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- #Stack smashing detected how does it work install#
- #Stack smashing detected how does it work software#
#Stack smashing detected how does it work install#
I couldn’t run it at first, and found that I had to install some missing libraries: apt-get install libc6-i386Īnd then I started gdb and loaded the file: $ gdb bof I copied the bof file to my computer: compiled the bof.c file into an executable: wget pwnable.kr/bin/bof Instead of just futzing around with the number of bytes in the beginning of our input, let’s use gdb and figure out exactly how many we need. That didn’t work, but I got an interesting message about stack smashing. *** stack smashing detected ***: /home/bof/bof terminated So, if we can write 32 bytes worth of data, then we can write our “0xcafebabe” message.
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So if the local variable key is in memory after overflowme, we can keep writing to overflowme long enough to overwrite key with our special message (‘cafebabe’). Variables are put on the stack such that earlier-defined variables in the code are last in memory (the stack grows upwards). So, gets is the unsafe version of fgets because it doesn’t check the size of its input. It is the caller’s responsibility to ensure that the input line, if any, is sufficiently short to fit in the string. The gets() function is equivalent to fgets() with an infinite size and a stream of stdin, except that the newline character (if any) is not stored in the string. If we type man gets (lol), the description of gets is shown: So, somehow, we need to change the value of key. It has a char array (our buffer), it prints out “overflow me : “, calls gets and then compares key (which is currently 0xdeadbeef) to 0xcafebabe. The program runs a function called func that is given an argument of “0xdeadbeef”. If we look at the bof.c file provided in the hint, we see: #include Netcat’s website describes it as “a featured networking utility which reads and writes data across network connections, using the TCP/IP protocol.” bof The “running at” line starts with “nc”, which means netcat.
#Stack smashing detected how does it work software#
Nana told me that buffer overflow is one of the most common software vulnerability. Next up in the Pwnable.kr “Toddler’s Bottle” series is ‘bof’.