Fix SSL_get0_raw_cipherlist()

SSL_get0_raw_cipherlist() was a little too "raw" in the case of an SSLv2
compat ClientHello. In 1.0.2 and below, during version negotiation, if
we received an SSLv2 compat ClientHello but actually wanted to do SSLv3+
then we would construct a "fake" SSLv3+ ClientHello. This "fake" ClientHello
would have its ciphersuite list converted to the SSLv3+ format. It was
this "fake" raw list that got saved away to later be returned by a call to
SSL_get0_raw_cipherlist().

In 1.1.0+ version negotiation works differently and we process an SSLv2
compat ClientHello directly without the need for an intermediary "fake"
ClientHello. This meant that the raw ciphersuite list being saved was in
the SSLv2 format. Any caller of this function would not expect that and
potentially overread the returned buffer by one byte.

Fixes #2189
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2280)

ssl/statem/statem_srvr.c

@@ -3450,20 +3450,51 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,
         return NULL;
     }
 
-    if ((skp == NULL) || (*skp == NULL)) {
-        sk = sk_SSL_CIPHER_new_null(); /* change perhaps later */
-        if (sk == NULL) {
-            SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST, ERR_R_MALLOC_FAILURE);
-            *al = SSL_AD_INTERNAL_ERROR;
-            return NULL;
-        }
-    } else {
-        sk = *skp;
-        sk_SSL_CIPHER_zero(sk);
+    sk = sk_SSL_CIPHER_new_null();
+    if (sk == NULL) {
+        SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST, ERR_R_MALLOC_FAILURE);
+        *al = SSL_AD_INTERNAL_ERROR;
+        return NULL;
     }
 
-    if (!PACKET_memdup(cipher_suites, &s->s3->tmp.ciphers_raw,
-                       &s->s3->tmp.ciphers_rawlen)) {
+    if (sslv2format) {
+        size_t numciphers = PACKET_remaining(cipher_suites) / n;
+        PACKET sslv2ciphers = *cipher_suites;
+        unsigned int leadbyte;
+        unsigned char *raw;
+
+        /*
+         * We store the raw ciphers list in SSLv3+ format so we need to do some
+         * preprocessing to convert the list first. If there are any SSLv2 only
+         * ciphersuites with a non-zero leading byte then we are going to
+         * slightly over allocate because we won't store those. But that isn't a
+         * problem.
+         */
+        raw = s->s3->tmp.ciphers_raw = OPENSSL_malloc(numciphers * n);
+        if (raw == NULL) {
+            *al = SSL_AD_INTERNAL_ERROR;
+            goto err;
+        }
+        for (s->s3->tmp.ciphers_rawlen = 0;
+             PACKET_remaining(&sslv2ciphers) > 0;
+             raw += TLS_CIPHER_LEN) {
+            if (!PACKET_get_1(&sslv2ciphers, &leadbyte)
+                    || (leadbyte == 0
+                        && !PACKET_copy_bytes(&sslv2ciphers, raw,
+                                              TLS_CIPHER_LEN))
+                    || (leadbyte != 0
+                        && !PACKET_forward(&sslv2ciphers, TLS_CIPHER_LEN))) {
+                *al = SSL_AD_INTERNAL_ERROR;
+                OPENSSL_free(raw);
+                s->s3->tmp.ciphers_raw = NULL;
+                s->s3->tmp.ciphers_rawlen = 0;
+                goto err;
+            }
+            if (leadbyte == 0)
+                s->s3->tmp.ciphers_rawlen += TLS_CIPHER_LEN;
+        }
+    } else if (!PACKET_memdup(cipher_suites, &s->s3->tmp.ciphers_raw,
+                           &s->s3->tmp.ciphers_rawlen)) {
         *al = SSL_AD_INTERNAL_ERROR;
         goto err;
     }
@@ -3524,11 +3555,9 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,
         goto err;
     }
 
-    if (skp != NULL)
-        *skp = sk;
-    return (sk);
+    *skp = sk;
+    return sk;
  err:
-    if ((skp == NULL) || (*skp == NULL))
-        sk_SSL_CIPHER_free(sk);
+    sk_SSL_CIPHER_free(sk);
     return NULL;
 }