/* vim:set ts=2 sw=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * "clean room" MD4 implementation (see RFC 1320)
 */

#include <string.h>
#include "md4.h"

/* the "conditional" function */
#define F(x, y, z) (((x) & (y)) | (~(x) & (z)))

/* the "majority" function */
#define G(x, y, z) (((x) & (y)) | ((x) & (z)) | ((y) & (z)))

/* the "parity" function */
#define H(x, y, z) ((x) ^ (y) ^ (z))

/* rotate n-bits to the left */
#define ROTL(x, n) (((x) << (n)) | ((x) >> (0x20 - n)))

/* round 1: [abcd k s]: a = (a + F(b,c,d) + X[k]) <<< s */
#define RD1(a, b, c, d, k, s) \
  a += F(b, c, d) + X[k];     \
  a = ROTL(a, s)

/* round 2: [abcd k s]: a = (a + G(b,c,d) + X[k] + MAGIC) <<< s */
#define RD2(a, b, c, d, k, s)          \
  a += G(b, c, d) + X[k] + 0x5A827999; \
  a = ROTL(a, s)

/* round 3: [abcd k s]: a = (a + H(b,c,d) + X[k] + MAGIC) <<< s */
#define RD3(a, b, c, d, k, s)          \
  a += H(b, c, d) + X[k] + 0x6ED9EBA1; \
  a = ROTL(a, s)

/* converts from word array to byte array, len is number of bytes */
static void w2b(uint8_t* out, const uint32_t* in, uint32_t len) {
  uint8_t* bp;
  const uint32_t *wp, *wpend;

  bp = out;
  wp = in;
  wpend = wp + (len >> 2);

  for (; wp != wpend; ++wp, bp += 4) {
    bp[0] = (uint8_t)((*wp) & 0xFF);
    bp[1] = (uint8_t)((*wp >> 8) & 0xFF);
    bp[2] = (uint8_t)((*wp >> 16) & 0xFF);
    bp[3] = (uint8_t)((*wp >> 24) & 0xFF);
  }
}

/* converts from byte array to word array, len is number of bytes */
static void b2w(uint32_t* out, const uint8_t* in, uint32_t len) {
  uint32_t* wp;
  const uint8_t *bp, *bpend;

  wp = out;
  bp = in;
  bpend = in + len;

  for (; bp != bpend; bp += 4, ++wp) {
    *wp = (uint32_t)bp[0] | ((uint32_t)bp[1] << 8) | ((uint32_t)bp[2] << 16) |
          ((uint32_t)bp[3] << 24);
  }
}

/* update state: data is 64 bytes in length */
static void md4step(uint32_t state[4], const uint8_t* data) {
  uint32_t A, B, C, D, X[16];

  b2w(X, data, 64);

  A = state[0];
  B = state[1];
  C = state[2];
  D = state[3];

  RD1(A, B, C, D, 0, 3);
  RD1(D, A, B, C, 1, 7);
  RD1(C, D, A, B, 2, 11);
  RD1(B, C, D, A, 3, 19);
  RD1(A, B, C, D, 4, 3);
  RD1(D, A, B, C, 5, 7);
  RD1(C, D, A, B, 6, 11);
  RD1(B, C, D, A, 7, 19);
  RD1(A, B, C, D, 8, 3);
  RD1(D, A, B, C, 9, 7);
  RD1(C, D, A, B, 10, 11);
  RD1(B, C, D, A, 11, 19);
  RD1(A, B, C, D, 12, 3);
  RD1(D, A, B, C, 13, 7);
  RD1(C, D, A, B, 14, 11);
  RD1(B, C, D, A, 15, 19);

  RD2(A, B, C, D, 0, 3);
  RD2(D, A, B, C, 4, 5);
  RD2(C, D, A, B, 8, 9);
  RD2(B, C, D, A, 12, 13);
  RD2(A, B, C, D, 1, 3);
  RD2(D, A, B, C, 5, 5);
  RD2(C, D, A, B, 9, 9);
  RD2(B, C, D, A, 13, 13);
  RD2(A, B, C, D, 2, 3);
  RD2(D, A, B, C, 6, 5);
  RD2(C, D, A, B, 10, 9);
  RD2(B, C, D, A, 14, 13);
  RD2(A, B, C, D, 3, 3);
  RD2(D, A, B, C, 7, 5);
  RD2(C, D, A, B, 11, 9);
  RD2(B, C, D, A, 15, 13);

  RD3(A, B, C, D, 0, 3);
  RD3(D, A, B, C, 8, 9);
  RD3(C, D, A, B, 4, 11);
  RD3(B, C, D, A, 12, 15);
  RD3(A, B, C, D, 2, 3);
  RD3(D, A, B, C, 10, 9);
  RD3(C, D, A, B, 6, 11);
  RD3(B, C, D, A, 14, 15);
  RD3(A, B, C, D, 1, 3);
  RD3(D, A, B, C, 9, 9);
  RD3(C, D, A, B, 5, 11);
  RD3(B, C, D, A, 13, 15);
  RD3(A, B, C, D, 3, 3);
  RD3(D, A, B, C, 11, 9);
  RD3(C, D, A, B, 7, 11);
  RD3(B, C, D, A, 15, 15);

  state[0] += A;
  state[1] += B;
  state[2] += C;
  state[3] += D;
}

void md4sum(const uint8_t* input, uint32_t inputLen, uint8_t* result) {
  uint8_t final[128];
  uint32_t i, n, m, state[4];
  uint64_t inputLenBits;
  uint32_t inputLenBitsLow;
  uint32_t inputLenBitsHigh;

  /* magic initial states */
  state[0] = 0x67452301;
  state[1] = 0xEFCDAB89;
  state[2] = 0x98BADCFE;
  state[3] = 0x10325476;

  /* compute number of complete 64-byte segments contained in input */
  m = inputLen >> 6;

  /* digest first m segments */
  for (i = 0; i < m; ++i) md4step(state, (input + (i << 6)));

  /* build final buffer */
  n = inputLen % 64;
  memcpy(final, input + (m << 6), n);
  final[n] = 0x80;
  memset(final + n + 1, 0, 120 - (n + 1));

  /* Append the original input length in bits as a 64-bit number. This is done
   * in two 32-bit chunks, with the least-significant 32 bits first.
   * w2b will handle endianness. */
  inputLenBits = inputLen << 3;
  inputLenBitsLow = (uint32_t)(inputLenBits & 0xFFFFFFFF);
  w2b(final + (n >= 56 ? 120 : 56), &inputLenBitsLow, 4);
  inputLenBitsHigh = (uint32_t)((inputLenBits >> 32) & 0xFFFFFFFF);
  w2b(final + (n >= 56 ? 124 : 60), &inputLenBitsHigh, 4);

  md4step(state, final);
  if (n >= 56) md4step(state, final + 64);

  /* copy state to result */
  w2b(result, state, 16);
}