source: crypting.c @ 07ff8a2

  /********************************************************************\
  * BitlBee -- An IRC to other IM-networks gateway                     *
  *                                                                    *
  * Copyright 2002-2004 Sjoerd Hemminga and others                     *
  \********************************************************************/

/* A little bit of encryption for the users' passwords                  */

/*
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License with
  the Debian GNU/Linux distribution in /usr/share/common-licenses/GPL;
  if not, write to the Free Software Foundation, Inc., 59 Temple Place,
  Suite 330, Boston, MA  02111-1307  USA
*/

/* [WvG] This file can also be compiled into a stand-alone program
   which can encode/decode BitlBee account files. The main() will be
   included if CRYPTING_MAIN is defined. Or just do "make decode" and
   the programs will be built. */

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <glib.h>
#include "md5.h"
#include "crypting.h"

/*\
 * [SH] Do _not_ call this if it's not entirely sure that it will not cause
 * harm to another users file, since this does not check the password for
 * correctness.
\*/

int checkpass (const char *pass, const char *md5sum)
{
        md5_state_t md5state;
        md5_byte_t digest[16];
        int i, j;
        char digits[3];
        
        md5_init (&md5state);
        md5_append (&md5state, (unsigned char *)pass, strlen (pass));
        md5_finish (&md5state, digest);
        
        for (i = 0, j = 0; i < 16; i++, j += 2) {
                /* Check password for correctness */
                g_snprintf (digits, sizeof (digits), "%02x\n", digest[i]);
                
                if (digits[0] != md5sum[j]) return (-1);
                if (digits[1] != md5sum[j + 1]) return (-1);
        }

        return( 0 );
}


char *hashpass (const char *password)
{
        md5_state_t md5state;
        md5_byte_t digest[16];
        int i;
        char digits[3];
        char *rv;
        
        if (password == NULL) return (NULL);
        
        rv = g_new0 (char, 33);
        
        md5_init (&md5state);
        md5_append (&md5state, (const unsigned char *)password, strlen (password));
        md5_finish (&md5state, digest);
        
        for (i = 0; i < 16; i++) {
                /* Build a hash of the pass */
                g_snprintf (digits, sizeof (digits), "%02x", digest[i]);
                strcat (rv, digits);
        }
        
        return (rv);
}

char *obfucrypt (char *line, const char *password) 
{
        int i, j;
        char *rv;
        
        if (password == NULL) return (NULL);
        
        rv = g_new0 (char, strlen (line) + 1);
        
        i = j = 0;
        while (*line) {
                /* Encrypt/obfuscate the line, using the password */
                if (*(signed char*)line < 0) *line = - (*line);
                
                rv[j] = *line + password[i]; /* Overflow intended */
                
                line++;
                if (!password[++i]) i = 0;
                j++;
        }
        
        return (rv);
}

char *deobfucrypt (char *line, const char *password) 
{
        int i, j;
        char *rv;
        
        if (password == NULL) return (NULL);
        
        rv = g_new0 (char, strlen (line) + 1);
        
        i = j = 0;
        while (*line) {
                /* Decrypt/deobfuscate the line, using the pass */
                rv[j] = *line - password[i]; /* Overflow intended */
                
                line++;
                if (!password[++i]) i = 0;
                j++;
        }
        
        return (rv);
}

#ifdef CRYPTING_MAIN

/* A little main() function for people who want a stand-alone program to
   encode/decode BitlCrypted files. */

int main( int argc, char *argv[] )
{
        char *hash, *action, line[256];
        char* (*func)( char *, const char * );
        
        if( argc < 2 )
        {
                fprintf( stderr, "Usage: %s <password>\n\n"
                                 "Reads from stdin, writes to stdout.\n"
                                 "Call as \"encode\" to encode, \"decode\" to decode.\n", argv[0] );
                return( 1 );
        }
        
        hash = hashpass( argv[1] );
        action = argv[0] + strlen( argv[0] ) - strlen( "encode" );
        
        if( strcmp( action, "encode" ) == 0 )
        {
                fwrite( hash, 32, 1, stdout );
                func = obfucrypt;
        }
        else if( strcmp( action, "decode" ) == 0 )
        {
                char hash2[32];
                
                fread( hash2, 32, 1, stdin );
                if( memcmp( hash, hash2, 32 ) != 0 )
                {
                        fprintf( stderr, "Passwords don't match. Can't decode.\n" );
                        return( 1 );
                }
                func = deobfucrypt;
        }
        else
        {
                return( main( 0, NULL ) );
        }
        
        while( fscanf( stdin, "%[^\n]255s", line ) > 0 )
        {
                char *out;
                
                /* Flush the newline */
                fgetc( stdin );
                
                out = func( line, argv[1] );
                printf( "%s\n", out );
                g_free( out );
        }
        
        return( 0 );
}

#endif