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#17205 - 05/01/04 05:31 AM A simple buffer overflow  
Joined: Apr 2004
Posts: 2
newblet Offline
Junior Member
newblet  Offline
Junior Member

Joined: Apr 2004
Posts: 2
USA
Hey,
I'm not sure if this should go in this forum or somewhere else, but here goes. I need some help writing a buffer overflow for a setuid binary. It basically allocates 256 bytes for a buffer and calls scanf(%s,buffer). I know that this function is exploitable, but I can't figure out how to send my shellcode+ret into the program.
Someone want to help me out? How do I get the program to read my overflow code?

Thanks

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#17206 - 05/04/04 07:25 AM Re: A simple buffer overflow  
Joined: Jun 2002
Posts: 62
UndeadBob Offline
Junior Member
UndeadBob  Offline
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Joined: Jun 2002
Posts: 62
UK
understand assembly and how the code works the cpu. then you shall have your answer...


"Mrs. Jones, I'm sorry to inform you, but we've run the tests, and it appears that you have XP. Now don't cry - it's bad, but it's not a death sentence. Modern science has advanced in recent years, and it's now possible to live a reasonably happy life with XP. And there's a survivor's group that you'll want to meet as well."
#17207 - 05/13/04 08:03 AM Re: A simple buffer overflow  
Joined: Apr 2004
Posts: 2
newblet Offline
Junior Member
newblet  Offline
Junior Member

Joined: Apr 2004
Posts: 2
USA
Ummm...sorry, but that wasn't very helpful; I already know how everything about the overflows works. I already have the program that creates an environment variable containing the string that will spawn my shell. I can use it to spawn a shell from a program that uses strcpy() and receives the string from a parameter. I just don't know how to make a program that uses stdin instead of parameters. I've already tried sending my string into a file and dumping the file in. I've also tried echoing the variable and using | to send it into the program. Could the return address be different because of the scanf()?

Edit: spelling

#17208 - 05/18/04 09:17 PM Re: A simple buffer overflow  
Joined: Mar 2002
Posts: 815
sinetific Offline
nobody
sinetific  Offline
nobody

Joined: Mar 2002
Posts: 815
Ann Arbor
You can use a debugger to find the return address


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