path: root/libextra/auth_srp.c

/*
 * Copyright (C) 2001,2002,2003 Nikos Mavroyanopoulos
 *
 * This file is part of GNUTLS.
 *
 * GNUTLS-EXTRA 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.
 *
 * GNUTLS-EXTRA 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include "gnutls_int.h"

#ifdef ENABLE_SRP

#include "gnutls_errors.h"
#include "auth_srp_passwd.h"
#include "gnutls_auth.h"
#include "gnutls_auth_int.h"
#include "gnutls_srp.h"
#include "debug.h"
#include "gnutls_num.h"
#include "auth_srp.h"
#include <gnutls_str.h>
#include <gnutls_datum.h>
#include <gnutls_alert.h>

int _gnutls_gen_srp_server_kx(gnutls_session, opaque **);
int _gnutls_gen_srp_client_kx(gnutls_session, opaque **);

int _gnutls_proc_srp_server_kx(gnutls_session, opaque *, size_t);
int _gnutls_proc_srp_client_kx(gnutls_session, opaque *, size_t);

const MOD_AUTH_STRUCT 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 state->key->b
#define B state->key->B
#define _a state->key->a
#define A state->key->A
#define N state->key->client_p
#define G state->key->client_g
#define V state->key->x
#define S state->key->KEY

/* 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 state, opaque ** data)
{
	int ret;
	uint8 *data_n, *data_s;
	uint8 *data_g;
	char *username;
	SRP_PWD_ENTRY *pwd_entry;
	SRP_SERVER_AUTH_INFO info;
	ssize_t data_size;
	size_t n_b, tmp_size;
	char buf[64];
	uint8 *data_b;

	if (state->security_parameters.extensions.srp_username[0] == 0) {
		/* The peer didn't send a valid SRP extension with the
		 * SRP username. The draft requires that we send an
		 * alert and start the handshake again.
		 */
		gnutls_assert();
		ret = gnutls_alert_send( state, GNUTLS_AL_WARNING,
			GNUTLS_A_MISSING_SRP_USERNAME);
		if (ret < 0) {
			gnutls_assert();
			return ret;
		}

		return GNUTLS_E_INT_HANDSHAKE_AGAIN;
	}

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

	info = _gnutls_get_auth_info( state);
	username = info->username;

	_gnutls_str_cpy( username, MAX_SRP_USERNAME, state->security_parameters.extensions.srp_username);

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

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

	/* copy from pwd_entry to local variables (actually in state) */
	if (_gnutls_mpi_scan( &G, pwd_entry->g.data, &pwd_entry->g.size) < 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	tmp_size = pwd_entry->n.size;
	if (_gnutls_mpi_scan( &N, pwd_entry->n.data, &tmp_size) < 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	tmp_size = pwd_entry->v.size;
	if (_gnutls_mpi_scan( &V, pwd_entry->v.data, &tmp_size) < 0) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	/* Calculate:  B = (3v + g^b) % N 
	 */
	B = _gnutls_calc_srp_B( &_b, G, N, V);
	if (B==NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	if (_gnutls_mpi_print( NULL, &n_b, B)!=0) {
		gnutls_assert();
		return GNUTLS_E_MPI_PRINT_FAILED;
	}


	/* Allocate size to hold the N, g, s, B 
	 */

	data_size = (pwd_entry->n.size + 2 + pwd_entry->g.size + 2 + 
		pwd_entry->salt.size + 1) + (n_b + 2);

	(*data) = gnutls_malloc( data_size);
	if ( (*data) == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	/* copy N (mod n) 
	 */
	data_n = *data;
	_gnutls_write_datum16( data_n, pwd_entry->n);


	/* copy G (generator) to data 
	 */
	data_g = &data_n[2 + pwd_entry->n.size];
	_gnutls_write_datum16( data_g, pwd_entry->g);


	/* copy the salt 
	 */
	data_s = &data_g[2 + pwd_entry->g.size];
	_gnutls_write_datum8( data_s, pwd_entry->salt);


	/* Copy the B value
	 */

	data_b = &data_s[1+pwd_entry->salt.size];
	if (_gnutls_mpi_print( &data_b[2], &n_b, B)!=0)
		return GNUTLS_E_MPI_PRINT_FAILED;
	_gnutls_write_uint16( n_b, data_b);

	_gnutls_hard_log( "INT: SRP B[%d]: %s\n", n_b, _gnutls_bin2hex(&data_b[2], n_b, buf, sizeof(buf)));

	_gnutls_srp_entry_free( pwd_entry);

	return data_size;
}

/* return A = g^a % N */
int _gnutls_gen_srp_client_kx(gnutls_session state, opaque ** data)
{
	size_t n_a;
	int ret;
	uint8 *data_a;
	char *username;
	char buf[64];
	char *password;
	const gnutls_srp_client_credentials cred =
	    _gnutls_get_cred(state->key, GNUTLS_CRD_SRP, NULL);

	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}
	
	username = cred->username;
	password = cred->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 */
	state->key->u = _gnutls_calc_srp_u(A, B);
	if ( state->key->u == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	_gnutls_dump_mpi( "SRP U: ", state->key->u);

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

	_gnutls_dump_mpi( "SRP B: ", B);
	
	_gnutls_mpi_release(&_b);
	_gnutls_mpi_release(&V);
	_gnutls_mpi_release(&state->key->u);
	_gnutls_mpi_release(&B);

	ret = _gnutls_generate_session_key( state->key);
	_gnutls_mpi_release(&S);

	if (ret < 0)
		return ret;

	if (_gnutls_mpi_print( NULL, &n_a, A)!=0) {
		gnutls_assert();
		return GNUTLS_E_MPI_PRINT_FAILED;
	}

	(*data) = gnutls_malloc(n_a + 2);
	if ( (*data) == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	/* copy A */
	data_a = (*data);
	if (_gnutls_mpi_print( &data_a[2], &n_a, A)!=0) {
		gnutls_free( *data);
		return GNUTLS_E_MPI_PRINT_FAILED;
	}
	_gnutls_hard_log( "INT: SRP A[%d]: %s\n", n_a, _gnutls_bin2hex(&data_a[2], n_a, buf, sizeof(buf)));

	_gnutls_mpi_release(&A);

	_gnutls_write_uint16( n_a, data_a);

	return n_a + 2;
}


/* just read A and put it to state */
int _gnutls_proc_srp_client_kx(gnutls_session state, opaque * data, size_t _data_size)
{
	size_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_scan(&A, &data[2], &_n_A) || A == NULL) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

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

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

	_gnutls_dump_mpi( "SRP U: ", state->key->u);

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

	_gnutls_dump_mpi( "SRP S: ", S);

	_gnutls_mpi_release(&A);
	_gnutls_mpi_release(&_b);
	_gnutls_mpi_release(&V);
	_gnutls_mpi_release(&state->key->u);
	_gnutls_mpi_release(&B);

	ret = _gnutls_generate_session_key( state->key);
	_gnutls_mpi_release( &S);

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

	return 0;
}


/* Checks if b%n==0 which is a fatal srp error.
 * Returns a proper error code in that case, and 0 when
 * all are ok.
 */
static int check_b_mod_n( GNUTLS_MPI b, GNUTLS_MPI n)
{
int ret;
GNUTLS_MPI r = _gnutls_mpi_alloc_like(b);

	_gnutls_mpi_mod( r, b, n);
	ret = _gnutls_mpi_cmp_ui(r, 0);
	
	_gnutls_mpi_release( &r);

	if (ret == 0) {
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}
	
	return 0;
}

/* Static parameters according to draft-ietf-tls-srp-05
 */
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;

const gnutls_datum gnutls_srp_1024_group_prime = {
	srp_params_1024, sizeof(srp_params_1024) };
const gnutls_datum gnutls_srp_1024_group_generator = {
	&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 gnutls_srp_1536_group_prime = {
	srp_params_1536, sizeof(srp_params_1536) };
const gnutls_datum gnutls_srp_1536_group_generator = {
	&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 gnutls_srp_2048_group_prime = {
	srp_params_2048, sizeof(srp_params_2048) };
const gnutls_datum gnutls_srp_2048_group_generator = {
	&srp_generator, sizeof(srp_generator) };


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

	if (n_g != 1 || g[0] != srp_generator) 
		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;
	}

	return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}

/* Check if N is a prime and G a generator of the
 * group.
 */
static int group_check_g_n( GNUTLS_MPI g, GNUTLS_MPI n) 
{
	if (gcry_prime_check( n, 0) != 0) {
		_gnutls_dump_mpi( "no prime N: ", n);
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}
	
	/* We should also check whether g is a generator,
	 * but this is not possible. We now only check if
	 * the generator is not too large.
	 */
	
	if (_gnutls_mpi_get_nbits(g) > 7) {
		gnutls_assert();
		return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
	}
	
	return 0;

}

/* receive the key exchange message ( n, g, s, B) 
 */
int _gnutls_proc_srp_server_kx(gnutls_session state, opaque * data, size_t _data_size)
{
	uint8 n_s;
	uint16 n_g, n_n, n_b;
	size_t _n_s, _n_g, _n_n, _n_b;
	const uint8 *data_n;
	const uint8 *data_g;
	const uint8 *data_s;
	const uint8 *data_b;
	int i, ret;
	opaque hd[SRP_MAX_HASH_SIZE];
	char *username, *password;
	ssize_t data_size = _data_size;

	const gnutls_srp_client_credentials cred =
	    _gnutls_get_cred(state->key, GNUTLS_CRD_SRP, NULL);

	if (cred == NULL) {
		gnutls_assert();
		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
	}
	
	username = cred->username;
	password = cred->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_s = n_s;
	_n_g = n_g;
	_n_n = n_n;
	_n_b = n_b;

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

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

	if (_gnutls_mpi_scan(&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_x509_log("Checking the SRP group parameters.\n");
		if ( (ret = group_check_g_n( G, N)) < 0) {
			gnutls_assert();
			return ret;
		}
	}

	/* Checks if b % n == 0
	 */
	if ( (ret = check_b_mod_n( B, N)) < 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, (opaque*)data_s, n_s, &_n_g, hd)) < 0) {
		gnutls_assert();
		return ret;
	}

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

	return 0;
}

#endif /* ENABLE_SRP */