Trampoline Sleds

A "trampoline sled" is a technique used to increase the reliability of exploitation by bypassing potential obstacles such as data corruption or unintended code execution paths. Trampoline sleds utilize multi-byte opcodes to create a series of instructions that effectively "jump" or "bounce" execution directly to the shellcode, regardless of the byte the return pointer hits.

Here's a more detailed explanation of how trampoline sleds work:

Traditional NOOP Sleds: In traditional exploitation techniques, like using NOOP sleds, a series of NOOP instructions (single-byte opcodes) are placed in the payload before the actual shellcode. The idea is that even if the exact address of the shellcode gets slightly offset due to memory layout variations or payload delivery mechanisms, the execution will still land somewhere within the NOOP sled, increasing the chances of successful exploitation.

Trampoline Sleds: Trampoline sleds take this concept further by using multi-byte opcodes that directly jump execution to the shellcode. Instead of relying on the NOP (No Operation) instruction (such as 0x90 in x86 assembly), trampoline sleds utilize other instructions, typically those that involve control flow redirection like unconditional jumps or calls.

Jumping Directly to Shellcode: The critical characteristic of trampoline sleds is that they contain instructions that effectively transfer control directly to the shellcode, bypassing any potential obstacles or byte alignment issues. So, even if the return pointer lands on any byte within the trampoline sled, the execution flow will be redirected to the shellcode without requiring additional execution steps or alignment adjustments.

Increasing Reliability: Trampoline sleds provide a more deterministic and controlled approach to redirecting execution flow to the shellcode, reducing the likelihood of exploitation failures due to memory layout variations or other factors.