/*

 * Copyright (C) 2002-2015 Free Software Foundation, Inc.

 * Copyright (C) 2014-2015 Nikos Mavrogiannopoulos

 * Copyright (C) 2016-2017 Red Hat, Inc.

 *

 * Author: Nikos Mavrogiannopoulos

 *

 * This file is part of GnuTLS.

 *

 * The GnuTLS is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser 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/>

 *

 */

/* Functions for the TLS PRF handling.

 */

#include "gnutls_int.h"

#include "errors.h"

#include "handshake.h"

#include "secrets.h"

#include <num.h>

#include <state.h>

#include <algorithms.h>

/**

 * gnutls_prf_raw:

 * @session: is a #gnutls_session_t type.

 * @label_size: length of the @label variable.

 * @label: label used in PRF computation, typically a short string.

 * @seed_size: length of the @seed variable.

 * @seed: optional extra data to seed the PRF with.

 * @outsize: size of pre-allocated output buffer to hold the output.

 * @out: pre-allocated buffer to hold the generated data.

 *

 * Apply the TLS Pseudo-Random-Function (PRF) on the master secret

 * and the provided data.

 *

 * The @label variable usually contains a string denoting the purpose

 * for the generated data.  The @seed usually contains data such as the

 * client and server random, perhaps together with some additional

 * data that is added to guarantee uniqueness of the output for a

 * particular purpose.

 *

 * Because the output is not guaranteed to be unique for a particular

 * session unless @seed includes the client random and server random

 * fields (the PRF would output the same data on another connection

 * resumed from the first one), it is not recommended to use this

 * function directly.  The gnutls_prf() function seeds the PRF with the

 * client and server random fields directly, and is recommended if you

 * want to generate pseudo random data unique for each session.

 *

 * Note: This function will only operate under TLS versions prior to 1.3.

 * In TLS1.3 the use of PRF is replaced with HKDF and the generic

 * exporters like gnutls_prf_rfc5705() should be used instead. Under

 * TLS1.3 this function returns %GNUTLS_E_INVALID_REQUEST.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.

 **/

int

gnutls_prf_raw(gnutls_session_t session,

	       size_t label_size,

	       const char *label,

	       size_t seed_size, const char *seed, size_t outsize,

	       char *out)

{

	int ret;

	const version_entry_st *vers = get_version(session);

	if (vers && vers->tls13_sem)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	if (session->security_parameters.prf == NULL)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	ret = _gnutls_prf_raw(session->security_parameters.prf->id,

			  GNUTLS_MASTER_SIZE, session->security_parameters.master_secret,

			  label_size, label,

			  seed_size, (uint8_t *) seed,

			  outsize, out);

	return ret;

}

static int

_tls13_derive_exporter(const mac_entry_st *prf,

		       gnutls_session_t session,

		       size_t label_size, const char *label,

		       size_t context_size, const char *context,

		       size_t outsize, char *out,

		       bool early)

{

	uint8_t secret[MAX_HASH_SIZE];

	uint8_t digest[MAX_HASH_SIZE];

	unsigned digest_size = prf->output_size;

	int ret;

	ret = _tls13_derive_secret2(prf, label, label_size, NULL, 0,

				    session->key.proto.tls13.ap_expkey,

				    secret);

	if (ret < 0)

		return gnutls_assert_val(ret);

	ret = gnutls_hash_fast((gnutls_digest_algorithm_t)prf->id,

			       context, context_size, digest);

	if (ret < 0)

		return gnutls_assert_val(ret);

	return _tls13_expand_secret2(prf,

				     EXPORTER_LABEL, sizeof(EXPORTER_LABEL)-1,

				     digest, digest_size,

				     secret, outsize, out);

}

/**

 * gnutls_prf_rfc5705:

 * @session: is a #gnutls_session_t type.

 * @label_size: length of the @label variable.

 * @label: label used in PRF computation, typically a short string.

 * @context_size: length of the @extra variable.

 * @context: optional extra data to seed the PRF with.

 * @outsize: size of pre-allocated output buffer to hold the output.

 * @out: pre-allocated buffer to hold the generated data.

 *

 * Exports keying material from TLS/DTLS session to an application, as

 * specified in RFC5705.

 *

 * In the TLS versions prior to 1.3, it applies the TLS

 * Pseudo-Random-Function (PRF) on the master secret and the provided

 * data, seeded with the client and server random fields.

 *

 * In TLS 1.3, it applies HKDF on the exporter master secret derived

 * from the master secret.

 *

 * The @label variable usually contains a string denoting the purpose

 * for the generated data.

 *

 * The @context variable can be used to add more data to the seed, after

 * the random variables.  It can be used to make sure the

 * generated output is strongly connected to some additional data

 * (e.g., a string used in user authentication). 

 *

 * The output is placed in @out, which must be pre-allocated.

 *

 * Note that, to provide the RFC5705 context, the @context variable

 * must be non-null.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.

 *

 * Since: 3.4.4

 **/

int

gnutls_prf_rfc5705(gnutls_session_t session,

		   size_t label_size, const char *label,

		   size_t context_size, const char *context,

		   size_t outsize, char *out)

{

	const version_entry_st *vers = get_version(session);

	int ret;

	if (session->security_parameters.prf == NULL)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	if (vers && vers->tls13_sem) {

		ret = _tls13_derive_exporter(session->security_parameters.prf,

					     session,

					     label_size, label,

					     context_size, context,

					     outsize, out,

					     0);

	} else {

		char *pctx = NULL;

		if (context != NULL && context_size > 65535)  {

			gnutls_assert();

			return GNUTLS_E_INVALID_REQUEST;

		}

		if (context != NULL) {

			pctx = gnutls_malloc(context_size+2);

			if (!pctx) {

				gnutls_assert();

				return GNUTLS_E_MEMORY_ERROR;

			}

			memcpy(pctx+2, context, context_size);

			_gnutls_write_uint16(context_size, (void*)pctx);

			context_size += 2;

		}

		ret = gnutls_prf(session, label_size, label, 0,

				 context_size, pctx, outsize, out);

		gnutls_free(pctx);

	}

	return ret;

}

/**

 * gnutls_prf_early:

 * @session: is a #gnutls_session_t type.

 * @label_size: length of the @label variable.

 * @label: label used in PRF computation, typically a short string.

 * @context_size: length of the @extra variable.

 * @context: optional extra data to seed the PRF with.

 * @outsize: size of pre-allocated output buffer to hold the output.

 * @out: pre-allocated buffer to hold the generated data.

 *

 * This function is similar to gnutls_prf_rfc5705(), but only works in

 * TLS 1.3 or later to export early keying material.

 *

 * Note that the keying material is only available after the

 * ClientHello message is processed and before the application traffic

 * keys are established.  Therefore this function shall be called in a

 * handshake hook function for %GNUTLS_HANDSHAKE_CLIENT_HELLO.

 *

 * The @label variable usually contains a string denoting the purpose

 * for the generated data.

 *

 * The @context variable can be used to add more data to the seed, after

 * the random variables.  It can be used to make sure the

 * generated output is strongly connected to some additional data

 * (e.g., a string used in user authentication).

 *

 * The output is placed in @out, which must be pre-allocated.

 *

 * Note that, to provide the RFC5705 context, the @context variable

 * must be non-null.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.

 *

 * Since: 3.6.8

 **/

int

gnutls_prf_early(gnutls_session_t session,

		 size_t label_size, const char *label,

		 size_t context_size, const char *context,

		 size_t outsize, char *out)

{

	if (session->internals.initial_negotiation_completed ||

	    session->key.binders[0].prf == NULL)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	return _tls13_derive_exporter(session->key.binders[0].prf, session,

				      label_size, label,

				      context_size, context,

				      outsize, out,

				      1);

}

/**

 * gnutls_prf:

 * @session: is a #gnutls_session_t type.

 * @label_size: length of the @label variable.

 * @label: label used in PRF computation, typically a short string.

 * @server_random_first: non-zero if server random field should be first in seed

 * @extra_size: length of the @extra variable.

 * @extra: optional extra data to seed the PRF with.

 * @outsize: size of pre-allocated output buffer to hold the output.

 * @out: pre-allocated buffer to hold the generated data.

 *

 * Applies the TLS Pseudo-Random-Function (PRF) on the master secret

 * and the provided data, seeded with the client and server random fields.

 * For the key expansion specified in RFC5705 see gnutls_prf_rfc5705().

 *

 * The @label variable usually contains a string denoting the purpose

 * for the generated data.  The @server_random_first indicates whether

 * the client random field or the server random field should be first

 * in the seed.  Non-zero indicates that the server random field is first,

 * 0 that the client random field is first.

 *

 * The @extra variable can be used to add more data to the seed, after

 * the random variables.  It can be used to make sure the

 * generated output is strongly connected to some additional data

 * (e.g., a string used in user authentication).

 *

 * The output is placed in @out, which must be pre-allocated.

 *

 * Note: This function produces identical output with gnutls_prf_rfc5705()

 * when @server_random_first is set to 0 and @extra is %NULL. Under TLS1.3

 * this function will only operate when these conditions are true, or otherwise

 * return %GNUTLS_E_INVALID_REQUEST.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.

 **/

int

gnutls_prf(gnutls_session_t session,

	   size_t label_size,

	   const char *label,

	   int server_random_first,

	   size_t extra_size, const char *extra,

	   size_t outsize, char *out)

{

	int ret;

	uint8_t *seed;

	const version_entry_st *vers = get_version(session);

	size_t seedsize = 2 * GNUTLS_RANDOM_SIZE + extra_size;

	if (vers && vers->tls13_sem) {

		if (extra == NULL && server_random_first == 0)

			return gnutls_prf_rfc5705(session, label_size, label,

						  extra_size, extra, outsize, out);

		else

			return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	}

	if (session->security_parameters.prf == NULL)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	seed = gnutls_malloc(seedsize);

	if (!seed) {

		gnutls_assert();

		return GNUTLS_E_MEMORY_ERROR;

	}

	memcpy(seed, server_random_first ?

	       session->security_parameters.server_random :

	       session->security_parameters.client_random,

	       GNUTLS_RANDOM_SIZE);

	memcpy(seed + GNUTLS_RANDOM_SIZE,

	       server_random_first ? session->security_parameters.

	       client_random : session->security_parameters.server_random,

	       GNUTLS_RANDOM_SIZE);

	if (extra && extra_size) {

		memcpy(seed + 2 * GNUTLS_RANDOM_SIZE, extra, extra_size);

	}

	ret =

	    _gnutls_prf_raw(session->security_parameters.prf->id,

			GNUTLS_MASTER_SIZE, session->security_parameters.master_secret,

			label_size, label,

			seedsize, seed,

			outsize, out);

	gnutls_free(seed);

	return ret;

}