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mbedtls/library/ctr_drbg.c
Andres Amaya Garcia 6a54336897 Fix integer overflows in buffer bound checks 
Fix potential integer overflows in the following functions:
  * mbedtls_md2_update() to be bypassed and cause
  * mbedtls_cipher_update()
  * mbedtls_ctr_drbg_reseed()
This overflows would mainly be exploitable in 32-bit systems and could
cause buffer bound checks to be bypassed.
2017-02-15 23:31:07 +02:00

595 lines
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/*
* CTR_DRBG implementation based on AES-256 (NIST SP 800-90)
*
* 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 NIST SP 800-90 DRBGs are described in the following publucation.
*
* http://csrc.nist.gov/publications/nistpubs/800-90/SP800-90revised_March2007.pdf
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_CTR_DRBG_C)
#include "mbedtls/ctr_drbg.h"
#include <string.h>
#if defined(MBEDTLS_FS_IO)
#include <stdio.h>
#endif
#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#endif /* MBEDTLS_PLATFORM_C */
#endif /* MBEDTLS_SELF_TEST */
/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
/*
* CTR_DRBG context initialization
*/
void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx )
{
memset( ctx, 0, sizeof( mbedtls_ctr_drbg_context ) );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
/*
* Non-public function wrapped by mbedtls_ctr_drbg_seed(). Necessary to allow
* NIST tests to succeed (which require known length fixed entropy)
*/
int mbedtls_ctr_drbg_seed_entropy_len(
mbedtls_ctr_drbg_context *ctx,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len,
size_t entropy_len )
{
int ret;
unsigned char key[MBEDTLS_CTR_DRBG_KEYSIZE];
memset( key, 0, MBEDTLS_CTR_DRBG_KEYSIZE );
mbedtls_aes_init( &ctx->aes_ctx );
ctx->f_entropy = f_entropy;
ctx->p_entropy = p_entropy;
ctx->entropy_len = entropy_len;
ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
/*
* Initialize with an empty key
*/
mbedtls_aes_setkey_enc( &ctx->aes_ctx, key, MBEDTLS_CTR_DRBG_KEYBITS );
if( ( ret = mbedtls_ctr_drbg_reseed( ctx, custom, len ) ) != 0 )
return( ret );
return( 0 );
}
int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len )
{
return( mbedtls_ctr_drbg_seed_entropy_len( ctx, f_entropy, p_entropy, custom, len,
MBEDTLS_CTR_DRBG_ENTROPY_LEN ) );
}
void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx )
{
if( ctx == NULL )
return;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_aes_free( &ctx->aes_ctx );
mbedtls_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
}
void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx, int resistance )
{
ctx->prediction_resistance = resistance;
}
void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx, size_t len )
{
ctx->entropy_len = len;
}
void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx, int interval )
{
ctx->reseed_interval = interval;
}
static int block_cipher_df( unsigned char *output,
const unsigned char *data, size_t data_len )
{
unsigned char buf[MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + MBEDTLS_CTR_DRBG_BLOCKSIZE + 16];
unsigned char tmp[MBEDTLS_CTR_DRBG_SEEDLEN];
unsigned char key[MBEDTLS_CTR_DRBG_KEYSIZE];
unsigned char chain[MBEDTLS_CTR_DRBG_BLOCKSIZE];
unsigned char *p, *iv;
mbedtls_aes_context aes_ctx;
int i, j;
size_t buf_len, use_len;
if( data_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
memset( buf, 0, MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + MBEDTLS_CTR_DRBG_BLOCKSIZE + 16 );
mbedtls_aes_init( &aes_ctx );
/*
* Construct IV (16 bytes) and S in buffer
* IV = Counter (in 32-bits) padded to 16 with zeroes
* S = Length input string (in 32-bits) || Length of output (in 32-bits) ||
* data || 0x80
* (Total is padded to a multiple of 16-bytes with zeroes)
*/
p = buf + MBEDTLS_CTR_DRBG_BLOCKSIZE;
*p++ = ( data_len >> 24 ) & 0xff;
*p++ = ( data_len >> 16 ) & 0xff;
*p++ = ( data_len >> 8 ) & 0xff;
*p++ = ( data_len ) & 0xff;
p += 3;
*p++ = MBEDTLS_CTR_DRBG_SEEDLEN;
memcpy( p, data, data_len );
p[data_len] = 0x80;
buf_len = MBEDTLS_CTR_DRBG_BLOCKSIZE + 8 + data_len + 1;
for( i = 0; i < MBEDTLS_CTR_DRBG_KEYSIZE; i++ )
key[i] = i;
mbedtls_aes_setkey_enc( &aes_ctx, key, MBEDTLS_CTR_DRBG_KEYBITS );
/*
* Reduce data to MBEDTLS_CTR_DRBG_SEEDLEN bytes of data
*/
for( j = 0; j < MBEDTLS_CTR_DRBG_SEEDLEN; j += MBEDTLS_CTR_DRBG_BLOCKSIZE )
{
p = buf;
memset( chain, 0, MBEDTLS_CTR_DRBG_BLOCKSIZE );
use_len = buf_len;
while( use_len > 0 )
{
for( i = 0; i < MBEDTLS_CTR_DRBG_BLOCKSIZE; i++ )
chain[i] ^= p[i];
p += MBEDTLS_CTR_DRBG_BLOCKSIZE;
use_len -= ( use_len >= MBEDTLS_CTR_DRBG_BLOCKSIZE ) ?
MBEDTLS_CTR_DRBG_BLOCKSIZE : use_len;
mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_ENCRYPT, chain, chain );
}
memcpy( tmp + j, chain, MBEDTLS_CTR_DRBG_BLOCKSIZE );
/*
* Update IV
*/
buf[3]++;
}
/*
* Do final encryption with reduced data
*/
mbedtls_aes_setkey_enc( &aes_ctx, tmp, MBEDTLS_CTR_DRBG_KEYBITS );
iv = tmp + MBEDTLS_CTR_DRBG_KEYSIZE;
p = output;
for( j = 0; j < MBEDTLS_CTR_DRBG_SEEDLEN; j += MBEDTLS_CTR_DRBG_BLOCKSIZE )
{
mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
memcpy( p, iv, MBEDTLS_CTR_DRBG_BLOCKSIZE );
p += MBEDTLS_CTR_DRBG_BLOCKSIZE;
}
mbedtls_aes_free( &aes_ctx );
return( 0 );
}
static int ctr_drbg_update_internal( mbedtls_ctr_drbg_context *ctx,
const unsigned char data[MBEDTLS_CTR_DRBG_SEEDLEN] )
{
unsigned char tmp[MBEDTLS_CTR_DRBG_SEEDLEN];
unsigned char *p = tmp;
int i, j;
memset( tmp, 0, MBEDTLS_CTR_DRBG_SEEDLEN );
for( j = 0; j < MBEDTLS_CTR_DRBG_SEEDLEN; j += MBEDTLS_CTR_DRBG_BLOCKSIZE )
{
/*
* Increase counter
*/
for( i = MBEDTLS_CTR_DRBG_BLOCKSIZE; i > 0; i-- )
if( ++ctx->counter[i - 1] != 0 )
break;
/*
* Crypt counter block
*/
mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, p );
p += MBEDTLS_CTR_DRBG_BLOCKSIZE;
}
for( i = 0; i < MBEDTLS_CTR_DRBG_SEEDLEN; i++ )
tmp[i] ^= data[i];
/*
* Update key and counter
*/
mbedtls_aes_setkey_enc( &ctx->aes_ctx, tmp, MBEDTLS_CTR_DRBG_KEYBITS );
memcpy( ctx->counter, tmp + MBEDTLS_CTR_DRBG_KEYSIZE, MBEDTLS_CTR_DRBG_BLOCKSIZE );
return( 0 );
}
void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len )
{
unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN];
if( add_len > 0 )
{
/* MAX_INPUT would be more logical here, but we have to match
* block_cipher_df()'s limits since we can't propagate errors */
if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT;
block_cipher_df( add_input, additional, add_len );
ctr_drbg_update_internal( ctx, add_input );
}
}
int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t len )
{
unsigned char seed[MBEDTLS_CTR_DRBG_MAX_SEED_INPUT];
size_t seedlen = 0;
if( ctx->entropy_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ||
len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - ctx->entropy_len )
return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
memset( seed, 0, MBEDTLS_CTR_DRBG_MAX_SEED_INPUT );
/*
* Gather entropy_len bytes of entropy to seed state
*/
if( 0 != ctx->f_entropy( ctx->p_entropy, seed,
ctx->entropy_len ) )
{
return( MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED );
}
seedlen += ctx->entropy_len;
/*
* Add additional data
*/
if( additional && len )
{
memcpy( seed + seedlen, additional, len );
seedlen += len;
}
/*
* Reduce to 384 bits
*/
block_cipher_df( seed, seed, seedlen );
/*
* Update state
*/
ctr_drbg_update_internal( ctx, seed );
ctx->reseed_counter = 1;
return( 0 );
}
int mbedtls_ctr_drbg_random_with_add( void *p_rng,
unsigned char *output, size_t output_len,
const unsigned char *additional, size_t add_len )
{
int ret = 0;
mbedtls_ctr_drbg_context *ctx = (mbedtls_ctr_drbg_context *) p_rng;
unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN];
unsigned char *p = output;
unsigned char tmp[MBEDTLS_CTR_DRBG_BLOCKSIZE];
int i;
size_t use_len;
if( output_len > MBEDTLS_CTR_DRBG_MAX_REQUEST )
return( MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG );
if( add_len > MBEDTLS_CTR_DRBG_MAX_INPUT )
return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
memset( add_input, 0, MBEDTLS_CTR_DRBG_SEEDLEN );
if( ctx->reseed_counter > ctx->reseed_interval ||
ctx->prediction_resistance )
{
if( ( ret = mbedtls_ctr_drbg_reseed( ctx, additional, add_len ) ) != 0 )
return( ret );
add_len = 0;
}
if( add_len > 0 )
{
block_cipher_df( add_input, additional, add_len );
ctr_drbg_update_internal( ctx, add_input );
}
while( output_len > 0 )
{
/*
* Increase counter
*/
for( i = MBEDTLS_CTR_DRBG_BLOCKSIZE; i > 0; i-- )
if( ++ctx->counter[i - 1] != 0 )
break;
/*
* Crypt counter block
*/
mbedtls_aes_crypt_ecb( &ctx->aes_ctx, MBEDTLS_AES_ENCRYPT, ctx->counter, tmp );
use_len = ( output_len > MBEDTLS_CTR_DRBG_BLOCKSIZE ) ? MBEDTLS_CTR_DRBG_BLOCKSIZE :
output_len;
/*
* Copy random block to destination
*/
memcpy( p, tmp, use_len );
p += use_len;
output_len -= use_len;
}
ctr_drbg_update_internal( ctx, add_input );
ctx->reseed_counter++;
return( 0 );
}
int mbedtls_ctr_drbg_random( void *p_rng, unsigned char *output, size_t output_len )
{
int ret;
mbedtls_ctr_drbg_context *ctx = (mbedtls_ctr_drbg_context *) p_rng;
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
ret = mbedtls_ctr_drbg_random_with_add( ctx, output, output_len, NULL, 0 );
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
#if defined(MBEDTLS_FS_IO)
int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path )
{
int ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR;
FILE *f;
unsigned char buf[ MBEDTLS_CTR_DRBG_MAX_INPUT ];
if( ( f = fopen( path, "wb" ) ) == NULL )
return( MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR );
if( ( ret = mbedtls_ctr_drbg_random( ctx, buf, MBEDTLS_CTR_DRBG_MAX_INPUT ) ) != 0 )
goto exit;
if( fwrite( buf, 1, MBEDTLS_CTR_DRBG_MAX_INPUT, f ) != MBEDTLS_CTR_DRBG_MAX_INPUT )
{
ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR;
goto exit;
}
ret = 0;
exit:
fclose( f );
return( ret );
}
int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path )
{
FILE *f;
size_t n;
unsigned char buf[ MBEDTLS_CTR_DRBG_MAX_INPUT ];
if( ( f = fopen( path, "rb" ) ) == NULL )
return( MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR );
fseek( f, 0, SEEK_END );
n = (size_t) ftell( f );
fseek( f, 0, SEEK_SET );
if( n > MBEDTLS_CTR_DRBG_MAX_INPUT )
{
fclose( f );
return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
}
if( fread( buf, 1, n, f ) != n )
{
fclose( f );
return( MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR );
}
fclose( f );
mbedtls_ctr_drbg_update( ctx, buf, n );
return( mbedtls_ctr_drbg_write_seed_file( ctx, path ) );
}
#endif /* MBEDTLS_FS_IO */
#if defined(MBEDTLS_SELF_TEST)
static const unsigned char entropy_source_pr[96] =
{ 0xc1, 0x80, 0x81, 0xa6, 0x5d, 0x44, 0x02, 0x16,
0x19, 0xb3, 0xf1, 0x80, 0xb1, 0xc9, 0x20, 0x02,
0x6a, 0x54, 0x6f, 0x0c, 0x70, 0x81, 0x49, 0x8b,
0x6e, 0xa6, 0x62, 0x52, 0x6d, 0x51, 0xb1, 0xcb,
0x58, 0x3b, 0xfa, 0xd5, 0x37, 0x5f, 0xfb, 0xc9,
0xff, 0x46, 0xd2, 0x19, 0xc7, 0x22, 0x3e, 0x95,
0x45, 0x9d, 0x82, 0xe1, 0xe7, 0x22, 0x9f, 0x63,
0x31, 0x69, 0xd2, 0x6b, 0x57, 0x47, 0x4f, 0xa3,
0x37, 0xc9, 0x98, 0x1c, 0x0b, 0xfb, 0x91, 0x31,
0x4d, 0x55, 0xb9, 0xe9, 0x1c, 0x5a, 0x5e, 0xe4,
0x93, 0x92, 0xcf, 0xc5, 0x23, 0x12, 0xd5, 0x56,
0x2c, 0x4a, 0x6e, 0xff, 0xdc, 0x10, 0xd0, 0x68 };
static const unsigned char entropy_source_nopr[64] =
{ 0x5a, 0x19, 0x4d, 0x5e, 0x2b, 0x31, 0x58, 0x14,
0x54, 0xde, 0xf6, 0x75, 0xfb, 0x79, 0x58, 0xfe,
0xc7, 0xdb, 0x87, 0x3e, 0x56, 0x89, 0xfc, 0x9d,
0x03, 0x21, 0x7c, 0x68, 0xd8, 0x03, 0x38, 0x20,
0xf9, 0xe6, 0x5e, 0x04, 0xd8, 0x56, 0xf3, 0xa9,
0xc4, 0x4a, 0x4c, 0xbd, 0xc1, 0xd0, 0x08, 0x46,
0xf5, 0x98, 0x3d, 0x77, 0x1c, 0x1b, 0x13, 0x7e,
0x4e, 0x0f, 0x9d, 0x8e, 0xf4, 0x09, 0xf9, 0x2e };
static const unsigned char nonce_pers_pr[16] =
{ 0xd2, 0x54, 0xfc, 0xff, 0x02, 0x1e, 0x69, 0xd2,
0x29, 0xc9, 0xcf, 0xad, 0x85, 0xfa, 0x48, 0x6c };
static const unsigned char nonce_pers_nopr[16] =
{ 0x1b, 0x54, 0xb8, 0xff, 0x06, 0x42, 0xbf, 0xf5,
0x21, 0xf1, 0x5c, 0x1c, 0x0b, 0x66, 0x5f, 0x3f };
static const unsigned char result_pr[16] =
{ 0x34, 0x01, 0x16, 0x56, 0xb4, 0x29, 0x00, 0x8f,
0x35, 0x63, 0xec, 0xb5, 0xf2, 0x59, 0x07, 0x23 };
static const unsigned char result_nopr[16] =
{ 0xa0, 0x54, 0x30, 0x3d, 0x8a, 0x7e, 0xa9, 0x88,
0x9d, 0x90, 0x3e, 0x07, 0x7c, 0x6f, 0x21, 0x8f };
static size_t test_offset;
static int ctr_drbg_self_test_entropy( void *data, unsigned char *buf,
size_t len )
{
const unsigned char *p = data;
memcpy( buf, p + test_offset, len );
test_offset += len;
return( 0 );
}
#define CHK( c ) if( (c) != 0 ) \
{ \
if( verbose != 0 ) \
mbedtls_printf( "failed\n" ); \
return( 1 ); \
}
/*
* Checkup routine
*/
int mbedtls_ctr_drbg_self_test( int verbose )
{
mbedtls_ctr_drbg_context ctx;
unsigned char buf[16];
mbedtls_ctr_drbg_init( &ctx );
/*
* Based on a NIST CTR_DRBG test vector (PR = True)
*/
if( verbose != 0 )
mbedtls_printf( " CTR_DRBG (PR = TRUE) : " );
test_offset = 0;
CHK( mbedtls_ctr_drbg_seed_entropy_len( &ctx, ctr_drbg_self_test_entropy,
(void *) entropy_source_pr, nonce_pers_pr, 16, 32 ) );
mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, MBEDTLS_CTR_DRBG_BLOCKSIZE ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, MBEDTLS_CTR_DRBG_BLOCKSIZE ) );
CHK( memcmp( buf, result_pr, MBEDTLS_CTR_DRBG_BLOCKSIZE ) );
mbedtls_ctr_drbg_free( &ctx );
if( verbose != 0 )
mbedtls_printf( "passed\n" );
/*
* Based on a NIST CTR_DRBG test vector (PR = FALSE)
*/
if( verbose != 0 )
mbedtls_printf( " CTR_DRBG (PR = FALSE): " );
mbedtls_ctr_drbg_init( &ctx );
test_offset = 0;
CHK( mbedtls_ctr_drbg_seed_entropy_len( &ctx, ctr_drbg_self_test_entropy,
(void *) entropy_source_nopr, nonce_pers_nopr, 16, 32 ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, 16 ) );
CHK( mbedtls_ctr_drbg_reseed( &ctx, NULL, 0 ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, 16 ) );
CHK( memcmp( buf, result_nopr, 16 ) );
mbedtls_ctr_drbg_free( &ctx );
if( verbose != 0 )
mbedtls_printf( "passed\n" );
if( verbose != 0 )
mbedtls_printf( "\n" );
return( 0 );
}
#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_CTR_DRBG_C */
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