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Logging is essential for gathering debugging information, for carrying out incident response or forensics activities and for maintaining incriminating , and collecting forensic evidence. Nevertheless, logging sensitive data raises many concerns, including the privacy of the stakeholders, limitations imposed by the law on the collection of personal information, and the potential for data exposure through by insiders. Sensitive information includes, but is not limited to, IP addresses, user names and passwords, email addresses, credit card numbers, and any personally identifiable information such as social security numbers. Many countries prohibit or restrict collection of personal data; others permit retention of personal data only when held in an anonymized form. Consequently, ensure that logs contain only non-sensitive data.For example, leaking unencrypted credit card numbers into a log file could be a violation of PCI DSS (Payment Card Industry Data Security Standard) regulations [PCI 2010]. Consequently, logs must not contain sensitive data, particularly when prohibited by law.

Unfortunately, violations of this rule are common. For example, prior to version Wiki MarkupViolations of this guideline are common. For example, prior to version 0.8.1, the LineControl Java client logged sensitive information , including the local user's password \[[CVE 2008|AA. Bibliography#CVE 08]\]password, as documented by CVE-2005-2990.

The java.util.logging class provides the a basic logging framework in for JDK v1versions 1.4 and above; the examples below use the logging framework. The higher. Other logging frameworks exist, but the basic principles apply regardless of the particular logging framework chosen.

A program may support multiple Programs typically support varying levels of sensitivityprotection. Some information, such as access times, can be safely logged. Some infomration information can be logged, but the log file must be restricted from everyone but particular administrators. Other information, such as credit card numbers, can be included in logs only be logged in encrypted form. Other information, Information such as passwords , should not be logged at all.

For these the following code samplesexamples, we will assume that the log in question lies outside the trust boundary of the information being sent to itrecorded. Also, normal log messages should include additional parameters such as date, time, source event, etc.. We omit them in these examples for the sake of and so forth. This information has been omitted from the following code examples for brevity.

Noncompliant Code Example

In this noncompliant code example, a server logs the IP address of the remote client in the event of a security exception. Such This data can be misused in various ways, such as building , for example, to build a profile of a user's browsing habits. Such logging may violate legal restrictions in many countries.

If When the log cannot be trusted to hold the IP addresscontain IP addresses, it should not hold contain any info information about a SecurityException, because it might leak an IP address. When an exception contains sensitive information, the custom MyExceptionReporter class should extract or cleanse it , before returning control to the next statement in the catch block . (See guideline see ERR00-J. Do not suppress or ignore checked exceptions).)

public void logRemoteIPAddress(String name) {
  Logger logger = Logger.getLogger("com.organization.Log");
  InetAddress machine = null;
  try {
    machine = InetAddress.getByName(name);
  } catch (UnknownHostException e) { 
    Exception e = MyExceptionReporter.handle(e);
  } catch (SecurityException e) {
    Exception e = MyExceptionReporter.handle(e);
    logger.severe(name + "," + machine.getHostAddress() + "," +
                  e.toString());
  }
} 

Compliant Solution

This compliant solution simply does not log the security exception.security exceptions except for the logging implicitly performed by MyExceptionReporter:

   // ...
  catch (SecurityException e) {
    Exception e = MyExceptionReporter.handle(e);
  }

Noncompliant Code Example

Some information that is logged should be elided from Log messages with sensitive information should not be printed to the console display for security reasons (a possible example might be of sensitive information is passenger age). The java.util.logging.Logger class supports different logging levels that can be used for classifying such information. These are : FINEST, FINER, FINE, CONFIG, INFO, WARNING, and SEVERE. All levels after and including INFO, log By default, the INFO, WARNING, and SEVERE levels print the message to the console in addition to an external source, which is accessible by end users and system administrators.

If we assume that the passenger age can appear in log files on the current system but not on the console display, this code example is noncompliant.

logger.info("Age: " + passengerAge);

...

Compliant Solution

This noncompliant code example logs at a level below INFO — FINEST, in this case — to prevent the passenger age from being displayed on the console. It also makes sure that such messages do not appear on the console. Thus the age is not actually loggedcompliant solution logs the passenger age at the FINEST level to prevent this information from displaying on the console. As noted previously, we are assuming the age may appear in system log files but not on the console.

// Make sure that all handlers only print log messages rated INFO or higher
Handler handlers[] = logger.getHandlers();
for (int i = 0; i < handlers.length; i++) {
  handlers[i].setLevel(Level.INFO);
}
// ...
logger.finest("Age: " + passengerAge);

Risk Assessment

Logging sensitive information can violate system security policies and can violate user privacy when the logging level is incorrect or when the log files are insecure.

Related Vulnerabilities

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

Bibliography

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Automated Detection

Related Guidelines

Android Implementation Details

DRD04-J. Do not log sensitive information is an Android-specific instance of this rule.

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Image Added Image Added Image Added|http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2990] \[[MITRE 2009|AA. Bibliography#MITRE 09]\] [CWE ID 532|http://cwe.mitre.org/data/definitions/532.html] "Information Leak Through Log Files", [CWE ID 533|http://cwe.mitre.org/data/definitions/533.html] "Information Leak Through Server Log Files", [CWE ID 359|http://cwe.mitre.org/data/definitions/359.html] "Privacy Violation", [CWE ID 542|http://cwe.mitre.org/data/definitions/542.html] "Information Leak Through Cleanup Log Files" \[[Sun 2006|AA. Bibliography#Sun 06]\]] [Java Logging Overview|http://java.sun.com/javase/6/docs/technotes/guides/logging/overview.html]FIO07-J. Do not create temporary files in shared directories      12. Input Output (FIO)      FIO10-J. Do not let external processes block on IO buffers