From: Bodo Möller <bodo@openssl.org>
Date: Thu, 25 May 2000 09:50:40 +0000 (+0000)
Subject: Implement SSL_OP_TLS_ROLLBACK_BUG for servers.
X-Git-Tag: OpenSSL_0_9_5~4
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=2c05c494c03a66c3e8e953f548d00f23b96e8b2d

Implement SSL_OP_TLS_ROLLBACK_BUG for servers.

Call dh_tmp_cb with correct 'is_export' flag.

Avoid tabs in CHANGES.
---

diff --git a/CHANGES b/CHANGES
index bc4f2218d6..4ae08b0e88 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,18 @@
 
  Changes between 0.9.5a and 0.9.6  [xx XXX 2000]
 
+  *) Implement SSL_OP_TLS_ROLLBACK_BUG: In ssl3_get_client_key_exchange, if
+     this option is set, tolerate broken clients that send the negotiated
+     protocol version number instead of the requested protocol version
+     number.
+     [Bodo Moeller]
+
+  *) Call dh_tmp_cb (set by ..._TMP_DH_CB) with correct 'is_export' flag;
+     i.e. non-zero for export ciphersuites, zero otherwise.
+     Previous versions had this flag inverted, inconsistent with
+     rsa_tmp_cb (..._TMP_RSA_CB).
+     [Bodo Moeller; problem reported by Amit Chopra]
+
   *) Add missing DSA library text string. Work around for some IIS
      key files with invalid SEQUENCE encoding.
      [Steve Henson]
@@ -19,7 +31,7 @@
      [Steve Henson]
 
   *) Eliminate non-ANSI declarations in crypto.h and stack.h.
-	 [Ulf Möller]
+     [Ulf Möller]
 
   *) Fix for SSL server purpose checking. Server checking was
      rejecting certificates which had extended key usage present
@@ -86,12 +98,12 @@
 
      The new configuration file reading functions are:
 
-	NCONF_new, NCONF_free, NCONF_load, NCONF_load_fp, NCONF_load_bio,
-	NCONF_get_section, NCONF_get_string, NCONF_get_numbre
+        NCONF_new, NCONF_free, NCONF_load, NCONF_load_fp, NCONF_load_bio,
+        NCONF_get_section, NCONF_get_string, NCONF_get_numbre
 
-	NCONF_default, NCONF_WIN32
+        NCONF_default, NCONF_WIN32
 
-	NCONF_dump_fp, NCONF_dump_bio
+        NCONF_dump_fp, NCONF_dump_bio
 
      NCONF_default and NCONF_WIN32 are method (or "class") choosers,
      NCONF_new creates a new CONF object.  This works in the same way
@@ -757,11 +769,11 @@
 
      With these changes, a new set of functions and macros have appeared:
 
-       CRYPTO_set_mem_debug_functions()		[F]
-       CRYPTO_get_mem_debug_functions()		[F]
-       CRYPTO_dbg_set_options()			[F]
-       CRYPTO_dbg_get_options()			[F]
-       CRYPTO_malloc_debug_init()		[M]
+       CRYPTO_set_mem_debug_functions()	        [F]
+       CRYPTO_get_mem_debug_functions()         [F]
+       CRYPTO_dbg_set_options()	                [F]
+       CRYPTO_dbg_get_options()                 [F]
+       CRYPTO_malloc_debug_init()               [M]
 
      The memory debug functions are NULL by default, unless the library
      is compiled with CRYPTO_MDEBUG or friends is defined.  If someone
diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c
index e23ca20bd3..64c1d80b8a 100644
--- a/ssl/s3_srvr.c
+++ b/ssl/s3_srvr.c
@@ -982,7 +982,7 @@ static int ssl3_send_server_key_exchange(SSL *s)
 			dhp=cert->dh_tmp;
 			if ((dhp == NULL) && (s->cert->dh_tmp_cb != NULL))
 				dhp=s->cert->dh_tmp_cb(s,
-				      !SSL_C_IS_EXPORT(s->s3->tmp.new_cipher),
+				      SSL_C_IS_EXPORT(s->s3->tmp.new_cipher),
 				      SSL_C_EXPORT_PKEYLENGTH(s->s3->tmp.new_cipher));
 			if (dhp == NULL)
 				{
@@ -1326,11 +1326,22 @@ static int ssl3_get_client_key_exchange(SSL *s)
 			goto f_err;
 			}
 
-		if ((p[0] != (s->client_version>>8)) || (p[1] != (s->client_version & 0xff)))
+		if (!((p[0] == (s->client_version>>8)) && (p[1] == (s->client_version & 0xff))))
 			{
-			al=SSL_AD_DECODE_ERROR;
-			SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
-			goto f_err;
+			/* The premaster secret must contain the same version number as the
+			 * ClientHello to detect version rollback attacks (strangely, the
+			 * protocol does not offer such protection for DH ciphersuites).
+			 * However, buggy clients exist that send the negotiated protocol
+			 * version instead if the servers does not support the requested
+			 * protocol version.
+			 * If SSL_OP_TLS_ROLLBACK_BUG is set, tolerate such clients. */
+			if (!((s->options & SSL_OP_TLS_ROLLBACK_BUG) &&
+				(p[0] == (s->version>>8)) && (p[1] == (s->version & 0xff))))
+				{
+				al=SSL_AD_DECODE_ERROR;
+				SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
+				goto f_err;
+				}
 			}
 
 		s->session->master_key_length=