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Difference between revisions of "Top 10 2013-A4-Insecure Direct Object References"

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The best way to find out if an application is vulnerable to insecure direct object references is to verify that all object references have appropriate defenses. To achieve this, consider:
 
The best way to find out if an application is vulnerable to insecure direct object references is to verify that all object references have appropriate defenses. To achieve this, consider:
 
# For direct references to restricted resources, the application needs to verify the user is authorized to access the exact resource they have requested.
 
# For direct references to restricted resources, the application needs to verify the user is authorized to access the exact resource they have requested.
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Code review of the application can quickly verify whether either approach is implemented safely. Testing is also effective for identifying direct object references and whether they are safe. Automated tools typically do not look for such flaws because they cannot recognize what requires protection or what is safe or unsafe.
 
Code review of the application can quickly verify whether either approach is implemented safely. Testing is also effective for identifying direct object references and whether they are safe. Automated tools typically do not look for such flaws because they cannot recognize what requires protection or what is safe or unsafe.
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Preventing insecure direct object references requires selecting an approach for protecting each user accessible object (e.g., object number, filename):
 
Preventing insecure direct object references requires selecting an approach for protecting each user accessible object (e.g., object number, filename):
  
 
# Use per user or session indirect object references. This prevents attackers from directly targeting unauthorized resources. For example, instead of using the resource’s database key, a drop down list of six resources authorized for the current user could use the numbers 1 to 6 to indicate which value the user selected. The application has to map the per-user indirect reference back to the actual database key on the server. OWASP’s [https://www.owasp.org/index.php/ESAPI  ESAPI] includes both sequential and random access reference maps that developers can use to eliminate direct object references.  
 
# Use per user or session indirect object references. This prevents attackers from directly targeting unauthorized resources. For example, instead of using the resource’s database key, a drop down list of six resources authorized for the current user could use the numbers 1 to 6 to indicate which value the user selected. The application has to map the per-user indirect reference back to the actual database key on the server. OWASP’s [https://www.owasp.org/index.php/ESAPI  ESAPI] includes both sequential and random access reference maps that developers can use to eliminate direct object references.  
 
# Check access. Each use of a direct object reference from an untrusted source must include an access control check to ensure the user is authorized for the requested object.
 
# Check access. Each use of a direct object reference from an untrusted source must include an access control check to ensure the user is authorized for the requested object.
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The application uses unverified data in a SQL call that is accessing account information:
 
The application uses unverified data in a SQL call that is accessing account information:
 
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http://example.com/app/accountInfo?acct=<span style="color:red;">notmyacct</span>
 
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* [https://www.owasp.org/index.php/Top_10_2007-Insecure_Direct_Object_Reference  OWASP Top 10-2007 on Insecure Dir Object References]
 
* [https://www.owasp.org/index.php/Top_10_2007-Insecure_Direct_Object_Reference  OWASP Top 10-2007 on Insecure Dir Object References]

Revision as of 22:47, 13 April 2013

NOTE: THIS IS NOT THE LATEST VERSION. Please visit the OWASP Top 10 project page to find the latest edition.

[[Top 10 {{{year}}}-Cross-Site Scripting (XSS)|← Cross-Site Scripting (XSS)]]
[[Top 10 {{{year}}}-Table of Contents | {{{year}}} Table of Contents]]

[[Top_10_{{{year}}}-Top 10|{{{year}}} Top 10 List]]

[[Top 10 {{{year}}}-Security Misconfiguration|Security Misconfiguration →]]
Threat Agents Attack Vectors Security Weakness Technical Impacts Business Impacts
Application Specific Exploitability
EASY		 Prevalence
COMMON		 Detectability
EASY		 Impact
MODERATE		 Application / Business Specific
Consider the types of users of your system. Do any users have only partial access to certain types of system data? . Attacker, who is an authorized system user, simply changes a parameter value that directly refers to a system object to another object the user isn’t authorized for. Is access granted? Applications frequently use the actual name or key of an object when generating web pages. Applications don’t always verify the user is authorized for the target object. This results in an insecure direct object reference flaw. Testers can easily manipulate parameter values to detect such flaws and code analysis quickly shows whether authorization is properly verified. Such flaws can compromise all the data that can be referenced by the parameter. Unless the name space is sparse, it’s easy for an attacker to access all available data of that type. Consider the business value of the exposed data.

Also consider the business impact of public exposure of the vulnerability.

Am I Vulnerable To 'Insecure Direct Object References'?

The best way to find out if an application is vulnerable to insecure direct object references is to verify that all object references have appropriate defenses. To achieve this, consider:

  1. For direct references to restricted resources, the application needs to verify the user is authorized to access the exact resource they have requested.
  2. If the reference is an indirect reference, the mapping to the direct reference must be limited to values authorized for the current user.

Code review of the application can quickly verify whether either approach is implemented safely. Testing is also effective for identifying direct object references and whether they are safe. Automated tools typically do not look for such flaws because they cannot recognize what requires protection or what is safe or unsafe.

How Do I Prevent 'Insecure Direct Object References'?

Preventing insecure direct object references requires selecting an approach for protecting each user accessible object (e.g., object number, filename):

  1. Use per user or session indirect object references. This prevents attackers from directly targeting unauthorized resources. For example, instead of using the resource’s database key, a drop down list of six resources authorized for the current user could use the numbers 1 to 6 to indicate which value the user selected. The application has to map the per-user indirect reference back to the actual database key on the server. OWASP’s ESAPI includes both sequential and random access reference maps that developers can use to eliminate direct object references.
  2. Check access. Each use of a direct object reference from an untrusted source must include an access control check to ensure the user is authorized for the requested object.
Example Attack Scenarios

The application uses unverified data in a SQL call that is accessing account information:

String query = "SELECT * FROM accts WHERE account = ?"; PreparedStatement pstmt = connection.prepareStatement(query , … ); {{red|pstmt.setString( 1, request.getParameter("acct"));}} ResultSet results = pstmt.executeQuery( );

The attacker simply modifies the ‘acct’ parameter in their browser to send whatever account number they want. If not verified, the attacker can access any user’s account, instead of only the intended customer’s account.

http://example.com/app/accountInfo?acct=<span style="color:red;">notmyacct</span>
References

OWASP

For additional access control requirements, see the ASVS requirements area for Access Control (V4).

External

[[Top 10 {{{year}}}-Cross-Site Scripting (XSS)|← Cross-Site Scripting (XSS)]]
[[Top 10 {{{year}}}-Table of Contents | {{{year}}} Table of Contents]]

[[Top_10_{{{year}}}-Top 10|{{{year}}} Top 10 List]]

[[Top 10 {{{year}}}-Security Misconfiguration|Security Misconfiguration →]]
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