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Security manager checks may get bypassed depending on the immediate caller's class loader.
For instance, in the presence of a security manager, the getSystemClassLoader and getParent methods succeed only if the caller's class loader is the delegation ancestor of the current class loader or if the caller's class loader is the same as the current one or if the code in the current execution context has the RunTimePermission, namely "getClassLoader".
Noncompliant Code Example
The createInstance method is the immediate caller of java.lang.Class.newInstance in this noncompliant example. The newInstance method is being invoked on the dateClass Class object. The issue is that the untrustedCode method can trigger the instantiation of a new class even though it should not have the permission to do so. This behavior is not caught by the security manager.
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A related issue is described in SEC03-J. Do not allow tainted parameters while using APIs that perform access checks against the immediate caller.
Compliant Solution
Do not accept Class, ClassLoader or Thread instances from untrusted code. If inevitable, safely acquire these instances by ensuring they come from trusted sources. Additionally, make sure to discard tainted inputs from untrusted code. Likewise, objects returned by the affected methods should not be propagated back to the untrusted code.
Note that the Class.newInstance()} method requires the class to contain a no-argument constructor. If this requirement is not satisfied, a runtime exception results, which indirectly prevents a security breach.
Risk Assessment
Bypassing Securitymanager checks may seriously compromise the security of a Java application.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
SEC33 SEC02-J | high | probable | medium | P12 | L1 |
Automated Detection
TODO
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
References
| Wiki Markup |
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\[[Gong 03|AA. Java References#Gong 03]\] Section 4.3.2, Class Loader Delegation Hierarchy \[[SCG 07|AA. Java References#SCG 07]\] Guideline 6-2 Safely invoke standard APIs that bypass SecurityManager checks depending on the immediate caller's class loader |
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