text: /* 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 <CNIOBoringSSL_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 RFC8452. 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(uint64_t Xi[2], const u128 Htable[16]) {
    uint64_t swapped[2];
    swapped[0] = CRYPTO_bswap8(Xi[1]);
    swapped[1] = CRYPTO_bswap8(Xi[0]);
    gcm_polyval_nohw(swapped, &Htable[0]);
    Xi[0] = CRYPTO_bswap8(swapped[1]);
    Xi[1] = CRYPTO_bswap8(swapped[0]);
  }
  
  void gcm_ghash_nohw(uint64_t Xi[2], const u128 Htable[16], const uint8_t *inp,
                      size_t len) {
    uint64_t swapped[2];
    swapped[0] = CRYPTO_bswap8(Xi[1]);
    swapped[1] = CRYPTO_bswap8(Xi[0]);
  
    while (len >= 16) {
      uint64_t block[2];
      OPENSSL_memcpy(block, inp, 16);
      swapped[0] ^= CRYPTO_bswap8(block[1]);
      swapped[1] ^= CRYPTO_bswap8(block[0]);
      gcm_polyval_nohw(swapped, &Htable[0]);
      inp += 16;
      len -= 16;
    }
  
    Xi[0] = CRYPTO_bswap8(swapped[1]);
    Xi[1] = CRYPTO_bswap8(swapped[0]);
  }
  