Exploit the possiblities

Shadowsocks-libev 3.1.0 Command Execution

Shadowsocks-libev 3.1.0 Command Execution
Posted Oct 14, 2017
Authored by Niklas Abel

Shadowsocks-libev version 3.1.0 suffers from a remote command execution vulnerability.

tags | exploit, remote
MD5 | 216d00d0c25d00e82c302e01f38cfc12

Shadowsocks-libev 3.1.0 Command Execution

Change Mirror Download

X41 D-Sec GmbH Security Advisory: X41-2017-010

Command Execution in Shadowsocks-libev
======================================

Overview
--------
Severity Rating: High
Confirmed Affected Versions: 3.1.0
Confirmed Patched Versions: N/A
Vendor: Shadowsocks
Vendor URL: https://github.com/shadowsocks/shadowsocks-libev
Vector: Local
Credit: X41 D-Sec GmbH, Niklas Abel
Status: Public
CVE: not yet assigned
Advisory-URL:
https://www.x41-dsec.de/lab/advisories/x41-2017-010-shadowsocks-libev/


Summary and Impact
------------------
Shadowsocks-libev offers local command execution per configuration file
or/and additionally, code execution per UDP request on 127.0.0.1.

The configuration file on the file system or the JSON configuration
received via UDP request is parsed and the arguments are passed to the
"add_server" function.
The function calls "construct_command_line(manager, server);" which
returns a string from the parsed configuration.
The string gets executed at line 486 "if (system(cmd) == -1) {", so if a
configuration parameter contains "||evil command&&" within the "method"
parameter, the evil command will get executed.

The ss-manager uses UDP port 8830 to get control commands on 127.0.0.1.
By default no authentication is required, although a password can be set
with the '-k' parameter.


Product Description
-------------------
Shadowsocks-libev is a lightweight secured SOCKS5 proxy for embedded
devices and low-end boxes. The ss-manager is meant to control
Shadowsocks servers for multiple users, it spawns new servers if needed.

It is a port of Shadowsocks created by @clowwindy, and maintained by
@madeye and @linusyang.


Proof of Concept
----------------
As passed configuration requests are getting executed, the following command
will create file "evil" in /tmp/ on the server:

nc -u 127.0.0.1 8839
add: {"server_port":8003, "password":"test", "method":"||touch
/tmp/evil||"}

The code is executed through shadowsocks-libev/src/manager.c.
If the configuration file on the file system is manipulated, the code
would get executed as soon as a Shadowsocks instance is started from
ss-manage, as long as the malicious part of the configuration has not
been overwritten.


Workarounds
-----------
There is no workaround available, do not use ss-manage until a patch is
released.


About X41 D-Sec GmbH
--------------------
X41 D-Sec is a provider of application security services. We focus on
application code reviews, design review and security testing. X41 D-Sec
GmbH was founded in 2015 by Markus Vervier. We support customers in
various industries such as finance, software development and public
institutions.

Timeline
--------
2017-09-28 Issues found
2017-10-05 Vendor contacted
2017-10-09 Vendor contacted, replied to use GitHub for a full disclosure
2017-10-11 Vendor contacted, asked if the vendor is sure to want a full
disclosure
2017-10-12 Vendor contacted, replied to create a public issue on GitHub
2017-10-13 Created public issue on GitHub
2017-10-13 Advisory release





Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

Want To Donate?


Bitcoin: 18PFeCVLwpmaBuQqd5xAYZ8bZdvbyEWMmU

File Archive:

February 2018

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Feb 1st
    15 Files
  • 2
    Feb 2nd
    15 Files
  • 3
    Feb 3rd
    15 Files
  • 4
    Feb 4th
    13 Files
  • 5
    Feb 5th
    16 Files
  • 6
    Feb 6th
    15 Files
  • 7
    Feb 7th
    15 Files
  • 8
    Feb 8th
    15 Files
  • 9
    Feb 9th
    18 Files
  • 10
    Feb 10th
    8 Files
  • 11
    Feb 11th
    8 Files
  • 12
    Feb 12th
    17 Files
  • 13
    Feb 13th
    15 Files
  • 14
    Feb 14th
    15 Files
  • 15
    Feb 15th
    17 Files
  • 16
    Feb 16th
    18 Files
  • 17
    Feb 17th
    37 Files
  • 18
    Feb 18th
    2 Files
  • 19
    Feb 19th
    16 Files
  • 20
    Feb 20th
    16 Files
  • 21
    Feb 21st
    15 Files
  • 22
    Feb 22nd
    16 Files
  • 23
    Feb 23rd
    31 Files
  • 24
    Feb 24th
    0 Files
  • 25
    Feb 25th
    0 Files
  • 26
    Feb 26th
    0 Files
  • 27
    Feb 27th
    0 Files
  • 28
    Feb 28th
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2018 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close