upstream: Refactor creation of KEX proposal.

This adds kex_proposal_populate_entries (and corresponding free) which
populates the KEX proposal array with dynamically allocated strings.
This replaces the previous mix of static and dynamic that has been the
source of previous leaks and bugs.  Remove unused compat functions.
With & ok djm@.

OpenBSD-Commit-ID: f2f99da4aae2233cb18bf9c749320c5e040a9c7b

1 files changed, 24 insertions, 41 deletions

diff --git a/sshconnect2.c b/sshconnect2.c
index 5b232e1b..03d00d33 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.363 2023/03/03 02:34:29 dtucker Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.364 2023/03/06 12:14:48 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -56,7 +56,6 @@
 #include "cipher.h"
 #include "sshkey.h"
 #include "kex.h"
-#include "myproposal.h"
 #include "sshconnect.h"
 #include "authfile.h"
 #include "dh.h"
@@ -221,24 +220,17 @@ void
 ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
     const struct ssh_conn_info *cinfo)
 {
-	char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
-	char *s, *all_key;
-	char *prop_kex = NULL, *prop_enc = NULL, *prop_hostkey = NULL;
-	int r, use_known_hosts_order = 0;
+	char *myproposal[PROPOSAL_MAX];
+	char *s, *all_key, *hkalgs = NULL;
+	int r;
 
 	xxx_host = host;
 	xxx_hostaddr = hostaddr;
 	xxx_conn_info = cinfo;
 
-	/*
-	 * If the user has not specified HostkeyAlgorithms, or has only
-	 * appended or removed algorithms from that list then prefer algorithms
-	 * that are in the list that are supported by known_hosts keys.
-	 */
-	if (options.hostkeyalgorithms == NULL ||
-	    options.hostkeyalgorithms[0] == '-' ||
-	    options.hostkeyalgorithms[0] == '+')
-		use_known_hosts_order = 1;
+	if (options.rekey_limit || options.rekey_interval)
+		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
+		    options.rekey_interval);
 
 	/* Expand or fill in HostkeyAlgorithms */
 	all_key = sshkey_alg_list(0, 0, 1, ',');
@@ -249,29 +241,22 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
 
 	if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
 		fatal_f("kex_names_cat");
-	myproposal[PROPOSAL_KEX_ALGS] = prop_kex = compat_kex_proposal(ssh, s);
-	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
-	    myproposal[PROPOSAL_ENC_ALGS_STOC] = prop_enc =
-	    compat_cipher_proposal(ssh, options.ciphers);
-	myproposal[PROPOSAL_COMP_ALGS_CTOS] =
-	    myproposal[PROPOSAL_COMP_ALGS_STOC] =
-	    (char *)compression_alg_list(options.compression);
-	myproposal[PROPOSAL_MAC_ALGS_CTOS] =
-	    myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
-	if (use_known_hosts_order) {
-		/* Query known_hosts and prefer algorithms that appear there */
-		myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
-		    compat_pkalg_proposal(ssh,
-		    order_hostkeyalgs(host, hostaddr, port, cinfo));
-	} else {
-		/* Use specified HostkeyAlgorithms exactly */
-		myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
-		    compat_pkalg_proposal(ssh, options.hostkeyalgorithms);
-	}
 
-	if (options.rekey_limit || options.rekey_interval)
-		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
-		    options.rekey_interval);
+	/*
+	 * If the user has not specified HostkeyAlgorithms, or has only
+	 * appended or removed algorithms from that list then prefer algorithms
+	 * that are in the list that are supported by known_hosts keys.
+	 */
+	if (options.hostkeyalgorithms == NULL ||
+	    options.hostkeyalgorithms[0] == '-' ||
+	    options.hostkeyalgorithms[0] == '+')
+		hkalgs = order_hostkeyalgs(host, hostaddr, port, cinfo);
+
+	kex_proposal_populate_entries(ssh, myproposal, s, options.ciphers,
+	    options.macs, compression_alg_list(options.compression),
+	    hkalgs ? hkalgs : options.hostkeyalgorithms);
+
+	free(hkalgs);
 
 	/* start key exchange */
 	if ((r = kex_setup(ssh, myproposal)) != 0)
@@ -295,6 +280,7 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &ssh->kex->done);
 
 	/* remove ext-info from the KEX proposals for rekeying */
+	free(myproposal[PROPOSAL_KEX_ALGS]);
 	myproposal[PROPOSAL_KEX_ALGS] =
 	    compat_kex_proposal(ssh, options.kex_algorithms);
 	if ((r = kex_prop2buf(ssh->kex->my, myproposal)) != 0)
@@ -308,10 +294,7 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
 	    (r = ssh_packet_write_wait(ssh)) != 0)
 		fatal_fr(r, "send packet");
 #endif
-	/* Free only parts of proposal that were dynamically allocated here. */
-	free(prop_kex);
-	free(prop_enc);
-	free(prop_hostkey);
+	kex_proposal_free_entries(myproposal);
 }
 
 /*