/* Functions to compute MD4 message digest of files or memory blocks.
   according to the definition of MD4 in RFC 1320 from April 1992.
   Copyright (C) 1995-1997, 1999-2003, 2005-2006, 2008-2023 Free Software
   Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Adapted by Simon Josefsson from gnulib md5.? and Libgcrypt
   cipher/md4.c . */

#include <config.h>

/* Specification.  */
#include "md4.h"

#include <stdint.h>
#include <string.h>
#include <sys/types.h>

#include <byteswap.h>
#ifdef WORDS_BIGENDIAN
# define SWAP(n) bswap_32 (n)
#else
# define SWAP(n) (n)
#endif

/* This array contains the bytes used to pad the buffer to the next
   64-byte boundary.  (RFC 1320, 3.1: Step 1)  */
static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */  };


/* Initialize structure containing state of computation.
   (RFC 1320, 3.3: Step 3)  */
void
md4_init_ctx (struct md4_ctx *ctx)
{
  ctx->A = 0x67452301;
  ctx->B = 0xefcdab89;
  ctx->C = 0x98badcfe;
  ctx->D = 0x10325476;

  ctx->total[0] = ctx->total[1] = 0;
  ctx->buflen = 0;
}

/* Copy the 4 byte value from v into the memory location pointed to by *cp,
   If your architecture allows unaligned access this is equivalent to
   * (uint32_t *) cp = v  */
static void
set_uint32 (char *cp, uint32_t v)
{
  memcpy (cp, &v, sizeof v);
}

/* Put result from CTX in first 16 bytes following RESBUF.  The result
   must be in little endian byte order.  */
void *
md4_read_ctx (const struct md4_ctx *ctx, void *resbuf)
{
  char *r = resbuf;
  set_uint32 (r + 0 * sizeof ctx->A, SWAP (ctx->A));
  set_uint32 (r + 1 * sizeof ctx->B, SWAP (ctx->B));
  set_uint32 (r + 2 * sizeof ctx->C, SWAP (ctx->C));
  set_uint32 (r + 3 * sizeof ctx->D, SWAP (ctx->D));

  return resbuf;
}

/* Process the remaining bytes in the internal buffer and the usual
   prolog according to the standard and write the result to RESBUF.  */
void *
md4_finish_ctx (struct md4_ctx *ctx, void *resbuf)
{
  /* Take yet unprocessed bytes into account.  */
  uint32_t bytes = ctx->buflen;
  size_t pad;

  /* Now count remaining bytes.  */
  ctx->total[0] += bytes;
  if (ctx->total[0] < bytes)
    ++ctx->total[1];

  pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
  memcpy (&((char*)ctx->buffer)[bytes], fillbuf, pad);

  /* Put the 64-bit file length in *bits* at the end of the buffer.  */
  ctx->buffer[(bytes + pad) / 4] = SWAP (ctx->total[0] << 3);
  ctx->buffer[(bytes + pad) / 4 + 1] = SWAP ((ctx->total[1] << 3) |
                                             (ctx->total[0] >> 29));

  /* Process last bytes.  */
  md4_process_block (ctx->buffer, bytes + pad + 8, ctx);

  return md4_read_ctx (ctx, resbuf);
}

/* Compute MD4 message digest for LEN bytes beginning at BUFFER.  The
   result is always in little endian byte order, so that a byte-wise
   output yields to the wanted ASCII representation of the message
   digest.  */
void *
md4_buffer (const char *buffer, size_t len, void *resblock)
{
  struct md4_ctx ctx;

  /* Initialize the computation context.  */
  md4_init_ctx (&ctx);

  /* Process whole buffer but last len % 64 bytes.  */
  md4_process_bytes (buffer, len, &ctx);

  /* Put result in desired memory area.  */
  return md4_finish_ctx (&ctx, resblock);
}

void
md4_process_bytes (const void *buffer, size_t len, struct md4_ctx *ctx)
{
  /* When we already have some bits in our internal buffer concatenate
     both inputs first.  */
  if (ctx->buflen != 0)
    {
      size_t left_over = ctx->buflen;
      size_t add = 128 - left_over > len ? len : 128 - left_over;

      memcpy (&((char*)ctx->buffer)[left_over], buffer, add);
      ctx->buflen += add;

      if (ctx->buflen > 64)
        {
          md4_process_block (ctx->buffer, ctx->buflen & ~63, ctx);

          ctx->buflen &= 63;
          /* The regions in the following copy operation cannot overlap.  */
          memcpy (ctx->buffer, &((char*)ctx->buffer)[(left_over + add) & ~63],
                  ctx->buflen);
        }

      buffer = (const char *) buffer + add;
      len -= add;
    }

  /* Process available complete blocks.  */
  if (len >= 64)
    {
#if !(_STRING_ARCH_unaligned || _STRING_INLINE_unaligned)
# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (uint32_t) != 0)
      if (UNALIGNED_P (buffer))
        while (len > 64)
          {
            md4_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
            buffer = (const char *) buffer + 64;
            len -= 64;
          }
      else
#endif
        {
          md4_process_block (buffer, len & ~63, ctx);
          buffer = (const char *) buffer + (len & ~63);
          len &= 63;
        }
    }

  /* Move remaining bytes in internal buffer.  */
  if (len > 0)
    {
      size_t left_over = ctx->buflen;

      memcpy (&((char*)ctx->buffer)[left_over], buffer, len);
      left_over += len;
      if (left_over >= 64)
        {
          md4_process_block (ctx->buffer, 64, ctx);
          left_over -= 64;
          memcpy (ctx->buffer, &ctx->buffer[16], left_over);
        }
      ctx->buflen = left_over;
    }
}

/* --- Code below is the primary difference between md5.c and md4.c --- */

/* MD4 round constants */
#define K1 0x5a827999
#define K2 0x6ed9eba1

/* Round functions.  */
#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z) (((x) & (y)) | ((x) & (z)) | ((y) & (z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define rol(x, n) (((x) << (n)) | ((uint32_t) (x) >> (32 - (n))))
#define R1(a,b,c,d,k,s) a=rol(a+F(b,c,d)+x[k],s);
#define R2(a,b,c,d,k,s) a=rol(a+G(b,c,d)+x[k]+K1,s);
#define R3(a,b,c,d,k,s) a=rol(a+H(b,c,d)+x[k]+K2,s);

/* Process LEN bytes of BUFFER, accumulating context into CTX.
   It is assumed that LEN % 64 == 0.  */

void
md4_process_block (const void *buffer, size_t len, struct md4_ctx *ctx)
{
  const uint32_t *words = buffer;
  size_t nwords = len / sizeof (uint32_t);
  const uint32_t *endp = words + nwords;
  uint32_t x[16];
  uint32_t A = ctx->A;
  uint32_t B = ctx->B;
  uint32_t C = ctx->C;
  uint32_t D = ctx->D;
  uint32_t lolen = len;

  /* First increment the byte count.  RFC 1320 specifies the possible
     length of the file up to 2^64 bits.  Here we only compute the
     number of bytes.  Do a double word increment.  */
  ctx->total[0] += lolen;
  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);

  /* Process all bytes in the buffer with 64 bytes in each round of
     the loop.  */
  while (words < endp)
    {
      int t;
      for (t = 0; t < 16; t++)
        {
          x[t] = SWAP (*words);
          words++;
        }

      /* Round 1.  */
      R1 (A, B, C, D, 0, 3);
      R1 (D, A, B, C, 1, 7);
      R1 (C, D, A, B, 2, 11);
      R1 (B, C, D, A, 3, 19);
      R1 (A, B, C, D, 4, 3);
      R1 (D, A, B, C, 5, 7);
      R1 (C, D, A, B, 6, 11);
      R1 (B, C, D, A, 7, 19);
      R1 (A, B, C, D, 8, 3);
      R1 (D, A, B, C, 9, 7);
      R1 (C, D, A, B, 10, 11);
      R1 (B, C, D, A, 11, 19);
      R1 (A, B, C, D, 12, 3);
      R1 (D, A, B, C, 13, 7);
      R1 (C, D, A, B, 14, 11);
      R1 (B, C, D, A, 15, 19);

      /* Round 2.  */
      R2 (A, B, C, D, 0, 3);
      R2 (D, A, B, C, 4, 5);
      R2 (C, D, A, B, 8, 9);
      R2 (B, C, D, A, 12, 13);
      R2 (A, B, C, D, 1, 3);
      R2 (D, A, B, C, 5, 5);
      R2 (C, D, A, B, 9, 9);
      R2 (B, C, D, A, 13, 13);
      R2 (A, B, C, D, 2, 3);
      R2 (D, A, B, C, 6, 5);
      R2 (C, D, A, B, 10, 9);
      R2 (B, C, D, A, 14, 13);
      R2 (A, B, C, D, 3, 3);
      R2 (D, A, B, C, 7, 5);
      R2 (C, D, A, B, 11, 9);
      R2 (B, C, D, A, 15, 13);

      /* Round 3.  */
      R3 (A, B, C, D, 0, 3);
      R3 (D, A, B, C, 8, 9);
      R3 (C, D, A, B, 4, 11);
      R3 (B, C, D, A, 12, 15);
      R3 (A, B, C, D, 2, 3);
      R3 (D, A, B, C, 10, 9);
      R3 (C, D, A, B, 6, 11);
      R3 (B, C, D, A, 14, 15);
      R3 (A, B, C, D, 1, 3);
      R3 (D, A, B, C, 9, 9);
      R3 (C, D, A, B, 5, 11);
      R3 (B, C, D, A, 13, 15);
      R3 (A, B, C, D, 3, 3);
      R3 (D, A, B, C, 11, 9);
      R3 (C, D, A, B, 7, 11);
      R3 (B, C, D, A, 15, 15);

      A = ctx->A += A;
      B = ctx->B += B;
      C = ctx->C += C;
      D = ctx->D += D;
    }
}