File gnutls-CVE-2020-24659.patch of Package gnutls.18748
commit 521e6492b9bbc8ec1519924526942cf2fc719497
Author: Daiki Ueno <ueno@gnu.org>
Date: Sat Aug 22 17:19:39 2020 +0200
handshake: reject no_renegotiation alert if handshake is incomplete
If the initial handshake is incomplete and the server sends a
no_renegotiation alert, the client should treat it as a fatal error
even if its level is warning. Otherwise the same handshake
state (e.g., DHE parameters) are reused in the next gnutls_handshake
call, if it is called in the loop idiom:
do {
ret = gnutls_handshake(session);
} while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
Signed-off-by: Daiki Ueno <ueno@gnu.org>
Index: gnutls-3.6.7/lib/gnutls_int.h
===================================================================
--- gnutls-3.6.7.orig/lib/gnutls_int.h 2020-09-14 14:48:26.817591531 +0200
+++ gnutls-3.6.7/lib/gnutls_int.h 2020-09-14 14:48:59.497822903 +0200
@@ -1360,6 +1360,7 @@ typedef struct {
#define HSK_RECORD_SIZE_LIMIT_NEGOTIATED (1<<24)
#define HSK_RECORD_SIZE_LIMIT_SENT (1<<25) /* record_size_limit extension was sent */
#define HSK_RECORD_SIZE_LIMIT_RECEIVED (1<<26) /* server: record_size_limit extension was seen but not accepted yet */
+#define HSK_SERVER_HELLO_RECEIVED (1<<29) /* client: Server Hello message has been received */
/* The hsk_flags are for use within the ongoing handshake;
* they are reset to zero prior to handshake start by gnutls_handshake. */
Index: gnutls-3.6.7/lib/handshake.c
===================================================================
--- gnutls-3.6.7.orig/lib/handshake.c 2020-09-14 14:48:25.789584252 +0200
+++ gnutls-3.6.7/lib/handshake.c 2020-09-14 14:50:23.626418528 +0200
@@ -2038,6 +2038,8 @@ read_server_hello(gnutls_session_t sessi
goto cleanup;
}
+ session->internals.hsk_flags |= HSK_SERVER_HELLO_RECEIVED;
+
cleanup:
return ret;
@@ -2636,16 +2638,42 @@ int gnutls_rehandshake(gnutls_session_t
return 0;
}
+/* This function checks whether the error code should be treated fatal
+ * or not, and also does the necessary state transition. In
+ * particular, in the case of a rehandshake abort it resets the
+ * handshake's internal state.
+ */
inline static int
_gnutls_abort_handshake(gnutls_session_t session, int ret)
{
- if (((ret == GNUTLS_E_WARNING_ALERT_RECEIVED) &&
- (gnutls_alert_get(session) == GNUTLS_A_NO_RENEGOTIATION))
- || ret == GNUTLS_E_GOT_APPLICATION_DATA)
- return 0;
+ switch (ret) {
+ case GNUTLS_E_WARNING_ALERT_RECEIVED:
+ if (gnutls_alert_get(session) == GNUTLS_A_NO_RENEGOTIATION) {
+ /* The server always toleretes a "no_renegotiation" alert. */
+ if (session->security_parameters.entity == GNUTLS_SERVER) {
+ STATE = STATE0;
+ return ret;
+ }
- /* this doesn't matter */
- return GNUTLS_E_INTERNAL_ERROR;
+ /* The client should tolerete a "no_renegotiation" alert only if:
+ * - the initial handshake has completed, or
+ * - a Server Hello is not yet received
+ */
+ if (session->internals.initial_negotiation_completed ||
+ !(session->internals.hsk_flags & HSK_SERVER_HELLO_RECEIVED)) {
+ STATE = STATE0;
+ return ret;
+ }
+
+ return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET);
+ }
+ return ret;
+ case GNUTLS_E_GOT_APPLICATION_DATA:
+ STATE = STATE0;
+ return ret;
+ default:
+ return ret;
+ }
}
@@ -2807,13 +2835,7 @@ int gnutls_handshake(gnutls_session_t se
}
if (ret < 0) {
- /* In the case of a rehandshake abort
- * we should reset the handshake's internal state.
- */
- if (_gnutls_abort_handshake(session, ret) == 0)
- STATE = STATE0;
-
- return ret;
+ return _gnutls_abort_handshake(session, ret);
}
/* clear handshake buffer */