ELF

The pwntools ELF class is the most useful class you will probably ever need, so understanding the full power of it will make your life easier. Essentially, the ELF class allows you to look up variables at runtime and stop hardcoding.

Creating an ELF object

Creating an ELF object is very simple.

elf = ELF('./vulnerable_program')

Getting a process

Rather than specifying another process, we can just get it from the ELF:

p = elf.process()

The PLT and GOT

Want to do a ret2plt?

puts_plt = elf.plt['puts']
puts_got = elf.got['puts']

Functions

Need to return to a function called vuln? Don't bother using a disassembler or debugger to find where it is.

main_address = elf.functions['vuln']

Note that elf.functions returns a Function object, so if you only want the address you can use elf.symbols:

main_address = elf.symbols['symbol']

elf.libc

When local, we can grab the libc the binary is running with:

libc = elf.libc

elf.search(needle, writable=False)

Search the entire binary for a specific sequence needle of characters. Very useful when trying to do a ret2libc. If writable is set it only checks for sections in memory that you can write to. Note this returns a generator so if you want the first match you have to enclose it in next().

binsh = next(libc.search(b'/bin/sh\x00'))

elf.address

elf.address is the base address of the binary. If the binary does not have PIE enabled, then it's absolute; if it does, all addresses are relative (they pretend the binary base is 0x0).

Setting the address value automatically updates the address of symbols, got, plt and functions, which makes it invaluable when adjusting for PIE or ASLR.

Let's say you leak the base address of libc while ASLR is enabled; with pwntools, it's ridiculously easy to get the location of system for a ret2libc.

libc = elf.libc
libc.address = 0xf7f23000           # You 'leaked' this

system = libc.symbols['system']
binsh = next(libc.search(b'/bin/sh\x00'))
exit_addr = libc.symbols['exit']

# Now you can do the ret2libc...