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

Mitigation Strategies

Static Analysis

Compliance with this rule can be checked using structural static analysis checkers using the following algorithm:

1. Traverse the abstract syntax tree (AST) to identify function calls to the signal function signal(int, void (*f)(int)).
2. At each function call to signal(int, void (*f)(int)) get the second argument from the argument list. To make sure that this is not an overloaded function the function type signature is evaluated and/or the location of the declaration of the function is verified to be from the correct file (because this is not a link-time analysis it is not possible to test the library implementation). Any definition for signal() in the application is suspicious, because it should be in a library.
3. Perform a nested query to identify all referenced objects with static storage duration. Verify that none of these objects are referenced as an rvalue, and that for each object referenced as an lvalue, the underlying type is sig_atomic_t.
4. Report any violations detected.

References

\[[Dowd 06|AA. C References#Dowd 06]\] Chapter 13, Synchronization and State
\[[ISO/IEC 03|AA. C References#ISO/IEC 03]\] "Signals and Interrupts"
\[[Open Group 04|AA. C References#Open Group 04]\] [longjmp|http://www.opengroup.org/onlinepubs/000095399/functions/longjmp.html]
\[OpenBSD\] [{{signal()}} Man Page|http://www.openbsd.org/cgi-bin/man.cgi?query=signal]
\[Zalewski\] [http://lcamtuf.coredump.cx/signals.txt]