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mbedtls/library/chachapoly.c
Manuel Pégourié-Gonnard 5ef92d309a chachapoly: adjust parameter order 
This module used (len, pointer) while (pointer, len) is more common in the
rest of the library, in particular it's what's used in the GCM API that
very comparable to it, so switch to (pointer, len) for consistency.

Note that the crypt_and_tag() and auth_decrypt() functions were already using
the same convention as GCM, so this also increases intra-module consistency.
2018-05-24 13:37:31 +02:00

534 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,
zeroes,
16U - partial_block_len );
}
}
/**
* \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,
zeroes,
16U - partial_block_len );
}
}
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,
const unsigned char *aad,
size_t aad_len )
{
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, aad_len ) );
}
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, output, len );
}
else /* DECRYPT */
{
(void) mbedtls_poly1305_update( &ctx->poly1305_ctx, input, len );
(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, len_block, 16U );
(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, aad_len );
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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