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Difference between revisions of "Testing for LDAP Injection (OTG-INPVAL-006)"
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| − | + | {{Template:OWASP Testing Guide v4}} | |
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| − | {{Template:OWASP Testing Guide | ||
| − | == | + | == Summary == |
| − | + | The Lightweight Directory Access Protocol (LDAP) is used to store information about users, hosts, and many other objects. [[LDAP injection]] is a server side attack, which could allow sensitive information about users and hosts represented in an LDAP structure to be disclosed, modified, or inserted. This is done by manipulating input parameters afterwards passed to internal search, add, and modify functions. | |
| − | [[LDAP injection]] is a server side attack, which could allow sensitive information about users and hosts represented in an LDAP structure to be disclosed, modified, or inserted. | ||
| − | This is done by manipulating input parameters afterwards passed to internal search, add, and modify functions. | ||
| − | |||
A web application could use LDAP in order to let users authenticate or search other users' information | A web application could use LDAP in order to let users authenticate or search other users' information | ||
| − | inside a corporate structure. | + | inside a corporate structure. The goal of LDAP injection attacks is to inject LDAP search filters metacharacters in a query which will be executed by the application. |
| − | |||
| − | The goal of LDAP injection attacks is to inject LDAP search filters metacharacters in a query which will be executed by the application. | ||
[[http://www.ietf.org/rfc/rfc2254.txt Rfc2254]] | [[http://www.ietf.org/rfc/rfc2254.txt Rfc2254]] | ||
| Line 56: | Line 12: | ||
extends [[http://www.ietf.org/rfc/rfc1960.txt Rfc1960]] (LDAPv2). | extends [[http://www.ietf.org/rfc/rfc1960.txt Rfc1960]] (LDAPv2). | ||
| − | An LDAP search filter is constructed in | + | |
| + | An LDAP search filter is constructed in Polish notation, | ||
also known as [[http://en.wikipedia.org/wiki/Polish_notation prefix notation]]. | also known as [[http://en.wikipedia.org/wiki/Polish_notation prefix notation]]. | ||
| + | |||
This means that a pseudo code condition on a search filter like this: | This means that a pseudo code condition on a search filter like this: | ||
| Line 66: | Line 24: | ||
find("(&(cn=John)(userPassword=mypass))") | find("(&(cn=John)(userPassword=mypass))") | ||
| + | |||
Boolean conditions and group aggregations on an | Boolean conditions and group aggregations on an | ||
| Line 92: | Line 51: | ||
|- | |- | ||
|} | |} | ||
| + | |||
| + | |||
More complete examples on how to build a search filter can be | More complete examples on how to build a search filter can be | ||
found in the related RFC. | found in the related RFC. | ||
| + | |||
A successful exploitation of an LDAP injection vulnerability could allow the tester to: | A successful exploitation of an LDAP injection vulnerability could allow the tester to: | ||
| Line 102: | Line 64: | ||
* Add or modify Objects inside LDAP tree structure. | * Add or modify Objects inside LDAP tree structure. | ||
| − | |||
| + | == How to Test == | ||
| − | === Example 1 | + | |
| + | === Example 1: Search Filters === | ||
Let's suppose we have a web application using a search | Let's suppose we have a web application using a search | ||
| Line 126: | Line 89: | ||
which matches every object with a 'cn' attribute equals to anything. | which matches every object with a 'cn' attribute equals to anything. | ||
| + | |||
If the application is vulnerable to LDAP injection, it will display some or all of the users' attributes, depending on the application's execution flow and the permissions of the LDAP connected user. | If the application is vulnerable to LDAP injection, it will display some or all of the users' attributes, depending on the application's execution flow and the permissions of the LDAP connected user. | ||
| + | |||
A tester could use a trial-and-error approach, by inserting in the parameter | A tester could use a trial-and-error approach, by inserting in the parameter | ||
| Line 133: | Line 98: | ||
the application for errors. | the application for errors. | ||
| − | === Example 2 | + | |
| + | === Example 2: Login === | ||
If a web application uses LDAP to check user credentials during the login process and it is vulnerable to LDAP injection, it is possible to bypass the authentication check by injecting an always true LDAP query (in a similar way to SQL | If a web application uses LDAP to check user credentials during the login process and it is vulnerable to LDAP injection, it is possible to bypass the authentication check by injecting an always true LDAP query (in a similar way to SQL | ||
and XPATH injection ). | and XPATH injection ). | ||
| + | |||
Let's suppose a web application uses a filter to match LDAP user/password pair. | Let's suppose a web application uses a filter to match LDAP user/password pair. | ||
searchlogin= "(&(uid="+user+")(userPassword={MD5}"+base64(pack("H*",md5(pass)))+"))"; | searchlogin= "(&(uid="+user+")(userPassword={MD5}"+base64(pack("H*",md5(pass)))+"))"; | ||
| + | |||
By using the following values: | By using the following values: | ||
| Line 151: | Line 119: | ||
searchlogin="(&(uid=*)(uid=*))(|(uid=*)(userPassword={MD5}X03MO1qnZdYdgyfeuILPmQ==))"; | searchlogin="(&(uid=*)(uid=*))(|(uid=*)(userPassword={MD5}X03MO1qnZdYdgyfeuILPmQ==))"; | ||
| − | which is correct and always true. | + | which is correct and always true. This way, the tester will gain logged-in status as the first user in LDAP tree. |
| − | This way, the tester will gain logged-in status as the first user in LDAP tree. | + | |
| + | |||
| + | ==Tools== | ||
| + | Softerra LDAP Browser - http://www.ldapadministrator.com/ | ||
== References == | == References == | ||
| + | '''OWASP References'''<br> | ||
| + | [[LDAP Injection Prevention Cheat Sheet]] | ||
| + | |||
'''Whitepapers'''<br> | '''Whitepapers'''<br> | ||
| − | Sacha Faust: "LDAP Injection" - http://www. | + | Sacha Faust: "LDAP Injection: Are Your Applications Vulnerable?" - http://www.networkdls.com/articles/ldapinjection.pdf<br> |
Bruce Greenblatt: "LDAP Overview" - http://www.directory-applications.com/ldap3_files/frame.htm<br> | Bruce Greenblatt: "LDAP Overview" - http://www.directory-applications.com/ldap3_files/frame.htm<br> | ||
IBM paper: "Understanding LDAP" - http://www.redbooks.ibm.com/redbooks/SG244986.html <br> | IBM paper: "Understanding LDAP" - http://www.redbooks.ibm.com/redbooks/SG244986.html <br> | ||
| − | + | RFC 1960: "A String Representation of LDAP Search Filters" - http://www.ietf.org/rfc/rfc1960.txt<br> | |
| − | + | "LDAP injection" - http://www.blackhat.com/presentations/bh-europe-08/Alonso-Parada/Whitepaper/bh-eu-08-alonso-parada-WP.pdf<br> | |
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Latest revision as of 03:31, 8 February 2017
This article is part of the new OWASP Testing Guide v4.
Back to the OWASP Testing Guide v4 ToC: https://www.owasp.org/index.php/OWASP_Testing_Guide_v4_Table_of_Contents Back to the OWASP Testing Guide Project: https://www.owasp.org/index.php/OWASP_Testing_Project
Summary
The Lightweight Directory Access Protocol (LDAP) is used to store information about users, hosts, and many other objects. LDAP injection is a server side attack, which could allow sensitive information about users and hosts represented in an LDAP structure to be disclosed, modified, or inserted. This is done by manipulating input parameters afterwards passed to internal search, add, and modify functions.
A web application could use LDAP in order to let users authenticate or search other users' information
inside a corporate structure. The goal of LDAP injection attacks is to inject LDAP search filters metacharacters in a query which will be executed by the application.
[Rfc2254] defines a grammar on how to build a search filter on LDAPv3 and extends [Rfc1960] (LDAPv2).
An LDAP search filter is constructed in Polish notation,
also known as [prefix notation].
This means that a pseudo code condition on a search filter like this:
find("cn=John & userPassword=mypass")
will be represented as:
find("(&(cn=John)(userPassword=mypass))")
Boolean conditions and group aggregations on an
LDAP search filter could be applied by using
the following metacharacters:
| Metachar | Meaning |
| & | Boolean AND |
| | | Boolean OR |
| ! | Boolean NOT |
| = | Equals |
| ~= | Approx |
| >= | Greater than |
| <= | Less than |
| * | Any character |
| () | Grouping parenthesis |
More complete examples on how to build a search filter can be
found in the related RFC.
A successful exploitation of an LDAP injection vulnerability could allow the tester to:
- Access unauthorized content
- Evade application restrictions
- Gather unauthorized informations
- Add or modify Objects inside LDAP tree structure.
How to Test
Example 1: Search Filters
Let's suppose we have a web application using a search filter like the following one:
searchfilter="(cn="+user+")"
which is instantiated by an HTTP request like this:
http://www.example.com/ldapsearch?user=John
If the value 'John' is replaced with a '*', by sending the request:
http://www.example.com/ldapsearch?user=*
the filter will look like:
searchfilter="(cn=*)"
which matches every object with a 'cn' attribute equals to anything.
If the application is vulnerable to LDAP injection, it will display some or all of the users' attributes, depending on the application's execution flow and the permissions of the LDAP connected user.
A tester could use a trial-and-error approach, by inserting in the parameter
'(', '|', '&', '*' and the other characters, in order to check
the application for errors.
Example 2: Login
If a web application uses LDAP to check user credentials during the login process and it is vulnerable to LDAP injection, it is possible to bypass the authentication check by injecting an always true LDAP query (in a similar way to SQL and XPATH injection ).
Let's suppose a web application uses a filter to match LDAP user/password pair.
searchlogin= "(&(uid="+user+")(userPassword={MD5}"+base64(pack("H*",md5(pass)))+"))";
By using the following values:
user=*)(uid=*))(|(uid=* pass=password
the search filter will results in:
searchlogin="(&(uid=*)(uid=*))(|(uid=*)(userPassword={MD5}X03MO1qnZdYdgyfeuILPmQ==))";
which is correct and always true. This way, the tester will gain logged-in status as the first user in LDAP tree.
Tools
Softerra LDAP Browser - http://www.ldapadministrator.com/
References
OWASP References
LDAP Injection Prevention Cheat Sheet
Whitepapers
Sacha Faust: "LDAP Injection: Are Your Applications Vulnerable?" - http://www.networkdls.com/articles/ldapinjection.pdf
Bruce Greenblatt: "LDAP Overview" - http://www.directory-applications.com/ldap3_files/frame.htm
IBM paper: "Understanding LDAP" - http://www.redbooks.ibm.com/redbooks/SG244986.html
RFC 1960: "A String Representation of LDAP Search Filters" - http://www.ietf.org/rfc/rfc1960.txt
"LDAP injection" - http://www.blackhat.com/presentations/bh-europe-08/Alonso-Parada/Whitepaper/bh-eu-08-alonso-parada-WP.pdf
