38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* This file provides an implementation of printf(3), that could be used
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* to do all sorts of nefarious things, while at the same time also
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* implementing printf(3) itself.
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*
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* Build this into a shared library to LD_PRELOAD to illustrate the point.
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*/
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#include <stdarg.h>
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#include <stdio.h>
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#include <string.h>
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int printf(const char *fmt, ...) {
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va_list args;
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fprintf(stdout, "Muahaha, I can do anything now!\n");
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fprintf(stdout, "Including... unlink(whatever)\n");
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fprintf(stdout, "And to have nobody notice, I'll also do what's expected.\n");
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va_start(args, fmt);
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vprintf(fmt, args);
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va_end(args);
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return strlen(fmt);
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}
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