/// @file sha256.c
///
/// FIPS-180-2 compliant SHA-256 implementation
/// GPL by Christophe Devine, applies to older version.
/// Modified for md5deep, in public domain.
/// Modified For Vim, Mohsin Ahmed, http://www.cs.albany.edu/~mosh
/// Mohsin Ahmed states this work is distributed under the VIM License or GPL,
/// at your choice.
///
/// Vim specific notes:
/// sha256_self_test() is implicitly called once.

#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

#include "nvim/ascii_defs.h"
#include "nvim/memory.h"
#include "nvim/sha256.h"

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "sha256.c.generated.h"
#endif
#define GET_UINT32(n, b, i) { \
  (n) = ((uint32_t)(b)[(i)] << 24) \
        | ((uint32_t)(b)[(i) + 1] << 16) \
        | ((uint32_t)(b)[(i) + 2] <<  8) \
        | ((uint32_t)(b)[(i) + 3]); \
}

#define PUT_UINT32(n, b, i) { \
  (b)[(i)] = (uint8_t)((n) >> 24); \
  (b)[(i) + 1] = (uint8_t)((n) >> 16); \
  (b)[(i) + 2] = (uint8_t)((n) >>  8); \
  (b)[(i) + 3] = (uint8_t)((n)); \
}

void sha256_start(context_sha256_T *ctx)
{
  ctx->total[0] = 0;
  ctx->total[1] = 0;

  ctx->state[0] = 0x6A09E667;
  ctx->state[1] = 0xBB67AE85;
  ctx->state[2] = 0x3C6EF372;
  ctx->state[3] = 0xA54FF53A;
  ctx->state[4] = 0x510E527F;
  ctx->state[5] = 0x9B05688C;
  ctx->state[6] = 0x1F83D9AB;
  ctx->state[7] = 0x5BE0CD19;
}

static void sha256_process(context_sha256_T *ctx, const uint8_t data[SHA256_BUFFER_SIZE])
{
  uint32_t temp1, temp2, W[SHA256_BUFFER_SIZE];
  uint32_t A, B, C, D, E, F, G, H;

  GET_UINT32(W[0],  data,  0);
  GET_UINT32(W[1],  data,  4);
  GET_UINT32(W[2],  data,  8);
  GET_UINT32(W[3],  data, 12);
  GET_UINT32(W[4],  data, 16);
  GET_UINT32(W[5],  data, 20);
  GET_UINT32(W[6],  data, 24);
  GET_UINT32(W[7],  data, 28);
  GET_UINT32(W[8],  data, 32);
  GET_UINT32(W[9],  data, 36);
  GET_UINT32(W[10], data, 40);
  GET_UINT32(W[11], data, 44);
  GET_UINT32(W[12], data, 48);
  GET_UINT32(W[13], data, 52);
  GET_UINT32(W[14], data, 56);
  GET_UINT32(W[15], data, 60);

#define  SHR(x, n) (((x) & 0xFFFFFFFF) >> (n))
#define ROTR(x, n) (SHR(x, n) | ((x) << (32 - (n))))

#define S0(x) (ROTR(x, 7) ^ ROTR(x, 18) ^  SHR(x, 3))
#define S1(x) (ROTR(x, 17) ^ ROTR(x, 19) ^  SHR(x, 10))

#define S2(x) (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
#define S3(x) (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))

#define F0(x, y, z) (((x) & (y)) | ((z) & ((x) | (y))))
#define F1(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))

#define R(t) \
  (W[t] = S1(W[(t) - 2]) + W[(t) - 7] + S0(W[(t) - 15]) + W[(t) - 16])

#define P(a, b, c, d, e, f, g, h, x, K) { \
  temp1 = (h) + S3(e) + F1(e, f, g) + (K) + (x); \
  temp2 = S2(a) + F0(a, b, c); \
  (d) += temp1; (h) = temp1 + temp2; \
}

  A = ctx->state[0];
  B = ctx->state[1];
  C = ctx->state[2];
  D = ctx->state[3];
  E = ctx->state[4];
  F = ctx->state[5];
  G = ctx->state[6];
  H = ctx->state[7];

  P(A, B, C, D, E, F, G, H, W[0],  0x428A2F98);
  P(H, A, B, C, D, E, F, G, W[1],  0x71374491);
  P(G, H, A, B, C, D, E, F, W[2],  0xB5C0FBCF);
  P(F, G, H, A, B, C, D, E, W[3],  0xE9B5DBA5);
  P(E, F, G, H, A, B, C, D, W[4],  0x3956C25B);
  P(D, E, F, G, H, A, B, C, W[5],  0x59F111F1);
  P(C, D, E, F, G, H, A, B, W[6],  0x923F82A4);
  P(B, C, D, E, F, G, H, A, W[7],  0xAB1C5ED5);
  P(A, B, C, D, E, F, G, H, W[8],  0xD807AA98);
  P(H, A, B, C, D, E, F, G, W[9],  0x12835B01);
  P(G, H, A, B, C, D, E, F, W[10], 0x243185BE);
  P(F, G, H, A, B, C, D, E, W[11], 0x550C7DC3);
  P(E, F, G, H, A, B, C, D, W[12], 0x72BE5D74);
  P(D, E, F, G, H, A, B, C, W[13], 0x80DEB1FE);
  P(C, D, E, F, G, H, A, B, W[14], 0x9BDC06A7);
  P(B, C, D, E, F, G, H, A, W[15], 0xC19BF174);
  P(A, B, C, D, E, F, G, H, R(16), 0xE49B69C1);
  P(H, A, B, C, D, E, F, G, R(17), 0xEFBE4786);
  P(G, H, A, B, C, D, E, F, R(18), 0x0FC19DC6);
  P(F, G, H, A, B, C, D, E, R(19), 0x240CA1CC);
  P(E, F, G, H, A, B, C, D, R(20), 0x2DE92C6F);
  P(D, E, F, G, H, A, B, C, R(21), 0x4A7484AA);
  P(C, D, E, F, G, H, A, B, R(22), 0x5CB0A9DC);
  P(B, C, D, E, F, G, H, A, R(23), 0x76F988DA);
  P(A, B, C, D, E, F, G, H, R(24), 0x983E5152);
  P(H, A, B, C, D, E, F, G, R(25), 0xA831C66D);
  P(G, H, A, B, C, D, E, F, R(26), 0xB00327C8);
  P(F, G, H, A, B, C, D, E, R(27), 0xBF597FC7);
  P(E, F, G, H, A, B, C, D, R(28), 0xC6E00BF3);
  P(D, E, F, G, H, A, B, C, R(29), 0xD5A79147);
  P(C, D, E, F, G, H, A, B, R(30), 0x06CA6351);
  P(B, C, D, E, F, G, H, A, R(31), 0x14292967);
  P(A, B, C, D, E, F, G, H, R(32), 0x27B70A85);
  P(H, A, B, C, D, E, F, G, R(33), 0x2E1B2138);
  P(G, H, A, B, C, D, E, F, R(34), 0x4D2C6DFC);
  P(F, G, H, A, B, C, D, E, R(35), 0x53380D13);
  P(E, F, G, H, A, B, C, D, R(36), 0x650A7354);
  P(D, E, F, G, H, A, B, C, R(37), 0x766A0ABB);
  P(C, D, E, F, G, H, A, B, R(38), 0x81C2C92E);
  P(B, C, D, E, F, G, H, A, R(39), 0x92722C85);
  P(A, B, C, D, E, F, G, H, R(40), 0xA2BFE8A1);
  P(H, A, B, C, D, E, F, G, R(41), 0xA81A664B);
  P(G, H, A, B, C, D, E, F, R(42), 0xC24B8B70);
  P(F, G, H, A, B, C, D, E, R(43), 0xC76C51A3);
  P(E, F, G, H, A, B, C, D, R(44), 0xD192E819);
  P(D, E, F, G, H, A, B, C, R(45), 0xD6990624);
  P(C, D, E, F, G, H, A, B, R(46), 0xF40E3585);
  P(B, C, D, E, F, G, H, A, R(47), 0x106AA070);
  P(A, B, C, D, E, F, G, H, R(48), 0x19A4C116);
  P(H, A, B, C, D, E, F, G, R(49), 0x1E376C08);
  P(G, H, A, B, C, D, E, F, R(50), 0x2748774C);
  P(F, G, H, A, B, C, D, E, R(51), 0x34B0BCB5);
  P(E, F, G, H, A, B, C, D, R(52), 0x391C0CB3);
  P(D, E, F, G, H, A, B, C, R(53), 0x4ED8AA4A);
  P(C, D, E, F, G, H, A, B, R(54), 0x5B9CCA4F);
  P(B, C, D, E, F, G, H, A, R(55), 0x682E6FF3);
  P(A, B, C, D, E, F, G, H, R(56), 0x748F82EE);
  P(H, A, B, C, D, E, F, G, R(57), 0x78A5636F);
  P(G, H, A, B, C, D, E, F, R(58), 0x84C87814);
  P(F, G, H, A, B, C, D, E, R(59), 0x8CC70208);
  P(E, F, G, H, A, B, C, D, R(60), 0x90BEFFFA);
  P(D, E, F, G, H, A, B, C, R(61), 0xA4506CEB);
  P(C, D, E, F, G, H, A, B, R(62), 0xBEF9A3F7);
  P(B, C, D, E, F, G, H, A, R(63), 0xC67178F2);

  ctx->state[0] += A;
  ctx->state[1] += B;
  ctx->state[2] += C;
  ctx->state[3] += D;
  ctx->state[4] += E;
  ctx->state[5] += F;
  ctx->state[6] += G;
  ctx->state[7] += H;
}

void sha256_update(context_sha256_T *ctx, const uint8_t *input, size_t length)
{
  if (length == 0) {
    return;
  }

  uint32_t left = ctx->total[0] & (SHA256_BUFFER_SIZE - 1);  // left < buf size

  ctx->total[0] += (uint32_t)length;
  ctx->total[0] &= 0xFFFFFFFF;

  if (ctx->total[0] < length) {
    ctx->total[1]++;
  }

  size_t fill = SHA256_BUFFER_SIZE - left;

  if (left && (length >= fill)) {
    memcpy(ctx->buffer + left, input, fill);
    sha256_process(ctx, ctx->buffer);
    length -= fill;
    input += fill;
    left = 0;
  }

  while (length >= SHA256_BUFFER_SIZE) {
    sha256_process(ctx, input);
    length -= SHA256_BUFFER_SIZE;
    input += SHA256_BUFFER_SIZE;
  }

  if (length) {
    memcpy(ctx->buffer + left, input, length);
  }
}

static uint8_t sha256_padding[SHA256_BUFFER_SIZE] = {
  0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

void sha256_finish(context_sha256_T *ctx, uint8_t digest[SHA256_SUM_SIZE])
{
  uint32_t high = (ctx->total[0] >> 29) | (ctx->total[1] <<  3);
  uint32_t low = (ctx->total[0] <<  3);

  uint8_t msglen[8];
  PUT_UINT32(high, msglen, 0);
  PUT_UINT32(low,  msglen, 4);

  uint32_t last = ctx->total[0] & 0x3F;
  uint32_t padn = (last < 56) ? (56 - last) : (120 - last);

  sha256_update(ctx, sha256_padding, padn);
  sha256_update(ctx, msglen,            8);

  PUT_UINT32(ctx->state[0], digest,  0);
  PUT_UINT32(ctx->state[1], digest,  4);
  PUT_UINT32(ctx->state[2], digest,  8);
  PUT_UINT32(ctx->state[3], digest, 12);
  PUT_UINT32(ctx->state[4], digest, 16);
  PUT_UINT32(ctx->state[5], digest, 20);
  PUT_UINT32(ctx->state[6], digest, 24);
  PUT_UINT32(ctx->state[7], digest, 28);
}

#define SHA_STEP 2

/// Gets the hex digest of the buffer.
///
/// @param buf
/// @param buf_len
/// @param salt
/// @param salt_len
///
/// @returns hex digest of "buf[buf_len]" in a static array.
///          if "salt" is not NULL also do "salt[salt_len]".
const char *sha256_bytes(const uint8_t *restrict buf,  size_t buf_len, const uint8_t *restrict salt,
                         size_t salt_len)
{
  static char hexit[SHA256_BUFFER_SIZE + 1];  // buf size + NULL

  sha256_self_test();

  context_sha256_T ctx;
  sha256_start(&ctx);
  sha256_update(&ctx, buf, buf_len);

  if (salt != NULL) {
    sha256_update(&ctx, salt, salt_len);
  }
  uint8_t sha256sum[SHA256_SUM_SIZE];
  sha256_finish(&ctx, sha256sum);

  for (size_t j = 0; j < SHA256_SUM_SIZE; j++) {
    snprintf(hexit + j * SHA_STEP, SHA_STEP + 1, "%02x", sha256sum[j]);
  }
  hexit[sizeof(hexit) - 1] = NUL;
  return hexit;
}

// These are the standard FIPS-180-2 test vectors
static char *sha_self_test_msg[] = {
  "abc",
  "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
  NULL
};

static char *sha_self_test_vector[] = {
  "ba7816bf8f01cfea414140de5dae2223" \
  "b00361a396177a9cb410ff61f20015ad",
  "248d6a61d20638b8e5c026930c3e6039" \
  "a33ce45964ff2167f6ecedd419db06c1",
  "cdc76e5c9914fb9281a1c7e284d73e67" \
  "f1809a48a497200e046d39ccc7112cd0"
};

/// Perform a test on the SHA256 algorithm.
///
/// @returns true if not failures generated.
bool sha256_self_test(void)
{
  char output[SHA256_BUFFER_SIZE + 1];  // buf size + NULL
  context_sha256_T ctx;
  uint8_t buf[1000];
  uint8_t sha256sum[SHA256_SUM_SIZE];
  const char *hexit;

  static bool sha256_self_tested = false;
  static bool failures = false;

  if (sha256_self_tested) {
    return failures == false;
  }
  sha256_self_tested = true;

  for (size_t i = 0; i < 3; i++) {
    if (i < 2) {
      hexit = sha256_bytes((uint8_t *)sha_self_test_msg[i],
                           strlen(sha_self_test_msg[i]),
                           NULL, 0);
      STRCPY(output, hexit);
    } else {
      sha256_start(&ctx);
      memset(buf, 'a', 1000);

      for (size_t j = 0; j < 1000; j++) {
        sha256_update(&ctx, buf, 1000);
      }
      sha256_finish(&ctx, sha256sum);

      for (size_t j = 0; j < SHA256_SUM_SIZE; j++) {
        snprintf(output + j * SHA_STEP, SHA_STEP + 1, "%02x", sha256sum[j]);
      }
    }

    if (memcmp(output, sha_self_test_vector[i], SHA256_BUFFER_SIZE) != 0) {
      failures = true;
      output[sizeof(output) - 1] = NUL;

      // printf("sha256_self_test %d failed %s\n", i, output);
    }
  }
  return failures == false;
}
