From 6612a7181af32903b03020090fe361360142258b Mon Sep 17 00:00:00 2001
From: Nikos Mavrogiannopoulos <nmav@redhat.com>
Date: Wed, 9 Dec 2015 10:07:18 +0100
Subject: [PATCH] Prevent a downgrade attack to RSA-MD5 signatures
This is by considering the list of the signature algorithms set by
priorities.
---
lib/ext/signature.c | 18 +--
tests/Makefile.am | 2 +-
tests/sign-md5-rep.c | 344 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 346 insertions(+), 18 deletions(-)
create mode 100644 tests/sign-md5-rep.c
diff --git a/lib/ext/signature.c b/lib/ext/signature.c
index fb971f5..6f3066e 100644
--- a/lib/ext/signature.c
+++ b/lib/ext/signature.c
@@ -313,28 +313,12 @@ _gnutls_session_sign_algo_enabled(gnutls_session_t session,
gnutls_sign_algorithm_t sig)
{
unsigned i;
- int ret;
const version_entry_st *ver = get_version(session);
- sig_ext_st *priv;
- extension_priv_data_t epriv;
if (unlikely(ver == NULL))
return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
- ret =
- _gnutls_ext_get_session_data(session,
- GNUTLS_EXTENSION_SIGNATURE_ALGORITHMS,
- &epriv);
- if (ret < 0) {
- gnutls_assert();
- return 0;
- }
- priv = epriv.ptr;
-
- if (!_gnutls_version_has_selectable_sighash(ver)
- || priv->sign_algorithms_size == 0)
- /* none set, allow all */
- {
+ if (!_gnutls_version_has_selectable_sighash(ver)) {
return 0;
}
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 95d6541..d1c4839 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -84,7 +84,7 @@ ctests = mini-record-2 simple gc set_pkcs12_cred certder certuniqueid \
mini-cert-status mini-rsa-psk global-init sec-params \
fips-test mini-global-load name-constraints x509-extensions \
long-session-id mini-x509-callbacks-intr \
- crlverify init_fds
+ crlverify init_fds sign-md5-rep
if ENABLE_OCSP
ctests += ocsp
diff --git a/tests/sign-md5-rep.c b/tests/sign-md5-rep.c
new file mode 100644
index 0000000..72869fa
--- /dev/null
+++ b/tests/sign-md5-rep.c
@@ -0,0 +1,344 @@
+/*
+ * Copyright (C) 2015 Nikos Mavrogiannopoulos
+ *
+ * Author: Nikos Mavrogiannopoulos
+ *
+ * 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 General Public License
+ * along with GnuTLS; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#if defined(_WIN32)
+
+int main()
+{
+ exit(77);
+}
+
+#else
+
+#include <string.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/dtls.h>
+#include <signal.h>
+
+#include "utils.h"
+
+static void terminate(void);
+
+/* This program tests whether EtM is negotiated as expected.
+ */
+
+static void server_log_func(int level, const char *str)
+{
+ fprintf(stderr, "server|<%d>| %s", level, str);
+}
+
+static void client_log_func(int level, const char *str)
+{
+ fprintf(stderr, "client|<%d>| %s", level, str);
+}
+
+static unsigned char server_cert_pem[] =
+ "-----BEGIN CERTIFICATE-----\n"
+ "MIICVjCCAcGgAwIBAgIERiYdMTALBgkqhkiG9w0BAQUwGTEXMBUGA1UEAxMOR251\n"
+ "VExTIHRlc3QgQ0EwHhcNMDcwNDE4MTMyOTIxWhcNMDgwNDE3MTMyOTIxWjA3MRsw\n"
+ "GQYDVQQKExJHbnVUTFMgdGVzdCBzZXJ2ZXIxGDAWBgNVBAMTD3Rlc3QuZ251dGxz\n"
+ "Lm9yZzCBnDALBgkqhkiG9w0BAQEDgYwAMIGIAoGA17pcr6MM8C6pJ1aqU46o63+B\n"
+ "dUxrmL5K6rce+EvDasTaDQC46kwTHzYWk95y78akXrJutsoKiFV1kJbtple8DDt2\n"
+ "DZcevensf9Op7PuFZKBroEjOd35znDET/z3IrqVgbtm2jFqab7a+n2q9p/CgMyf1\n"
+ "tx2S5Zacc1LWn9bIjrECAwEAAaOBkzCBkDAMBgNVHRMBAf8EAjAAMBoGA1UdEQQT\n"
+ "MBGCD3Rlc3QuZ251dGxzLm9yZzATBgNVHSUEDDAKBggrBgEFBQcDATAPBgNVHQ8B\n"
+ "Af8EBQMDB6AAMB0GA1UdDgQWBBTrx0Vu5fglyoyNgw106YbU3VW0dTAfBgNVHSME\n"
+ "GDAWgBTpPBz7rZJu5gakViyi4cBTJ8jylTALBgkqhkiG9w0BAQUDgYEAaFEPTt+7\n"
+ "bzvBuOf7+QmeQcn29kT6Bsyh1RHJXf8KTk5QRfwp6ogbp94JQWcNQ/S7YDFHglD1\n"
+ "AwUNBRXwd3riUsMnsxgeSDxYBfJYbDLeohNBsqaPDJb7XailWbMQKfAbFQ8cnOxg\n"
+ "rOKLUQRWJ0K3HyXRMhbqjdLIaQiCvQLuizo=\n" "-----END CERTIFICATE-----\n";
+
+const gnutls_datum_t server_cert = { server_cert_pem,
+ sizeof(server_cert_pem)
+};
+
+static unsigned char server_key_pem[] =
+ "-----BEGIN RSA PRIVATE KEY-----\n"
+ "MIICXAIBAAKBgQDXulyvowzwLqknVqpTjqjrf4F1TGuYvkrqtx74S8NqxNoNALjq\n"
+ "TBMfNhaT3nLvxqResm62ygqIVXWQlu2mV7wMO3YNlx696ex/06ns+4VkoGugSM53\n"
+ "fnOcMRP/PciupWBu2baMWppvtr6far2n8KAzJ/W3HZLllpxzUtaf1siOsQIDAQAB\n"
+ "AoGAYAFyKkAYC/PYF8e7+X+tsVCHXppp8AoP8TEZuUqOZz/AArVlle/ROrypg5kl\n"
+ "8YunrvUdzH9R/KZ7saNZlAPLjZyFG9beL/am6Ai7q7Ma5HMqjGU8kTEGwD7K+lbG\n"
+ "iomokKMOl+kkbY/2sI5Czmbm+/PqLXOjtVc5RAsdbgvtmvkCQQDdV5QuU8jap8Hs\n"
+ "Eodv/tLJ2z4+SKCV2k/7FXSKWe0vlrq0cl2qZfoTUYRnKRBcWxc9o92DxK44wgPi\n"
+ "oMQS+O7fAkEA+YG+K9e60sj1K4NYbMPAbYILbZxORDecvP8lcphvwkOVUqbmxOGh\n"
+ "XRmTZUuhBrJhJKKf6u7gf3KWlPl6ShKEbwJASC118cF6nurTjuLf7YKARDjNTEws\n"
+ "qZEeQbdWYINAmCMj0RH2P0mvybrsXSOD5UoDAyO7aWuqkHGcCLv6FGG+qwJAOVqq\n"
+ "tXdUucl6GjOKKw5geIvRRrQMhb/m5scb+5iw8A4LEEHPgGiBaF5NtJZLALgWfo5n\n"
+ "hmC8+G8F0F78znQtPwJBANexu+Tg5KfOnzSILJMo3oXiXhf5PqXIDmbN0BKyCKAQ\n"
+ "LfkcEcUbVfmDaHpvzwY9VEaoMOKVLitETXdNSxVpvWM=\n"
+ "-----END RSA PRIVATE KEY-----\n";
+
+const gnutls_datum_t server_key = { server_key_pem,
+ sizeof(server_key_pem)
+};
+
+
+static int handshake_callback(gnutls_session_t session, unsigned int htype,
+ unsigned post, unsigned int incoming)
+{
+ gnutls_priority_set_direct(session, "NORMAL:-KX-ALL:+ECDHE-RSA", NULL);
+ return 0;
+}
+
+
+/* A very basic TLS client, with anonymous authentication.
+ */
+
+#define MAX_BUF 1024
+
+static void client(int fd)
+{
+ int ret;
+ char buffer[MAX_BUF + 1];
+ gnutls_certificate_credentials_t x509_cred;
+ gnutls_session_t session;
+ /* Need to enable anonymous KX specifically. */
+
+ global_init();
+
+ if (debug) {
+ gnutls_global_set_log_function(client_log_func);
+ gnutls_global_set_log_level(7);
+ }
+
+ gnutls_certificate_allocate_credentials(&x509_cred);
+
+ /* Initialize TLS session
+ */
+ gnutls_init(&session, GNUTLS_CLIENT);
+
+ /* Use default priorities */
+ gnutls_priority_set_direct(session, "NORMAL:-KX-ALL:+ECDHE-RSA:-SIGN-ALL:+SIGN-RSA-MD5", NULL);
+
+ /* put the anonymous credentials to the current session
+ */
+ gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+
+ gnutls_transport_set_int(session, fd);
+ gnutls_handshake_set_hook_function(session, GNUTLS_HANDSHAKE_SERVER_KEY_EXCHANGE,
+ GNUTLS_HOOK_PRE,
+ handshake_callback);
+
+ /* Perform the TLS handshake
+ */
+ do {
+ ret = gnutls_handshake(session);
+ }
+ while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
+
+ if (ret == GNUTLS_E_UNSUPPORTED_SIGNATURE_ALGORITHM) {
+ /* success */
+ goto end;
+ }
+
+ if (ret < 0) {
+ terminate();
+ fail("client: Handshake failed: %s\n", gnutls_strerror(ret));
+ exit(1);
+ } else {
+ if (debug)
+ success("client: Handshake was completed\n");
+ }
+
+ if (gnutls_sign_algorithm_get(session) == GNUTLS_SIGN_RSA_MD5) {
+ terminate();
+ fail("client: MD5 was negotiated\n");
+ exit(1);
+ }
+ success("client: %s was negotiated\n", gnutls_sign_get_name(gnutls_sign_algorithm_get(session)));
+
+ if (debug)
+ success("client: TLS version is: %s\n",
+ gnutls_protocol_get_name
+ (gnutls_protocol_get_version(session)));
+
+ do {
+ do {
+ ret = gnutls_record_recv(session, buffer, MAX_BUF);
+ } while (ret == GNUTLS_E_AGAIN
+ || ret == GNUTLS_E_INTERRUPTED);
+ } while (ret > 0);
+
+ if (ret == 0) {
+ if (debug)
+ success
+ ("client: Peer has closed the TLS connection\n");
+ goto end;
+ } else if (ret < 0) {
+ terminate();
+ fail("client: Error: %s\n", gnutls_strerror(ret));
+ exit(1);
+ }
+
+ gnutls_bye(session, GNUTLS_SHUT_WR);
+
+ end:
+
+ close(fd);
+
+ gnutls_deinit(session);
+
+ gnutls_certificate_free_credentials(x509_cred);
+
+ gnutls_global_deinit();
+}
+
+
+/* These are global */
+pid_t child;
+
+static void terminate(void)
+{
+ kill(child, SIGTERM);
+ exit(1);
+}
+
+static void server(int fd)
+{
+ int ret;
+ char buffer[MAX_BUF + 1];
+ gnutls_session_t session;
+ gnutls_certificate_credentials_t x509_cred;
+
+ /* this must be called once in the program
+ */
+ global_init();
+ memset(buffer, 0, sizeof(buffer));
+
+ if (debug) {
+ gnutls_global_set_log_function(server_log_func);
+ gnutls_global_set_log_level(4711);
+ }
+
+ gnutls_certificate_allocate_credentials(&x509_cred);
+ gnutls_certificate_set_x509_key_mem(x509_cred, &server_cert,
+ &server_key,
+ GNUTLS_X509_FMT_PEM);
+
+ gnutls_init(&session, GNUTLS_SERVER);
+
+ /* avoid calling all the priority functions, since the defaults
+ * are adequate.
+ */
+ gnutls_priority_set_direct(session, "NORMAL:-KX-ALL:+ECDHE-RSA:-SIGN-ALL:+SIGN-RSA-MD5", NULL);
+
+ gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+
+ gnutls_transport_set_int(session, fd);
+
+ do {
+ ret = gnutls_handshake(session);
+ } while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
+ if (ret < 0) {
+ /* failure is expected here */
+ goto end;
+ }
+
+ if (debug) {
+ success("server: Handshake was completed\n");
+ success("server: %s was negotiated\n", gnutls_sign_get_name(gnutls_sign_algorithm_get(session)));
+ }
+
+ if (debug)
+ success("server: TLS version is: %s\n",
+ gnutls_protocol_get_name
+ (gnutls_protocol_get_version(session)));
+
+ /* do not wait for the peer to close the connection.
+ */
+ gnutls_bye(session, GNUTLS_SHUT_WR);
+
+ end:
+ close(fd);
+ gnutls_deinit(session);
+
+ gnutls_certificate_free_credentials(x509_cred);
+
+ gnutls_global_deinit();
+
+ if (debug)
+ success("server: finished\n");
+}
+
+static void ch_handler(int sig)
+{
+ int status;
+ wait(&status);
+ if (WEXITSTATUS(status) != 0 ||
+ (WIFSIGNALED(status) && WTERMSIG(status) == SIGSEGV)) {
+ if (WIFSIGNALED(status))
+ fail("Child died with sigsegv\n");
+ else
+ fail("Child died with status %d\n",
+ WEXITSTATUS(status));
+ terminate();
+ }
+ return;
+}
+
+void doit(void)
+{
+ int fd[2];
+ int ret;
+
+ signal(SIGCHLD, ch_handler);
+
+ ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fd);
+ if (ret < 0) {
+ perror("socketpair");
+ exit(1);
+ }
+
+ child = fork();
+ if (child < 0) {
+ perror("fork");
+ fail("fork");
+ exit(1);
+ }
+
+ if (child) {
+ /* parent */
+ close(fd[1]);
+ client(fd[0]);
+ kill(child, SIGTERM);
+ } else {
+ close(fd[0]);
+ server(fd[1]);
+ exit(0);
+ }
+}
+
+#endif /* _WIN32 */
--
2.5.0