Great question—let’s break down the role of the caller’s EBP in these two buffer overflow scenarios clearly, since it’s easy to mix up their purposes!

1. Full Return Address Overflow Attack #

In this classic buffer overflow scenario, the caller's EBP is little more than a stepping stone to reach the actual target: the return address. Here's how it fits in:

• When you overflow the vulnerable buffer, you first overwrite local variables, then you overwrite the caller's EBP (saved on the stack immediately after the local buffer). But this overwriting isn't the goal—it's just collateral damage, a necessary step to get to the return address sitting right above EBP.
• The real objective is to overwrite that return address to point to attacker-controlled shellcode (or a ROP gadget). The mangled EBP doesn't directly contribute to control flow here; once the function executes ret, we already have control of EIP, so the messed-up EBP is irrelevant unless the code later uses it (by which point we're already in control).

2. Single-Byte EBP Overflow Attack #

This is a craftier scenario where you can't fully overflow to reach the return address (maybe due to partial bounds checking or limited buffer space), so the caller's EBP becomes the primary target. Here's its critical role:

• The caller's EBP holds the base pointer of the previous stack frame. By only overwriting its least significant byte (LSB), you shift the EBP's value to a new location within your attacker-controlled buffer when the function returns and executes pop ebp.
• Once EBP is pointing into your buffer, any subsequent code that uses EBP to reference stack variables (like mov eax, [ebp-0x8]) will start reading from your controlled data instead of the original stack frame.
• This shift can also manipulate the stack pointer (ESP) indirectly. For example, if the calling function uses EBP to calculate stack offsets for operations like push or pop, the modified EBP will force those operations to interact with your buffer, eventually letting you take control of EIP without ever directly overwriting the return address.

Core Difference at a Glance #

• Full return address overflow: Caller EBP is a barrier to cross; overwriting it is incidental, and the return address is the direct path to EIP control.
• Single-byte EBP overflow: Caller EBP is the attack's focal point. Modifying it manipulates the stack frame context, which indirectly lets you hijack control by tricking the program into using your buffer data as critical stack values.

内容的提问来源于stack exchange，提问作者wulfgarpro