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Difference between revisions of "LDAP injection"

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m (small typo fix and rewording)
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==Description==
 
==Description==
−
LDAP (Lightweight Directory Access Protocol) Injection is an attack used to exploit web based applications that construct LDAP statements from user input. When an application fails to sufficiently sanatize user input, it may be possible for an attacker to alter the construction of an LDAP statement. Due to the nature of web based applications the process will be run with the same permissions as the web server itself. Thus this could result in the execution of the command. Such a scenario could result in granting permissions to query, modify or remove anything inside the LDAP tree.
+
 
 +
LDAP Injection is an attack used to exploit web based applications that construct LDAP statements based on user input. When an application fails to properly sanitize user input, it’s possible to modify LDAP statements using a local proxy. This could result in the execution of arbitrary command such as granting permissions to unauthorized queries, and content modification inside the LDAP tree.
 +
The same advanced exploitation techniques available in SQL Injection can be similarly applied in LDAP Injection.
 +
 
 +
 
 +
 
 +
==Examples ==
 +
 
 +
===Example 1===
 +
 
 +
 
 +
In a page with a user search form, the following code is responsible to catch input value and generate a LDAP query that will be used in LDAP database.
 +
 
 +
  <input type="text" size=20 name="userName">Insert the username</input>
 +
 
 +
 
 +
The  LDAP query is narrowed down for performance and the underlying code for this function might be the following:
 +
  String ldapSearchQuery = "(cn=" + $userName + ")";
 +
  System.out.println(ldapSearchQuery);
 +
 
 +
 
 +
Case the variable $userName is not validated, it could be possible accomplish LDAP injection, as follows:
 +
*If a user puts “*” on box search, the system may return all the usernames on the LDAP base
 +
*If a user puts “jonys) (| (password = * ) )”, it will generate the code bellow revealing jonys’ password
 +
( cn = jonys ) ( | (password = * ) )
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 +
 
 +
===Example 2===
 +
 
 +
The following vulnerable code is used in an ASP web application which provides login with LDAP data base.  
 +
On line 11, the variable userName is initialized and validated to check if it’s not in blank. Then, the content of this variable is used to construct a LDAP query used by SearchFilter on line 28. The attacker has the chance specify what will be queried on LDAP server, and see the result on the line 33 to 41, are all results and their attributes are displayed.
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 +
 
 +
Commented vulnerable asp code:
 +
<nowiki>
 +
1. <html>
 +
2. <body>
 +
3. <%@ Language=VBScript %>
 +
4. <%
 +
5. Dim userName
 +
6. Dim filter
 +
7. Dim ldapObj
 +
8.
 +
9. Const LDAP_SERVER = "ldap.example"
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10.
 +
11. userName = Request.QueryString("user")
 +
12.
 +
13. if( userName = "" ) then
 +
14. Response.Write("Invalid request. Please specify a valid
 +
15. user name")
 +
16. Response.End()
 +
17. end if
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18.
 +
19. filter = "(uid=" + CStr(userName) + ")" ' searching for the  user entry
 +
20.
 +
21. 'Creating the LDAP object and setting the base dn
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22. Set ldapObj = Server.CreateObject("IPWorksASP.LDAP")
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23. ldapObj.ServerName = LDAP_SERVER
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24. ldapObj.DN = "ou=people,dc=spilab,dc=com"
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25.
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26. 'Setting the search filter
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27. ldapObj.SearchFilter = filter
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28.
 +
29. ldapObj.Search
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30.
 +
31. 'Showing the user information
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32. While ldapObj.NextResult = 1
 +
33. Response.Write("<p>")
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34.
 +
35. Response.Write("<b><u>User information for: " +
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36. ldapObj.AttrValue(0) + "</u></b><br>")
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37. For i = 0 To ldapObj.AttrCount -1
 +
38. Response.Write("<b>" + ldapObj.AttrType(i) +"</b>: " +
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39. ldapObj.AttrValue(i) + "<br>" )
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40. Next
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41. Response.Write("</p>")
 +
42. Wend
 +
43. %>
 +
44. </body>
 +
45. </html>  </nowiki>
 +
 +
 
 +
 
 +
In the example above, we send the * character in the user parameter which will result in the filter variable in the code to be initialized with (uid=*). The resulting LDAP statement will make the server return any object that contains a uid attribute like username.
 +
 
 +
 
 +
<nowiki> http://www.some-site.org/index.asp?user=*  </nowiki>
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 +
 
  
 
==References==
 
==References==
−
*[http://www.ietf.org/rfc/rfc1960.txt A String Representation of LDAP Search Filters (RFC1960)]
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−
*[http://www.redbooks.ibm.com/redbooks/SG244986.html IBM RedBooks - Understanding LDAP]
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*http://www.ietf.org/rfc/rfc1960.txt A String Representation of LDAP Search Filters (RFC1960)
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*http://www.redbooks.ibm.com/redbooks/SG244986.html IBM RedBooks - Understanding LDAP
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*http://www.webappsec.org/projects/threat/classes/ldap_injection.shtml
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 +
 
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==Related Threats==
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{{Template:Stub}}
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[[:Category:Information Disclosure]]
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==Related Attacks==
 
==Related Attacks==
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*[[SQL Injection]]
 
*[[SQL Injection]]
 
*[[Command Injection]]
 
*[[Command Injection]]
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*[[Relative Path Traversal]]
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*[[Resource Injection]]
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*[[Path Manipulation]]
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 +
  
 
==Related Vulnerabilities==
 
==Related Vulnerabilities==
−
[[:Category:Lack of Input Validation]]
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 +
[[:Category:Input Validation Vulnerability]]
 +
 
 +
 
  
 
==Related Countermeasures==
 
==Related Countermeasures==
 +
 
[[:Category:Input Validation]]
 
[[:Category:Input Validation]]
 +
 +
 +
;Some other ways of to prevent of this attack:
 +
 +
: Validating for the type:
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  int  trustedUserName = Convert.ToInt32( Request.Querysrting(“username”)
 +
 +
: Pattern validating
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  string email = Regex.IsMatch( Request.Querystring( “email” ) ,”  ^.+@[^\.].*\.[a-z]{2,}$ ” ).
 +
 +
:Domain values validation:
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  string trustedCountry = Request.Querystring(“country”) in {“BR”,“VE”,“CL”,“CO”,“UY”,“PE”,“PY”}
 +
 +
  
 
==Categories==
 
==Categories==
 
[[Category:Injection Attack]]
 
[[Category:Injection Attack]]

Revision as of 13:35, 27 July 2007

This is an Attack. To view all attacks, please see the Attack Category page.


Description

LDAP Injection is an attack used to exploit web based applications that construct LDAP statements based on user input. When an application fails to properly sanitize user input, it’s possible to modify LDAP statements using a local proxy. This could result in the execution of arbitrary command such as granting permissions to unauthorized queries, and content modification inside the LDAP tree. The same advanced exploitation techniques available in SQL Injection can be similarly applied in LDAP Injection.


Examples

Example 1

In a page with a user search form, the following code is responsible to catch input value and generate a LDAP query that will be used in LDAP database. 

 <input type="text" size=20 name="userName">Insert the username</input>


The LDAP query is narrowed down for performance and the underlying code for this function might be the following: 

 String ldapSearchQuery = "(cn=" + $userName + ")";
 System.out.println(ldapSearchQuery);


Case the variable $userName is not validated, it could be possible accomplish LDAP injection, as follows: 

*If a user puts “*” on box search, the system may return all the usernames on the LDAP base
*If a user puts “jonys) (| (password = * ) )”, it will generate the code bellow revealing jonys’ password
( cn = jonys ) ( | (password = * ) )


Example 2

The following vulnerable code is used in an ASP web application which provides login with LDAP data base. On line 11, the variable userName is initialized and validated to check if it’s not in blank. Then, the content of this variable is used to construct a LDAP query used by SearchFilter on line 28. The attacker has the chance specify what will be queried on LDAP server, and see the result on the line 33 to 41, are all results and their attributes are displayed.


Commented vulnerable asp code: 

 
 1.	<html>
 2.	<body>
 3.	<%@ Language=VBScript %>
 4.	<%
 5.	Dim userName
 6.	Dim filter
 7.	Dim ldapObj
 8.		
 9.	Const LDAP_SERVER = "ldap.example"
 10.	
 11.	userName = Request.QueryString("user")
 12.	
 13.	if( userName = "" ) then
 14.	Response.Write("Invalid request. Please specify a valid
 15.	user name")
 16.	Response.End()
 17.	end if
 18.	
 19.	filter = "(uid=" + CStr(userName) + ")" ' searching for the  user entry 
 20.	
 21.	'Creating the LDAP object and setting the base dn
 22.	Set ldapObj = Server.CreateObject("IPWorksASP.LDAP")
 23.	ldapObj.ServerName = LDAP_SERVER
 24.	ldapObj.DN = "ou=people,dc=spilab,dc=com"
 25.	
 26.	'Setting the search filter
 27.	ldapObj.SearchFilter = filter
 28.	
 29.	ldapObj.Search
 30.	
 31.	'Showing the user information
 32.	While ldapObj.NextResult = 1
 33.	Response.Write("<p>")
 34.	
 35.	Response.Write("<b><u>User information for: " + 
 36.	ldapObj.AttrValue(0) + "</u></b><br>")
 37.	For i = 0 To ldapObj.AttrCount -1
 38.	Response.Write("<b>" + ldapObj.AttrType(i) +"</b>: " +
 39.	ldapObj.AttrValue(i) + "<br>" )
 40.	Next
 41.	Response.Write("</p>")
 42.	Wend
 43.	%>
 44.	</body>
 45.	</html>


In the example above, we send the * character in the user parameter which will result in the filter variable in the code to be initialized with (uid=*). The resulting LDAP statement will make the server return any object that contains a uid attribute like username. 


 http://www.some-site.org/index.asp?user=*


References


Related Threats

This article is a stub. You can help OWASP by expanding it or discussing it on its Talk page.Category:Information Disclosure


Related Attacks


Related Vulnerabilities

Category:Input Validation Vulnerability


Related Countermeasures

Category:Input Validation


Some other ways of to prevent of this attack
Validating for the type:
 int  trustedUserName = Convert.ToInt32( Request.Querysrting(“username”)
Pattern validating
 string email = Regex.IsMatch( Request.Querystring( “email” ) ,”  ^.+@[^\.].*\.[a-z]{2,}$ ” ).
Domain values validation:
 string trustedCountry = Request.Querystring(“country”) in {“BR”,“VE”,“CL”,“CO”,“UY”,“PE”,“PY”}


Categories

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