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/*
** ********************************************************************
** 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
**          MDupdate(&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,
**          MDupdate(&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.
** If the machine stores the least-significant byte of an int in the
** least-addressed byte (e.g., VAX and 8086), then LOWBYTEFIRST
** should be set to TRUE.  Otherwise (e.g., SUNS), LOWBYTEFIRST
** should be set to FALSE.  Note that on machines with LOWBYTEFIRST
** FALSE the routine MDupdate modifies has a side-effect on its input
** array (the order of bytes in each word are reversed).  If this is
** undesired a call to MDreverse(X) can reverse the bytes of X back
** into order after each call to MDupdate.
**
** NOTE: LOWBYTEFIRST removed by Eric Rosenquist in favour of run-time
** detection to simplify build process.
*/

#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)

/* MDprint(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
MDprint(MDp)
MDptr 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);
}

/* MDbegin(MDp)
** Initialize message digest buffer MDp.
** This is a user-callable routine.
*/
void
MDbegin(MDp)
MDptr 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;
}

/* MDreverse(X)
** Reverse the byte-ordering of every int in X.
** Assumes X is an array of 16 ints.
** The macro revx reverses the byte-ordering of the next word of X.
*/
#define revx { t = (*X << 16) | (*X >> 16); \
  *X++ = ((t & 0xFF00FF00) >> 8) | ((t & 0x00FF00FF) << 8); }
MDreverse(X)
unsigned int *X;
{ register unsigned int t;
revx; revx; revx; revx; revx; revx; revx; revx;
revx; revx; revx; revx; revx; revx; revx; revx;
}

/* 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,X)
MDptr MDp;
unsigned int *X;
{
register unsigned int tmp, A, B, C, D;
static int low_byte_first = -1;

if (low_byte_first == -1) {
    low_byte_first = (htons((unsigned short int)1) != 1);
}

if (low_byte_first == 0) {
    MDreverse(X);
}

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;
}

/* MDupdate(MDp,X,count)
** Input: MDp -- an MDptr
**        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 MDupdate 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
MDupdate(MDp,X,count)
MDptr 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: MDupdate 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,(unsigned int *)X);
 }
else if (count > 512) /* Check for count too large */
 { printf("\nError: MDupdate 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,(unsigned int *)XX);
	 }
   else /* need to do two blocks to finish up */
	 { MDblock(MDp,(unsigned int *)XX);
	   for (i=0;i<56;i++) XX[i] = 0;
	   for (i=0;i<8;i++)  XX[56+i] = MDp->count[i];
	   MDblock(MDp,(unsigned int *)XX);
	 }
   /* Set flag saying we're done with MD computation */
   MDp->done = 1;
 }
}

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

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