexp = NULL;
+	if ((kex = calloc(1, sizeof(*kex))) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((kex->peer = sshbuf_new()) == NULL ||
+	    (kex->my = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = kex_prop2buf(kex->my, proposal)) != 0)
+		goto out;
+	kex->done = 0;
+	kex_reset_dispatch(ssh);
+	r = 0;
+	*kexp = kex;
+ out:
+	if (r != 0)
+		kex_free(kex);
+	return r;
 }
 
 void
@@ -351,51 +424,53 @@ kex_free_newkeys(struct newkeys *newkeys)
 	free(newkeys);
 }
 
-Kex *
-kex_setup(char *proposal[PROPOSAL_MAX])
+void
+kex_free(struct kex *kex)
 {
-	struct kex *kex;
+	u_int mode;
 
-	if ((kex = calloc(1, sizeof(*kex))) == NULL)
-		fatal("%s: calloc", __func__);
-	if ((kex->peer = sshbuf_new()) == NULL ||
-	    (kex->my = sshbuf_new()) == NULL) {
-		fatal("%s: sshbuf_new", __func__);
+#ifdef WITH_OPENSSL
+	if (kex->dh)
+		DH_free(kex->dh);
+	if (kex->ec_client_key)
+		EC_KEY_free(kex->ec_client_key);
+#endif
+	for (mode = 0; mode < MODE_MAX; mode++) {
+		kex_free_newkeys(kex->newkeys[mode]);
+		kex->newkeys[mode] = NULL;
 	}
-	kex_prop2buf(kex->my, proposal);
-	kex->done = 0;
-
-	kex_send_kexinit(kex);					/* we start */
-	kex_reset_dispatch();
-
-	return kex;
+	sshbuf_free(kex->peer);
+	sshbuf_free(kex->my);
+	free(kex->session_id);
+	free(kex->client_version_string);
+	free(kex->server_version_string);
+	free(kex);
 }
 
-static void
-kex_kexinit_finish(Kex *kex)
+int
+kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX])
 {
-	if (!(kex->flags & KEX_INIT_SENT))
-		kex_send_kexinit(kex);
-
-	kex_choose_conf(kex);
-
-	if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
-	    kex->kex[kex->kex_type] != NULL) {
-		(kex->kex[kex->kex_type])(kex);
-	} else {
-		fatal("Unsupported key exchange %d", kex->kex_type);
+	int r;
+
+	if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0)
+		return r;
+	if ((r = kex_send_kexinit(ssh)) != 0) {		/* we start */
+		kex_free(ssh->kex);
+		ssh->kex = NULL;
+		return r;
 	}
+	return 0;
 }
 
-static void
-choose_enc(Enc *enc, char *client, char *server)
+static int
+choose_enc(struct sshenc *enc, char *client, char *server)
 {
 	char *name = match_list(client, server, NULL);
+
 	if (name == NULL)
-		fatal("no matching cipher found: client %s server %s",
-		    client, server);
+		return SSH_ERR_NO_CIPHER_ALG_MATCH;
 	if ((enc->cipher = cipher_by_name(name)) == NULL)
-		fatal("matching cipher is not supported: %s", name);
+		return SSH_ERR_INTERNAL_ERROR;
 	enc->name = name;
 	enc->enabled = 0;
 	enc->iv = NULL;
@@ -403,31 +478,34 @@ choose_enc(Enc *enc, char *client, char *server)
 	enc->key = NULL;
 	enc->key_len = cipher_keylen(enc->cipher);
 	enc->block_size = cipher_blocksize(enc->cipher);
+	return 0;
 }
 
-static void
-choose_mac(Mac *mac, char *client, char *server)
+static int
+choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server)
 {
 	char *name = match_list(client, server, NULL);
+
 	if (name == NULL)
-		fatal("no matching mac found: client %s server %s",
-		    client, server);
+		return SSH_ERR_NO_MAC_ALG_MATCH;
 	if (mac_setup(mac, name) < 0)
-		fatal("unsupported mac %s", name);
+		return SSH_ERR_INTERNAL_ERROR;
 	/* truncate the key */
-	if (datafellows & SSH_BUG_HMAC)
+	if (ssh->compat & SSH_BUG_HMAC)
 		mac->key_len = 16;
 	mac->name = name;
 	mac->key = NULL;
 	mac->enabled = 0;
+	return 0;
 }
 
-static void
-choose_comp(Comp *comp, char *client, char *server)
+static int
+choose_comp(struct sshcomp *comp, char *client, char *server)
 {
 	char *name = match_list(client, server, NULL);
+
 	if (name == NULL)
-		fatal("no matching comp found: client %s server %s", client, server);
+		return SSH_ERR_NO_COMPRESS_ALG_MATCH;
 	if (strcmp(name, "zlib@openssh.com") == 0) {
 		comp->type = COMP_DELAYED;
 	} else if (strcmp(name, "zlib") == 0) {
@@ -435,36 +513,41 @@ choose_comp(Comp *comp, char *client, char *server)
 	} else if (strcmp(name, "none") == 0) {
 		comp->type = COMP_NONE;
 	} else {
-		fatal("unsupported comp %s", name);
+		return SSH_ERR_INTERNAL_ERROR;
 	}
 	comp->name = name;
+	return 0;
 }
 
-static void
-choose_kex(Kex *k, char *client, char *server)
+static int
+choose_kex(struct kex *k, char *client, char *server)
 {
 	const struct kexalg *kexalg;
 
 	k->name = match_list(client, server, NULL);
+
 	if (k->name == NULL)
-		fatal("Unable to negotiate a key exchange method");
+		return SSH_ERR_NO_KEX_ALG_MATCH;
 	if ((kexalg = kex_alg_by_name(k->name)) == NULL)
-		fatal("unsupported kex alg %s", k->name);
+		return SSH_ERR_INTERNAL_ERROR;
 	k->kex_type = kexalg->type;
 	k->hash_alg = kexalg->hash_alg;
 	k->ec_nid = kexalg->ec_nid;
+	return 0;
 }
 
-static void
-choose_hostkeyalg(Kex *k, char *client, char *server)
+static int
+choose_hostkeyalg(struct kex *k, char *client, char *server)
 {
 	char *hostkeyalg = match_list(client, server, NULL);
+
 	if (hostkeyalg == NULL)
-		fatal("no hostkey alg");
-	k->hostkey_type = key_type_from_name(hostkeyalg);
+		return SSH_ERR_NO_HOSTKEY_ALG_MATCH;
+	k->hostkey_type = sshkey_type_from_name(hostkeyalg);
 	if (k->hostkey_type == KEY_UNSPEC)
-		fatal("bad hostkey alg '%s'", hostkeyalg);
+		return SSH_ERR_INTERNAL_ERROR;
 	free(hostkeyalg);
+	return 0;
 }
 
 static int
@@ -491,18 +574,20 @@ proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
 	return (1);
 }
 
-static void
-kex_choose_conf(Kex *kex)
+static int
+kex_choose_conf(struct ssh *ssh)
 {
-	Newkeys *newkeys;
-	char **my, **peer;
+	struct kex *kex = ssh->kex;
+	struct newkeys *newkeys;
+	char **my = NULL, **peer = NULL;
 	char **cprop, **sprop;
 	int nenc, nmac, ncomp;
 	u_int mode, ctos, need, dh_need, authlen;
-	int first_kex_follows, type;
+	int r, first_kex_follows;
 
-	my   = kex_buf2prop(kex->my, NULL);
-	peer = kex_buf2prop(kex->peer, &first_kex_follows);
+	if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0 ||
+	    (r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0)
+		goto out;
 
 	if (kex->server) {
 		cprop=peer;
@@ -514,8 +599,9 @@ kex_choose_conf(Kex *kex)
 
 	/* Check whether server offers roaming */
 	if (!kex->server) {
-		char *roaming;
-		roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
+		char *roaming = match_list(KEX_RESUME,
+		    peer[PROPOSAL_KEX_ALGS], NULL);
+
 		if (roaming) {
 			kex->roaming = 1;
 			free(roaming);
@@ -524,28 +610,39 @@ kex_choose_conf(Kex *kex)
 
 	/* Algorithm Negotiation */
 	for (mode = 0; mode < MODE_MAX; mode++) {
-		newkeys = xcalloc(1, sizeof(*newkeys));
+		if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		kex->newkeys[mode] = newkeys;
 		ctos = (!kex->server && mode == MODE_OUT) ||
 		    (kex->server && mode == MODE_IN);
 		nenc  = ctos ? PROPOSAL_ENC_ALGS_CTOS  : PROPOSAL_ENC_ALGS_STOC;
 		nmac  = ctos ? PROPOSAL_MAC_ALGS_CTOS  : PROPOSAL_MAC_ALGS_STOC;
 		ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
-		choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc]);
-		/* ignore mac for authenticated encryption */
+		if ((r = choose_enc(&newkeys->enc, cprop[nenc],
+		    sprop[nenc])) != 0)
+			goto out;
 		authlen = cipher_authlen(newkeys->enc.cipher);
-		if (authlen == 0)
-			choose_mac(&newkeys->mac, cprop[nmac], sprop[nmac]);
-		choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
+		/* ignore mac for authenticated encryption */
+		if (authlen == 0 &&
+		    (r = choose_mac(ssh, &newkeys->mac, cprop[nmac],
+		    sprop[nmac])) != 0)
+			goto out;
+		if ((r = choose_comp(&newkeys->comp, cprop[ncomp],
+		    sprop[ncomp])) != 0)
+			goto out;
 		debug("kex: %s %s %s %s",
 		    ctos ? "client->server" : "server->client",
 		    newkeys->enc.name,
 		    authlen == 0 ? newkeys->mac.name : "<implicit>",
 		    newkeys->comp.name);
 	}
-	choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
-	choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
-	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
+	if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS],
+	    sprop[PROPOSAL_KEX_ALGS])) != 0 ||
+	    (r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
+	    sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0)
+		goto out;
 	need = dh_need = 0;
 	for (mode = 0; mode < MODE_MAX; mode++) {
 		newkeys = kex->newkeys[mode];
@@ -564,45 +661,47 @@ kex_choose_conf(Kex *kex)
 
 	/* ignore the next message if the proposals do not match */
 	if (first_kex_follows && !proposals_match(my, peer) &&
-	    !(datafellows & SSH_BUG_FIRSTKEX)) {
-		type = packet_read();
-		debug2("skipping next packet (type %u)", type);
-	}
-
+	    !(ssh->compat & SSH_BUG_FIRSTKEX))
+		ssh->dispatch_skip_packets = 1;
+	r = 0;
+ out:
 	kex_prop_free(my);
 	kex_prop_free(peer);
+	return r;
 }
 
-static u_char *
-derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
-    const u_char *shared_secret, u_int slen)
+static int
+derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
+    const struct sshbuf *shared_secret, u_char **keyp)
 {
-	Buffer b;
-	struct ssh_digest_ctx *hashctx;
+	struct kex *kex = ssh->kex;
+	struct ssh_digest_ctx *hashctx = NULL;
 	char c = id;
 	u_int have;
 	size_t mdsz;
 	u_char *digest;
+	int r;
 
 	if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
-		fatal("bad kex md size %zu", mdsz);
-	digest = xmalloc(roundup(need, mdsz));
-
-	buffer_init(&b);
-	buffer_append(&b, shared_secret, slen);
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((digest = calloc(1, roundup(need, mdsz))) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 
 	/* K1 = HASH(K || H || "A" || session_id) */
-	if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
-		fatal("%s: ssh_digest_start failed", __func__);
-	if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
+	if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
+	    ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
 	    ssh_digest_update(hashctx, hash, hashlen) != 0 ||
 	    ssh_digest_update(hashctx, &c, 1) != 0 ||
 	    ssh_digest_update(hashctx, kex->session_id,
-	    kex->session_id_len) != 0)
-		fatal("%s: ssh_digest_update failed", __func__);
-	if (ssh_digest_final(hashctx, digest, mdsz) != 0)
-		fatal("%s: ssh_digest_final failed", __func__);
+	    kex->session_id_len) != 0 ||
+	    ssh_digest_final(hashctx, digest, mdsz) != 0) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	ssh_digest_free(hashctx);
+	hashctx = NULL;
 
 	/*
 	 * expand key:
@@ -610,38 +709,49 @@ derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
 	 * Key = K1 || K2 || ... || Kn
 	 */
 	for (have = mdsz; need > have; have += mdsz) {
-		if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
-			fatal("%s: ssh_digest_start failed", __func__);
-		if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
+		if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
+		    ssh_digest_update_buffer(hashctx, shared_secret) != 0 ||
 		    ssh_digest_update(hashctx, hash, hashlen) != 0 ||
-		    ssh_digest_update(hashctx, digest, have) != 0)
-			fatal("%s: ssh_digest_update failed", __func__);
-		if (ssh_digest_final(hashctx, digest + have, mdsz) != 0)
-			fatal("%s: ssh_digest_final failed", __func__);
+		    ssh_digest_update(hashctx, digest, have) != 0 ||
+		    ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
+			r = SSH_ERR_LIBCRYPTO_ERROR;
+			goto out;
+		}
 		ssh_digest_free(hashctx);
+		hashctx = NULL;
 	}
-	buffer_free(&b);
 #ifdef DEBUG_KEX
 	fprintf(stderr, "key '%c'== ", c);
 	dump_digest("key", digest, need);
 #endif
-	return digest;
+	*keyp = digest;
+	digest = NULL;
+	r = 0;
+ out:
+	if (digest)
+		free(digest);
+	ssh_digest_free(hashctx);
+	return r;
 }
 
 #define NKEYS	6
-void
-kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen,
-    const u_char *shared_secret, u_int slen)
+int
+kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
+    const struct sshbuf *shared_secret)
 {
+	struct kex *kex = ssh->kex;
 	u_char *keys[NKEYS];
-	u_int i, mode, ctos;
+	u_int i, j, mode, ctos;
+	int r;
 
 	for (i = 0; i < NKEYS; i++) {
-		keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
-		    shared_secret, slen);
+		if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,
+		    shared_secret, &keys[i])) != 0) {
+			for (j = 0; j < i; j++)
+				free(keys[j]);
+			return r;
+		}
 	}
-
-	debug2("kex_derive_keys");
 	for (mode = 0; mode < MODE_MAX; mode++) {
 		ctos = (!kex->server && mode == MODE_OUT) ||
 		    (kex->server && mode == MODE_IN);
@@ -649,54 +759,54 @@ kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen,
 		kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3];
 		kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5];
 	}
+	return 0;
 }
 
 #ifdef WITH_OPENSSL
-void
-kex_derive_keys_bn(Kex *kex, u_char *hash, u_int hashlen, const BIGNUM *secret)
+int
+kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen,
+    const BIGNUM *secret)
 {
-	Buffer shared_secret;
-
-	buffer_init(&shared_secret);
-	buffer_put_bignum2(&shared_secret, secret);
-	kex_derive_keys(kex, hash, hashlen,
-	    buffer_ptr(&shared_secret), buffer_len(&shared_secret));
-	buffer_free(&shared_secret);
+	struct sshbuf *shared_secret;
+	int r;
+
+	if ((shared_secret = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0)
+		r = kex_derive_keys(ssh, hash, hashlen, shared_secret);
+	sshbuf_free(shared_secret);
+	return r;
 }
 #endif
 
 #ifdef WITH_SSH1
-void
+int
 derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
     u_int8_t cookie[8], u_int8_t id[16])
 {
 	u_int8_t nbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
-	int len;
-	struct ssh_digest_ctx *hashctx;
-
-	if ((hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL)
-		fatal("%s: ssh_digest_start", __func__);
+	struct ssh_digest_ctx *hashctx = NULL;
+	size_t len;
+	int r;
 
 	len = BN_num_bytes(host_modulus);
 	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
-		fatal("%s: bad host modulus (len %d)", __func__, len);
-	BN_bn2bin(host_modulus, nbuf);
-	if (ssh_digest_update(hashctx, nbuf, len) != 0)
-		fatal("%s: ssh_digest_update failed", __func__);
-
-	len = BN_num_bytes(server_modulus);
-	if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
-		fatal("%s: bad server modulus (len %d)", __func__, len);
-	BN_bn2bin(server_modulus, nbuf);
-	if (ssh_digest_update(hashctx, nbuf, len) != 0 ||
-	    ssh_digest_update(hashctx, cookie, 8) != 0)
-		fatal("%s: ssh_digest_update failed", __func__);
-	if (ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0)
-		fatal("%s: ssh_digest_final failed", __func__);
+		return SSH_ERR_KEY_BITS_MISMATCH;
+	if (BN_bn2bin(host_modulus, nbuf) <= 0 ||
+	    (hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
+	    ssh_digest_update(hashctx, nbuf, len) != 0 ||
+	    ssh_digest_update(hashctx, cookie, 8) != 0 ||
+	    ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
-
+	r = 0;
+ out:
+	ssh_digest_free(hashctx);
 	explicit_bzero(nbuf, sizeof(nbuf));
 	explicit_bzero(obuf, sizeof(obuf));
+	return r;
 }
 #endif
 
@@ -704,16 +814,7 @@ derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
 void
 dump_digest(char *msg, u_char *digest, int len)
 {
-	int i;
-
 	fprintf(stderr, "%s\n", msg);
-	for (i = 0; i < len; i++) {
-		fprintf(stderr, "%02x", digest[i]);
-		if (i%32 == 31)
-			fprintf(stderr, "\n");
-		else if (i%8 == 7)
-			fprintf(stderr, " ");
-	}
-	fprintf(stderr, "\n");
+	sshbuf_dump_data(digest, len, stderr);
 }
 #endif
diff --git a/kex.h b/kex.h
index 1f7c824b..1798eea4 100644
--- a/kex.h
+++ b/kex.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.68 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: kex.h,v 1.69 2015/01/19 20:16:15 markus Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -30,8 +30,8 @@
 #include "buffer.h" /* XXX for typedef */
 #include "key.h" /* XXX for typedef */
 
-#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
-#include <openssl/ec.h>
+#ifdef WITH_LEAKMALLOC
+#include "leakmalloc.h"
 #endif
 
 #define KEX_COOKIE_LEN	16
@@ -50,6 +50,8 @@
 #define COMP_ZLIB	1
 #define COMP_DELAYED	2
 
+#define CURVE25519_SIZE 32
+
 enum kex_init_proposals {
 	PROPOSAL_KEX_ALGS,
 	PROPOSAL_SERVER_HOST_KEY_ALGS,
@@ -82,12 +84,6 @@ enum kex_exchange {
 
 #define KEX_INIT_SENT	0x0001
 
-typedef struct kex Kex;
-typedef struct sshcomp Comp;
-typedef struct sshmac Mac;
-typedef struct sshenc Enc;
-typedef struct newkeys Newkeys;
-
 struct sshenc {
 	char	*name;
 	const struct sshcipher *cipher;
@@ -106,8 +102,11 @@ struct sshcomp {
 struct newkeys {
 	struct sshenc	enc;
 	struct sshmac	mac;
-	struct sshcomp	comp;
+	struct sshcomp  comp;
 };
+
+struct ssh;
+
 struct kex {
 	u_char	*session_id;
 	size_t	session_id_len;
@@ -117,73 +116,87 @@ struct kex {
 	int	server;
 	char	*name;
 	int	hostkey_type;
-	int	kex_type;
+	u_int	kex_type;
 	int	roaming;
 	struct sshbuf *my;
 	struct sshbuf *peer;
 	sig_atomic_t done;
-	int	flags;
+	u_int	flags;
 	int	hash_alg;
 	int	ec_nid;
 	char	*client_version_string;
 	char	*server_version_string;
-	int	(*verify_host_key)(Key *);
-	Key	*(*load_host_public_key)(int);
-	Key	*(*load_host_private_key)(int);
-	int	(*host_key_index)(Key *);
-	void    (*sign)(Key *, Key *, u_char **, u_int *, u_char *, u_int);
-	void	(*kex[KEX_MAX])(Kex *);
+	int	(*verify_host_key)(struct sshkey *, struct ssh *);
+	struct sshkey *(*load_host_public_key)(int, struct ssh *);
+	struct sshkey *(*load_host_private_key)(int, struct ssh *);
+	int	(*host_key_index)(struct sshkey *, struct ssh *);
+	int	(*sign)(struct sshkey *, struct sshkey *,
+	    u_char **, size_t *, u_char *, size_t, u_int);
+	int	(*kex[KEX_MAX])(struct ssh *);
+	/* kex specific state */
+	DH	*dh;			/* DH */
+	u_int	min, max, nbits;	/* GEX */
+	EC_KEY	*ec_client_key;		/* ECDH */
+	const EC_GROUP *ec_group;	/* ECDH */
+	u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 */
+	u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
 };
 
 int	 kex_names_valid(const char *);
 char	*kex_alg_list(char);
 
-Kex	*kex_setup(char *[PROPOSAL_MAX]);
-void	 kex_finish(Kex *);
-void     kex_free_newkeys(struct newkeys *);
+int	 kex_new(struct ssh *, char *[PROPOSAL_MAX], struct kex **);
+int	 kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
+void	 kex_free_newkeys(struct newkeys *);
+void	 kex_free(struct kex *);
 
-void	 kex_send_kexinit(Kex *);
-int	 kex_input_kexinit(int, u_int32_t, void *);
-void	 kex_derive_keys(Kex *, u_char *, u_int, const u_char *, u_int);
-void	 kex_derive_keys_bn(Kex *, u_char *, u_int, const BIGNUM *);
-
-void	 kexdh_client(Kex *);
-void	 kexdh_server(Kex *);
-void	 kexgex_client(Kex *);
-void	 kexgex_server(Kex *);
-void	 kexecdh_client(Kex *);
-void	 kexecdh_server(Kex *);
-void	 kexc25519_client(Kex *);
-void	 kexc25519_server(Kex *);
-
-void
-kex_dh_hash(char *, char *, char *, int, char *, int, u_char *, int,
-    BIGNUM *, BIGNUM *, BIGNUM *, u_char **, u_int *);
-void
-kexgex_hash(int, char *, char *, char *, int, char *,
-    int, u_char *, int, int, int, int, BIGNUM *, BIGNUM *, BIGNUM *,
-    BIGNUM *, BIGNUM *, u_char **, u_int *);
-#ifdef OPENSSL_HAS_ECC
-void
-kex_ecdh_hash(int, const EC_GROUP *, char *, char *, char *, int,
-    char *, int, u_char *, int, const EC_POINT *, const EC_POINT *,
-    const BIGNUM *, u_char **, u_int *);
-#endif
-void
-kex_c25519_hash(int, char *, char *, char *, int,
-    char *, int, u_char *, int, const u_char *, const u_char *,
-    const u_char *, u_int, u_char **, u_int *);
+int	 kex_buf2prop(struct sshbuf *, int *, char ***);
+int	 kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
+void	 kex_prop_free(char **);
 
-#define CURVE25519_SIZE 32
-void	kexc25519_keygen(u_char[CURVE25519_SIZE], u_char[CURVE25519_SIZE])
+int	 kex_send_kexinit(struct ssh *);
+int	 kex_input_kexinit(int, u_int32_t, void *);
+int	 kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
+int	 kex_derive_keys_bn(struct ssh *, u_char *, u_int, const BIGNUM *);
+int	 kex_send_newkeys(struct ssh *);
+
+int	 kexdh_client(struct ssh *);
+int	 kexdh_server(struct ssh *);
+int	 kexgex_client(struct ssh *);
+int	 kexgex_server(struct ssh *);
+int	 kexecdh_client(struct ssh *);
+int	 kexecdh_server(struct ssh *);
+int	 kexc25519_client(struct ssh *);
+int	 kexc25519_server(struct ssh *);
+
+int	 kex_dh_hash(const char *, const char *,
+    const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
+    const BIGNUM *, const BIGNUM *, const BIGNUM *, u_char *, size_t *);
+
+int	 kexgex_hash(int, const char *, const char *,
+    const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
+    int, int, int,
+    const BIGNUM *, const BIGNUM *, const BIGNUM *,
+    const BIGNUM *, const BIGNUM *,
+    u_char *, size_t *);
+
+int kex_ecdh_hash(int, const EC_GROUP *, const char *, const char *,
+    const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
+    const EC_POINT *, const EC_POINT *, const BIGNUM *, u_char *, size_t *);
+
+int	 kex_c25519_hash(int, const char *, const char *, const char *, size_t,
+    const char *, size_t, const u_char *, size_t, const u_char *, const u_char *,
+    const u_char *, size_t, u_char *, size_t *);
+
+void	kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
-void kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
-    const u_char pub[CURVE25519_SIZE], Buffer *out)
+int	kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
+    const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
 
-void
+int
 derive_ssh1_session_id(BIGNUM *, BIGNUM *, u_int8_t[8], u_int8_t[16]);
 
 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
diff --git a/kexc25519.c b/kexc25519.c
index e3afa005..b6e6c401 100644
--- a/kexc25519.c
+++ b/kexc25519.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexc25519.c,v 1.7 2014/05/02 03:27:54 djm Exp $ */
+/* $OpenBSD: kexc25519.c,v 1.8 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001, 2013 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -35,13 +35,14 @@
 #include <openssl/bn.h>
 #include <openssl/evp.h>
 
-#include "buffer.h"
+#include "sshbuf.h"
 #include "ssh2.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
 #include "kex.h"
 #include "log.h"
 #include "digest.h"
+#include "ssherr.h"
 
 extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
     const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
@@ -58,65 +59,70 @@ kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
 	crypto_scalarmult_curve25519(pub, key, basepoint);
 }
 
-void
+int
 kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
-    const u_char pub[CURVE25519_SIZE], Buffer *out)
+    const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
 {
 	u_char shared_key[CURVE25519_SIZE];
+	int r;
 
 	crypto_scalarmult_curve25519(shared_key, key, pub);
 #ifdef DEBUG_KEXECDH
 	dump_digest("shared secret", shared_key, CURVE25519_SIZE);
 #endif
-	buffer_clear(out);
-	buffer_put_bignum2_from_string(out, shared_key, CURVE25519_SIZE);
+	sshbuf_reset(out);
+	r = sshbuf_put_bignum2_bytes(out, shared_key, CURVE25519_SIZE);
 	explicit_bzero(shared_key, CURVE25519_SIZE);
+	return r;
 }
 
-void
+int
 kex_c25519_hash(
     int hash_alg,
-    char *client_version_string,
-    char *server_version_string,
-    char *ckexinit, int ckexinitlen,
-    char *skexinit, int skexinitlen,
-    u_char *serverhostkeyblob, int sbloblen,
+    const char *client_version_string,
+    const char *server_version_string,
+    const char *ckexinit, size_t ckexinitlen,
+    const char *skexinit, size_t skexinitlen,
+    const u_char *serverhostkeyblob, size_t sbloblen,
     const u_char client_dh_pub[CURVE25519_SIZE],
     const u_char server_dh_pub[CURVE25519_SIZE],
-    const u_char *shared_secret, u_int secretlen,
-    u_char **hash, u_int *hashlen)
+    const u_char *shared_secret, size_t secretlen,
+    u_char *hash, size_t *hashlen)
 {
-	Buffer b;
-	static u_char digest[SSH_DIGEST_MAX_LENGTH];
-
-	buffer_init(&b);
-	buffer_put_cstring(&b, client_version_string);
-	buffer_put_cstring(&b, server_version_string);
-
-	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-	buffer_put_int(&b, ckexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, ckexinit, ckexinitlen);
-	buffer_put_int(&b, skexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, skexinit, skexinitlen);
-
-	buffer_put_string(&b, serverhostkeyblob, sbloblen);
-	buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
-	buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
-	buffer_append(&b, shared_secret, secretlen);
-
+	struct sshbuf *b;
+	int r;
+
+	if (*hashlen < ssh_digest_bytes(hash_alg))
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((b = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_cstring(b, client_version_string)) < 0 ||
+	    (r = sshbuf_put_cstring(b, server_version_string)) < 0 ||
+	    /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	    (r = sshbuf_put_u32(b, ckexinitlen+1)) < 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 ||
+	    (r = sshbuf_put(b, ckexinit, ckexinitlen)) < 0 ||
+	    (r = sshbuf_put_u32(b, skexinitlen+1)) < 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 ||
+	    (r = sshbuf_put(b, skexinit, skexinitlen)) < 0 ||
+	    (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) < 0 ||
+	    (r = sshbuf_put_string(b, client_dh_pub, CURVE25519_SIZE)) < 0 ||
+	    (r = sshbuf_put_string(b, server_dh_pub, CURVE25519_SIZE)) < 0 ||
+	    (r = sshbuf_put(b, shared_secret, secretlen)) < 0) {
+		sshbuf_free(b);
+		return r;
+	}
 #ifdef DEBUG_KEX
-	buffer_dump(&b);
+	sshbuf_dump(b, stderr);
 #endif
-	if (ssh_digest_buffer(hash_alg, &b, digest, sizeof(digest)) != 0)
-		fatal("%s: digest_buffer failed", __func__);
-
-	buffer_free(&b);
-
+	if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
+		sshbuf_free(b);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	sshbuf_free(b);
+	*hashlen = ssh_digest_bytes(hash_alg);
 #ifdef DEBUG_KEX
-	dump_digest("hash", digest, ssh_digest_bytes(hash_alg));
+	dump_digest("hash", hash, *hashlen);
 #endif
-	*hash = digest;
-	*hashlen = ssh_digest_bytes(hash_alg);
+	return 0;
 }
diff --git a/kexc25519c.c b/kexc25519c.c
index ffb537ef..833ce054 100644
--- a/kexc25519c.c
+++ b/kexc25519c.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexc25519c.c,v 1.5 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexc25519c.c,v 1.6 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -33,97 +33,136 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "ssh2.h"
+#include "sshbuf.h"
+#include "digest.h"
+#include "ssherr.h"
 
-void
-kexc25519_client(Kex *kex)
-{
-	Key *server_host_key;
-	u_char client_key[CURVE25519_SIZE];
-	u_char client_pubkey[CURVE25519_SIZE];
-	u_char *server_pubkey = NULL;
-	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *hash;
-	u_int slen, sbloblen, hashlen;
-	Buffer shared_secret;
-
-	kexc25519_keygen(client_key, client_pubkey);
+static int
+input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt);
 
-	packet_start(SSH2_MSG_KEX_ECDH_INIT);
-	packet_put_string(client_pubkey, sizeof(client_pubkey));
-	packet_send();
-	debug("sending SSH2_MSG_KEX_ECDH_INIT");
+int
+kexc25519_client(struct ssh *ssh)
+{
+	struct kex *kex = ssh->kex;
+	int r;
 
+	kexc25519_keygen(kex->c25519_client_key, kex->c25519_client_pubkey);
 #ifdef DEBUG_KEXECDH
-	dump_digest("client private key:", client_key, sizeof(client_key));
+	dump_digest("client private key:", kex->c25519_client_key,
+	    sizeof(kex->c25519_client_key));
 #endif
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
+	    (r = sshpkt_put_string(ssh, kex->c25519_client_pubkey,
+	    sizeof(kex->c25519_client_pubkey))) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		return r;
 
 	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
-	packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_c25519_reply);
+	return 0;
+}
+
+static int
+input_kex_c25519_reply(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	struct sshkey *server_host_key = NULL;
+	struct sshbuf *shared_secret = NULL;
+	u_char *server_pubkey = NULL;
+	u_char *server_host_key_blob = NULL, *signature = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t slen, pklen, sbloblen, hashlen;
+	int r;
+
+	if (kex->verify_host_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
 
 	/* hostkey */
-	server_host_key_blob = packet_get_string(&sbloblen);
-	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
-	if (server_host_key == NULL)
-		fatal("cannot decode server_host_key_blob");
-	if (server_host_key->type != kex->hostkey_type)
-		fatal("type mismatch for decoded server_host_key_blob");
-	if (kex->verify_host_key == NULL)
-		fatal("cannot verify server_host_key");
-	if (kex->verify_host_key(server_host_key) == -1)
-		fatal("server_host_key verification failed");
+	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+	    &sbloblen)) != 0 ||
+	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
+	    &server_host_key)) != 0)
+		goto out;
+	if (server_host_key->type != kex->hostkey_type) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (kex->verify_host_key(server_host_key, ssh) == -1) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 
 	/* Q_S, server public key */
-	server_pubkey = packet_get_string(&slen);
-	if (slen != CURVE25519_SIZE)
-		fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
+	/* signed H */
+	if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+	if (pklen != CURVE25519_SIZE) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 
 #ifdef DEBUG_KEXECDH
 	dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
 #endif
 
-	/* signed H */
-	signature = packet_get_string(&slen);
-	packet_check_eom();
-
-	buffer_init(&shared_secret);
-	kexc25519_shared_key(client_key, server_pubkey, &shared_secret);
+	if ((shared_secret = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
+	    shared_secret)) < 0)
+		goto out;
 
 	/* calc and verify H */
-	kex_c25519_hash(
+	hashlen = sizeof(hash);
+	if ((r = kex_c25519_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->my), buffer_len(kex->my),
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 	    server_host_key_blob, sbloblen,
-	    client_pubkey,
+	    kex->c25519_client_pubkey,
 	    server_pubkey,
-	    buffer_ptr(&shared_secret), buffer_len(&shared_secret),
-	    &hash, &hashlen
-	);
-	free(server_host_key_blob);
-	free(server_pubkey);
-	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
-		fatal("key_verify failed for server_host_key");
-	key_free(server_host_key);
-	free(signature);
+	    sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
+	    hash, &hashlen)) < 0)
+		goto out;
+
+	if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
+	    ssh->compat)) != 0)
+		goto out;
 
 	/* save session id */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
-	kex_derive_keys(kex, hash, hashlen,
-	    buffer_ptr(&shared_secret), buffer_len(&shared_secret));
-	buffer_free(&shared_secret);
-	kex_finish(kex);
+
+	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+out:
+	explicit_bzero(hash, sizeof(hash));
+	explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
+	free(server_host_key_blob);
+	free(server_pubkey);
+	free(signature);
+	sshkey_free(server_host_key);
+	sshbuf_free(shared_secret);
+	return r;
 }
diff --git a/kexc25519s.c b/kexc25519s.c
index ba6f546f..912b0afb 100644
--- a/kexc25519s.c
+++ b/kexc25519s.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexc25519s.c,v 1.5 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexc25519s.c,v 1.6 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -30,97 +30,128 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "ssh2.h"
+#include "sshbuf.h"
+#include "ssherr.h"
 
-void
-kexc25519_server(Kex *kex)
+static int input_kex_c25519_init(int, u_int32_t, void *);
+
+int
+kexc25519_server(struct ssh *ssh)
+{
+	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_c25519_init);
+	return 0;
+}
+
+static int
+input_kex_c25519_init(int type, u_int32_t seq, void *ctxt)
 {
-	Key *server_host_private, *server_host_public;
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	struct sshkey *server_host_private, *server_host_public;
+	struct sshbuf *shared_secret = NULL;
 	u_char *server_host_key_blob = NULL, *signature = NULL;
 	u_char server_key[CURVE25519_SIZE];
 	u_char *client_pubkey = NULL;
 	u_char server_pubkey[CURVE25519_SIZE];
-	u_char *hash;
-	u_int slen, sbloblen, hashlen;
-	Buffer shared_secret;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t slen, pklen, sbloblen, hashlen;
+	int r;
 
 	/* generate private key */
 	kexc25519_keygen(server_key, server_pubkey);
 #ifdef DEBUG_KEXECDH
 	dump_digest("server private key:", server_key, sizeof(server_key));
 #endif
-
 	if (kex->load_host_public_key == NULL ||
-	    kex->load_host_private_key == NULL)
-		fatal("Cannot load hostkey");
-	server_host_public = kex->load_host_public_key(kex->hostkey_type);
-	if (server_host_public == NULL)
-		fatal("Unsupported hostkey type %d", kex->hostkey_type);
-	server_host_private = kex->load_host_private_key(kex->hostkey_type);
-
-	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
-	packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
-	client_pubkey = packet_get_string(&slen);
-	if (slen != CURVE25519_SIZE)
-		fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
-	packet_check_eom();
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    ssh)) == NULL ||
+	    (server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    ssh)) == NULL) {
+		r = SSH_ERR_NO_HOSTKEY_LOADED;
+		goto out;
+	}
 
+	if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+	if (pklen != CURVE25519_SIZE) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 #ifdef DEBUG_KEXECDH
 	dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
 #endif
 
-	buffer_init(&shared_secret);
-	kexc25519_shared_key(server_key, client_pubkey, &shared_secret);
+	if ((shared_secret = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = kexc25519_shared_key(server_key, client_pubkey,
+	    shared_secret)) < 0)
+		goto out;
 
 	/* calc H */
-	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
-	kex_c25519_hash(
+	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+	    &sbloblen)) != 0)
+		goto out;
+	hashlen = sizeof(hash);
+	if ((r = kex_c25519_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
-	    buffer_ptr(kex->my), buffer_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 	    server_host_key_blob, sbloblen,
 	    client_pubkey,
 	    server_pubkey,
-	    buffer_ptr(&shared_secret), buffer_len(&shared_secret),
-	    &hash, &hashlen
-	);
+	    sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
+	    hash, &hashlen)) < 0)
+		goto out;
 
 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
 	/* sign H */
-	kex->sign(server_host_private, server_host_public, &signature, &slen,
-	    hash, hashlen);
-
-	/* destroy_sensitive_data(); */
+	if ((r = kex->sign(server_host_private, server_host_public,
+	    &signature, &slen, hash, hashlen, ssh->compat)) < 0)
+		goto out;
 
 	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
-	packet_start(SSH2_MSG_KEX_ECDH_REPLY);
-	packet_put_string(server_host_key_blob, sbloblen);
-	packet_put_string(server_pubkey, sizeof(server_pubkey));
-	packet_put_string(signature, slen);
-	packet_send();
-
-	free(signature);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_pubkey, sizeof(server_pubkey))) != 0 ||
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+
+	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+out:
+	explicit_bzero(hash, sizeof(hash));
+	explicit_bzero(server_key, sizeof(server_key));
 	free(server_host_key_blob);
-	/* have keys, free server key */
+	free(signature);
 	free(client_pubkey);
-
-	kex_derive_keys(kex, hash, hashlen,
-	    buffer_ptr(&shared_secret), buffer_len(&shared_secret));
-	buffer_free(&shared_secret);
-	kex_finish(kex);
+	sshbuf_free(shared_secret);
+	return r;
 }
diff --git a/kexdh.c b/kexdh.c
index 2c1dfb6f..feea6697 100644
--- a/kexdh.c
+++ b/kexdh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexdh.c,v 1.24 2014/01/09 23:20:00 djm Exp $ */
+/* $OpenBSD: kexdh.c,v 1.25 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  *
@@ -33,58 +33,61 @@
 
 #include <openssl/evp.h>
 
-#include "buffer.h"
 #include "ssh2.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
 #include "kex.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 #include "digest.h"
-#include "log.h"
 
-void
+int
 kex_dh_hash(
-    char *client_version_string,
-    char *server_version_string,
-    char *ckexinit, int ckexinitlen,
-    char *skexinit, int skexinitlen,
-    u_char *serverhostkeyblob, int sbloblen,
-    BIGNUM *client_dh_pub,
-    BIGNUM *server_dh_pub,
-    BIGNUM *shared_secret,
-    u_char **hash, u_int *hashlen)
+    const char *client_version_string,
+    const char *server_version_string,
+    const u_char *ckexinit, size_t ckexinitlen,
+    const u_char *skexinit, size_t skexinitlen,
+    const u_char *serverhostkeyblob, size_t sbloblen,
+    const BIGNUM *client_dh_pub,
+    const BIGNUM *server_dh_pub,
+    const BIGNUM *shared_secret,
+    u_char *hash, size_t *hashlen)
 {
-	Buffer b;
-	static u_char digest[SSH_DIGEST_MAX_LENGTH];
-
-	buffer_init(&b);
-	buffer_put_cstring(&b, client_version_string);
-	buffer_put_cstring(&b, server_version_string);
-
-	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-	buffer_put_int(&b, ckexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, ckexinit, ckexinitlen);
-	buffer_put_int(&b, skexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, skexinit, skexinitlen);
-
-	buffer_put_string(&b, serverhostkeyblob, sbloblen);
-	buffer_put_bignum2(&b, client_dh_pub);
-	buffer_put_bignum2(&b, server_dh_pub);
-	buffer_put_bignum2(&b, shared_secret);
+	struct sshbuf *b;
+	int r;
 
+	if (*hashlen < ssh_digest_bytes(SSH_DIGEST_SHA1))
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((b = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_cstring(b, client_version_string)) != 0 ||
+	    (r = sshbuf_put_cstring(b, server_version_string)) != 0 ||
+	    /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	    (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
+	    (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
+	    (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, client_dh_pub)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, server_dh_pub)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, shared_secret)) != 0) {
+		sshbuf_free(b);
+		return r;
+	}
 #ifdef DEBUG_KEX
-	buffer_dump(&b);
+	sshbuf_dump(b, stderr);
 #endif
-	if (ssh_digest_buffer(SSH_DIGEST_SHA1, &b, digest, sizeof(digest)) != 0)
-		fatal("%s: ssh_digest_buffer failed", __func__);
-
-	buffer_free(&b);
-
+	if (ssh_digest_buffer(SSH_DIGEST_SHA1, b, hash, *hashlen) != 0) {
+		sshbuf_free(b);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	sshbuf_free(b);
+	*hashlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
 #ifdef DEBUG_KEX
-	dump_digest("hash", digest, ssh_digest_bytes(SSH_DIGEST_SHA1));
+	dump_digest("hash", hash, *hashlen);
 #endif
-	*hash = digest;
-	*hashlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
+	return 0;
 }
 #endif /* WITH_OPENSSL */
diff --git a/kexdhc.c b/kexdhc.c
index cd12df33..52b75229 100644
--- a/kexdhc.c
+++ b/kexdhc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexdhc.c,v 1.16 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexdhc.c,v 1.17 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  *
@@ -36,129 +36,175 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "dh.h"
 #include "ssh2.h"
+#include "dispatch.h"
+#include "compat.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 
-void
-kexdh_client(Kex *kex)
+static int input_kex_dh(int, u_int32_t, void *);
+
+int
+kexdh_client(struct ssh *ssh)
 {
-	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
-	DH *dh;
-	Key *server_host_key;
-	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *kbuf, *hash;
-	u_int klen, slen, sbloblen, hashlen;
-	int kout;
+	struct kex *kex = ssh->kex;
+	int r;
 
 	/* generate and send 'e', client DH public key */
 	switch (kex->kex_type) {
 	case KEX_DH_GRP1_SHA1:
-		dh = dh_new_group1();
+		kex->dh = dh_new_group1();
 		break;
 	case KEX_DH_GRP14_SHA1:
-		dh = dh_new_group14();
+		kex->dh = dh_new_group14();
 		break;
 	default:
-		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if (kex->dh == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
 	}
-	dh_gen_key(dh, kex->we_need * 8);
-	packet_start(SSH2_MSG_KEXDH_INIT);
-	packet_put_bignum2(dh->pub_key);
-	packet_send();
-
 	debug("sending SSH2_MSG_KEXDH_INIT");
+	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
+	    (r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 #ifdef DEBUG_KEXDH
-	DHparams_print_fp(stderr, dh);
+	DHparams_print_fp(stderr, kex->dh);
 	fprintf(stderr, "pub= ");
-	BN_print_fp(stderr, dh->pub_key);
+	BN_print_fp(stderr, kex->dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
-
 	debug("expecting SSH2_MSG_KEXDH_REPLY");
-	packet_read_expect(SSH2_MSG_KEXDH_REPLY);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
+	r = 0;
+ out:
+	return r;
+}
 
+static int
+input_kex_dh(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
+	struct sshkey *server_host_key = NULL;
+	u_char *kbuf = NULL, *server_host_key_blob = NULL, *signature = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t klen = 0, slen, sbloblen, hashlen;
+	int kout, r;
+
+	if (kex->verify_host_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
 	/* key, cert */
-	server_host_key_blob = packet_get_string(&sbloblen);
-	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
-	if (server_host_key == NULL)
-		fatal("cannot decode server_host_key_blob");
-	if (server_host_key->type != kex->hostkey_type)
-		fatal("type mismatch for decoded server_host_key_blob");
-	if (kex->verify_host_key == NULL)
-		fatal("cannot verify server_host_key");
-	if (kex->verify_host_key(server_host_key) == -1)
-		fatal("server_host_key verification failed");
-
+	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+	    &sbloblen)) != 0 ||
+	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
+	    &server_host_key)) != 0)
+		goto out;
+	if (server_host_key->type != kex->hostkey_type) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (kex->verify_host_key(server_host_key, ssh) == -1) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 	/* DH parameter f, server public DH key */
-	if ((dh_server_pub = BN_new()) == NULL)
-		fatal("dh_server_pub == NULL");
-	packet_get_bignum2(dh_server_pub);
-
+	if ((dh_server_pub = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	/* signed H */
+	if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "dh_server_pub= ");
 	BN_print_fp(stderr, dh_server_pub);
 	fprintf(stderr, "\n");
 	debug("bits %d", BN_num_bits(dh_server_pub));
 #endif
+	if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
+		sshpkt_disconnect(ssh, "bad server public DH value");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
-	/* signed H */
-	signature = packet_get_string(&slen);
-	packet_check_eom();
-
-	if (!dh_pub_is_valid(dh, dh_server_pub))
-		packet_disconnect("bad server public DH value");
-
-	klen = DH_size(dh);
-	kbuf = xmalloc(klen);
-	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
-		fatal("DH_compute_key: failed");
+	klen = DH_size(kex->dh);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
+	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("kexdh_client: BN_new failed");
-	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
-		fatal("kexdh_client: BN_bin2bn failed");
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
 
 	/* calc and verify H */
-	kex_dh_hash(
+	hashlen = sizeof(hash);
+	if ((r = kex_dh_hash(
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->my), buffer_len(kex->my),
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 	    server_host_key_blob, sbloblen,
-	    dh->pub_key,
+	    kex->dh->pub_key,
 	    dh_server_pub,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	free(server_host_key_blob);
-	BN_clear_free(dh_server_pub);
-	DH_free(dh);
+	    hash, &hashlen)) != 0)
+		goto out;
 
-	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
-		fatal("key_verify failed for server_host_key");
-	key_free(server_host_key);
-	free(signature);
+	if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
+	    ssh->compat)) != 0)
+		goto out;
 
 	/* save session id */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
-	kex_finish(kex);
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	DH_free(kex->dh);
+	kex->dh = NULL;
+	if (dh_server_pub)
+		BN_clear_free(dh_server_pub);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
+	sshkey_free(server_host_key);
+	free(server_host_key_blob);
+	free(signature);
+	return r;
 }
 #endif /* WITH_OPENSSL */
diff --git a/kexdhs.c b/kexdhs.c
index 34a215f8..182657ac 100644
--- a/kexdhs.c
+++ b/kexdhs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexdhs.c,v 1.19 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexdhs.c,v 1.20 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  *
@@ -35,55 +35,88 @@
 
 #include <openssl/dh.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "dh.h"
 #include "ssh2.h"
 
-void
-kexdh_server(Kex *kex)
+#include "dispatch.h"
+#include "compat.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+
+static int input_kex_dh_init(int, u_int32_t, void *);
+
+int
+kexdh_server(struct ssh *ssh)
 {
-	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
-	DH *dh;
-	Key *server_host_public, *server_host_private;
-	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
-	u_int sbloblen, klen, hashlen, slen;
-	int kout;
+	struct kex *kex = ssh->kex;
+	int r;
 
 	/* generate server DH public key */
 	switch (kex->kex_type) {
 	case KEX_DH_GRP1_SHA1:
-		dh = dh_new_group1();
+		kex->dh = dh_new_group1();
 		break;
 	case KEX_DH_GRP14_SHA1:
-		dh = dh_new_group14();
+		kex->dh = dh_new_group14();
 		break;
 	default:
-		fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
 	}
-	dh_gen_key(dh, kex->we_need * 8);
+	if (kex->dh == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
+		goto out;
 
 	debug("expecting SSH2_MSG_KEXDH_INIT");
-	packet_read_expect(SSH2_MSG_KEXDH_INIT);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_INIT, &input_kex_dh_init);
+	r = 0;
+ out:
+	return r;
+}
+
+int
+input_kex_dh_init(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
+	struct sshkey *server_host_public, *server_host_private;
+	u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t sbloblen, slen;
+	size_t klen = 0, hashlen;
+	int kout, r;
 
 	if (kex->load_host_public_key == NULL ||
-	    kex->load_host_private_key == NULL)
-		fatal("Cannot load hostkey");
-	server_host_public = kex->load_host_public_key(kex->hostkey_type);
-	if (server_host_public == NULL)
-		fatal("Unsupported hostkey type %d", kex->hostkey_type);
-	server_host_private = kex->load_host_private_key(kex->hostkey_type);
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    ssh)) == NULL ||
+	    (server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    ssh)) == NULL) {
+		r = SSH_ERR_NO_HOSTKEY_LOADED;
+		goto out;
+	}
 
 	/* key, cert */
-	if ((dh_client_pub = BN_new()) == NULL)
-		fatal("dh_client_pub == NULL");
-	packet_get_bignum2(dh_client_pub);
-	packet_check_eom();
+	if ((dh_client_pub = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "dh_client_pub= ");
@@ -93,71 +126,90 @@ kexdh_server(Kex *kex)
 #endif
 
 #ifdef DEBUG_KEXDH
-	DHparams_print_fp(stderr, dh);
+	DHparams_print_fp(stderr, kex->dh);
 	fprintf(stderr, "pub= ");
-	BN_print_fp(stderr, dh->pub_key);
+	BN_print_fp(stderr, kex->dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
-	if (!dh_pub_is_valid(dh, dh_client_pub))
-		packet_disconnect("bad client public DH value");
+	if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
+		sshpkt_disconnect(ssh, "bad client public DH value");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
-	klen = DH_size(dh);
-	kbuf = xmalloc(klen);
-	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
-		fatal("DH_compute_key: failed");
+	klen = DH_size(kex->dh);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
+	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("kexdh_server: BN_new failed");
-	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
-		fatal("kexdh_server: BN_bin2bn failed");
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
-
-	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
-
+	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+	    &sbloblen)) != 0)
+		goto out;
 	/* calc H */
-	kex_dh_hash(
+	hashlen = sizeof(hash);
+	if ((r = kex_dh_hash(
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
-	    buffer_ptr(kex->my), buffer_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 	    server_host_key_blob, sbloblen,
 	    dh_client_pub,
-	    dh->pub_key,
+	    kex->dh->pub_key,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	BN_clear_free(dh_client_pub);
+	    hash, &hashlen)) != 0)
+		goto out;
 
 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
 	/* sign H */
-	kex->sign(server_host_private, server_host_public, &signature, &slen,
-	    hash, hashlen);
+	if ((r = kex->sign(server_host_private, server_host_public,
+	    &signature, &slen, hash, hashlen, ssh->compat)) < 0)
+		goto out;
 
 	/* destroy_sensitive_data(); */
 
 	/* send server hostkey, DH pubkey 'f' and singed H */
-	packet_start(SSH2_MSG_KEXDH_REPLY);
-	packet_put_string(server_host_key_blob, sbloblen);
-	packet_put_bignum2(dh->pub_key);	/* f */
-	packet_put_string(signature, slen);
-	packet_send();
-
-	free(signature);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||	/* f */
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	DH_free(kex->dh);
+	kex->dh = NULL;
+	if (dh_client_pub)
+		BN_clear_free(dh_client_pub);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
 	free(server_host_key_blob);
-	/* have keys, free DH */
-	DH_free(dh);
-
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
-	kex_finish(kex);
+	free(signature);
+	return r;
 }
 #endif /* WITH_OPENSSL */
diff --git a/kexecdh.c b/kexecdh.c
index 3115d13d..2a4fec6b 100644
--- a/kexecdh.c
+++ b/kexecdh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexecdh.c,v 1.5 2014/01/09 23:20:00 djm Exp $ */
+/* $OpenBSD: kexecdh.c,v 1.6 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -38,60 +38,63 @@
 #include <openssl/ec.h>
 #include <openssl/ecdh.h>
 
-#include "buffer.h"
 #include "ssh2.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
 #include "kex.h"
-#include "log.h"
+#include "sshbuf.h"
 #include "digest.h"
+#include "ssherr.h"
 
-void
+int
 kex_ecdh_hash(
     int hash_alg,
     const EC_GROUP *ec_group,
-    char *client_version_string,
-    char *server_version_string,
-    char *ckexinit, int ckexinitlen,
-    char *skexinit, int skexinitlen,
-    u_char *serverhostkeyblob, int sbloblen,
+    const char *client_version_string,
+    const char *server_version_string,
+    const u_char *ckexinit, size_t ckexinitlen,
+    const u_char *skexinit, size_t skexinitlen,
+    const u_char *serverhostkeyblob, size_t sbloblen,
     const EC_POINT *client_dh_pub,
     const EC_POINT *server_dh_pub,
     const BIGNUM *shared_secret,
-    u_char **hash, u_int *hashlen)
+    u_char *hash, size_t *hashlen)
 {
-	Buffer b;
-	static u_char digest[SSH_DIGEST_MAX_LENGTH];
-
-	buffer_init(&b);
-	buffer_put_cstring(&b, client_version_string);
-	buffer_put_cstring(&b, server_version_string);
-
-	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-	buffer_put_int(&b, ckexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, ckexinit, ckexinitlen);
-	buffer_put_int(&b, skexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, skexinit, skexinitlen);
-
-	buffer_put_string(&b, serverhostkeyblob, sbloblen);
-	buffer_put_ecpoint(&b, ec_group, client_dh_pub);
-	buffer_put_ecpoint(&b, ec_group, server_dh_pub);
-	buffer_put_bignum2(&b, shared_secret);
+	struct sshbuf *b;
+	int r;
 
+	if (*hashlen < ssh_digest_bytes(hash_alg))
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((b = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_cstring(b, client_version_string)) != 0 ||
+	    (r = sshbuf_put_cstring(b, server_version_string)) != 0 ||
+	    /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	    (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
+	    (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
+	    (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
+	    (r = sshbuf_put_ec(b, client_dh_pub, ec_group)) != 0 ||
+	    (r = sshbuf_put_ec(b, server_dh_pub, ec_group)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, shared_secret)) != 0) {
+		sshbuf_free(b);
+		return r;
+	}
 #ifdef DEBUG_KEX
-	buffer_dump(&b);
+	sshbuf_dump(b, stderr);
 #endif
-	if (ssh_digest_buffer(hash_alg, &b, digest, sizeof(digest)) != 0)
-		fatal("%s: ssh_digest_buffer failed", __func__);
-
-	buffer_free(&b);
-
+	if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
+		sshbuf_free(b);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	sshbuf_free(b);
+	*hashlen = ssh_digest_bytes(hash_alg);
 #ifdef DEBUG_KEX
-	dump_digest("hash", digest, ssh_digest_bytes(hash_alg));
+	dump_digest("hash", hash, *hashlen);
 #endif
-	*hash = digest;
-	*hashlen = ssh_digest_bytes(hash_alg);
+	return 0;
 }
 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
diff --git a/kexecdhc.c b/kexecdhc.c
index df811c1c..3f362c5b 100644
--- a/kexecdhc.c
+++ b/kexecdhc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexecdhc.c,v 1.8 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexecdhc.c,v 1.9 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -34,126 +34,193 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include <openssl/ecdh.h>
+
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "dh.h"
 #include "ssh2.h"
+#include "dispatch.h"
+#include "compat.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 
-#include <openssl/ecdh.h>
+static int input_kex_ecdh_reply(int, u_int32_t, void *);
 
-void
-kexecdh_client(Kex *kex)
+int
+kexecdh_client(struct ssh *ssh)
 {
-	EC_KEY *client_key;
-	EC_POINT *server_public;
+	struct kex *kex = ssh->kex;
+	EC_KEY *client_key = NULL;
 	const EC_GROUP *group;
-	BIGNUM *shared_secret;
-	Key *server_host_key;
-	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *kbuf, *hash;
-	u_int klen, slen, sbloblen, hashlen;
+	const EC_POINT *public_key;
+	int r;
 
-	if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
-		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
-	if (EC_KEY_generate_key(client_key) != 1)
-		fatal("%s: EC_KEY_generate_key failed", __func__);
+	if ((client_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if (EC_KEY_generate_key(client_key) != 1) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	group = EC_KEY_get0_group(client_key);
+	public_key = EC_KEY_get0_public_key(client_key);
 
-	packet_start(SSH2_MSG_KEX_ECDH_INIT);
-	packet_put_ecpoint(group, EC_KEY_get0_public_key(client_key));
-	packet_send();
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
+	    (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 	debug("sending SSH2_MSG_KEX_ECDH_INIT");
 
 #ifdef DEBUG_KEXECDH
 	fputs("client private key:\n", stderr);
-	key_dump_ec_key(client_key);
+	sshkey_dump_ec_key(client_key);
 #endif
+	kex->ec_client_key = client_key;
+	kex->ec_group = group;
+	client_key = NULL;	/* owned by the kex */
 
 	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
-	packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply);
+	r = 0;
+ out:
+	if (client_key)
+		EC_KEY_free(client_key);
+	return r;
+}
+
+static int
+input_kex_ecdh_reply(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	const EC_GROUP *group;
+	EC_POINT *server_public = NULL;
+	EC_KEY *client_key;
+	BIGNUM *shared_secret = NULL;
+	struct sshkey *server_host_key = NULL;
+	u_char *server_host_key_blob = NULL, *signature = NULL;
+	u_char *kbuf = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t slen, sbloblen;
+	size_t klen = 0, hashlen;
+	int r;
+
+	if (kex->verify_host_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	group = kex->ec_group;
+	client_key = kex->ec_client_key;
 
 	/* hostkey */
-	server_host_key_blob = packet_get_string(&sbloblen);
-	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
-	if (server_host_key == NULL)
-		fatal("cannot decode server_host_key_blob");
-	if (server_host_key->type != kex->hostkey_type)
-		fatal("type mismatch for decoded server_host_key_blob");
-	if (kex->verify_host_key == NULL)
-		fatal("cannot verify server_host_key");
-	if (kex->verify_host_key(server_host_key) == -1)
-		fatal("server_host_key verification failed");
+	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+	    &sbloblen)) != 0 ||
+	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
+	    &server_host_key)) != 0)
+		goto out;
+	if (server_host_key->type != kex->hostkey_type) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (kex->verify_host_key(server_host_key, ssh) == -1) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 
 	/* Q_S, server public key */
-	if ((server_public = EC_POINT_new(group)) == NULL)
-		fatal("%s: EC_POINT_new failed", __func__);
-	packet_get_ecpoint(group, server_public);
-
-	if (key_ec_validate_public(group, server_public) != 0)
-		fatal("%s: invalid server public key", __func__);
+	/* signed H */
+	if ((server_public = EC_POINT_new(group)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXECDH
 	fputs("server public key:\n", stderr);
-	key_dump_ec_point(group, server_public);
+	sshkey_dump_ec_point(group, server_public);
 #endif
-
-	/* signed H */
-	signature = packet_get_string(&slen);
-	packet_check_eom();
+	if (sshkey_ec_validate_public(group, server_public) != 0) {
+		sshpkt_disconnect(ssh, "invalid server public key");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
 	klen = (EC_GROUP_get_degree(group) + 7) / 8;
-	kbuf = xmalloc(klen);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 	if (ECDH_compute_key(kbuf, klen, server_public,
-	    client_key, NULL) != (int)klen)
-		fatal("%s: ECDH_compute_key failed", __func__);
+	    client_key, NULL) != (int)klen ||
+	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 
 #ifdef DEBUG_KEXECDH
 	dump_digest("shared secret", kbuf, klen);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("%s: BN_new failed", __func__);
-	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
-		fatal("%s: BN_bin2bn failed", __func__);
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
-
 	/* calc and verify H */
-	kex_ecdh_hash(
+	hashlen = sizeof(hash);
+	if ((r = kex_ecdh_hash(
 	    kex->hash_alg,
 	    group,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->my), buffer_len(kex->my),
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 	    server_host_key_blob, sbloblen,
 	    EC_KEY_get0_public_key(client_key),
 	    server_public,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	free(server_host_key_blob);
-	EC_POINT_clear_free(server_public);
-	EC_KEY_free(client_key);
+	    hash, &hashlen)) != 0)
+		goto out;
 
-	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
-		fatal("key_verify failed for server_host_key");
-	key_free(server_host_key);
-	free(signature);
+	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
+	    hashlen, ssh->compat)) != 0)
+		goto out;
 
 	/* save session id */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
-	kex_finish(kex);
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	if (kex->ec_client_key) {
+		EC_KEY_free(kex->ec_client_key);
+		kex->ec_client_key = NULL;
+	}
+	if (server_public)
+		EC_POINT_clear_free(server_public);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
+	sshkey_free(server_host_key);
+	free(server_host_key_blob);
+	free(signature);
+	return r;
 }
 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
+
diff --git a/kexecdhs.c b/kexecdhs.c
index 6bfad04c..6b8d95d9 100644
--- a/kexecdhs.c
+++ b/kexecdhs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexecdhs.c,v 1.11 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexecdhs.c,v 1.12 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -32,124 +32,176 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include <openssl/ecdh.h>
+
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "ssh2.h"
 
-#include <openssl/ecdh.h>
+#include "dispatch.h"
+#include "compat.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+
+static int input_kex_ecdh_init(int, u_int32_t, void *);
+
+int
+kexecdh_server(struct ssh *ssh)
+{
+	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_ecdh_init);
+	return 0;
+}
 
-void
-kexecdh_server(Kex *kex)
+static int
+input_kex_ecdh_init(int type, u_int32_t seq, void *ctxt)
 {
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
 	EC_POINT *client_public;
-	EC_KEY *server_key;
+	EC_KEY *server_key = NULL;
 	const EC_GROUP *group;
-	BIGNUM *shared_secret;
-	Key *server_host_private, *server_host_public;
+	const EC_POINT *public_key;
+	BIGNUM *shared_secret = NULL;
+	struct sshkey *server_host_private, *server_host_public;
 	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *kbuf, *hash;
-	u_int klen, slen, sbloblen, hashlen;
-
-	if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL)
-		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
-	if (EC_KEY_generate_key(server_key) != 1)
-		fatal("%s: EC_KEY_generate_key failed", __func__);
+	u_char *kbuf = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t slen, sbloblen;
+	size_t klen = 0, hashlen;
+	int r;
+
+	if ((server_key = EC_KEY_new_by_curve_name(kex->ec_nid)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if (EC_KEY_generate_key(server_key) != 1) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	group = EC_KEY_get0_group(server_key);
 
 #ifdef DEBUG_KEXECDH
 	fputs("server private key:\n", stderr);
-	key_dump_ec_key(server_key);
+	sshkey_dump_ec_key(server_key);
 #endif
 
 	if (kex->load_host_public_key == NULL ||
-	    kex->load_host_private_key == NULL)
-		fatal("Cannot load hostkey");
-	server_host_public = kex->load_host_public_key(kex->hostkey_type);
-	if (server_host_public == NULL)
-		fatal("Unsupported hostkey type %d", kex->hostkey_type);
-	server_host_private = kex->load_host_private_key(kex->hostkey_type);
-
-	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
-	packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
-	if ((client_public = EC_POINT_new(group)) == NULL)
-		fatal("%s: EC_POINT_new failed", __func__);
-	packet_get_ecpoint(group, client_public);
-	packet_check_eom();
-
-	if (key_ec_validate_public(group, client_public) != 0)
-		fatal("%s: invalid client public key", __func__);
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    ssh)) == NULL ||
+	    (server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    ssh)) == NULL) {
+		r = SSH_ERR_NO_HOSTKEY_LOADED;
+		goto out;
+	}
+	if ((client_public = EC_POINT_new(group)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXECDH
 	fputs("client public key:\n", stderr);
-	key_dump_ec_point(group, client_public);
+	sshkey_dump_ec_point(group, client_public);
 #endif
+	if (sshkey_ec_validate_public(group, client_public) != 0) {
+		sshpkt_disconnect(ssh, "invalid client public key");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
 	/* Calculate shared_secret */
 	klen = (EC_GROUP_get_degree(group) + 7) / 8;
-	kbuf = xmalloc(klen);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 	if (ECDH_compute_key(kbuf, klen, client_public,
-	    server_key, NULL) != (int)klen)
-		fatal("%s: ECDH_compute_key failed", __func__);
+	    server_key, NULL) != (int)klen ||
+	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 
-#ifdef DEBUG_KEXDH
+#ifdef DEBUG_KEXECDH
 	dump_digest("shared secret", kbuf, klen);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("%s: BN_new failed", __func__);
-	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
-		fatal("%s: BN_bin2bn failed", __func__);
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
-
 	/* calc H */
-	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
-	kex_ecdh_hash(
+	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+	    &sbloblen)) != 0)
+		goto out;
+	hashlen = sizeof(hash);
+	if ((r = kex_ecdh_hash(
 	    kex->hash_alg,
 	    group,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
-	    buffer_ptr(kex->my), buffer_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 	    server_host_key_blob, sbloblen,
 	    client_public,
 	    EC_KEY_get0_public_key(server_key),
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	EC_POINT_clear_free(client_public);
+	    hash, &hashlen)) != 0)
+		goto out;
 
 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
 	/* sign H */
-	kex->sign(server_host_private, server_host_public, &signature, &slen,
-	    hash, hashlen);
+	if ((r = kex->sign(server_host_private, server_host_public,
+	    &signature, &slen, hash, hashlen, ssh->compat)) < 0)
+		goto out;
 
 	/* destroy_sensitive_data(); */
 
+	public_key = EC_KEY_get0_public_key(server_key);
 	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
-	packet_start(SSH2_MSG_KEX_ECDH_REPLY);
-	packet_put_string(server_host_key_blob, sbloblen);
-	packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
-	packet_put_string(signature, slen);
-	packet_send();
-
-	free(signature);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	if (kex->ec_client_key) {
+		EC_KEY_free(kex->ec_client_key);
+		kex->ec_client_key = NULL;
+	}
+	if (server_key)
+		EC_KEY_free(server_key);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
 	free(server_host_key_blob);
-	/* have keys, free server key */
-	EC_KEY_free(server_key);
-
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
-	kex_finish(kex);
+	free(signature);
+	return r;
 }
 #endif /* defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC) */
+
diff --git a/kexgex.c b/kexgex.c
index d1fa1a06..8b0d8333 100644
--- a/kexgex.c
+++ b/kexgex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgex.c,v 1.28 2014/01/09 23:20:00 djm Exp $ */
+/* $OpenBSD: kexgex.c,v 1.29 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -33,69 +33,70 @@
 #include <openssl/evp.h>
 #include <signal.h>
 
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
 #include "kex.h"
 #include "ssh2.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 #include "digest.h"
-#include "log.h"
 
-void
+int
 kexgex_hash(
     int hash_alg,
-    char *client_version_string,
-    char *server_version_string,
-    char *ckexinit, int ckexinitlen,
-    char *skexinit, int skexinitlen,
-    u_char *serverhostkeyblob, int sbloblen,
-    int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
-    BIGNUM *client_dh_pub,
-    BIGNUM *server_dh_pub,
-    BIGNUM *shared_secret,
-    u_char **hash, u_int *hashlen)
+    const char *client_version_string,
+    const char *server_version_string,
+    const u_char *ckexinit, size_t ckexinitlen,
+    const u_char *skexinit, size_t skexinitlen,
+    const u_char *serverhostkeyblob, size_t sbloblen,
+    int min, int wantbits, int max,
+    const BIGNUM *prime,
+    const BIGNUM *gen,
+    const BIGNUM *client_dh_pub,
+    const BIGNUM *server_dh_pub,
+    const BIGNUM *shared_secret,
+    u_char *hash, size_t *hashlen)
 {
-	Buffer b;
-	static u_char digest[SSH_DIGEST_MAX_LENGTH];
+	struct sshbuf *b;
+	int r;
 
-	buffer_init(&b);
-	buffer_put_cstring(&b, client_version_string);
-	buffer_put_cstring(&b, server_version_string);
-
-	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-	buffer_put_int(&b, ckexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, ckexinit, ckexinitlen);
-	buffer_put_int(&b, skexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, skexinit, skexinitlen);
-
-	buffer_put_string(&b, serverhostkeyblob, sbloblen);
-	if (min == -1 || max == -1)
-		buffer_put_int(&b, wantbits);
-	else {
-		buffer_put_int(&b, min);
-		buffer_put_int(&b, wantbits);
-		buffer_put_int(&b, max);
+	if (*hashlen < ssh_digest_bytes(SSH_DIGEST_SHA1))
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((b = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_cstring(b, client_version_string)) != 0 ||
+	    (r = sshbuf_put_cstring(b, server_version_string)) != 0 ||
+	    /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	    (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
+	    (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
+	    (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
+	    (min != -1 && (r = sshbuf_put_u32(b, min)) != 0) ||
+	    (r = sshbuf_put_u32(b, wantbits)) != 0 ||
+	    (max != -1 && (r = sshbuf_put_u32(b, max)) != 0) ||
+	    (r = sshbuf_put_bignum2(b, prime)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, gen)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, client_dh_pub)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, server_dh_pub)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, shared_secret)) != 0) {
+		sshbuf_free(b);
+		return r;
 	}
-	buffer_put_bignum2(&b, prime);
-	buffer_put_bignum2(&b, gen);
-	buffer_put_bignum2(&b, client_dh_pub);
-	buffer_put_bignum2(&b, server_dh_pub);
-	buffer_put_bignum2(&b, shared_secret);
-
 #ifdef DEBUG_KEXDH
-	buffer_dump(&b);
+	sshbuf_dump(b, stderr);
 #endif
-	if (ssh_digest_buffer(hash_alg, &b, digest, sizeof(digest)) != 0)
-		fatal("%s: ssh_digest_buffer failed", __func__);
-
-	buffer_free(&b);
-
-#ifdef DEBUG_KEX
-	dump_digest("hash", digest, ssh_digest_bytes(hash_alg));
-#endif
-	*hash = digest;
+	if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
+		sshbuf_free(b);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	sshbuf_free(b);
 	*hashlen = ssh_digest_bytes(hash_alg);
+#ifdef DEBUG_KEXDH
+	dump_digest("hash", hash, *hashlen);
+#endif
+	return 0;
 }
 #endif /* WITH_OPENSSL */
diff --git a/kexgexc.c b/kexgexc.c
index 18d09cfb..0898824f 100644
--- a/kexgexc.c
+++ b/kexgexc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexc.c,v 1.18 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexgexc.c,v 1.19 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -37,174 +37,237 @@
 #include <string.h>
 #include <signal.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
 #include "dh.h"
 #include "ssh2.h"
 #include "compat.h"
+#include "dispatch.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 
-void
-kexgex_client(Kex *kex)
+static int input_kex_dh_gex_group(int, u_int32_t, void *);
+static int input_kex_dh_gex_reply(int, u_int32_t, void *);
+
+int
+kexgex_client(struct ssh *ssh)
 {
-	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
-	BIGNUM *p = NULL, *g = NULL;
-	Key *server_host_key;
-	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
-	u_int klen, slen, sbloblen, hashlen;
-	int kout;
-	int min, max, nbits;
-	DH *dh;
+	struct kex *kex = ssh->kex;
+	int r;
+	u_int nbits;
 
 	nbits = dh_estimate(kex->dh_need * 8);
 
-	if (datafellows & SSH_OLD_DHGEX) {
+	kex->min = DH_GRP_MIN;
+	kex->max = DH_GRP_MAX;
+	kex->nbits = nbits;
+	if (ssh->compat & SSH_OLD_DHGEX) {
 		/* Old GEX request */
-		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
-		packet_put_int(nbits);
-		min = DH_GRP_MIN;
-		max = DH_GRP_MAX;
-
-		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
+		if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST_OLD))
+		    != 0 ||
+		    (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
+		    (r = sshpkt_send(ssh)) != 0)
+			goto out;
+		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", kex->nbits);
 	} else {
 		/* New GEX request */
-		min = DH_GRP_MIN;
-		max = DH_GRP_MAX;
-		packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
-		packet_put_int(min);
-		packet_put_int(nbits);
-		packet_put_int(max);
-
+		if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
+		    (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
+		    (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
+		    (r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
+		    (r = sshpkt_send(ssh)) != 0)
+			goto out;
 		debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
-		    min, nbits, max);
+		    kex->min, kex->nbits, kex->max);
 	}
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
-	    min, nbits, max);
+	    kex->min, kex->nbits, kex->max);
 #endif
-	packet_send();
-
-	debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
-	packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
+	    &input_kex_dh_gex_group);
+	r = 0;
+ out:
+	return r;
+}
 
-	if ((p = BN_new()) == NULL)
-		fatal("BN_new");
-	packet_get_bignum2(p);
-	if ((g = BN_new()) == NULL)
-		fatal("BN_new");
-	packet_get_bignum2(g);
-	packet_check_eom();
+static int
+input_kex_dh_gex_group(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	BIGNUM *p = NULL, *g = NULL;
+	int r, bits;
 
-	if (BN_num_bits(p) < min || BN_num_bits(p) > max)
-		fatal("DH_GEX group out of range: %d !< %d !< %d",
-		    min, BN_num_bits(p), max);
+	debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
 
-	dh = dh_new_group(g, p);
-	dh_gen_key(dh, kex->we_need * 8);
+	if ((p = BN_new()) == NULL ||
+	    (g = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
+	    (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+	if ((bits = BN_num_bits(p)) < 0 ||
+	    (u_int)bits < kex->min || (u_int)bits > kex->max) {
+		r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
+		goto out;
+	}
+	if ((kex->dh = dh_new_group(g, p)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	p = g = NULL; /* belong to kex->dh now */
 
+	/* generate and send 'e', client DH public key */
+	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
+	    (r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
 #ifdef DEBUG_KEXDH
-	DHparams_print_fp(stderr, dh);
+	DHparams_print_fp(stderr, kex->dh);
 	fprintf(stderr, "pub= ");
-	BN_print_fp(stderr, dh->pub_key);
+	BN_print_fp(stderr, kex->dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
+	r = 0;
+out:
+	if (p)
+		BN_clear_free(p);
+	if (g)
+		BN_clear_free(g);
+	return r;
+}
 
-	debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
-	/* generate and send 'e', client DH public key */
-	packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
-	packet_put_bignum2(dh->pub_key);
-	packet_send();
-
-	debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
-	packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
+static int
+input_kex_dh_gex_reply(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
+	struct sshkey *server_host_key = NULL;
+	u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t klen = 0, slen, sbloblen, hashlen;
+	int kout, r;
 
+	debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
+	if (kex->verify_host_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
 	/* key, cert */
-	server_host_key_blob = packet_get_string(&sbloblen);
-	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
-	if (server_host_key == NULL)
-		fatal("cannot decode server_host_key_blob");
-	if (server_host_key->type != kex->hostkey_type)
-		fatal("type mismatch for decoded server_host_key_blob");
-	if (kex->verify_host_key == NULL)
-		fatal("cannot verify server_host_key");
-	if (kex->verify_host_key(server_host_key) == -1)
-		fatal("server_host_key verification failed");
-
+	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+	    &sbloblen)) != 0 ||
+	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
+	    &server_host_key)) != 0)
+		goto out;
+	if (server_host_key->type != kex->hostkey_type) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (kex->verify_host_key(server_host_key, ssh) == -1) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 	/* DH parameter f, server public DH key */
-	if ((dh_server_pub = BN_new()) == NULL)
-		fatal("dh_server_pub == NULL");
-	packet_get_bignum2(dh_server_pub);
-
+	if ((dh_server_pub = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	/* signed H */
+	if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "dh_server_pub= ");
 	BN_print_fp(stderr, dh_server_pub);
 	fprintf(stderr, "\n");
 	debug("bits %d", BN_num_bits(dh_server_pub));
 #endif
+	if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
+		sshpkt_disconnect(ssh, "bad server public DH value");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
-	/* signed H */
-	signature = packet_get_string(&slen);
-	packet_check_eom();
-
-	if (!dh_pub_is_valid(dh, dh_server_pub))
-		packet_disconnect("bad server public DH value");
-
-	klen = DH_size(dh);
-	kbuf = xmalloc(klen);
-	if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
-		fatal("DH_compute_key: failed");
+	klen = DH_size(kex->dh);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
+	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("kexgex_client: BN_new failed");
-	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
-		fatal("kexgex_client: BN_bin2bn failed");
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
-
-	if (datafellows & SSH_OLD_DHGEX)
-		min = max = -1;
+	if (ssh->compat & SSH_OLD_DHGEX)
+		kex->min = kex->max = -1;
 
 	/* calc and verify H */
-	kexgex_hash(
+	hashlen = sizeof(hash);
+	if ((r = kexgex_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->my), buffer_len(kex->my),
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
 	    server_host_key_blob, sbloblen,
-	    min, nbits, max,
-	    dh->p, dh->g,
-	    dh->pub_key,
+	    kex->min, kex->nbits, kex->max,
+	    kex->dh->p, kex->dh->g,
+	    kex->dh->pub_key,
 	    dh_server_pub,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-
-	/* have keys, free DH */
-	DH_free(dh);
-	free(server_host_key_blob);
-	BN_clear_free(dh_server_pub);
+	    hash, &hashlen)) != 0)
+		goto out;
 
-	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
-		fatal("key_verify failed for server_host_key");
-	key_free(server_host_key);
-	free(signature);
+	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
+	    hashlen, ssh->compat)) != 0)
+		goto out;
 
 	/* save session id */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
 
-	kex_finish(kex);
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	DH_free(kex->dh);
+	kex->dh = NULL;
+	if (dh_server_pub)
+		BN_clear_free(dh_server_pub);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
+	sshkey_free(server_host_key);
+	free(server_host_key_blob);
+	free(signature);
+	return r;
 }
 #endif /* WITH_OPENSSL */
diff --git a/kexgexs.c b/kexgexs.c
index 1021e0bf..6e2b009b 100644
--- a/kexgexs.c
+++ b/kexgexs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexs.c,v 1.20 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: kexgexs.c,v 1.21 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -37,10 +37,9 @@
 
 #include <openssl/dh.h>
 
-#include "xmalloc.h"
-#include "buffer.h"
-#include "key.h"
+#include "sshkey.h"
 #include "cipher.h"
+#include "digest.h"
 #include "kex.h"
 #include "log.h"
 #include "packet.h"
@@ -51,33 +50,43 @@
 #include "ssh-gss.h"
 #endif
 #include "monitor_wrap.h"
+#include "dispatch.h"
+#include "ssherr.h"
+#include "sshbuf.h"
 
-void
-kexgex_server(Kex *kex)
+static int input_kex_dh_gex_request(int, u_int32_t, void *);
+static int input_kex_dh_gex_init(int, u_int32_t, void *);
+
+int
+kexgex_server(struct ssh *ssh)
 {
-	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
-	Key *server_host_public, *server_host_private;
-	DH *dh;
-	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
-	u_int sbloblen, klen, slen, hashlen;
-	int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
-	int type, kout;
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST_OLD,
+	    &input_kex_dh_gex_request);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
+	    &input_kex_dh_gex_request);
+	debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
+	return 0;
+}
+
+static int
+input_kex_dh_gex_request(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	int r;
+	u_int min = 0, max = 0, nbits = 0;
 
-	if (kex->load_host_public_key == NULL ||
-	    kex->load_host_private_key == NULL)
-		fatal("Cannot load hostkey");
-	server_host_public = kex->load_host_public_key(kex->hostkey_type);
-	if (server_host_public == NULL)
-		fatal("Unsupported hostkey type %d", kex->hostkey_type);
-	server_host_private = kex->load_host_private_key(kex->hostkey_type);
-
-	type = packet_read();
 	switch (type) {
 	case SSH2_MSG_KEX_DH_GEX_REQUEST:
 		debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
-		omin = min = packet_get_int();
-		onbits = nbits = packet_get_int();
-		omax = max = packet_get_int();
+		if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
+		    (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
+		    (r = sshpkt_get_u32(ssh, &max)) != 0 ||
+		    (r = sshpkt_get_end(ssh)) != 0)
+			goto out;
+		kex->nbits = nbits;
+		kex->min = min;
+		kex->max = max;
 		min = MAX(DH_GRP_MIN, min);
 		max = MIN(DH_GRP_MAX, max);
 		nbits = MAX(DH_GRP_MIN, nbits);
@@ -85,45 +94,88 @@ kexgex_server(Kex *kex)
 		break;
 	case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
 		debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
-		onbits = nbits = packet_get_int();
+		if ((r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
+		    (r = sshpkt_get_end(ssh)) != 0)
+			goto out;
+		kex->nbits = nbits;
 		/* unused for old GEX */
-		omin = min = DH_GRP_MIN;
-		omax = max = DH_GRP_MAX;
+		kex->min = min = DH_GRP_MIN;
+		kex->max = max = DH_GRP_MAX;
 		break;
 	default:
-		fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
 	}
-	packet_check_eom();
 
-	if (omax < omin || onbits < omin || omax < onbits)
-		fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
-		    omin, onbits, omax);
+	if (kex->max < kex->min || kex->nbits < kex->min ||
+	    kex->max < kex->nbits) {
+		r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
+		goto out;
+	}
 
 	/* Contact privileged parent */
-	dh = PRIVSEP(choose_dh(min, nbits, max));
-	if (dh == NULL)
-		packet_disconnect("Protocol error: no matching DH grp found");
-
+	kex->dh = PRIVSEP(choose_dh(min, nbits, max));
+	if (kex->dh == NULL) {
+		sshpkt_disconnect(ssh, "no matching DH grp found");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
-	packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
-	packet_put_bignum2(dh->p);
-	packet_put_bignum2(dh->g);
-	packet_send();
-
-	/* flush */
-	packet_write_wait();
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 
 	/* Compute our exchange value in parallel with the client */
-	dh_gen_key(dh, kex->we_need * 8);
+	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
+		goto out;
+
+	/* old KEX does not use min/max in kexgex_hash() */
+	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
+		kex->min = kex->max = -1;
 
 	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
-	packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
+	r = 0;
+ out:
+	return r;
+}
+
+static int
+input_kex_dh_gex_init(int type, u_int32_t seq, void *ctxt)
+{
+	struct ssh *ssh = ctxt;
+	struct kex *kex = ssh->kex;
+	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
+	struct sshkey *server_host_public, *server_host_private;
+	u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t sbloblen, slen;
+	size_t klen = 0, hashlen;
+	int kout, r;
+
+	if (kex->load_host_public_key == NULL ||
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    ssh)) == NULL ||
+	    (server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    ssh)) == NULL) {
+		r = SSH_ERR_NO_HOSTKEY_LOADED;
+		goto out;
+	}
 
 	/* key, cert */
-	if ((dh_client_pub = BN_new()) == NULL)
-		fatal("dh_client_pub == NULL");
-	packet_get_bignum2(dh_client_pub);
-	packet_check_eom();
+	if ((dh_client_pub = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXDH
 	fprintf(stderr, "dh_client_pub= ");
@@ -133,79 +185,92 @@ kexgex_server(Kex *kex)
 #endif
 
 #ifdef DEBUG_KEXDH
-	DHparams_print_fp(stderr, dh);
+	DHparams_print_fp(stderr, kex->dh);
 	fprintf(stderr, "pub= ");
-	BN_print_fp(stderr, dh->pub_key);
+	BN_print_fp(stderr, kex->dh->pub_key);
 	fprintf(stderr, "\n");
 #endif
-	if (!dh_pub_is_valid(dh, dh_client_pub))
-		packet_disconnect("bad client public DH value");
+	if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
+		sshpkt_disconnect(ssh, "bad client public DH value");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
-	klen = DH_size(dh);
-	kbuf = xmalloc(klen);
-	if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
-		fatal("DH_compute_key: failed");
+	klen = DH_size(kex->dh);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
+	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 #ifdef DEBUG_KEXDH
 	dump_digest("shared secret", kbuf, kout);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("kexgex_server: BN_new failed");
-	if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
-		fatal("kexgex_server: BN_bin2bn failed");
-	explicit_bzero(kbuf, klen);
-	free(kbuf);
-
-	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
-
-	if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
-		omin = min = omax = max = -1;
-
+	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+	    &sbloblen)) != 0)
+		goto out;
 	/* calc H */
-	kexgex_hash(
+	hashlen = sizeof(hash);
+	if ((r = kexgex_hash(
 	    kex->hash_alg,
 	    kex->client_version_string,
 	    kex->server_version_string,
-	    buffer_ptr(kex->peer), buffer_len(kex->peer),
-	    buffer_ptr(kex->my), buffer_len(kex->my),
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
 	    server_host_key_blob, sbloblen,
-	    omin, onbits, omax,
-	    dh->p, dh->g,
+	    kex->min, kex->nbits, kex->max,
+	    kex->dh->p, kex->dh->g,
 	    dh_client_pub,
-	    dh->pub_key,
+	    kex->dh->pub_key,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	BN_clear_free(dh_client_pub);
+	    hash, &hashlen)) != 0)
+		goto out;
 
 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
 	/* sign H */
-	kex->sign(server_host_private, server_host_public, &signature, &slen,
-	    hash, hashlen);
+	if ((r = kex->sign(server_host_private, server_host_public,
+	    &signature, &slen, hash, hashlen, ssh->compat)) < 0)
+		goto out;
 
 	/* destroy_sensitive_data(); */
 
 	/* send server hostkey, DH pubkey 'f' and singed H */
-	debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
-	packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
-	packet_put_string(server_host_key_blob, sbloblen);
-	packet_put_bignum2(dh->pub_key);	/* f */
-	packet_put_string(signature, slen);
-	packet_send();
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||     /* f */
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 
-	free(signature);
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	DH_free(kex->dh);
+	kex->dh = NULL;
+	if (dh_client_pub)
+		BN_clear_free(dh_client_pub);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
 	free(server_host_key_blob);
-	/* have keys, free DH */
-	DH_free(dh);
-
-	kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
-
-	kex_finish(kex);
+	free(signature);
+	return r;
 }
 #endif /* WITH_OPENSSL */
diff --git a/monitor.c b/monitor.c
index 6ee29112..40fff097 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.139 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: monitor.c,v 1.140 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -717,7 +717,7 @@ mm_answer_sign(int sock, Buffer *m)
 		    datafellows)) != 0)
 			fatal("%s: sshkey_sign failed: %s",
 			    __func__, ssh_err(r));
-	} else if ((key = get_hostkey_public_by_index(keyid)) != NULL &&
+	} else if ((key = get_hostkey_public_by_index(keyid, active_state)) != NULL &&
 	    auth_sock > 0) {
 		if ((r = ssh_agent_sign(auth_sock, key, &signature, &siglen,
 		    p, datlen, datafellows)) != 0) {
diff --git a/monitor_wrap.c b/monitor_wrap.c
index 84df481d..c0935dc6 100644
--- a/monitor_wrap.c
+++ b/monitor_wrap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.c,v 1.82 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: monitor_wrap.c,v 1.83 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -221,13 +221,13 @@ mm_choose_dh(int min, int nbits, int max)
 int
 mm_key_sign(Key *key, u_char **sigp, u_int *lenp, u_char *data, u_int datalen)
 {
-	Kex *kex = *pmonitor->m_pkex;
+	struct kex *kex = *pmonitor->m_pkex;
 	Buffer m;
 
 	debug3("%s entering", __func__);
 
 	buffer_init(&m);
-	buffer_put_int(&m, kex->host_key_index(key));
+	buffer_put_int(&m, kex->host_key_index(key, active_state));
 	buffer_put_string(&m, data, datalen);
 
 	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_SIGN, &m);
diff --git a/serverloop.c b/serverloop.c
index edf6a813..83a1e010 100644
--- a/serverloop.c
+++ b/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.174 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: serverloop.c,v 1.175 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -544,7 +544,7 @@ drain_output(void)
 static void
 process_buffered_input_packets(void)
 {
-	dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? active_state->kex : NULL);
+	dispatch_run(DISPATCH_NONBLOCK, NULL, active_state);
 }
 
 /*
@@ -874,7 +874,7 @@ server_loop2(Authctxt *authctxt)
 			if (packet_need_rekeying()) {
 				debug("need rekeying");
 				active_state->kex->done = 0;
-				kex_send_kexinit(active_state->kex);
+				kex_send_kexinit(active_state);
 			}
 		}
 		process_input(readset);
diff --git a/ssh-keyscan.c b/ssh-keyscan.c
index 84301b6f..223ac58f 100644
--- a/ssh-keyscan.c
+++ b/ssh-keyscan.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keyscan.c,v 1.93 2014/12/11 08:20:09 djm Exp $ */
+/* $OpenBSD: ssh-keyscan.c,v 1.94 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
  *
@@ -100,7 +100,7 @@ typedef struct Connection {
 	char *c_namelist;	/* Pointer to other possible addresses */
 	char *c_output_name;	/* Hostname of connection for output */
 	char *c_data;		/* Data read from this fd */
-	Kex *c_kex;		/* The key-exchange struct for ssh2 */
+	struct kex *c_kex;	/* The key-exchange struct for ssh2 */
 	struct timeval c_tv;	/* Time at which connection gets aborted */
 	TAILQ_ENTRY(Connection) c_link;	/* List of connections in timeout order. */
 } con;
@@ -221,7 +221,7 @@ keygrab_ssh1(con *c)
 #endif
 
 static int
-hostjump(Key *hostkey)
+hostjump(Key *hostkey, struct ssh *ssh)
 {
 	kexjmp_key = hostkey;
 	longjmp(kexjmp, 1);
@@ -247,7 +247,7 @@ static Key *
 keygrab_ssh2(con *c)
 {
 	char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
-	int j;
+	int r, j;
 
 	packet_set_connection(c->c_fd, c->c_fd);
 	enable_compat20();
@@ -256,7 +256,9 @@ keygrab_ssh2(con *c)
 	    (c->c_keytype == KT_RSA ? "ssh-rsa" :
 	    (c->c_keytype == KT_ED25519 ? "ssh-ed25519" :
 	    "ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521"));
-	c->c_kex = kex_setup(myproposal);
+	if ((r = kex_setup(active_state, myproposal)) < 0)
+		fatal("%s: kex_setup: %s", __func__, ssh_err(r));
+	c->c_kex = active_state->kex;
 #ifdef WITH_OPENSSL
 	c->c_kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 	c->c_kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
@@ -269,7 +271,7 @@ keygrab_ssh2(con *c)
 
 	if (!(j = setjmp(kexjmp))) {
 		nonfatal_fatal = 1;
-		dispatch_run(DISPATCH_BLOCK, &c->c_kex->done, c->c_kex);
+		dispatch_run(DISPATCH_BLOCK, &c->c_kex->done, active_state);
 		fprintf(stderr, "Impossible! dispatch_run() returned!\n");
 		exit(1);
 	}
diff --git a/sshconnect2.c b/sshconnect2.c
index e0d12999..e5802abc 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.218 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.219 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -92,7 +92,7 @@ char *xxx_host;
 struct sockaddr *xxx_hostaddr;
 
 static int
-verify_host_key_callback(Key *hostkey)
+verify_host_key_callback(Key *hostkey, struct ssh *ssh)
 {
 	if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
 		fatal("Host key verification failed.");
@@ -157,7 +157,7 @@ void
 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 {
 	char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
-	Kex *kex;
+	struct kex *kex;
 
 	xxx_host = host;
 	xxx_hostaddr = hostaddr;
@@ -204,8 +204,8 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 		    (time_t)options.rekey_interval);
 
 	/* start key exchange */
-	kex = kex_setup(myproposal);
-	active_state->kex = kex;
+	kex_setup(active_state, myproposal);
+	kex = active_state->kex;
 #ifdef WITH_OPENSSL
 	kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 	kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
@@ -218,7 +218,7 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 	kex->server_version_string=server_version_string;
 	kex->verify_host_key=&verify_host_key_callback;
 
-	dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
+	dispatch_run(DISPATCH_BLOCK, &kex->done, active_state);
 
 	if (options.use_roaming && !kex->roaming) {
 		debug("Roaming not allowed by server");
diff --git a/sshd.c b/sshd.c
index e4530398..21d8dd69 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.434 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: sshd.c,v 1.435 2015/01/19 20:16:15 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -836,7 +836,7 @@ list_hostkey_types(void)
 }
 
 static Key *
-get_hostkey_by_type(int type, int need_private)
+get_hostkey_by_type(int type, int need_private, struct ssh *ssh)
 {
 	int i;
 	Key *key;
@@ -865,15 +865,15 @@ get_hostkey_by_type(int type, int need_private)
 }
 
 Key *
-get_hostkey_public_by_type(int type)
+get_hostkey_public_by_type(int type, struct ssh *ssh)
 {
-	return get_hostkey_by_type(type, 0);
+	return get_hostkey_by_type(type, 0, ssh);
 }
 
 Key *
-get_hostkey_private_by_type(int type)
+get_hostkey_private_by_type(int type, struct ssh *ssh)
 {
-	return get_hostkey_by_type(type, 1);
+	return get_hostkey_by_type(type, 1, ssh);
 }
 
 Key *
@@ -885,7 +885,7 @@ get_hostkey_by_index(int ind)
 }
 
 Key *
-get_hostkey_public_by_index(int ind)
+get_hostkey_public_by_index(int ind, struct ssh *ssh)
 {
 	if (ind < 0 || ind >= options.num_host_key_files)
 		return (NULL);
@@ -893,7 +893,7 @@ get_hostkey_public_by_index(int ind)
 }
 
 int
-get_hostkey_index(Key *key)
+get_hostkey_index(Key *key, struct ssh *ssh)
 {
 	int i;
 
@@ -2432,29 +2432,30 @@ do_ssh1_kex(void)
 }
 #endif
 
-void
-sshd_hostkey_sign(Key *privkey, Key *pubkey, u_char **signature, u_int *slen,
-    u_char *data, u_int dlen)
+int
+sshd_hostkey_sign(Key *privkey, Key *pubkey, u_char **signature, size_t *slen,
+    u_char *data, size_t dlen, u_int flag)
 {
 	int r;
+	u_int xxx_slen, xxx_dlen = dlen;
 
 	if (privkey) {
-		if (PRIVSEP(key_sign(privkey, signature, slen, data, dlen) < 0))
+		if (PRIVSEP(key_sign(privkey, signature, &xxx_slen, data, xxx_dlen) < 0))
 			fatal("%s: key_sign failed", __func__);
+		if (slen)
+			*slen = xxx_slen;
 	} else if (use_privsep) {
-		if (mm_key_sign(pubkey, signature, slen, data, dlen) < 0)
+		if (mm_key_sign(pubkey, signature, &xxx_slen, data, xxx_dlen) < 0)
 			fatal("%s: pubkey_sign failed", __func__);
+		if (slen)
+			*slen = xxx_slen;
 	} else {
-		size_t xxx_slen;
-
-		if ((r = ssh_agent_sign(auth_sock, pubkey, signature, &xxx_slen,
+		if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slen,
 		    data, dlen, datafellows)) != 0)
 			fatal("%s: ssh_agent_sign failed: %s",
 			    __func__, ssh_err(r));
-		/* XXX: Old API is u_int; new size_t */
-		if (slen != NULL)
-			*slen = xxx_slen;
 	}
+	return 0;
 }
 
 /*
@@ -2464,7 +2465,7 @@ static void
 do_ssh2_kex(void)
 {
 	char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
-	Kex *kex;
+	struct kex *kex;
 
 	if (options.ciphers != NULL) {
 		myproposal[PROPOSAL_ENC_ALGS_CTOS] =
@@ -2500,8 +2501,8 @@ do_ssh2_kex(void)
 	    list_hostkey_types());
 
 	/* start key exchange */
-	kex = kex_setup(myproposal);
-	active_state->kex = kex;
+	kex_setup(active_state, myproposal);
+	kex = active_state->kex;
 #ifdef WITH_OPENSSL
 	kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
 	kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
@@ -2518,7 +2519,7 @@ do_ssh2_kex(void)
 	kex->host_key_index=&get_hostkey_index;
 	kex->sign = sshd_hostkey_sign;
 
-	dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
+	dispatch_run(DISPATCH_BLOCK, &kex->done, active_state);
 
 	session_id2 = kex->session_id;
 	session_id2_len = kex->session_id_len;