/********************************************************************
 * $Author: jgoerzen $
 * $Revision: 1.3 $
 * $Date: 2001/01/17 19:30:25 $
 * $Source: /var/cvs/gopher/gopherd/authenticate.c,v $
 * $State: Exp $
 *
 * Paul Lindner, University of Minnesota CIS.
 *
 * Copyright 1991, 1992, 1993 by the Regents of the University of Minnesota
 * see the file "Copyright" in the distribution for conditions of use.
 *********************************************************************
 * MODULE: authenticate.c
 * Routines to do encryption and decryption, and validate tickets
 *********************************************************************
 * Revision History:
 * $Log: authenticate.c,v $
 * Revision 1.3  2001/01/17 19:30:25  jgoerzen
 * Change many sprintf -> snprintf
 *
 * Revision 1.2  2000/12/20 01:19:20  jgoerzen
 * Added patches from David Allen <s2mdalle@titan.vcu.edu>
 *
 * Revision 1.1.1.1  2000/08/19 00:28:56  jgoerzen
 * Import from UMN Gopher 2.3.1 after GPLization
 *
 * Revision 3.20  1995/09/25  05:02:30  lindner
 * Convert to ANSI C
 *
 * Revision 3.19  1995/04/15  07:12:08  lindner
 * Minor fixes
 *
 * Revision 3.18  1995/02/11  06:19:25  lindner
 * allocate proper amount of space for des routines
 *
 * Revision 3.17  1995/02/07  07:02:23  lindner
 * performance fixes
 *
 * Revision 3.16  1994/10/13  05:17:47  lindner
 * Compiler complaint fixes
 *
 * Revision 3.15  1994/07/22  22:28:01  lindner
 * NO_AUTHENTICATION mods
 *
 * Revision 3.14  1994/07/19  20:23:17  lindner
 * Remove unused vars
 *
 * Revision 3.13  1994/06/29  05:39:01  lindner
 * Add AUTH, remove admit1
 *
 * Revision 3.12  1994/02/20  16:51:57  lindner
 * Don't compile authentication stuff unless needed
 *
 * Revision 3.11  1993/11/02  05:55:48  lindner
 * Fix for interactive unix
 *
 * Revision 3.10  1993/09/18  03:28:05  lindner
 * Fix for Abort() fcn declaration
 *
 * Revision 3.9  1993/09/11  05:05:08  lindner
 * compiler warning fix
 *
 * Revision 3.8  1993/07/29  20:12:18  lindner
 * Removed dead variables
 *
 * Revision 3.7  1993/07/27  05:27:39  lindner
 * Mondo Debug overhaul from Mitra
 *
 * Revision 3.6  1993/07/07  19:34:17  lindner
 * renamed encrypt() to UMNDESencrypt()
 *
 * Revision 3.5  1993/04/10  06:07:17  lindner
 * none
 *
 * Revision 3.4  1993/04/09  16:51:54  lindner
 * Little mods for combined public gopher and admit1 gopher.
 *
 * Revision 3.3  1993/04/07  05:16:57  lindner
 * Unhid changes for Admit1 stuff.
 *
 * Revision 3.1  1993/03/19  20:02:13  lindner
 * DES and ticket routines
 *
 *
 *********************************************************************/

#include "String.h"
#include <stdio.h>

#include "gopherd.h"
#include "command.h"

/* -------------------------------------------------
 *
 * Sofware DES functions 12 Dec 1986 by Phil Karn, KA9Q;
 * large sections from 1977 public-domain program by Jim Gillogly
 * Modified by George Gonzalez to not do initial/final permutations
 * Further bludgeoned by Farhad Anklesaria for AdmitOne authentication.
 *
 ---------------------------------------------------- */

#ifndef NO_AUTHENTICATION


typedef unsigned int Desnum;


#define  SLEN 255  /* Generic small buffer length */
#include "Debug.h"

static int IntelOrder = 1;     /*Hacked out.  fxa*/

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

/* Lookup tables initialized once only at startup by desinit() */


  
/* bit 0 == left-most in byte */
static short bytebit[] = { 0200,0100,0040,0020,0010,0004,0002,0001 };
  
  
static unsigned char (*kn)[8];
static int (*spbox)[64]; /* Combined S && P boxes */

static void
DESAbort(char *text)
{
     if (text != NULL) fprintf(stderr,"%s",text);
     exit(-1);
}
  
#ifdef DES_TEST
void main()
{
     Desnum bkey[3];
     char *entext;
     DEBUG =1;

     entext = GDESencrypt("lindner", "156.106.128.92", "uglyduck", "lindner");

     desdone();
     desinit();
     GDESdecrypt("lindner", "156.106.128.92", "uglyduck", entext);

}
#endif


/*--------------------------------*/
/* Initialize the lookup table for the combined S && P boxes */
static void 
spinit()
{
     char pbox[ 32 ];
     short p, i, s, j, t, rowcol;
     int val;
     
     for ( p = 1; p <= 32; p++ ) {
	  for ( i = 0; i <= 31; i++ ) {
	       if ( p32i[i] == p ) {
		    pbox[p - 1] = 31 - i;
		    break;
	       }
	  }
     }
     for ( s = 0; s <= 7; s++ ) {
	  for ( i = 0; i <= 63; i++ ) {
	       val = 0;
	       rowcol = (i & 32) | ((i & 1) ? 16 : 0) | ((i >> 1) & 0xf);
	       t = si[s][rowcol];
	       for ( j = 0; j <= 3; j++ ) {
		    if ( t & ( 8 >> j ) ) {
			 val |= 1L << pbox[ ( s << 2 ) + j ];
		    }
	       }
	       spbox[s][i] = val;
	  }
     }
}


/*--------------------------------*/
/* Allocate space && initialize DES lookup arrays
 * mode == 1: DEA without initial && final permutations for speed
 */

static int
desinit()
{
     if ( spbox != 0 ) return 0; 
     
     spbox = ( int (*)[64] ) malloc( sizeof( int ) * 8 * 64);
     if ( spbox != 0) { 
	  spinit();
	  kn = (unsigned char (*)[8]) malloc( sizeof( char ) * 8 * 16);
	  if ( kn == 0 ) {
	       free( (char *) spbox );
	       spbox = 0;
	  } 
     }
     if ( spbox == 0 || kn == 0 ) {
	  return -1;
     } else {
	  return 0;
     }
}

/*--------------------------------*/
/* Free up storage used by DES */

#if 0
static void
desdone()
{ 
     if (spbox != 0) {
	  free( (char *) spbox );
	  free( (char *) kn );
	  spbox = 0;
	  kn = 0;
     }
}
#endif /* 0 */


/*--------------------------------*/

static void setdeskey(Desnum *keynum) 
{
     unsigned char key[9];
     unsigned char pc1m[56];  /* place to modify pc1 into */
     unsigned char pcr[56];  /* place to rotate pc1 into */
     register short i, j, k;
     
     for (i=0,j=3; i<4; i++)
	  key[j--] = (keynum[0] >> (i*8)) & 0xFF;
     for (i=0,j=7; i<4; i++)
	  key[j--] = (keynum[1] >> (i*8)) & 0xFF;

     /* 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 */
	  k = pc1[j] - 1;
	  pc1m[j] = ( key[ k >> 3 ]  & bytebit[ k & 07 ]) ? 1 : 0;
     } 
     
     for (i=0; i<16; i++) {  /* key chunk for each iteration */
	  for (j=0; j<56; j++) { /* rotate pc1 the right amount */
	       k = j + totrot[i];
	       pcr[j] = pc1m[ k < ( j < 28 ? 28 : 56 ) ? k : k - 28 ];
	  }
	  for (j=0; j<48; j++) { /* select bits individually */
	       if ( pcr[ pc2[ j ] - 1 ] ) {
		    kn[i] [j/6] |= bytebit[j % 6] >> 2;
	       }
	  }
     }
}


/*--------------------------------*/

static void byteswap(Desnum *x ) 
{
     register char * cp;
     register char tmp;
     
     cp = (char *) x;
     tmp = cp[3];
     cp[3] = cp[0];
     cp[0] = tmp;
     
     tmp = cp[2];
     cp[2] = cp[1];
     cp[1] = tmp;
}

/*--------------------------------*/

static void mv(Desnum *in, Desnum *out)
{  
     out[0] = in[0];
     out[1] = in[1];

     if ( IntelOrder ) {
	  byteswap( (Desnum * ) &out[0] );
	  byteswap( (Desnum * ) &out[1] );
     }
}


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

static int f(Desnum r, unsigned char subkey[8])
{
     register Desnum rval, rt;
     
     /* Run E(R) ^ K through the combined S & P boxes
      * This ; takes advantage of a convenient regularity in
      * E, namely that each group of 6 bits in E(R) feeding
      * a single S-box == a contiguous segment of R.
      */
     rt = (r >> 1) | ((r & 1) ? 0x80000000 : 0);
     rval = 0;
     rval |= spbox[0][((rt >> 26) ^ *subkey++) & 0x3f];
     rval |= spbox[1][((rt >> 22) ^ *subkey++) & 0x3f];
     rval |= spbox[2][((rt >> 18) ^ *subkey++) & 0x3f];
     rval |= spbox[3][((rt >> 14) ^ *subkey++) & 0x3f];
     rval |= spbox[4][((rt >> 10) ^ *subkey++) & 0x3f];
     rval |= spbox[5][((rt >> 6) ^ *subkey++) & 0x3f];
     rval |= spbox[6][((rt >> 2) ^ *subkey++) & 0x3f];
     rt = (r << 1) | ((r & 0x80000000) ? 1 : 0);
     rval |= spbox[7][(rt ^ *subkey) & 0x3f];
     return rval;
}

/*--------------------------------*/

static void pass(short num, Desnum *block)
{
     short b;
     
     b = num & 1;
     block[ b ] ^= f( block[ 1 - b ], kn[ num ] );
}




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

static void endes(Desnum *block) 
{
     register short i;
     Desnum work[4];   /* Working data storage */
     Desnum tmp;
     
     mv( block, work ); /* Initial Permutation */
     for (i=0; i<16; i++)
	  pass( i, work );

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

     mv(work, block );
}



/*--------------------------------*/
/* In-place decryption of 64-bit block */
static void 
dedes(Desnum *block) 
{
     register short i;
     Desnum work[4]; /* Working data storage */
     Desnum tmp;
     ;
     mv( block, work ); /* Initial permutation */

     work[3] = 
     
     /* Left/right half swap */
     tmp = work[0];
     work[0] = work[1]; 
     work[1] = tmp;
     
     /* Do the 16 rounds in reverse order */
     for ( i = 0; i <=15; i++ )
	  pass( 15 - i, work );
     
     mv(work, block );
}

/*--------------------------------*/

static short Hx(char c)
{
     if ( c >= '0' && c <= '9' ) {
	  return( c - '0' );
     } else {
	  if ( c >= 'A' && c <= 'F' )
	       return( c - 'A' + 10 );
	  else if ( c >= 'a' && c <= 'f' )
	       return( c - 'a' + 10);
	  else
	       return( 0 );
     }
}


/*--------------------------------*/
/* Take a character string and convert it into two long ints 
*/

static void 
HexToBin(char * In, Desnum Out[])
{
     short i;
     int bytes[8];


     for (i=0; i < 8; i++) 
	  bytes[i] = (Hx(In[i*2]) * 16 ) + Hx(In[i*2 + 1]);

     Out[0] = (bytes[0]*16777216) + (bytes[1]*65536) + (bytes[2]*256) + bytes[3];

     Out[1] = (bytes[4]*16777216) + (bytes[5]*65536) + (bytes[6]*256) + bytes[7];

     Debug("Output of HextoBin is %X", Out[0]);
     Debug("%X\n", Out[1]);

}


/*--------------------------------*/

static void
GDESkey(char *user, char *ip, char *key, Desnum bkey[3])
{
     char          keystr[256];
     char         *cp;
     Desnum        c;
     int i, keysize;
     
/*     strcpy(keystr, user);
     strcat(keystr, ip);
     strcat(keystr, key); */
	i = keysize = sizeof(keystr)-1;
	strncpy(keystr, user, i), i -= strlen(keystr);
	strncat(keystr, ip, i), i -= strlen(keystr);
	strncat(keystr, key, i), keystr[keysize] = '\0';

     Debug("Encoding key %s\n", keystr);

     /** keystr contains our text key, encode it into a 64 bit # **/
     cp = keystr;
     
     bkey[0] = 0;
     bkey[1] = 0;

     while (*cp) {
	  for (i=0; *cp && i < 4; i++) {
	       c = *cp++;
	       bkey[0] ^= (c << (i*8));
	  }
	  for (i=0; *cp && i < 4; i++) {
	       c = *cp++;
	       bkey[1] ^= (c << (i*8));
	  }
     }
     

     Debug("Key is %lu", bkey[0]);
     Debug(" %lu\n", bkey[1]);
}


static int
GDESpackText(char *str, Desnum packedtext[])
{
     char *cp;
     int  longnum;
     int  i;

     cp      = str;
     longnum = 0;
     while (*cp) {
	  packedtext[longnum] = 0;
	  packedtext[longnum+1] = 0;

	  for (i=3; i >=0 && *cp; i--) {
	       packedtext[longnum] |= (*cp++ << (i*8));
	  }
	  longnum++;
     }
	       
     return(longnum);
}

static void
GDESunpackText(char *str, Desnum packedtext[], int numlongs)
{
     char *cp;
     int  i, x;

     cp      = str;

     for (i=0; i< numlongs; i++) {
	  for (x=3; x >= 0; x--) {
	       
	       *cp++ = (packedtext[i]>>(x*8)) & 0xFF;
	  }
     }
     Debug("Unpacked String: %s\n", str);
}

/*--------------------------------*/

char*
GDESencrypt(char *user, char *ip, char *key, char *cleartext)
{
     Desnum bkey[3];
     Desnum packedtext[10];
     int  longnum = 0;
     int  i;
     Desnum temp[3];
     char temptext[10];
     static char encoded[512];

     encoded[0] = '\0';
     for (i=0; i<10; i++) {
	  packedtext[i] = 0;
     }
     
     GDESkey(user, ip, key, bkey);

     if ( desinit() != 0 ) 
	  DESAbort("Error initializing DES.\n");
     
     longnum = GDESpackText(cleartext, packedtext);

     setdeskey( bkey);

     for (i = 0; i < longnum; i+=2) {
	  temp[0] = packedtext[i];
	  temp[1] = packedtext[i+1];

	  endes(temp);

	  snprintf(temptext, sizeof(temptext), "%.8X%.8X", temp[0] , temp[1]);
	  strcat(encoded, temptext);
	  Debug("Encoded: %s\n", temptext);
     }
     Debug("Encoded %s\n", encoded);

     return(encoded);
}


char *
GDESdecrypt(char *user, char *ip, char *key, char *codedtext)
{
     static char decoded[512];
     Desnum bkey[3];
     Desnum packedtext[10], temp[3];
     int           longnum = 0;
     char *cp;
     int i;

     decoded[0] = '\0';
     for (i=0; i<10; i++) {
	  packedtext[i] = 0;
     }

     if ( desinit() != 0 ) 
	  DESAbort("Error initializing DES.\n");

     GDESkey(user, ip, key, bkey);
     setdeskey(bkey);


     cp = codedtext;
     while (*cp) {
	  HexToBin(cp, temp);
	  dedes(temp);

	  packedtext[longnum] = temp[0];
	  packedtext[longnum+1] = temp[1];
	  longnum+=2;
	  cp += 16;
     }
     
     GDESunpackText(decoded, packedtext, longnum);

     return(decoded);
}
#endif