tests: TLS fuzzing tool

Add test-tls program that can be used for fuzzing the internal TLS
client and server implementations. This tool can write client or server
messages into a file as an initialization step and for the fuzzing step,
that file (with potential modifications) can be used to replace the
internally generated message contents.

The TEST_FUZZ=y build parameter is used to make a special build where a
hardcoded random number generator and hardcoded timestamp are used to
force deterministic behavior for the TLS operations.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/crypto/Makefile

@@ -62,7 +62,9 @@ LIB_OBJS += crypto_internal-modexp.o
 LIB_OBJS += crypto_internal-rsa.o
 LIB_OBJS += tls_internal.o
 LIB_OBJS += fips_prf_internal.o
+ifndef TEST_FUZZ
 LIB_OBJS += random.o
+endif
 
 
 libcrypto.a: $(LIB_OBJS)

src/lib.rules

@@ -6,6 +6,11 @@ ifndef CFLAGS
 CFLAGS = -MMD -O2 -Wall -g
 endif
 
+ifdef TEST_FUZZ
+CFLAGS += -DCONFIG_NO_RANDOM_POOL
+CFLAGS += -DTEST_FUZZ
+endif
+
 CFLAGS += -I.. -I../utils
 
 

src/tls/tlsv1_client_write.c

@@ -72,6 +72,9 @@ u8 * tls_send_client_hello(struct tlsv1_client *conn, size_t *out_len)
 	*out_len = 0;
 
 	os_get_time(&now);
+#ifdef TEST_FUZZ
+	now.sec = 0xfffefdfc;
+#endif /* TEST_FUZZ */
 	WPA_PUT_BE32(conn->client_random, now.sec);
 	if (random_get_bytes(conn->client_random + 4, TLS_RANDOM_LEN - 4)) {
 		wpa_printf(MSG_ERROR, "TLSv1: Could not generate "

src/tls/tlsv1_server_write.c

@@ -53,6 +53,9 @@ static int tls_write_server_hello(struct tlsv1_server *conn,
 	pos += TLS_RECORD_HEADER_LEN;
 
 	os_get_time(&now);
+#ifdef TEST_FUZZ
+	now.sec = 0xfffefdfc;
+#endif /* TEST_FUZZ */
 	WPA_PUT_BE32(conn->server_random, now.sec);
 	if (random_get_bytes(conn->server_random + 4, TLS_RANDOM_LEN - 4)) {
 		wpa_printf(MSG_ERROR, "TLSv1: Could not generate "

src/utils/os_unix.c

@@ -250,6 +250,13 @@ void os_daemonize_terminate(const char *pid_file)
 
 int os_get_random(unsigned char *buf, size_t len)
 {
+#ifdef TEST_FUZZ
+	size_t i;
+
+	for (i = 0; i < len; i++)
+		buf[i] = i & 0xff;
+	return 0;
+#else /* TEST_FUZZ */
 	FILE *f;
 	size_t rc;
 
@@ -266,6 +273,7 @@ int os_get_random(unsigned char *buf, size_t len)
 	fclose(f);
 
 	return rc != len ? -1 : 0;
+#endif /* TEST_FUZZ */
 }
 
 

tests/Makefile

@@ -17,6 +17,11 @@ ifndef CFLAGS
 CFLAGS = -MMD -O2 -Wall -g
 endif
 
+ifdef TEST_FUZZ
+CFLAGS += -DCONFIG_NO_RANDOM_POOL
+CFLAGS += -DTEST_FUZZ
+endif
+
 CFLAGS += -I../src
 CFLAGS += -I../src/utils
 
@@ -77,6 +82,9 @@ test-sha1: test-sha1.o $(LIBS)
 test-sha256: test-sha256.o $(LIBS)
 	$(LDO) $(LDFLAGS) -o $@ $^ $(LLIBS)
 
+test-tls: test-tls.o $(LIBS)
+	$(LDO) $(LDFLAGS) -o $@ $< $(LLIBS)
+
 test-x509: test-x509.o $(LIBS)
 	$(LDO) $(LDFLAGS) -o $@ $< $(LLIBS)
 
@@ -99,6 +107,7 @@ clean:
 	$(MAKE) -C ../src clean
 	rm -f $(TESTS) *~ *.o *.d
 	rm -f test-https
+	rm -f test-tls
 	rm -f test_x509v3_nist.out.*
 	rm -f test_x509v3_nist2.out.*
 

tests/test-tls.c

@@ -0,0 +1,243 @@
+/*
+ * Testing tool for TLSv1 client/server routines
+ * Copyright (c) 2019, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "includes.h"
+
+#include "common.h"
+#include "crypto/tls.h"
+
+
+static void usage(void) {
+	wpa_printf(MSG_INFO,
+		   "usage: test-tls <server/client> <read/write> <file>");
+	exit(-1);
+}
+
+
+static void write_msg(FILE *f, struct wpabuf *msg)
+{
+	u8 len[2];
+
+	wpa_printf(MSG_DEBUG, "TEST: Write message to file (msg_len=%u)",
+		   (unsigned int) wpabuf_len(msg));
+	WPA_PUT_BE16(len, wpabuf_len(msg));
+	fwrite(len, 2, 1, f);
+	fwrite(wpabuf_head(msg), wpabuf_len(msg), 1, f);
+}
+
+
+static struct wpabuf * read_msg(FILE *f)
+{
+	u8 len[2];
+	u16 msg_len;
+	struct wpabuf *msg;
+
+	if (fread(len, 2, 1, f) != 1) {
+		wpa_printf(MSG_ERROR, "TEST-ERROR: Could not read msg len");
+		return NULL;
+	}
+	msg_len = WPA_GET_BE16(len);
+
+	msg = wpabuf_alloc(msg_len);
+	if (!msg)
+		return NULL;
+	if (msg_len > 0 &&
+	    fread(wpabuf_put(msg, msg_len), msg_len, 1, f) != 1) {
+		wpa_printf(MSG_ERROR, "TEST-ERROR: Truncated msg (msg_len=%u)",
+			   msg_len);
+		wpabuf_free(msg);
+		return NULL;
+	}
+	wpa_hexdump_buf(MSG_DEBUG, "TEST: Read message from file", msg);
+
+	return msg;
+}
+
+
+int main(int argc, char *argv[])
+{
+	struct tls_config conf;
+	void *tls_server, *tls_client;
+	struct tls_connection_params params;
+	struct tls_connection *conn_server = NULL, *conn_client = NULL;
+	int ret = -1;
+	struct wpabuf *in = NULL, *out = NULL, *appl;
+	enum { SERVER, CLIENT } test_peer;
+	enum { READ, WRITE } test_oper;
+	const char *file;
+	FILE *f;
+
+	wpa_debug_level = 0;
+	wpa_debug_show_keys = 1;
+
+	if (argc < 4)
+		usage();
+
+	if (os_strcmp(argv[1], "server") == 0)
+		test_peer = SERVER;
+	else if (os_strcmp(argv[1], "client") == 0)
+		test_peer = CLIENT;
+	else
+		usage();
+
+	if (os_strcmp(argv[2], "read") == 0)
+		test_oper = READ;
+	else if (os_strcmp(argv[2], "write") == 0)
+		test_oper = WRITE;
+	else
+		usage();
+
+	file = argv[3];
+
+	f = fopen(file, test_oper == READ ? "r" : "w");
+	if (!f)
+		return -1;
+
+	os_memset(&conf, 0, sizeof(conf));
+	tls_server = tls_init(&conf);
+	tls_client = tls_init(&conf);
+	if (!tls_server || !tls_client)
+		goto fail;
+
+	os_memset(&params, 0, sizeof(params));
+	params.ca_cert = "hwsim/auth_serv/ca.pem";
+	params.client_cert = "hwsim/auth_serv/server.pem";
+	params.private_key = "hwsim/auth_serv/server.key";
+	params.dh_file = "hwsim/auth_serv/dh.conf";
+
+	if (tls_global_set_params(tls_server, &params)) {
+		wpa_printf(MSG_ERROR, "Failed to set TLS parameters");
+		goto fail;
+	}
+
+	conn_server = tls_connection_init(tls_server);
+	conn_client = tls_connection_init(tls_client);
+	if (!conn_server || !conn_client)
+		goto fail;
+
+	in = NULL;
+	for (;;) {
+		appl = NULL;
+		if (test_peer == CLIENT && test_oper == READ)
+			out = read_msg(f);
+		else
+			out = tls_connection_handshake(tls_client, conn_client,
+						       in, &appl);
+		wpabuf_free(in);
+		in = NULL;
+		if (!out)
+			goto fail;
+		if (test_peer == CLIENT && test_oper == WRITE &&
+		    wpabuf_len(out) > 0)
+			write_msg(f, out);
+		if (!(test_peer == CLIENT && test_oper == READ) &&
+		    tls_connection_get_failed(tls_client, conn_client)) {
+			wpa_printf(MSG_ERROR, "TLS handshake failed");
+			goto fail;
+		}
+		if (((test_peer == CLIENT && test_oper == READ) ||
+		     tls_connection_established(tls_client, conn_client)) &&
+		    ((test_peer == SERVER && test_oper == READ) ||
+		     tls_connection_established(tls_server, conn_server)))
+			break;
+
+		appl = NULL;
+		if (test_peer == SERVER && test_oper == READ)
+			in = read_msg(f);
+		else
+			in = tls_connection_server_handshake(tls_server,
+							     conn_server,
+							     out, &appl);
+		wpabuf_free(out);
+		out = NULL;
+		if (!in)
+			goto fail;
+		if (test_peer == SERVER && test_oper == WRITE)
+			write_msg(f, in);
+		if (!(test_peer == SERVER && test_oper == READ) &&
+		    tls_connection_get_failed(tls_server, conn_server)) {
+			wpa_printf(MSG_ERROR, "TLS handshake failed");
+			goto fail;
+		}
+		if (((test_peer == CLIENT && test_oper == READ) ||
+		     tls_connection_established(tls_client, conn_client)) &&
+		    ((test_peer == SERVER && test_oper == READ) ||
+		     tls_connection_established(tls_server, conn_server)))
+			break;
+	}
+
+	wpabuf_free(in);
+	in = wpabuf_alloc(100);
+	if (!in)
+		goto fail;
+	wpabuf_put_str(in, "PING");
+	wpabuf_free(out);
+	if (test_peer == CLIENT && test_oper == READ)
+		out = read_msg(f);
+	else
+		out = tls_connection_encrypt(tls_client, conn_client, in);
+	wpabuf_free(in);
+	in = NULL;
+	if (!out)
+		goto fail;
+	if (test_peer == CLIENT && test_oper == WRITE)
+		write_msg(f, out);
+
+	if (!(test_peer == SERVER && test_oper == READ)) {
+		in = tls_connection_decrypt(tls_server, conn_server, out);
+		wpabuf_free(out);
+		out = NULL;
+		if (!in)
+			goto fail;
+		wpa_hexdump_buf(MSG_DEBUG, "Server decrypted ApplData", in);
+	}
+
+	wpabuf_free(in);
+	in = wpabuf_alloc(100);
+	if (!in)
+		goto fail;
+	wpabuf_put_str(in, "PONG");
+	wpabuf_free(out);
+	if (test_peer == SERVER && test_oper == READ)
+		out = read_msg(f);
+	else
+		out = tls_connection_encrypt(tls_server, conn_server, in);
+	wpabuf_free(in);
+	in = NULL;
+	if (!out)
+		goto fail;
+	if (test_peer == SERVER && test_oper == WRITE)
+		write_msg(f, out);
+
+	if (!(test_peer == CLIENT && test_oper == READ)) {
+		in = tls_connection_decrypt(tls_client, conn_client, out);
+		wpabuf_free(out);
+		out = NULL;
+		if (!in)
+			goto fail;
+		wpa_hexdump_buf(MSG_DEBUG, "Client decrypted ApplData", in);
+	}
+
+	ret = 0;
+fail:
+	if (tls_server) {
+		if (conn_server)
+			tls_connection_deinit(tls_server, conn_server);
+		tls_deinit(tls_server);
+	}
+	if (tls_client) {
+		if (conn_client)
+			tls_connection_deinit(tls_server, conn_client);
+		tls_deinit(tls_client);
+	}
+	wpabuf_free(in);
+	wpabuf_free(out);
+	fclose(f);
+
+	return ret;
+}