/*
** ********************************************************************
** md4.c -- Implementation of MD4 Message Digest Algorithm           **
** Updated: 2/16/90 by Ronald L. Rivest                              **
** (C) 1990 RSA Data Security, Inc.                                  **
** ********************************************************************
*/

/*
** To use MD4:
**   -- Include md4.h in your program
**   -- Declare an MDstruct MD to hold the state of the digest
**          computation.
**   -- Initialize MD using MDbegin(&MD)
**   -- For each full block (64 bytes) X you wish to process, call
**          MD4Update(&MD,X,512)
**      (512 is the number of bits in a full block.)
**   -- For the last block (less than 64 bytes) you wish to process,
**          MD4Update(&MD,X,n)
**      where n is the number of bits in the partial block. A partial
**      block terminates the computation, so every MD computation
**      should terminate by processing a partial block, even if it
**      has n = 0.
**   -- The message digest is available in MD.buffer[0] ...
**      MD.buffer[3].  (Least-significant byte of each word
**      should be output first.)
**   -- You can print out the digest using MDprint(&MD)
*/

/* Implementation notes:
** This implementation assumes that ints are 32-bit quantities.
*/

#define TRUE  1
#define FALSE 0

/* Compile-time includes
*/
#include <stdio.h>
#include "md4.h"
#include "pppd.h"

/* Compile-time declarations of MD4 "magic constants".
*/
#define I0  0x67452301       /* Initial values for MD buffer */
#define I1  0xefcdab89
#define I2  0x98badcfe
#define I3  0x10325476
#define C2  013240474631     /* round 2 constant = sqrt(2) in octal */
#define C3  015666365641     /* round 3 constant = sqrt(3) in octal */
/* C2 and C3 are from Knuth, The Art of Programming, Volume 2
** (Seminumerical Algorithms), Second Edition (1981), Addison-Wesley.
** Table 2, page 660.
*/

#define fs1  3               /* round 1 shift amounts */
#define fs2  7
#define fs3 11
#define fs4 19
#define gs1  3               /* round 2 shift amounts */
#define gs2  5
#define gs3  9
#define gs4 13
#define hs1  3               /* round 3 shift amounts */
#define hs2  9
#define hs3 11
#define hs4 15

/* Compile-time macro declarations for MD4.
** Note: The "rot" operator uses the variable "tmp".
** It assumes tmp is declared as unsigned int, so that the >>
** operator will shift in zeros rather than extending the sign bit.
*/
#define f(X,Y,Z)             ((X&Y) | ((~X)&Z))
#define g(X,Y,Z)             ((X&Y) | (X&Z) | (Y&Z))
#define h(X,Y,Z)             (X^Y^Z)
#define rot(X,S)             (tmp=X,(tmp<<S) | (tmp>>(32-S)))
#define ff(A,B,C,D,i,s)      A = rot((A + f(B,C,D) + X[i]),s)
#define gg(A,B,C,D,i,s)      A = rot((A + g(B,C,D) + X[i] + C2),s)
#define hh(A,B,C,D,i,s)      A = rot((A + h(B,C,D) + X[i] + C3),s)

/* MD4print(MDp)
** Print message digest buffer MDp as 32 hexadecimal digits.
** Order is from low-order byte of buffer[0] to high-order byte of
** buffer[3].
** Each byte is printed with high-order hexadecimal digit first.
** This is a user-callable routine.
*/
void
MD4Print(MDp)
MD4_CTX *MDp;
{
  int i,j;
  for (i=0;i<4;i++)
    for (j=0;j<32;j=j+8)
      printf("%02x",(MDp->buffer[i]>>j) & 0xFF);
}

/* MD4Init(MDp)
** Initialize message digest buffer MDp.
** This is a user-callable routine.
*/
void
MD4Init(MDp)
MD4_CTX *MDp;
{
  int i;
  MDp->buffer[0] = I0;
  MDp->buffer[1] = I1;
  MDp->buffer[2] = I2;
  MDp->buffer[3] = I3;
  for (i=0;i<8;i++) MDp->count[i] = 0;
  MDp->done = 0;
}

/* MDblock(MDp,X)
** Update message digest buffer MDp->buffer using 16-word data block X.
** Assumes all 16 words of X are full of data.
** Does not update MDp->count.
** This routine is not user-callable.
*/
static void
MDblock(MDp,Xb)
MD4_CTX *MDp;
unsigned char *Xb;
{
  register unsigned int tmp, A, B, C, D;
  unsigned int X[16];
  int i;

  for (i = 0; i < 16; ++i) {
    X[i] = Xb[0] + (Xb[1] << 8) + (Xb[2] << 16) + (Xb[3] << 24);
    Xb += 4;
  }

  A = MDp->buffer[0];
  B = MDp->buffer[1];
  C = MDp->buffer[2];
  D = MDp->buffer[3];
  /* Update the message digest buffer */
  ff(A , B , C , D ,  0 , fs1); /* Round 1 */
  ff(D , A , B , C ,  1 , fs2);
  ff(C , D , A , B ,  2 , fs3);
  ff(B , C , D , A ,  3 , fs4);
  ff(A , B , C , D ,  4 , fs1);
  ff(D , A , B , C ,  5 , fs2);
  ff(C , D , A , B ,  6 , fs3);
  ff(B , C , D , A ,  7 , fs4);
  ff(A , B , C , D ,  8 , fs1);
  ff(D , A , B , C ,  9 , fs2);
  ff(C , D , A , B , 10 , fs3);
  ff(B , C , D , A , 11 , fs4);
  ff(A , B , C , D , 12 , fs1);
  ff(D , A , B , C , 13 , fs2);
  ff(C , D , A , B , 14 , fs3);
  ff(B , C , D , A , 15 , fs4);
  gg(A , B , C , D ,  0 , gs1); /* Round 2 */
  gg(D , A , B , C ,  4 , gs2);
  gg(C , D , A , B ,  8 , gs3);
  gg(B , C , D , A , 12 , gs4);
  gg(A , B , C , D ,  1 , gs1);
  gg(D , A , B , C ,  5 , gs2);
  gg(C , D , A , B ,  9 , gs3);
  gg(B , C , D , A , 13 , gs4);
  gg(A , B , C , D ,  2 , gs1);
  gg(D , A , B , C ,  6 , gs2);
  gg(C , D , A , B , 10 , gs3);
  gg(B , C , D , A , 14 , gs4);
  gg(A , B , C , D ,  3 , gs1);
  gg(D , A , B , C ,  7 , gs2);
  gg(C , D , A , B , 11 , gs3);
  gg(B , C , D , A , 15 , gs4);
  hh(A , B , C , D ,  0 , hs1); /* Round 3 */
  hh(D , A , B , C ,  8 , hs2);
  hh(C , D , A , B ,  4 , hs3);
  hh(B , C , D , A , 12 , hs4);
  hh(A , B , C , D ,  2 , hs1);
  hh(D , A , B , C , 10 , hs2);
  hh(C , D , A , B ,  6 , hs3);
  hh(B , C , D , A , 14 , hs4);
  hh(A , B , C , D ,  1 , hs1);
  hh(D , A , B , C ,  9 , hs2);
  hh(C , D , A , B ,  5 , hs3);
  hh(B , C , D , A , 13 , hs4);
  hh(A , B , C , D ,  3 , hs1);
  hh(D , A , B , C , 11 , hs2);
  hh(C , D , A , B ,  7 , hs3);
  hh(B , C , D , A , 15 , hs4);
  MDp->buffer[0] += A;
  MDp->buffer[1] += B;
  MDp->buffer[2] += C;
  MDp->buffer[3] += D;
}

/* MD4Update(MDp,X,count)
** Input: X -- a pointer to an array of unsigned characters.
**        count -- the number of bits of X to use.
**          (if not a multiple of 8, uses high bits of last byte.)
** Update MDp using the number of bits of X given by count.
** This is the basic input routine for an MD4 user.
** The routine completes the MD computation when count < 512, so
** every MD computation should end with one call to MD4Update with a
** count less than 512.  A call with count 0 will be ignored if the
** MD has already been terminated (done != 0), so an extra call with
** count 0 can be given as a "courtesy close" to force termination
** if desired.
*/
void
MD4Update(MDp,X,count)
MD4_CTX *MDp;
unsigned char *X;
unsigned int count;
{
  unsigned int i, tmp, bit, byte, mask;
  unsigned char XX[64];
  unsigned char *p;

  /* return with no error if this is a courtesy close with count
  ** zero and MDp->done is true.
  */
  if (count == 0 && MDp->done) return;
  /* check to see if MD is already done and report error */
  if (MDp->done)
  { printf("\nError: MD4Update MD already done."); return; }

  /* Add count to MDp->count */
  tmp = count;
  p = MDp->count;
  while (tmp)
  { tmp += *p;
  *p++ = tmp;
  tmp = tmp >> 8;
  }

  /* Process data */
  if (count == 512)
  { /* Full block of data to handle */
    MDblock(MDp,X);
  }
  else if (count > 512) /* Check for count too large */
  {
    printf("\nError: MD4Update called with illegal count value %d.",
	   count);
    return;
  }
  else /* partial block -- must be last block so finish up */
  {
    /* Find out how many bytes and residual bits there are */
    byte = count >> 3;
    bit =  count & 7;
    /* Copy X into XX since we need to modify it */
    for (i=0;i<=byte;i++)   XX[i] = X[i];
    for (i=byte+1;i<64;i++) XX[i] = 0;
    /* Add padding '1' bit and low-order zeros in last byte */
    mask = 1 << (7 - bit);
    XX[byte] = (XX[byte] | mask) & ~( mask - 1);
    /* If room for bit count, finish up with this block */
    if (byte <= 55)
    {
      for (i=0;i<8;i++) XX[56+i] = MDp->count[i];
      MDblock(MDp,XX);
    }
    else /* need to do two blocks to finish up */
    {
      MDblock(MDp,XX);
      for (i=0;i<56;i++) XX[i] = 0;
      for (i=0;i<8;i++)  XX[56+i] = MDp->count[i];
      MDblock(MDp,XX);
    }
    /* Set flag saying we're done with MD computation */
    MDp->done = 1;
  }
}

/*
** Finish up MD4 computation and return message digest.
*/
void
MD4Final(buf, MD)
unsigned char *buf;
MD4_CTX *MD;
{
  int i, j;
  unsigned int w;

  MD4Update(MD, NULL, 0);
  for (i = 0; i < 4; ++i) {
    w = MD->buffer[i];
    for (j = 0; j < 4; ++j) {
      *buf++ = w;
      w >>= 8;
    }
  }
}

/*
** End of md4.c
****************************(cut)***********************************/
