660 lines
17 KiB
C
660 lines
17 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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/*
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* The following sources were referenced in the design of this implementation
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* of the Diffie-Hellman-Merkle algorithm:
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*
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* [1] Handbook of Applied Cryptography - 1997, Chapter 12
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* Menezes, van Oorschot and Vanstone
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*
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_DHM_C)
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#include "mbedtls/dhm.h"
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#include "mbedtls/platform_util.h"
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#include <string.h>
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#if defined(MBEDTLS_PEM_PARSE_C)
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#include "mbedtls/pem.h"
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#endif
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#if defined(MBEDTLS_ASN1_PARSE_C)
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#include "mbedtls/asn1.h"
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#endif
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#if defined(MBEDTLS_PLATFORM_C)
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#include "mbedtls/platform.h"
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#else
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#include <stdlib.h>
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#include <stdio.h>
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#define mbedtls_printf printf
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#define mbedtls_calloc calloc
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#define mbedtls_free free
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#endif
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#if !defined(MBEDTLS_DHM_ALT)
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/*
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* helper to validate the mbedtls_mpi size and import it
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*/
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static int dhm_read_bignum( mbedtls_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( MBEDTLS_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( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = mbedtls_mpi_read_binary( X, *p, n ) ) != 0 )
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return( MBEDTLS_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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* This means that we need to return an error if
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* public_param < 2 or 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 mbedtls_mpi *param, const mbedtls_mpi *P )
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{
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mbedtls_mpi L, U;
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int ret = 0;
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mbedtls_mpi_init( &L ); mbedtls_mpi_init( &U );
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MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &L, 2 ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &U, P, 2 ) );
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if( mbedtls_mpi_cmp_mpi( param, &L ) < 0 ||
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mbedtls_mpi_cmp_mpi( param, &U ) > 0 )
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{
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ret = MBEDTLS_ERR_DHM_BAD_INPUT_DATA;
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}
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cleanup:
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mbedtls_mpi_free( &L ); mbedtls_mpi_free( &U );
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return( ret );
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}
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void mbedtls_dhm_init( mbedtls_dhm_context *ctx )
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{
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memset( ctx, 0, sizeof( mbedtls_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 mbedtls_dhm_read_params( mbedtls_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 = mbedtls_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 mbedtls_dhm_make_params( mbedtls_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( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
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return( MBEDTLS_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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MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ) );
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while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
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MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
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if( count++ > 10 )
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return( MBEDTLS_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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MBEDTLS_MPI_CHK( mbedtls_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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do { \
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MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( ( X ), \
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p + 2, \
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( n ) ) ); \
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*p++ = (unsigned char)( ( n ) >> 8 ); \
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*p++ = (unsigned char)( ( n ) ); \
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p += ( n ); \
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} while( 0 )
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n1 = mbedtls_mpi_size( &ctx->P );
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n2 = mbedtls_mpi_size( &ctx->G );
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n3 = mbedtls_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( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED + ret );
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return( 0 );
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}
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/*
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* Set prime modulus and generator
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*/
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int mbedtls_dhm_set_group( mbedtls_dhm_context *ctx,
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const mbedtls_mpi *P,
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const mbedtls_mpi *G )
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{
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int ret;
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if( ctx == NULL || P == NULL || G == NULL )
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return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = mbedtls_mpi_copy( &ctx->P, P ) ) != 0 ||
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( ret = mbedtls_mpi_copy( &ctx->G, G ) ) != 0 )
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{
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return( MBEDTLS_ERR_DHM_SET_GROUP_FAILED + ret );
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}
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ctx->len = mbedtls_mpi_size( &ctx->P );
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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 mbedtls_dhm_read_public( mbedtls_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( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
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if( ( ret = mbedtls_mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
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return( MBEDTLS_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 mbedtls_dhm_make_public( mbedtls_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( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
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if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
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return( MBEDTLS_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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MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ) );
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while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
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MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
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if( count++ > 10 )
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return( MBEDTLS_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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MBEDTLS_MPI_CHK( mbedtls_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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MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->GX, output, olen ) );
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cleanup:
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if( ret != 0 )
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return( MBEDTLS_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( mbedtls_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( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
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{
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MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &ctx->pX, &ctx->X ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->Vi, 1 ) );
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MBEDTLS_MPI_CHK( mbedtls_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( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
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{
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
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MBEDTLS_MPI_CHK( mbedtls_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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MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->Vi, mbedtls_mpi_size( &ctx->P ), f_rng, p_rng ) );
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while( mbedtls_mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
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MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->Vi, 1 ) );
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if( count++ > 10 )
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return( MBEDTLS_ERR_MPI_NOT_ACCEPTABLE );
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}
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while( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
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/* Vf = Vi^-X mod P */
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MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
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MBEDTLS_MPI_CHK( mbedtls_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 mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
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unsigned char *output, size_t output_size, 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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mbedtls_mpi GYb;
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if( ctx == NULL || output_size < ctx->len )
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return( MBEDTLS_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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mbedtls_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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MBEDTLS_MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
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}
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else
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MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &GYb, &ctx->GY ) );
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/* Do modular exponentiation */
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MBEDTLS_MPI_CHK( mbedtls_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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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
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}
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*olen = mbedtls_mpi_size( &ctx->K );
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MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->K, output, *olen ) );
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cleanup:
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mbedtls_mpi_free( &GYb );
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if( ret != 0 )
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return( MBEDTLS_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 mbedtls_dhm_free( mbedtls_dhm_context *ctx )
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{
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mbedtls_mpi_free( &ctx->pX ); mbedtls_mpi_free( &ctx->Vf );
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mbedtls_mpi_free( &ctx->Vi ); mbedtls_mpi_free( &ctx->RP );
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mbedtls_mpi_free( &ctx->K ); mbedtls_mpi_free( &ctx->GY );
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mbedtls_mpi_free( &ctx->GX ); mbedtls_mpi_free( &ctx->X );
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mbedtls_mpi_free( &ctx->G ); mbedtls_mpi_free( &ctx->P );
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mbedtls_platform_zeroize( ctx, sizeof( mbedtls_dhm_context ) );
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}
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#if defined(MBEDTLS_ASN1_PARSE_C)
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/*
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* Parse DHM parameters
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*/
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int mbedtls_dhm_parse_dhm( mbedtls_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(MBEDTLS_PEM_PARSE_C)
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mbedtls_pem_context pem;
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mbedtls_pem_init( &pem );
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/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
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if( dhminlen == 0 || dhmin[dhminlen - 1] != '\0' )
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ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
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else
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ret = mbedtls_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 != MBEDTLS_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 /* MBEDTLS_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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* privateValueLength INTEGER OPTIONAL
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|
* }
|
|
*/
|
|
if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
|
|
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
|
|
{
|
|
ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
|
|
goto exit;
|
|
}
|
|
|
|
end = p + len;
|
|
|
|
if( ( ret = mbedtls_asn1_get_mpi( &p, end, &dhm->P ) ) != 0 ||
|
|
( ret = mbedtls_asn1_get_mpi( &p, end, &dhm->G ) ) != 0 )
|
|
{
|
|
ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
|
|
goto exit;
|
|
}
|
|
|
|
if( p != end )
|
|
{
|
|
/* This might be the optional privateValueLength.
|
|
* If so, we can cleanly discard it */
|
|
mbedtls_mpi rec;
|
|
mbedtls_mpi_init( &rec );
|
|
ret = mbedtls_asn1_get_mpi( &p, end, &rec );
|
|
mbedtls_mpi_free( &rec );
|
|
if ( ret != 0 )
|
|
{
|
|
ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
|
|
goto exit;
|
|
}
|
|
if ( p != end )
|
|
{
|
|
ret = MBEDTLS_ERR_DHM_INVALID_FORMAT +
|
|
MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
|
|
goto exit;
|
|
}
|
|
}
|
|
|
|
ret = 0;
|
|
|
|
dhm->len = mbedtls_mpi_size( &dhm->P );
|
|
|
|
exit:
|
|
#if defined(MBEDTLS_PEM_PARSE_C)
|
|
mbedtls_pem_free( &pem );
|
|
#endif
|
|
if( ret != 0 )
|
|
mbedtls_dhm_free( dhm );
|
|
|
|
return( ret );
|
|
}
|
|
|
|
#if defined(MBEDTLS_FS_IO)
|
|
/*
|
|
* Load all data from a file into a given buffer.
|
|
*
|
|
* The file is expected to contain either PEM or DER encoded data.
|
|
* A terminating null byte is always appended. It is included in the announced
|
|
* length only if the data looks like it is PEM encoded.
|
|
*/
|
|
static int load_file( const char *path, unsigned char **buf, size_t *n )
|
|
{
|
|
FILE *f;
|
|
long size;
|
|
|
|
if( ( f = fopen( path, "rb" ) ) == NULL )
|
|
return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
|
|
|
|
fseek( f, 0, SEEK_END );
|
|
if( ( size = ftell( f ) ) == -1 )
|
|
{
|
|
fclose( f );
|
|
return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
|
|
}
|
|
fseek( f, 0, SEEK_SET );
|
|
|
|
*n = (size_t) size;
|
|
|
|
if( *n + 1 == 0 ||
|
|
( *buf = mbedtls_calloc( 1, *n + 1 ) ) == NULL )
|
|
{
|
|
fclose( f );
|
|
return( MBEDTLS_ERR_DHM_ALLOC_FAILED );
|
|
}
|
|
|
|
if( fread( *buf, 1, *n, f ) != *n )
|
|
{
|
|
fclose( f );
|
|
|
|
mbedtls_platform_zeroize( *buf, *n + 1 );
|
|
mbedtls_free( *buf );
|
|
|
|
return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
|
|
}
|
|
|
|
fclose( f );
|
|
|
|
(*buf)[*n] = '\0';
|
|
|
|
if( strstr( (const char *) *buf, "-----BEGIN " ) != NULL )
|
|
++*n;
|
|
|
|
return( 0 );
|
|
}
|
|
|
|
/*
|
|
* Load and parse DHM parameters
|
|
*/
|
|
int mbedtls_dhm_parse_dhmfile( mbedtls_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 = mbedtls_dhm_parse_dhm( dhm, buf, n );
|
|
|
|
mbedtls_platform_zeroize( buf, n );
|
|
mbedtls_free( buf );
|
|
|
|
return( ret );
|
|
}
|
|
#endif /* MBEDTLS_FS_IO */
|
|
#endif /* MBEDTLS_ASN1_PARSE_C */
|
|
#endif /* MBEDTLS_DHM_ALT */
|
|
|
|
#if defined(MBEDTLS_SELF_TEST)
|
|
|
|
static const char mbedtls_test_dhm_params[] =
|
|
"-----BEGIN DH PARAMETERS-----\r\n"
|
|
"MIGHAoGBAJ419DBEOgmQTzo5qXl5fQcN9TN455wkOL7052HzxxRVMyhYmwQcgJvh\r\n"
|
|
"1sa18fyfR9OiVEMYglOpkqVoGLN7qd5aQNNi5W7/C+VBdHTBJcGZJyyP5B3qcz32\r\n"
|
|
"9mLJKudlVudV0Qxk5qUJaPZ/xupz0NyoVpviuiBOI1gNi8ovSXWzAgEC\r\n"
|
|
"-----END DH PARAMETERS-----\r\n";
|
|
|
|
static const size_t mbedtls_test_dhm_params_len = sizeof( mbedtls_test_dhm_params );
|
|
|
|
/*
|
|
* Checkup routine
|
|
*/
|
|
int mbedtls_dhm_self_test( int verbose )
|
|
{
|
|
int ret;
|
|
mbedtls_dhm_context dhm;
|
|
|
|
mbedtls_dhm_init( &dhm );
|
|
|
|
if( verbose != 0 )
|
|
mbedtls_printf( " DHM parameter load: " );
|
|
|
|
if( ( ret = mbedtls_dhm_parse_dhm( &dhm,
|
|
(const unsigned char *) mbedtls_test_dhm_params,
|
|
mbedtls_test_dhm_params_len ) ) != 0 )
|
|
{
|
|
if( verbose != 0 )
|
|
mbedtls_printf( "failed\n" );
|
|
|
|
ret = 1;
|
|
goto exit;
|
|
}
|
|
|
|
if( verbose != 0 )
|
|
mbedtls_printf( "passed\n\n" );
|
|
|
|
exit:
|
|
mbedtls_dhm_free( &dhm );
|
|
|
|
return( ret );
|
|
}
|
|
|
|
#endif /* MBEDTLS_SELF_TEST */
|
|
|
|
#endif /* MBEDTLS_DHM_C */
|