Build a Return-Oriented Programming Chain

Building a ROP Chain

A ROP chain is a carefully constructed sequence of gadget addresses placed on the stack. Each gadget performs a small operation and ends with ret, which loads the next gadget address. By chaining enough gadgets, attackers perform arbitrary computations without injecting new code.

Constructing a Chain

Find gadgets with tools like ROPgadget, ropper, or objdump. For calling system("/bin/sh") on x86-64 Linux:

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Challenges include NULL bytes in addresses (terminate strcpy), 16-byte stack alignment before system(), and ASLR randomizing all addresses.

For This Exercise

You will document ROP chain construction conceptually, including gadget types and stack layout. The pop-rdi/system chain is the canonical first ROP exploit taught in pwn-focused CTFs, and getting stack alignment right trips up most first-time exploit writers.

Gadget Hunting in Practice

ROPgadget scans executable segments for sequences ending in ret. Libc is gadget-rich because it contains millions of instructions compiled from C source. Useful gadgets need not be full functions; pop rdi; ret is just two instructions. Defenders deploy Control Flow Integrity and shadow stacks, but understanding basic chain construction remains essential for CTF competitions and vulnerability research on unpatched services.