Show source - Diffie-Hellman source code
include/polarssl/dhm.h
/**
* \file dhm.h
*
* Copyright (C) 2006-2010, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* 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.
*
* 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.
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef POLARSSL_DHM_H
#define POLARSSL_DHM_H
#include "polarssl/bignum.h"
#define POLARSSL_ERR_DHM_BAD_INPUT_DATA 0x0480
#define POLARSSL_ERR_DHM_READ_PARAMS_FAILED 0x0490
#define POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED 0x04A0
#define POLARSSL_ERR_DHM_READ_PUBLIC_FAILED 0x04B0
#define POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED 0x04C0
#define POLARSSL_ERR_DHM_CALC_SECRET_FAILED 0x04D0
typedef struct
{
int len; /*!< size(P) in chars */
mpi P; /*!< prime modulus */
mpi G; /*!< generator */
mpi X; /*!< secret value */
mpi GX; /*!< self = G^X mod P */
mpi GY; /*!< peer = G^Y mod P */
mpi K; /*!< key = GY^X mod P */
mpi RP; /*!< cached R^2 mod P */
}
dhm_context;
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief Parse the ServerKeyExchange parameters
*
* \param ctx DHM context
* \param p &(start of input buffer)
* \param end end of buffer
*
* \return 0 if successful, or an POLARSSL_ERR_DHM_XXX error code
*/
int dhm_read_params( dhm_context *ctx,
unsigned char **p,
const unsigned char *end );
/**
* \brief Setup and write the ServerKeyExchange parameters
*
* \param ctx DHM context
* \param x_size private value size in bytes
* \param output destination buffer
* \param olen number of chars written
* \param f_rng RNG function
* \param p_rng RNG parameter
*
* \note This function assumes that ctx->P and ctx->G
* have already been properly set (for example
* using mpi_read_string or mpi_read_binary).
*
* \return 0 if successful, or an POLARSSL_ERR_DHM_XXX error code
*/
int dhm_make_params( dhm_context *ctx, int x_size,
unsigned char *output, int *olen,
int (*f_rng)(void *), void *p_rng );
/**
* \brief Import the peer's public value G^Y
*
* \param ctx DHM context
* \param input input buffer
* \param ilen size of buffer
*
* \return 0 if successful, or an POLARSSL_ERR_DHM_XXX error code
*/
int dhm_read_public( dhm_context *ctx,
const unsigned char *input, int ilen );
/**
* \brief Create own private value X and export G^X
*
* \param ctx DHM context
* \param x_size private value size in bits
* \param output destination buffer
* \param olen must be equal to ctx->P.len
* \param f_rng RNG function
* \param p_rng RNG parameter
*
* \return 0 if successful, or an POLARSSL_ERR_DHM_XXX error code
*/
int dhm_make_public( dhm_context *ctx, int s_size,
unsigned char *output, int olen,
int (*f_rng)(void *), void *p_rng );
/**
* \brief Derive and export the shared secret (G^Y)^X mod P
*
* \param ctx DHM context
* \param output destination buffer
* \param olen number of chars written
*
* \return 0 if successful, or an POLARSSL_ERR_DHM_XXX error code
*/
int dhm_calc_secret( dhm_context *ctx,
unsigned char *output, int *olen );
/*
* \brief Free the components of a DHM key
*/
void dhm_free( dhm_context *ctx );
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if the test failed
*/
int dhm_self_test( int verbose );
#ifdef __cplusplus
}
#endif
#endif
library/dhm.c
/*
* Diffie-Hellman-Merkle key exchange
*
* Copyright (C) 2006-2010, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* 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.
*
* 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.
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*
* Reference:
*
* http://www.cacr.math.uwaterloo.ca/hac/ (chapter 12)
*/
#include "polarssl/config.h"
#if defined(POLARSSL_DHM_C)
#include "polarssl/dhm.h"
#include <string.h>
/*
* helper to validate the mpi size and import it
*/
static int dhm_read_bignum( mpi *X,
unsigned char **p,
const unsigned char *end )
{
int ret, n;
if( end - *p < 2 )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
n = ( (*p)[0] << 8 ) | (*p)[1];
(*p) += 2;
if( (int)( end - *p ) < n )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mpi_read_binary( X, *p, n ) ) != 0 )
return( POLARSSL_ERR_DHM_READ_PARAMS_FAILED | ret );
(*p) += n;
return( 0 );
}
/*
* Parse the ServerKeyExchange parameters
*/
int dhm_read_params( dhm_context *ctx,
unsigned char **p,
const unsigned char *end )
{
int ret, n;
memset( ctx, 0, sizeof( dhm_context ) );
if( ( ret = dhm_read_bignum( &ctx->P, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->G, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->GY, p, end ) ) != 0 )
return( ret );
ctx->len = mpi_size( &ctx->P );
if( end - *p < 2 )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
n = ( (*p)[0] << 8 ) | (*p)[1];
(*p) += 2;
if( end != *p + n )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
return( 0 );
}
/*
* Setup and write the ServerKeyExchange parameters
*/
int dhm_make_params( dhm_context *ctx, int x_size,
unsigned char *output, int *olen,
int (*f_rng)(void *), void *p_rng )
{
int i, ret, n, n1, n2, n3;
unsigned char *p;
/*
* Generate X as large as possible ( < P )
*/
n = x_size / sizeof( t_int );
MPI_CHK( mpi_grow( &ctx->X, n ) );
MPI_CHK( mpi_lset( &ctx->X, 0 ) );
p = (unsigned char *) ctx->X.p;
for( i = 0; i < x_size - 1; i++ )
*p++ = (unsigned char) f_rng( p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
/*
* Calculate GX = G^X mod P
*/
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
/*
* export P, G, GX
*/
#define DHM_MPI_EXPORT(X,n) \
MPI_CHK( mpi_write_binary( X, p + 2, n ) ); \
*p++ = (unsigned char)( n >> 8 ); \
*p++ = (unsigned char)( n ); p += n;
n1 = mpi_size( &ctx->P );
n2 = mpi_size( &ctx->G );
n3 = mpi_size( &ctx->GX );
p = output;
DHM_MPI_EXPORT( &ctx->P , n1 );
DHM_MPI_EXPORT( &ctx->G , n2 );
DHM_MPI_EXPORT( &ctx->GX, n3 );
*olen = p - output;
ctx->len = n1;
cleanup:
if( ret != 0 )
return( ret | POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
return( 0 );
}
/*
* Import the peer's public value G^Y
*/
int dhm_read_public( dhm_context *ctx,
const unsigned char *input, int ilen )
{
int ret;
if( ctx == NULL || ilen < 1 || ilen > ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
return( POLARSSL_ERR_DHM_READ_PUBLIC_FAILED | ret );
return( 0 );
}
/*
* Create own private value X and export G^X
*/
int dhm_make_public( dhm_context *ctx, int x_size,
unsigned char *output, int olen,
int (*f_rng)(void *), void *p_rng )
{
int ret, i, n;
unsigned char *p;
if( ctx == NULL || olen < 1 || olen > ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
/*
* generate X and calculate GX = G^X mod P
*/
n = x_size / sizeof( t_int );
MPI_CHK( mpi_grow( &ctx->X, n ) );
MPI_CHK( mpi_lset( &ctx->X, 0 ) );
n = x_size - 1;
p = (unsigned char *) ctx->X.p;
for( i = 0; i < n; i++ )
*p++ = (unsigned char) f_rng( p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
MPI_CHK( mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED | ret );
return( 0 );
}
/*
* Derive and export the shared secret (G^Y)^X mod P
*/
int dhm_calc_secret( dhm_context *ctx,
unsigned char *output, int *olen )
{
int ret;
if( ctx == NULL || *olen < ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
MPI_CHK( mpi_exp_mod( &ctx->K, &ctx->GY, &ctx->X,
&ctx->P, &ctx->RP ) );
*olen = mpi_size( &ctx->K );
MPI_CHK( mpi_write_binary( &ctx->K, output, *olen ) );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_CALC_SECRET_FAILED | ret );
return( 0 );
}
/*
* Free the components of a DHM key
*/
void dhm_free( dhm_context *ctx )
{
mpi_free( &ctx->RP, &ctx->K, &ctx->GY,
&ctx->GX, &ctx->X, &ctx->G,
&ctx->P, NULL );
}
#if defined(POLARSSL_SELF_TEST)
/*
* Checkup routine
*/
int dhm_self_test( int verbose )
{
return( verbose++ );
}
#endif
#endif