defcamp 2013 - http header analysis
Post on 10-May-2015
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Agenda
• Why are headers important to us?
Agenda
• Why are headers important to us?
• What Checks are in AppSec Scanners?
Agenda
• Why are headers important to us?
• What Checks are in AppSec Scanners?
• Review of Header Attributes
Agenda
• Why are headers important to us?
• What Checks are in AppSec Scanners?
• Review of Header Attributes
• Demo of gethead.py
Why are headers important to us?
Why are headers important to us?
It’s the least protected area...
Reference: Data compiled from InfoSec Institute 2012 study
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GET" POST" HTTP"Cookie" HTTP"Header"
Input&Parameter&Coverage&in&Web&Applica6on&Scanners&
No"Coverage"
Coverage"
Non$Coverage$Rate$of$Input$Vectors$
GET$
POST$
HTTP$Cookie$
HTTP$Header$
Opportunity
POST /.%252e/.%252e/.%252e/.%252e/.%252e/.%252e/.%252e/boot.ini&url=httphacker.com HTTP/1.0 Referer: domain.com/external.xml Accept: */* User-Agent: Mozilla/5.0 Gecko/20110614 Firefox/3.6.18 Host: domain.com Connection: Keep-Alive Cookie: oAuth[access_token]=%31%33%33%37%22%3e%3c%73%43%72%49%70%54%3e%61%6c%65%72%74%28%68 %74%74%70%68%61%63%6b%65%72%29%3c%2f%73%43%72%49%70%54%3e;PHPSESSID=k04mk749i6cur91k; !<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/passwd"> ]><REQUEST><FROM>null</FROM><METHOD>SEND</METHOD><MESSAGE type=”MSG”><HEAD><ID>612117752013</ID><FROM>null</FROM><DESTINATION>UserManagerService&xxe;</DESTINATION><ACTION>logout</ACTION><EVENT>null</EVENT></HEAD><BODY /></MESSAGE></REQUEST> !username:http&password=hacker
What Checks are in AppSec Scanners?
What Checks are in AppSec Scanners?
What is missing in AppSec Scanners?
Let’s review some of these headers...
Content Security Policy (CSP)
Content Security Policy (CSP)
• Lets you specify a policy for where content in your webpages can be loaded from
Content Security Policy (CSP)
• Lets you specify a policy for where content in your webpages can be loaded from
• Lets you put restrictions on script execution
Content Security Policy (CSP)
• Lets you specify a policy for where content in your webpages can be loaded from
• Lets you put restrictions on script execution
• Headers
• Content-Security-Policy - Chrome 25 (Firefox nightlies)
• X-Content-Security-Policy - Firefox 4+
• X-WebKit-CSP - WebKit browsers (Chrome/Safari)
CSP Directives
• default-src - Specifies the default for other sources
• script-src
• style-src
• object-src - plugins
• img-src
• media-src - video/audio
• frame-src
• font-src
• connect-src
• report-uri - Specifies where CSP violations can be reported
CSP Sources (for the directives)
• ‘none’ - No content of this type is allowed (All directives)
CSP Sources (for the directives)
• ‘none’ - No content of this type is allowed (All directives)
• ‘self ’ - Content of this type can only be loaded from the same origin (no content from other sites) (All directives)
CSP Sources (for the directives)
• ‘none’ - No content of this type is allowed (All directives)
• ‘self ’ - Content of this type can only be loaded from the same origin (no content from other sites) (All directives)
• ‘unsafe-inline’ - Allows unsafe inline content
• Supported by style-src (inline css) and script-src (inline script)
CSP Sources (for the directives)
• ‘none’ - No content of this type is allowed (All directives)
• ‘self ’ - Content of this type can only be loaded from the same origin (no content from other sites) (All directives)
• ‘unsafe-inline’ - Allows unsafe inline content
• Supported by style-src (inline css) and script-src (inline script)
• ‘unsafe-eval’ - Allow script functions considered unsafe (such as eval())
• Supported by script-src
CSP Sources (for the directives)
• And you can specify custom sources:
• * - Allow content from anywhere
• https: - Scheme only, load only content served over https
• *.domain.com - Wildcard host, allow content from any domain.com sub-domain
• www.domain.com:81 - You can specify a port number
• https://www.domain.com - You can specify an absolute URI for a host (path has no effect though)
And then it all comes together
• Content-Security-Policy: default-src ‘self ’; script-src ‘self ’ scripts.domain.com
• This policy sets a default source of ‘self ’ for all directives
• script-src defines its own sources, replacing the default
• In effect, scripts, stylesheets, images, flash animations, Java applets, etc., can only be loaded from the same origin as the page
• Scripts can also be loaded from scripts.domain.com
• This policy denies inline scripts and CSS!
The “special” sources
• ‘unsafe-inline’ can allow inline scripts (script-src) and styles (style-src)
• ‘unsafe-eval’ allows certain JavaScript functions considered high risk (eval())
• Use these special sources with care
CSP Reporting
• You can specify a “report-uri” in the CSP header
CSP Reporting
• You can specify a “report-uri” in the CSP header
• Must be a relative URI
CSP Reporting
• You can specify a “report-uri” in the CSP header
• Must be a relative URI
• Will post violation reports as JSON back to the web application
CSP Reporting
• You can specify a “report-uri” in the CSP header
• Must be a relative URI
• Will post violation reports as JSON back to the web application
• Content-Security-Policy-Report-Only
• Will not block scripts or resources violating the policy
• Will report them to the web application
XSS Protection
XSS Protection
• X-XSS-Protection: 1; mode=block
• Enables XSS Filter built into most recent web browsers
• Role is to re-enable for a particular website if it was disabled by the user
XSS summarized
• Make sure you validate your inputs
• Make sure you encode everything you output
• Input to the web application
• Data from backend system
• EVERYTHING!
• Use CSP and XSS-Protection as an extra level of defense, it’s not the cure!
X-Frame-Options (Click-jacking)
Click-jacking
• A malicious site loads the vulnerable site in an iframe
Click-jacking
• A malicious site loads the vulnerable site in an iframe
• The iframe is invisible and positioned in front of something the user is likely to click on
Click-jacking
• A malicious site loads the vulnerable site in an iframe
• The iframe is invisible and positioned in front of something the user is likely to click on
• The user clicks on what appears to be an element on the malicious site
• The user really clicks in the iframe, triggering some operation on the vulnerable site
X-Frame-Options
• X-Frame-Options: Deny | SameOrigin
• Instructs the browser to not display the page in a frame
• When the page isn’t displayed, there’s nothing to click on!
• Browser support: Opera 10.5+, Chrome 4.1+, IE 8+, Firefox 3.6.9+, Safari 4+
• Remember: The request is still sent to - and processed by - the web server!
X-Frame-Options Client Message
HTTP Strict Transport Security (HTTPS stripping)
HTTPS stripping explained
• “Secure” websites use SSL/TLS to preserve the confidentiality and integrity of the communication with a browser
HTTPS stripping explained
• “Secure” websites use SSL/TLS to preserve the confidentiality and integrity of the communication with a browser
• For usability, “secure” websites are still accessible through insecure channels (HTTP on port 80)
• They’ll redirect the user to HTTPS
• User enters www.onlinebank.com - and is redirected to https://www.onlinebank.com
• The very first request is insecure, and open to attack!
HTTPS stripping explained
• SSL stripping is a MiTM attack
• Attacker keeps the victim on HTTP, but passes requests on over HTTPS to the target website
• Practical attack demoed at BlackHat in 2009 (sslstrip)
HTTPS stripping scenario
An attacker sitting in the middle of a HTTPS session
HTTPS stripping scenario
An attacker sitting in the middle of a HTTPS session An attacker performing a HTTPS stripping attack
HTTP Strict Transport Security
• Strict-Transport-Security: max-age=31536000; includeSubDomains
• Max-age specifies for how many seconds the policy should be in effect
• includeSubDomains - optional
• Instructs the browser to only communicate to that hostname over SSL/TLS
• Fails hard on certificate errors
• The user does not have the option to click through certificate warnings
• Browser support: Chrome 4+, Firefox 4+, Opera 12
Session hijacking Securing Cookies
Session hijacking explained
• Means getting access to a user’s privileged session > steal session tokens
Session hijacking explained
• Means getting access to a user’s privileged session > steal session tokens
• Session tokens mean cookies
Session hijacking explained
• Means getting access to a user’s privileged session > steal session tokens
• Session tokens mean cookies
• Protect the cookies!
Session hijacking explained
• Means getting access to a user’s privileged session > steal session tokens
• Session tokens mean cookies
• Protect the cookies!
• Cookies can be marked with the ‘httpOnly’ flag > makes them inaccessible to JS, they won’t be included in requests from applets
Session hijacking explained
• Means getting access to a user’s privileged session > steal session tokens
• Session tokens mean cookies
• Protect the cookies!
• Cookies can be marked with the ‘httpOnly’ flag > makes them inaccessible to JS, they won’t be included in requests from applets
• Cookies can be marked with the “secure” flag > instructs the browser to only send them with HTTPS requests
IE MIME sniffing (Content-Type Options)
IE MIME Sniffing
• HTTP responses include a header stating what type of content is included
IE MIME Sniffing
• HTTP responses include a header stating what type of content is included
• To compensate for misconfigured servers and bad programming, IE introduced MIME sniffing back in the days (IE4)
IE MIME Sniffing
• HTTP responses include a header stating what type of content is included
• To compensate for misconfigured servers and bad programming, IE introduced MIME sniffing back in the days (IE4)
• They introduced the “X-Content-Type-Options: nosniff” header in IE9 to disable the behavior
IE MIME Sniffing
• HTTP responses include a header stating what type of content is included
• To compensate for misconfigured servers and bad programming, IE introduced MIME sniffing back in the days (IE4)
• They introduced the “X-Content-Type-Options: nosniff” header in IE9 to disable the behavior
• Always serve your content with the correct content type, and the “X-Content-Type-Options” header
In Summary...we need more header detection and protection!
gethead Current Features
• Written in Python 2.7.5
• Performs HTTP Header Analysis
• Reports Header Vulnerabilities
• Open Source
gethead December Features
• Support for git updates
• Support for Python 3.x
• Complete Header Analysis
• Rank Vulnerabilities by Severity
• Export Findings with Description, Impact, Execution, Fix, and References
• Export with multi-format options (XML, HTML, TXT)
gethead February Features
• Replay & Inline Upstream Proxy Support to import into WebInspect
• Scan domains, sub-domains, and multi-services
• Header Injection & Fuzzing functionality
• HTTP Header Policy Bypassing
• Modularize and port to more platforms (e.g. gMinor, Kali, Burp Extension, Metasploit, Chrome)
Thank you.
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