Buffer Overflows

Cause of around 20-50% of all CERT security alerts

Simple example (DOS attack)

$ cat bufftest.c

main()
{
        char buff[20];

        gets(buff);
        puts(buff);
}

$ cc -o bufftest bufftest.c
/tmp/ccjCiHlw.o: In function `main':
/tmp/ccjCiHlw.o(.text+0xe): warning: this program uses gets(), which is unsafe.
$ ./bufftest
warning: this program uses gets(), which is unsafe.
normal text
normal text
$ ./bufftest
warning: this program uses gets(), which is unsafe.
text longer than the buffer size
text longer than the buffer size
Segmentation fault (core dumped)

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