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Non-final classes containing methods that perform security checks can be compromised if a malicious subclass overrides the method and omits the checks. For this reason, it is recommended that the methods be prohibited from being extended by declaring them private or final.

Noncompliant Code Example

This noncompliant code example allows a subclass to override the readSensitiveFile() method and omit the required security check.

public void readSensitiveFile() {
  try {
    SecurityManager sm = System.getSecurityManager();
    if(sm != null) {  // Check if file can be read
      sm.checkRead("/temp/tempFile");
    } 
    // Access the file
  } catch (SecurityException se) { 
    // Log exception  
  }
}

Compliant Solution

This compliant solution prohibits inheritance of the readSensitiveFile() method by declaring it final.

public final void readSensitiveFile() {
  try {
    SecurityManager sm = System.getSecurityManager();
    if(sm != null) {  // check if file can be read
      sm.checkRead("/temp/tempFile");
    } 
    // Access the file
  } catch (SecurityException se) { 
    // Log exception 
  }
}

Compliant Solution

This compliant solution prohibits inheritance of the readSensitiveFile() method by declaring it private.

private void readSensitiveFile() {
  try {
    SecurityManager sm = System.getSecurityManager();
    if(sm != null) {  // check if file can be read
      sm.checkRead("/temp/tempFile");
    } 
    // Access the file
  } catch (SecurityException se) { 
    // Log exception 
  }
}

Exceptions

EX1: Classes that are declared final are exempt from this guideline as they imply that the contained methods cannot be overridden.

Risk Assessment

Failing to declare a non-final class's method private or final can allow a subclass to omit the security checks defined in the methods.

Automated Detection

TODO

Related Vulnerabilities

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

References

\[[Ware 08|AA. Java References#Ware 08]\]

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