priorities: introduced %FORCE_ETMtmp-measure-record

This introduces a priority string option to force encrypt-then-mac
during negotiation, to prevent negotiating the legacy CBC ciphersuites.

Resolves #472

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

9 files changed, 438 insertions, 5 deletions

diff --git a/doc/cha-gtls-app.texi b/doc/cha-gtls-app.texi
index 5ecb3d7382..c23c848d90 100644
--- a/doc/cha-gtls-app.texi
+++ b/doc/cha-gtls-app.texi
@@ -1350,6 +1350,10 @@ in certificates.
 will disable the encrypt-then-mac TLS extension (RFC7366). This is
 implied by the %COMPAT keyword.
 
+@item %FORCE_ETM @tab
+negotiate CBC ciphersuites only when both sides of the connection support
+encrypt-then-mac TLS extension (RFC7366).
+
 @item %DISABLE_SAFE_RENEGOTIATION @tab
 will completely disable safe renegotiation
 completely.  Do not use unless you know what you are doing.
diff --git a/lib/algorithms/ciphersuites.c b/lib/algorithms/ciphersuites.c
index 02023ce2a9..ac1fdf9f41 100644
--- a/lib/algorithms/ciphersuites.c
+++ b/lib/algorithms/ciphersuites.c
@@ -1405,6 +1405,14 @@ const char *gnutls_cipher_suite_info(size_t idx,
 					continue; \
 			}
 
+#define CIPHER_CHECK(algo) \
+			if (session->internals.priorities->force_etm && !have_etm) { \
+				const cipher_entry_st *_cipher; \
+				_cipher = cipher_to_entry(algo); \
+				if (_cipher == NULL || _gnutls_cipher_type(_cipher) == CIPHER_BLOCK) \
+					continue; \
+			}
+
 #define KX_SRP_CHECKS(kx, action) \
 	if (kx == GNUTLS_KX_SRP_RSA || kx == GNUTLS_KX_SRP_DSS) { \
 		if (!_gnutls_get_cred(session, GNUTLS_CRD_SRP)) { \
@@ -1450,11 +1458,20 @@ _gnutls_figure_common_ciphersuite(gnutls_session_t session,
 	gnutls_credentials_type_t cred_type = GNUTLS_CRD_CERTIFICATE; /* default for TLS1.3 */
 	unsigned int no_cert_found = 0;
 	const gnutls_group_entry_st *sgroup = NULL;
+	gnutls_ext_priv_data_t epriv;
+	unsigned have_etm = 0;
 
 	if (version == NULL) {
 		return gnutls_assert_val(GNUTLS_E_NO_CIPHER_SUITES);
 	}
 
+	/* we figure whether etm is negotiated by checking the raw extension data
+	 * because we only set (security_params) EtM to true only after the ciphersuite is
+	 * negotiated. */
+	ret = _gnutls_hello_ext_get_priv(session, GNUTLS_EXTENSION_ETM, &epriv);
+	if (ret >= 0 && ((intptr_t)epriv) != 0)
+		have_etm = 1;
+
 	/* If we didn't receive the supported_groups extension, then
 	 * we should assume that SECP256R1 is supported; that is required
 	 * by RFC4492, probably to allow SSLv2 hellos negotiate elliptic curve
@@ -1474,6 +1491,8 @@ _gnutls_figure_common_ciphersuite(gnutls_session_t session,
 
 			kx = peer_clist->entry[i]->kx_algorithm;
 
+			CIPHER_CHECK(peer_clist->entry[i]->block_algorithm);
+
 			if (!version->tls13_sem)
 				cred_type = _gnutls_map_kx_get_cred(kx, 1);
 
@@ -1510,6 +1529,8 @@ _gnutls_figure_common_ciphersuite(gnutls_session_t session,
 		for (j = 0; j < session->internals.priorities->cs.size; j++) {
 			VERSION_CHECK(session->internals.priorities->cs.entry[j]);
 
+			CIPHER_CHECK(session->internals.priorities->cs.entry[j]->block_algorithm);
+
 			for (i = 0; i < peer_clist->size; i++) {
 				_gnutls_debug_log("checking %.2x.%.2x (%s) for compatibility\n",
 					(unsigned)peer_clist->entry[i]->id[0],
diff --git a/lib/gnutls_int.h b/lib/gnutls_int.h
index 320c394d18..0db05af163 100644
--- a/lib/gnutls_int.h
+++ b/lib/gnutls_int.h
@@ -900,6 +900,7 @@ struct gnutls_priority_st {
 	bool no_tickets;
 	bool have_cbc;
 	bool have_psk;
+	bool force_etm;
 	unsigned int additional_verify_flags;
 
 	/* TLS_FALLBACK_SCSV */
diff --git a/lib/handshake.c b/lib/handshake.c
index 30e229f3d0..278769e2f8 100644
--- a/lib/handshake.c
+++ b/lib/handshake.c
@@ -1825,7 +1825,6 @@ read_server_hello(gnutls_session_t session,
 	 */
 	if (!vers->tls13_sem &&
 	    client_check_if_resuming(session, session_id, session_id_len) == 0) {
-
 		ret =
 		    _gnutls_parse_hello_extensions(session, GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO,
 						   GNUTLS_EXT_MANDATORY,
@@ -1878,6 +1877,14 @@ read_server_hello(gnutls_session_t session,
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
+	/* check if EtM is required */
+	if (!vers->tls13_sem && session->internals.priorities->force_etm && !session->security_parameters.etm) {
+		const cipher_entry_st *cipher = cipher_to_entry(session->security_parameters.cs->block_algorithm);
+		if (_gnutls_cipher_type(cipher) == CIPHER_BLOCK)
+			return gnutls_assert_val(GNUTLS_E_UNWANTED_ALGORITHM);
+	}
+
+
 	ret =
 	    _gnutls_parse_hello_extensions(session,
 					   ext_parse_flag,
diff --git a/lib/priority.c b/lib/priority.c
index 1ebd6b4695..a749678580 100644
--- a/lib/priority.c
+++ b/lib/priority.c
@@ -809,6 +809,10 @@ static void enable_no_etm(gnutls_priority_t c)
 {
 	c->_no_etm = 1;
 }
+static void enable_force_etm(gnutls_priority_t c)
+{
+	c->force_etm = 1;
+}
 static void enable_no_tickets(gnutls_priority_t c)
 {
 	c->no_tickets = 1;
diff --git a/lib/priority_options.gperf b/lib/priority_options.gperf
index 44968d4327..a955ec85e6 100644
--- a/lib/priority_options.gperf
+++ b/lib/priority_options.gperf
@@ -10,6 +10,7 @@ DUMBFW, enable_dumbfw
 NO_EXTENSIONS, enable_no_extensions
 NO_TICKETS, enable_no_tickets
 NO_ETM, enable_no_etm
+FORCE_ETM, enable_force_etm
 NO_SESSION_HASH, enable_no_ext_master_secret
 STATELESS_COMPRESSION, dummy_func
 VERIFY_ALLOW_BROKEN, enable_verify_allow_broken
diff --git a/tests/Makefile.am b/tests/Makefile.am
index e095e36cbc..9f4b053e43 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -153,7 +153,7 @@ ctests += mini-record-2 simple gnutls_hmac_fast set_pkcs12_cred cert certuniquei
 	 pubkey-import-export sign-is-secure spki spki-abstract rsa-rsa-pss \
 	 mini-dtls-fork mini-dtls-pthread mini-key-material x509cert-invalid \
 	 tls-ext-register tls-supplemental mini-dtls0-9 duplicate-extensions \
-	 record-retvals mini-server-name tls-etm x509-cert-callback alerts \
+	 record-retvals mini-server-name tls-etm tls-force-etm x509-cert-callback alerts \
 	 client-sign-md5-rep tls12-invalid-key-exchanges session-rdn-read \
 	 tls13-cert-key-exchange x509-cert-callback-ocsp gnutls_ocsp_resp_list_import2 \
 	 server-sign-md5-rep privkey-keygen mini-tls-nonblock no-signal pkcs7-gen dtls-etm \
diff --git a/tests/tls-force-etm.c b/tests/tls-force-etm.c
new file mode 100644
index 0000000000..1cc42ec5ec
--- /dev/null
+++ b/tests/tls-force-etm.c
@@ -0,0 +1,396 @@
+/*
+ * Copyright (C) 2015-2018 Red Hat, Inc.
+ *
+ * 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 Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+#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 <assert.h>
+
+#include "utils.h"
+#include "cert-common.h"
+
+/* This program tests whether forced 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);
+}
+
+#define MAX_BUF 1024
+
+static void client(int fd, const char *prio, unsigned etm, int eret)
+{
+	int ret;
+	char buffer[MAX_BUF + 1];
+	gnutls_anon_client_credentials_t anoncred;
+	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_anon_allocate_client_credentials(&anoncred);
+	gnutls_certificate_allocate_credentials(&x509_cred);
+
+	assert(gnutls_init(&session, GNUTLS_CLIENT)>=0);
+	gnutls_handshake_set_timeout(session, 20 * 1000);
+
+	/* Use default priorities */
+	assert(gnutls_priority_set_direct(session, prio, NULL)>=0);
+
+	/* put the anonymous credentials to the current session
+	 */
+	gnutls_credentials_set(session, GNUTLS_CRD_ANON, anoncred);
+	gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+
+	gnutls_transport_set_int(session, fd);
+
+	/* Perform the TLS handshake
+	 */
+	do {
+		ret = gnutls_handshake(session);
+	}
+	while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
+
+	if (eret < 0) {
+		if (eret != ret) {
+			fail("client: Handshake failed with unexpected error: %s\n", gnutls_strerror(ret));
+		}
+		goto end;
+	}
+
+	if (ret < 0) {
+		fail("client: Handshake failed: %s\n", gnutls_strerror(ret));
+	} else {
+		if (debug)
+			success("client: Handshake was completed\n");
+	}
+
+	if (debug)
+		success("client: TLS version is: %s\n",
+			gnutls_protocol_get_name
+			(gnutls_protocol_get_version(session)));
+
+	if (etm != 0 && gnutls_session_etm_status(session) == 0) {
+		fail("client: EtM was not negotiated with %s!\n", prio);
+		exit(1);
+	} else if (etm == 0 && gnutls_session_etm_status(session) != 0) {
+		fail("client: EtM was negotiated with %s!\n", prio);
+		exit(1);
+	}
+
+	if (etm != 0 && ((gnutls_session_get_flags(session) & GNUTLS_SFLAGS_ETM) == 0)) {
+		fail("client: EtM was not negotiated with %s!\n", prio);
+		exit(1);
+	} else if (etm == 0 && ((gnutls_session_get_flags(session) & GNUTLS_SFLAGS_ETM) != 0)) {
+		fail("client: EtM was negotiated with %s!\n", prio);
+		exit(1);
+	}
+
+	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) {
+		if (ret != 0) {
+			fail("client: Error: %s\n", gnutls_strerror(ret));
+			exit(1);
+		}
+	}
+
+	gnutls_bye(session, GNUTLS_SHUT_WR);
+
+      end:
+
+	close(fd);
+
+	gnutls_deinit(session);
+
+	gnutls_anon_free_client_credentials(anoncred);
+	gnutls_certificate_free_credentials(x509_cred);
+
+	gnutls_global_deinit();
+}
+
+
+static void server(int fd, const char *prio, unsigned etm, int eret)
+{
+	int ret;
+	char buffer[MAX_BUF + 1];
+	gnutls_session_t session;
+	gnutls_anon_server_credentials_t anoncred;
+	gnutls_certificate_credentials_t x509_cred;
+	unsigned to_send = sizeof(buffer)/4;
+
+	/* 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_anon_allocate_server_credentials(&anoncred);
+
+	assert(gnutls_init(&session, GNUTLS_SERVER)>=0);
+	gnutls_handshake_set_timeout(session, 20 * 1000);
+
+	/* avoid calling all the priority functions, since the defaults
+	 * are adequate.
+	 */
+	assert(gnutls_priority_set_direct(session, prio, NULL) >= 0);
+
+	gnutls_credentials_set(session, GNUTLS_CRD_ANON, anoncred);
+	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 (eret < 0) {
+		if (eret != -1 && eret != ret) {
+			fail("server: Handshake failed with unexpected error: %s\n", gnutls_strerror(ret));
+		}
+		goto end;
+	}
+
+	if (ret < 0) {
+		close(fd);
+		gnutls_deinit(session);
+		fail("server: Handshake has failed (%s)\n\n",
+		     gnutls_strerror(ret));
+	}
+
+	if (etm != 0 && gnutls_session_etm_status(session) == 0) {
+		fail("server: EtM was not negotiated with %s!\n", prio);
+		exit(1);
+	} else if (etm == 0 && gnutls_session_etm_status(session) != 0) {
+		fail("server: EtM was negotiated with %s!\n", prio);
+		exit(1);
+	}
+
+	if (etm != 0 && ((gnutls_session_get_flags(session) & GNUTLS_SFLAGS_ETM) == 0)) {
+		fail("server: EtM was not negotiated with %s!\n", prio);
+		exit(1);
+	} else if (etm == 0 && ((gnutls_session_get_flags(session) & GNUTLS_SFLAGS_ETM) != 0)) {
+		fail("server: EtM was negotiated with %s!\n", prio);
+		exit(1);
+	}
+
+	if (debug)
+		success("server: Handshake was completed\n");
+
+	if (debug)
+		success("server: TLS version is: %s\n",
+			gnutls_protocol_get_name
+			(gnutls_protocol_get_version(session)));
+
+	do {
+		do {
+			ret =
+			    gnutls_record_send(session, buffer,
+						sizeof(buffer));
+		} while (ret == GNUTLS_E_AGAIN
+			 || ret == GNUTLS_E_INTERRUPTED);
+
+		if (ret < 0) {
+			fail("Error sending %d byte packet: %s\n", to_send,
+			     gnutls_strerror(ret));
+		}
+		to_send++;
+	}
+	while (to_send < 64);
+
+	to_send = -1;
+	/* do not wait for the peer to close the connection.
+	 */
+	gnutls_bye(session, GNUTLS_SHUT_WR);
+ end:
+	close(fd);
+	gnutls_deinit(session);
+
+	gnutls_anon_free_server_credentials(anoncred);
+	gnutls_certificate_free_credentials(x509_cred);
+
+	gnutls_global_deinit();
+
+	if (debug)
+		success("server: finished\n");
+}
+
+struct test_st {
+	const char *name;
+	const char *server_prio;
+	const char *client_prio;
+	unsigned etm;
+	int client_err;
+	int server_err;
+};
+
+static void start(struct test_st *test)
+{
+	int fd[2];
+	int ret, status;
+	pid_t child;
+
+
+	success("trying: %s\n", test->name);
+	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]);
+		server(fd[0], test->server_prio, test->etm, test->server_err);
+		wait(&status);
+		check_wait_status(status);
+	} else {
+		close(fd[0]);
+		client(fd[1], test->client_prio, test->etm, test->client_err);
+		exit(0);
+	}
+}
+
+#define AES_CBC "NONE:+VERS-TLS1.0:-CIPHER-ALL:+AES-128-CBC:+SHA1:+SIGN-ALL:+COMP-ALL:+ANON-ECDH:+CURVE-ALL"
+#define AES_CBC_SHA256 "NONE:+VERS-TLS1.2:-CIPHER-ALL:+RSA:+AES-128-CBC:+AES-256-CBC:+SHA256:+SIGN-ALL:+COMP-ALL:+ANON-ECDH:+CURVE-ALL"
+#define AES_GCM "NONE:+VERS-TLS1.2:-CIPHER-ALL:+RSA:+AES-128-GCM:+MAC-ALL:+SIGN-ALL:+COMP-ALL:+ANON-ECDH:+CURVE-ALL"
+
+#define AES_CBC_TLS12 "NONE:+VERS-TLS1.2:-CIPHER-ALL:+RSA:+AES-128-CBC:+MAC-ALL:+SIGN-ALL:+COMP-ALL:+ANON-ECDH:+CURVE-ALL"
+
+static void ch_handler(int sig)
+{
+	return;
+}
+
+static struct test_st tests[] = {
+	{
+		.name = "aes-cbc-hmac-sha1 with force etm",
+		.server_prio = AES_CBC":%FORCE_ETM",
+		.client_prio = AES_CBC":%FORCE_ETM",
+		.etm = 1
+	},
+	{
+		.name = "aes-cbc-hmac-sha256 with force etm",
+		.server_prio = AES_CBC_SHA256":%FORCE_ETM",
+		.client_prio = AES_CBC_SHA256":%FORCE_ETM",
+		.etm = 1
+	},
+	{
+		.name = "server aes-cbc-hmac-sha1 with force etm, gcm fallback",
+		.server_prio = AES_CBC_TLS12":+AES-128-GCM:%FORCE_ETM",
+		.client_prio = AES_CBC_TLS12":+AES-128-GCM:%NO_ETM",
+		.etm = 0
+	},
+	{
+		.name = "aes-gcm with force etm",
+		.server_prio = AES_GCM":%FORCE_ETM",
+		.client_prio = AES_GCM":%FORCE_ETM",
+		.etm = 0
+	},
+	{
+		.name = "server aes-cbc-hmac-sha1 with force etm failure",
+		.server_prio = AES_CBC":%FORCE_ETM",
+		.client_prio = AES_CBC":%NO_ETM",
+		.etm = 0,
+		.client_err = GNUTLS_E_PREMATURE_TERMINATION,
+		.server_err = GNUTLS_E_NO_CIPHER_SUITES
+	},
+	{
+		.name = "client aes-cbc-hmac-sha1 with force etm failure",
+		.server_prio = AES_CBC":%NO_ETM",
+		.client_prio = AES_CBC":%FORCE_ETM",
+		.etm = 0,
+		.client_err = GNUTLS_E_UNWANTED_ALGORITHM,
+		.server_err = -1
+	}
+};
+
+void doit(void)
+{
+	unsigned i;
+	signal(SIGCHLD, ch_handler);
+
+	for (i=0;i<sizeof(tests)/sizeof(tests[0]);i++) {
+		start(&tests[i]);
+	}
+}
+#endif				/* _WIN32 */
diff --git a/tests/utils.h b/tests/utils.h
index 1247402e9f..58e9aef8a2 100644
--- a/tests/utils.h
+++ b/tests/utils.h
@@ -16,9 +16,8 @@
  * 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
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
  */
 
 #ifndef UTILS_H