server auth: disable TLS 1.3 if no signature algorithm is usable

This is a server side counterpart of
005a4d04145707daad9588acedfdb5f6cd97c80c.

Instead of signalling an error when no algorithm is usable in TLS 1.3,
it downgrades the session to TLS 1.2 with a warning.

Signed-off-by: Daiki Ueno <dueno@redhat.com>

9 files changed, 417 insertions, 2 deletions

diff --git a/.gitignore b/.gitignore
index 4c0a25a3bf..dd17220f64 100644
--- a/.gitignore
+++ b/.gitignore
@@ -582,6 +582,7 @@ tests/pkcs11/pkcs11-pubkey-import-ecdsa
 tests/pkcs11/pkcs11-pubkey-import-rsa
 tests/pkcs11/pkcs11-rsa-pss-privkey-test
 tests/pkcs11/tls-neg-pkcs11-key
+tests/pkcs11/tls-neg-pkcs11-no-key
 tests/pkcs12-decode/Makefile
 tests/pkcs12-decode/Makefile.in
 tests/pkcs12_encode
diff --git a/lib/algorithms.h b/lib/algorithms.h
index 6f82879d31..870e9d6d35 100644
--- a/lib/algorithms.h
+++ b/lib/algorithms.h
@@ -395,6 +395,9 @@ _gnutls_tls_aid_to_sign(uint8_t id0, uint8_t id1, const version_entry_st *ver);
 const sign_algorithm_st *_gnutls_sign_to_tls_aid(gnutls_sign_algorithm_t
 						 sign);
 
+const gnutls_sign_entry_st *
+_gnutls13_sign_get_compatible_with_privkey(gnutls_privkey_t privkey);
+
 unsigned int _gnutls_pk_bits_to_subgroup_bits(unsigned int pk_bits);
 gnutls_digest_algorithm_t _gnutls_pk_bits_to_sha_hash(unsigned int pk_bits);
 
diff --git a/lib/algorithms/sign.c b/lib/algorithms/sign.c
index e2c926b066..fc5aa0a75e 100644
--- a/lib/algorithms/sign.c
+++ b/lib/algorithms/sign.c
@@ -736,3 +736,16 @@ _gnutls_tls_aid_to_sign_entry(uint8_t id0, uint8_t id1, const version_entry_st *
 
 	return NULL;
 }
+
+const gnutls_sign_entry_st *
+_gnutls13_sign_get_compatible_with_privkey(gnutls_privkey_t privkey)
+{
+	GNUTLS_SIGN_LOOP(
+		if (p->tls13_ok &&
+		    _gnutls_privkey_compatible_with_sig(privkey, p->id)) {
+			return p;
+		}
+	);
+
+	return NULL;
+}
diff --git a/lib/auth.c b/lib/auth.c
index df438ddc7a..f9e6900803 100644
--- a/lib/auth.c
+++ b/lib/auth.c
@@ -154,6 +154,10 @@ gnutls_credentials_set(gnutls_session_t session,
 				}
 			}
 
+			if (session->security_parameters.entity == GNUTLS_SERVER &&
+			    !c->tls13_ok)
+				allow_tls13 = 0;
+
 			if (!allow_tls13) {
 				/* to prevent the server random indicate TLS1.3 support */
 				session->internals.flags |= INT_FLAG_NO_TLS13;
diff --git a/lib/auth/cert.h b/lib/auth/cert.h
index 4499320865..29b7220f7b 100644
--- a/lib/auth/cert.h
+++ b/lib/auth/cert.h
@@ -102,6 +102,10 @@ typedef struct gnutls_certificate_credentials_st {
 	/* OCSP */
 	gnutls_status_request_ocsp_func glob_ocsp_func;
 	void *glob_ocsp_func_ptr; /* corresponding OCSP response function */
+
+	/* This is only used by server to indicate whether this
+	 * credentials can be used for signing in TLS 1.3. */
+	bool tls13_ok;
 } certificate_credentials_st;
 
 /* This is the information we keep for the peer
diff --git a/lib/cert-cred.c b/lib/cert-cred.c
index d4b48f2069..c34d241fc1 100644
--- a/lib/cert-cred.c
+++ b/lib/cert-cred.c
@@ -74,6 +74,9 @@ _gnutls_certificate_credential_append_keypair(gnutls_certificate_credentials_t r
 	res->certs[res->ncerts].names = names;
 	res->certs[res->ncerts].pkey = key;
 
+	if (_gnutls13_sign_get_compatible_with_privkey(key))
+		res->tls13_ok = 1;
+
 	/* move RSA-PSS certificates before any RSA key.
 	 * Note that we cannot assume that any previous pointers
 	 * to sorted list are ok, due to the realloc in res->certs. */
diff --git a/tests/Makefile.am b/tests/Makefile.am
index eb65e94858..9643a93265 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -453,9 +453,11 @@ tls13_anti_replay_CPPFLAGS = $(AM_CPPFLAGS) \
 
 if ENABLE_PKCS11
 if !WINDOWS
-ctests += tls13/post-handshake-with-cert-pkcs11
+ctests += tls13/post-handshake-with-cert-pkcs11 pkcs11/tls-neg-pkcs11-no-key
 tls13_post_handshake_with_cert_pkcs11_DEPENDENCIES = libpkcs11mock2.la libutils.la
 tls13_post_handshake_with_cert_pkcs11_LDADD = $(LDADD) $(LIBDL)
+pkcs11_tls_neg_pkcs11_no_key_DEPENDENCIES = libpkcs11mock2.la libutils.la
+pkcs11_tls_neg_pkcs11_no_key_LDADD = $(LDADD) $(LIBDL)
 endif
 endif
 
diff --git a/tests/pkcs11/tls-neg-pkcs11-no-key.c b/tests/pkcs11/tls-neg-pkcs11-no-key.c
new file mode 100644
index 0000000000..af32c33ab9
--- /dev/null
+++ b/tests/pkcs11/tls-neg-pkcs11-no-key.c
@@ -0,0 +1,375 @@
+/*
+ * Copyright (C) 2017-2019 Red Hat, Inc.
+ *
+ * Author: 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>
+
+#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 "cert-common.h"
+#include "tls13/ext-parse.h"
+#include "pkcs11/softhsm.h"
+#include "utils.h"
+
+/* This program tests that TLS 1.3 is disabled 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 P11LIB "libpkcs11mock2.so"
+
+#define PIN "1234"
+
+#define CONFIG_NAME "softhsm-neg-no-key"
+#define CONFIG CONFIG_NAME".config"
+
+static
+int pin_func(void *userdata, int attempt, const char *url, const char *label,
+	     unsigned flags, char *pin, size_t pin_max)
+{
+	if (attempt == 0) {
+		strcpy(pin, PIN);
+		return 0;
+	}
+	return -1;
+}
+
+static void client(int fd)
+{
+	int ret;
+	gnutls_session_t session;
+	gnutls_certificate_credentials_t x509_cred;
+
+	global_init();
+
+	if (debug) {
+		gnutls_global_set_log_function(client_log_func);
+		gnutls_global_set_log_level(7);
+	}
+
+	ret = gnutls_certificate_allocate_credentials(&x509_cred);
+	if (ret < 0)
+		exit(1);
+
+	ret = gnutls_certificate_set_x509_trust_mem(x509_cred, &ca_cert, GNUTLS_X509_FMT_PEM);
+	if (ret < 0)
+		exit(1);
+
+	/* Initialize TLS session
+	 */
+	assert(gnutls_init(&session, GNUTLS_CLIENT)>=0);
+
+	gnutls_handshake_set_timeout(session, 20 * 1000);
+
+	ret = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+	if (ret < 0)
+		fail("cannot set credentials\n");
+
+	ret = gnutls_priority_set_direct(session, "NORMAL:-VERS-ALL:+VERS-TLS1.3:+VERS-TLS1.2", NULL);
+	if (ret < 0)
+		fail("cannot set priorities\n");
+
+
+	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 (ret != 0)
+		fail("handshake failed: %s\n", gnutls_strerror(ret));
+
+	if (debug)
+		success("client handshake completed\n");
+
+	if (gnutls_protocol_get_version(session) == GNUTLS_TLS1_2) {
+		if (debug)
+			success("session is downgraded to TLS 1.2\n");
+	} else
+		fail("session is NOT downgraded to TLS 1.2\n");
+
+	do {
+		ret = gnutls_bye(session, GNUTLS_SHUT_WR);
+	} while (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED);
+
+	close(fd);
+
+	gnutls_deinit(session);
+
+	gnutls_global_deinit();
+}
+
+static void server(int fd)
+{
+	int ret;
+	const char *lib;
+	gnutls_x509_crt_t crt;
+	gnutls_x509_privkey_t key;
+	gnutls_datum_t tmp;
+	gnutls_session_t session;
+	gnutls_certificate_credentials_t x509_cred;
+
+	/* this must be called once in the program
+	 */
+	global_init();
+
+	if (debug) {
+		gnutls_global_set_log_function(server_log_func);
+		gnutls_global_set_log_level(4711);
+	}
+
+	/* point to SoftHSM token that libpkcs11mock2.so internally uses */
+	setenv(SOFTHSM_ENV, CONFIG, 1);
+
+	gnutls_pkcs11_set_pin_function(pin_func, NULL);
+
+	lib = getenv("P11MOCKLIB2");
+	if (lib == NULL)
+		lib = P11LIB;
+
+	ret = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
+	if (ret != 0) {
+		fail("%d: %s\n", ret, gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret = gnutls_pkcs11_add_provider(lib, NULL);
+	if (ret != 0) {
+		fail("%d: %s\n", ret, gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret = gnutls_x509_crt_init(&crt);
+	if (ret < 0) {
+		fprintf(stderr,
+			"gnutls_x509_crt_init: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret = gnutls_x509_crt_import(crt, &server_ca3_cert, GNUTLS_X509_FMT_PEM);
+	if (ret < 0) {
+		fprintf(stderr,
+			"gnutls_x509_crt_import: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	if (debug) {
+		gnutls_x509_crt_print(crt, GNUTLS_CRT_PRINT_ONELINE, &tmp);
+
+		printf("\tCertificate: %.*s\n", tmp.size, tmp.data);
+		gnutls_free(tmp.data);
+	}
+
+	ret = gnutls_x509_privkey_init(&key);
+	if (ret < 0) {
+		fprintf(stderr,
+			"gnutls_x509_privkey_init: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret = gnutls_x509_privkey_import(key, &server_ca3_key, GNUTLS_X509_FMT_PEM);
+	if (ret < 0) {
+		fprintf(stderr,
+			"gnutls_x509_privkey_import: %s\n",
+			gnutls_strerror(ret));
+		exit(1);
+	}
+
+	/* initialize softhsm token */
+	ret = gnutls_pkcs11_token_init(SOFTHSM_URL, PIN, "test");
+	if (ret < 0) {
+		fail("gnutls_pkcs11_token_init: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret =
+	    gnutls_pkcs11_token_set_pin(SOFTHSM_URL, NULL, PIN,
+					GNUTLS_PIN_USER);
+	if (ret < 0) {
+		fail("gnutls_pkcs11_token_set_pin: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret = gnutls_pkcs11_copy_x509_crt(SOFTHSM_URL, crt, "cert",
+					  GNUTLS_PKCS11_OBJ_FLAG_MARK_PRIVATE |
+					  GNUTLS_PKCS11_OBJ_FLAG_LOGIN);
+	if (ret < 0) {
+		fail("gnutls_pkcs11_copy_x509_crt: %s\n", gnutls_strerror(ret));
+		exit(1);
+	}
+
+	ret =
+	    gnutls_pkcs11_copy_x509_privkey(SOFTHSM_URL, key, "cert",
+					    GNUTLS_KEY_DIGITAL_SIGNATURE |
+					    GNUTLS_KEY_KEY_ENCIPHERMENT,
+					    GNUTLS_PKCS11_OBJ_FLAG_MARK_PRIVATE
+					    |
+					    GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE
+					    | GNUTLS_PKCS11_OBJ_FLAG_LOGIN);
+	if (ret < 0) {
+		fail("gnutls_pkcs11_copy_x509_privkey: %s\n",
+		     gnutls_strerror(ret));
+		exit(1);
+	}
+
+	gnutls_x509_crt_deinit(crt);
+	gnutls_x509_privkey_deinit(key);
+
+	assert(gnutls_certificate_allocate_credentials(&x509_cred)>=0);
+
+	gnutls_init(&session, GNUTLS_SERVER);
+
+	gnutls_handshake_set_timeout(session, 20 * 1000);
+
+	assert(gnutls_certificate_set_x509_key_file(x509_cred,
+						    SOFTHSM_URL
+						    ";object=cert;object-type=cert",
+						    SOFTHSM_URL
+						    ";object=cert;object-type=private;pin-value="
+						    PIN,
+						    GNUTLS_X509_FMT_DER)>=0);
+
+	gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+
+	/* avoid calling all the priority functions, since the defaults
+	 * are adequate.
+	 */
+	gnutls_priority_set_direct(session, "NORMAL:-VERS-ALL:+VERS-TLS1.3:+VERS-TLS1.2", NULL);
+
+	gnutls_transport_set_int(session, fd);
+
+	do {
+		ret = gnutls_handshake(session);
+	} while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
+
+	if (ret != 0)
+		fail("handshake failed: %s\n", gnutls_strerror(ret));
+
+	if (debug)
+		success("server handshake completed\n");
+
+	if (gnutls_protocol_get_version(session) == GNUTLS_TLS1_2) {
+		if (debug)
+			success("session is downgraded to TLS 1.2\n");
+	} else
+		fail("session is NOT downgraded to TLS 1.2\n");
+
+	do {
+		ret = gnutls_bye(session, GNUTLS_SHUT_RDWR);
+	} while (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED);
+
+	close(fd);
+	gnutls_deinit(session);
+
+	gnutls_certificate_free_credentials(x509_cred);
+
+	gnutls_global_deinit();
+
+	if (debug)
+		success("server: client/server hello were verified\n");
+}
+
+void doit(void)
+{
+	const char *bin;
+	char buf[128];
+	int fd[2];
+	int ret;
+	pid_t child;
+	int status = 0;
+
+	/* check if softhsm module is loadable */
+	(void) softhsm_lib();
+
+	/* initialize SoftHSM token that libpkcs11mock2.so internally uses */
+	bin = softhsm_bin();
+
+	set_softhsm_conf(CONFIG);
+	snprintf(buf, sizeof(buf),
+		 "%s --init-token --slot 0 --label test --so-pin " PIN " --pin "
+		 PIN, bin);
+	system(buf);
+
+	signal(SIGCHLD, SIG_IGN);
+	signal(SIGPIPE, SIG_IGN);
+
+	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]);
+		kill(child, SIGTERM);
+		wait(&status);
+		check_wait_status(status);
+	} else {
+		close(fd[0]);
+		client(fd[1]);
+		exit(0);
+	}
+
+}
+#endif				/* _WIN32 */
diff --git a/tests/tls-neg-ext4-key.c b/tests/tls-neg-ext4-key.c
index 15172f9cc0..1adc65b93a 100644
--- a/tests/tls-neg-ext4-key.c
+++ b/tests/tls-neg-ext4-key.c
@@ -444,11 +444,21 @@ static const test_st tests[] = {
 	 .sig = GNUTLS_SIGN_RSA_PSS_SHA256,
 	 .exp_kx = GNUTLS_KX_ECDHE_RSA,
 	},
-	{.name = "tls1.3 rsa-pss cert, rsa-sign key", /* we expect the server to refuse negotiating */
+	{.name = "tls1.3 rsa-pss cert, rsa-sign key", /* we expect the server to attempt to downgrade to TLS 1.2, but it is not possible because it is not enabled */
 	 .pk = GNUTLS_PK_RSA,
 	 .prio = "NORMAL:-VERS-ALL:+VERS-TLS1.3",
 	 .cert = &server_ca3_rsa_pss_cert,
 	 .key = &server_ca3_rsa_pss_key,
+	 .sig = GNUTLS_SIGN_RSA_SHA256,
+	 .exp_kx = GNUTLS_KX_ECDHE_RSA,
+	 .exp_serv_err = GNUTLS_E_INSUFFICIENT_SECURITY
+	},
+	{.name = "tls1.3 rsa-pss cert, rsa-sign key, downgrade to tls1.2", /* we expect the server to downgrade to TLS 1.2 and refuse negotiating */
+	 .pk = GNUTLS_PK_RSA,
+	 .prio = "NORMAL:-VERS-ALL:+VERS-TLS1.3:+VERS-TLS1.2",
+	 .cert = &server_ca3_rsa_pss_cert,
+	 .key = &server_ca3_rsa_pss_key,
+	 .sig = GNUTLS_SIGN_RSA_SHA256,
 	 .exp_kx = GNUTLS_KX_ECDHE_RSA,
 	 .exp_serv_err = GNUTLS_E_NO_CIPHER_SUITES
 	},