CWE-364: Signal Handler Race Condition | Glexia

Causes

• This code registers the same signal handler function with two different signals (CWE-831). If those signals are sent to the process, the handler creates a log message (specified in the first argument to the program) and exits. The handler function uses global state (globalVar and logMessage), and it can be called by both the SIGHUP and SIGTERM signals. An attack scenario might follow these lines:, ,At this point, the state of the heap is uncertain, because malloc is still modifying the metadata for the heap; the metadata might be in an inconsistent state. The SIGTERM-handler call to free() is assuming that the metadata is inconsistent, possibly causing it to write data to the wrong location while managing the heap. The result is memory corruption, which could lead to a crash or even code execution, depending on the circumstances under which the code is running.,Note that this is an adaptation of a classic example as originally presented by Michal Zalewski [REF-360]; the original example was shown to be exploitable for code execution.,Also note that the strdup(argv[1]) call contains a potential buffer over-read (CWE-126) if the program is called without any arguments, because argc would be 0, and argv[1] would point outside the bounds of the array.
• The following code registers a signal handler with multiple signals in order to log when a specific event occurs and to free associated memory before exiting. However, the following sequence of events may result in a double-free (CWE-415):, ,This is just one possible exploitation of the above code. As another example, the syslog call may use malloc calls which are not async-signal safe. This could cause corruption of the heap management structures. For more details, consult the example within "Delivering Signals for Fun and Profit" [REF-360].

Remediation

• Requirements: Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• Architecture and Design: Design signal handlers to only set flags, rather than perform complex functionality. These flags can then be checked and acted upon within the main program loop.
• Implementation: Only use reentrant functions within signal handlers. Also, use validation to ensure that state is consistent while performing asynchronous actions that affect the state of execution.

Detection

• Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Related CWEs

• CWE-123: Write-what-where Condition
• CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
• CWE-415: Double Free
• CWE-416: Use After Free
• CWE-368: Context Switching Race Condition
• CWE-432: Dangerous Signal Handler not Disabled During Sensitive Operations
• CWE-828: Signal Handler with Functionality that is not Asynchronous-Safe
• CWE-831: Signal Handler Function Associated with Multiple Signals

Related CVEs

Related CVE mappings appear after CVE records are cross-indexed.

ATT&CK Relevance

ATT&CK relevance is shown only when reviewed or responsibly inferred.