// Copyright 2023 The BoringSSL Authors

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/base.h>

#include <assert.h>

#include <stdlib.h>

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

#include "./internal.h"

// keccak_f implements the Keccak-1600 permutation as described at

// https://keccak.team/keccak_specs_summary.html. Each lane is represented as a

// 64-bit value and the 5×5 lanes are stored as an array in row-major order.

static void keccak_f(uint64_t state[25]) {

  static const int kNumRounds = 24;

  for (int round = 0; round < kNumRounds; round++) {

    // θ step

    uint64_t c[5];

    for (int x = 0; x < 5; x++) {

      c[x] = state[x] ^ state[x + 5] ^ state[x + 10] ^ state[x + 15] ^

             state[x + 20];

    }

    for (int x = 0; x < 5; x++) {

      const uint64_t d = c[(x + 4) % 5] ^ CRYPTO_rotl_u64(c[(x + 1) % 5], 1);

      for (int y = 0; y < 5; y++) {

        state[y * 5 + x] ^= d;

      }

    }

    // ρ and π steps.

    //

    // These steps involve a mapping of the state matrix. Each input point,

    // (x,y), is rotated and written to the point (y, 2x + 3y). In the Keccak

    // pseudo-code a separate array is used because an in-place operation would

    // overwrite some values that are subsequently needed. However, the mapping

    // forms a trail through 24 of the 25 values so we can do it in place with

    // only a single temporary variable.

    //

    // Start with (1, 0). The value here will be mapped and end up at (0, 2).

    // That value will end up at (2, 1), then (1, 2), and so on. After 24

    // steps, 24 of the 25 values have been hit (as this mapping is injective)

    // and the sequence will repeat. All that remains is to handle the element

    // at (0, 0), but the rotation for that element is zero, and it goes to (0,

    // 0), so we can ignore it.

    uint64_t prev_value = state[1];

#define PI_RHO_STEP(index, rotation)                              \

  do {                                                            \

    const uint64_t value = CRYPTO_rotl_u64(prev_value, rotation); \

    prev_value = state[index];                                    \

    state[index] = value;                                         \

  } while (0)

    PI_RHO_STEP(10, 1);

    PI_RHO_STEP(7, 3);

    PI_RHO_STEP(11, 6);

    PI_RHO_STEP(17, 10);

    PI_RHO_STEP(18, 15);

    PI_RHO_STEP(3, 21);

    PI_RHO_STEP(5, 28);

    PI_RHO_STEP(16, 36);

    PI_RHO_STEP(8, 45);

    PI_RHO_STEP(21, 55);

    PI_RHO_STEP(24, 2);

    PI_RHO_STEP(4, 14);

    PI_RHO_STEP(15, 27);

    PI_RHO_STEP(23, 41);

    PI_RHO_STEP(19, 56);

    PI_RHO_STEP(13, 8);

    PI_RHO_STEP(12, 25);

    PI_RHO_STEP(2, 43);

    PI_RHO_STEP(20, 62);

    PI_RHO_STEP(14, 18);

    PI_RHO_STEP(22, 39);

    PI_RHO_STEP(9, 61);

    PI_RHO_STEP(6, 20);

    PI_RHO_STEP(1, 44);

#undef PI_RHO_STEP

    // χ step

    for (int y = 0; y < 5; y++) {

      const int row_index = 5 * y;

      const uint64_t orig_x0 = state[row_index];

      const uint64_t orig_x1 = state[row_index + 1];

      state[row_index] ^= ~orig_x1 & state[row_index + 2];

      state[row_index + 1] ^= ~state[row_index + 2] & state[row_index + 3];

      state[row_index + 2] ^= ~state[row_index + 3] & state[row_index + 4];

      state[row_index + 3] ^= ~state[row_index + 4] & orig_x0;

      state[row_index + 4] ^= ~orig_x0 & orig_x1;

    }

    // ι step

    //

    // From https://keccak.team/files/Keccak-reference-3.0.pdf, section

    // 1.2, the round constants are based on the output of a LFSR. Thus, as

    // suggested in the appendix of of

    // https://keccak.team/keccak_specs_summary.html, the values are

    // simply encoded here.

    static const uint64_t kRoundConstants[24] = {

        0x0000000000000001, 0x0000000000008082, 0x800000000000808a,

        0x8000000080008000, 0x000000000000808b, 0x0000000080000001,

        0x8000000080008081, 0x8000000000008009, 0x000000000000008a,

        0x0000000000000088, 0x0000000080008009, 0x000000008000000a,

        0x000000008000808b, 0x800000000000008b, 0x8000000000008089,

        0x8000000000008003, 0x8000000000008002, 0x8000000000000080,

        0x000000000000800a, 0x800000008000000a, 0x8000000080008081,

        0x8000000000008080, 0x0000000080000001, 0x8000000080008008,

    };

    state[0] ^= kRoundConstants[round];

  }

}

static void keccak_init(struct BORINGSSL_keccak_st *ctx,

                        enum boringssl_keccak_config_t config) {

  size_t required_out_len;

  size_t capacity_bytes;

  switch (config) {

    case boringssl_sha3_256:

      capacity_bytes = 512 / 8;

      required_out_len = 32;

      break;

    case boringssl_sha3_512:

      capacity_bytes = 1024 / 8;

      required_out_len = 64;

      break;

    case boringssl_shake128:

      capacity_bytes = 256 / 8;

      required_out_len = 0;

      break;

    case boringssl_shake256:

      capacity_bytes = 512 / 8;

      required_out_len = 0;

      break;

    default:

      abort();

  }

  OPENSSL_memset(ctx, 0, sizeof(*ctx));

  ctx->config = config;

  ctx->phase = boringssl_keccak_phase_absorb;

  ctx->required_out_len = required_out_len;

  ctx->rate_bytes = 200 - capacity_bytes;

  assert(ctx->rate_bytes % 8 == 0);

}

void BORINGSSL_keccak(uint8_t *out, size_t out_len, const uint8_t *in,

                      size_t in_len, enum boringssl_keccak_config_t config) {

  struct BORINGSSL_keccak_st ctx;

  keccak_init(&ctx, config);

  if (ctx.required_out_len != 0 && out_len != ctx.required_out_len) {

    abort();

  }

  BORINGSSL_keccak_absorb(&ctx, in, in_len);

  BORINGSSL_keccak_squeeze(&ctx, out, out_len);

}

void BORINGSSL_keccak_init(struct BORINGSSL_keccak_st *ctx,

                           enum boringssl_keccak_config_t config) {

  keccak_init(ctx, config);

}

void BORINGSSL_keccak_absorb(struct BORINGSSL_keccak_st *ctx, const uint8_t *in,

                             size_t in_len) {

  if (ctx->phase == boringssl_keccak_phase_squeeze) {

    // It's illegal to call absorb() again after calling squeeze().

    abort();

  }

  const size_t rate_words = ctx->rate_bytes / 8;

  // XOR the input. Accessing |ctx->state| as a |uint8_t*| is allowed by strict

  // aliasing because we require |uint8_t| to be a character type.

  uint8_t *state_bytes = (uint8_t *)ctx->state;

  // Absorb partial block.

  if (ctx->absorb_offset != 0) {

    assert(ctx->absorb_offset < ctx->rate_bytes);

    size_t first_block_len = ctx->rate_bytes - ctx->absorb_offset;

    for (size_t i = 0; i < first_block_len && i < in_len; i++) {

      state_bytes[ctx->absorb_offset + i] ^= in[i];

    }

    // This input didn't fill the block.

    if (first_block_len > in_len) {

      ctx->absorb_offset += in_len;

      return;

    }

    keccak_f(ctx->state);

    in += first_block_len;

    in_len -= first_block_len;

  }

  // Absorb full blocks.

  while (in_len >= ctx->rate_bytes) {

    for (size_t i = 0; i < rate_words; i++) {

      ctx->state[i] ^= CRYPTO_load_u64_le(in + 8 * i);

    }

    keccak_f(ctx->state);

    in += ctx->rate_bytes;

    in_len -= ctx->rate_bytes;

  }

  // Absorb partial block.

  assert(in_len < ctx->rate_bytes);

  for (size_t i = 0; i < in_len; i++) {

    state_bytes[i] ^= in[i];

  }

  ctx->absorb_offset = in_len;

}

static void keccak_finalize(struct BORINGSSL_keccak_st *ctx) {

  uint8_t terminator;

  switch (ctx->config) {

    case boringssl_sha3_256:

    case boringssl_sha3_512:

      terminator = 0x06;

      break;

    case boringssl_shake128:

    case boringssl_shake256:

      terminator = 0x1f;

      break;

    default:

      abort();

  }

  // XOR the terminator. Accessing |ctx->state| as a |uint8_t*| is allowed by

  // strict aliasing because we require |uint8_t| to be a character type.

  uint8_t *state_bytes = (uint8_t *)ctx->state;

  state_bytes[ctx->absorb_offset] ^= terminator;

  state_bytes[ctx->rate_bytes - 1] ^= 0x80;

  keccak_f(ctx->state);

}

void BORINGSSL_keccak_squeeze(struct BORINGSSL_keccak_st *ctx, uint8_t *out,

                              size_t out_len) {

  if (ctx->required_out_len != 0 &&

      (ctx->phase == boringssl_keccak_phase_squeeze ||

       out_len != ctx->required_out_len)) {

    // The SHA-3 variants must be squeezed in a single call, to confirm that the

    // output length is correct.

    abort();

  }

  if (ctx->phase == boringssl_keccak_phase_absorb) {

    keccak_finalize(ctx);

    ctx->phase = boringssl_keccak_phase_squeeze;

  }

  // Accessing |ctx->state| as a |uint8_t*| is allowed by strict aliasing

  // because we require |uint8_t| to be a character type.

  const uint8_t *state_bytes = (const uint8_t *)ctx->state;

  while (out_len) {

    if (ctx->squeeze_offset == ctx->rate_bytes) {

      keccak_f(ctx->state);

      ctx->squeeze_offset = 0;

    }

    size_t remaining = ctx->rate_bytes - ctx->squeeze_offset;

    size_t todo = out_len;

    if (todo > remaining) {

      todo = remaining;

    }

    OPENSSL_memcpy(out, &state_bytes[ctx->squeeze_offset], todo);

    out += todo;

    out_len -= todo;

    ctx->squeeze_offset += todo;

  }

}