/* Copyright (c) 2019, Google Inc.

 *

 * Permission to use, copy, modify, and/or distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION

 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN

 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <openssl/base.h>

#include "../../internal.h"

#include "internal.h"

#if !defined(BORINGSSL_HAS_UINT128) && defined(OPENSSL_SSE2)

#include <emmintrin.h>

#endif

// This file contains a constant-time implementation of GHASH based on the notes

// in https://bearssl.org/constanttime.html#ghash-for-gcm and the reduction

// algorithm described in

// https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf.

//

// Unlike the BearSSL notes, we use uint128_t in the 64-bit implementation. Our

// primary compilers (clang, clang-cl, and gcc) all support it. MSVC will run

// the 32-bit implementation, but we can use its intrinsics if necessary.

#if defined(BORINGSSL_HAS_UINT128)

static void gcm_mul64_nohw(uint64_t *out_lo, uint64_t *out_hi, uint64_t a,

                           uint64_t b) {

  // One term every four bits means the largest term is 64/4 = 16, which barely

  // overflows into the next term. Using one term every five bits would cost 25

  // multiplications instead of 16. It is faster to mask off the bottom four

  // bits of |a|, giving a largest term of 60/4 = 15, and apply the bottom bits

  // separately.

  uint64_t a0 = a & UINT64_C(0x1111111111111110);

  uint64_t a1 = a & UINT64_C(0x2222222222222220);

  uint64_t a2 = a & UINT64_C(0x4444444444444440);

  uint64_t a3 = a & UINT64_C(0x8888888888888880);

  uint64_t b0 = b & UINT64_C(0x1111111111111111);

  uint64_t b1 = b & UINT64_C(0x2222222222222222);

  uint64_t b2 = b & UINT64_C(0x4444444444444444);

  uint64_t b3 = b & UINT64_C(0x8888888888888888);

  uint128_t c0 = (a0 * (uint128_t)b0) ^ (a1 * (uint128_t)b3) ^

                 (a2 * (uint128_t)b2) ^ (a3 * (uint128_t)b1);

  uint128_t c1 = (a0 * (uint128_t)b1) ^ (a1 * (uint128_t)b0) ^

                 (a2 * (uint128_t)b3) ^ (a3 * (uint128_t)b2);

  uint128_t c2 = (a0 * (uint128_t)b2) ^ (a1 * (uint128_t)b1) ^

                 (a2 * (uint128_t)b0) ^ (a3 * (uint128_t)b3);

  uint128_t c3 = (a0 * (uint128_t)b3) ^ (a1 * (uint128_t)b2) ^

                 (a2 * (uint128_t)b1) ^ (a3 * (uint128_t)b0);

  // Multiply the bottom four bits of |a| with |b|.

  uint64_t a0_mask = UINT64_C(0) - (a & 1);

  uint64_t a1_mask = UINT64_C(0) - ((a >> 1) & 1);

  uint64_t a2_mask = UINT64_C(0) - ((a >> 2) & 1);

  uint64_t a3_mask = UINT64_C(0) - ((a >> 3) & 1);

  uint128_t extra = (a0_mask & b) ^ ((uint128_t)(a1_mask & b) << 1) ^

                    ((uint128_t)(a2_mask & b) << 2) ^

                    ((uint128_t)(a3_mask & b) << 3);

  *out_lo = (((uint64_t)c0) & UINT64_C(0x1111111111111111)) ^

            (((uint64_t)c1) & UINT64_C(0x2222222222222222)) ^

            (((uint64_t)c2) & UINT64_C(0x4444444444444444)) ^

            (((uint64_t)c3) & UINT64_C(0x8888888888888888)) ^ ((uint64_t)extra);

  *out_hi = (((uint64_t)(c0 >> 64)) & UINT64_C(0x1111111111111111)) ^

            (((uint64_t)(c1 >> 64)) & UINT64_C(0x2222222222222222)) ^

            (((uint64_t)(c2 >> 64)) & UINT64_C(0x4444444444444444)) ^

            (((uint64_t)(c3 >> 64)) & UINT64_C(0x8888888888888888)) ^

            ((uint64_t)(extra >> 64));

}

#elif defined(OPENSSL_SSE2)

static __m128i gcm_mul32_nohw(uint32_t a, uint32_t b) {

  // One term every four bits means the largest term is 32/4 = 8, which does not

  // overflow into the next term.

  __m128i aa = _mm_setr_epi32(a, 0, a, 0);

  __m128i bb = _mm_setr_epi32(b, 0, b, 0);

  __m128i a0a0 =

      _mm_and_si128(aa, _mm_setr_epi32(0x11111111, 0, 0x11111111, 0));

  __m128i a2a2 =

      _mm_and_si128(aa, _mm_setr_epi32(0x44444444, 0, 0x44444444, 0));

  __m128i b0b1 =

      _mm_and_si128(bb, _mm_setr_epi32(0x11111111, 0, 0x22222222, 0));

  __m128i b2b3 =

      _mm_and_si128(bb, _mm_setr_epi32(0x44444444, 0, 0x88888888, 0));

  __m128i c0c1 =

      _mm_xor_si128(_mm_mul_epu32(a0a0, b0b1), _mm_mul_epu32(a2a2, b2b3));

  __m128i c2c3 =

      _mm_xor_si128(_mm_mul_epu32(a2a2, b0b1), _mm_mul_epu32(a0a0, b2b3));

  __m128i a1a1 =

      _mm_and_si128(aa, _mm_setr_epi32(0x22222222, 0, 0x22222222, 0));

  __m128i a3a3 =

      _mm_and_si128(aa, _mm_setr_epi32(0x88888888, 0, 0x88888888, 0));

  __m128i b3b0 =

      _mm_and_si128(bb, _mm_setr_epi32(0x88888888, 0, 0x11111111, 0));

  __m128i b1b2 =

      _mm_and_si128(bb, _mm_setr_epi32(0x22222222, 0, 0x44444444, 0));

  c0c1 = _mm_xor_si128(c0c1, _mm_mul_epu32(a1a1, b3b0));

  c0c1 = _mm_xor_si128(c0c1, _mm_mul_epu32(a3a3, b1b2));

  c2c3 = _mm_xor_si128(c2c3, _mm_mul_epu32(a3a3, b3b0));

  c2c3 = _mm_xor_si128(c2c3, _mm_mul_epu32(a1a1, b1b2));

  c0c1 = _mm_and_si128(

      c0c1, _mm_setr_epi32(0x11111111, 0x11111111, 0x22222222, 0x22222222));

  c2c3 = _mm_and_si128(

      c2c3, _mm_setr_epi32(0x44444444, 0x44444444, 0x88888888, 0x88888888));

  c0c1 = _mm_xor_si128(c0c1, c2c3);

  // c0 ^= c1

  c0c1 = _mm_xor_si128(c0c1, _mm_srli_si128(c0c1, 8));

  return c0c1;

}

static void gcm_mul64_nohw(uint64_t *out_lo, uint64_t *out_hi, uint64_t a,

                           uint64_t b) {

  uint32_t a0 = a & 0xffffffff;

  uint32_t a1 = a >> 32;

  uint32_t b0 = b & 0xffffffff;

  uint32_t b1 = b >> 32;

  // Karatsuba multiplication.

  __m128i lo = gcm_mul32_nohw(a0, b0);

  __m128i hi = gcm_mul32_nohw(a1, b1);

  __m128i mid = gcm_mul32_nohw(a0 ^ a1, b0 ^ b1);

  mid = _mm_xor_si128(mid, lo);

  mid = _mm_xor_si128(mid, hi);

  __m128i ret = _mm_unpacklo_epi64(lo, hi);

  mid = _mm_slli_si128(mid, 4);

  mid = _mm_and_si128(mid, _mm_setr_epi32(0, 0xffffffff, 0xffffffff, 0));

  ret = _mm_xor_si128(ret, mid);

  memcpy(out_lo, &ret, 8);

  memcpy(out_hi, ((char*)&ret) + 8, 8);

}

#else  // !BORINGSSL_HAS_UINT128 && !OPENSSL_SSE2

static uint64_t gcm_mul32_nohw(uint32_t a, uint32_t b) {

  // One term every four bits means the largest term is 32/4 = 8, which does not

  // overflow into the next term.

  uint32_t a0 = a & 0x11111111;

  uint32_t a1 = a & 0x22222222;

  uint32_t a2 = a & 0x44444444;

  uint32_t a3 = a & 0x88888888;

  uint32_t b0 = b & 0x11111111;

  uint32_t b1 = b & 0x22222222;

  uint32_t b2 = b & 0x44444444;

  uint32_t b3 = b & 0x88888888;

  uint64_t c0 = (a0 * (uint64_t)b0) ^ (a1 * (uint64_t)b3) ^

                (a2 * (uint64_t)b2) ^ (a3 * (uint64_t)b1);

  uint64_t c1 = (a0 * (uint64_t)b1) ^ (a1 * (uint64_t)b0) ^

                (a2 * (uint64_t)b3) ^ (a3 * (uint64_t)b2);

  uint64_t c2 = (a0 * (uint64_t)b2) ^ (a1 * (uint64_t)b1) ^

                (a2 * (uint64_t)b0) ^ (a3 * (uint64_t)b3);

  uint64_t c3 = (a0 * (uint64_t)b3) ^ (a1 * (uint64_t)b2) ^

                (a2 * (uint64_t)b1) ^ (a3 * (uint64_t)b0);

  return (c0 & UINT64_C(0x1111111111111111)) |

         (c1 & UINT64_C(0x2222222222222222)) |

         (c2 & UINT64_C(0x4444444444444444)) |

         (c3 & UINT64_C(0x8888888888888888));

}

static void gcm_mul64_nohw(uint64_t *out_lo, uint64_t *out_hi, uint64_t a,

                           uint64_t b) {

  uint32_t a0 = a & 0xffffffff;

  uint32_t a1 = a >> 32;

  uint32_t b0 = b & 0xffffffff;

  uint32_t b1 = b >> 32;

  // Karatsuba multiplication.

  uint64_t lo = gcm_mul32_nohw(a0, b0);

  uint64_t hi = gcm_mul32_nohw(a1, b1);

  uint64_t mid = gcm_mul32_nohw(a0 ^ a1, b0 ^ b1) ^ lo ^ hi;

  *out_lo = lo ^ (mid << 32);

  *out_hi = hi ^ (mid >> 32);

}

#endif  // BORINGSSL_HAS_UINT128

void gcm_init_nohw(u128 Htable[16], const uint64_t Xi[2]) {

  // We implement GHASH in terms of POLYVAL, as described in RFC 8452. This

  // avoids a shift by 1 in the multiplication, needed to account for bit

  // reversal losing a bit after multiplication, that is,

  // rev128(X) * rev128(Y) = rev255(X*Y).

  //

  // Per Appendix A, we run mulX_POLYVAL. Note this is the same transformation

  // applied by |gcm_init_clmul|, etc. Note |Xi| has already been byteswapped.

  //

  // See also slide 16 of

  // https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf

  Htable[0].lo = Xi[1];

  Htable[0].hi = Xi[0];

  uint64_t carry = Htable[0].hi >> 63;

  carry = 0u - carry;

  Htable[0].hi <<= 1;

  Htable[0].hi |= Htable[0].lo >> 63;

  Htable[0].lo <<= 1;

  // The irreducible polynomial is 1 + x^121 + x^126 + x^127 + x^128, so we

  // conditionally add 0xc200...0001.

  Htable[0].lo ^= carry & 1;

  Htable[0].hi ^= carry & UINT64_C(0xc200000000000000);

  // This implementation does not use the rest of |Htable|.

}

static void gcm_polyval_nohw(uint64_t Xi[2], const u128 *H) {

  // Karatsuba multiplication. The product of |Xi| and |H| is stored in |r0|

  // through |r3|. Note there is no byte or bit reversal because we are

  // evaluating POLYVAL.

  uint64_t r0, r1;

  gcm_mul64_nohw(&r0, &r1, Xi[0], H->lo);

  uint64_t r2, r3;

  gcm_mul64_nohw(&r2, &r3, Xi[1], H->hi);

  uint64_t mid0, mid1;

  gcm_mul64_nohw(&mid0, &mid1, Xi[0] ^ Xi[1], H->hi ^ H->lo);

  mid0 ^= r0 ^ r2;

  mid1 ^= r1 ^ r3;

  r2 ^= mid1;

  r1 ^= mid0;

  // Now we multiply our 256-bit result by x^-128 and reduce. |r2| and

  // |r3| shifts into position and we must multiply |r0| and |r1| by x^-128. We

  // have:

  //

  //       1 = x^121 + x^126 + x^127 + x^128

  //  x^-128 = x^-7 + x^-2 + x^-1 + 1

  //

  // This is the GHASH reduction step, but with bits flowing in reverse.

  // The x^-7, x^-2, and x^-1 terms shift bits past x^0, which would require

  // another reduction steps. Instead, we gather the excess bits, incorporate

  // them into |r0| and |r1| and reduce once. See slides 17-19

  // of https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf.

  r1 ^= (r0 << 63) ^ (r0 << 62) ^ (r0 << 57);

  // 1

  r2 ^= r0;

  r3 ^= r1;

  // x^-1

  r2 ^= r0 >> 1;

  r2 ^= r1 << 63;

  r3 ^= r1 >> 1;

  // x^-2

  r2 ^= r0 >> 2;

  r2 ^= r1 << 62;

  r3 ^= r1 >> 2;

  // x^-7

  r2 ^= r0 >> 7;

  r2 ^= r1 << 57;

  r3 ^= r1 >> 7;

  Xi[0] = r2;

  Xi[1] = r3;

}

void gcm_gmult_nohw(uint8_t Xi[16], const u128 Htable[16]) {

  uint64_t swapped[2];

  swapped[0] = CRYPTO_load_u64_be(Xi + 8);

  swapped[1] = CRYPTO_load_u64_be(Xi);

  gcm_polyval_nohw(swapped, &Htable[0]);

  CRYPTO_store_u64_be(Xi, swapped[1]);

  CRYPTO_store_u64_be(Xi + 8, swapped[0]);

}

void gcm_ghash_nohw(uint8_t Xi[16], const u128 Htable[16], const uint8_t *inp,

                    size_t len) {

  uint64_t swapped[2];

  swapped[0] = CRYPTO_load_u64_be(Xi + 8);

  swapped[1] = CRYPTO_load_u64_be(Xi);

  while (len >= 16) {

    swapped[0] ^= CRYPTO_load_u64_be(inp + 8);

    swapped[1] ^= CRYPTO_load_u64_be(inp);

    gcm_polyval_nohw(swapped, &Htable[0]);

    inp += 16;

    len -= 16;

  }

  CRYPTO_store_u64_be(Xi, swapped[1]);

  CRYPTO_store_u64_be(Xi + 8, swapped[0]);

}