File gnutls-CVE-2025-6395.patch of Package gnutls.39718
From 23135619773e6ec087ff2abc65405bd4d5676bad Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Mon, 7 Jul 2025 11:15:45 +0900
Subject: [PATCH] handshake: clear HSK_PSK_SELECTED is when resetting binders
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When a TLS 1.3 handshake involves HRR and resumption or PSK, and the
second Client Hello omits PSK, the server would result in a NULL
pointer dereference as the PSK binder information is cleared while the
HSK_PSK_SELECTED flag is still set. This makes sure that
HSK_PSK_SELECTED flag is always cleared when the PSK binders are
reset. This also makes it clear the HSK_PSK_SELECTED flag is valid
only during a handshake; after that, whether PSK is used can be
checked with gnutls_auth_client_get_type.
Reported by Stefan Bühler.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
.gitignore | 1 +
NEWS | 4 +
lib/handshake.c | 25 +++-
lib/state.c | 4 +-
tests/Makefile.am | 2 +
tests/tls13/hello_retry_request_psk.c | 173 ++++++++++++++++++++++++++
6 files changed, 205 insertions(+), 4 deletions(-)
create mode 100644 tests/tls13/hello_retry_request_psk.c
Index: gnutls-3.7.3/lib/handshake.c
===================================================================
--- gnutls-3.7.3.orig/lib/handshake.c
+++ gnutls-3.7.3/lib/handshake.c
@@ -590,9 +590,28 @@ static int set_auth_types(gnutls_session
/* Under TLS1.3 this returns a KX which matches the negotiated
* groups from the key shares; if we are resuming then the KX seen
* here doesn't match the original session. */
- if (!session->internals.resumed)
- kx = gnutls_kx_get(session);
- else
+ if (!session->internals.resumed) {
+ const gnutls_group_entry_st *group = get_group(session);
+
+ if (session->internals.hsk_flags & HSK_PSK_SELECTED) {
+ if (group) {
+ kx = group->pk == GNUTLS_PK_DH ?
+ GNUTLS_KX_DHE_PSK :
+ GNUTLS_KX_ECDHE_PSK;
+ } else {
+ kx = GNUTLS_KX_PSK;
+ }
+ } else if (group) {
+ /* Not necessarily be RSA, but just to
+ * make _gnutls_map_kx_get_cred below
+ * work.
+ */
+ kx = group->pk == GNUTLS_PK_DH ?
+ GNUTLS_KX_DHE_RSA :
+ GNUTLS_KX_ECDHE_RSA;
+ } else
+ kx = GNUTLS_KX_UNKNOWN;
+ } else
kx = GNUTLS_KX_UNKNOWN;
} else {
/* TLS1.2 or earlier, kx is associated with ciphersuite */
Index: gnutls-3.7.3/lib/state.c
===================================================================
--- gnutls-3.7.3.orig/lib/state.c
+++ gnutls-3.7.3/lib/state.c
@@ -206,7 +206,8 @@ gnutls_kx_algorithm_t gnutls_kx_get(gnut
const gnutls_group_entry_st *group = get_group(session);
if (ver->tls13_sem) {
- if (session->internals.hsk_flags & HSK_PSK_SELECTED) {
+ if (gnutls_auth_client_get_type(session) ==
+ GNUTLS_CRD_PSK) {
if (group) {
if (group->pk == GNUTLS_PK_DH)
return GNUTLS_KX_DHE_PSK;
@@ -328,6 +329,7 @@ void reset_binders(gnutls_session_t sess
_gnutls_free_temp_key_datum(&session->key.binders[0].psk);
_gnutls_free_temp_key_datum(&session->key.binders[1].psk);
memset(session->key.binders, 0, sizeof(session->key.binders));
+ session->internals.hsk_flags &= ~HSK_PSK_SELECTED;
}
/* Check whether certificate credentials of type @cert_type are set
Index: gnutls-3.7.3/tests/Makefile.am
===================================================================
--- gnutls-3.7.3.orig/tests/Makefile.am
+++ gnutls-3.7.3/tests/Makefile.am
@@ -127,6 +127,8 @@ ctests += tls13/hello_retry_request
ctests += tls13/hello_retry_request_resume
+ctests += tls13/hello_retry_request_psk
+
ctests += tls13/psk-ext
ctests += tls13/key_update
Index: gnutls-3.7.3/tests/tls13/hello_retry_request_psk.c
===================================================================
--- /dev/null
+++ gnutls-3.7.3/tests/tls13/hello_retry_request_psk.c
@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) 2017-2025 Red Hat, Inc.
+ *
+ * Author: Nikos Mavrogiannopoulos, Daiki Ueno
+ *
+ * This file is part of GnuTLS.
+ *
+ * GnuTLS is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuTLS is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#include <string.h>
+#include <gnutls/gnutls.h>
+#include <assert.h>
+
+#include "cert-common.h"
+#include "utils.h"
+#include "tls13/ext-parse.h"
+#include "eagain-common.h"
+
+/* This program exercises the case where a TLS 1.3 handshake ends up
+ * with HRR, and the first CH includes PSK while the 2nd CH omits
+ * it */
+
+const char *testname = "hello entry request";
+
+const char *side = "";
+
+#define myfail(fmt, ...) fail("%s: " fmt, testname, ##__VA_ARGS__)
+
+static void tls_log_func(int level, const char *str)
+{
+ fprintf(stderr, "%s|<%d>| %s", side, level, str);
+}
+
+struct ctx_st {
+ unsigned hrr_seen;
+ unsigned hello_counter;
+};
+
+static int pskfunc(gnutls_session_t session, const char *username,
+ gnutls_datum_t *key)
+{
+ if (debug)
+ printf("psk: username %s\n", username);
+ key->data = gnutls_malloc(4);
+ key->data[0] = 0xDE;
+ key->data[1] = 0xAD;
+ key->data[2] = 0xBE;
+ key->data[3] = 0xEF;
+ key->size = 4;
+ return 0;
+}
+
+static int hello_callback(gnutls_session_t session, unsigned int htype,
+ unsigned post, unsigned int incoming,
+ const gnutls_datum_t *msg)
+{
+ struct ctx_st *ctx = gnutls_session_get_ptr(session);
+ assert(ctx != NULL);
+
+ if (htype == GNUTLS_HANDSHAKE_HELLO_RETRY_REQUEST)
+ ctx->hrr_seen = 1;
+
+ if (htype == GNUTLS_HANDSHAKE_CLIENT_HELLO) {
+ if (post == GNUTLS_HOOK_POST)
+ ctx->hello_counter++;
+ else {
+ /* Unset the PSK credential to omit the extension */
+ gnutls_credentials_set(session, GNUTLS_CRD_PSK, NULL);
+ }
+ }
+
+ return 0;
+}
+
+void doit(void)
+{
+ int sret, cret;
+ gnutls_psk_server_credentials_t scred;
+ gnutls_psk_client_credentials_t ccred;
+ gnutls_certificate_credentials_t ccred2;
+ gnutls_session_t server, client;
+ /* Need to enable anonymous KX specifically. */
+ const gnutls_datum_t key = { (void *)"DEADBEEF", 8 };
+
+ struct ctx_st ctx;
+ memset(&ctx, 0, sizeof(ctx));
+
+ global_init();
+
+ gnutls_global_set_log_function(tls_log_func);
+ if (debug)
+ gnutls_global_set_log_level(9);
+
+ /* Init server */
+ assert(gnutls_psk_allocate_server_credentials(&scred) >= 0);
+ gnutls_psk_set_server_credentials_function(scred, pskfunc);
+
+ gnutls_init(&server, GNUTLS_SERVER);
+
+ assert(gnutls_priority_set_direct(
+ server,
+ "NORMAL:-VERS-ALL:+VERS-TLS1.3:-GROUP-ALL:+GROUP-X25519:+DHE-PSK",
+ NULL) >= 0);
+
+ gnutls_credentials_set(server, GNUTLS_CRD_PSK, scred);
+ gnutls_transport_set_push_function(server, server_push);
+ gnutls_transport_set_pull_function(server, server_pull);
+ gnutls_transport_set_ptr(server, server);
+
+ /* Init client */
+ assert(gnutls_psk_allocate_client_credentials(&ccred) >= 0);
+ gnutls_psk_set_client_credentials(ccred, "test", &key,
+ GNUTLS_PSK_KEY_HEX);
+ assert(gnutls_certificate_allocate_credentials(&ccred2) >= 0);
+
+ assert(gnutls_init(&client, GNUTLS_CLIENT | GNUTLS_KEY_SHARE_TOP) >= 0);
+
+ gnutls_session_set_ptr(client, &ctx);
+
+ cret = gnutls_priority_set_direct(
+ client,
+ "NORMAL:-VERS-ALL:+VERS-TLS1.3:-GROUP-ALL:+GROUP-SECP256R1:+GROUP-X25519:+DHE-PSK",
+ NULL);
+ if (cret < 0)
+ myfail("cannot set TLS 1.3 priorities\n");
+
+ gnutls_credentials_set(client, GNUTLS_CRD_PSK, ccred);
+ gnutls_credentials_set(client, GNUTLS_CRD_CERTIFICATE, ccred2);
+ gnutls_transport_set_push_function(client, client_push);
+ gnutls_transport_set_pull_function(client, client_pull);
+ gnutls_transport_set_ptr(client, client);
+
+ gnutls_handshake_set_hook_function(client, GNUTLS_HANDSHAKE_ANY,
+ GNUTLS_HOOK_BOTH, hello_callback);
+
+ HANDSHAKE_EXPECT(client, server, GNUTLS_E_AGAIN,
+ GNUTLS_E_INSUFFICIENT_CREDENTIALS);
+
+ assert(ctx.hrr_seen != 0);
+
+ gnutls_bye(client, GNUTLS_SHUT_WR);
+ gnutls_bye(server, GNUTLS_SHUT_WR);
+
+ gnutls_deinit(client);
+ gnutls_deinit(server);
+
+ gnutls_psk_free_server_credentials(scred);
+ gnutls_psk_free_client_credentials(ccred);
+ gnutls_certificate_free_credentials(ccred2);
+
+ gnutls_global_deinit();
+ reset_buffers();
+}
