This repo is for learning various heap exploitation techniques. We came up with the idea during a hack meeting, and have implemented the following techniques:
| File | Technique | Applicable CTF Challenges |
|---|---|---|
| fastbin_dup.c | Tricking malloc into returning an already-allocated heap pointer by abusing the fastbin freelist. | |
| fastbin_dup_into_stack.c | Tricking malloc into returning a nearly-arbitrary pointer by abusing the fastbin freelist. | 9447-search-engine |
| unsafe_unlink.c | Exploiting free on a corrupted chunk to get arbitrary write. | HITCON CTF 2014-stkof |
| house_of_spirit.c | Frees a fake fastbin chunk to get malloc to return a nearly-arbitrary pointer. |
Have a good example?
Add it here!
Try to inline the whole technique in a single .c -- it's a lot easier to learn that way.
The malloc_playground.c file given is the source for a program that prompts the user for commands to allocate and free memory interactively.
Some good heap exploitation resources are:
- Malloc Des-Maleficarum (http://phrack.org/issues/66/10.html) - some malloc exploitation techniques
- Understanding the heap by breaking it (https://www.blackhat.com/presentations/bh-usa-07/Ferguson/Whitepaper/bh-usa-07-ferguson-WP.pdf) - explains heap implementation and a couple exploits
- Glibc Adventures: The Forgotten Chunk (http://www.contextis.com/documents/120/Glibc_Adventures-The_Forgotten_Chunks.pdf) - advanced heap exploitation
There are a couple of "hardening" measures embedded in glibc, like export MALLOC_CHECK_=1 (enables some checks), export MALLOC_PERTURB_=1 (data is overwritten), export MALLOC_MMAP_THRESHOLD_=1 (always use mmap()), ...
More info: mcheck(), mallopt().
There's also some tracing support as mtrace(), malloc_stats(), malloc_info(), memusage, and in other functions in this family.