Quantitative analysis of issues found by afl in mandoc

http://undeadly.org/cgi?action=article&sid=20150619071929

by jorgecastillo • 11 years ago

85 6 11 years ago

undeadly.org

baby• 11 years ago

abuse of assert() for input validation

Does anyone know what he's talking about?

mje__• 11 years ago

assert() is a macro that is usually disabled in production builds. Input validation is obviously most important in production, so assert() should never be used for validation.

KerrickStaley• 11 years ago

assert() is a macro that will print an error message and abort the program if its argument doesn't evaluate to true.

assert() is usually used in debug builds to verify internal invariants of the code: "if this is false, something has gone horribly, terribly wrong; we've gone crazy and we should abort to avoid further hurting ourselves or others". It shouldn't be used to verify that user input is well-formed, since this happens under normal circumstances.

RickHull• 11 years ago

Furthermore, assert is specifically intended to catch internal logic bugs which would still be present even after user input validation. i.e. logic bugs which are invariant upon user input

strommen• 11 years ago

The 7 most-severe bugs were specifically related to reading/writing the wrong place in memory. These are impossible bugs to have in managed-memory environments.

It is absolute madness to use C or C++ in a security-critical system.

xyzzy123• 11 years ago

Except for maybe the kernel, libc, the browser, drivers, widely used server software, emulator suites, the window system, the office suite you have to use, the runtime libraries for the high level languages you use, and so on. </s>

(Hmm, perhaps I'm making your point for you? ...)

One thing I have noticed though is that replacing manual with automatic memory management often doesn't help as much as one might think. The bugs just tend to shift to other areas (e.g. memory corruption -> command execution, XSS or XXE etc).

I think this is because with a more forgiving language, developers tend to naturally create more complex systems. Like how car drivers go faster when they feel safer in their car.

Quantitative analysis of issues found by afl in mandoc

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