Question

Couldn’t find the answer by serching (maybe bad keywords), so I am creating a new question.

How do you handle parameter checking for dllexported methods with string parameters. The general rule is never trust user, but in reality? For example:

int foo(const char *bar)
{
    if(!bar)
        return FAIL;

    ???
}

Say the user of the library calls our function like:

foo(reinterpret_cast<char*>(0x00000008));

That should cause an AV on first:

strlen(bar);

Is there a way to guard against this? Correct approach to handle the error?

I know IsBadReadPtr is out of the question, because this function is in a class of dangerous and never to be used. But is there even a way I should and could handle the problem? I can’t __declpec(dllexport) std::string, can I? Moreover, even if I would, the std::string has some sort of thread local storage or statics that cause access violations when used from different modules, as far as I know (caused by statics or different heaps?).

Is there a security risk in using these functions, stack overflow (R/E)IP overwrite, or is it just going to cause safe AV?

Answer 1

You can only babysit the client so far. If they pass garbage to your function, is it your problem?