Return-to-libc attack
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A return-to-libc attack is a computer security attack usually starting with a buffer overflow in which the return address on the call stack is replaced by the address of another instruction and an additional portion of the stack is overwritten to provide arguments to this function. This allows attackers to call preexisting functions without the need to inject malicious code into a program.
The shared library called "libc" provides the C runtime on UNIX style systems. Although the attacker could make the code return anywhere, libc is the most likely target, as it is always linked to the program, and it provides useful calls for an attacker (such as the system() call to execute an arbitrary program, which needs only one argument). This is why the exploit is called "return-to-libc" even when the return address may point to a completely different location.
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[edit] Protection from return-to-libc attacks
A non-executable stack can prevent some buffer overflow exploitation, however it cannot prevent a return-to-libc attack because in the return-to-libc attack only existing executable code is used. On the other hand these attacks can only call preexisting functions. Stack-smashing protection can prevent or obstruct exploitation as it may detect the corruption of the stack and possibly flush out the compromised segment. Address space layout randomization (ASLR) makes this type of attack extremely unlikely to succeed on 64-bit machines as the memory locations of functions are random. For 32-bit systems ASLR provides little benefit since there are only 16 bits available for randomization, and they can be defeated by brute force in a matter of minutes.[1]
[edit] Related attacks
Return-oriented programming is an elaboration of the techniques used in this attack, and can be used to execute more general operations by chaining individual smaller attacks that execute a small number of instructions at a time.
[edit] See also
- Buffer overflow
- Stack buffer overflow
- Stack-smashing protection
- No eXecute (NX) bit
- Address space layout randomization
- Return-oriented programming
[edit] References
- ^ Shacham, Hovav; Page, Matthew; Pfaff, Ben; Goh, Eu-Jin; Modadugu, Nagendra; and Boneh, Dan. "On the Effectiveness of Address-Space Randomization". Proceedings of Computer and Communications Security (CCS'04), October 25–29, 2004, Washington (DC). http://www.stanford.edu/~blp/papers/asrandom.pdf.
[edit] External links
- Bypassing non-executable-stack during exploitation using return-to-libc by c0ntex at InfoSecWriters.com
