/*
*
* Adobe's encryption/decryption algorithm for eexec and show. Runs in
* eexec mode unless told otherwise. Use,
*
*              pscrypt file.cypher > file.clear
*
* to decrypt eexec input. Assumes file.cypher is hex with the key as the
* first four bytes, and writes file.clear as binary (omitting the key).
* Use
*
*              pscrypt -e12ab34ef file.clear >file.cypher
*
* to encrypt file.clear (for eexec) using 12ab34ef as the key. Input is
* binary and output is hex. The key must be given as a hex number. Use
* -sshow to encrypt or decrypt a CharString or Subr,
*
*              pscrypt -sshow file.cypher > file.clear
*
* Use -b or -x to read binary or hex input, and -B or -X to output binary
* or hex.
*
*/

#include <stdio.h>
#include <ctype.h>

#define ENCRYPT         0
#define DECRYPT         1

#define NOTSET          -1
#define BINARY          0
#define HEX             1
#define LINELENGTH      40

#define CHARSTRING      4330
#define EEXEC           55665
#define MAGIC1          52845
#define MAGIC2          22719

int     argc;
char    **argv;

int     mode = DECRYPT;
int     input = NOTSET;
int     output = NOTSET;
int     outoffset = NOTSET;
int     inoffset = NOTSET;

int     cryptkey = 0;                   /* encryption key set with -e */
int     linelength = LINELENGTH;        /* only for hex output */
int     lastchar = 0;

unsigned long   seed = EEXEC;
unsigned long   key;

FILE    *fp_in = stdin;

/*****************************************************************************/

main(agc, agv)

   int         agc;
   char        *agv[];

{

/*
*
* Implementation of the encryption/decryption used by eexec and show.
*
*/

   argc = agc;
   argv = agv;

   options();
   initialize();
   arguments();

   exit(0);

}   /* End of main */

/*****************************************************************************/

options()

{

   int         ch;
   char        *names = "bde:l:os:xBSX";

   extern char *optarg;
   extern int  optind;

/*
*
* Command line options.
*
*/

   while ( (ch = getopt(argc, argv, names)) != EOF )
       switch ( ch ) {
           case 'b':                   /* binary input */
                   input = BINARY;
                   break;

           case 'd':                   /* decrypt */
                   mode = DECRYPT;
                   break;

           case 'e':                   /* encrypt */
                   mode = ENCRYPT;
                   if ( *optarg == '0' && *optarg == 'x' )
                       optarg += 2;
                   sscanf(optarg, "%8x", &cryptkey);
                   break;

           case 'l':                   /* line length hex output */
                   linelength = atoi(optarg);
                   break;

           case 'o':                   /* output all bytes - debugging */
                   outoffset = 0;
                   break;

           case 's':                   /* seed */
                   if ( *optarg == 'e' )
                       seed = EEXEC;
                   else if ( *optarg == 's' )
                       seed = CHARSTRING;
                   else if ( *optarg == '0' && *(optarg+1) == 'x' )
                       sscanf(optarg+2, "%x", &seed);
                   else if ( *optarg == '0' )
                       sscanf(optarg, "%o", &seed);
                   else sscanf(optarg, "%d", &seed);
                   break;

           case 'x':                   /* hex input */
                   input = HEX;
                   break;

           case 'B':                   /* binary output */
                   output = BINARY;
                   break;

           case 'X':                   /* hex output */
                   output = HEX;
                   break;

           case '?':                   /* don't understand the option */
                   fprintf(stderr, "bad option -%c\n", ch);
                   exit(1);
                   break;

           default:                    /* don't know what to do for ch */
                   fprintf(stderr, "missing case for option -%c\n", ch);
                   exit(1);
                   break;
       }   /* End switch */

   argc -= optind;                     /* get ready for non-option args */
   argv += optind;

}   /* End of options */

/*****************************************************************************/

initialize()

{

/*
*
* Initialization that has to be done after the options.
*
*/

   key = seed;

   if ( mode == DECRYPT ) {
       input = (input == NOTSET) ? HEX : input;
       output = (output == NOTSET) ? BINARY : output;
       inoffset = (inoffset == NOTSET) ? 0 : inoffset;
       outoffset = (outoffset == NOTSET) ? -4 : outoffset;
   } else {
       input = (input == NOTSET) ? BINARY : input;
       output = (output == NOTSET) ? HEX : output;
       inoffset = (inoffset == NOTSET) ? 4 : inoffset;
       outoffset = (outoffset == NOTSET) ? 0 : outoffset;
   }   /* End else */

   if ( linelength <= 0 )
       linelength = LINELENGTH;

}   /* End of initialize */

/*****************************************************************************/

arguments()

{

/*
*
* Everything left is an input file. No arguments or '-' means stdin.
*
*/

   if ( argc < 1 )
       crypt();
   else
       while ( argc > 0 ) {
           if ( strcmp(*argv, "-") == 0 )
               fp_in = stdin;
           else if ( (fp_in = fopen(*argv, "r")) == NULL ) {
               fprintf(stderr, "can't open %s\n", *argv);
               exit(1);
           }   /* End if */
           crypt();
           if ( fp_in != stdin )
               fclose(fp_in);
           argc--;
           argv++;
       }   /* End while */

}   /* End of arguments */

/*****************************************************************************/

crypt()

{

   unsigned int        cypher;
   unsigned int        clear;

/*
*
* Runs the encryption/decryption algorithm.
*
*/

   while ( lastchar != EOF ) {
       cypher = nextbyte();
       clear = ((key >> 8) ^ cypher) & 0xFF;
       key = (key + (mode == DECRYPT ? cypher : clear)) * MAGIC1 + MAGIC2;
       if ( ++outoffset > 0 && lastchar != EOF ) {
           if ( output == HEX ) {
               printf("%.2X", clear);
               if ( linelength > 0 && (outoffset % linelength) == 0 )
                   putchar('\n');
           } else putchar(clear);
       }   /* End if */
   }   /* End while */

}   /* End of crypt */

/*****************************************************************************/

nextbyte()

{

   int         val = EOF;

/*
*
* Returns the next byte. Uses cryptkey (i.e. what followed -e) while inoffset is
* positive, otherwise reads (hex or binary) from fp_in.
*
*/

   if ( inoffset-- > 0 )
       val = (cryptkey >> (inoffset*8)) & 0xFF;
   else if ( input == HEX ) {
       if ( (val = nexthexchar()) != EOF )
           val = (val << 4) | nexthexchar();
   } else if ( input == BINARY )
       val = Getc(fp_in);

   return(val);

}   /* End of nextbyte */

/*****************************************************************************/

nexthexchar()

{

   int         ch;

/*
*
* Reads the next hex character.
*
*/

   while ( (ch = Getc(fp_in)) != EOF && ! isxdigit(ch) ) ;

   if ( isdigit(ch) )
       ch -= '0';
   else if ( isupper(ch) )
       ch -= 'A' - 10;
   else if ( islower(ch) )
       ch -= 'a' - 10;

   return(ch);

}   /* End of nexthexchar */

/*****************************************************************************/

Getc(fp)

   FILE        *fp;

{

/*
*
* Reads the next byte from *fp, sets lastchar, and returns the character.
*
*/

   return(lastchar = getc(fp));

}   /* End of Getc */

/*****************************************************************************/

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