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Latest revision as of 22:27, 15 June 2013

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

← A3-Cross-Site Scripting (XSS)
2013 Inhaltsverzeichnis

2013 Die Top-10-Risiken

A5-Sicherheitsrelevante Fehlkonfiguration →
Bedrohungsquellen
Angriffsvektoren
Schwachstellen
Technische Auswirkung
Auswirkung auf das Unternehmen
Anwendungs-
spezifisch		 Ausnutzbarkeit
EINFACH		 Verbreitung
HÄUFIG		 Auffindbarkeit
EINFACH		 Auswirkung
MITTEL		 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. Code analysis quickly shows whether authorization is properly verified.

Such flaws can compromise all the data that can be referenced by the parameter. Unless object references are unpredictable, 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

Bin ich durch 'Unsichere direkte Objektreferenzen' verwundbar?

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, does the application fail to verify the user is authorized to access the exact resource they have requested?
  2. If the reference is an indirect reference, does the mapping to the direct reference fail to limit the values to those 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.

Wie kann ich 'Unsichere direkte Objektreferenzen' verhindern?

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.
Mögliche Angriffsszenarien

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 , … );

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=notmyacct

Referenzen

OWASP

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

Andere

← A3-Cross-Site Scripting (XSS)
2013 Inhaltsverzeichnis

2013 Die Top-10-Risiken

A5-Sicherheitsrelevante Fehlkonfiguration →
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