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:
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 were to occur while writing the security exception, the
catch block would throw an
IOException and the critical security exception would be lost. Finally, an attacker may disguise the exception so that it occurs with several other innocuous exceptions.
Throwable.printStackTrace() to output a security exception also constitutes a violation of this rule.
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.
Typically, only one logger is required for the entire program.
Exceptions thrown during data logging can cause loss of data and can conceal security problems.
Debug Warning (Java)
|S106||Standard outputs should not be used directly to log anything|
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.