From: Matt Caswell <matt@openssl.org>
Date: Wed, 12 Apr 2017 16:02:42 +0000 (+0100)
Subject: Don't fail the connection in SSLv3 if server selects ECDHE
X-Git-Tag: OpenSSL_1_1_0g~159
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=d717edf80ed3494a5a25c0b82ce61e5885de68ac;p=oweals%2Fopenssl.git

Don't fail the connection in SSLv3 if server selects ECDHE

ECDHE is not properly defined for SSLv3. Commit fe55c4a2 prevented ECDHE
from being selected in that protocol. However, historically, servers do
still select ECDHE anyway so that commit causes interoperability problems.
Clients that previously worked when talking to an SSLv3 server could now
fail.

This commit introduces an exception which enables a client to continue in
SSLv3 if the server selected ECDHE.

(cherry picked from commit 8af91fd9d08487e0dffb6ccac5f42633c964f3f0)

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3734)
---

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 9f9dce6c1e..f706c27982 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1944,7 +1944,7 @@ STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s)
     ssl_set_client_disabled(s);
     for (i = 0; i < sk_SSL_CIPHER_num(ciphers); i++) {
         const SSL_CIPHER *c = sk_SSL_CIPHER_value(ciphers, i);
-        if (!ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED)) {
+        if (!ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED, 0)) {
             if (!sk)
                 sk = sk_SSL_CIPHER_new_null();
             if (!sk)
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index eb7e8c9d2b..de4a520c2a 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -2070,7 +2070,7 @@ __owur size_t tls12_get_psigalgs(SSL *s, int sent, const unsigned char **psigs);
 __owur int tls12_check_peer_sigalg(const EVP_MD **pmd, SSL *s,
                                    const unsigned char *sig, EVP_PKEY *pkey);
 void ssl_set_client_disabled(SSL *s);
-__owur int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op);
+__owur int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op, int echde);
 
 __owur int ssl_add_clienthello_use_srtp_ext(SSL *s, unsigned char *p, int *len,
                                             int maxlen);
diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index a2a6684fa9..c4963f5767 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -1038,7 +1038,7 @@ MSG_PROCESS_RETURN tls_process_server_hello(SSL *s, PACKET *pkt)
      * If it is a disabled cipher we either didn't send it in client hello,
      * or it's not allowed for the selected protocol. So we return an error.
      */
-    if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_CHECK)) {
+    if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_CHECK, 1)) {
         al = SSL_AD_ILLEGAL_PARAMETER;
         SSLerr(SSL_F_TLS_PROCESS_SERVER_HELLO, SSL_R_WRONG_CIPHER_RETURNED);
         goto f_err;
@@ -2919,7 +2919,7 @@ int ssl_cipher_list_to_bytes(SSL *s, STACK_OF(SSL_CIPHER) *sk, unsigned char *p)
     for (i = 0; i < sk_SSL_CIPHER_num(sk); i++) {
         c = sk_SSL_CIPHER_value(sk, i);
         /* Skip disabled ciphers */
-        if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED))
+        if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED, 0))
             continue;
         j = s->method->put_cipher_by_char(c, p);
         p += j;
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 3f9702b9c2..377ed328b4 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -863,19 +863,31 @@ void ssl_set_client_disabled(SSL *s)
  * @s: SSL connection that you want to use the cipher on
  * @c: cipher to check
  * @op: Security check that you want to do
+ * @ecdhe: If set to 1 then TLSv1 ECDHE ciphers are also allowed in SSLv3
  *
  * Returns 1 when it's disabled, 0 when enabled.
  */
-int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op)
+int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op, int ecdhe)
 {
     if (c->algorithm_mkey & s->s3->tmp.mask_k
         || c->algorithm_auth & s->s3->tmp.mask_a)
         return 1;
     if (s->s3->tmp.max_ver == 0)
         return 1;
-    if (!SSL_IS_DTLS(s) && ((c->min_tls > s->s3->tmp.max_ver)
-                            || (c->max_tls < s->s3->tmp.min_ver)))
-        return 1;
+    if (!SSL_IS_DTLS(s)) {
+        int min_tls = c->min_tls;
+
+        /*
+         * For historical reasons we will allow ECHDE to be selected by a server
+         * in SSLv3 if we are a client
+         */
+        if (min_tls == TLS1_VERSION && ecdhe
+                && (c->algorithm_mkey & (SSL_kECDHE | SSL_kECDHEPSK)) != 0)
+            min_tls = SSL3_VERSION;
+
+        if ((min_tls > s->s3->tmp.max_ver) || (c->max_tls < s->s3->tmp.min_ver))
+            return 1;
+    }
     if (SSL_IS_DTLS(s) && (DTLS_VERSION_GT(c->min_dtls, s->s3->tmp.max_ver)
                            || DTLS_VERSION_LT(c->max_dtls, s->s3->tmp.min_ver)))
         return 1;