library/dhm.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  *  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"

 /*
  * 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 );
 }

 /*
  * Verify sanity of parameter with regards to P
  *
  * Parameter should be: 2 <= public_param <= P - 2
  *
  * For more information on the attack, see:
  *  http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf
  *  http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643
  */
 static int dhm_check_range( const mpi *param, const mpi *P )
 {
     mpi L, U;
     int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA;

     mpi_init( &L ); mpi_init( &U );
     mpi_lset( &L, 2 );
     mpi_sub_int( &U, P, 2 );

     if( mpi_cmp_mpi( param, &L ) >= 0 &&
         mpi_cmp_mpi( param, &U ) <= 0 )
     {
         ret = 0;
     }

     mpi_free( &L ); mpi_free( &U );

     return( ret );
 }

 /*
  * Parse the ServerKeyExchange parameters
  */
 int dhm_read_params( dhm_context *ctx,
                      unsigned char **p,
                      const unsigned char *end )
 {
     int ret;

     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 );

     if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
         return( ret );

     ctx->len = mpi_size( &ctx->P );

     return( 0 );
 }

 /*
  * Setup and write the ServerKeyExchange parameters
  */
 int dhm_make_params( dhm_context *ctx, int x_size,
                      unsigned char *output, size_t *olen,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng )
 {
     int ret, count = 0;
     size_t n1, n2, n3;
     unsigned char *p;

     if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
         return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

     /*
      * Generate X as large as possible ( < P )
      */
     do
     {
         mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );

         while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
             mpi_shift_r( &ctx->X, 1 );

         if( count++ > 10 )
             return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
     }
     while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );

     /*
      * Calculate GX = G^X mod P
      */
     MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
                           &ctx->P , &ctx->RP ) );

     if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
         return( ret );

     /*
      * 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( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );

     return( 0 );
 }

 /*
  * Import the peer's public value G^Y
  */
 int dhm_read_public( dhm_context *ctx,
                      const unsigned char *input, size_t 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, size_t olen,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng )
 {
     int ret, count = 0;

     if( ctx == NULL || olen < 1 || olen > ctx->len )
         return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

     if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
         return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

     /*
      * generate X and calculate GX = G^X mod P
      */
     do
     {
         mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );

         while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
             mpi_shift_r( &ctx->X, 1 );

         if( count++ > 10 )
             return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED );
     }
     while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );

     MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
                           &ctx->P , &ctx->RP ) );

     if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
         return( ret );

     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, size_t *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 ) );

     if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
         return( ret );

     *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 ); mpi_free( &ctx->K ); mpi_free( &ctx->GY );
     mpi_free( &ctx->GX ); mpi_free( &ctx->X ); mpi_free( &ctx->G );
     mpi_free( &ctx->P );
 }

 #if defined(POLARSSL_SELF_TEST)

 /*
  * Checkup routine
  */
 int dhm_self_test( int verbose )
 {
     return( verbose++ );
 }

 #endif

 #endif
	/*
	* 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"

	/*
	* 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 );
	}

	/*
	* Verify sanity of parameter with regards to P
	*
	* Parameter should be: 2 <= public_param <= P - 2
	*
	* For more information on the attack, see:
	* http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf
	* http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643
	*/
	static int dhm_check_range( const mpi param, const mpi P )
	{
	mpi L, U;
	int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA;

	mpi_init( &L ); mpi_init( &U );
	mpi_lset( &L, 2 );
	mpi_sub_int( &U, P, 2 );

	if( mpi_cmp_mpi( param, &L ) >= 0 &&
	mpi_cmp_mpi( param, &U ) <= 0 )
	{
	ret = 0;
	}

	mpi_free( &L ); mpi_free( &U );

	return( ret );
	}

	/*
	* Parse the ServerKeyExchange parameters
	*/
	int dhm_read_params( dhm_context *ctx,
	unsigned char **p,
	const unsigned char *end )
	{
	int ret;

	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 );

	if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
	return( ret );

	ctx->len = mpi_size( &ctx->P );

	return( 0 );
	}

	/*
	* Setup and write the ServerKeyExchange parameters
	*/
	int dhm_make_params( dhm_context *ctx, int x_size,
	unsigned char output, size_t olen,
	int (f_rng)(void , unsigned char *, size_t),
	void *p_rng )
	{
	int ret, count = 0;
	size_t n1, n2, n3;
	unsigned char *p;

	if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
	return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

	/*
	* Generate X as large as possible ( < P )
	*/
	do
	{
	mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );

	while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
	mpi_shift_r( &ctx->X, 1 );

	if( count++ > 10 )
	return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
	}
	while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );

	/*
	* Calculate GX = G^X mod P
	*/
	MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
	&ctx->P , &ctx->RP ) );

	if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
	return( ret );

	/*
	* 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( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );

	return( 0 );
	}

	/*
	* Import the peer's public value G^Y
	*/
	int dhm_read_public( dhm_context *ctx,
	const unsigned char *input, size_t 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, size_t olen,
	int (f_rng)(void , unsigned char *, size_t),
	void *p_rng )
	{
	int ret, count = 0;

	if( ctx == NULL \|\| olen < 1 \|\| olen > ctx->len )
	return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

	if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
	return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );

	/*
	* generate X and calculate GX = G^X mod P
	*/
	do
	{
	mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );

	while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
	mpi_shift_r( &ctx->X, 1 );

	if( count++ > 10 )
	return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED );
	}
	while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );

	MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
	&ctx->P , &ctx->RP ) );

	if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
	return( ret );

	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, size_t 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 ) );

	if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
	return( ret );

	*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 ); mpi_free( &ctx->K ); mpi_free( &ctx->GY );
	mpi_free( &ctx->GX ); mpi_free( &ctx->X ); mpi_free( &ctx->G );
	mpi_free( &ctx->P );
	}

	#if defined(POLARSSL_SELF_TEST)

	/*
	* Checkup routine
	*/
	int dhm_self_test( int verbose )
	{
	return( verbose++ );
	}

	#endif

	#endif