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mbedtls/library/chachapoly.c
Manuel Pégourié-Gonnard 346b8d5050 chachapoly: split crypt_and_mac() to match GCM API 
In addition to making the APIs of the various AEAD modules more consistent
with each other, it's useful to have an auth_decrypt() function so that we can
safely check the tag ourselves, as the user might otherwise do it in an
insecure way (or even forget to do it altogether).
2018-05-24 13:37:31 +02:00

533 lines
16 KiB
C
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/**
* \file chachapoly.c
*
* \brief ChaCha20-Poly1305 AEAD construction based on RFC 7539.
*
* Copyright (C) 2006-2016, 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)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_CHACHAPOLY_C)
#include "mbedtls/chachapoly.h"
#include <string.h>
#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 */
#if !defined(MBEDTLS_CHACHAPOLY_ALT)
#define CHACHAPOLY_STATE_INIT ( 0 )
#define CHACHAPOLY_STATE_AAD ( 1 )
#define CHACHAPOLY_STATE_CIPHERTEXT ( 2 ) /* Encrypting or decrypting */
#define CHACHAPOLY_STATE_FINISHED ( 3 )
/* 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;
}
/**
* \brief Adds padding bytes (zeroes) to pad the AAD for Poly1305.
*
* \param ctx The ChaCha20-Poly1305 context.
*/
static void mbedtls_chachapoly_pad_aad( mbedtls_chachapoly_context *ctx )
{
uint32_t partial_block_len = (uint32_t) ( ctx->aad_len % 16U );
unsigned char zeroes[15];
if ( partial_block_len > 0U )
{
memset( zeroes, 0, sizeof( zeroes ) );
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx,
16U - partial_block_len,
zeroes );
}
}
/**
* \brief Adds padding bytes (zeroes) to pad the ciphertext for Poly1305.
*
* \param ctx The ChaCha20-Poly1305 context.
*/
static void mbedtls_chachapoly_pad_ciphertext( mbedtls_chachapoly_context *ctx )
{
uint32_t partial_block_len = (uint32_t) ( ctx->ciphertext_len % 16U );
unsigned char zeroes[15];
if ( partial_block_len > 0U )
{
memset( zeroes, 0, sizeof( zeroes ) );
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx,
16U - partial_block_len,
zeroes );
}
}
void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx )
{
if ( ctx != NULL )
{
mbedtls_chacha20_init( &ctx->chacha20_ctx );
mbedtls_poly1305_init( &ctx->poly1305_ctx );
ctx->aad_len = 0U;
ctx->ciphertext_len = 0U;
ctx->state = CHACHAPOLY_STATE_INIT;
ctx->mode = MBEDTLS_CHACHAPOLY_ENCRYPT;
}
}
void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx )
{
if ( ctx != NULL )
{
mbedtls_chacha20_free( &ctx->chacha20_ctx );
mbedtls_poly1305_free( &ctx->poly1305_ctx );
ctx->aad_len = 0U;
ctx->ciphertext_len = 0U;
ctx->state = CHACHAPOLY_STATE_INIT;
ctx->mode = MBEDTLS_CHACHAPOLY_ENCRYPT;
}
}
int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx,
const unsigned char key[32] )
{
int result;
if ( ( ctx == NULL ) || ( key == NULL ) )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
result = mbedtls_chacha20_setkey( &ctx->chacha20_ctx, key );
return( result );
}
int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx,
const unsigned char nonce[12],
mbedtls_chachapoly_mode_t mode )
{
int result;
unsigned char poly1305_key[64];
if ( ( ctx == NULL ) || ( nonce == NULL ) )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
/* Set counter = 0, will be update to 1 when generating Poly1305 key */
result = mbedtls_chacha20_starts( &ctx->chacha20_ctx, nonce, 0U );
if ( result != 0 )
goto cleanup;
/* Generate the Poly1305 key by getting the ChaCha20 keystream output with counter = 0.
* This is the same as encrypting a buffer of zeroes.
* Only the first 256-bits (32 bytes) of the key is used for Poly1305.
* The other 256 bits are discarded.
*/
memset( poly1305_key, 0, sizeof( poly1305_key ) );
result = mbedtls_chacha20_update( &ctx->chacha20_ctx, sizeof( poly1305_key ),
poly1305_key, poly1305_key );
if ( result != 0 )
goto cleanup;
result = mbedtls_poly1305_starts( &ctx->poly1305_ctx, poly1305_key );
if ( result == 0 )
{
ctx->aad_len = 0U;
ctx->ciphertext_len = 0U;
ctx->state = CHACHAPOLY_STATE_AAD;
ctx->mode = mode;
}
cleanup:
mbedtls_zeroize( poly1305_key, 64U );
return( result );
}
int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx,
size_t aad_len,
const unsigned char *aad )
{
if ( ctx == NULL )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
else if ( ( aad_len > 0U ) && ( aad == NULL ) )
{
/* aad pointer is allowed to be NULL if aad_len == 0 */
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
else if ( ctx->state != CHACHAPOLY_STATE_AAD )
{
return(MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
}
ctx->aad_len += aad_len;
return( mbedtls_poly1305_update( &ctx->poly1305_ctx, aad_len, aad ) );
}
int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx,
size_t len,
const unsigned char *input,
unsigned char *output )
{
if ( ( ctx == NULL ) || ( input == NULL ) || ( output == NULL ) )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
else if ( ( len > 0U ) && ( ( input == NULL ) || ( output == NULL ) ) )
{
/* input and output pointers are allowed to be NULL if len == 0 */
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
else if ( ( ctx->state != CHACHAPOLY_STATE_AAD ) &&
( ctx->state != CHACHAPOLY_STATE_CIPHERTEXT ) )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
}
if ( ctx->state == CHACHAPOLY_STATE_AAD )
{
ctx->state = CHACHAPOLY_STATE_CIPHERTEXT;
mbedtls_chachapoly_pad_aad( ctx );
}
ctx->ciphertext_len += len;
if ( ctx->mode == MBEDTLS_CHACHAPOLY_ENCRYPT )
{
/* Note: the following functions return an error only if one or more of
* the input pointers are NULL. Since we have checked their validity
* above, we can safety ignore the return value.
*/
(void) mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx, len, output );
}
else /* DECRYPT */
{
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx, len, input );
(void) mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
}
return( 0 );
}
int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx,
unsigned char mac[16] )
{
unsigned char len_block[16];
if ( ( ctx == NULL ) || ( mac == NULL ) )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_INPUT_DATA );
}
else if ( ctx->state == CHACHAPOLY_STATE_INIT )
{
return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
}
if ( ctx->state == CHACHAPOLY_STATE_AAD )
{
mbedtls_chachapoly_pad_aad( ctx );
}
else if ( ctx->state == CHACHAPOLY_STATE_CIPHERTEXT )
{
mbedtls_chachapoly_pad_ciphertext( ctx );
}
ctx->state = CHACHAPOLY_STATE_FINISHED;
/* The lengths of the AAD and ciphertext are processed by
* Poly1305 as the final 128-bit block, encoded as little-endian integers.
*/
len_block[0] = (unsigned char) ctx->aad_len;
len_block[1] = (unsigned char) ( ctx->aad_len >> 8 );
len_block[2] = (unsigned char) ( ctx->aad_len >> 16 );
len_block[3] = (unsigned char) ( ctx->aad_len >> 24 );
len_block[4] = (unsigned char) ( ctx->aad_len >> 32 );
len_block[5] = (unsigned char) ( ctx->aad_len >> 40 );
len_block[6] = (unsigned char) ( ctx->aad_len >> 48 );
len_block[7] = (unsigned char) ( ctx->aad_len >> 56 );
len_block[8] = (unsigned char) ctx->ciphertext_len;
len_block[9] = (unsigned char) ( ctx->ciphertext_len >> 8 );
len_block[10] = (unsigned char) ( ctx->ciphertext_len >> 16 );
len_block[11] = (unsigned char) ( ctx->ciphertext_len >> 24 );
len_block[12] = (unsigned char) ( ctx->ciphertext_len >> 32 );
len_block[13] = (unsigned char) ( ctx->ciphertext_len >> 40 );
len_block[14] = (unsigned char) ( ctx->ciphertext_len >> 48 );
len_block[15] = (unsigned char) ( ctx->ciphertext_len >> 56 );
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx, 16U, len_block );
(void) mbedtls_poly1305_finish( &ctx->poly1305_ctx, mac );
return( 0 );
}
int mbedtls_chachapoly_crypt_and_tag( mbedtls_chachapoly_context *ctx,
mbedtls_chachapoly_mode_t mode,
size_t length,
const unsigned char nonce[12],
const unsigned char *aad,
size_t aad_len,
const unsigned char *input,
unsigned char *output,
unsigned char tag[16] )
{
int result;
result = mbedtls_chachapoly_starts( ctx, nonce, mode );
if ( result != 0 )
goto cleanup;
result = mbedtls_chachapoly_update_aad( ctx, aad_len, aad );
if ( result != 0 )
goto cleanup;
result = mbedtls_chachapoly_update( ctx, length, input, output );
if ( result != 0 )
goto cleanup;
result = mbedtls_chachapoly_finish( ctx, tag );
cleanup:
return( result );
}
int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx,
size_t length,
const unsigned char nonce[12],
const unsigned char *aad,
size_t aad_len,
const unsigned char tag[16],
const unsigned char *input,
unsigned char *output )
{
int ret;
unsigned char check_tag[16];
size_t i;
int diff;
if( ( ret = mbedtls_chachapoly_crypt_and_tag( ctx,
MBEDTLS_CHACHAPOLY_DECRYPT, length, nonce,
aad, aad_len, input, output, check_tag ) ) != 0 )
{
return( ret );
}
/* Check tag in "constant-time" */
for( diff = 0, i = 0; i < sizeof( check_tag ); i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
{
mbedtls_zeroize( output, length );
return( MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED );
}
return( 0 );
}
#endif /* MBEDTLS_CHACHAPOLY_ALT */
#if defined(MBEDTLS_SELF_TEST)
static const unsigned char test_key[1][32] =
{
{
0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f
}
};
static const unsigned char test_nonce[1][12] =
{
{
0x07, 0x00, 0x00, 0x00, /* 32-bit common part */
0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47 /* 64-bit IV */
}
};
static const unsigned char test_aad[1][12] =
{
{
0x50, 0x51, 0x52, 0x53, 0xc0, 0xc1, 0xc2, 0xc3,
0xc4, 0xc5, 0xc6, 0xc7
}
};
static const size_t test_aad_len[1] =
{
12U
};
static const unsigned char test_input[1][114] =
{
{
0x4c, 0x61, 0x64, 0x69, 0x65, 0x73, 0x20, 0x61,
0x6e, 0x64, 0x20, 0x47, 0x65, 0x6e, 0x74, 0x6c,
0x65, 0x6d, 0x65, 0x6e, 0x20, 0x6f, 0x66, 0x20,
0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x61, 0x73,
0x73, 0x20, 0x6f, 0x66, 0x20, 0x27, 0x39, 0x39,
0x3a, 0x20, 0x49, 0x66, 0x20, 0x49, 0x20, 0x63,
0x6f, 0x75, 0x6c, 0x64, 0x20, 0x6f, 0x66, 0x66,
0x65, 0x72, 0x20, 0x79, 0x6f, 0x75, 0x20, 0x6f,
0x6e, 0x6c, 0x79, 0x20, 0x6f, 0x6e, 0x65, 0x20,
0x74, 0x69, 0x70, 0x20, 0x66, 0x6f, 0x72, 0x20,
0x74, 0x68, 0x65, 0x20, 0x66, 0x75, 0x74, 0x75,
0x72, 0x65, 0x2c, 0x20, 0x73, 0x75, 0x6e, 0x73,
0x63, 0x72, 0x65, 0x65, 0x6e, 0x20, 0x77, 0x6f,
0x75, 0x6c, 0x64, 0x20, 0x62, 0x65, 0x20, 0x69,
0x74, 0x2e
}
};
static const unsigned char test_output[1][114] =
{
{
0xd3, 0x1a, 0x8d, 0x34, 0x64, 0x8e, 0x60, 0xdb,
0x7b, 0x86, 0xaf, 0xbc, 0x53, 0xef, 0x7e, 0xc2,
0xa4, 0xad, 0xed, 0x51, 0x29, 0x6e, 0x08, 0xfe,
0xa9, 0xe2, 0xb5, 0xa7, 0x36, 0xee, 0x62, 0xd6,
0x3d, 0xbe, 0xa4, 0x5e, 0x8c, 0xa9, 0x67, 0x12,
0x82, 0xfa, 0xfb, 0x69, 0xda, 0x92, 0x72, 0x8b,
0x1a, 0x71, 0xde, 0x0a, 0x9e, 0x06, 0x0b, 0x29,
0x05, 0xd6, 0xa5, 0xb6, 0x7e, 0xcd, 0x3b, 0x36,
0x92, 0xdd, 0xbd, 0x7f, 0x2d, 0x77, 0x8b, 0x8c,
0x98, 0x03, 0xae, 0xe3, 0x28, 0x09, 0x1b, 0x58,
0xfa, 0xb3, 0x24, 0xe4, 0xfa, 0xd6, 0x75, 0x94,
0x55, 0x85, 0x80, 0x8b, 0x48, 0x31, 0xd7, 0xbc,
0x3f, 0xf4, 0xde, 0xf0, 0x8e, 0x4b, 0x7a, 0x9d,
0xe5, 0x76, 0xd2, 0x65, 0x86, 0xce, 0xc6, 0x4b,
0x61, 0x16
}
};
static const size_t test_input_len[1] =
{
114U
};
static const unsigned char test_mac[1][16] =
{
{
0x1a, 0xe1, 0x0b, 0x59, 0x4f, 0x09, 0xe2, 0x6a,
0x7e, 0x90, 0x2e, 0xcb, 0xd0, 0x60, 0x06, 0x91
}
};
int mbedtls_chachapoly_self_test( int verbose )
{
mbedtls_chachapoly_context ctx;
unsigned i;
int result;
unsigned char output[200];
unsigned char mac[16];
for ( i = 0U; i < 1U; i++ )
{
if ( verbose != 0 )
{
mbedtls_printf( " ChaCha20-Poly1305 test %u ", i );
}
mbedtls_chachapoly_init( &ctx );
result = mbedtls_chachapoly_setkey( &ctx, test_key[i] );
if ( result != 0 )
{
if ( verbose != 0 )
{
mbedtls_printf( "setkey() error code: %i\n", result );
}
return( -1 );
}
result = mbedtls_chachapoly_crypt_and_tag( &ctx,
MBEDTLS_CHACHAPOLY_ENCRYPT,
test_input_len[i],
test_nonce[i],
test_aad[i],
test_aad_len[i],
test_input[i],
output,
mac );
if ( result != 0 )
{
if ( verbose != 0 )
{
mbedtls_printf( "crypt_and_tag() error code: %i\n", result );
}
return( -1 );
}
if ( memcmp( output, test_output[i], test_input_len[i] ) != 0 )
{
if ( verbose != 0 )
{
mbedtls_printf( "failure (wrong output)\n" );
}
return( -1 );
}
if ( memcmp( mac, test_mac[i], 16U ) != 0 )
{
if ( verbose != 0 )
{
mbedtls_printf( "failure (wrong MAC)\n" );
}
return( -1 );
}
mbedtls_chachapoly_free( &ctx );
if ( verbose != 0 )
{
mbedtls_printf( "passed\n" );
}
}
if( verbose != 0 )
{
mbedtls_printf( "\n" );
}
return( 0 );
}
#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_CHACHAPOLY_C */
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