From: dtucker <dtucker@openbsd.org>
Date: Fri, 1 Jul 2022 03:39:44 +0000 (+0000)
Subject: Don't leak the strings allocated by order_hostkeyalgs() and
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=0c7793e63650862296905b8935667fb89b91184c;p=openbsd

Don't leak the strings allocated by order_hostkeyalgs() and
list_hostkey_types() that are passed to compat_pkalg_proposal().
Part of github PR#324 from ZoltanFridrich, ok djm@

This is a roll-forward of the previous rollback now that the required
changes in compat.c have been done.
---

diff --git a/usr.bin/ssh/sshconnect2.c b/usr.bin/ssh/sshconnect2.c
index cd0a4e8de5b..67f8e0309cf 100644
--- a/usr.bin/ssh/sshconnect2.c
+++ b/usr.bin/ssh/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.358 2022/06/24 10:45:06 dtucker Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.359 2022/07/01 03:39:44 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -213,6 +213,7 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
 {
 	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;
 
 	xxx_host = host;
@@ -238,10 +239,9 @@ 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] = compat_kex_proposal(ssh, s);
+	myproposal[PROPOSAL_KEX_ALGS] = prop_kex = compat_kex_proposal(ssh, s);
 	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
-	    compat_cipher_proposal(ssh, options.ciphers);
-	myproposal[PROPOSAL_ENC_ALGS_STOC] =
+	    myproposal[PROPOSAL_ENC_ALGS_STOC] = prop_enc =
 	    compat_cipher_proposal(ssh, options.ciphers);
 	myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 	    myproposal[PROPOSAL_COMP_ALGS_STOC] =
@@ -250,12 +250,12 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
 	    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] =
+		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] =
+		myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
 		    compat_pkalg_proposal(ssh, options.hostkeyalgorithms);
 	}
 
@@ -296,6 +296,10 @@ 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);
 }
 
 /*
diff --git a/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c
index 16a5e4ff8c1..dc450911ba7 100644
--- a/usr.bin/ssh/sshd.c
+++ b/usr.bin/ssh/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.588 2022/06/24 10:45:06 dtucker Exp $ */
+/* $OpenBSD: sshd.c,v 1.589 2022/07/01 03:39:44 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2195,12 +2195,14 @@ do_ssh2_kex(struct ssh *ssh)
 {
 	char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
 	struct kex *kex;
+	char *prop_kex = NULL, *prop_enc = NULL, *prop_hostkey = NULL;
 	int r;
 
-	myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(ssh,
+	myproposal[PROPOSAL_KEX_ALGS] = prop_kex = compat_kex_proposal(ssh,
 	    options.kex_algorithms);
-	myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal(ssh,
-	    options.ciphers);
+	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
+	    myproposal[PROPOSAL_ENC_ALGS_STOC] = prop_enc =
+	    compat_cipher_proposal(ssh, options.ciphers);
 	myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal(ssh,
 	    options.ciphers);
 	myproposal[PROPOSAL_MAC_ALGS_CTOS] =
@@ -2215,8 +2217,8 @@ do_ssh2_kex(struct ssh *ssh)
 		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
 		    options.rekey_interval);
 
-	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal(
-	    ssh, list_hostkey_types());
+	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
+	   compat_pkalg_proposal(ssh, list_hostkey_types());
 
 	/* start key exchange */
 	if ((r = kex_setup(ssh, myproposal)) != 0)
@@ -2249,6 +2251,9 @@ do_ssh2_kex(struct ssh *ssh)
 	    (r = ssh_packet_write_wait(ssh)) != 0)
 		fatal_fr(r, "send test");
 #endif
+	free(prop_kex);
+	free(prop_enc);
+	free(prop_hostkey);
 	debug("KEX done");
 }