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Exceptions that are thrown while logging is in progress can prevent successful logging unless special care is taken. Failure to account for exceptions during the logging process can cause security vulnerabilities, such as allowing an attacker to conceal critical security exceptions by preventing them from being logged. Consequently, programs must ensure that data logging continues to operate correctly even when exceptions are thrown during the logging process.

Noncompliant Code Example

This noncompliant code example writes a critical security exception to the standard error stream. :

try {
  // ...
} catch (SecurityException se) {
  System.err.println(ese);
  // Recover from exception
}

Writing such exceptions to the standard error stream is inadequate for logging purposes. First, the standard error stream may be exhausted or closed, preventing recording of subsequent exceptions. Second, the trust level of the standard error stream may be insufficient for recording certain security-critical exceptions or errors without leaking sensitive information. If an I/O error occurs were to occur while writing the security exception, the catch block will would throw an IOException and the critical security exception will would be lost. Finally, an attacker may disguise the exception so that it occurs with several other innocuous exceptions.

Similarly, using Using Console.printf(), System.out.print*(), or eThrowable.printStackTrace() to output a security exception also constitutes a violation of this rule.

Compliant Solution

This compliant solution uses java.util.logging.Logger, the default logging API provided by JDK 1.4 and later. Use of other compliant logging mechanisms, such as log4j, is also permitted.

try {
  // ...
} catch(SecurityException se) {
  logger.log(Level.SEVERE, se);
  // Recover from exception
}

Typically, only one logger is required for the entire program.

Risk Assessment

Exceptions thrown during data logging can cause loss of data and can conceal security problems.

Automated Detection

Related Vulnerabilities

HARMONY-5981 describes a vulnerability in the HARMONY implementation of Java. In this implementation, the FileHandler class can receive log messages, but if one thread closes the associated file, a second thread will throw an exception when it tries to log a message.

Bibliography

\[[API 2006|AA. Bibliography#API 06]\] [Class Logger|http://java.sun.com/javase/6/docs/api/java/util/logging/Logger.html]
\[[JLS 2005|AA. Bibliography#JLS 05]\] [Chapter 11, Exceptions|http://java.sun.com/docs/books/jls/third_edition/html/exceptions.html]
\[[Ware 2008|AA. Bibliography#Ware 08]\]

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Image Added Image Added ERR06-J. Do not allow exceptions to expose sensitive information      06. Exceptional Behavior (ERR)      Image Modified