FCrackZip 1.0 Buffer Overflow

`# Exploit Title: FCrackZip Local Buffer Overflow PoC  
# Date: September 5th, 2010  
# Author: 0x6264  
# Software Link: http://oldhome.schmorp.de/marc/data/fcrackzip-1.0.tar.gz  
# Version: 1.0  
# Tested on: Ubuntu 10.04  
# CVE : None  
  
Software Description:  
fcrackzip is a zip password cracker, similar to fzc, zipcrack and others.  
  
Vulnerability:  
FCrackZip does not check the length of the input provided to it when using the '-p' flag to supply an initial password or file used for a dictionary attack. Passing it a string exceding its buffer size (40) results in an overwrite.  
  
Vulnerable Code:  
----------------------------  
case 'p':  
strcpy (pw, optarg);  
break;  
----------------------------  
  
Proof of Concept:  
  
$ ./fcrackzip -p $(python -c 'print "A"*44') file.zip  
  
Due to being compiled using canaries the overflow is detected and the process is terminated before the overwrite can take place.  
  
Solution:  
Replace the function 'strcpy (pw, optarg);' with 'strncpy (pw, optarg, 40);' Unlike strcpy(), strncpy() will copy no more than the specified string size(40 in our case).  
  
`