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Exception Name | Description of information leak or threat |
|---|---|
| Underlying file system structure, user name enumeration |
| Database structure, user name enumeration |
| Enumeration of open ports when untrusted client can choose server port |
| May provide information about thread-unsafe code |
| Insufficient server resources (may aid DoS) |
| Resource enumeration |
| Underlying file system structure |
| Owner enumeration |
| Denial of service (DoS) |
| Denial of service (DoS) |
Noncompliant Code Example (Leaks from Exception Message and Type)
This noncompliant code example accepts a file name as an input argument. An attacker can gain insights into the structure of the underlying file system by repeatedly passing different paths to fictitious files. When a file is not found, the FileInputStream constructor throws a FileNotFoundException.
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In this noncompliant example, the exception is not sanitized which enables the attacker to also learn the user's home directory and as a result, the user name.
Noncompliant Code Example (rethrowing sensitive exception)
This noncompliant code example logs the exception and re-throws it without performing adequate message sanitization.
| Code Block | ||
|---|---|---|
| ||
try {
FileInputStream fis = new FileInputStream(System.getenv("APPDATA") + args[0]);
} catch (FileNotFoundException e) {
// Log the exception
throw e;
}
|
Noncompliant Code Example (Wrapping and Rethrowing Sensitive Exception)
This noncompliant code example logs the exception and wraps it in an unchecked exception before re-throwing it.
| Code Block | ||
|---|---|---|
| ||
try {
FileInputStream fis = new FileInputStream(System.getenv("APPDATA") + args[0]);
} catch (FileNotFoundException e) {
// Log the exception
throw new RuntimeException("Unable to retrieve file", e);
}
|
Compliant Solution (Forward to Dedicated Handler or Reporter)
The exception must be caught while taking special care to sanitize the message before propagating it to the caller. In cases where the exception type itself can reveal too much information, consider throwing a different exception altogether (with a different message, or possibly a higher level exception, referred to as exception translation). The MyExceptionReporter class described in guideline EXC01-J. Use a class dedicated to reporting exceptions is a good choice, as this compliant solution exemplifies.
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While following this guideline, make sure that security exceptions such as java.security.AccessControlException and java.lang.SecurityException are not masked in the process. This can lead to far more pernicious effects such as missed security event log entries. (See guideline EXC03-J. Use a logging API to log critical security exceptions.) The MyExceptionReporter class prescribes a logging method to deal with this condition.
Risk Assessment
Exceptions may inadvertently reveal sensitive information unless care is taken to limit the information disclosure.
Guideline | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
EXC06-J | medium | probable | high | P4 | L3 |
Automated Detection
TODO
Related Vulnerabilities
Other Languages
This guideline appears in the C++ Secure Coding Standard as ERR12-CPP. Do not allow exceptions to transmit sensitive information.
Bibliography
| Wiki Markup |
|---|
\[[SCG 2007|AA. Bibliography#SCG 07]\] Guideline 3-4 Purge sensitive information from exceptions \[[Gong 2003|AA. Bibliography#Gong 03]\] 9.1 Security Exceptions \[[MITRE 2009|AA. Bibliography#MITRE 09]\] [CWE ID 209|http://cwe.mitre.org/data/definitions/209.html] "Error Message Information Leak", [CWE ID 600|http://cwe.mitre.org/data/definitions/600.html] "Failure to Catch All Exceptions (Missing Catch Block)", [CWE ID 497|http://cwe.mitre.org/data/definitions/497.html] "Information Leak of System Data" |
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