SEC34-J. Do not allow tainted variables in doPrivileged blocks

It is important to disallow operations on tainted input in a doPrivileged() block. This is because an adversary may supply malicious input that may result in indirect privilege escalation attacks.

Noncompliant Code Example

This noncompliant code example accepts a tained filename argument. An adversary may supply the name of a sensitive password file, complete with the path and consequently force operations to be performed on the wrong file.

private void privilegedMethod(final String filename) throws FileNotFoundException {
  final FileInputStream f[]={null};
  try {
    FileInputStream fis = AccessController.doPrivileged(
      new PrivilegedExceptionAction() {
        public FileInputStream run() throws FileNotFoundException {
          f[0] = new FileInputStream(filename);            
        }
      }
    );
  } catch (PrivilegedActionException e) { /* forward to handler */ }
  // do something with the file and then close it
}

Compliant Solution

Explicitly hardcode the name of the file and confine the privileged variables to the same method. This ensures that no malicious file is loaded by exploiting the privileges of the corresponding code.

private void privilegedMethod(final String filename) throws FileNotFoundException {
  final FileInputStream f[]={null};
  try {
    FileInputStream fis = AccessController.doPrivileged(
      new PrivilegedExceptionAction() {
        public FileInputStream run() throws FileNotFoundException {
          f[0] = new FileInputStream("/usr/home/filename");            
        }
      }
    );
  } catch (PrivilegedActionException e) { /* forward to handler */ }
  // do something with the file and then close it
}

Risk Assessment

Allowing tainted inputs in privileged operations can lead to privilege escalation attacks.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

[[API 06]] method doPrivileged()
[[Gong 03]] Sections 6.4, AccessController and 9.5 Privileged Code
[[SCG 07]] Guideline 6-1 Safely invoke java.security.AccessController.doPrivileged
[[MITRE 09]] CWE ID 266 "Incorrect Privilege Assignment", CWE ID 272 "Least Privilege Violation"

SEC33-J. Do not expose standard APIs that use the immediate caller's class loader instance to untrusted code      01. Platform Security (SEC)      02. Declarations and Initialization (DCL)