glibc library provides functions such as
malloc to help developers manage the heap memory according to their use cases. It is the responsibility of the developer to:
freeany memory he/she has obtained using
- Do not
freethe same memory more than once.
- Ensure that memory usage does not go beyond the amount of memory requested, in other terms, prevent heap overflows.
Failing to do makes the software vulnerable to various kinds of attacks. Shellphish, a famous Capture the Flag team from UC Santa Barbara, has done a great job in listing a variety of heap exploitation techniques in how2heap. Attacks described in "The Malloc Maleficarum" by "Phantasmal Phantasmagoria" in an email to the "Bugtraq" mailing list are also described.
A summary of the attacks has been described below:
|First Fit||This is not an attack, it just demonstrates the nature of glibc's allocator||---|
||Disrupt the fastbin by freeing a chunk twice|
||Disrupting fastbin link structure|
|Unlink Exploit||Getting (nearly)arbitrary write access||Freeing a corrupted chunk and exploiting
|Shrinking Free Chunks||Making
||Corrupting a free chunk by decreasing its size|
|House of Spirit||Making
||Forcing freeing of a crafted fake chunk|
|House of Lore||Making
||Disrupting smallbin link structure|
|House of Force||Making
||Overflowing into top chunk's header|
|House of Einherjar||Making
||Overflowing a single byte into the next chunk|