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/* $Id: des.c,v 1.2 1996/12/12 00:04:44 baskar Exp $ */

/*
 *  @(#)des.c	26.3 (96/01/02 15:21:37)
    Copyright 1995 Ascend Communications, Inc.
    All rights reserved.
    Use of copyright notice does not imply publication.
 */

/* des.c,  /appletalk/source,  Garth Conboy,  10/05/88  */
/* Public domain code.  */

/* FILE: DES.C
 * Overview:  This file contains routines that implement software
 * 	DES functions.
 *
 */

#include <assert.h>
#include <sys/types.h>
#include <netinet/in.h>
#include "radius.h"
#include "des.h"

/* Static routines */

static void spinit P__((void));
static void perminit P__((char perm[16][16][8], char p[64]));
static void permute P__((char *inblock, char perm[16][16][8],char *outblock));
static void round P__((int num, long unsigned *block));
static long unsigned f P__((long unsigned r, unsigned char subkey[8]));


/* Tables defined in the Data Encryption Standard documents */

/* initial permutation IP */
static char ip[] = {
  58, 50, 42, 34, 26, 18, 10, 2,
  60, 52, 44, 36, 28, 20, 12, 4,
  62, 54, 46, 38, 30, 22, 14, 6,
  64, 56, 48, 40, 32, 24, 16, 8,
  57, 49, 41, 33, 25, 17, 9, 1,
  59, 51, 43, 35, 27, 19, 11, 3,
  61, 53, 45, 37, 29, 21, 13, 5,
  63, 55, 47, 39, 31, 23, 15, 7
};

/* final permutation IP^-1 */
static char fp[] = {
  40, 8, 48, 16, 56, 24, 64, 32,
  39, 7, 47, 15, 55, 23, 63, 31,
  38, 6, 46, 14, 54, 22, 62, 30,
  37, 5, 45, 13, 53, 21, 61, 29,
  36, 4, 44, 12, 52, 20, 60, 28,
  35, 3, 43, 11, 51, 19, 59, 27,
  34, 2, 42, 10, 50, 18, 58, 26,
  33, 1, 41, 9, 49, 17, 57, 25
};

/*
 * expansion operation matrix This is for reference only; it is unused in the
 * code as the f() function performs it implicitly for speed
 */

#if 0
static char ei[] = {
  32, 1, 2, 3, 4, 5,
  4, 5, 6, 7, 8, 9,
  8, 9, 10, 11, 12, 13,
  12, 13, 14, 15, 16, 17,
  16, 17, 18, 19, 20, 21,
  20, 21, 22, 23, 24, 25,
  24, 25, 26, 27, 28, 29,
  28, 29, 30, 31, 32, 1
};

#endif

/* permuted choice table (key) */
static char pc1[] = {
  57, 49, 41, 33, 25, 17, 9,
  1, 58, 50, 42, 34, 26, 18,
  10, 2, 59, 51, 43, 35, 27,
  19, 11, 3, 60, 52, 44, 36,

  63, 55, 47, 39, 31, 23, 15,
  7, 62, 54, 46, 38, 30, 22,
  14, 6, 61, 53, 45, 37, 29,
  21, 13, 5, 28, 20, 12, 4
};

/* number left rotations of pc1 */
static char totrot[] = {
  1, 2, 4, 6, 8, 10, 12, 14, 15, 17, 19, 21, 23, 25, 27, 28
};

/* permuted choice key (table) */
static char pc2[] = {
  14, 17, 11, 24, 1, 5,
  3, 28, 15, 6, 21, 10,
  23, 19, 12, 4, 26, 8,
  16, 7, 27, 20, 13, 2,
  41, 52, 31, 37, 47, 55,
  30, 40, 51, 45, 33, 48,
  44, 49, 39, 56, 34, 53,
  46, 42, 50, 36, 29, 32
};

/* The (in)famous S-boxes */
static char si[8][64] = {
  /* S1 */ {
  14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
  0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
  4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
  15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13,
  },

  /* S2 */ {
  15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
  3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
  0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
  13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9,
  },

  /* S3 */ {
  10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
  13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
  13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
  1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12,
  },

  /* S4 */ {
  7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
  13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
  10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
  3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14,
  },

  /* S5 */ {
  2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
  14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
  4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
  11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3,
  },

  /* S6 */ {
  12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
  10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
  9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
  4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13,
  },

  /* S7 */ {
  4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
  13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
  1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
  6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12,
  },

  /* S8 */ {
  13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
  1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
  7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
  2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11
  }
};

/* 32-bit permutation function P used on the output of the S-boxes */
static char p32i[] = {
  16, 7, 20, 21,
  29, 12, 28, 17,
  1, 15, 23, 26,
  5, 18, 31, 10,
  2, 8, 24, 14,
  32, 27, 3, 9,
  19, 13, 30, 6,
  22, 11, 4, 25
};

/* End of DES-defined tables */

/* Lookup tables initialized once only at startup by desinit() */
static long (*sp)[64];		/* Combined S and P boxes */

static char (*iperm)[16][8];	/* Initial and final permutations */
static char (*fperm)[16][8];

/* 8 6-bit subkeys for each of 16 rounds, initialized by setkey() */
static unsigned char (*kn)[8];

/* bit 0 is left-most in byte */
static int bytebit[] = {
  0200, 0100, 040, 020, 010, 04, 02, 01
};

static int nibblebit[] = {
  010, 04, 02, 01
};
static int desmode;

/*
 * Allocate space and initialize DES lookup arrays mode == 0: standard Data
 * Encryption Algorithm mode == 1: DEA without initial and final permutations
 * for speed mode == 2: DEA without permutations and with 128-byte key
 * (completely independent subkeys for each round)
 * for now I assume that this is called with mode 0.
 */

int 
des_init()
{
  int mode   = 0;


  if (sp != 0) {		/* Already inited? */
    /* If the tables are already allocated don't alloca again. */
    return( MEMORY_ERR );
  }

  desmode = mode;

  if ((sp = (long (*)[64]) malloc(sizeof(long) * 8 * 64)) == 0) {
    return( MEMORY_ERR );
  }

  spinit();
  if ((kn = (unsigned char (*)[8]) malloc(sizeof(char) * 8 * 16)) == 0) {
    free(sp);
    return( MEMORY_ERR );
  }
  if (mode == 1 || mode == 2)	/* No permutations */
    return( MEMORY_ERR ) ;

  if ((iperm = (char (*)[16][8]) malloc(sizeof(char) * 16 * 16 * 8)) == 0) {
    free(sp);
    free(kn);
    return( MEMORY_ERR );
  }
  perminit(iperm, ip);

  if ((fperm = (char (*)[16][8]) malloc(sizeof(char) * 16 * 16 * 8)) == 0) {
    free(sp);
    free(kn);
    free(iperm);
    return( MEMORY_ERR );
  }
  perminit(fperm, fp);
  return(0);
}				/* desinit */

/* Free up storage used by DES */
void 
desdone()
{
  if (sp == 0)
    return;			/* Already done */

  free(sp);
  free(kn);
  if (iperm != 0)
    free(iperm);
  if (fperm != 0)
    free(fperm);

  sp = 0;
  iperm = 0;
  fperm = 0;
  kn = 0;

}				/* desdone */

/* Set key (initialize key schedule array) */

void 
dessetkey(key)
char *key;
{				/* 64 bits (will use only 56) */
  char pc1m[56];		/* place to modify pc1 into */
  char pcr[56];			/* place to rotate pc1 into */

  register int i, j, l;
  int m;

  /*
   * In mode 2, the 128 bytes of subkey are set directly from the user's key,
   * allowing him to use completely independent subkeys for each round. Note
   * that the user MUST specify a full 128 bytes.
   * 
   * I would like to think that this technique gives the NSA a real headache,
   * but I'm not THAT naive.
   */

  if (desmode == 2) {
    for (i = 0; i < 16; i++)
      for (j = 0; j < 8; j++)
	kn[i][j] = *key++;
    return;
  }
  /* Clear key schedule */

  for (i = 0; i < 16; i++)
    for (j = 0; j < 8; j++)
      kn[i][j] = 0;

  for (j = 0; j < 56; j++) {	/* convert pc1 to bits of key */
    l = pc1[j] - 1;		/* integer bit location  */
    m = l & 07;			/* find bit              */
    pc1m[j] = (char) ((key[l >> 3] &	/* find which key byte l is in */
		       bytebit[m])	/* and which bit of that byte */
		      ? 1 : 0);	/* and store 1-bit result */
  }

  for (i = 0; i < 16; i++) {	/* key chunk for each iteration */
    for (j = 0; j < 56; j++)	/* rotate pc1 the right amount */
      pcr[j] = pc1m[(l = j + totrot[i]) < (j < 28 ? 28 : 56) ? l : l - 28];

    /* rotate left and right halves independently */

    for (j = 0; j < 48; j++) {	/* select bits individually */
      /* check bit that goes to kn[j] */

      if (pcr[pc2[j] - 1]) {
	/* mask it in if it's there */

	l = j % 6;
	kn[i][j / 6] |= (unsigned char) (bytebit[l] >> 2);
      }
    }
  }

}				/* setkey */

/* In-place encryption of 64-bit block */

void 
endes(block)
char *block;
{
  register int i;
  unsigned long work[2];	/* Working data storage */
  long unsigned tmp;

  permute(block, iperm, (char *) work);	/* Initial Permutation */

  work[0] = ntohl(work[0]);
  work[1] = ntohl(work[1]);

  /* Do the 16 rounds */

  for (i = 0; i < 16; i++)
    round(i, work);

  /* Left/right half swap */

  tmp = work[0];
  work[0] = work[1];
  work[1] = tmp;

  work[0] = ntohl(work[0]);
  work[1] = ntohl(work[1]);

  permute((char *) work, fperm, block);	/* Inverse initial permutation */

}				/* endes */

/* In-place decryption of 64-bit block */

void 
dedes(block)
char *block;
{
  register int i;
  unsigned long work[2];	/* Working data storage */
  long unsigned tmp;

  permute(block, iperm, (char *) work);	/* Initial permutation */

  work[0] = ntohl(work[0]);
  work[1] = ntohl(work[1]);

  /* Left/right half swap */

  tmp = work[0];
  work[0] = work[1];
  work[1] = tmp;

  /* Do the 16 rounds in reverse order */

  for (i = 15; i >= 0; i--)
    round(i, work);

  work[0] = ntohl(work[0]);
  work[1] = ntohl(work[1]);

  permute((char *) work, fperm, block);	/* Inverse initial permutation */

}				/* dedes */

/* Permute inblock with perm */

static void 
permute(inblock,
	perm,	/* 2K bytes defining perm. */
	outblock)
char *inblock;
char perm[16][16][8];
char *outblock;
{				/* result into outblock,64 bits */
  register int i, j;
  register char *ib, *ob;	/* ptr to input or output block */
  register char *p, *q;

  if (perm == 0) {
    /* No permutation, just copy */

    for (i = 8; i != 0; i--)
      *outblock++ = *inblock++;
    return;
  }
  /* Clear output block */

  for (i = 8, ob = outblock; i != 0; i--)
    *ob++ = 0;

  ib = inblock;
  for (j = 0; j < 16; j += 2, ib++) {	/* for each input nibble */
    ob = outblock;
    p = perm[j][(*ib >> 4) & 017];
    q = perm[j + 1][*ib & 017];
    for (i = 8; i != 0; i--)	/* and each output byte */
      *ob++ |= (char) (*p++ | *q++);	/* OR the masks together */
  }

}				/* permute */

/* Do one DES cipher round */

static void 
round(num,			/* i.e. the num-th one   */
      block)
int num;
long unsigned *block;
{

  /*
   * The rounds are numbered from 0 to 15. On even rounds the right half is
   * fed to f() and the result exclusive-ORs the left half; on odd rounds the
   * reverse is done.
   */

  if (num & 1)
    block[1] ^= f(block[0], kn[num]);
  else
    block[0] ^= f(block[1], kn[num]);

}				/* round */

/* The nonlinear function f(r,k), the heart of DES */

static long unsigned 
f(r,		/* 32 bits */
  subkey)
long unsigned r;
unsigned char subkey[8];
{				/* 48-bit key for this round */
  register unsigned long rval, rt;

#ifdef  TRACE
  unsigned char *cp;
  int i;

  NU_printf("f(%08lx, %02x %02x %02x %02x %02x %02x %02x %02x) = ",
	    r,
	    subkey[0], subkey[1], subkey[2],
	    subkey[3], subkey[4], subkey[5],
	    subkey[6], subkey[7]);
#endif

  /*
   * Run E(R) ^ K through the combined S & P boxes This code takes advantage
   * of a convenient regularity in E, namely that each group of 6 bits in
   * E(R) feeding a single S-box is a contiguous segment of R.
   */

  rt = (r >> 1) | ((r & 1) ? (long unsigned) 0x80000000 : (long unsigned) 0);
  rval = 0;
  rval |= (long unsigned) sp[0][((rt >> 26) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[1][((rt >> 22) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[2][((rt >> 18) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[3][((rt >> 14) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[4][((rt >> 10) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[5][((rt >> 6) ^ *subkey++) & 0x3f];
  rval |= (long unsigned) sp[6][((rt >> 2) ^ *subkey++) & 0x3f];
  rt = (r << 1) | ((r & 0x80000000) ? (long unsigned) 1 : (long unsigned) 0);
  rval |= (long unsigned) sp[7][(rt ^ *subkey) & 0x3f];

#ifdef  TRACE
  NU_printf(" %08lx\n", rval);
#endif

  return (rval);

}				/* f */

/* Initialize a perm array */

static void 
perminit(perm,	/* 64-bit, either init or final */
	 p)
char perm[16][16][8];
char p[64];
{
  register int l, j, k;
  int i, m;

  /* Clear the permutation array */

  for (i = 0; i < 16; i++)
    for (j = 0; j < 16; j++)
      for (k = 0; k < 8; k++)
	perm[i][j][k] = 0;

  for (i = 0; i < 16; i++)	/* each input nibble position */
    for (j = 0; j < 16; j++)	/* each possible input nibble */
      for (k = 0; k < 64; k++) {/* each output bit position */
	l = p[k] - 1;		/* where does this bit come from */
	if ((l >> 2) != i)	/* does it come from input position? */
	  continue;		/* if not, bit k is 0 */
	if (!(j & nibblebit[l & 3]))
	  continue;		/* any such bit in input? */
	m = k & 07;		/* which bit is this in the byte */
	perm[i][j][k >> 3] |= (char) bytebit[m];
      }

}				/* perminit */

/* Initialize the lookup table for the combined S and P boxes */
static void 
spinit()
{
  char pbox[32];

  int p, i, s, j, rowcol;
  long val;

  /* Compute pbox, the inverse of p32i.  This is easier to work with. */

  for (p = 0; p < 32; p++)
    for (i = 0; i < 32; i++)
      if (p32i[i] - 1 == p) {
	pbox[p] = (char) i;
	break;
      }
  for (s = 0; s < 8; s++)	/* For each S-box */
    for (i = 0; i < 64; i++) {	/* For each possible input */
      val = 0;

      /*
       * The row number is formed from the first and last bits; the column
       * number is from the middle 4
       */

      rowcol = (i & 32) | ((i & 1) ? 16 : 0) | ((i >> 1) & 0xf);
      for (j = 0; j < 4; j++)	/* For each output bit */
	if (si[s][rowcol] & (8 >> (short) j))
	  val |= 1L << (short) (31 - pbox[4 * s + j]);

      sp[s][i] = val;

    }

}				/* spinit */

