/*

 * Copyright (C) 2011-2012 Free Software Foundation, Inc.

 * Copyright (C) 2018 Red Hat, Inc.

 *

 * Author: Nikos Mavrogiannopoulos

 *

 * This file is part of GnuTLS.

 *

 * The GnuTLS is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

/*

 * The following code is an implementation of the AES-128-GCM cipher

 * using intel's AES instruction set.

 */

#include "errors.h"

#include "gnutls_int.h"

#include <gnutls/crypto.h>

#include "errors.h"

#include <aes-x86.h>

#include <x86-common.h>

#include <nettle/memxor.h>

#include <byteswap.h>

#define GCM_BLOCK_SIZE 16

/* GCM mode */

typedef struct {

  uint64_t hi, lo;

} u128;

/* This is the gcm128 structure used in openssl. It

 * is compatible with the included assembly code.

 */

struct gcm128_context {

  union {

    uint64_t u[2];

    uint32_t d[4];

    uint8_t c[16];

  } Yi, EKi, EK0, len, Xi, H;

  u128 Htable[16];

};

struct aes_gcm_ctx {

  AES_KEY expanded_key;

  struct gcm128_context gcm;

  unsigned finished;

  unsigned auth_finished;

  size_t rekey_counter;

};

void gcm_init_clmul(u128 Htable[16], const uint64_t Xi[2]);

void gcm_ghash_clmul(uint64_t Xi[2], const u128 Htable[16],

         const uint8_t * inp, size_t len);

void gcm_gmult_clmul(uint64_t Xi[2], const u128 Htable[16]);

static void aes_gcm_deinit(void *_ctx)

{

  struct aes_gcm_ctx *ctx = _ctx;

  zeroize_temp_key(ctx, sizeof(*ctx));

  gnutls_free(ctx);

}

static int

aes_gcm_cipher_init(gnutls_cipher_algorithm_t algorithm, void **_ctx, int enc)

{

  /* we use key size to distinguish */

  if (algorithm != GNUTLS_CIPHER_AES_128_GCM &&

      algorithm != GNUTLS_CIPHER_AES_192_GCM &&

      algorithm != GNUTLS_CIPHER_AES_256_GCM)

    return GNUTLS_E_INVALID_REQUEST;

  *_ctx = gnutls_calloc(1, sizeof(struct aes_gcm_ctx));

  if (*_ctx == NULL) {

    gnutls_assert();

    return GNUTLS_E_MEMORY_ERROR;

  }

  return 0;

}

static int

aes_gcm_cipher_setkey(void *_ctx, const void *userkey, size_t keysize)

{

  struct aes_gcm_ctx *ctx = _ctx;

  int ret;

  CHECK_AES_KEYSIZE(keysize);

  ret =

      aesni_set_encrypt_key(userkey, keysize * 8,

          ALIGN16(&ctx->expanded_key));

  if (ret != 0)

    return gnutls_assert_val(GNUTLS_E_ENCRYPTION_FAILED);

  aesni_ecb_encrypt(ctx->gcm.H.c, ctx->gcm.H.c,

        GCM_BLOCK_SIZE, ALIGN16(&ctx->expanded_key), 1);

  ctx->gcm.H.u[0] = bswap_64(ctx->gcm.H.u[0]);

  ctx->gcm.H.u[1] = bswap_64(ctx->gcm.H.u[1]);

  gcm_init_clmul(ctx->gcm.Htable, ctx->gcm.H.u);

  ctx->rekey_counter = 0;

  return 0;

}

static int aes_gcm_setiv(void *_ctx, const void *iv, size_t iv_size)

{

  struct aes_gcm_ctx *ctx = _ctx;

  if (iv_size != GCM_BLOCK_SIZE - 4)

    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  memset(ctx->gcm.Xi.c, 0, sizeof(ctx->gcm.Xi.c));

  memset(ctx->gcm.len.c, 0, sizeof(ctx->gcm.len.c));

  memcpy(ctx->gcm.Yi.c, iv, GCM_BLOCK_SIZE - 4);

  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 4] = 0;

  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 3] = 0;

  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 2] = 0;

  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 1] = 1;

  aesni_ecb_encrypt(ctx->gcm.Yi.c, ctx->gcm.EK0.c,

        GCM_BLOCK_SIZE, ALIGN16(&ctx->expanded_key), 1);

  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 1] = 2;

  ctx->finished = 0;

  ctx->auth_finished = 0;

  ctx->rekey_counter = 0;

  return 0;

}

static void

gcm_ghash(struct aes_gcm_ctx *ctx, const uint8_t * src, size_t src_size)

{

  size_t rest = src_size % GCM_BLOCK_SIZE;

  size_t aligned_size = src_size - rest;

  if (aligned_size > 0)

    gcm_ghash_clmul(ctx->gcm.Xi.u, ctx->gcm.Htable, src,

        aligned_size);

  if (rest > 0) {

    memxor(ctx->gcm.Xi.c, src + aligned_size, rest);

    gcm_gmult_clmul(ctx->gcm.Xi.u, ctx->gcm.Htable);

  }

}

static inline void

ctr_encrypt_last(struct aes_gcm_ctx *ctx, const uint8_t * src,

     uint8_t * dst, size_t pos, size_t length)

{

  uint8_t tmp[GCM_BLOCK_SIZE];

  uint8_t out[GCM_BLOCK_SIZE];

  memcpy(tmp, &src[pos], length);

  aesni_ctr32_encrypt_blocks(tmp, out, 1,

           ALIGN16(&ctx->expanded_key), ctx->gcm.Yi.c);

  memcpy(&dst[pos], out, length);

}

static int

aes_gcm_encrypt(void *_ctx, const void *src, size_t src_size,

    void *dst, size_t length)

{

  struct aes_gcm_ctx *ctx = _ctx;

  int blocks = src_size / GCM_BLOCK_SIZE;

  int exp_blocks = blocks * GCM_BLOCK_SIZE;

  int rest = src_size - (exp_blocks);

  uint32_t counter;

  int ret;

  if (unlikely(ctx->finished))

    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  if (unlikely(length < src_size))

    return gnutls_assert_val(GNUTLS_E_SHORT_MEMORY_BUFFER);

  ret = record_aes_gcm_encrypt_size(&ctx->rekey_counter, src_size);

  if (ret < 0) {

    return gnutls_assert_val(ret);

  }

  if (blocks > 0) {

    aesni_ctr32_encrypt_blocks(src, dst,

             blocks,

             ALIGN16(&ctx->expanded_key),

             ctx->gcm.Yi.c);

    counter = _gnutls_read_uint32(ctx->gcm.Yi.c + 12);

    counter += blocks;

    _gnutls_write_uint32(counter, ctx->gcm.Yi.c + 12);

  }

  if (rest > 0) {   /* last incomplete block */

    ctr_encrypt_last(ctx, src, dst, exp_blocks, rest);

    ctx->finished = 1;

  }

  gcm_ghash(ctx, dst, src_size);

  ctx->gcm.len.u[1] += src_size;

  return 0;

}

static int

aes_gcm_decrypt(void *_ctx, const void *src, size_t src_size,

    void *dst, size_t dst_size)

{

  struct aes_gcm_ctx *ctx = _ctx;

  int blocks = src_size / GCM_BLOCK_SIZE;

  int exp_blocks = blocks * GCM_BLOCK_SIZE;

  int rest = src_size - (exp_blocks);

  uint32_t counter;

  if (unlikely(ctx->finished))

    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  if (unlikely(dst_size < src_size))

    return gnutls_assert_val(GNUTLS_E_SHORT_MEMORY_BUFFER);

  gcm_ghash(ctx, src, src_size);

  ctx->gcm.len.u[1] += src_size;

  if (blocks > 0) {

    aesni_ctr32_encrypt_blocks(src, dst,

             blocks,

             ALIGN16(&ctx->expanded_key),

             ctx->gcm.Yi.c);

    counter = _gnutls_read_uint32(ctx->gcm.Yi.c + 12);

    counter += blocks;

    _gnutls_write_uint32(counter, ctx->gcm.Yi.c + 12);

  }

  if (rest > 0) {   /* last incomplete block */

    ctr_encrypt_last(ctx, src, dst, exp_blocks, rest);

    ctx->finished = 1;

  }

  return 0;

}

static int aes_gcm_auth(void *_ctx, const void *src, size_t src_size)

{

  struct aes_gcm_ctx *ctx = _ctx;

  if (unlikely(ctx->auth_finished))

    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  gcm_ghash(ctx, src, src_size);

  ctx->gcm.len.u[0] += src_size;

  if (src_size % GCM_BLOCK_SIZE != 0)

    ctx->auth_finished = 1;

  return 0;

}

static void aes_gcm_tag(void *_ctx, void *tag, size_t tagsize)

{

  struct aes_gcm_ctx *ctx = _ctx;

  uint8_t buffer[GCM_BLOCK_SIZE];

  uint64_t alen, clen;

  alen = ctx->gcm.len.u[0] * 8;

  clen = ctx->gcm.len.u[1] * 8;

  _gnutls_write_uint64(alen, buffer);

  _gnutls_write_uint64(clen, &buffer[8]);

  gcm_ghash_clmul(ctx->gcm.Xi.u, ctx->gcm.Htable, buffer, GCM_BLOCK_SIZE);

  ctx->gcm.Xi.u[0] ^= ctx->gcm.EK0.u[0];

  ctx->gcm.Xi.u[1] ^= ctx->gcm.EK0.u[1];

  memcpy(tag, ctx->gcm.Xi.c, MIN(GCM_BLOCK_SIZE, tagsize));

}

#include "aes-gcm-aead.h"

const gnutls_crypto_cipher_st _gnutls_aes_gcm_pclmul = {

  .init = aes_gcm_cipher_init,

  .setkey = aes_gcm_cipher_setkey,

  .setiv = aes_gcm_setiv,

  .aead_encrypt = aes_gcm_aead_encrypt,

  .aead_decrypt = aes_gcm_aead_decrypt,

  .encrypt = aes_gcm_encrypt,

  .decrypt = aes_gcm_decrypt,

  .deinit = aes_gcm_deinit,

  .tag = aes_gcm_tag,

  .auth = aes_gcm_auth,

};