📄 ltc_gcm.c
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/*
---------------------------------------------------------------------------
Copyright (c) 1998-2006, Brian Gladman, Worcester, UK. All rights reserved.
LICENSE TERMS
The free distribution and use of this software in both source and binary
form is allowed (with or without changes) provided that:
1. distributions of this source code include the above copyright
notice, this list of conditions and the following disclaimer;
2. distributions in binary form include the above copyright
notice, this list of conditions and the following disclaimer
in the documentation and/or other associated materials;
3. the copyright holder's name is not used to endorse products
built using this software without specific written permission.
ALTERNATIVELY, provided that this notice is retained in full, this product
may be distributed under the terms of the GNU General Public License (GPL),
in which case the provisions of the GPL apply INSTEAD OF those given above.
DISCLAIMER
This software is provided 'as is' with no explicit or implied warranties
in respect of its properties, including, but not limited to, correctness
and/or fitness for purpose.
---------------------------------------------------------------------------
Issue Date: 13/06/2006
This code has been derived from LibTomCrypt, the cryptographic library
authored by Tom St Denis. His contribution is hence acknowledged. This
code has been developed to obtain two independent implementations of the
combined AES encryption/authentication modes (CCM, GCM and EAX) in order
to be able to check test vectors before their publication.
*/
#include <string.h>
#include "ltc_gcm.h"
#define GCM_MODE_IV 0
#define GCM_MODE_AAD 1
#define GCM_MODE_TEXT 2
#define store_64h( x, y ) \
{ ( y )[0] = ( uint_8t ) ( ((x) >> 56) & 255 ); \
( y )[1] = ( uint_8t ) ( ((x) >> 48) & 255 ); \
( y )[2] = ( uint_8t ) ( ((x) >> 40) & 255 ); \
( y )[3] = ( uint_8t ) ( ((x) >> 32) & 255 ); \
( y )[4] = ( uint_8t ) ( ((x) >> 24) & 255 ); \
( y )[5] = ( uint_8t ) ( ((x) >> 16) & 255 ); \
( y )[6] = ( uint_8t ) ( ((x) >> 8) & 255 ); \
( y )[7] = ( uint_8t ) ( (x) & 255 ); \
}
#if defined( GCM_TABLES )
const uint_8t gcm_shift_table[2 * 256] =
{
0x00, 0x00, 0x01, 0xc2, 0x03, 0x84, 0x02, 0x46, 0x07, 0x08, 0x06, 0xca, 0x04, 0x8c, 0x05, 0x4e,
0x0e, 0x10, 0x0f, 0xd2, 0x0d, 0x94, 0x0c, 0x56, 0x09, 0x18, 0x08, 0xda, 0x0a, 0x9c, 0x0b, 0x5e,
0x1c, 0x20, 0x1d, 0xe2, 0x1f, 0xa4, 0x1e, 0x66, 0x1b, 0x28, 0x1a, 0xea, 0x18, 0xac, 0x19, 0x6e,
0x12, 0x30, 0x13, 0xf2, 0x11, 0xb4, 0x10, 0x76, 0x15, 0x38, 0x14, 0xfa, 0x16, 0xbc, 0x17, 0x7e,
0x38, 0x40, 0x39, 0x82, 0x3b, 0xc4, 0x3a, 0x06, 0x3f, 0x48, 0x3e, 0x8a, 0x3c, 0xcc, 0x3d, 0x0e,
0x36, 0x50, 0x37, 0x92, 0x35, 0xd4, 0x34, 0x16, 0x31, 0x58, 0x30, 0x9a, 0x32, 0xdc, 0x33, 0x1e,
0x24, 0x60, 0x25, 0xa2, 0x27, 0xe4, 0x26, 0x26, 0x23, 0x68, 0x22, 0xaa, 0x20, 0xec, 0x21, 0x2e,
0x2a, 0x70, 0x2b, 0xb2, 0x29, 0xf4, 0x28, 0x36, 0x2d, 0x78, 0x2c, 0xba, 0x2e, 0xfc, 0x2f, 0x3e,
0x70, 0x80, 0x71, 0x42, 0x73, 0x04, 0x72, 0xc6, 0x77, 0x88, 0x76, 0x4a, 0x74, 0x0c, 0x75, 0xce,
0x7e, 0x90, 0x7f, 0x52, 0x7d, 0x14, 0x7c, 0xd6, 0x79, 0x98, 0x78, 0x5a, 0x7a, 0x1c, 0x7b, 0xde,
0x6c, 0xa0, 0x6d, 0x62, 0x6f, 0x24, 0x6e, 0xe6, 0x6b, 0xa8, 0x6a, 0x6a, 0x68, 0x2c, 0x69, 0xee,
0x62, 0xb0, 0x63, 0x72, 0x61, 0x34, 0x60, 0xf6, 0x65, 0xb8, 0x64, 0x7a, 0x66, 0x3c, 0x67, 0xfe,
0x48, 0xc0, 0x49, 0x02, 0x4b, 0x44, 0x4a, 0x86, 0x4f, 0xc8, 0x4e, 0x0a, 0x4c, 0x4c, 0x4d, 0x8e,
0x46, 0xd0, 0x47, 0x12, 0x45, 0x54, 0x44, 0x96, 0x41, 0xd8, 0x40, 0x1a, 0x42, 0x5c, 0x43, 0x9e,
0x54, 0xe0, 0x55, 0x22, 0x57, 0x64, 0x56, 0xa6, 0x53, 0xe8, 0x52, 0x2a, 0x50, 0x6c, 0x51, 0xae,
0x5a, 0xf0, 0x5b, 0x32, 0x59, 0x74, 0x58, 0xb6, 0x5d, 0xf8, 0x5c, 0x3a, 0x5e, 0x7c, 0x5f, 0xbe,
0xe1, 0x00, 0xe0, 0xc2, 0xe2, 0x84, 0xe3, 0x46, 0xe6, 0x08, 0xe7, 0xca, 0xe5, 0x8c, 0xe4, 0x4e,
0xef, 0x10, 0xee, 0xd2, 0xec, 0x94, 0xed, 0x56, 0xe8, 0x18, 0xe9, 0xda, 0xeb, 0x9c, 0xea, 0x5e,
0xfd, 0x20, 0xfc, 0xe2, 0xfe, 0xa4, 0xff, 0x66, 0xfa, 0x28, 0xfb, 0xea, 0xf9, 0xac, 0xf8, 0x6e,
0xf3, 0x30, 0xf2, 0xf2, 0xf0, 0xb4, 0xf1, 0x76, 0xf4, 0x38, 0xf5, 0xfa, 0xf7, 0xbc, 0xf6, 0x7e,
0xd9, 0x40, 0xd8, 0x82, 0xda, 0xc4, 0xdb, 0x06, 0xde, 0x48, 0xdf, 0x8a, 0xdd, 0xcc, 0xdc, 0x0e,
0xd7, 0x50, 0xd6, 0x92, 0xd4, 0xd4, 0xd5, 0x16, 0xd0, 0x58, 0xd1, 0x9a, 0xd3, 0xdc, 0xd2, 0x1e,
0xc5, 0x60, 0xc4, 0xa2, 0xc6, 0xe4, 0xc7, 0x26, 0xc2, 0x68, 0xc3, 0xaa, 0xc1, 0xec, 0xc0, 0x2e,
0xcb, 0x70, 0xca, 0xb2, 0xc8, 0xf4, 0xc9, 0x36, 0xcc, 0x78, 0xcd, 0xba, 0xcf, 0xfc, 0xce, 0x3e,
0x91, 0x80, 0x90, 0x42, 0x92, 0x04, 0x93, 0xc6, 0x96, 0x88, 0x97, 0x4a, 0x95, 0x0c, 0x94, 0xce,
0x9f, 0x90, 0x9e, 0x52, 0x9c, 0x14, 0x9d, 0xd6, 0x98, 0x98, 0x99, 0x5a, 0x9b, 0x1c, 0x9a, 0xde,
0x8d, 0xa0, 0x8c, 0x62, 0x8e, 0x24, 0x8f, 0xe6, 0x8a, 0xa8, 0x8b, 0x6a, 0x89, 0x2c, 0x88, 0xee,
0x83, 0xb0, 0x82, 0x72, 0x80, 0x34, 0x81, 0xf6, 0x84, 0xb8, 0x85, 0x7a, 0x87, 0x3c, 0x86, 0xfe,
0xa9, 0xc0, 0xa8, 0x02, 0xaa, 0x44, 0xab, 0x86, 0xae, 0xc8, 0xaf, 0x0a, 0xad, 0x4c, 0xac, 0x8e,
0xa7, 0xd0, 0xa6, 0x12, 0xa4, 0x54, 0xa5, 0x96, 0xa0, 0xd8, 0xa1, 0x1a, 0xa3, 0x5c, 0xa2, 0x9e,
0xb5, 0xe0, 0xb4, 0x22, 0xb6, 0x64, 0xb7, 0xa6, 0xb2, 0xe8, 0xb3, 0x2a, 0xb1, 0x6c, 0xb0, 0xae,
0xbb, 0xf0, 0xba, 0x32, 0xb8, 0x74, 0xb9, 0xb6, 0xbc, 0xf8, 0xbd, 0x3a, 0xbf, 0x7c, 0xbe, 0xbe };
#endif
static void gcm_rightshift( uint_8t a[] )
{
int x;
for( x = 15; x > 0; x-- )
{
a[x] = ( a[x] >> 1 ) | ( (a[x - 1] << 7) & 0x80 );
}
a[0] >>= 1;
}
static const uint_8t mask[] = { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };
static const uint_8t poly[] = { 0x00, 0xe1 };
static void gcm_gf_mult( const uint_8t a[], const uint_8t b[], uint_8t c[] )
{
uint_8t zb[16], vb[16];
unsigned int x, y, z;
memset( zb, 0, 16 );
memcpy( vb, a, 16 );
for( x = 0; x < 128; x++ )
{
if( b[x >> 3] & mask[x & 7] )
for( y = 0; y < 16; y++ )
zb[y] ^= vb[y];
z = vb[15] & 0x01;
gcm_rightshift( vb );
vb[0] ^= poly[z];
}
memcpy( c, zb, 16 );
}
static void gcm_mult_h( gcm_state gcm[1], uint_8t ix[] )
{
uint_8t tb[16];
#ifdef GCM_TABLES
int x, y;
memcpy( tb, &gcm->gf_tab[0][ix[0]][0], 16 );
for( x = 1; x < 16; x++ )
for( y = 0; y < 16; y++ )
tb[y] ^= gcm->gf_tab[x][ix[x]][y];
#else
gcm_gf_mult( gcm->hh, ix, tb );
#endif
memcpy( ix, tb, 16 );
}
int gcm_init( const unsigned char key[], int key_len, gcm_state gcm[1] )
{
uint_8t bb[16];
#ifdef GCM_TABLES
int x, y, z, t;
#endif
if(aes_encrypt_key( key, key_len, gcm->ctx ) != EXIT_SUCCESS)
return EXIT_FAILURE;
memset( bb, 0, 16 );
aes_encrypt( bb, gcm->hh, gcm->ctx );
memset( gcm->buf, 0, sizeof(gcm->buf) );
memset( gcm->acc, 0, sizeof(gcm->acc) );
gcm->mode = GCM_MODE_IV;
gcm->iv_mode = 0;
gcm->bfr_len = 0;
gcm->auth_len = 0;
gcm->ptxt_len = 0;
#ifdef GCM_TABLES
memset( bb, 0, 16 );
for( y = 0; y < 256; y++ )
{
bb[0] = y;
gcm_gf_mult( gcm->hh, bb, &gcm->gf_tab[0][y][0] );
}
for( x = 1; x < 16; x++ )
{
for( y = 0; y < 256; y++ )
{
t = gcm->gf_tab[x - 1][y][15];
for( z = 15; z > 0; z-- )
gcm->gf_tab[x][y][z] = gcm->gf_tab[x - 1][y][z - 1];
gcm->gf_tab[x][y][0] = gcm_shift_table[t << 1];
gcm->gf_tab[x][y][1] ^= gcm_shift_table[( t << 1 ) + 1];
}
}
#endif
return EXIT_SUCCESS;
}
int gcm_add_iv( const unsigned char iv[], unsigned long iv_len, gcm_state gcm[1] )
{
uint_32t x, y;
if( gcm->mode != GCM_MODE_IV )
return EXIT_FAILURE;
if( gcm->bfr_len >= 16 || gcm->bfr_len < 0 )
return EXIT_FAILURE;
if( iv_len + gcm->bfr_len > 12 )
gcm->iv_mode |= 1;
for( x = 0; x < iv_len; x++ )
{
gcm->buf[gcm->bfr_len++] = *iv++;
if( gcm->bfr_len == 16 )
{
for( y = 0; y < 16; y++ )
gcm->acc[y] ^= gcm->buf[y];
gcm_mult_h( gcm, gcm->acc );
gcm->bfr_len = 0;
gcm->auth_len += 128;
}
}
return EXIT_SUCCESS;
}
int gcm_add_aad( const unsigned char data[], unsigned long data_len, gcm_state gcm[1] )
{
uint_32t x;
if( gcm->bfr_len > 16 || gcm->bfr_len < 0 )
return EXIT_FAILURE;
if( gcm->mode == GCM_MODE_IV )
{
if( gcm->iv_mode || gcm->bfr_len != 12 )
{
for( x = 0; x < (uint_32t) gcm->bfr_len; x++ )
gcm->acc[x] ^= gcm->buf[x];
if( gcm->bfr_len )
{
gcm->auth_len += gcm->bfr_len * 8;
gcm_mult_h( gcm, gcm->acc );
}
memset( gcm->buf, 0, 8 );
store_64h( gcm->auth_len, gcm->buf + 8 );
for( x = 0; x < 16; x++ )
gcm->acc[x] ^= gcm->buf[x];
gcm_mult_h( gcm, gcm->acc );
memcpy( gcm->ctr, gcm->acc, 16 );
memset( gcm->acc, 0, 16 );
}
else
{
memcpy( gcm->ctr, gcm->buf, 12 );
gcm->ctr[12] = 0;
gcm->ctr[13] = 0;
gcm->ctr[14] = 0;
gcm->ctr[15] = 1;
}
memcpy( gcm->ctr_0, gcm->ctr, 16 );
memset( gcm->buf, 0, 16 );
gcm->bfr_len = 0;
gcm->auth_len = 0;
gcm->mode = GCM_MODE_AAD;
}
if( gcm->mode != GCM_MODE_AAD || gcm->bfr_len >= 16 )
return EXIT_FAILURE;
for( x = 0; x < data_len; x++ )
{
gcm->acc[gcm->bfr_len++] ^= *data++;
if( gcm->bfr_len == 16 )
{
gcm_mult_h( gcm, gcm->acc );
gcm->bfr_len = 0;
gcm->auth_len += 128;
}
}
return EXIT_SUCCESS;
}
int gcm_process( unsigned char pt[], unsigned long pt_len, unsigned char ct[], int dir, gcm_state gcm[1] )
{
uint_32t x, y;
uint_8t b;
if( gcm->bfr_len > 16 || gcm->bfr_len < 0 )
return EXIT_FAILURE;
if( gcm->mode == GCM_MODE_AAD )
{
if( gcm->bfr_len )
{
gcm->auth_len += gcm->bfr_len * 8;
gcm_mult_h( gcm, gcm->acc );
}
for( y = 15; y >= 12; y-- )
if( ++gcm->ctr[y] & 255 )
break;
if( aes_encrypt( gcm->ctr, gcm->buf, gcm->ctx ) != EXIT_SUCCESS )
return EXIT_FAILURE;
gcm->bfr_len = 0;
gcm->mode = GCM_MODE_TEXT;
}
if( gcm->mode != GCM_MODE_TEXT )
return EXIT_FAILURE;
for( x = 0; x < pt_len; x++ )
{
if( gcm->bfr_len == 16 )
{
gcm->ptxt_len += 128;
gcm_mult_h( gcm, gcm->acc );
for( y = 15; y >= 12; y-- )
if( ++gcm->ctr[y] & 255 )
break;
if( aes_encrypt( gcm->ctr, gcm->buf, gcm->ctx ) != EXIT_SUCCESS )
return EXIT_FAILURE;
gcm->bfr_len = 0;
}
if( dir == GCM_ENCRYPT )
b = ct[x] = pt[x] ^ gcm->buf[gcm->bfr_len];
else
{
b = ct[x];
pt[x] = ct[x] ^ gcm->buf[gcm->bfr_len];
}
gcm->acc[gcm->bfr_len++] ^= b;
}
return EXIT_SUCCESS;
}
int gcm_reset( gcm_state gcm[1] )
{
memset( gcm->buf, 0, sizeof(gcm->buf) );
memset( gcm->acc, 0, sizeof(gcm->acc) );
gcm->mode = GCM_MODE_IV;
gcm->iv_mode = 0;
gcm->bfr_len = 0;
gcm->auth_len = 0;
gcm->ptxt_len = 0;
return EXIT_SUCCESS;
}
int gcm_done( unsigned char tag[], unsigned long *taglen, gcm_state gcm[1] )
{
uint_32t x;
if( gcm->bfr_len > 16 || gcm->bfr_len < 0 )
return EXIT_FAILURE;
if( gcm->mode != GCM_MODE_TEXT )
return EXIT_FAILURE;
if( gcm->bfr_len )
{
gcm->ptxt_len += gcm->bfr_len * 8;
gcm_mult_h( gcm, gcm->acc );
}
store_64h( gcm->auth_len, gcm->buf );
store_64h( gcm->ptxt_len, gcm->buf + 8 );
for( x = 0; x < 16; x++ )
gcm->acc[x] ^= gcm->buf[x];
gcm_mult_h( gcm, gcm->acc );
if( aes_encrypt( gcm->ctr_0, gcm->buf, gcm->ctx ) != EXIT_SUCCESS)
return EXIT_FAILURE;
for( x = 0; x < 16 && x < *taglen; x++ )
tag[x] = gcm->buf[x] ^ gcm->acc[x];
*taglen = x;
return EXIT_SUCCESS;
}
int gcm_memory( const unsigned char key[], unsigned long key_len,
const unsigned char iv[], unsigned long iv_len,
const unsigned char data[], unsigned long data_len,
unsigned char pt[], unsigned long pt_len,
unsigned char ct[],
unsigned char tag[], unsigned long taglen,
int dir, int *stat )
{
void *orig;
gcm_state *gcm;
int err, t_len = taglen;
orig = gcm = malloc( sizeof(*gcm) );
if( (err = gcm_init( key, key_len, gcm )) != EXIT_SUCCESS )
goto exit1;
if( (err = gcm_add_iv( iv, iv_len, gcm )) != EXIT_SUCCESS )
goto exit1;
if( (err = gcm_add_aad( data, data_len, gcm )) != EXIT_SUCCESS )
goto exit1;
if( (err = gcm_process( pt, pt_len, ct, dir, gcm )) != EXIT_SUCCESS )
goto exit1;
if(dir == 0)
err = gcm_done( tag, &t_len, gcm );
else
{ unsigned char *buf = malloc( taglen );
if(buf)
{
err = gcm_done( buf, &t_len, gcm );
*stat = ( memcmp( buf, tag, taglen ) == 0 ? EXIT_SUCCESS : EXIT_FAILURE );
free( buf );
}
else
err = EXIT_FAILURE;
}
exit1:
free( orig );
return err;
}
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