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Lab 2 – Exploitation (Buffer Overflow)

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CECS 478 Lab 2 – Exploitation (Buffer Overflow)
60 points
Assignment Description. This assignment focuses on buffer overflow attacks and how they can
be carried out on poorly-programmed system programs. This assigment will be difficult–but not
impossible–to complete on a modern operating system, as there are canaries built-in to modern
shells (and kernels) to prevent such a thing from occurring. Review the article Smashing the Stack
for Fun and Profit for a very good, detailed introduction on how to perform a stack smashing
attack. Your textbook also has an excellent tutorial in Chapter 3 on how to perform a buffer
overflow exploit on a modern operating system.
Assignment. Given the following C code file, perform a stack smash on the vuln.c code file using
a C program that you create named exploit.c. For full credit, your program should attempt to open
up a reverse shell on the attacked program as root by exploiting the buffer (you can verify this by
typing the command ‘whoami‘ on the resulting terminal. Don’t start the exploit as root–use your
own user account to do this). The vuln.c code must be compiled in its own, separate program and
must not be altered from its original state. You might consider running your exploit using a Perl
wrapper to inject the appropriate assembly code. See here for an example of running Perl within
C.
1 //vuln.c
2 #include <stdio.h>
3 #include <string.h>
4 int main(int argc, char **argv) {
5 // Make some stack information
6 char a[100], b[100], c[100], d[100];
7 // Call the exploitable function
8 exploitable(argv[1]);
9 // Return: everything is okay
10 return(0); }
11
12 int exploitable(char *arg) {
13 // Make some stack space
14 char buffer[10];
15 // Now copy the buffer
16 strcpy(buffer, arg);
17 printf(“The buffer says .. [%s/%p].\n”, buffer, &buffer);
18 // Return: the fun stuff
19 return(0); }
Note: when running Linux, you will probably need to disable some address randomization.
1
Deliverables. Submit your exploit.c to Beachboard Dropbox (no compression!) along with a
writeup of how you attempted the stack smashing attack and screenshots of the output or result of
a successful attack. Make sure that all code is commented with your own explanations or it will
not be graded and you will receive zero points for the lab.
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