Build Time Hacking

Build Time Hacking
Mohammed Tanveer
21- March-2015

About me
Security Engineer at Citrix R&D India Pvt. Ltd.
Gamer by the night and hacker by the day ;-)
Twitter: @threatpointer
Disclaimer: Thoughts and views expressed are of my own and does not resemble any of my
employers!

Hacking during building Software!
Imagine we had the power to understand the code before its complied
How about embedding a backdoor ?
How about stealing legitimate certificates of a well known vendor and
using them to sign malware?
Or even reading error logs which threw out a ton of useful internal
details about the application itself!

Today- What to expect!
Explore frequently found Build Infrastructure design & implementation
issues
Understand the threat landscape from the “build” point of view!
Gain better sight on assessing your existing Build infrastructure
Proposed ways on securing your build environment using existing tools
and hardening guidelines.

What is Build
From ToProcess
of conversion
Source code Artifacts
run at the end-user
workstation
6

Why do we need to build ?
7
Configuration
Build
RESULT OF
 defined set of components having specific versions
 components = functional units
 components and their versions are chosen to meet specific
objectives or tasks
Main objectives
Functionality Performance

• Conclusively:
 To incorporate additional functionality (feature)
 To reach defined level of performance (as an example of non-
functional requirement)
8
Why do we need to build ?

Build tasks by priority
•Compilation
•Deployment
• DB integration
• Unit testing
• Code coverage
• Static analysis
• Source code metrics
• Dynamic analysis
• Documentation generation
• …
9

Build types
• Classification by use:
• Private [Developers build]
• Integration [Centralized build]
• Release [delivery to the end-user]
10

Build Tools
GNU Auto tools
• make
• automake
• autoconf
• autoheader
• libtool
• gettext
• gcc
• pkg-config
Auto tools alternatives
• pymake
• CMake
• Cons
• SCons
• qmake
• makepp
• JAM
• waf
Continuous Integration
Tools
• AnthillPro
• Bamboo
• Apache Continuum
• BuildIT
• BuildBot
• Hudson
• Jenkins
• Team Foundation Server
• TeamCity
• Travis CI

What is Continuous Integration
Continuous Integration is a software development practice where members of a
team integrate their work frequently, usually each person integrates at least daily -
leading to multiple integrations per day. Each integration is verified by an
automated build (including test) to detect integration errors as quickly as possible.
--by Martin Fowler
Ref: http://martinfowler.com/articles/continuousIntegration.html

Continuous Integration Overview
Ref: http://www.javaworld.com/javaworld/jw-12-2008/images/CIOverview.jpg

Opportunities during Build Process
• External facing Assets
 GitHub/Subversion -SVN’s
 Build Engineer’s Tools – ex: Jenkins
• Internally facing Assets
 Source Code Repositories- Perforce, GIT
 CI Tools
 Monitoring Tools
 QA Testing Tools
 Code Signing Tools/keys

External facing –Opportunities
• Source code put up on Git/SVN is usually open to public, partially private or
completely private
• Where is the opportunity ?
1. Imagine a naïve developer contributes to an open source project with a
new feature, checks in code, project lead- reviews the
feature/functionality and merges it the master repository
2. Invested efforts perform code audits to find bugs, often using them as
ZeroDays
• This would imply to all projects that are completely open sourced or partially
private ones.

What about completely Private ones ?
• We all know we don’t have access to them directly, right ?
The Indirect Way: (PenTester’s Way)
• Check for all available build tools/assets that are being used by the
target vendor
Example: Jenkins

External facing –cont.
Build triggering and monitoring
Tool- Jenkins
Jenkins an award winning CI
tool and has the most active
community in its category
We even have plenty of dorks

Jenkins-
Jenkins has had a very rich history of being PenTester friendly
Links for reference:
https://www.pentestgeek.com/2014/06/13/hacking-jenkins-servers-with-no-password/
http://www.labofapenetrationtester.com/2014/06/hacking-jenkins-servers.html
http://xn--thibaud-dya.fr/jenkins_credentials.html
http://dariusfreamon.wordpress.com/2014/01/07/jenkins-accountpasswordreset-account-
name-enumeration/

Jenkins User Id’s
• Exposed Jenkins interface reveals
information about the developers
participating in the software
projects. It is possible to extract user
id’s of the registered accounts with
associated names. This is a
substantial point of gaining
information about the users of a
specific organization.

Software Builds Information and Source
Codes
• Information about the changes in
the software over a passage of time
reveals information about the
development flow of the
components. Jenkins application
does not ask for any explicit
permission from the administrators
to validate the user before
accessing the ongoing software
builds.

Server-side Information Disclosure in
Environment Variables:
• Access to environment variables provides plethora of information. Example
shows the significant information about the configuration for MySQL (JDBC)
database server. The attacker can easily glean username and password of the
database (SONAR_JDBC_USERNAME & SONAR_JDBC_PASSWORD) including the
internal IP address with port number on which JDBC service is running

Server-side Information Disclosure in
Environment Variables: -Count

Exposure of Application Secret Data
In this example, the curl command uses a secret key to connect to a specific domain for
fetching JSON data through GET request.
The underlined example shows how a secret key is extracted by accessing the console-
output.

CRON Job Execution
The example shown below presents the creation of database by a specific cron job in one of the
vulnerable Jenkins configuration. It reveals how the table of OAUTH tokens is created and index is
generated.
The example shows the creation of database by a specific CRON job in one of the vulnerable
Jenkins configuration. It reveals how the table of OAUTH tokens is created and index is generated.

Jenkins- Thick client issues
Jenkins comes with a
command line utility
which allows us to
remotely
manage builds on
different nodes
The client jar file can
be modified to execute
code on the remote
Jenkins server

CLI Architecture & Quick Demo!
Makes a http request on Port 8080
Looks for a CLI port in response headers
Returns the CLI port that has been configured to listen on
CLIENT SERVER
An http request is sent on the specific port
ELSE
Full Duplex http stream
CLIENT SERVER

Jenkins – Groovy Script
• Jenkins features a nice
Groovy script console which
allows to run arbitrary scripts
on the Jenkins server or on
slave nodes. This feature can
be accessed from the
"manage Jenkins" link,
typically at
your http://server/jenkins/scr
ipt

MetaSploit Love
• Use the Auxiliary mode to understand the Jenkins configurations
• Using Jenkins Script-Console Java Execution
• exploit/multi/http/jenkins_script_console

Jenkins- Plugins
• SonarQube
• SonarQube Plugin for Jenkins contains a flaw that is triggered when a direct
request is sent for /jenkins/configure, which will cause the plugin to display
password information via the 'sonar.sonarPassword ' parameter. This may
allow a remote authenticated attacker to gain access to password information
• Active Directory
• Jenkins contains an unspecified flaw in the Active Directory plugin that may
allow an attacker to gain unauthorized administrator access
• Open ID
• Jenkins Open ID Plugin contains an unspecified flaw in SSO mode that may
allow an attacker to gain unauthorized administrative access

Plugins
Hudson Tray Application
• This plugin provides the Hudson User
a tool that runs on their desktop, that
monitors the status of the Hudson
Server (multiple servers supported),
and provides a simple tray icon on the
Notification Panel/System Tray,
showing them the worst case color of
the Hudson Jobs they are monitoring
The same plugin allows you to upload
arbitrary python scripts to the server.

Lesson learnt!!
We make use of the so call features of tools that are either
misconfigured or mismanaged leading us to compromise the complete
Build environment.

Problems known- Solutions ?
Dual Jenkins -DMZ based deployment for public facing interfaces

Problems known- Solutions ?
• Take special care of all tools interacting with the build environment.
• Disable as many plugins as possible- reducing the overall attack
surface
• If a public facing Jenkins is strictly needed- Use the DMZ method
explained in the previous slide.
• Username used should not be same as corporate id’s, these are
anyways going to be public 
• Old school- Patch them regularly and check logs regularly

Speaking of Internally facing assets
• Source Code Repositories- Perforce, GIT
• CI Tools
• Monitoring Tools
• QA Testing Tools
• Code Signing Tools/Private keys
• Build Engineers Systems

Internally facing - Solutions –cont.
• Make sure all components interacting with the build environment is
patched regularly and checked for any misconfigurations
• Its best to have a separate domain to operate your Build environment
& create groups specifically for Build engineers only
• Should you have multiple teams/products, segregate them within the
protected environment using dedicated VLAN’s
• Define Firewall rules for only what is needed and block the rest.

Credits
• Ahmed Gomaa
• Nikhil SamratAshok Mittal
• James Luther

Build Time Hacking

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