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/*
AES-GCM-128
Copyright (C) Stefan Metzmacher 2014
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "replace.h"
#include "lib/crypto/aes.h"
#include "lib/crypto/aes_gcm_128.h"
#include "lib/util/byteorder.h"
static inline void aes_gcm_128_inc32(uint8_t inout[AES_BLOCK_SIZE])
{
uint32_t v;
v = RIVAL(inout, AES_BLOCK_SIZE - 4);
v += 1;
RSIVAL(inout, AES_BLOCK_SIZE - 4, v);
}
static inline void aes_gcm_128_mul(const uint8_t x[AES_BLOCK_SIZE],
const uint8_t y[AES_BLOCK_SIZE],
uint8_t v[AES_BLOCK_SIZE],
uint8_t z[AES_BLOCK_SIZE])
{
uint8_t i;
/* 11100001 || 0^120 */
static const uint8_t r[AES_BLOCK_SIZE] = {
0xE1, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
};
memset(z, 0, AES_BLOCK_SIZE);
memcpy(v, y, AES_BLOCK_SIZE);
for (i = 0; i < AES_BLOCK_SIZE; i++) {
uint8_t mask;
for (mask = 0x80; mask != 0 ; mask >>= 1) {
uint8_t v_lsb = v[AES_BLOCK_SIZE-1] & 1;
if (x[i] & mask) {
aes_block_xor(z, v, z);
}
aes_block_rshift(v, v);
if (v_lsb != 0) {
aes_block_xor(v, r, v);
}
}
}
}
static inline void aes_gcm_128_ghash_block(struct aes_gcm_128_context *ctx,
const uint8_t in[AES_BLOCK_SIZE])
{
aes_block_xor(ctx->Y, in, ctx->y.block);
aes_gcm_128_mul(ctx->y.block, ctx->H, ctx->v.block, ctx->Y);
}
void aes_gcm_128_init(struct aes_gcm_128_context *ctx,
const uint8_t K[AES_BLOCK_SIZE],
const uint8_t IV[AES_GCM_128_IV_SIZE])
{
ZERO_STRUCTP(ctx);
AES_set_encrypt_key(K, 128, &ctx->aes_key);
/*
* Step 1: generate H (ctx->Y is the zero block here)
*/
AES_encrypt(ctx->Y, ctx->H, &ctx->aes_key);
/*
* Step 2: generate J0
*/
memcpy(ctx->J0, IV, AES_GCM_128_IV_SIZE);
aes_gcm_128_inc32(ctx->J0);
/*
* We need to prepare CB with J0.
*/
memcpy(ctx->CB, ctx->J0, AES_BLOCK_SIZE);
ctx->c.ofs = AES_BLOCK_SIZE;
}
static inline void aes_gcm_128_update_tmp(struct aes_gcm_128_context *ctx,
struct aes_gcm_128_tmp *tmp,
const uint8_t *v, size_t v_len)
{
tmp->total += v_len;
if (tmp->ofs > 0) {
size_t copy = MIN(AES_BLOCK_SIZE - tmp->ofs, v_len);
memcpy(tmp->block + tmp->ofs, v, copy);
tmp->ofs += copy;
v += copy;
v_len -= copy;
}
if (tmp->ofs == AES_BLOCK_SIZE) {
aes_gcm_128_ghash_block(ctx, tmp->block);
tmp->ofs = 0;
}
while (v_len >= AES_BLOCK_SIZE) {
aes_gcm_128_ghash_block(ctx, v);
v += AES_BLOCK_SIZE;
v_len -= AES_BLOCK_SIZE;
}
if (v_len == 0) {
return;
}
ZERO_STRUCT(tmp->block);
memcpy(tmp->block, v, v_len);
tmp->ofs = v_len;
}
void aes_gcm_128_updateA(struct aes_gcm_128_context *ctx,
const uint8_t *a, size_t a_len)
{
aes_gcm_128_update_tmp(ctx, &ctx->A, a, a_len);
}
void aes_gcm_128_updateC(struct aes_gcm_128_context *ctx,
const uint8_t *c, size_t c_len)
{
if (ctx->A.ofs > 0) {
aes_gcm_128_ghash_block(ctx, ctx->A.block);
ctx->A.ofs = 0;
}
aes_gcm_128_update_tmp(ctx, &ctx->C, c, c_len);
}
static inline void aes_gcm_128_crypt_tmp(struct aes_gcm_128_context *ctx,
struct aes_gcm_128_tmp *tmp,
uint8_t *m, size_t m_len)
{
tmp->total += m_len;
while (m_len > 0) {
if (tmp->ofs == AES_BLOCK_SIZE) {
aes_gcm_128_inc32(ctx->CB);
AES_encrypt(ctx->CB, tmp->block, &ctx->aes_key);
tmp->ofs = 0;
}
if (likely(tmp->ofs == 0 && m_len >= AES_BLOCK_SIZE)) {
aes_block_xor(m, tmp->block, m);
m += AES_BLOCK_SIZE;
m_len -= AES_BLOCK_SIZE;
aes_gcm_128_inc32(ctx->CB);
AES_encrypt(ctx->CB, tmp->block, &ctx->aes_key);
continue;
}
m[0] ^= tmp->block[tmp->ofs];
m += 1;
m_len -= 1;
tmp->ofs += 1;
}
}
void aes_gcm_128_crypt(struct aes_gcm_128_context *ctx,
uint8_t *m, size_t m_len)
{
aes_gcm_128_crypt_tmp(ctx, &ctx->c, m, m_len);
}
void aes_gcm_128_digest(struct aes_gcm_128_context *ctx,
uint8_t T[AES_BLOCK_SIZE])
{
if (ctx->A.ofs > 0) {
aes_gcm_128_ghash_block(ctx, ctx->A.block);
ctx->A.ofs = 0;
}
if (ctx->C.ofs > 0) {
aes_gcm_128_ghash_block(ctx, ctx->C.block);
ctx->C.ofs = 0;
}
RSBVAL(ctx->AC, 0, ctx->A.total * 8);
RSBVAL(ctx->AC, 8, ctx->C.total * 8);
aes_gcm_128_ghash_block(ctx, ctx->AC);
AES_encrypt(ctx->J0, ctx->c.block, &ctx->aes_key);
aes_block_xor(ctx->c.block, ctx->Y, T);
ZERO_STRUCTP(ctx);
}
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