/* 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, 2008-2020 Free Software
   Foundation, Inc.

   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 3, or (at your option) any
   later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU 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>

#include "md4.h"

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

#if USE_UNLOCKED_IO
# include "unlocked-io.h"
#endif

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

#define BLOCKSIZE 32768
#if BLOCKSIZE % 64 != 0
# error "invalid BLOCKSIZE"
#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 bytes read from STREAM.  The
   resulting message digest number will be written into the 16 bytes
   beginning at RESBLOCK.  */
int
md4_stream (FILE * stream, void *resblock)
{
  struct md4_ctx ctx;
  size_t sum;

  char *buffer = malloc (BLOCKSIZE + 72);
  if (!buffer)
    return 1;

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

  /* Iterate over full file contents.  */
  while (1)
    {
      /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
         computation function processes the whole buffer so that with the
         next round of the loop another block can be read.  */
      size_t n;
      sum = 0;

      /* Read block.  Take care for partial reads.  */
      while (1)
        {
          n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);

          sum += n;

          if (sum == BLOCKSIZE)
            break;

          if (n == 0)
            {
              /* Check for the error flag IFF N == 0, so that we don't
                 exit the loop after a partial read due to e.g., EAGAIN
                 or EWOULDBLOCK.  */
              if (ferror (stream))
                {
                  free (buffer);
                  return 1;
                }
              goto process_partial_block;
            }

          /* We've read at least one byte, so ignore errors.  But always
             check for EOF, since feof may be true even though N > 0.
             Otherwise, we could end up calling fread after EOF.  */
          if (feof (stream))
            goto process_partial_block;
        }

      /* Process buffer with BLOCKSIZE bytes.  Note that
         BLOCKSIZE % 64 == 0
       */
      md4_process_block (buffer, BLOCKSIZE, &ctx);
    }

process_partial_block:;

  /* Process any remaining bytes.  */
  if (sum > 0)
    md4_process_bytes (buffer, sum, &ctx);

  /* Construct result in desired memory.  */
  md4_finish_ctx (&ctx, resblock);
  free (buffer);
  return 0;
}

/* 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;
    }
}
