/*
 * Copyright (C) 2001-2012 Free Software Foundation, 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 <http://www.gnu.org/licenses/>
 *
 */

#include "gnutls_int.h"

#ifdef ENABLE_SRP

#include "errors.h"
#include <auth/srp_passwd.h>
#include "auth.h"
#include "srp.h"
#include "num.h"
#include <auth/srp_kx.h>
#include <str.h>
#include <datum.h>
#include <ext/srp.h>

const mod_auth_st srp_auth_struct = {
	"SRP",
	NULL,
	NULL,
	_gnutls_gen_srp_server_kx,
	_gnutls_gen_srp_client_kx,
	NULL,
	NULL,

	NULL,
	NULL,			/* certificate */
	_gnutls_proc_srp_server_kx,
	_gnutls_proc_srp_client_kx,
	NULL,
	NULL
};


#define _b session->key.b
#define B session->key.B
#define _a session->key.a
#define A session->key.A
#define N session->key.srp_p
#define G session->key.srp_g
#define V session->key.x
#define S session->key.srp_key

/* Checks if a%n==0,+1,-1%n which is a fatal srp error.
 * Returns a proper error code in that case, and 0 when
 * all are ok.
 */
inline static int check_param_mod_n(bigint_t a, bigint_t n, int is_a)
{
	int ret, err = 0;
	bigint_t r;

	ret = _gnutls_mpi_init(&r);
	if (ret < 0)
		return gnutls_assert_val(ret);

	ret = _gnutls_mpi_modm(r, a, n);
	if (ret < 0) {
		_gnutls_mpi_release(&r);
		return gnutls_assert_val(ret);
	}

	ret = _gnutls_mpi_cmp_ui(r, 0);
	if (ret == 0)
		err = 1;

	if (is_a != 0) {
		ret = _gnutls_mpi_cmp_ui(r, 1);
		if (ret == 0)
			err = 1;

		ret = _gnutls_mpi_add_ui(r, r, 1);
		if (ret < 0) {
			_gnutls_mpi_release(&r);
			return gnutls_assert_val(ret);
		}
		
		ret = _gnutls_mpi_cmp(r, n);
		if (ret == 0)
			err = 1;
	}

	_gnutls_mpi_release(&r);

	if (err != 0) {
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}

	return 0;
}


/* Send the first key exchange message ( g, n, s) and append the verifier algorithm number 
 * Data is allocated by the caller, and should have data_size size.
 */
int
_gnutls_gen_srp_server_kx(gnutls_session_t session,
			  gnutls_buffer_st * data)
{
	int ret;
	char *username;
	SRP_PWD_ENTRY *pwd_entry;
	srp_server_auth_info_t info;
	size_t tmp_size;
	extension_priv_data_t epriv;
	srp_ext_st *priv;

	ret =
	    _gnutls_ext_get_session_data(session, GNUTLS_EXTENSION_SRP,
					 &epriv);
	if (ret < 0) {		/* peer didn't send a username */
		gnutls_assert();
		return GNUTLS_E_UNKNOWN_SRP_USERNAME;
	}
	priv = epriv;

	if ((ret =
	     _gnutls_auth_info_set(session, GNUTLS_CRD_SRP,
				   sizeof(srp_server_auth_info_st),
				   1)) < 0) {
		gnutls_assert();
		return ret;
	}

	info = _gnutls_get_auth_info(session, GNUTLS_CRD_SRP);
	if (info == NULL)
		return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

	username = info->username;

	_gnutls_str_cpy(username, MAX_USERNAME_SIZE, priv->username);

	ret = _gnutls_srp_pwd_read_entry(session, username, &pwd_entry);

	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	/* copy from pwd_entry to local variables (actually in session) */
	tmp_size = pwd_entry->g.size;
	if (_gnutls_mpi_init_scan_nz(&G, pwd_entry->g.data, tmp_size) < 0) {
		gnutls_assert();
		ret = GNUTLS_E_MPI_SCAN_FAILED;
		goto cleanup;
	}

	tmp_size = pwd_entry->n.size;
	if (_gnutls_mpi_init_scan_nz(&N, pwd_entry->n.data, tmp_size) < 0) {
		gnutls_assert();
		ret = GNUTLS_E_MPI_SCAN_FAILED;
		goto cleanup;
	}

	tmp_size = pwd_entry->v.size;
	if (_gnutls_mpi_init_scan_nz(&V, pwd_entry->v.data, tmp_size) < 0) {
		gnutls_assert();
		ret = GNUTLS_E_MPI_SCAN_FAILED;
		goto cleanup;
	}

	/* Calculate:  B = (k*v + g^b) % N 
	 */
	B = _gnutls_calc_srp_B(&_b, G, N, V);
	if (B == NULL) {
		gnutls_assert();
		ret = GNUTLS_E_MEMORY_ERROR;
		goto cleanup;
	}

	/* copy N (mod n) 
	 */
	ret =
	    _gnutls_buffer_append_data_prefix(data, 16, pwd_entry->n.data,
					      pwd_entry->n.size);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	/* copy G (generator) to data 
	 */
	ret =
	    _gnutls_buffer_append_data_prefix(data, 16, pwd_entry->g.data,
					      pwd_entry->g.size);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	/* copy the salt 
	 */
	ret =
	    _gnutls_buffer_append_data_prefix(data, 8,
					      pwd_entry->salt.data,
					      pwd_entry->salt.size);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	/* Copy the B value
	 */

	ret = _gnutls_buffer_append_mpi(data, 16, B, 0);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	_gnutls_mpi_log("SRP B: ", B);

	ret = data->length;

      cleanup:
	_gnutls_srp_entry_free(pwd_entry);
	return ret;
}

/* return A = g^a % N */
int
_gnutls_gen_srp_client_kx(gnutls_session_t session,
			  gnutls_buffer_st * data)
{
	int ret;
	char *username, *password;
	gnutls_srp_client_credentials_t cred;
	extension_priv_data_t epriv;
	srp_ext_st *priv;

	ret =
	    _gnutls_ext_get_session_data(session, GNUTLS_EXTENSION_SRP,
					 &epriv);
	if (ret < 0) {		/* peer didn't send a username */
		gnutls_assert();
		return GNUTLS_E_UNKNOWN_SRP_USERNAME;
	}
	priv = epriv;

	cred = (gnutls_srp_client_credentials_t)
	    _gnutls_get_cred(session, GNUTLS_CRD_SRP);

	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	if (priv->username == NULL) {
		username = cred->username;
		password = cred->password;
	} else {

		username = priv->username;
		password = priv->password;
	}

	if (username == NULL || password == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	/* calc A = g^a % N 
	 */
	if (G == NULL || N == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	A = _gnutls_calc_srp_A(&_a, G, N);
	if (A == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	/* Rest of SRP calculations 
	 */

	/* calculate u */
	session->key.u = _gnutls_calc_srp_u(A, B, N);
	if (session->key.u == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	_gnutls_mpi_log("SRP U: ", session->key.u);

	/* S = (B - g^x) ^ (a + u * x) % N */
	S = _gnutls_calc_srp_S2(B, G, session->key.x, _a, session->key.u,
				N);
	if (S == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	_gnutls_mpi_log("SRP B: ", B);

	zrelease_temp_mpi_key(&_b);
	zrelease_temp_mpi_key(&V);
	zrelease_temp_mpi_key(&session->key.u);
	zrelease_temp_mpi_key(&B);

	ret = _gnutls_mpi_dprint(session->key.srp_key, &session->key.key);
	zrelease_temp_mpi_key(&S);

	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	ret = _gnutls_buffer_append_mpi(data, 16, A, 0);
	if (ret < 0)
		return gnutls_assert_val(ret);

	_gnutls_mpi_log("SRP A: ", A);

	_gnutls_mpi_release(&A);

	return data->length;
}


/* just read A and put it to session */
int
_gnutls_proc_srp_client_kx(gnutls_session_t session, uint8_t * data,
			   size_t _data_size)
{
	ssize_t _n_A;
	ssize_t data_size = _data_size;
	int ret;

	DECR_LEN(data_size, 2);
	_n_A = _gnutls_read_uint16(&data[0]);

	DECR_LEN(data_size, _n_A);
	if (_gnutls_mpi_init_scan_nz(&A, &data[2], _n_A) || A == NULL) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	_gnutls_mpi_log("SRP A: ", A);
	_gnutls_mpi_log("SRP B: ", B);

	/* Checks if A % n == 0.
	 */
	if ((ret = check_param_mod_n(A, N, 1)) < 0) {
		gnutls_assert();
		return ret;
	}

	/* Start the SRP calculations.
	 * - Calculate u 
	 */
	session->key.u = _gnutls_calc_srp_u(A, B, N);
	if (session->key.u == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	_gnutls_mpi_log("SRP U: ", session->key.u);

	/* S = (A * v^u) ^ b % N 
	 */
	S = _gnutls_calc_srp_S1(A, _b, session->key.u, V, N);
	if (S == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	_gnutls_mpi_log("SRP S: ", S);

	_gnutls_mpi_release(&A);
	zrelease_temp_mpi_key(&_b);
	zrelease_temp_mpi_key(&V);
	zrelease_temp_mpi_key(&session->key.u);
	zrelease_temp_mpi_key(&B);

	ret = _gnutls_mpi_dprint(session->key.srp_key, &session->key.key);
	zrelease_temp_mpi_key(&S);

	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	return 0;
}



/* Static parameters according to draft-ietf-tls-srp-07
 * Note that if more parameters are added check_g_n()
 * and _gnutls_srp_entry_free() should be changed.
 */
static const unsigned char srp_params_1024[] = {
	0xEE, 0xAF, 0x0A, 0xB9, 0xAD, 0xB3, 0x8D, 0xD6,
	0x9C, 0x33, 0xF8, 0x0A, 0xFA, 0x8F, 0xC5, 0xE8,
	0x60, 0x72, 0x61, 0x87, 0x75, 0xFF, 0x3C, 0x0B,
	0x9E, 0xA2, 0x31, 0x4C, 0x9C, 0x25, 0x65, 0x76,
	0xD6, 0x74, 0xDF, 0x74, 0x96, 0xEA, 0x81, 0xD3,
	0x38, 0x3B, 0x48, 0x13, 0xD6, 0x92, 0xC6, 0xE0,
	0xE0, 0xD5, 0xD8, 0xE2, 0x50, 0xB9, 0x8B, 0xE4,
	0x8E, 0x49, 0x5C, 0x1D, 0x60, 0x89, 0xDA, 0xD1,
	0x5D, 0xC7, 0xD7, 0xB4, 0x61, 0x54, 0xD6, 0xB6,
	0xCE, 0x8E, 0xF4, 0xAD, 0x69, 0xB1, 0x5D, 0x49,
	0x82, 0x55, 0x9B, 0x29, 0x7B, 0xCF, 0x18, 0x85,
	0xC5, 0x29, 0xF5, 0x66, 0x66, 0x0E, 0x57, 0xEC,
	0x68, 0xED, 0xBC, 0x3C, 0x05, 0x72, 0x6C, 0xC0,
	0x2F, 0xD4, 0xCB, 0xF4, 0x97, 0x6E, 0xAA, 0x9A,
	0xFD, 0x51, 0x38, 0xFE, 0x83, 0x76, 0x43, 0x5B,
	0x9F, 0xC6, 0x1D, 0x2F, 0xC0, 0xEB, 0x06, 0xE3
};

static const unsigned char srp_generator = 0x02;
static const unsigned char srp3072_generator = 0x05;

const gnutls_datum_t gnutls_srp_1024_group_prime = {
	(void *) srp_params_1024, sizeof(srp_params_1024)
};

const gnutls_datum_t gnutls_srp_1024_group_generator = {
	(void *) &srp_generator, sizeof(srp_generator)
};

static const unsigned char srp_params_1536[] = {
	0x9D, 0xEF, 0x3C, 0xAF, 0xB9, 0x39, 0x27, 0x7A, 0xB1,
	0xF1, 0x2A, 0x86, 0x17, 0xA4, 0x7B, 0xBB, 0xDB, 0xA5,
	0x1D, 0xF4, 0x99, 0xAC, 0x4C, 0x80, 0xBE, 0xEE, 0xA9,
	0x61, 0x4B, 0x19, 0xCC, 0x4D, 0x5F, 0x4F, 0x5F, 0x55,
	0x6E, 0x27, 0xCB, 0xDE, 0x51, 0xC6, 0xA9, 0x4B, 0xE4,
	0x60, 0x7A, 0x29, 0x15, 0x58, 0x90, 0x3B, 0xA0, 0xD0,
	0xF8, 0x43, 0x80, 0xB6, 0x55, 0xBB, 0x9A, 0x22, 0xE8,
	0xDC, 0xDF, 0x02, 0x8A, 0x7C, 0xEC, 0x67, 0xF0, 0xD0,
	0x81, 0x34, 0xB1, 0xC8, 0xB9, 0x79, 0x89, 0x14, 0x9B,
	0x60, 0x9E, 0x0B, 0xE3, 0xBA, 0xB6, 0x3D, 0x47, 0x54,
	0x83, 0x81, 0xDB, 0xC5, 0xB1, 0xFC, 0x76, 0x4E, 0x3F,
	0x4B, 0x53, 0xDD, 0x9D, 0xA1, 0x15, 0x8B, 0xFD, 0x3E,
	0x2B, 0x9C, 0x8C, 0xF5, 0x6E, 0xDF, 0x01, 0x95, 0x39,
	0x34, 0x96, 0x27, 0xDB, 0x2F, 0xD5, 0x3D, 0x24, 0xB7,
	0xC4, 0x86, 0x65, 0x77, 0x2E, 0x43, 0x7D, 0x6C, 0x7F,
	0x8C, 0xE4, 0x42, 0x73, 0x4A, 0xF7, 0xCC, 0xB7, 0xAE,
	0x83, 0x7C, 0x26, 0x4A, 0xE3, 0xA9, 0xBE, 0xB8, 0x7F,
	0x8A, 0x2F, 0xE9, 0xB8, 0xB5, 0x29, 0x2E, 0x5A, 0x02,
	0x1F, 0xFF, 0x5E, 0x91, 0x47, 0x9E, 0x8C, 0xE7, 0xA2,
	0x8C, 0x24, 0x42, 0xC6, 0xF3, 0x15, 0x18, 0x0F, 0x93,
	0x49, 0x9A, 0x23, 0x4D, 0xCF, 0x76, 0xE3, 0xFE, 0xD1,
	0x35, 0xF9, 0xBB
};

const gnutls_datum_t gnutls_srp_1536_group_prime = {
	(void *) srp_params_1536, sizeof(srp_params_1536)
};

const gnutls_datum_t gnutls_srp_1536_group_generator = {
	(void *) &srp_generator, sizeof(srp_generator)
};

static const unsigned char srp_params_2048[] = {
	0xAC, 0x6B, 0xDB, 0x41, 0x32, 0x4A, 0x9A, 0x9B, 0xF1,
	0x66, 0xDE, 0x5E, 0x13, 0x89, 0x58, 0x2F, 0xAF, 0x72,
	0xB6, 0x65, 0x19, 0x87, 0xEE, 0x07, 0xFC, 0x31, 0x92,
	0x94, 0x3D, 0xB5, 0x60, 0x50, 0xA3, 0x73, 0x29, 0xCB,
	0xB4, 0xA0, 0x99, 0xED, 0x81, 0x93, 0xE0, 0x75, 0x77,
	0x67, 0xA1, 0x3D, 0xD5, 0x23, 0x12, 0xAB, 0x4B, 0x03,
	0x31, 0x0D, 0xCD, 0x7F, 0x48, 0xA9, 0xDA, 0x04, 0xFD,
	0x50, 0xE8, 0x08, 0x39, 0x69, 0xED, 0xB7, 0x67, 0xB0,
	0xCF, 0x60, 0x95, 0x17, 0x9A, 0x16, 0x3A, 0xB3, 0x66,
	0x1A, 0x05, 0xFB, 0xD5, 0xFA, 0xAA, 0xE8, 0x29, 0x18,
	0xA9, 0x96, 0x2F, 0x0B, 0x93, 0xB8, 0x55, 0xF9, 0x79,
	0x93, 0xEC, 0x97, 0x5E, 0xEA, 0xA8, 0x0D, 0x74, 0x0A,
	0xDB, 0xF4, 0xFF, 0x74, 0x73, 0x59, 0xD0, 0x41, 0xD5,
	0xC3, 0x3E, 0xA7, 0x1D, 0x28, 0x1E, 0x44, 0x6B, 0x14,
	0x77, 0x3B, 0xCA, 0x97, 0xB4, 0x3A, 0x23, 0xFB, 0x80,
	0x16, 0x76, 0xBD, 0x20, 0x7A, 0x43, 0x6C, 0x64, 0x81,
	0xF1, 0xD2, 0xB9, 0x07, 0x87, 0x17, 0x46, 0x1A, 0x5B,
	0x9D, 0x32, 0xE6, 0x88, 0xF8, 0x77, 0x48, 0x54, 0x45,
	0x23, 0xB5, 0x24, 0xB0, 0xD5, 0x7D, 0x5E, 0xA7, 0x7A,
	0x27, 0x75, 0xD2, 0xEC, 0xFA, 0x03, 0x2C, 0xFB, 0xDB,
	0xF5, 0x2F, 0xB3, 0x78, 0x61, 0x60, 0x27, 0x90, 0x04,
	0xE5, 0x7A, 0xE6, 0xAF, 0x87, 0x4E, 0x73, 0x03, 0xCE,
	0x53, 0x29, 0x9C, 0xCC, 0x04, 0x1C, 0x7B, 0xC3, 0x08,
	0xD8, 0x2A, 0x56, 0x98, 0xF3, 0xA8, 0xD0, 0xC3, 0x82,
	0x71, 0xAE, 0x35, 0xF8, 0xE9, 0xDB, 0xFB, 0xB6, 0x94,
	0xB5, 0xC8, 0x03, 0xD8, 0x9F, 0x7A, 0xE4, 0x35, 0xDE,
	0x23, 0x6D, 0x52, 0x5F, 0x54, 0x75, 0x9B, 0x65, 0xE3,
	0x72, 0xFC, 0xD6, 0x8E, 0xF2, 0x0F, 0xA7, 0x11, 0x1F,
	0x9E, 0x4A, 0xFF, 0x73
};

const gnutls_datum_t gnutls_srp_2048_group_prime = {
	(void *) srp_params_2048, sizeof(srp_params_2048)
};

const gnutls_datum_t gnutls_srp_2048_group_generator = {
	(void *) &srp_generator, sizeof(srp_generator)
};

static const unsigned char srp_params_3072[] = {
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9,
	0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6,
	0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E,
	0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
	0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E,
	0x34, 0x04, 0xDD, 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A,
	0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, 0xF2, 0x5F, 0x14,
	0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
	0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4,
	0x4C, 0x42, 0xE9, 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF,
	0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, 0xEE, 0x38, 0x6B,
	0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
	0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC,
	0xE4, 0x5B, 0x3D, 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63,
	0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36, 0x1C, 0x55, 0xD3,
	0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F,
	0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C,
	0x62, 0xF3, 0x56, 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5,
	0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, 0x67, 0x0C, 0x35,
	0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08,
	0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E,
	0x36, 0xCE, 0x3B, 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E,
	0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, 0xEC, 0x07, 0xA2,
	0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9,
	0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39,
	0x95, 0x49, 0x7C, 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2,
	0x26, 0x18, 0x98, 0xFA, 0x05, 0x10, 0x15, 0x72, 0x8E,
	0x5A, 0x8A, 0xAA, 0xC4, 0x2D, 0xAD, 0x33, 0x17, 0x0D,
	0x04, 0x50, 0x7A, 0x33, 0xA8, 0x55, 0x21, 0xAB, 0xDF,
	0x1C, 0xBA, 0x64, 0xEC, 0xFB, 0x85, 0x04, 0x58, 0xDB,
	0xEF, 0x0A, 0x8A, 0xEA, 0x71, 0x57, 0x5D, 0x06, 0x0C,
	0x7D, 0xB3, 0x97, 0x0F, 0x85, 0xA6, 0xE1, 0xE4, 0xC7,
	0xAB, 0xF5, 0xAE, 0x8C, 0xDB, 0x09, 0x33, 0xD7, 0x1E,
	0x8C, 0x94, 0xE0, 0x4A, 0x25, 0x61, 0x9D, 0xCE, 0xE3,
	0xD2, 0x26, 0x1A, 0xD2, 0xEE, 0x6B, 0xF1, 0x2F, 0xFA,
	0x06, 0xD9, 0x8A, 0x08, 0x64, 0xD8, 0x76, 0x02, 0x73,
	0x3E, 0xC8, 0x6A, 0x64, 0x52, 0x1F, 0x2B, 0x18, 0x17,
	0x7B, 0x20, 0x0C, 0xBB, 0xE1, 0x17, 0x57, 0x7A, 0x61,
	0x5D, 0x6C, 0x77, 0x09, 0x88, 0xC0, 0xBA, 0xD9, 0x46,
	0xE2, 0x08, 0xE2, 0x4F, 0xA0, 0x74, 0xE5, 0xAB, 0x31,
	0x43, 0xDB, 0x5B, 0xFC, 0xE0, 0xFD, 0x10, 0x8E, 0x4B,
	0x82, 0xD1, 0x20, 0xA9, 0x3A, 0xD2, 0xCA, 0xFF, 0xFF,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};

const gnutls_datum_t gnutls_srp_3072_group_generator = {
	(void *) &srp3072_generator, sizeof(srp3072_generator)
};

const gnutls_datum_t gnutls_srp_3072_group_prime = {
	(void *) srp_params_3072, sizeof(srp_params_3072)
};

static const unsigned char srp_params_4096[] = {
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA,
	    0xA2,
	0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C,
	    0xD1,
	0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE,
	    0xA6,
	0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04,
	    0xDD,
	0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A,
	    0x6D,
	0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2,
	    0x45,
	0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42,
	    0xE9,
	0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7,
	    0xED,
	0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24,
	    0x11,
	0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B,
	    0x3D,
	0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48,
	    0x36,
	0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF,
	    0x5F,
	0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3,
	    0x56,
	0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96,
	    0x6D,
	0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C,
	    0x08,
	0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE,
	    0x3B,
	0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83,
	    0xA2,
	0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52,
	    0xC9,
	0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49,
	    0x7C,
	0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05,
	    0x10,
	0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAA, 0xC4, 0x2D, 0xAD, 0x33, 0x17,
	    0x0D,
	0x04, 0x50, 0x7A, 0x33, 0xA8, 0x55, 0x21, 0xAB, 0xDF, 0x1C, 0xBA,
	    0x64,
	0xEC, 0xFB, 0x85, 0x04, 0x58, 0xDB, 0xEF, 0x0A, 0x8A, 0xEA, 0x71,
	    0x57,
	0x5D, 0x06, 0x0C, 0x7D, 0xB3, 0x97, 0x0F, 0x85, 0xA6, 0xE1, 0xE4,
	    0xC7,
	0xAB, 0xF5, 0xAE, 0x8C, 0xDB, 0x09, 0x33, 0xD7, 0x1E, 0x8C, 0x94,
	    0xE0,
	0x4A, 0x25, 0x61, 0x9D, 0xCE, 0xE3, 0xD2, 0x26, 0x1A, 0xD2, 0xEE,
	    0x6B,
	0xF1, 0x2F, 0xFA, 0x06, 0xD9, 0x8A, 0x08, 0x64, 0xD8, 0x76, 0x02,
	    0x73,
	0x3E, 0xC8, 0x6A, 0x64, 0x52, 0x1F, 0x2B, 0x18, 0x17, 0x7B, 0x20,
	    0x0C,
	0xBB, 0xE1, 0x17, 0x57, 0x7A, 0x61, 0x5D, 0x6C, 0x77, 0x09, 0x88,
	    0xC0,
	0xBA, 0xD9, 0x46, 0xE2, 0x08, 0xE2, 0x4F, 0xA0, 0x74, 0xE5, 0xAB,
	    0x31,
	0x43, 0xDB, 0x5B, 0xFC, 0xE0, 0xFD, 0x10, 0x8E, 0x4B, 0x82, 0xD1,
	    0x20,
	0xA9, 0x21, 0x08, 0x01, 0x1A, 0x72, 0x3C, 0x12, 0xA7, 0x87, 0xE6,
	    0xD7,
	0x88, 0x71, 0x9A, 0x10, 0xBD, 0xBA, 0x5B, 0x26, 0x99, 0xC3, 0x27,
	    0x18,
	0x6A, 0xF4, 0xE2, 0x3C, 0x1A, 0x94, 0x68, 0x34, 0xB6, 0x15, 0x0B,
	    0xDA,
	0x25, 0x83, 0xE9, 0xCA, 0x2A, 0xD4, 0x4C, 0xE8, 0xDB, 0xBB, 0xC2,
	    0xDB,
	0x04, 0xDE, 0x8E, 0xF9, 0x2E, 0x8E, 0xFC, 0x14, 0x1F, 0xBE, 0xCA,
	    0xA6,
	0x28, 0x7C, 0x59, 0x47, 0x4E, 0x6B, 0xC0, 0x5D, 0x99, 0xB2, 0x96,
	    0x4F,
	0xA0, 0x90, 0xC3, 0xA2, 0x23, 0x3B, 0xA1, 0x86, 0x51, 0x5B, 0xE7,
	    0xED,
	0x1F, 0x61, 0x29, 0x70, 0xCE, 0xE2, 0xD7, 0xAF, 0xB8, 0x1B, 0xDD,
	    0x76,
	0x21, 0x70, 0x48, 0x1C, 0xD0, 0x06, 0x91, 0x27, 0xD5, 0xB0, 0x5A,
	    0xA9,
	0x93, 0xB4, 0xEA, 0x98, 0x8D, 0x8F, 0xDD, 0xC1, 0x86, 0xFF, 0xB7,
	    0xDC,
	0x90, 0xA6, 0xC0, 0x8F, 0x4D, 0xF4, 0x35, 0xC9, 0x34, 0x06, 0x31,
	    0x99,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};

const gnutls_datum_t gnutls_srp_4096_group_generator = {
	(void *) &srp3072_generator, sizeof(srp3072_generator)
};

const gnutls_datum_t gnutls_srp_4096_group_prime = {
	(void *) srp_params_4096, sizeof(srp_params_4096)
};

/* Check if G and N are parameters from the SRP draft.
 */
static int
check_g_n(const uint8_t * g, size_t n_g, const uint8_t * n, size_t n_n)
{

	if ((n_n == sizeof(srp_params_3072) &&
	     memcmp(srp_params_3072, n, n_n) == 0) ||
	    (n_n == sizeof(srp_params_4096) &&
	     memcmp(srp_params_4096, n, n_n) == 0)) {
		if (n_g != 1 || g[0] != srp3072_generator) {
			return
			    gnutls_assert_val
			    (GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
		}
		return 0;
	}

	if (n_g != 1 || g[0] != srp_generator) {
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}

	if (n_n == sizeof(srp_params_1024) &&
	    memcmp(srp_params_1024, n, n_n) == 0) {
		return 0;
	}

	if (n_n == sizeof(srp_params_1536) &&
	    memcmp(srp_params_1536, n, n_n) == 0) {
		return 0;
	}

	if (n_n == sizeof(srp_params_2048) &&
	    memcmp(srp_params_2048, n, n_n) == 0) {
		return 0;
	}

	gnutls_assert();
	return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}

/* Check if N is a prime and G a generator of the
 * group. This check is only done if N is big enough.
 * Otherwise only the included parameters must be used.
 */
static int
group_check_g_n(gnutls_session_t session, bigint_t g, bigint_t n)
{
	bigint_t q = NULL, two = NULL, w = NULL;
	int ret;

	if (_gnutls_mpi_get_nbits(n) < (session->internals.srp_prime_bits
					? session->internals.srp_prime_bits
					: 2048)) {
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}

	/* N must be of the form N=2q+1
	 * where q is also a prime.
	 */
	if (_gnutls_prime_check(n) != 0) {
		_gnutls_mpi_log("no prime N: ", n);
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}

	ret = _gnutls_mpi_init_multi(&two, &q, &w, NULL);
	if (ret < 0) {
		gnutls_assert();
		return ret;
	}

	/* q = n-1 
	 */
	ret = _gnutls_mpi_sub_ui(q, n, 1);
	if (ret < 0) {
		gnutls_assert();
		goto error;
	}

	/* q = q/2, remember that q is divisible by 2 (prime - 1)
	 */
	ret = _gnutls_mpi_set_ui(two, 2);
	if (ret < 0) {
		gnutls_assert();
		goto error;
	}

	ret = _gnutls_mpi_div(q, q, two);
	if (ret < 0) {
		gnutls_assert();
		goto error;
	}

	if (_gnutls_prime_check(q) != 0) {
		/* N was not on the form N=2q+1, where q = prime
		 */
		_gnutls_mpi_log("no prime Q: ", q);
		gnutls_assert();
		ret = GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
		goto error;
	}

	/* We also check whether g is a generator,
	 */

	/* check if g < q < N
	 */
	if (_gnutls_mpi_cmp(g, q) >= 0) {
		gnutls_assert();
		ret = GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
		goto error;
	}

	/* check if g^q mod N == N-1
	 * w = g^q mod N
	 */
	ret = _gnutls_mpi_powm(w, g, q, n);
	if (ret < 0) {
		gnutls_assert();
		goto error;
	}

	/* w++
	 */
	ret = _gnutls_mpi_add_ui(w, w, 1);
	if (ret < 0) {
		gnutls_assert();
		goto error;
	}

	if (_gnutls_mpi_cmp(w, n) != 0) {
		gnutls_assert();
		ret = GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
		goto error;
	}

	ret = 0;

      error:
	_gnutls_mpi_release(&q);
	_gnutls_mpi_release(&two);
	_gnutls_mpi_release(&w);

	return ret;

}

/* receive the key exchange message ( n, g, s, B) 
 */
int
_gnutls_proc_srp_server_kx(gnutls_session_t session, uint8_t * data,
			   size_t _data_size)
{
	uint8_t n_s;
	uint16_t n_g, n_n, n_b;
	size_t _n_g, _n_n, _n_b;
	const uint8_t *data_n;
	const uint8_t *data_g;
	const uint8_t *data_s;
	const uint8_t *data_b;
	int i, ret;
	uint8_t hd[SRP_MAX_HASH_SIZE];
	char *username, *password;
	ssize_t data_size = _data_size;
	gnutls_srp_client_credentials_t cred;
	extension_priv_data_t epriv;
	srp_ext_st *priv;

	ret =
	    _gnutls_ext_get_session_data(session, GNUTLS_EXTENSION_SRP,
					 &epriv);
	if (ret < 0) {
		gnutls_assert();
		return GNUTLS_E_UNKNOWN_SRP_USERNAME;
	}
	priv = epriv;

	cred = (gnutls_srp_client_credentials_t)
	    _gnutls_get_cred(session, GNUTLS_CRD_SRP);

	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	if (priv->username == NULL) {
		username = cred->username;
		password = cred->password;
	} else {
		username = priv->username;
		password = priv->password;
	}

	if (username == NULL || password == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}

	i = 0;

	/* Read N 
	 */
	DECR_LEN(data_size, 2);
	n_n = _gnutls_read_uint16(&data[i]);
	i += 2;

	DECR_LEN(data_size, n_n);
	data_n = &data[i];
	i += n_n;

	/* Read G 
	 */
	DECR_LEN(data_size, 2);
	n_g = _gnutls_read_uint16(&data[i]);
	i += 2;

	DECR_LEN(data_size, n_g);
	data_g = &data[i];
	i += n_g;

	/* Read salt 
	 */
	DECR_LEN(data_size, 1);
	n_s = data[i];
	i += 1;

	DECR_LEN(data_size, n_s);
	data_s = &data[i];
	i += n_s;

	/* Read B 
	 */
	DECR_LEN(data_size, 2);
	n_b = _gnutls_read_uint16(&data[i]);
	i += 2;

	DECR_LEN(data_size, n_b);
	data_b = &data[i];
	i += n_b;

	_n_g = n_g;
	_n_n = n_n;
	_n_b = n_b;

	if (_gnutls_mpi_init_scan_nz(&N, data_n, _n_n) != 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	if (_gnutls_mpi_init_scan_nz(&G, data_g, _n_g) != 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	if (_gnutls_mpi_init_scan_nz(&B, data_b, _n_b) != 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}


	/* Check if the g and n are from the SRP
	 * draft. Otherwise check if N is a prime and G
	 * a generator.
	 */
	if ((ret = check_g_n(data_g, _n_g, data_n, _n_n)) < 0) {
		_gnutls_audit_log(session,
				  "SRP group parameters are not in the white list. Checking validity.\n");
		if ((ret = group_check_g_n(session, G, N)) < 0) {
			gnutls_assert();
			return ret;
		}
	}

	/* Checks if b % n == 0
	 */
	if ((ret = check_param_mod_n(B, N, 0)) < 0) {
		gnutls_assert();
		return ret;
	}


	/* generate x = SHA(s | SHA(U | ":" | p))
	 * (or the equivalent using bcrypt)
	 */
	if ((ret =
	     _gnutls_calc_srp_x(username, password, (uint8_t *) data_s,
				n_s, &_n_g, hd)) < 0) {
		gnutls_assert();
		return ret;
	}

	if (_gnutls_mpi_init_scan_nz(&session->key.x, hd, _n_g) != 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}


	return i;		/* return the processed data
				 * needed in auth_srp_rsa.
				 */
}

#endif				/* ENABLE_SRP */
