The rop chain builder based off of angr
angrop is a rop gadget finder and chain builder
angrop is a tool to automatically generate rop chains.
It is built on top of angr's symbolic execution engine, and uses constraint solving for generating chains and understanding the effects of gadgets.
angrop should support all the architectures supported by angr, although more testing needs to be done.
Typically, it can generate rop chains (especially long chains) faster than humans.
It includes functions to generate chains which are commonly used in exploitation and CTF's, such as setting registers, and calling functions.
The ROP analysis finds rop gadgets and can automatically build rop chains.
>>> import angr, angrop >>> p = angr.Project("/bin/ls") >>> rop = p.analyses.ROP() >>> rop.find_gadgets() >>> chain = rop.set_regs(rax=0x1337, rbx=0x56565656) >>> chain.payload_str() b'\xb32@\x00\x00\x00\x00\x007\x13\x00\x00\x00\x00\x00\x00\xa1\x18@\x00\x00\x00\x00\x00VVVV\x00\x00\x00\x00' >>> chain.print_payload_code() chain = b"" chain += p64(0x410b23) # pop rax; ret chain += p64(0x1337) chain += p64(0x404dc0) # pop rbx; ret chain += p64(0x56565656)
# angrop includes methods to create certain common chains # setting registers chain = rop.set_regs(rax=0x1337, rbx=0x56565656) # writing to memory # writes "/bin/sh\0" to address 0x61b100 chain = rop.write_to_mem(0x61b100, b"/bin/sh\0") # calling functions chain = rop.func_call("read", [0, 0x804f000, 0x100]) # adding values to memory chain = rop.add_to_mem(0x804f124, 0x41414141) # chains can be added together to chain operations chain = rop.write_to_mem(0x61b100, b"/home/ctf/flag\x00") + rop.func_call("open", [0x61b100,os.O_RDONLY]) + ... # chains can be printed for copy pasting into exploits >>> chain.print_payload_code() chain = b"" chain += p64(0x410b23) # pop rax; ret chain += p64(0x74632f656d6f682f) chain += p64(0x404dc0) # pop rbx; ret chain += p64(0x61b0f8) chain += p64(0x40ab63) # mov qword ptr [rbx + 8], rax; add rsp, 0x10; pop rbx; ret ...
Gadgets contain a lot of information:
For example look at how the following code translates into a gadget
0x403be4: and ebp,edi 0x403be6: mov QWORD PTR [rbx+0x90],rax 0x403bed: xor eax,eax 0x403bef: add rsp,0x10 0x403bf3: pop rbx 0x403bf4: ret
>>> print(rop.gadgets) Gadget 0x403be4 Stack change: 0x20 Changed registers: set(['rbx', 'rax', 'rbp']) Popped registers: set(['rbx']) Register dependencies: rbp: [rdi, rbp] Memory write: address (64 bits) depends on: ['rbx'] data (64 bits) depends on: ['rax']
The dependencies describe what registers affect the final value of another register. In the example above, the final value of rbp depends on both rdi and rbp. Dependencies are analyzed for registers and for memory actions. All of the information is stored as properties in the gadgets, so it is easy to iterate over them and find gadgets which fit your needs.
>>> for g in rop.gadgets: if "rax" in g.popped_regs and "rbx" not in g.changed_regs: print(g) Gadget 0x4032b3 Stack change: 0x10 Changed registers: set(['rax']) Popped registers: set(['rax']) Register dependencies:
Allow strings to be passed as arguments to func_call(), which are then written to memory and referenced.
Add a function for open, read, write (for ctf's)
Allow using of angr objects such as BVV, BVS to make using symbolic values easy
The segment analysis for finding executable addresses seems to break on non-elf binaries often, such as PE files, kernel modules.
Allow setting constraints on the generated chain e.g. bytes that are valid.
Make sure to import angrop before calling proj.analyses.ROP()
Make sure to call find_gadets() before trying to make chains
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