Modify client hello version when renegotiating to enhance interop with

[openssl.git] / ssl / s3_clnt.c

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index e7b477a5e723e9d1bf5776550fd40c374710920e..323a73277515be80f00f051aff8e97c998690ed5 100644 (file)
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -689,9 +689,43 @@ int ssl3_client_hello(SSL *s)
                /* Do the message type and length last */
                d=p= &(buf[4]);
 
+               /* version indicates the negotiated version: for example from
+                * an SSLv2/v3 compatible client hello). The client_version
+                * field is the maximum version we permit and it is also
+                * used in RSA encrypted premaster secrets. Some servers can
+                * choke if we initially report a higher version then
+                * renegotiate to a lower one in the premaster secret. This
+                * didn't happen with TLS 1.0 as most servers supported it
+                * but it can with TLS 1.1 or later if the server only supports
+                * 1.0.
+                *
+                * Possible scenario with previous logic:
+                *      1. Client hello indicates TLS 1.2
+                *      2. Server hello says TLS 1.0
+                *      3. RSA encrypted premaster secret uses 1.2.
+                *      4. Handhaked proceeds using TLS 1.0.
+                *      5. Server sends hello request to renegotiate.
+                *      6. Client hello indicates TLS v1.0 as we now
+                *         know that is maximum server supports.
+                *      7. Server chokes on RSA encrypted premaster secret
+                *         containing version 1.0.
+                *
+                * For interoperability it should be OK to always use the
+                * maximum version we support in client hello and then rely
+                * on the checking of version to ensure the servers isn't
+                * being inconsistent: for example initially negotiating with
+                * TLS 1.0 and renegotiating with TLS 1.2. We do this by using
+                * client_version in client hello and not resetting it to
+                * the negotiated version.
+                */
+#if 0
                *(p++)=s->version>>8;
                *(p++)=s->version&0xff;
                s->client_version=s->version;
+#else
+               *(p++)=s->client_version>>8;
+               *(p++)=s->client_version&0xff;
+#endif
 
                /* Random stuff */
                memcpy(p,s->s3->client_random,SSL3_RANDOM_SIZE);