upstream: make ssh->kex->session_id a sshbuf instead of u_char*/size_t

and use that instead of global variables containing copies of it. feedback/ok
markus@

OpenBSD-Commit-ID: a4b1b1ca4afd2e37cb9f64f737b30a6a7f96af68

auth2-gss.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-gss.c,v 1.30 2020/10/18 11:32:01 djm Exp $ */
+/* $OpenBSD: auth2-gss.c,v 1.31 2021/01/27 10:05:28 djm Exp $ */
 
 /*
  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
@@ -299,7 +299,7 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
 	mic.value = p;
 	mic.length = len;
 	ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
-	    "gssapi-with-mic");
+	    "gssapi-with-mic", ssh->kex->session_id);
 
 	if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
 		fatal_f("sshbuf_mutable_ptr failed");

auth2-hostbased.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-hostbased.c,v 1.45 2021/01/26 05:32:21 dtucker Exp $ */
+/* $OpenBSD: auth2-hostbased.c,v 1.46 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -35,6 +35,7 @@
 #include "xmalloc.h"
 #include "ssh2.h"
 #include "packet.h"
+#include "kex.h"
 #include "sshbuf.h"
 #include "log.h"
 #include "misc.h"
@@ -54,8 +55,6 @@
 
 /* import */
 extern ServerOptions options;
-extern u_char *session_id2;
-extern u_int session_id2_len;
 
 static int
 userauth_hostbased(struct ssh *ssh)
@@ -129,7 +128,7 @@ userauth_hostbased(struct ssh *ssh)
 	if ((b = sshbuf_new()) == NULL)
 		fatal_f("sshbuf_new failed");
 	/* reconstruct packet */
-	if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
+	if ((r = sshbuf_put_stringb(b, ssh->kex->session_id)) != 0 ||
 	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
 	    (r = sshbuf_put_cstring(b, authctxt->user)) != 0 ||
 	    (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||

auth2-pubkey.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.105 2021/01/26 00:49:30 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.106 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -47,6 +47,7 @@
 #include "ssh.h"
 #include "ssh2.h"
 #include "packet.h"
+#include "kex.h"
 #include "sshbuf.h"
 #include "log.h"
 #include "misc.h"
@@ -72,8 +73,6 @@
 
 /* import */
 extern ServerOptions options;
-extern u_char *session_id2;
-extern u_int session_id2_len;
 
 static char *
 format_key(const struct sshkey *key)
@@ -175,11 +174,11 @@ userauth_pubkey(struct ssh *ssh)
 		if ((b = sshbuf_new()) == NULL)
 			fatal_f("sshbuf_new failed");
 		if (ssh->compat & SSH_OLD_SESSIONID) {
-			if ((r = sshbuf_put(b, session_id2, session_id2_len)) != 0)
+			if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
 				fatal_fr(r, "put old session id");
 		} else {
-			if ((r = sshbuf_put_string(b, session_id2,
-			    session_id2_len)) != 0)
+			if ((r = sshbuf_put_stringb(b,
+			    ssh->kex->session_id)) != 0)
 				fatal_fr(r, "put session id");
 		}
 		if (!authctxt->valid || authctxt->user == NULL) {

auth2.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2.c,v 1.159 2020/10/18 11:32:01 djm Exp $ */
+/* $OpenBSD: auth2.c,v 1.160 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -61,8 +61,6 @@
 
 /* import */
 extern ServerOptions options;
-extern u_char *session_id2;
-extern u_int session_id2_len;
 extern struct sshbuf *loginmsg;
 
 /* methods */

clientloop.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.357 2021/01/27 09:26:54 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.358 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Author: Tatu Ylonen <[email protected]>
  * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
@@ -2125,9 +2125,6 @@ client_global_hostkeys_private_confirm(struct ssh *ssh, int type,
 
 	if ((signdata = sshbuf_new()) == NULL)
 		fatal_f("sshbuf_new failed");
-	/* Don't want to accidentally accept an unbound signature */
-	if (ssh->kex->session_id_len == 0)
-		fatal_f("ssh->kex->session_id_len == 0");
 	/*
 	 * Expect a signature for each of the ctx->nnew private keys we
 	 * haven't seen before. They will be in the same order as the
@@ -2140,8 +2137,8 @@ client_global_hostkeys_private_confirm(struct ssh *ssh, int type,
 		sshbuf_reset(signdata);
 		if ( (r = sshbuf_put_cstring(signdata,
 		    "[email protected]")) != 0 ||
-		    (r = sshbuf_put_string(signdata, ssh->kex->session_id,
-		    ssh->kex->session_id_len)) != 0 ||
+		    (r = sshbuf_put_stringb(signdata,
+		    ssh->kex->session_id)) != 0 ||
 		    (r = sshkey_puts(ctx->keys[i], signdata)) != 0)
 			fatal_fr(r, "compose signdata");
 		/* Extract and verify signature */

gss-genr.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: gss-genr.c,v 1.27 2020/10/18 11:32:01 djm Exp $ */
+/* $OpenBSD: gss-genr.c,v 1.28 2021/01/27 10:05:28 djm Exp $ */
 
 /*
  * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
@@ -44,9 +44,6 @@
 
 #include "ssh-gss.h"
 
-extern u_char *session_id2;
-extern u_int session_id2_len;
-
 /* sshbuf_get for gss_buffer_desc */
 int
 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
@@ -259,12 +256,12 @@ ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
 
 void
 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
-    const char *context)
+    const char *context, const struct sshbuf *session_id)
 {
 	int r;
 
 	sshbuf_reset(b);
-	if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
+	if ((r = sshbuf_put_stringb(b, session_id)) != 0 ||
 	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
 	    (r = sshbuf_put_cstring(b, user)) != 0 ||
 	    (r = sshbuf_put_cstring(b, service)) != 0 ||

kex.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.164 2021/01/27 09:26:54 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.165 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -637,7 +637,8 @@ kex_new(void)
 	    (kex->peer = sshbuf_new()) == NULL ||
 	    (kex->my = sshbuf_new()) == NULL ||
 	    (kex->client_version = sshbuf_new()) == NULL ||
-	    (kex->server_version = sshbuf_new()) == NULL) {
+	    (kex->server_version = sshbuf_new()) == NULL ||
+	    (kex->session_id = sshbuf_new()) == NULL) {
 		kex_free(kex);
 		return NULL;
 	}
@@ -697,7 +698,7 @@ kex_free(struct kex *kex)
 	sshbuf_free(kex->client_version);
 	sshbuf_free(kex->server_version);
 	sshbuf_free(kex->client_pub);
-	free(kex->session_id);
+	sshbuf_free(kex->session_id);
 	free(kex->failed_choice);
 	free(kex->hostkey_alg);
 	free(kex->name);
@@ -1015,8 +1016,7 @@ derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
 	    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 ||
+	    ssh_digest_update_buffer(hashctx, kex->session_id) != 0 ||
 	    ssh_digest_final(hashctx, digest, mdsz) != 0) {
 		r = SSH_ERR_LIBCRYPTO_ERROR;
 		error_f("KEX hash failed");
@@ -1067,12 +1067,14 @@ kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
 	int r;
 
 	/* save initial hash as session id */
-	if (kex->session_id == NULL) {
-		kex->session_id_len = hashlen;
-		kex->session_id = malloc(kex->session_id_len);
-		if (kex->session_id == NULL)
+	if ((kex->flags & KEX_INITIAL) != 0) {
+		if ((kex->session_id = sshbuf_new()) == NULL)
 			return SSH_ERR_ALLOC_FAIL;
-		memcpy(kex->session_id, hash, kex->session_id_len);
+		if ((r = sshbuf_put(kex->session_id, hash, hashlen)) != 0)
+			return r;
+	} else if (sshbuf_len(kex->session_id) == 0) {
+		error_f("no session ID in rekex");
+			return SSH_ERR_INTERNAL_ERROR;
 	}
 	for (i = 0; i < NKEYS; i++) {
 		if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen,

kex.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.112 2020/12/29 00:59:15 djm Exp $ */
+/* $OpenBSD: kex.h,v 1.113 2021/01/27 10:05:28 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -132,8 +132,6 @@ struct newkeys {
 struct ssh;
 
 struct kex {
-	u_char	*session_id;
-	size_t	session_id_len;
 	struct newkeys	*newkeys[MODE_MAX];
 	u_int	we_need;
 	u_int	dh_need;
@@ -149,6 +147,7 @@ struct kex {
 	struct sshbuf *peer;
 	struct sshbuf *client_version;
 	struct sshbuf *server_version;
+	struct sshbuf *session_id;
 	sig_atomic_t done;
 	u_int	flags;
 	int	hash_alg;

monitor.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.222 2021/01/27 09:26:54 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.223 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <[email protected]>
  * Copyright 2002 Markus Friedl <[email protected]>
@@ -104,7 +104,6 @@ static Gssctxt *gsscontext = NULL;
 /* Imports */
 extern ServerOptions options;
 extern u_int utmp_len;
-extern u_char session_id[];
 extern struct sshbuf *loginmsg;
 extern struct sshauthopt *auth_opts; /* XXX move to permanent ssh->authctxt? */
 
@@ -1431,7 +1430,9 @@ mm_answer_keyverify(struct ssh *ssh, int sock, struct sshbuf *m)
 		break;
 	}
 	if (!valid_data)
-		fatal_f("bad signature data blob");
+		fatal_f("bad %s signature data blob",
+		    key_blobtype == MM_USERKEY ? "userkey" :
+		    (key_blobtype == MM_HOSTKEY ? "hostkey" : "unknown"));
 
 	if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
 	    SSH_FP_DEFAULT)) == NULL)
@@ -1716,28 +1717,34 @@ monitor_apply_keystate(struct ssh *ssh, struct monitor *pmonitor)
 		fatal_fr(r, "packet_set_state");
 	sshbuf_free(child_state);
 	child_state = NULL;
-
-	if ((kex = ssh->kex) != NULL) {
-		/* XXX set callbacks */
+	if ((kex = ssh->kex) == NULL)
+		fatal_f("internal error: ssh->kex == NULL");
+	if (session_id2_len != sshbuf_len(ssh->kex->session_id)) {
+		fatal_f("incorrect session id length %zu (expected %u)",
+		    sshbuf_len(ssh->kex->session_id), session_id2_len);
+	}
+	if (memcmp(sshbuf_ptr(ssh->kex->session_id), session_id2,
+	    session_id2_len) != 0)
+		fatal_f("session ID mismatch");
+	/* XXX set callbacks */
 #ifdef WITH_OPENSSL
-		kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
-		kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
-		kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
-		kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
-		kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
-		kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
-		kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
+	kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
+	kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
+	kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
+	kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
+	kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
+	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
+	kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
 # ifdef OPENSSL_HAS_ECC
-		kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
+	kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
 # endif
 #endif /* WITH_OPENSSL */
-		kex->kex[KEX_C25519_SHA256] = kex_gen_server;
-		kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
-		kex->load_host_public_key=&get_hostkey_public_by_type;
-		kex->load_host_private_key=&get_hostkey_private_by_type;
-		kex->host_key_index=&get_hostkey_index;
-		kex->sign = sshd_hostkey_sign;
-	}
+	kex->kex[KEX_C25519_SHA256] = kex_gen_server;
+	kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
+	kex->load_host_public_key=&get_hostkey_public_by_type;
+	kex->load_host_private_key=&get_hostkey_private_by_type;
+	kex->host_key_index=&get_hostkey_index;
+	kex->sign = sshd_hostkey_sign;
 }
 
 /* This function requires careful sanity checking */

packet.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.298 2020/11/27 00:49:58 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.299 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Author: Tatu Ylonen <[email protected]>
  * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
@@ -2196,9 +2196,7 @@ kex_to_blob(struct sshbuf *m, struct kex *kex)
 {
 	int r;
 
-	if ((r = sshbuf_put_string(m, kex->session_id,
-	    kex->session_id_len)) != 0 ||
-	    (r = sshbuf_put_u32(m, kex->we_need)) != 0 ||
+	if ((r = sshbuf_put_u32(m, kex->we_need)) != 0 ||
 	    (r = sshbuf_put_cstring(m, kex->hostkey_alg)) != 0 ||
 	    (r = sshbuf_put_u32(m, kex->hostkey_type)) != 0 ||
 	    (r = sshbuf_put_u32(m, kex->hostkey_nid)) != 0 ||
@@ -2207,6 +2205,7 @@ kex_to_blob(struct sshbuf *m, struct kex *kex)
 	    (r = sshbuf_put_stringb(m, kex->peer)) != 0 ||
 	    (r = sshbuf_put_stringb(m, kex->client_version)) != 0 ||
 	    (r = sshbuf_put_stringb(m, kex->server_version)) != 0 ||
+	    (r = sshbuf_put_stringb(m, kex->session_id)) != 0 ||
 	    (r = sshbuf_put_u32(m, kex->flags)) != 0)
 		return r;
 	return 0;
@@ -2359,8 +2358,7 @@ kex_from_blob(struct sshbuf *m, struct kex **kexp)
 
 	if ((kex = kex_new()) == NULL)
 		return SSH_ERR_ALLOC_FAIL;
-	if ((r = sshbuf_get_string(m, &kex->session_id, &kex->session_id_len)) != 0 ||
-	    (r = sshbuf_get_u32(m, &kex->we_need)) != 0 ||
+	if ((r = sshbuf_get_u32(m, &kex->we_need)) != 0 ||
 	    (r = sshbuf_get_cstring(m, &kex->hostkey_alg, NULL)) != 0 ||
 	    (r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_type)) != 0 ||
 	    (r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_nid)) != 0 ||
@@ -2369,6 +2367,7 @@ kex_from_blob(struct sshbuf *m, struct kex **kexp)
 	    (r = sshbuf_get_stringb(m, kex->peer)) != 0 ||
 	    (r = sshbuf_get_stringb(m, kex->client_version)) != 0 ||
 	    (r = sshbuf_get_stringb(m, kex->server_version)) != 0 ||
+	    (r = sshbuf_get_stringb(m, kex->session_id)) != 0 ||
 	    (r = sshbuf_get_u32(m, &kex->flags)) != 0)
 		goto out;
 	kex->server = 1;

serverloop.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.224 2020/10/18 11:32:02 djm Exp $ */
+/* $OpenBSD: serverloop.c,v 1.225 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Author: Tatu Ylonen <[email protected]>
  * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
@@ -779,8 +779,8 @@ server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
 		    sshkey_type_plain(key->type) == KEY_RSA;
 		if ((r = sshbuf_put_cstring(sigbuf,
 		    "[email protected]")) != 0 ||
-		    (r = sshbuf_put_string(sigbuf,
-		    ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
+		    (r = sshbuf_put_stringb(sigbuf,
+		    ssh->kex->session_id)) != 0 ||
 		    (r = sshkey_puts(key, sigbuf)) != 0 ||
 		    (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
 		    sshbuf_ptr(sigbuf), sshbuf_len(sigbuf),

ssh-gss.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-gss.h,v 1.14 2018/07/10 09:13:30 djm Exp $ */
+/* $OpenBSD: ssh-gss.h,v 1.15 2021/01/27 10:05:28 djm Exp $ */
 /*
  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
  *
@@ -122,7 +122,7 @@ void ssh_gssapi_build_ctx(Gssctxt **);
 void ssh_gssapi_delete_ctx(Gssctxt **);
 OM_uint32 ssh_gssapi_sign(Gssctxt *, gss_buffer_t, gss_buffer_t);
 void ssh_gssapi_buildmic(struct sshbuf *, const char *,
-    const char *, const char *);
+    const char *, const char *, const struct sshbuf *);
 int ssh_gssapi_check_mechanism(Gssctxt **, gss_OID, const char *);
 
 /* In the server */