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mbedtls/library/dhm.c
Andres Amaya Garcia 1f6301b3c8 Rename mbedtls_zeroize to mbedtls_platform_zeroize
2018-04-17 10:00:21 -05:00

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/*
* Diffie-Hellman-Merkle key exchange
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
/*
* The following sources were referenced in the design of this implementation
* of the Diffie-Hellman-Merkle algorithm:
*
* [1] Handbook of Applied Cryptography - 1997, Chapter 12
* Menezes, van Oorschot and Vanstone
*
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_DHM_C)
#include "mbedtls/dhm.h"
#include "mbedtls/platform_util.h"
#include <string.h>
#if defined(MBEDTLS_PEM_PARSE_C)
#include "mbedtls/pem.h"
#endif
#if defined(MBEDTLS_ASN1_PARSE_C)
#include "mbedtls/asn1.h"
#endif
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#include <stdio.h>
#define mbedtls_printf printf
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
#if !defined(MBEDTLS_DHM_ALT)
/*
* helper to validate the mbedtls_mpi size and import it
*/
static int dhm_read_bignum( mbedtls_mpi *X,
unsigned char **p,
const unsigned char *end )
{
int ret, n;
if( end - *p < 2 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
n = ( (*p)[0] << 8 ) | (*p)[1];
(*p) += 2;
if( (int)( end - *p ) < n )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mbedtls_mpi_read_binary( X, *p, n ) ) != 0 )
return( MBEDTLS_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
*
* This means that we need to return an error if
* public_param < 2 or 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 mbedtls_mpi *param, const mbedtls_mpi *P )
{
mbedtls_mpi L, U;
int ret = 0;
mbedtls_mpi_init( &L ); mbedtls_mpi_init( &U );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &L, 2 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &U, P, 2 ) );
if( mbedtls_mpi_cmp_mpi( param, &L ) < 0 ||
mbedtls_mpi_cmp_mpi( param, &U ) > 0 )
{
ret = MBEDTLS_ERR_DHM_BAD_INPUT_DATA;
}
cleanup:
mbedtls_mpi_free( &L ); mbedtls_mpi_free( &U );
return( ret );
}
void mbedtls_dhm_init( mbedtls_dhm_context *ctx )
{
memset( ctx, 0, sizeof( mbedtls_dhm_context ) );
}
/*
* Parse the ServerKeyExchange parameters
*/
int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx,
unsigned char **p,
const unsigned char *end )
{
int ret;
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 = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
/*
* Setup and write the ServerKeyExchange parameters
*/
int mbedtls_dhm_make_params( mbedtls_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( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
/*
* Generate X as large as possible ( < P )
*/
do
{
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ) );
while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
if( count++ > 10 )
return( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
/*
* Calculate GX = G^X mod P
*/
MBEDTLS_MPI_CHK( mbedtls_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 ) \
do { \
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( ( X ), \
p + 2, \
( n ) ) ); \
*p++ = (unsigned char)( ( n ) >> 8 ); \
*p++ = (unsigned char)( ( n ) ); \
p += ( n ); \
} while( 0 )
n1 = mbedtls_mpi_size( &ctx->P );
n2 = mbedtls_mpi_size( &ctx->G );
n3 = mbedtls_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( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED + ret );
return( 0 );
}
/*
* Set prime modulus and generator
*/
int mbedtls_dhm_set_group( mbedtls_dhm_context *ctx,
const mbedtls_mpi *P,
const mbedtls_mpi *G )
{
int ret;
if( ctx == NULL || P == NULL || G == NULL )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mbedtls_mpi_copy( &ctx->P, P ) ) != 0 ||
( ret = mbedtls_mpi_copy( &ctx->G, G ) ) != 0 )
{
return( MBEDTLS_ERR_DHM_SET_GROUP_FAILED + ret );
}
ctx->len = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
/*
* Import the peer's public value G^Y
*/
int mbedtls_dhm_read_public( mbedtls_dhm_context *ctx,
const unsigned char *input, size_t ilen )
{
int ret;
if( ctx == NULL || ilen < 1 || ilen > ctx->len )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = mbedtls_mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
return( MBEDTLS_ERR_DHM_READ_PUBLIC_FAILED + ret );
return( 0 );
}
/*
* Create own private value X and export G^X
*/
int mbedtls_dhm_make_public( mbedtls_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( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
/*
* generate X and calculate GX = G^X mod P
*/
do
{
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ) );
while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
if( count++ > 10 )
return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
MBEDTLS_MPI_CHK( mbedtls_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 );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( MBEDTLS_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( mbedtls_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( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &ctx->pX, &ctx->X ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->Vi, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_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( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
MBEDTLS_MPI_CHK( mbedtls_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
{
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->Vi, mbedtls_mpi_size( &ctx->P ), f_rng, p_rng ) );
while( mbedtls_mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->Vi, 1 ) );
if( count++ > 10 )
return( MBEDTLS_ERR_MPI_NOT_ACCEPTABLE );
}
while( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
/* Vf = Vi^-X mod P */
MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
MBEDTLS_MPI_CHK( mbedtls_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 mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
unsigned char *output, size_t output_size, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
mbedtls_mpi GYb;
if( ctx == NULL || output_size < ctx->len )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
mbedtls_mpi_init( &GYb );
/* Blind peer's value */
if( f_rng != NULL )
{
MBEDTLS_MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
}
else
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &GYb, &ctx->GY ) );
/* Do modular exponentiation */
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
&ctx->P, &ctx->RP ) );
/* Unblind secret value */
if( f_rng != NULL )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
}
*olen = mbedtls_mpi_size( &ctx->K );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->K, output, *olen ) );
cleanup:
mbedtls_mpi_free( &GYb );
if( ret != 0 )
return( MBEDTLS_ERR_DHM_CALC_SECRET_FAILED + ret );
return( 0 );
}
/*
* Free the components of a DHM key
*/
void mbedtls_dhm_free( mbedtls_dhm_context *ctx )
{
mbedtls_mpi_free( &ctx->pX ); mbedtls_mpi_free( &ctx->Vf );
mbedtls_mpi_free( &ctx->Vi ); mbedtls_mpi_free( &ctx->RP );
mbedtls_mpi_free( &ctx->K ); mbedtls_mpi_free( &ctx->GY );
mbedtls_mpi_free( &ctx->GX ); mbedtls_mpi_free( &ctx->X );
mbedtls_mpi_free( &ctx->G ); mbedtls_mpi_free( &ctx->P );
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_dhm_context ) );
}
#if defined(MBEDTLS_ASN1_PARSE_C)
/*
* Parse DHM parameters
*/
int mbedtls_dhm_parse_dhm( mbedtls_dhm_context *dhm, const unsigned char *dhmin,
size_t dhminlen )
{
int ret;
size_t len;
unsigned char *p, *end;
#if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_context pem;
mbedtls_pem_init( &pem );
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( dhminlen == 0 || dhmin[dhminlen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_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 != MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
goto exit;
p = ( ret == 0 ) ? pem.buf : (unsigned char *) dhmin;
#else
p = (unsigned char *) dhmin;
#endif /* MBEDTLS_PEM_PARSE_C */
end = p + dhminlen;
/*
* DHParams ::= SEQUENCE {
* prime INTEGER, -- P
* generator INTEGER, -- g
* privateValueLength INTEGER OPTIONAL
* }
*/
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 */
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