This repo is for learning various heap exploitation techniques.
We use Ubuntu's Libc releases as the gold-standard. Each technique is verified to work on corresponding Ubuntu releases.
You can run apt source libc6 to download the source code of the Libc your are using on Debian-based operating system. You can also click
We came up with the idea during a hack meeting, and have implemented the following techniques:
| File | Technique | Glibc-Version | Patch | Applicable CTF Challenges | |
|---|---|---|---|---|---|
| first_fit.c | Demonstrating glibc malloc's first-fit behavior. | ||||
| calc_tcache_idx.c | Demonstrating glibc's tcache index calculation. | ||||
| fastbin_dup.c | Tricking malloc into returning an already-allocated heap pointer by abusing the fastbin freelist. | latest | |||
| fastbin_dup_into_stack.c | Tricking malloc into returning a nearly-arbitrary pointer by abusing the fastbin freelist. | latest | 9447-search-engine, 0ctf 2017-babyheap | ||
| fastbin_dup_consolidate.c | Tricking malloc into returning an already-allocated heap pointer by putting a pointer on both fastbin freelist and the top chunk. | latest | Hitcon 2016 SleepyHolder | ||
| unsafe_unlink.c | Exploiting free on a corrupted chunk to get arbitrary write. | latest | HITCON CTF 2014-stkof, Insomni'hack 2017-Wheel of Robots | ||
| house_of_spirit.c | Frees a fake fastbin chunk to get malloc to return a nearly-arbitrary pointer. | latest | hack.lu CTF 2014-OREO | ||
| poison_null_byte.c | Exploiting a single null byte overflow. | latest | PlaidCTF 2015-plaiddb, BalsnCTF 2019-PlainNote | ||
| house_of_lore.c | Tricking malloc into returning a nearly-arbitrary pointer by abusing the smallbin freelist. | latest | |||
| overlapping_chunks.c | Exploit the overwrite of a freed chunk size in the unsorted bin in order to make a new allocation overlap with an existing chunk | < 2.29 | patch | hack.lu CTF 2015-bookstore, Nuit du Hack 2016-night-deamonic-heap | |
| overlapping_chunks_2.c | Exploit the overwrite of an in use chunk size in order to make a new allocation overlap with an existing chunk | < 2.29 | patch | ||
| mmap_overlapping_chunks.c | Exploit an in use mmap chunk in order to make a new allocation overlap with a current mmap chunk | latest | |||
| house_of_force.c | Exploiting the Top Chunk (Wilderness) header in order to get malloc to return a nearly-arbitrary pointer | < 2.29 | patch | Boston Key Party 2016-cookbook, BCTF 2016-bcloud | |
| unsorted_bin_into_stack.c | Exploiting the overwrite of a freed chunk on unsorted bin freelist to return a nearly-arbitrary pointer. | < 2.29 | patch | ||
| unsorted_bin_attack.c | Exploiting the overwrite of a freed chunk on unsorted bin freelist to write a large value into arbitrary address | < 2.29 | patch | 0ctf 2016-zerostorage | |
| large_bin_attack.c | Exploiting the overwrite of a freed chunk on large bin freelist to write a large value into arbitrary address | latest | 0ctf 2018-heapstorm2 | ||
| house_of_einherjar.c | Exploiting a single null byte overflow to trick malloc into returning a controlled pointer | latest | Seccon 2016-tinypad | ||
| house_of_water.c | Exploit a UAF or double free to gain leakless control of the t-cache metadata and a leakless way to link libc in t-cache | latest | 37c3 Potluck - Tamagoyaki | ||
| sysmalloc_int_free.c | Demonstrating freeing the nearly arbitrary sized Top Chunk (Wilderness) using malloc (sysmalloc _int_free() ) |
latest | |||
| house_of_orange.c | Exploiting the Top Chunk (Wilderness) in order to gain arbitrary code execution | < 2.26 | patch | Hitcon 2016 houseoforange | |
| house_of_tangerine.c | Exploiting the Top Chunk (Wilderness) in order to trick malloc into returning a completely arbitrary pointer by abusing the tcache freelist | >= 2.26 | PicoCTF 2024- high frequency troubles | ||
| house_of_roman.c | Leakless technique in order to gain remote code execution via fake fastbins, the unsorted_bin attack and relative overwrites. | < 2.29 | patch | ||
| tcache_poisoning.c | Tricking malloc into returning a completely arbitrary pointer by abusing the tcache freelist. (requires heap leak on and after 2.32) | > 2.25 | patch | ||
| tcache_house_of_spirit.c | Frees a fake chunk to get malloc to return a nearly-arbitrary pointer. | > 2.25 | |||
| house_of_botcake.c | Bypass double free restriction on tcache. Make tcache_dup great again. |
> 2.25 | |||
| tcache_stashing_unlink_attack.c | Exploiting the overwrite of a freed chunk on small bin freelist to trick malloc into returning an arbitrary pointer and write a large value into arbitraty address with the help of calloc. | > 2.25 | Hitcon 2019 one punch man | ||
| fastbin_reverse_into_tcache.c | Exploiting the overwrite of a freed chunk in the fastbin to write a large value into an arbitrary address. | > 2.25 | |||
| house_of_mind_fastbin.c | Exploiting a single byte overwrite with arena handling to write a large value (heap pointer) to an arbitrary address | latest | |||
| house_of_storm.c | Exploiting a use after free on both a large and unsorted bin chunk to return an arbitrary chunk from malloc | < 2.29 | |||
| house_of_gods.c | A technique to hijack a thread's arena within 8 allocations | < 2.27 | |||
| decrypt_safe_linking.c | Decrypt the poisoned value in linked list to recover the actual pointer | >= 2.32 | |||
| safe_link_double_protect.c | Leakless bypass for PROTECT_PTR by protecting a pointer twice, allowing for arbitrary pointer linking in t-cache | >= 2.32 | 37c3 Potluck - Tamagoyaki | ||
| tcache_dup.c(obsolete) | Tricking malloc into returning an already-allocated heap pointer by abusing the tcache freelist. | 2.26 - 2.28 | patch |
The GnuLibc is under constant development and several of the techniques above have let to consistency checks introduced in the malloc/free logic.
Consequently, these checks regularly break some of the techniques and require adjustments to bypass them (if possible).
We address this issue by keeping multiple versions of the same technique for each Glibc-release that required an adjustment.
The structure is glibc_<version>/technique.c.
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.
- make sure you have the following packages/tools installed:
patchelf zstd wget(of course alsobuild-essentialor similar for compilers,make, ...) - also,
/usr/bin/pythonmust be/point to yourpythonbinary (e. g./usr/bin/python3)
git clone https://github.com/shellphish/how2heap
cd how2heap
make clean base
./malloc_playgroundNotice that this will link the binaries with your system libc. If you want to play with other libc versions. Please refer to Complete Setup.
You will encounter symbol versioning issues (see this) if you try to LD_PRELOAD libcs to a binary that's compiled on your host machine.
We have two ways to bypass it.
This one tells linker to link the target binary with the target libc.
git clone https://github.com/shellphish/how2heap
cd how2heap
H2H_USE_SYSTEM_LIBC=N make v2.23This will link all the binaries against corresponding libcs. What's better is that it comes with debug symbols. Now you can play with any libc versions on your host machine. In this example, it will compile all glibc-2.23 binaries and link them with libc-2.23. You can change the number to play with other libc versions.
This uses Docker-based approach to complie binaries inside an old ubuntu container so it is runnable with the target libc version.
git clone https://github.com/shellphish/how2heap
cd how2heap
# the next command will prepare the target binary so it runs with
# the expected libc version
make base
./glibc_run.sh 2.30 ./malloc_playground -d -p
# now you can play with the binary with glibc-2.30
# and even debug it with the correct symbols
readelf -d -W malloc_playground | grep RUNPATH # or use checksec
readelf -l -W malloc_playground | grep interpreter
gdb -q -ex "start" ./malloc_playgroundThere are some heap exploitation tools floating around.
The malloc_playground.c file given is the source for a program that prompts the user for commands to allocate and free memory interactively.
Examine the glibc heap in gdb: https://github.com/scwuaptx/Pwngdb
An exploitation-centric gdb plugin that provides the ability to view/tamper with the glibc heap: https://github.com/pwndbg/pwndbg
Another excellent gdb plugin that provides the ability to examine the glibc heap: https://github.com/hugsy/gef
Examine the glibc heap in IDA Pro: https://github.com/danigargu/heap-viewer
Debugger that lets you set "checkpoints" as well as view and edit the heap using a hexeditor: https://github.com/haxkor/forkever
Helps you visualize heap operations by replacing addresses with symbols: https://github.com/Arinerron/heaptrace
Some good heap exploitation resources, roughly in order of their publication, are:
- glibc in-depth tutorial (https://heap-exploitation.dhavalkapil.com/) - book and exploit samples
- ptmalloc fanzine, a set of resources and examples related to meta-data attacks on ptmalloc (http://tukan.farm/2016/07/26/ptmalloc-fanzine/)
- A malloc diagram, from libheap (https://raw.githubusercontent.com/cloudburst/libheap/master/heap.png)
- Glibc Adventures: The Forgotten Chunk (https://go.contextis.com/rs/140-OCV-459/images/Glibc_Adventures-The_Forgotten_Chunks.pdf) - advanced heap exploitation
- Pseudomonarchia jemallocum (http://www.phrack.org/issues/68/10.html)
- The House Of Lore: Reloaded (http://phrack.org/issues/67/8.html)
- Malloc Des-Maleficarum (http://phrack.org/issues/66/10.html) - some malloc exploitation techniques
- Yet another free() exploitation technique (http://phrack.org/issues/66/6.html)
- 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
- The use of set_head to defeat the wilderness (http://phrack.org/issues/64/9.html)
- The Malloc Maleficarum (http://seclists.org/bugtraq/2005/Oct/118)
- OS X heap exploitation techniques (http://phrack.org/issues/63/5.html)
- Exploiting The Wilderness (http://seclists.org/vuln-dev/2004/Feb/25)
- Advanced Doug lea's malloc exploits (http://phrack.org/issues/61/6.html)
- GDB Enhanced Features (GEF) Heap Exploration Tools (https://hugsy.github.io/gef/commands/heap/)
- pwndbg Heap Commands (https://browserpwndbg.readthedocs.io/en/docs/commands/heap/heap/)
- Painless intro to the Linux userland heap (https://sensepost.com/blog/2017/painless-intro-to-the-linux-userland-heap/)
- Heap exploitation techniques that work on glibc-2.31 (https://github.com/StarCross-Tech/heap_exploit_2.31)
- Overview of GLIBC heap exploitation techniques (https://0x434b.dev/overview-of-glibc-heap-exploitation-techniques/)
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.
