Archive for March 2011

YOPS Webserver Stack Buffer Overflow   1 comment

  • Post Info:
    1. # Author: Flavio do Carmo Junior aka waKKu
      # URL: Author’s Webpage
      # Date: February 16, 2011
      # Category: Exploiting, Programming, Security, Vulnerability Analysis

    Welcome back, goodfella ;)

    This is another post in “Vulnerability Analysis” category, but at this time, this is one of our (DcLabs) 0-days.

    1. Introduction
    YOPS is a really simple webserver we’ve found an Arbitrary (Remote) Code Execution and released an advisory and exploit last year.

    2. Triggering the bug
    One of DcLabs members, ipax, using a fuzzer noticed that when sending a big buffer and using the “HEAD” HTTP Method the software crashed with a segfault signal.

    He then asked me to take a look and, some time later, here we are ;). Ok, first thing to do is download a copy of the software and (God bless open source) compile it with debugging symbols, then running our “trigger” again, we were able to identify the crash:

    # --- gdb output ---
    MANAGER: 1 jobs in ACCEPTOR->PARSER queue
    errorer #1 has job (status = 400) (.errors/400.html)
    Program received signal SIGSEGV, Segmentation fault.
    [Switching to Thread 1208023360 (LWP 14222)]
    logger_th (arg=Cannot access memory at address 0xa30300c
    ) at main.c:383
    383                     printf("logger #%d: '%s' LOGGED [%d]\n", id, job->hdr.request_line, job->status);
    # --- gdb output ---

    The flaw happened at function logger_th(), something overwrote its argument address, as seen in (logger_th (arg=Cannot access memory at address 0xa30300c)) gdb message.

    3. Hunting down a vulnerability
    Read the rest of this entry »


    Posted March 24, 2011 by waKKu in Exploiting, Security, Vulnerability Analysis