595 lines
14 KiB
C
595 lines
14 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange
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*
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* Copyright (C) 2006-2014, ARM Limited, All Rights Reserved
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*
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* This file is part of mbed TLS (http://www.polarssl.org)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/*
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* Reference:
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*
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* http://www.cacr.math.uwaterloo.ca/hac/ (chapter 12)
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*/
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#if !defined(POLARSSL_CONFIG_FILE)
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#include "polarssl/config.h"
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#else
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#include POLARSSL_CONFIG_FILE
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#endif
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#if defined(POLARSSL_DHM_C)
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#include "polarssl/dhm.h"
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#if defined(POLARSSL_PEM_PARSE_C)
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#include "polarssl/pem.h"
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#endif
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#if defined(POLARSSL_ASN1_PARSE_C)
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#include "polarssl/asn1.h"
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#endif
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#if defined(POLARSSL_PLATFORM_C)
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#include "polarssl/platform.h"
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#else
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#include <stdlib.h>
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#define polarssl_printf printf
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#define polarssl_malloc malloc
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#define polarssl_free free
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#endif
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/* Implementation that should never be optimized out by the compiler */
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static void polarssl_zeroize( void *v, size_t n ) {
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volatile unsigned char *p = v; while( n-- ) *p++ = 0;
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}
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/*
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* helper to validate the mpi size and import it
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*/
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static int dhm_read_bignum( mpi *X,
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unsigned char **p,
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const unsigned char *end )
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{
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int ret, n;
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if( end - *p < 2 )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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n = ( (*p)[0] << 8 ) | (*p)[1];
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(*p) += 2;
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if( (int)( end - *p ) < n )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = mpi_read_binary( X, *p, n ) ) != 0 )
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return( POLARSSL_ERR_DHM_READ_PARAMS_FAILED + ret );
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(*p) += n;
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return( 0 );
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}
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/*
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* Verify sanity of parameter with regards to P
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*
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* Parameter should be: 2 <= public_param <= P - 2
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*
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* For more information on the attack, see:
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* http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf
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* http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643
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*/
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static int dhm_check_range( const mpi *param, const mpi *P )
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{
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mpi L, U;
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int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA;
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mpi_init( &L ); mpi_init( &U );
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MPI_CHK( mpi_lset( &L, 2 ) );
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MPI_CHK( mpi_sub_int( &U, P, 2 ) );
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if( mpi_cmp_mpi( param, &L ) >= 0 &&
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mpi_cmp_mpi( param, &U ) <= 0 )
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{
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ret = 0;
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}
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cleanup:
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mpi_free( &L ); mpi_free( &U );
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return( ret );
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}
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void dhm_init( dhm_context *ctx )
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{
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memset( ctx, 0, sizeof( dhm_context ) );
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}
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/*
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* Parse the ServerKeyExchange parameters
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*/
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int dhm_read_params( dhm_context *ctx,
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unsigned char **p,
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const unsigned char *end )
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{
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int ret;
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if( ( ret = dhm_read_bignum( &ctx->P, p, end ) ) != 0 ||
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( ret = dhm_read_bignum( &ctx->G, p, end ) ) != 0 ||
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( ret = dhm_read_bignum( &ctx->GY, p, end ) ) != 0 )
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return( ret );
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if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
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return( ret );
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ctx->len = mpi_size( &ctx->P );
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return( 0 );
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}
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/*
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* Setup and write the ServerKeyExchange parameters
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*/
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int dhm_make_params( dhm_context *ctx, int x_size,
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unsigned char *output, size_t *olen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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int ret, count = 0;
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size_t n1, n2, n3;
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unsigned char *p;
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if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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/*
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* Generate X as large as possible ( < P )
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*/
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do
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{
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mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
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while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
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MPI_CHK( mpi_shift_r( &ctx->X, 1 ) );
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if( count++ > 10 )
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return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
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}
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while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
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/*
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* Calculate GX = G^X mod P
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*/
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MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
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&ctx->P , &ctx->RP ) );
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if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
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return( ret );
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/*
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* export P, G, GX
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*/
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#define DHM_MPI_EXPORT(X,n) \
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MPI_CHK( mpi_write_binary( X, p + 2, n ) ); \
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*p++ = (unsigned char)( n >> 8 ); \
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*p++ = (unsigned char)( n ); p += n;
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n1 = mpi_size( &ctx->P );
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n2 = mpi_size( &ctx->G );
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n3 = mpi_size( &ctx->GX );
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p = output;
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DHM_MPI_EXPORT( &ctx->P , n1 );
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DHM_MPI_EXPORT( &ctx->G , n2 );
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DHM_MPI_EXPORT( &ctx->GX, n3 );
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*olen = p - output;
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ctx->len = n1;
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cleanup:
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if( ret != 0 )
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return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );
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return( 0 );
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}
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/*
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* Import the peer's public value G^Y
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*/
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int dhm_read_public( dhm_context *ctx,
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const unsigned char *input, size_t ilen )
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{
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int ret;
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if( ctx == NULL || ilen < 1 || ilen > ctx->len )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
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return( POLARSSL_ERR_DHM_READ_PUBLIC_FAILED + ret );
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return( 0 );
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}
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/*
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* Create own private value X and export G^X
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*/
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int dhm_make_public( dhm_context *ctx, int x_size,
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unsigned char *output, size_t olen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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int ret, count = 0;
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if( ctx == NULL || olen < 1 || olen > ctx->len )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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/*
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* generate X and calculate GX = G^X mod P
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*/
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do
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{
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mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
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while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
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MPI_CHK( mpi_shift_r( &ctx->X, 1 ) );
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if( count++ > 10 )
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return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED );
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}
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while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
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MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
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&ctx->P , &ctx->RP ) );
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if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
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return( ret );
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MPI_CHK( mpi_write_binary( &ctx->GX, output, olen ) );
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cleanup:
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if( ret != 0 )
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return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED + ret );
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return( 0 );
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}
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/*
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* Use the blinding method and optimisation suggested in section 10 of:
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* KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA,
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* DSS, and other systems. In : Advances in Cryptology—CRYPTO’96. Springer
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* Berlin Heidelberg, 1996. p. 104-113.
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*/
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static int dhm_update_blinding( dhm_context *ctx,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
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{
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int ret, count;
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/*
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* Don't use any blinding the first time a particular X is used,
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* but remember it to use blinding next time.
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*/
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if( mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
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{
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MPI_CHK( mpi_copy( &ctx->pX, &ctx->X ) );
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MPI_CHK( mpi_lset( &ctx->Vi, 1 ) );
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MPI_CHK( mpi_lset( &ctx->Vf, 1 ) );
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return( 0 );
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}
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/*
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* Ok, we need blinding. Can we re-use existing values?
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* If yes, just update them by squaring them.
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*/
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if( mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
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{
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MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
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MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
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MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
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MPI_CHK( mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->P ) );
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return( 0 );
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}
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/*
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* We need to generate blinding values from scratch
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*/
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/* Vi = random( 2, P-1 ) */
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count = 0;
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do
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{
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mpi_fill_random( &ctx->Vi, mpi_size( &ctx->P ), f_rng, p_rng );
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while( mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
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MPI_CHK( mpi_shift_r( &ctx->Vi, 1 ) );
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if( count++ > 10 )
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return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
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}
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while( mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
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/* Vf = Vi^-X mod P */
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MPI_CHK( mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
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MPI_CHK( mpi_exp_mod( &ctx->Vf, &ctx->Vf, &ctx->X, &ctx->P, &ctx->RP ) );
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cleanup:
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return( ret );
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}
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/*
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* Derive and export the shared secret (G^Y)^X mod P
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*/
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int dhm_calc_secret( dhm_context *ctx,
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unsigned char *output, size_t *olen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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int ret;
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mpi GYb;
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if( ctx == NULL || *olen < ctx->len )
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return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
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return( ret );
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mpi_init( &GYb );
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/* Blind peer's value */
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if( f_rng != NULL )
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{
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MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
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MPI_CHK( mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
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MPI_CHK( mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
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}
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else
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MPI_CHK( mpi_copy( &GYb, &ctx->GY ) );
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/* Do modular exponentiation */
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MPI_CHK( mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
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&ctx->P, &ctx->RP ) );
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/* Unblind secret value */
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if( f_rng != NULL )
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{
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MPI_CHK( mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
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MPI_CHK( mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
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}
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*olen = mpi_size( &ctx->K );
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MPI_CHK( mpi_write_binary( &ctx->K, output, *olen ) );
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cleanup:
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mpi_free( &GYb );
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if( ret != 0 )
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return( POLARSSL_ERR_DHM_CALC_SECRET_FAILED + ret );
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return( 0 );
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}
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/*
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* Free the components of a DHM key
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*/
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void dhm_free( dhm_context *ctx )
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{
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mpi_free( &ctx->pX); mpi_free( &ctx->Vf ); mpi_free( &ctx->Vi );
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mpi_free( &ctx->RP ); mpi_free( &ctx->K ); mpi_free( &ctx->GY );
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mpi_free( &ctx->GX ); mpi_free( &ctx->X ); mpi_free( &ctx->G );
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mpi_free( &ctx->P );
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polarssl_zeroize( ctx, sizeof( dhm_context ) );
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}
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#if defined(POLARSSL_ASN1_PARSE_C)
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/*
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* Parse DHM parameters
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*/
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int dhm_parse_dhm( dhm_context *dhm, const unsigned char *dhmin,
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size_t dhminlen )
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{
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int ret;
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size_t len;
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unsigned char *p, *end;
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#if defined(POLARSSL_PEM_PARSE_C)
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pem_context pem;
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pem_init( &pem );
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ret = pem_read_buffer( &pem,
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"-----BEGIN DH PARAMETERS-----",
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"-----END DH PARAMETERS-----",
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dhmin, NULL, 0, &dhminlen );
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if( ret == 0 )
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{
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/*
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* Was PEM encoded
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*/
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dhminlen = pem.buflen;
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}
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else if( ret != POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
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goto exit;
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p = ( ret == 0 ) ? pem.buf : (unsigned char *) dhmin;
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#else
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p = (unsigned char *) dhmin;
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#endif /* POLARSSL_PEM_PARSE_C */
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end = p + dhminlen;
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/*
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* DHParams ::= SEQUENCE {
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* prime INTEGER, -- P
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* generator INTEGER, -- g
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* }
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*/
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if( ( ret = asn1_get_tag( &p, end, &len,
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ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
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{
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ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
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goto exit;
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}
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end = p + len;
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if( ( ret = asn1_get_mpi( &p, end, &dhm->P ) ) != 0 ||
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( ret = asn1_get_mpi( &p, end, &dhm->G ) ) != 0 )
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{
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ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
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goto exit;
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}
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if( p != end )
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{
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ret = POLARSSL_ERR_DHM_INVALID_FORMAT +
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POLARSSL_ERR_ASN1_LENGTH_MISMATCH;
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goto exit;
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}
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ret = 0;
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dhm->len = mpi_size( &dhm->P );
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exit:
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#if defined(POLARSSL_PEM_PARSE_C)
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pem_free( &pem );
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#endif
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if( ret != 0 )
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dhm_free( dhm );
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return( ret );
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}
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#if defined(POLARSSL_FS_IO)
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/*
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* Load all data from a file into a given buffer.
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*/
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static int load_file( const char *path, unsigned char **buf, size_t *n )
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{
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FILE *f;
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long size;
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if( ( f = fopen( path, "rb" ) ) == NULL )
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return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
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fseek( f, 0, SEEK_END );
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if( ( size = ftell( f ) ) == -1 )
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{
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fclose( f );
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return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
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}
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fseek( f, 0, SEEK_SET );
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*n = (size_t) size;
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if( *n + 1 == 0 ||
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( *buf = (unsigned char *) polarssl_malloc( *n + 1 ) ) == NULL )
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{
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fclose( f );
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return( POLARSSL_ERR_DHM_MALLOC_FAILED );
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}
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if( fread( *buf, 1, *n, f ) != *n )
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{
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fclose( f );
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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 );
|
||
|
||
polarssl_zeroize( buf, 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;
|
||
|
||
dhm_init( &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" );
|
||
|
||
ret = 1;
|
||
goto exit;
|
||
}
|
||
|
||
if( verbose != 0 )
|
||
polarssl_printf( "passed\n\n" );
|
||
|
||
exit:
|
||
dhm_free( &dhm );
|
||
|
||
return( ret );
|
||
#else
|
||
if( verbose != 0 )
|
||
polarssl_printf( " DHM parameter load: skipped\n" );
|
||
|
||
return( 0 );
|
||
#endif /* POLARSSL_CERTS_C */
|
||
}
|
||
|
||
#endif /* POLARSSL_SELF_TEST */
|
||
|
||
#endif /* POLARSSL_DHM_C */
|