src/base/unverified_aes256.cc

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#include "base/unverified_aes256.h"

#include <algorithm>
#include <cstring>

#include "base/logging.h"

namespace mozc {
namespace internal {
namespace {

const uint8_t kSBox[256] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
    0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
    0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
    0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
    0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
    0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
    0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
    0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
    0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
    0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
    0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
    0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

const uint8_t kInvSBox[256] = {
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
    0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
    0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
    0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
    0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
    0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
    0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
    0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
    0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
    0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
    0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
    0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
    0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
    0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
    0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
    0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
};

const size_t kNr = 14;

void AddRoundKey(uint8_t block[UnverifiedAES256::kBlockBytes],
                 const uint8 round_key[UnverifiedAES256::kBlockBytes]) {
  for (size_t i = 0; i < UnverifiedAES256::kBlockBytes; ++i) {
    block[i] ^= round_key[i];
  }
}

uint8 GF_p8_mul3(uint8 val) {
  const uint8 x = val * 2;
  return (val >= 0x80) ? (x ^ 0x1b) : x;
}

void MixColumnsImpl(uint8 column[4]) {
  uint8 a1[4];
  uint8 a2[4];
  uint8 a3[4];
  for (size_t i = 0; i < 4; ++i) {
    a1[i] = column[i];
    a2[i] = GF_p8_mul3(a1[i]);
    a3[i] = a2[i] ^ a1[i];
  }
  column[0] = a2[0] ^ a3[1] ^ a1[2] ^ a1[3];
  column[1] = a1[0] ^ a2[1] ^ a3[2] ^ a1[3];
  column[2] = a1[0] ^ a1[1] ^ a2[2] ^ a3[3];
  column[3] = a3[0] ^ a1[1] ^ a1[2] ^ a2[3];
}

void InvMixColumnsImpl(uint8 column[4]) {
  uint8 a9[4];
  uint8 a11[4];
  uint8 a13[4];
  uint8 a14[4];
  for (size_t i = 0; i < 4; ++i) {
    const uint8 a1 = column[i];
    const uint8 a2 = GF_p8_mul3(a1);
    const uint8 a2_2 = GF_p8_mul3(a2);
    a9[i] = GF_p8_mul3(a2_2) ^ a1;
    a11[i] = GF_p8_mul3(a2_2 ^ a1) ^ a1;
    const uint8 a2a1_2 = GF_p8_mul3(a2 ^ a1);
    a13[i] = GF_p8_mul3(a2a1_2) ^ a1;
    a14[i] = GF_p8_mul3(a2a1_2 ^ a1);
  }
  column[0] = a14[0] ^ a11[1] ^ a13[2] ^  a9[3];
  column[1] =  a9[0] ^ a14[1] ^ a11[2] ^ a13[3];
  column[2] = a13[0] ^  a9[1] ^ a14[2] ^ a11[3];
  column[3] = a11[0] ^ a13[1] ^  a9[2] ^ a14[3];
}

}  // namespace

void UnverifiedAES256::TransformCBC(const uint8 (&key)[kKeyBytes],
                                    const uint8 (&iv)[kBlockBytes],
                                    uint8 *block,
                                    size_t block_count) {
  uint8 w[kKeyScheduleBytes];
  MakeKeySchedule(key, w);

  uint8 vec[kBlockBytes];
  memcpy(vec, iv, kBlockBytes);
  for (size_t i = 0; i < block_count; ++i) {
    uint8_t *src = block + (i * kBlockBytes);
    for (size_t j = 0; j < kBlockBytes; ++j) {
      src[j] ^= vec[j];
    }
    TransformECB(w, src);
    memcpy(vec, src, kBlockBytes);
  }
}

void UnverifiedAES256::InverseTransformCBC(const uint8 (&key)[kKeyBytes],
                                           const uint8 (&iv)[kBlockBytes],
                                           uint8 *block,
                                           size_t block_count) {
  uint8 w[kKeyScheduleBytes];
  MakeKeySchedule(key, w);

  uint8 prev_block[kBlockBytes];
  memcpy(prev_block, iv, kBlockBytes);
  for (size_t i = 0; i < block_count; ++i) {
    uint8 original_current_block[kBlockBytes];
    uint8_t *currnt_block = block + (i * kBlockBytes);
    memcpy(original_current_block, currnt_block, kBlockBytes);
    InverseTransformECB(w, currnt_block);
    for (size_t j = 0; j < kBlockBytes; ++j) {
      currnt_block[j] ^= prev_block[j];
    }
    memcpy(prev_block, original_current_block, kBlockBytes);
  }
}

void UnverifiedAES256::MakeKeySchedule(const uint8 (&key)[kKeyBytes],
                                       uint8 w[kKeyScheduleBytes]) {
  memcpy(w, key, kKeyBytes);
  for (size_t base = 1; ; ++base) {
    uint8 *k = &w[base * kKeyBytes];
    uint8 *prev = k - kKeyBytes;
    // Note: Although the following equation is not always satisfied,
    // it is valid at least when 1 <= |base| <= 7.
    DCHECK_LE(1, base);
    DCHECK_GE(7, base);
    const uint8 rcon = 1 << (base - 1);
    k[0] = prev[0] ^ kSBox[prev[29]] ^ rcon;
    k[1] = prev[1] ^ kSBox[prev[30]];
    k[2] = prev[2] ^ kSBox[prev[31]];
    k[3] = prev[3] ^ kSBox[prev[28]];
    for (size_t i = 4; i < 16; ++i) {
      k[i] = prev[i] ^ k[i-4];
    }
    if (base == 7) {
      break;
    }
    for (size_t i = 16; i < 20; ++i) {
      k[i] = prev[i] ^ kSBox[k[i-4]];
    }
    for (size_t i = 20; i < 32; ++i) {
      k[i] = prev[i] ^ k[i-4];
    }
  }
}

void UnverifiedAES256::SubBytes(uint8 block[kBlockBytes]) {
  for (size_t i = 0; i < kBlockBytes; ++i) {
    block[i] = kSBox[block[i]];
  }
}

void UnverifiedAES256::InvSubBytes(uint8 block[kBlockBytes]) {
  for (size_t i = 0; i < kBlockBytes; ++i) {
    block[i] = kInvSBox[block[i]];
  }
}

void UnverifiedAES256::MixColumns(uint8 block[kBlockBytes]) {
  for (size_t i = 0; i < kBlockBytes; i+=4) {
    MixColumnsImpl(block + i);
  }
}

void UnverifiedAES256::InvMixColumns(uint8 block[kBlockBytes]) {
  for (size_t i = 0; i < kBlockBytes; i+=4) {
    InvMixColumnsImpl(block + i);
  }
}

void UnverifiedAES256::ShiftRows(uint8 block[kBlockBytes]) {
  // Row 0 does not change.

  // Row 1
  {
    const uint8 x = block[1];
    block[1] = block[5];
    block[5] = block[9];
    block[9] = block[13];
    block[13] = x;
  }

  // Row 2
  {
    std::swap(block[2], block[10]);
    std::swap(block[6], block[14]);
  }

  // Row 3
  {
    const uint8 x = block[3];
    block[3] = block[15];
    block[15] = block[11];
    block[11] = block[7];
    block[7] = x;
  }
}

void UnverifiedAES256::InvShiftRows(uint8 block[kBlockBytes]) {
  // Row 0 does not change.

  // Row 1
  {
    const uint8 x = block[1];
    block[1] = block[13];
    block[13] = block[9];
    block[9] = block[5];
    block[5] = x;
  }

  // Row 2
  {
    std::swap(block[2], block[10]);
    std::swap(block[6], block[14]);
  }

  // Row 3
  {
    const uint8 x = block[3];
    block[3] = block[7];
    block[7] = block[11];
    block[11] = block[15];
    block[15] = x;
  }
}

void UnverifiedAES256::TransformECB(const uint8 (&w)[kKeyScheduleBytes],
                                    uint8 block[kBlockBytes]) {
  AddRoundKey(block, &w[0]);
  for (size_t round = 1; round < kNr; ++round) {
    SubBytes(block);
    ShiftRows(block);
    MixColumns(block);
    AddRoundKey(block, &w[kBlockBytes * round]);
  }
  SubBytes(block);
  ShiftRows(block);
  AddRoundKey(block, &w[kBlockBytes * kNr]);
}

void UnverifiedAES256::InverseTransformECB(const uint8 (&w)[kKeyScheduleBytes],
                                           uint8 block[kBlockBytes]) {
  AddRoundKey(block, &w[kBlockBytes * kNr]);
  InvShiftRows(block);
  InvSubBytes(block);
  for (size_t round = (kNr - 1); round > 0; --round) {
    AddRoundKey(block, &w[kBlockBytes * round]);
    InvMixColumns(block);
    InvShiftRows(block);
    InvSubBytes(block);
  }
  AddRoundKey(block, &w[0]);
}

}  // namespace internal
}  // namespace mozc