577 lines
14 KiB
C
577 lines
14 KiB
C
/*
|
||
* Diffie-Hellman-Merkle key exchange
|
||
*
|
||
* Copyright (C) 2006-2014, 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"
|
||
|
||
#if defined(POLARSSL_PEM_PARSE_C)
|
||
#include "polarssl/pem.h"
|
||
#endif
|
||
|
||
#if defined(POLARSSL_ASN1_PARSE_C)
|
||
#include "polarssl/asn1.h"
|
||
#endif
|
||
|
||
#if defined(POLARSSL_PLATFORM_C)
|
||
#include "polarssl/platform.h"
|
||
#else
|
||
#include <stdlib.h>
|
||
#define polarssl_printf printf
|
||
#define polarssl_malloc malloc
|
||
#define polarssl_free free
|
||
#endif
|
||
|
||
/*
|
||
* 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;
|
||
|
||
dhm_free( ctx );
|
||
|
||
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 );
|
||
}
|
||
|
||
/*
|
||
* Use the blinding method and optimisation suggested in section 10 of:
|
||
* KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA,
|
||
* DSS, and other systems. In : Advances in Cryptology—CRYPTO’96. Springer
|
||
* Berlin Heidelberg, 1996. p. 104-113.
|
||
*/
|
||
static int dhm_update_blinding( dhm_context *ctx,
|
||
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
|
||
{
|
||
int ret, count;
|
||
|
||
/*
|
||
* Don't use any blinding the first time a particular X is used,
|
||
* but remember it to use blinding next time.
|
||
*/
|
||
if( mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
|
||
{
|
||
MPI_CHK( mpi_copy( &ctx->pX, &ctx->X ) );
|
||
MPI_CHK( mpi_lset( &ctx->Vi, 1 ) );
|
||
MPI_CHK( mpi_lset( &ctx->Vf, 1 ) );
|
||
|
||
return( 0 );
|
||
}
|
||
|
||
/*
|
||
* Ok, we need blinding. Can we re-use existing values?
|
||
* If yes, just update them by squaring them.
|
||
*/
|
||
if( mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
|
||
{
|
||
MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
|
||
MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
|
||
|
||
MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
|
||
MPI_CHK( mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->P ) );
|
||
|
||
return( 0 );
|
||
}
|
||
|
||
/*
|
||
* We need to generate blinding values from scratch
|
||
*/
|
||
|
||
/* Vi = random( 2, P-1 ) */
|
||
count = 0;
|
||
do
|
||
{
|
||
mpi_fill_random( &ctx->Vi, mpi_size( &ctx->P ), f_rng, p_rng );
|
||
|
||
while( mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
|
||
mpi_shift_r( &ctx->Vi, 1 );
|
||
|
||
if( count++ > 10 )
|
||
return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
|
||
}
|
||
while( mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
|
||
|
||
/* Vf = Vi^-X mod P */
|
||
MPI_CHK( mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
|
||
MPI_CHK( mpi_exp_mod( &ctx->Vf, &ctx->Vf, &ctx->X, &ctx->P, &ctx->RP ) );
|
||
|
||
cleanup:
|
||
return( ret );
|
||
}
|
||
|
||
/*
|
||
* 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 (*f_rng)(void *, unsigned char *, size_t),
|
||
void *p_rng )
|
||
{
|
||
int ret;
|
||
mpi GYb;
|
||
|
||
if( ctx == NULL || *olen < ctx->len )
|
||
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
|
||
|
||
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
|
||
return( ret );
|
||
|
||
mpi_init( &GYb );
|
||
|
||
/* Blind peer's value */
|
||
if( f_rng != NULL )
|
||
{
|
||
MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
|
||
MPI_CHK( mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
|
||
MPI_CHK( mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
|
||
}
|
||
else
|
||
MPI_CHK( mpi_copy( &GYb, &ctx->GY ) );
|
||
|
||
/* Do modular exponentiation */
|
||
MPI_CHK( mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
|
||
&ctx->P, &ctx->RP ) );
|
||
|
||
/* Unblind secret value */
|
||
if( f_rng != NULL )
|
||
{
|
||
MPI_CHK( mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
|
||
MPI_CHK( mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
|
||
}
|
||
|
||
*olen = mpi_size( &ctx->K );
|
||
|
||
MPI_CHK( mpi_write_binary( &ctx->K, output, *olen ) );
|
||
|
||
cleanup:
|
||
mpi_free( &GYb );
|
||
|
||
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->pX); mpi_free( &ctx->Vf ); mpi_free( &ctx->Vi );
|
||
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 );
|
||
|
||
memset( ctx, 0, sizeof( dhm_context ) );
|
||
}
|
||
|
||
#if defined(POLARSSL_ASN1_PARSE_C)
|
||
/*
|
||
* Parse DHM parameters
|
||
*/
|
||
int dhm_parse_dhm( dhm_context *dhm, const unsigned char *dhmin, size_t dhminlen )
|
||
{
|
||
int ret;
|
||
size_t len;
|
||
unsigned char *p, *end;
|
||
#if defined(POLARSSL_PEM_PARSE_C)
|
||
pem_context pem;
|
||
|
||
pem_init( &pem );
|
||
memset( dhm, 0, sizeof( dhm_context ) );
|
||
|
||
ret = pem_read_buffer( &pem,
|
||
"-----BEGIN DH PARAMETERS-----",
|
||
"-----END DH PARAMETERS-----",
|
||
dhmin, NULL, 0, &dhminlen );
|
||
|
||
if( ret == 0 )
|
||
{
|
||
/*
|
||
* Was PEM encoded
|
||
*/
|
||
dhminlen = pem.buflen;
|
||
}
|
||
else if( ret != POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
|
||
goto exit;
|
||
|
||
p = ( ret == 0 ) ? pem.buf : (unsigned char *) dhmin;
|
||
#else
|
||
p = (unsigned char *) dhmin;
|
||
#endif
|
||
end = p + dhminlen;
|
||
|
||
/*
|
||
* DHParams ::= SEQUENCE {
|
||
* prime INTEGER, -- P
|
||
* generator INTEGER, -- g
|
||
* }
|
||
*/
|
||
if( ( ret = asn1_get_tag( &p, end, &len,
|
||
ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
|
||
{
|
||
ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
|
||
goto exit;
|
||
}
|
||
|
||
end = p + len;
|
||
|
||
if( ( ret = asn1_get_mpi( &p, end, &dhm->P ) ) != 0 ||
|
||
( ret = asn1_get_mpi( &p, end, &dhm->G ) ) != 0 )
|
||
{
|
||
ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
|
||
goto exit;
|
||
}
|
||
|
||
if( p != end )
|
||
{
|
||
ret = POLARSSL_ERR_DHM_INVALID_FORMAT +
|
||
POLARSSL_ERR_ASN1_LENGTH_MISMATCH;
|
||
goto exit;
|
||
}
|
||
|
||
ret = 0;
|
||
|
||
exit:
|
||
#if defined(POLARSSL_PEM_PARSE_C)
|
||
pem_free( &pem );
|
||
#endif
|
||
if( ret != 0 )
|
||
dhm_free( dhm );
|
||
|
||
return( ret );
|
||
}
|
||
|
||
#if defined(POLARSSL_FS_IO)
|
||
/*
|
||
* Load all data from a file into a given buffer.
|
||
*/
|
||
static int load_file( const char *path, unsigned char **buf, size_t *n )
|
||
{
|
||
FILE *f;
|
||
long size;
|
||
|
||
if( ( f = fopen( path, "rb" ) ) == NULL )
|
||
return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
|
||
|
||
fseek( f, 0, SEEK_END );
|
||
if( ( size = ftell( f ) ) == -1 )
|
||
{
|
||
fclose( f );
|
||
return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
|
||
}
|
||
fseek( f, 0, SEEK_SET );
|
||
|
||
*n = (size_t) size;
|
||
|
||
if( *n + 1 == 0 ||
|
||
( *buf = (unsigned char *) polarssl_malloc( *n + 1 ) ) == NULL )
|
||
{
|
||
fclose( f );
|
||
return( POLARSSL_ERR_DHM_MALLOC_FAILED );
|
||
}
|
||
|
||
if( fread( *buf, 1, *n, f ) != *n )
|
||
{
|
||
fclose( f );
|
||
polarssl_free( *buf );
|
||
return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
|
||
}
|
||
|
||
fclose( f );
|
||
|
||
(*buf)[*n] = '\0';
|
||
|
||
return( 0 );
|
||
}
|
||
|
||
/*
|
||
* Load and parse DHM parameters
|
||
*/
|
||
int dhm_parse_dhmfile( dhm_context *dhm, const char *path )
|
||
{
|
||
int ret;
|
||
size_t n;
|
||
unsigned char *buf;
|
||
|
||
if ( ( ret = load_file( path, &buf, &n ) ) != 0 )
|
||
return( ret );
|
||
|
||
ret = dhm_parse_dhm( dhm, buf, n );
|
||
|
||
memset( buf, 0, n + 1 );
|
||
polarssl_free( buf );
|
||
|
||
return( ret );
|
||
}
|
||
#endif /* POLARSSL_FS_IO */
|
||
#endif /* POLARSSL_ASN1_PARSE_C */
|
||
|
||
#if defined(POLARSSL_SELF_TEST)
|
||
|
||
#include "polarssl/certs.h"
|
||
|
||
/*
|
||
* Checkup routine
|
||
*/
|
||
int dhm_self_test( int verbose )
|
||
{
|
||
#if defined(POLARSSL_CERTS_C)
|
||
int ret;
|
||
dhm_context dhm;
|
||
|
||
if( verbose != 0 )
|
||
polarssl_printf( " DHM parameter load: " );
|
||
|
||
if( ( ret = dhm_parse_dhm( &dhm, (const unsigned char *) test_dhm_params,
|
||
strlen( test_dhm_params ) ) ) != 0 )
|
||
{
|
||
if( verbose != 0 )
|
||
polarssl_printf( "failed\n" );
|
||
|
||
return( ret );
|
||
}
|
||
|
||
if( verbose != 0 )
|
||
polarssl_printf( "passed\n\n" );
|
||
|
||
dhm_free( &dhm );
|
||
|
||
return( 0 );
|
||
#else
|
||
((void) verbose);
|
||
return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
|
||
#endif
|
||
}
|
||
|
||
#endif
|
||
|
||
#endif
|