upstream commit

add experimental api for packet layer; ok djm@

5 files changed, 688 insertions, 9 deletions

diff --git a/Makefile.in b/Makefile.in
index 13256c2a..b494ac7c 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -65,6 +65,7 @@ MANFMT=@MANFMT@
 TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-pkcs11-helper$(EXEEXT) ssh-agent$(EXEEXT) scp$(EXEEXT) sftp-server$(EXEEXT) sftp$(EXEEXT)
 
 LIBOPENSSH_OBJS=\
+	ssh_api.o \
 	ssherr.o \
 	sshbuf.o \
 	sshkey.o \
@@ -75,20 +76,22 @@ LIBOPENSSH_OBJS=\
 	bitmap.o
 
 LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
-	authfd.o authfile.o bufaux.o bufbn.o buffer.o \
+	authfd.o authfile.o bufaux.o bufbn.o bufec.o buffer.o \
 	canohost.o channels.o cipher.o cipher-aes.o cipher-aesctr.o \
 	cipher-bf1.o cipher-ctr.o cipher-3des1.o cleanup.o \
 	compat.o crc32.o deattack.o fatal.o hostfile.o \
 	log.o match.o md-sha256.o moduli.o nchan.o packet.o opacket.o \
 	readpass.o rsa.o ttymodes.o xmalloc.o addrmatch.o \
-	atomicio.o key.o dispatch.o kex.o mac.o uidswap.o uuencode.o misc.o \
+	atomicio.o key.o dispatch.o mac.o uidswap.o uuencode.o misc.o \
 	monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-rsa.o dh.o \
-	kexdh.o kexgex.o kexdhc.o kexgexc.o bufec.o kexecdh.o kexecdhc.o \
 	msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
 	ssh-pkcs11.o smult_curve25519_ref.o \
-	kexc25519.o kexc25519c.o poly1305.o chacha.o cipher-chachapoly.o \
+	poly1305.o chacha.o cipher-chachapoly.o \
 	ssh-ed25519.o digest-openssl.o digest-libc.o hmac.o \
-	sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o blocks.o
+	sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o blocks.o \
+	kex.o kexdh.o kexgex.o kexecdh.o kexc25519.o \
+	kexdhc.o kexgexc.o kexecdhc.o kexc25519c.o \
+	kexdhs.o kexgexs.o kexecdhs.o kexc25519s.o
 
 SSHOBJS= ssh.o readconf.o clientloop.o sshtty.o \
 	sshconnect.o sshconnect1.o sshconnect2.o mux.o \
@@ -101,8 +104,7 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passwd.o auth-rsa.o auth-rh-rsa.o \
 	auth-chall.o auth2-chall.o groupaccess.o \
 	auth-skey.o auth-bsdauth.o auth2-hostbased.o auth2-kbdint.o \
 	auth2-none.o auth2-passwd.o auth2-pubkey.o \
-	monitor_mm.o monitor.o monitor_wrap.o kexdhs.o kexgexs.o kexecdhs.o \
-	kexc25519s.o auth-krb5.o \
+	monitor_mm.o monitor.o monitor_wrap.o auth-krb5.o \
 	auth2-gss.o gss-serv.o gss-serv-krb5.o \
 	loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \
 	sftp-server.o sftp-common.o \
diff --git a/packet.c b/packet.c
index 3306e4d6..cf9d3648 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.201 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: packet.c,v 1.202 2015/01/19 20:30:23 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -233,6 +233,8 @@ ssh_alloc_session_state(void)
 	    (state->incoming_packet = sshbuf_new()) == NULL)
 		goto fail;
 	TAILQ_INIT(&state->outgoing);
+	TAILQ_INIT(&ssh->private_keys);
+	TAILQ_INIT(&ssh->public_keys);
 	state->connection_in = -1;
 	state->connection_out = -1;
 	state->max_packet_size = 32768;
diff --git a/packet.h b/packet.h
index d9b56c30..069af2ea 100644
--- a/packet.h
+++ b/packet.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.h,v 1.63 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: packet.h,v 1.64 2015/01/19 20:30:23 markus Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -34,6 +34,11 @@ struct session_state;	/* private session data */
 
 #include "dispatch.h"	/* typedef, DISPATCH_MAX */
 
+struct key_entry {
+	TAILQ_ENTRY(key_entry) next;
+	struct sshkey *key;
+};
+
 struct ssh {
 	/* Session state */
 	struct session_state *state;
@@ -52,6 +57,13 @@ struct ssh {
 
 	/* datafellows */
 	int compat;
+
+	/* Lists for private and public keys */
+	TAILQ_HEAD(, key_entry) private_keys;
+	TAILQ_HEAD(, key_entry) public_keys;
+
+	/* APP data */
+	void *app_data;
 };
 
 struct ssh *ssh_alloc_session_state(void);
diff --git a/ssh_api.c b/ssh_api.c
new file mode 100644
index 00000000..1df995c9
--- /dev/null
+++ b/ssh_api.c
@@ -0,0 +1,527 @@
+/* $OpenBSD: ssh_api.c,v 1.1 2015/01/19 20:30:23 markus Exp $ */
+/*
+ * Copyright (c) 2012 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "includes.h"
+
+#include "ssh1.h" /* For SSH_MSG_NONE */
+#include "ssh_api.h"
+#include "compat.h"
+#include "log.h"
+#include "authfile.h"
+#include "sshkey.h"
+#include "misc.h"
+#include "ssh1.h"
+#include "ssh2.h"
+#include "version.h"
+#include "myproposal.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+
+#include <string.h>
+
+int	_ssh_exchange_banner(struct ssh *);
+int	_ssh_send_banner(struct ssh *, char **);
+int	_ssh_read_banner(struct ssh *, char **);
+int	_ssh_order_hostkeyalgs(struct ssh *);
+int	_ssh_verify_host_key(struct sshkey *, struct ssh *);
+struct sshkey *_ssh_host_public_key(int, struct ssh *);
+struct sshkey *_ssh_host_private_key(int, struct ssh *);
+int	_ssh_host_key_sign(struct sshkey *, struct sshkey *, u_char **,
+    size_t *, u_char *, size_t, u_int);
+
+/*
+ * stubs for the server side implementation of kex.
+ * disable privsep so our stubs will never be called.
+ */
+int	use_privsep = 0;
+int	mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
+    u_char *, u_int, u_int);
+DH	*mm_choose_dh(int, int, int);
+
+/* Define these two variables here so that they are part of the library */
+u_char *session_id2 = NULL;
+u_int session_id2_len = 0;
+
+int
+mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
+    u_char *data, u_int datalen, u_int compat)
+{
+	return (-1);
+}
+
+DH *
+mm_choose_dh(int min, int nbits, int max)
+{
+	return (NULL);
+}
+
+/* API */
+
+int
+ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
+{
+        char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
+	struct ssh *ssh;
+	char **proposal;
+	static int called;
+	int r;
+
+	if (!called) {
+		OpenSSL_add_all_algorithms();
+		called = 1;
+	}
+
+	ssh = ssh_packet_set_connection(NULL, -1, -1);
+	if (is_server)
+		ssh_packet_set_server(ssh);
+
+	/* Initialize key exchange */
+	proposal = kex_params ? kex_params->proposal : myproposal;
+	if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) {
+		ssh_free(ssh);
+		return r;
+	}
+	ssh->kex->server = is_server;
+	if (is_server) {
+#ifdef WITH_OPENSSL
+		ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
+		ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
+		ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
+		ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
+		ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
+#endif /* WITH_OPENSSL */
+		ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server;
+		ssh->kex->load_host_public_key=&_ssh_host_public_key;
+		ssh->kex->load_host_private_key=&_ssh_host_private_key;
+		ssh->kex->sign=&_ssh_host_key_sign;
+	} else {
+#ifdef WITH_OPENSSL
+		ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
+		ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
+		ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
+		ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
+		ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
+#endif /* WITH_OPENSSL */
+		ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client;
+		ssh->kex->verify_host_key =&_ssh_verify_host_key;
+	}
+	*sshp = ssh;
+	return 0;
+}
+
+void
+ssh_free(struct ssh *ssh)
+{
+	struct key_entry *k;
+
+	ssh_packet_close(ssh);
+	/*
+	 * we've only created the public keys variants in case we
+	 * are a acting as a server.
+	 */
+	while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
+		TAILQ_REMOVE(&ssh->public_keys, k, next);
+		if (ssh->kex && ssh->kex->server)
+			sshkey_free(k->key);
+		free(k);
+	}
+	while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
+		TAILQ_REMOVE(&ssh->private_keys, k, next);
+		free(k);
+	}
+	if (ssh->kex)
+		kex_free(ssh->kex);
+	free(ssh);
+}
+
+void
+ssh_set_app_data(struct ssh *ssh, void *app_data)
+{
+	ssh->app_data = app_data;
+}
+
+void *
+ssh_get_app_data(struct ssh *ssh)
+{
+	return ssh->app_data;
+}
+
+/* Returns < 0 on error, 0 otherwise */
+int
+ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
+{
+	struct sshkey *pubkey = NULL;
+	struct key_entry *k = NULL, *k_prv = NULL;
+	int r;
+
+	if (ssh->kex->server) {
+		if ((r = sshkey_from_private(key, &pubkey)) != 0)
+			return r;
+		if ((k = malloc(sizeof(*k))) == NULL ||
+		    (k_prv = malloc(sizeof(*k_prv))) == NULL) {
+			free(k);
+			sshkey_free(pubkey);
+			return SSH_ERR_ALLOC_FAIL;
+		}
+		k_prv->key = key;
+		TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
+
+		/* add the public key, too */
+		k->key = pubkey;
+		TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
+		r = 0;
+	} else {
+		if ((k = malloc(sizeof(*k))) == NULL)
+			return SSH_ERR_ALLOC_FAIL;
+		k->key = key;
+		TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
+		r = 0;
+	}
+
+	return r;
+}
+
+int
+ssh_set_verify_host_key_callback(struct ssh *ssh,
+    int (*cb)(struct sshkey *, struct ssh *))
+{
+	if (cb == NULL || ssh->kex == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+
+	ssh->kex->verify_host_key = cb;
+
+	return 0;
+}
+
+int
+ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
+{
+	return sshbuf_put(ssh_packet_get_input(ssh), data, len);
+}
+
+int
+ssh_packet_next(struct ssh *ssh, u_char *typep)
+{
+	int r;
+	u_int32_t seqnr;
+	u_char type;
+
+	/*
+	 * Try to read a packet. Return SSH_MSG_NONE if no packet or not
+	 * enough data.
+	 */
+	*typep = SSH_MSG_NONE;
+	if (ssh->kex->client_version_string == NULL ||
+	    ssh->kex->server_version_string == NULL)
+		return _ssh_exchange_banner(ssh);
+	/*
+	 * If we enough data and a dispatch function then
+	 * call the function and get the next packet.
+	 * Otherwise return the packet type to the caller so it
+	 * can decide how to go on.
+	 *
+	 * We will only call the dispatch function for:
+	 *     20-29    Algorithm negotiation
+	 *     30-49    Key exchange method specific (numbers can be reused for
+	 *              different authentication methods)
+	 */
+	for (;;) {
+		if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
+			return r;
+		if (type > 0 && type < DISPATCH_MAX &&
+		    type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
+		    ssh->dispatch[type] != NULL) {
+			if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
+				return r;
+		} else {
+			*typep = type;
+			return 0;
+		}
+	}
+}
+
+const u_char *
+ssh_packet_payload(struct ssh *ssh, size_t *lenp)
+{
+	return sshpkt_ptr(ssh, lenp);
+}
+
+int
+ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
+{
+	int r;
+
+	if ((r = sshpkt_start(ssh, type)) != 0 ||
+	    (r = sshpkt_put(ssh, data, len)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		return r;
+	return 0;
+}
+
+const u_char *
+ssh_output_ptr(struct ssh *ssh, size_t *len)
+{
+	struct sshbuf *output = ssh_packet_get_output(ssh);
+
+	*len = sshbuf_len(output);
+	return sshbuf_ptr(output);
+}
+
+int
+ssh_output_consume(struct ssh *ssh, size_t len)
+{
+	return sshbuf_consume(ssh_packet_get_output(ssh), len);
+}
+
+int
+ssh_output_space(struct ssh *ssh, size_t len)
+{
+	return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
+}
+
+int
+ssh_input_space(struct ssh *ssh, size_t len)
+{
+	return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
+}
+
+/* Read other side's version identification. */
+int
+_ssh_read_banner(struct ssh *ssh, char **bannerp)
+{
+	struct sshbuf *input;
+	const char *s;
+	char buf[256], remote_version[256];	/* must be same size! */
+	const char *mismatch = "Protocol mismatch.\r\n";
+	int r, remote_major, remote_minor;
+	size_t i, n, j, len;
+
+	*bannerp = NULL;
+	input = ssh_packet_get_input(ssh);
+	len = sshbuf_len(input);
+	s = (const char *)sshbuf_ptr(input);
+	for (j = n = 0;;) {
+		for (i = 0; i < sizeof(buf) - 1; i++) {
+			if (j >= len)
+				return (0);
+			buf[i] = s[j++];
+			if (buf[i] == '\r') {
+				buf[i] = '\n';
+				buf[i + 1] = 0;
+				continue;		/**XXX wait for \n */
+			}
+			if (buf[i] == '\n') {
+				buf[i + 1] = 0;
+				break;
+			}
+		}
+		buf[sizeof(buf) - 1] = 0;
+		if (strncmp(buf, "SSH-", 4) == 0)
+			break;
+		debug("ssh_exchange_identification: %s", buf);
+		if (ssh->kex->server || ++n > 65536) {
+			if ((r = sshbuf_put(ssh_packet_get_output(ssh),
+			   mismatch, strlen(mismatch))) != 0)
+				return r;
+			return SSH_ERR_NO_PROTOCOL_VERSION;
+		}
+	}
+	if ((r = sshbuf_consume(input, j)) != 0)
+		return r;
+
+	/*
+	 * Check that the versions match.  In future this might accept
+	 * several versions and set appropriate flags to handle them.
+	 */
+	if (sscanf(buf, "SSH-%d.%d-%[^\n]\n",
+	    &remote_major, &remote_minor, remote_version) != 3)
+		return SSH_ERR_INVALID_FORMAT;
+	debug("Remote protocol version %d.%d, remote software version %.100s",
+	    remote_major, remote_minor, remote_version);
+
+	ssh->compat = compat_datafellows(remote_version);
+	if  (remote_major == 1 && remote_minor == 99) {
+		remote_major = 2;
+		remote_minor = 0;
+	}
+	if (remote_major != 2)
+		return SSH_ERR_PROTOCOL_MISMATCH;
+	enable_compat20();
+	chop(buf);
+	debug("Remote version string %.100s", buf);
+	if ((*bannerp = strdup(buf)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	return 0;
+}
+
+/* Send our own protocol version identification. */
+int
+_ssh_send_banner(struct ssh *ssh, char **bannerp)
+{
+	char buf[256];
+	int r;
+
+	snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION);
+	if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0)
+		return r;
+	chop(buf);
+	debug("Local version string %.100s", buf);
+	if ((*bannerp = strdup(buf)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	return 0;
+}
+
+int
+_ssh_exchange_banner(struct ssh *ssh)
+{
+	struct kex *kex = ssh->kex;
+	int r;
+
+	/*
+	 * if _ssh_read_banner() cannot parse a full version string
+	 * it will return NULL and we end up calling it again.
+	 */
+
+	r = 0;
+	if (kex->server) {
+		if (kex->server_version_string == NULL)
+			r = _ssh_send_banner(ssh, &kex->server_version_string);
+		if (r == 0 &&
+		    kex->server_version_string != NULL &&
+		    kex->client_version_string == NULL)
+			r = _ssh_read_banner(ssh, &kex->client_version_string);
+	} else {
+		if (kex->server_version_string == NULL)
+			r = _ssh_read_banner(ssh, &kex->server_version_string);
+		if (r == 0 &&
+		    kex->server_version_string != NULL &&
+		    kex->client_version_string == NULL)
+			r = _ssh_send_banner(ssh, &kex->client_version_string);
+	}
+	if (r != 0)
+		return r;
+	/* start initial kex as soon as we have exchanged the banners */
+	if (kex->server_version_string != NULL &&
+	    kex->client_version_string != NULL) {
+		if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
+		    (r = kex_send_kexinit(ssh)) != 0)
+			return r;
+	}
+	return 0;
+}
+
+struct sshkey *
+_ssh_host_public_key(int type, struct ssh *ssh)
+{
+	struct key_entry *k;
+
+	debug3("%s: need %d", __func__, type);
+	TAILQ_FOREACH(k, &ssh->public_keys, next) {
+		debug3("%s: check %s", __func__, sshkey_type(k->key));
+		if (k->key->type == type)
+			return (k->key);
+	}
+	return (NULL);
+}
+
+struct sshkey *
+_ssh_host_private_key(int type, struct ssh *ssh)
+{
+	struct key_entry *k;
+
+	debug3("%s: need %d", __func__, type);
+	TAILQ_FOREACH(k, &ssh->private_keys, next) {
+		debug3("%s: check %s", __func__, sshkey_type(k->key));
+		if (k->key->type == type)
+			return (k->key);
+	}
+	return (NULL);
+}
+
+int
+_ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
+{
+	struct key_entry *k;
+
+	debug3("%s: need %s", __func__, sshkey_type(hostkey));
+	TAILQ_FOREACH(k, &ssh->public_keys, next) {
+		debug3("%s: check %s", __func__, sshkey_type(k->key));
+		if (sshkey_equal_public(hostkey, k->key))
+			return (0);	/* ok */
+	}
+	return (-1);	/* failed */
+}
+
+/* offer hostkey algorithms in kexinit depending on registered keys */
+int
+_ssh_order_hostkeyalgs(struct ssh *ssh)
+{
+	struct key_entry *k;
+	char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
+	char **proposal;
+	size_t maxlen;
+	int ktype, r;
+
+	/* XXX we de-serialize ssh->kex->my, modify it, and change it */
+	if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
+		return r;
+	orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
+	if ((oavail = avail = strdup(orig)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	maxlen = strlen(avail) + 1;
+	if ((replace = calloc(1, maxlen)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	*replace = '\0';
+	while ((alg = strsep(&avail, ",")) && *alg != '\0') {
+		if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
+			continue;
+		TAILQ_FOREACH(k, &ssh->public_keys, next) {
+			if (k->key->type == ktype ||
+			    (sshkey_is_cert(k->key) && k->key->type ==
+			    sshkey_type_plain(ktype))) {
+				if (*replace != '\0')
+					strlcat(replace, ",", maxlen);
+				strlcat(replace, alg, maxlen);
+				break;
+			}
+		}
+	}
+	if (*replace != '\0') {
+		debug2("%s: orig/%d    %s", __func__, ssh->kex->server, orig);
+		debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
+		free(orig);
+		proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
+		replace = NULL;	/* owned by proposal */
+		r = kex_prop2buf(ssh->kex->my, proposal);
+	}
+ out:
+	free(oavail);
+	free(replace);
+	kex_prop_free(proposal);
+	return r;
+}
+
+int
+_ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey,
+    u_char **signature, size_t *slen, u_char *data, size_t dlen, u_int compat)
+{
+	return sshkey_sign(privkey, signature, slen, data, dlen, compat);
+}
diff --git a/ssh_api.h b/ssh_api.h
new file mode 100644
index 00000000..a7e14e06
--- /dev/null
+++ b/ssh_api.h
@@ -0,0 +1,136 @@
+/* $OpenBSD: ssh_api.h,v 1.1 2015/01/19 20:30:23 markus Exp $ */
+/*
+ * Copyright (c) 2012 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef API_H
+#define API_H
+
+#include <sys/queue.h>
+#include <sys/types.h>
+#include <signal.h>
+
+#include "cipher.h"
+#include "sshkey.h"
+#include "kex.h"
+#include "ssh.h"
+#include "ssh2.h"
+#include "packet.h"
+
+struct kex_params {
+	char *proposal[PROPOSAL_MAX];
+};
+
+/* public SSH API functions */
+
+/*
+ * ssh_init() create a ssh connection object with given (optional)
+ * key exchange parameters.
+ */
+int	ssh_init(struct ssh **, int is_server, struct kex_params *kex_params);
+
+/*
+ * release ssh connection state.
+ */
+void	ssh_free(struct ssh *);
+
+/*
+ * attach application specific data to the connection state
+ */
+void	ssh_set_app_data(struct ssh *, void *);
+void	*ssh_get_app_data(struct ssh *);
+
+/*
+ * ssh_add_hostkey() registers a private/public hostkey for an ssh
+ * connection.
+ * ssh_add_hostkey() needs to be called before a key exchange is
+ * initiated with ssh_packet_next().
+ * private hostkeys are required if we need to act as a server.
+ * public hostkeys are used to verify the servers hostkey.
+ */
+int	ssh_add_hostkey(struct ssh *ssh, struct sshkey *key);
+
+/*
+ * ssh_set_verify_host_key_callback() registers a callback function
+ * which should be called instead of the default verification. The
+ * function given must return 0 if the hostkey is ok, -1 if the
+ * verification has failed.
+ */
+int	ssh_set_verify_host_key_callback(struct ssh *ssh,
+    int (*cb)(struct sshkey *, struct ssh *));
+
+/*
+ * ssh_packet_next() advances to the next input packet and returns
+ * the packet type in typep.
+ * ssh_packet_next() works by processing an input byte-stream,
+ * decrypting the received data and hiding the key-exchange from
+ * the caller.
+ * ssh_packet_next() sets typep if there is no new packet available.
+ * in this case the caller must fill the input byte-stream by passing
+ * the data received over network to ssh_input_append().
+ * additinally, the caller needs to send the resulting output
+ * byte-stream back over the network. otherwise the key exchange
+ * would not proceed. the output byte-stream is accessed through
+ * ssh_output_ptr().
+ */
+int	ssh_packet_next(struct ssh *ssh, u_char *typep);
+
+/*
+ * ssh_packet_payload() returns a pointer to the raw payload data of
+ * the current input packet and the length of this payload.
+ * the payload is accessible until ssh_packet_next() is called again.
+ */
+const u_char	*ssh_packet_payload(struct ssh *ssh, size_t *lenp);
+
+/*
+ * ssh_packet_put() creates an encrypted packet with the given type
+ * and payload.
+ * the encrypted packet is appended to the output byte-stream.
+ */
+int	ssh_packet_put(struct ssh *ssh, int type, const u_char *data,
+    size_t len);
+
+/*
+ * ssh_input_space() checks if 'len' bytes can be appended to the
+ * input byte-stream.
+ */
+int	ssh_input_space(struct ssh *ssh, size_t len);
+
+/*
+ * ssh_input_append() appends data to the input byte-stream.
+ */
+int	ssh_input_append(struct ssh *ssh, const u_char *data, size_t len);
+
+/*
+ * ssh_output_space() checks if 'len' bytes can be appended to the
+ * output byte-stream. XXX
+ */
+int	ssh_output_space(struct ssh *ssh, size_t len);
+
+/*
+ * ssh_output_ptr() retrieves both a pointer and the length of the
+ * current output byte-stream. the bytes need to be sent over the
+ * network. the number of bytes that have been successfully sent can
+ * be removed from the output byte-stream with ssh_output_consume().
+ */
+const u_char	*ssh_output_ptr(struct ssh *ssh, size_t *len);
+
+/*
+ * ssh_output_consume() removes the given number of bytes from
+ * the output byte-stream.
+ */
+int	ssh_output_consume(struct ssh *ssh, size_t len);
+
+#endif