CHEATSHEET.md

Intro

The following cheatsheet aims to give an overview of various things you can do with angr and act as a quick reference to check the syntax for something without having to dig through the deeper docs.

General getting started

Some useful imports

import angr #the main framework
import claripy #the solver engine

Loading the binary

proj = angr.Project("/path/to/binary", auto_load_libs=False) # auto_load_libs False for improved performance

States

Create a SimState object

state = proj.factory.entry_state()

Simulation Managers

Generate a simulation manager object

simgr = proj.factory.simulation_manager(state)

Exploring and analysing states

Choosing a different Exploring strategy

simgr.use_technique(angr.exploration_techniques.DFS())

Symbolically execute until we find a state satisfying our find= and avoid= parameters

avoid_addr = [0x400c06, 0x400bc7]
find_addr = 0x400c10d
simgr.explore(find=find_addr, avoid=avoid_addr)

found = simgr.found[0] # A state that reached the find condition from explore
found.solver.eval(sym_arg, cast_to=bytes) # Return a concrete string value for the sym arg to reach this state

Symbolically execute until lambda expression is True

simgr.step(until=lambda sm: sm.active[0].addr >= first_jmp)

This is especially useful with the ability to access the current STDOUT or STDERR (1 here is the File Descriptor for STDOUT)

simgr.explore(find=lambda s: "correct" in s.posix.dumps(1))

Memory Managment on big searches (Auto Drop Stashes):

simgr.explore(find=find_addr, avoid=avoid_addr, step_func=lambda lsm: lsm.drop(stash='avoid'))

Manually Exploring

simgr.step(step_func=step_func, until=lambda lsm: len(sm.found) > 0)

def step_func(lsm):
    lsm.stash(filter_func=lambda state: state.addr == 0x400c06, from_stash='active', to_stash='avoid')
    lsm.stash(filter_func=lambda state: state.addr == 0x400bc7, from_stash='active', to_stash='avoid')
    lsm.stash(filter_func=lambda state: state.addr == 0x400c10, from_stash='active', to_stash='found')
    return lsm

Enable Logging output from Simulation Manager:

import logging
logging.getLogger('angr.sim_manager').setLevel(logging.DEBUG)

Stashes

Move Stash:

simgr.stash(from_stash="found", to_stash="active")

Drop Stashes:

simgr.drop(stash="avoid")

Constraint Solver (claripy)

Create symbolic object

sym_arg_size = 15 #Length in Bytes because we will multiply with 8 later
sym_arg = claripy.BVS('sym_arg', 8*sym_arg_size)

Restrict sym_arg to typical char range

for byte in sym_arg.chop(8):
    initial_state.add_constraints(byte >= '\x20') # ' '
    initial_state.add_constraints(byte <= '\x7e') # '~'

Create a state with a symbolic argument

argv = [proj.filename]
argv.append(sym_arg)
state = proj.factory.entry_state(args=argv)

Use argument for solving:

sym_arg = angr.claripy.BVS("sym_arg", flag_size * 8)
argv = [proj.filename]
argv.append(sym_arg)
initial_state = proj.factory.full_init_state(args=argv, add_options=angr.options.unicorn, remove_options={angr.options.LAZY_SOLVES})

FFI and Hooking

Calling a function from ipython

f = proj.factory.callable(address)
f(10)
x=claripy.BVS('x', 64)
f(x) #TODO: Find out how to make that result readable

If what you are interested in is not directly returned because for example the function returns the pointer to a buffer you can access the state after the function returns with

>>> f.result_state
<SimState @ 0x1000550>

Hooking

There are already predefined hooks for libc functions (useful for statically compiled libraries)

proj = angr.Project('/path/to/binary', use_sim_procedures=True)
proj.hook(addr, angr.SIM_PROCEDURES['libc']['atoi']())

Hooking with Simprocedure:

class fixpid(angr.SimProcedure):
    def run(self):
            return 0x30

proj.hook(0x4008cd, fixpid())

Other useful tricks

Drop into an ipython if a ctr+c is recieved (useful for debugging scripts that are running forever)

import signal
def killmyself():
    os.system('kill %d' % os.getpid())
def sigint_handler(signum, frame):
    print 'Stopping Execution for Debug. If you want to kill the programm issue: killmyself()'
    if not "IPython" in sys.modules:
        import IPython
        IPython.embed()

signal.signal(signal.SIGINT, sigint_handler)

Get the calltrace of a state to find out where we got stuck

state = simgr.active[0]
print state.callstack

Get a basic block

block = proj.factory.block(address)
block.capstone.pp() #Capstone object has pretty print and other data about the dissassembly
block.vex.pp()      #Print vex representation

State manipulation

Write to state:

aaaa = claripy.BVV(0x41414141, 32) # 32 = Bits
state.memory.store(0x6021f2, aaaa)

Read Pointer to Pointer from Frame:

poi1 = new_state.solver.eval(new_state.regs.rbp)-0x10
poi1 = new_state.mem[poi1].long.concrete
poi1 += 0x8
ptr1 = new_state.mem[poi1].long.concrete 

Read from State:

key = []
for i in range(38):
    key.append(extractkey.mem[0x602140 + i*4].int.concrete)

Alternatively, the below expression is equivalent

key = extractkey.mem[0x602140].int.array(38).concrete

Debugging angr

Set Breakpoint at every Memory read/write:

new_state.inspect.b('mem_read', when=angr.BP_AFTER, action=debug_funcRead)
def debug_funcRead(state):
    print 'Read', state.inspect.mem_read_expr, 'from', state.inspect.mem_read_address

Set Breakpoint at specific Memory location:

new_state.inspect.b('mem_write', mem_write_address=0x6021f1, when=angr.BP_AFTER, action=debug_funcWrite)