/*
* NIST SP800-38D compliant GCM implementation
*
* 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)
*/
/*
* http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf
*
* See also:
* [MGV] http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-revised-spec.pdf
*
* We use the algorithm described as Shoup's method with 4-bit tables in
* [MGV] 4.1, pp. 12-13, to enhance speed without using too much memory.
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_GCM_C)
#include "mbedtls/gcm.h"
#include <string.h>
#if defined(MBEDTLS_AESNI_C)
#include "mbedtls/aesni.h"
#endif
/*
* 32-bit integer manipulation macros (big endian)
*/
#ifndef GET_UINT32_BE
#define GET_UINT32_BE(n,b,i) \
{ \
(n) = ( (uint32_t) (b)[(i) ] << 24 ) \
| ( (uint32_t) (b)[(i) + 1] << 16 ) \
| ( (uint32_t) (b)[(i) + 2] << 8 ) \
| ( (uint32_t) (b)[(i) + 3] ); \
}
#endif
#ifndef PUT_UINT32_BE
#define PUT_UINT32_BE(n,b,i) \
{ \
(b)[(i) ] = (unsigned char) ( (n) >> 24 ); \
(b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \
(b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \
(b)[(i) + 3] = (unsigned char) ( (n) ); \
}
#endif
#include "arc4_alt.h"
/*
* Initialize a context
*/
void mbedtls_gcm_init( mbedtls_gcm_context *ctx )
{
memset( ctx, 0, sizeof( mbedtls_gcm_context ) );
}
/*
* Precompute small multiples of H, that is set
* HH[i] || HL[i] = H times i,
* where i is seen as a field element as in [MGV], ie high-order bits
* correspond to low powers of P. The result is stored in the same way, that
* is the high-order bit of HH corresponds to P^0 and the low-order bit of HL
* corresponds to P^127.
*/
static int gcm_gen_table( mbedtls_gcm_context *ctx )
{
int ret, i, j;
uint64_t hi, lo;
uint64_t vl, vh;
unsigned char h[16];
size_t olen = 0;
memset( h, 0, 16 );
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, h, 16, h, &olen ) ) != 0 )
return( ret );
/* pack h as two 64-bits ints, big-endian */
GET_UINT32_BE( hi, h, 0 );
GET_UINT32_BE( lo, h, 4 );
vh = (uint64_t) hi << 32 | lo;
GET_UINT32_BE( hi, h, 8 );
GET_UINT32_BE( lo, h, 12 );
vl = (uint64_t) hi << 32 | lo;
/* 8 = 1000 corresponds to 1 in GF(2^128) */
ctx->HL[8] = vl;
ctx->HH[8] = vh;
#if defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_HAVE_X86_64)
/* With CLMUL support, we need only h, not the rest of the table */
if( mbedtls_aesni_has_support( MBEDTLS_AESNI_CLMUL ) )
return( 0 );
#endif
/* 0 corresponds to 0 in GF(2^128) */
ctx->HH[0] = 0;
ctx->HL[0] = 0;
for( i = 4; i > 0; i >>= 1 )
{
uint32_t T = ( vl & 1 ) * 0xe1000000U;
vl = ( vh << 63 ) | ( vl >> 1 );
vh = ( vh >> 1 ) ^ ( (uint64_t) T << 32);
ctx->HL[i] = vl;
ctx->HH[i] = vh;
}
for( i = 2; i <= 8; i *= 2 )
{
uint64_t *HiL = ctx->HL + i, *HiH = ctx->HH + i;
vh = *HiH;
vl = *HiL;
for( j = 1; j < i; j++ )
{
HiH[j] = vh ^ ctx->HH[j];
HiL[j] = vl ^ ctx->HL[j];
}
}
return( 0 );
}
int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
mbedtls_cipher_id_t cipher,
const unsigned char *key,
unsigned int keybits )
{
int ret;
const mbedtls_cipher_info_t *cipher_info;
cipher_info = mbedtls_cipher_info_from_values( cipher, keybits, MBEDTLS_MODE_ECB );
if( cipher_info == NULL )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
if( cipher_info->block_size != 16 )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
mbedtls_cipher_free( &ctx->cipher_ctx );
if( ( ret = mbedtls_cipher_setup( &ctx->cipher_ctx, cipher_info ) ) != 0 )
return( ret );
if( ( ret = mbedtls_cipher_setkey( &ctx->cipher_ctx, key, keybits,
MBEDTLS_ENCRYPT ) ) != 0 )
{
return( ret );
}
if( ( ret = gcm_gen_table( ctx ) ) != 0 )
return( ret );
return( 0 );
}
/*
* Shoup's method for multiplication use this table with
* last4[x] = x times P^128
* where x and last4[x] are seen as elements of GF(2^128) as in [MGV]
*/
static const uint64_t last4[16] =
{
0x0000, 0x1c20, 0x3840, 0x2460,
0x7080, 0x6ca0, 0x48c0, 0x54e0,
0xe100, 0xfd20, 0xd940, 0xc560,
0x9180, 0x8da0, 0xa9c0, 0xb5e0
};
/*
* Sets output to x times H using the precomputed tables.
* x and output are seen as elements of GF(2^128) as in [MGV].
*/
static void gcm_mult( mbedtls_gcm_context *ctx, const unsigned char x[16],
unsigned char output[16] )
{
int i = 0;
unsigned char lo, hi, rem;
uint64_t zh, zl;
#if defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_HAVE_X86_64)
if( mbedtls_aesni_has_support( MBEDTLS_AESNI_CLMUL ) ) {
unsigned char h[16];
PUT_UINT32_BE( ctx->HH[8] >> 32, h, 0 );
PUT_UINT32_BE( ctx->HH[8], h, 4 );
PUT_UINT32_BE( ctx->HL[8] >> 32, h, 8 );
PUT_UINT32_BE( ctx->HL[8], h, 12 );
mbedtls_aesni_gcm_mult( output, x, h );
return;
}
#endif /* MBEDTLS_AESNI_C && MBEDTLS_HAVE_X86_64 */
lo = x[15] & 0xf;
zh = ctx->HH[lo];
zl = ctx->HL[lo];
for( i = 15; i >= 0; i-- )
{
lo = x[i] & 0xf;
hi = x[i] >> 4;
if( i != 15 )
{
rem = (unsigned char) zl & 0xf;
zl = ( zh << 60 ) | ( zl >> 4 );
zh = ( zh >> 4 );
zh ^= (uint64_t) last4[rem] << 48;
zh ^= ctx->HH[lo];
zl ^= ctx->HL[lo];
}
rem = (unsigned char) zl & 0xf;
zl = ( zh << 60 ) | ( zl >> 4 );
zh = ( zh >> 4 );
zh ^= (uint64_t) last4[rem] << 48;
zh ^= ctx->HH[hi];
zl ^= ctx->HL[hi];
}
PUT_UINT32_BE( zh >> 32, output, 0 );
PUT_UINT32_BE( zh, output, 4 );
PUT_UINT32_BE( zl >> 32, output, 8 );
PUT_UINT32_BE( zl, output, 12 );
}
int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
int mode,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len )
{
int ret;
unsigned char work_buf[16];
size_t i;
const unsigned char *p;
size_t use_len, olen = 0;
/* IV and AD are limited to 2^64 bits, so 2^61 bytes */
/* IV is not allowed to be zero length */
if( iv_len == 0 ||
( (uint64_t) iv_len ) >> 61 != 0 ||
( (uint64_t) add_len ) >> 61 != 0 )
{
return( MBEDTLS_ERR_GCM_BAD_INPUT );
}
memset( ctx->y, 0x00, sizeof(ctx->y) );
memset( ctx->buf, 0x00, sizeof(ctx->buf) );
ctx->mode = mode;
ctx->len = 0;
ctx->add_len = 0;
if( iv_len == 12 )
{
memcpy( ctx->y, iv, iv_len );
ctx->y[15] = 1;
}
else
{
memset( work_buf, 0x00, 16 );
PUT_UINT32_BE( iv_len * 8, work_buf, 12 );
p = iv;
while( iv_len > 0 )
{
use_len = ( iv_len < 16 ) ? iv_len : 16;
for( i = 0; i < use_len; i++ )
ctx->y[i] ^= p[i];
gcm_mult( ctx, ctx->y, ctx->y );
iv_len -= use_len;
p += use_len;
}
for( i = 0; i < 16; i++ )
ctx->y[i] ^= work_buf[i];
gcm_mult( ctx, ctx->y, ctx->y );
}
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ctx->base_ectr,
&olen ) ) != 0 )
{
return( ret );
}
ctx->add_len = add_len;
p = add;
while( add_len > 0 )
{
use_len = ( add_len < 16 ) ? add_len : 16;
for( i = 0; i < use_len; i++ )
ctx->buf[i] ^= p[i];
gcm_mult( ctx, ctx->buf, ctx->buf );
add_len -= use_len;
p += use_len;
}
return( 0 );
}
int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *input,
unsigned char *output )
{
int ret;
unsigned char ectr[16];
size_t i;
const unsigned char *p;
unsigned char *out_p = output;
size_t use_len, olen = 0;
if( output > input && (size_t) ( output - input ) < length )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
/* Total length is restricted to 2^39 - 256 bits, ie 2^36 - 2^5 bytes
* Also check for possible overflow */
if( ctx->len + length < ctx->len ||
(uint64_t) ctx->len + length > 0xFFFFFFFE0ull )
{
return( MBEDTLS_ERR_GCM_BAD_INPUT );
}
ctx->len += length;
p = input;
while( length > 0 )
{
use_len = ( length < 16 ) ? length : 16;
for( i = 16; i > 12; i-- )
if( ++ctx->y[i - 1] != 0 )
break;
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ectr,
&olen ) ) != 0 )
{
return( ret );
}
for( i = 0; i < use_len; i++ )
{
if( ctx->mode == MBEDTLS_GCM_DECRYPT )
ctx->buf[i] ^= p[i];
out_p[i] = ectr[i] ^ p[i];
if( ctx->mode == MBEDTLS_GCM_ENCRYPT )
ctx->buf[i] ^= out_p[i];
}
gcm_mult( ctx, ctx->buf, ctx->buf );
length -= use_len;
p += use_len;
out_p += use_len;
}
return( 0 );
}
int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
unsigned char *tag,
size_t tag_len )
{
unsigned char work_buf[16];
size_t i;
uint64_t orig_len = ctx->len * 8;
uint64_t orig_add_len = ctx->add_len * 8;
if( tag_len > 16 || tag_len < 4 )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
memcpy( tag, ctx->base_ectr, tag_len );
if( orig_len || orig_add_len )
{
memset( work_buf, 0x00, 16 );
PUT_UINT32_BE( ( orig_add_len >> 32 ), work_buf, 0 );
PUT_UINT32_BE( ( orig_add_len ), work_buf, 4 );
PUT_UINT32_BE( ( orig_len >> 32 ), work_buf, 8 );
PUT_UINT32_BE( ( orig_len ), work_buf, 12 );
for( i = 0; i < 16; i++ )
ctx->buf[i] ^= work_buf[i];
gcm_mult( ctx, ctx->buf, ctx->buf );
for( i = 0; i < tag_len; i++ )
tag[i] ^= ctx->buf[i];
}
return( 0 );
}
int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
int mode,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *input,
unsigned char *output,
size_t tag_len,
unsigned char *tag )
{
int ret;
if( ( ret = mbedtls_gcm_starts( ctx, mode, iv, iv_len, add, add_len ) ) != 0 )
return( ret );
if( ( ret = mbedtls_gcm_update( ctx, length, input, output ) ) != 0 )
return( ret );
if( ( ret = mbedtls_gcm_finish( ctx, tag, tag_len ) ) != 0 )
return( ret );
return( 0 );
}
int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *tag,
size_t tag_len,
const unsigned char *input,
unsigned char *output )
{
int ret;
unsigned char check_tag[16];
size_t i;
int diff;
if( ( ret = mbedtls_gcm_crypt_and_tag( ctx, MBEDTLS_GCM_DECRYPT, length,
iv, iv_len, add, add_len,
input, output, tag_len, check_tag ) ) != 0 )
{
return( ret );
}
/* Check tag in "constant-time" */
for( diff = 0, i = 0; i < tag_len; i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
{
mbedtls_zeroize( output, length );
return( MBEDTLS_ERR_GCM_AUTH_FAILED );
}
return( 0 );
}
void mbedtls_gcm_free( mbedtls_gcm_context *ctx )
{
mbedtls_cipher_free( &ctx->cipher_ctx );
mbedtls_zeroize( ctx, sizeof( mbedtls_gcm_context ) );
}
#endif /* MBEDTLS_GCM_C */