cert-cred: fix possible segfault when resetting cert retrieval function

Reset get_cert_callback3 callback to NULL if provided callback is NULL.
Otherwise after the certificate request call_legacy_cert_cb1 /
call_legacy_cert_cb2 will try to unconditionally call legacy_cert_cb1 /
legacy_cert_cb2 callback (set to NULL) leading to segfault.

Fixes: 9829ef9a3ca06d60472599df7c74ebb9a53f1fe2
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>

2 files changed, 131 insertions, 1 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index f6d89ab6b3..1081027c03 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -197,7 +197,8 @@ ctests += mini-record-2 simple gnutls_hmac_fast set_pkcs12_cred cert certuniquei
 	 x509sign-verify-error rng-op-nonce rng-op-random rng-op-key x509-dn-decode-compat \
 	 ip-check mini-x509-ipaddr trust-store base64-raw random-art dhex509self \
 	 dss-sig-val sign-pk-api tls-session-ext-override record-pad \
-	 tls13-server-kx-neg gnutls_ext_raw_parse_dtls key-export-pkcs8
+	 tls13-server-kx-neg gnutls_ext_raw_parse_dtls key-export-pkcs8 \
+	 null_retrieve_function
 
 if HAVE_SECCOMP_TESTS
 ctests += dtls-with-seccomp tls-with-seccomp dtls-client-with-seccomp tls-client-with-seccomp
diff --git a/tests/null_retrieve_function.c b/tests/null_retrieve_function.c
new file mode 100644
index 0000000000..4eaee869fc
--- /dev/null
+++ b/tests/null_retrieve_function.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2011-2012 Free Software Foundation, Inc.
+ * Copyright (C) 2018 Dmitry Eremin-Solenikov
+ *
+ * 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
+ */
+
+/* Parts copied from GnuTLS example programs. */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+#include <gnutls/abstract.h>
+
+#include "utils.h"
+#include "cert-common.h"
+
+/* Test for memory allocations in a non-matching key-cert pair loading.
+ *
+ */
+
+static int cert_cb1(gnutls_session_t session,
+		const gnutls_datum_t * req_ca_rdn,
+		int nreqs,
+		const gnutls_pk_algorithm_t * pk_algos,
+		int pk_algos_length,
+		gnutls_retr2_st *retr)
+{
+	return -1;
+}
+
+static int cert_cb2(gnutls_session_t session,
+		const gnutls_datum_t *req_ca_rdn,
+		int nreqs,
+		const gnutls_pk_algorithm_t *pk_algos,
+		int pk_algos_length,
+		gnutls_pcert_st** pcert,
+		unsigned int *pcert_length,
+		gnutls_privkey_t *privkey)
+{
+	return -1;
+}
+
+static int cert_cb3(gnutls_session_t session,
+		const struct gnutls_cert_retr_st *info,
+		gnutls_pcert_st **certs,
+		unsigned int *pcert_length,
+		gnutls_ocsp_data_st **ocsp,
+		unsigned int *ocsp_length,
+		gnutls_privkey_t *privkey,
+		unsigned int *flags)
+{
+	return -1;
+}
+
+
+static void tls_log_func(int level, const char *str)
+{
+	fprintf(stderr, "<%d>| %s", level, str);
+}
+
+void doit(void)
+{
+	gnutls_certificate_credentials_t x509_cred;
+	gnutls_certificate_credentials_t clicred;
+	int ret;
+
+	/* this must be called once in the program
+	 */
+	global_init();
+
+	gnutls_global_set_log_function(tls_log_func);
+	if (debug)
+		gnutls_global_set_log_level(6);
+
+	gnutls_certificate_allocate_credentials(&x509_cred);
+
+	ret = gnutls_certificate_set_x509_key_mem(x509_cred, &server_ca3_localhost_cert_chain,
+					    &server_ca3_key,
+					    GNUTLS_X509_FMT_PEM);
+	if (ret < 0) {
+		fail("error in error code\n");
+		exit(1);
+	}
+
+	gnutls_certificate_allocate_credentials(&clicred);
+	gnutls_certificate_set_retrieve_function(clicred, cert_cb1);
+	gnutls_certificate_set_retrieve_function(clicred, NULL);
+	_test_cli_serv(x509_cred, clicred, "NORMAL", "NORMAL", "localhost", NULL, NULL, NULL, 0, 1, GNUTLS_E_NO_CERTIFICATE_FOUND, -1);
+	gnutls_certificate_free_credentials(clicred);
+
+	gnutls_certificate_allocate_credentials(&clicred);
+	gnutls_certificate_set_retrieve_function2(clicred, cert_cb2);
+	gnutls_certificate_set_retrieve_function2(clicred, NULL);
+	_test_cli_serv(x509_cred, clicred, "NORMAL", "NORMAL", "localhost", NULL, NULL, NULL, 0, 1, GNUTLS_E_NO_CERTIFICATE_FOUND, -1);
+	gnutls_certificate_free_credentials(clicred);
+
+	gnutls_certificate_allocate_credentials(&clicred);
+	gnutls_certificate_set_retrieve_function3(clicred, cert_cb3);
+	gnutls_certificate_set_retrieve_function3(clicred, NULL);
+	_test_cli_serv(x509_cred, clicred, "NORMAL", "NORMAL", "localhost", NULL, NULL, NULL, 0, 1, GNUTLS_E_NO_CERTIFICATE_FOUND, -1);
+	gnutls_certificate_free_credentials(clicred);
+
+	gnutls_certificate_free_credentials(x509_cred);
+
+	gnutls_global_deinit();
+
+	if (debug)
+		success("success");
+}