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F-5811: verify resumed cipher suite matches cached session

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On session-ID resumption the client only checked that the server's selected
suite was in its offered list, not that it equaled the resumed session's
suite, so a server could resume the session ID under a different cipher suite.
Per RFC 5246 Section 7.4.1.2 / F.1.4 a resumed session reuses its negotiated
suite; abort with a fatal illegal_parameter on mismatch.
This commit is contained in:
Juliusz Sosinowicz
2026-06-03 00:26:18 +02:00
parent b2c80eae15
commit a3a2609b18
1 changed files with 19 additions and 0 deletions
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src/internal.c
+19
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@@ -32279,6 +32279,25 @@ static void MakePSKPreMasterSecret(Arrays* arrays, byte use_psk_key)
WOLFSSL_ERROR_VERBOSE(EXT_MASTER_SECRET_NEEDED_E);
return EXT_MASTER_SECRET_NEEDED_E;
}
#ifndef NO_RESUME_SUITE_CHECK
/* RFC 5246 Section 7.4.1.3: on resumption the ServerHello
* reuses the previously negotiated cipher suite. Reject a
* server that resumes the session but selects a different
* suite. Skipped for ticket resumption (suite is bound in the
* ticket), consistent with the EMS check above. */
if (
#ifdef HAVE_SESSION_TICKET
ssl->session->ticketLen == 0 &&
#endif
(ssl->options.cipherSuite0 != ssl->session->cipherSuite0 ||
ssl->options.cipherSuite != ssl->session->cipherSuite)) {
WOLFSSL_MSG("Resumed session cipher suite does not match "
"ServerHello cipher suite");
SendAlert(ssl, alert_fatal, illegal_parameter);
WOLFSSL_ERROR_VERBOSE(MATCH_SUITE_ERROR);
return MATCH_SUITE_ERROR;
}
#endif /* NO_RESUME_SUITE_CHECK */
if (SetCipherSpecs(ssl) == 0) {
if (!HaveUniqueSessionObj(ssl)) {
WOLFSSL_MSG("Unable to have unique session object");