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Modify client hello version when renegotiating to enhance interop with

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some servers.
This commit is contained in:
Dr. Stephen Henson 2012-02-09 15:41:44 +00:00
parent d06f047b04
commit fc6800d19f
2 changed files with 41 additions and 0 deletions
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7
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@ -4,6 +4,13 @@
Changes between 1.0.0f and 1.0.1 [xx XXX xxxx]
*) Some servers which support TLS 1.0 can choke if we initially indicate
support for TLS 1.2 and later renegotiate using TLS 1.0 in the RSA
encrypted premaster secret. As a workaround use the maximum pemitted
client version in client hello, this should keep such servers happy
and still work with previous versions of OpenSSL.
[Steve Henson]
*) Add support for TLS/DTLS heartbeats.
[Robin Seggelmann <seggelmann@fh-muenster.de>]

34
ssl/s3_clnt.c
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@ -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);