8/12/2023 0 Comments Buffer overflow stack![]() ![]() Learn the basics in this buffer overflow attack videoĪ typical objective of such an attack is to inject malicious code to provide the attacker with a shell. What if we created a buffer overflow that overwrites the return address of the instruction pointer such that it returned into the stack? It would start to execute whatever was in the stack! If you loaded the stack with malicious code, you cause this code to run! Buffer Overflow Attacksīuffer overflows on the stack are a common exploitation method. When the function foo returns, the current stack frame is unallocated, and the contents of the previous eip are loaded into the eip register, in this case is the string “EEEE” (i.e., \圆9\圆9\圆9\圆9), meaning the next instruction the program will execute is whatever lives at address 0圆9696969. Space for current function’s local variables are allocated onto the stack, and current function’s esp grows downwards accordingly.The calling functions esp 4 bytes becomes the current functions ebp.Set the values of ebp, esp and eip of the current function:.The calling function’s eip and ebp are then pushed to the stack (in fact all the CPU’s registers are pushed to the stack, but we’ve omitted them for brevity).Any arguments for the new function are pushed on the stack.Save the values of ebp, esp and eip, of the calling function:.The new function becomes the current function and the previous function is called the calling function. When a function is called, the system creates a new stack frame. The relationship between the registers and memory looks like this: eip: the instruction pointer, which points points to the next instruction (in the text region) to be executed.It changes (downward) as the stack grows. esp: the stack pointer, which points to the current top of the stack frame.It is fixed within the current stack frame. ebp: the base pointer (also called the frame pointer), which points to the bottom of the stack frame.To keep track of this, the system uses the following hardware registers: What instruction the current function is to execute next.Where the current function’s stack frame ends.Where the current function’s stack frame begins.The program needs to keep track of a several important things: When a function completes, all those things are removed from the stack. When a new function is called, things are added to the stack. A stack frame is a region of the stack which is dedicated to the execution of a particular function. In this case you can think of the stack as being a little bit like a notebook that can be used to keep notes. | text | holds executable code (read only)Ī stack is a last-in first-out data structure. | data | holds global and static variables ![]() | heap | holds dynamically allocated data ![]()
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