strongswan-ext/fuzz/fuzz_tls.c

/*
 * Copyright (C) 2026 Arthur SC Chan
 *
 * Copyright (C) secunet Security Networks AG
 *
 * This program 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 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program 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.
 */

#include <library.h>
#include <tls.h>
#include <credentials/sets/mem_cred.h>

/**
 * ECDSA256 private key (same as used in test_socket.c)
 */
static chunk_t ecdsa256 = chunk_from_chars(
	0x30,0x77,0x02,0x01,0x01,0x04,0x20,0x2d,0x01,0x7e,0x5b,0x4a,0x7d,0x78,0xe9,0x23,
	0xeb,0xb2,0xac,0x4c,0xf1,0x28,0x3b,0xfa,0x1d,0xa9,0x08,0x5c,0xd0,0x60,0x2a,0xa6,
	0x54,0xd3,0x94,0xd4,0x05,0xa1,0x04,0xa0,0x0a,0x06,0x08,0x2a,0x86,0x48,0xce,0x3d,
	0x03,0x01,0x07,0xa1,0x44,0x03,0x42,0x00,0x04,0x15,0x9c,0xbe,0xdb,0x54,0xa6,0xe7,
	0x7f,0x76,0x05,0xa6,0x9d,0xf3,0x41,0x38,0x43,0x98,0xe9,0x0b,0x2b,0x8b,0x02,0xb4,
	0x04,0x9b,0x61,0x84,0x65,0x63,0x3b,0x08,0xb2,0x4b,0x1e,0xd0,0x32,0x20,0xe9,0xfc,
	0x62,0xa7,0xd0,0x71,0x9e,0xe9,0xf9,0x2d,0x91,0xb8,0xf2,0xa3,0x4d,0x8a,0x78,0xb2,
	0x0b,0xfb,0x59,0x7c,0x40,0xbd,0xaf,0xa2,0x07
);

/**
 * TLS certificate for ECDSA256 key
 * pki --self --in ecdsa256.key --dn "C=CH, O=strongSwan, CN=tls-fuzz-ecdsa" --san server.test
 */
static chunk_t ecdsa256_crt = chunk_from_chars(
	0x30,0x82,0x01,0x87,0x30,0x82,0x01,0x2C,0xA0,0x03,0x02,0x01,0x02,0x02,0x08,0x3D,
	0x6D,0x48,0xA3,0x1F,0x8A,0x62,0x3E,0x30,0x0A,0x06,0x08,0x2A,0x86,0x48,0xCE,0x3D,
	0x04,0x03,0x02,0x30,0x3B,0x31,0x0B,0x30,0x09,0x06,0x03,0x55,0x04,0x06,0x13,0x02,
	0x43,0x48,0x31,0x13,0x30,0x11,0x06,0x03,0x55,0x04,0x0A,0x13,0x0A,0x73,0x74,0x72,
	0x6F,0x6E,0x67,0x53,0x77,0x61,0x6E,0x31,0x17,0x30,0x15,0x06,0x03,0x55,0x04,0x03,
	0x13,0x0E,0x74,0x6C,0x73,0x2D,0x66,0x75,0x7A,0x7A,0x2D,0x65,0x63,0x64,0x73,0x61,
	0x30,0x1E,0x17,0x0D,0x32,0x36,0x30,0x35,0x32,0x39,0x30,0x38,0x33,0x38,0x33,0x36,
	0x5A,0x17,0x0D,0x32,0x39,0x30,0x35,0x32,0x38,0x30,0x38,0x33,0x38,0x33,0x36,0x5A,
	0x30,0x3B,0x31,0x0B,0x30,0x09,0x06,0x03,0x55,0x04,0x06,0x13,0x02,0x43,0x48,0x31,
	0x13,0x30,0x11,0x06,0x03,0x55,0x04,0x0A,0x13,0x0A,0x73,0x74,0x72,0x6F,0x6E,0x67,
	0x53,0x77,0x61,0x6E,0x31,0x17,0x30,0x15,0x06,0x03,0x55,0x04,0x03,0x13,0x0E,0x74,
	0x6C,0x73,0x2D,0x66,0x75,0x7A,0x7A,0x2D,0x65,0x63,0x64,0x73,0x61,0x30,0x59,0x30,
	0x13,0x06,0x07,0x2A,0x86,0x48,0xCE,0x3D,0x02,0x01,0x06,0x08,0x2A,0x86,0x48,0xCE,
	0x3D,0x03,0x01,0x07,0x03,0x42,0x00,0x04,0x15,0x9C,0xBE,0xDB,0x54,0xA6,0xE7,0x7F,
	0x76,0x05,0xA6,0x9D,0xF3,0x41,0x38,0x43,0x98,0xE9,0x0B,0x2B,0x8B,0x02,0xB4,0x04,
	0x9B,0x61,0x84,0x65,0x63,0x3B,0x08,0xB2,0x4B,0x1E,0xD0,0x32,0x20,0xE9,0xFC,0x62,
	0xA7,0xD0,0x71,0x9E,0xE9,0xF9,0x2D,0x91,0xB8,0xF2,0xA3,0x4D,0x8A,0x78,0xB2,0x0B,
	0xFB,0x59,0x7C,0x40,0xBD,0xAF,0xA2,0x07,0xA3,0x1A,0x30,0x18,0x30,0x16,0x06,0x03,
	0x55,0x1D,0x11,0x04,0x0F,0x30,0x0D,0x82,0x0B,0x73,0x65,0x72,0x76,0x65,0x72,0x2E,
	0x74,0x65,0x73,0x74,0x30,0x0A,0x06,0x08,0x2A,0x86,0x48,0xCE,0x3D,0x04,0x03,0x02,
	0x03,0x49,0x00,0x30,0x46,0x02,0x21,0x00,0xCB,0xD9,0x0D,0xC9,0x5C,0x68,0xF8,0x9D,
	0x69,0x69,0xB3,0x73,0x33,0xE7,0x29,0x08,0x63,0x7D,0xDB,0x12,0x8E,0xB5,0x5F,0xBF,
	0xEC,0xE7,0x81,0x95,0xC4,0x3F,0x7E,0xFA,0x02,0x21,0x00,0xB7,0x79,0xDA,0x0F,0xD1,
	0x42,0x9C,0xC2,0xD1,0x32,0x03,0x2D,0xE5,0x55,0x22,0xD8,0x09,0xAC,0xA9,0x1B,0xA1,
	0x0D,0x31,0xB8,0x24,0xEE,0xE3,0xE0,0xBF,0xBD,0x18,0xA5,
);

/**
 * Credential set
 */
static mem_cred_t *creds;

/**
 * Load the test certificate
 */
static void setup_cert()
{
	private_key_t *key;
	certificate_t *cert;

	creds = mem_cred_create();
	lib->credmgr->add_set(lib->credmgr, &creds->set);

	key = lib->creds->create(lib->creds, CRED_PRIVATE_KEY, KEY_ANY,
							 BUILD_BLOB, ecdsa256, BUILD_END);
	if (key)
	{
		creds->add_key(creds, key);
	}

	cert = lib->creds->create(lib->creds, CRED_CERTIFICATE, CERT_X509,
							  BUILD_BLOB, ecdsa256_crt, BUILD_END);
	if (cert)
	{
		creds->add_cert(creds, TRUE, cert);
	}
}

/**
 * Minimal TLS application stub for fuzzing
 */
typedef struct {
	tls_application_t public;
} fuzz_tls_application_t;

static status_t app_process(tls_application_t *this, bio_reader_t *reader)
{
	/* Consume application data without processing */
	return NEED_MORE;
}

static status_t app_build(tls_application_t *this, bio_writer_t *writer)
{
	/* No application data to send */
	return INVALID_STATE;
}

static void app_destroy(tls_application_t *this)
{
	free(this);
}

static tls_application_t *create_tls_application()
{
	fuzz_tls_application_t *app;

	INIT(app,
		.public = {
			.process = app_process,
			.build = app_build,
			.destroy = app_destroy,
		},
	);
	return &app->public;
}

int LLVMFuzzerInitialize(int *argc, char ***argv)
{
	dbg_default_set_level(-1);
	library_init(NULL, "fuzz_tls");
	if (!lib->plugins->load(lib->plugins, PLUGINS))
	{
		return 1;
	}
	setup_cert();
	return 0;
}

int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len)
{
	tls_t *tls;
	identification_t *server_id, *peer_id;
	tls_application_t *app;
	status_t status;
	char out[TLS_MAX_FRAGMENT_LEN + 2048];
	size_t outlen, msglen;
	bool is_server;

	/* Need one role byte plus minimum TLS record header (5 bytes) */
	if (len < 6)
	{
		return 0;
	}

	/* First byte selects role: input is then either a request (server) or
	 * response (client) */
	is_server = buf[0] & 1;
	buf++;
	len--;

	server_id = identification_create_from_string("server.test");
	peer_id = identification_create_from_string("peer.test");
	app = create_tls_application();

	tls = tls_create(is_server, server_id, peer_id, TLS_PURPOSE_GENERIC,
					 app, NULL, TLS_FLAG_ENCRYPTION_OPTIONAL);
	tls->set_version(tls, TLS_SUPPORTED_MIN, TLS_SUPPORTED_MAX);

	/* Client must emit ClientHello first so input is interpreted as the
	 * server's reply */
	if (!is_server)
	{
		do
		{
			outlen = sizeof(out);
			status = tls->build(tls, out, &outlen, &msglen);
		}
		while (status == NEED_MORE);
	}

	status = tls->process(tls, (void*)buf, len);

	/* Drive build() naturally based on process() status */
	if (status == NEED_MORE)
	{
		do
		{
			outlen = sizeof(out);
			status = tls->build(tls, out, &outlen, &msglen);
		}
		while (status == NEED_MORE);
	}

	tls->destroy(tls);
	server_id->destroy(server_id);
	peer_id->destroy(peer_id);
	return 0;
}