标签：angrctf __ sm init state 解题 angr found
angr脚本——以angrctf解题记录为参考
angr是用于逆向工程中进行二进制分析的一个python框架
符号执行 （Symbolic Execution）是一种程序分析技术。其可以通过分析程序来得到让特定代码区域执行的输入。使用符号执行分析一个程序时，该程序会使用符号值作为输入，而非一般执行程序时使用的具体值。在达到目标代码时，分析器可以得到相应的路径约束，然后通过约束求解器来得到可以触发目标代码的具体值。
以下脚本均用Python3执行，在笔者Ubuntu16.04虚拟机上通过，且能够得到正确的结果
0x00.白给题，简单脚本
import angr
p = angr.Project("./00_angr_find")
init_state = p.factory.entry_state()
sm = p.factory.simulation_manager(init_state)
sm.explore(find=0x08048678) # 输出GoodJob的地方
found_state = sm.found[0]
found_state.posix.dumps(0) # 标准输入
0x01.增加限制条件——explore函数中find和avoid的使用
import angr
import sys
def main(argv):
path_to_binary = argv[1]
project = angr.Project(path_to_binary)
initial_state = project.factory.entry_state()
simulation = project.factory.simgr(initial_state)
# Explore the binary, but this time, instead of only looking for a state that
# reaches the print_good_address, also find a state that does not reach
# will_not_succeed_address. The binary is pretty large, to save you some time,
# everything you will need to look at is near the beginning of the address
# space.
# (!)
print_good_address = 0x080485e5
will_not_succeed_address = 0x080485a8
simulation.explore(find=print_good_address, avoid=will_not_succeed_address)
if simulation.found:
solution_state = simulation.found[0]
print (solution_state.posix.dumps(0))
else:
raise Exception('Could not find the solution')
if __name__ == '__main__':
main(sys.argv)
0x02.find和avoid的进一步使用——以输出作为限制条件
project = angr.Project(path_to_binary)
initial_state = project.factory.entry_state()
simulation = project.factory.simgr(initial_state)
# Define a function that checks if you have found the state you are looking
# for.
def is_successful(state):
# Dump whatever has been printed out by the binary so far into a string.
stdout_output = state.posix.dumps(1)
# Return whether 'Good Job.' has been printed yet.
# (!)
return b'Good Job.' in stdout_output # :boolean
# Same as above, but this time check if the state should abort. If you return
# False, Angr will continue to step the state. In this specific challenge, the
# only time at which you will know you should abort is when the program prints
# "Try again."
def should_abort(state):
stdout_output = state.posix.dumps(1)
return b'Try again.' in stdout_output # :boolean
# Tell Angr to explore the binary and find any state that is_successful identfies
# as a successful state by returning True.
simulation.explore(find=is_successful, avoid=should_abort)
if simulation.found:
solution_state = simulation.found[0]
print(solution_state.posix.dumps(0))
else:
raise Exception('Could not find the solution')
if __name__ == '__main__':
main(sys.argv)
0x03.寄存器符号化
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path) # 执行前的初始化工作，例如生成中间语言等
start_addr = 0x80488d1 # 指定程序入口地址
init_state = p.factory.blank_state(addr=start_addr)
pass1 = claripy.BVS('pass1', 32) # 生成符号向量，前者为名称，后者为32/64位
pass2 = claripy.BVS('pass2', 32)
pass3 = claripy.BVS('pass3', 32)
init_state.regs.eax = pass1 # 设置初始状态时各寄存器的状态
init_state.regs.ebx = pass2
init_state.regs.edx = pass3
sm = p.factory.simulation_manager(init_state) # 开始模拟执行
def is_good(state):
return b'Good Job' in state.posix.dumps(1)
def is_bad(state):
return b'Try again' in state.posix.dumps(1)
sm.explore(find=is_good, avoid=is_bad) # 寻找结果
if sm.found:
found_state = sm.found[0]
password1 = found_state.solver.eval(pass1) # 求出结果
password2 = found_state.solver.eval(pass2)
password3 = found_state.solver.eval(pass3)
print("Solution: {:x} {:x} {:x}".format(password1, password2, password3))
else:
raise Exception("No solution found")
if __name__ == '__main__':
main(sys.argv)
0x04.栈符号化
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path) # 执行前的初始化工作，例如生成中间语言等
start_addr = 0x8048697 # 指定程序入口地址
init_state = p.factory.blank_state(addr=start_addr) # 初始化状态
pass1 = claripy.BVS('pass1', 32) # 生成符号向量，前者为名称，后者为32/64位
pass2 = claripy.BVS('pass2', 32)
# 对栈的模拟
# /-------- The stack --------\
# ebp -> | padding |
# |---------------------------|
# ebp - 0x01 | more padding |
# |---------------------------|
# ebp - 0x02 | even more padding |
# |---------------------------|
# . . . <- How much padding? Hint: how
# |---------------------------| many bytes is password0?
# ebp - 0x0b | password0, second byte |
# |---------------------------|
# ebp - 0x0c | password0, first byte |
# |---------------------------|
# ebp - 0x0d | password1, last byte |
# |---------------------------|
# . . .
# |---------------------------|
# ebp - 0x10 | password1, first byte |
# |---------------------------|
# . . .
# |---------------------------|
# esp -> | |
# \---------------------------/
#
padding_size = 8 # 栈中填充的长度,即输入的内容入栈时esp=ebp-0x08
# 对栈的情况进行模拟
# ebp是父ebp，保存完父函数ebp才开辟本函数栈空间，当函数执行完以后会有一个pop ebp恢复父函数ebp
# 但是因为我们要执行的代码与父函数无关，只用执行到find的地方就可以了，不用返回父函数接着执行，所以保存不保存父函数ebp都无所谓
# 即：ebp是上一个栈桢的栈基,在这个函数里,这个ebp的值是未知的,在这个angr程序里不会执行到在函数最后几条指令的pop ebp,自然也就不需要再push ebp
init_state.regs.ebp = init_state.regs.esp
init_state.regs.esp -= padding_size
# 模拟scanf的入栈过程
init_state.stack_push(pass1)
init_state.stack_push(pass2)
sm = p.factory.simulation_manager(init_state) # 开始模拟执行
def is_good(state):
return b'Good Job' in state.posix.dumps(1)
def is_bad(state):
return b'Try again' in state.posix.dumps(1)
sm.explore(find=is_good, avoid=is_bad) # 寻找结果
if sm.found:
found_state = sm.found[0]
password1 = found_state.solver.eval(pass1) # 求出结果
password2 = found_state.solver.eval(pass2)
print("Solution: {} {}".format(password1, password2))
else:
raise Exception("No solution found")
if __name__ == '__main__':
main(sys.argv)
0x05.静态内存符号化
import angr
import claripy
import sys
def main(argv):
path_to_binary = argv[1]
project = angr.Project(path_to_binary)
start_address = 0x8048606
initial_state = project.factory.blank_state(addr=start_address)
# The binary is calling scanf("%8s %8s %8s %8s").
# (!)
password0 = claripy.BVS('password0', 8*8)
password1 = claripy.BVS('password1', 8*8)
password2 = claripy.BVS('password2', 8*8)
password3 = claripy.BVS('password3', 8*8)
# Determine the address of the global variable to which scanf writes the user
# input. The function 'initial_state.memory.store(address, value)' will write
# 'value' (a bitvector) to 'address' (a memory location, as an integer.) The
# 'address' parameter can also be a bitvector (and can be symbolic!).
# (!)
password0_address = 0xa29faa0
initial_state.memory.store(password0_address, password0)
password1_address = 0xa29faa8
initial_state.memory.store(password1_address, password1)
password2_address = 0xa29fab0
initial_state.memory.store(password2_address, password2)
password3_address = 0xa29fab8
initial_state.memory.store(password3_address, password3)
simulation = project.factory.simgr(initial_state)
def is_successful(state):
stdout_output = state.posix.dumps(sys.stdout.fileno())
return b'Good Job.' in stdout_output
def should_abort(state):
stdout_output = state.posix.dumps(sys.stdout.fileno())
return b'Try again.' in stdout_output
simulation.explore(find=is_successful, avoid=should_abort)
if simulation.found:
solution_state = simulation.found[0]
# Solve for the symbolic values. We are trying to solve for a string.
# Therefore, we will use eval, with named parameter cast_to=str
# which returns a string instead of an integer.
# (!)
solution0 = solution_state.se.eval(password0,cast_to=bytes).decode("utf-8")
solution1 = solution_state.se.eval(password1,cast_to=bytes).decode("utf-8")
solution2 = solution_state.se.eval(password2,cast_to=bytes).decode("utf-8")
solution3 = solution_state.se.eval(password3,cast_to=bytes).decode("utf-8")
solution = ' '.join([ solution0, solution1, solution2, solution3 ])
print (solution)
else:
raise Exception('Could not find the solution')
if __name__ == '__main__':
main(sys.argv)
0x06.动态内存符号化
# malloc出来的内存地址是不确定的，但是，我们可以跳过malloc和scanf，给指针变量buffer一个指定的内存地址
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path)
start_address = 0x0804869E # 跳过malloc和scanf
init_state = p.factory.blank_state(addr=start_address)
buffer0 = 0x44444444 # 随便指定两块内存地址,存放符号化向量
buffer1 = 0x44444544
buffer0_addr = 0xa79a118 # 指向这两块内存地址的指针，存放他们的地址
buffer1_addr = 0xa79a120
# Note: by default, Angr stores integers in memory with big-endianness. To
# specify to use the endianness of your architecture, use the parameter
# endness=project.arch.memory_endness. On x86, this is little-endian.
# (!)
# 内存中的内容是小端序的，故要加上参数endness = p.arch.memory_endness,否则写入的地址是大端序的
init_state.memory.store(buffer0_addr, buffer0, endness=p.arch.memory_endness)
init_state.memory.store(buffer1_addr, buffer1, endness=p.arch.memory_endness)
# 存入符号向量
p0 = claripy.BVS('p0', 64)
p1 = claripy.BVS('p1', 64)
init_state.memory.store(buffer0, p0)
init_state.memory.store(buffer1, p1)
sm = p.factory.simulation_manager(init_state)
def is_successful(state):
return b'Good Job.' in state.posix.dumps(1)
def should_abort(state):
return b'Try again.' in state.posix.dumps(1)
sm.explore(find=is_successful, avoid=should_abort)
if sm.found:
solution = sm.found[0]
pass0 = solution.se.eval(p0, cast_to=bytes).decode("utf-8")
pass1 = solution.se.eval(p1, cast_to=bytes).decode("utf-8")
print("Solution: {} {}".format(pass0, pass1))
else:
raise Exception('Could not find the solution')
if __name__ == '__main__':
main(sys.argv)
0x07.文件符号化
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path)
# 从scanf及ignore_me后，memset前开始执行
start_addr = 0x80488de
init_state = p.factory.blank_state(addr=start_addr)
filename = "WCEXPXBW.txt"
filesize = 0x40
# 构造符号向量
password = init_state.solver.BVS("password", filesize*8)
# 构造符号化文件,SimFile函数用于构造文件信息，包括文件名，文件内容和文件大小
sim_file = angr.storage.SimFile(filename, content=password, size=filesize)
# 将符号化文件插入到初始状态中,angr.fs.insert是将文件插入到文件系统中，需要文件名与符号化的文件
init_state.fs.insert(filename, sim_file)
sm = p.factory.simgr(init_state)
def is_successful(state):
return b'Good Job.' in state.posix.dumps(1)
def should_abort(state):
return b'Try again.' in state.posix.dumps(1)
sm.explore(find=is_successful, avoid=should_abort)
if sm.found:
solution = sm.found[0]
password_str = solution.solver.eval(password, cast_to=bytes).decode("utf-8")
print("Solution: {} ".format(password_str))
else:
raise Exception('Could not find the solution')
if __name__ == '__main__':
main(sys.argv)
0x08.增加约束条件解决路径爆炸问题
import angr
import sys
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path)
start_addr = 0x0804862A
init_state = p.factory.blank_state(addr=start_addr)
buffer_addr = 0x0804A050
password = init_state.solver.BVS("password", 16*8)
init_state.memory.store(buffer_addr, password)
sm = p.factory.simgr(init_state)
check_addr = 0x08048565#此地址并非调用call check的地址，而是点进去看到的函数的代码段的起始地址
sm.explore(find=check_addr)#寻找各种到此函数的路径
if sm.found:
check_state = sm.found[0]
desired_string = "BWYRUBQCMVSBRGFU"
check_param1 = buffer_addr
check_param2 = 0x10
#从内存中把经过变化的buffer再取出来，进行后一步比较
check_bvs = check_state.memory.load(check_param1, check_param2)
check_constraint = desired_string == check_bvs
check_state.add_constraints(check_constraint)
password1 = check_state.solver.eval(password, cast_to=bytes).decode("utf-8")
print("Solution: {}".format(password1))
if __name__ == '__main__':
main(sys.argv)
0x09.设置hook函数解决路径爆炸问题
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path)
init_state = p.factory.entry_state()#从main函数开始，angr自动帮你处理输入
# Hook the address of where check_equals_ is called.
# (!)
check_addr = 0x080486B8#call check_equals这条指令的位置
check_skip_size = 5#
#自定义hook函数
@p.hook(check_addr, length = check_skip_size)#先指定call hook函数的位置，再指定call hook函数这条指令的大小
def check_hook(state):
user_input_addr = 0x0804A054
user_input_length = 16
user_input_bvs = state.memory.load(user_input_addr, user_input_length)#从指定的位置取出输入
desired_string = "XKSPZSJKJYQCQXZV"#我们想要的字符串
#hook函数的返回，返回值给到eax
state.regs.eax = claripy.If(desired_string == user_input_bvs, claripy.BVV(1, 32), claripy.BVV(0, 32))
def is_good(state):
return b'Good Job.' in state.posix.dumps(1)
def is_bad(state):
return b'Try again.' in state.posix.dumps(1)
sm = p.factory.simgr(init_state)
sm.explore(find=is_good, avoid=is_bad)
if sm.found:
found_state = sm.found[0]
print("Solution: {}".format(found_state.posix.dumps(0)))
else:
raise Exception("Solution Not found")
if __name__ == '__main__':
main(sys.argv)
0x0A.hook所有同名函数
import angr
import sys
import claripy
def main(argv):
bin_path = argv[1]
p = angr.Project(bin_path)
init_state = p.factory.entry_state()
#将hook函数设置成一个类
class mySimPro(angr.SimProcedure):
def run(self, to_check, length):#传入用户输入的地址和输入长度
user_input_buffer_address = to_check
user_input_buffer_length = length
angr_bvs = self.state.memory.load(user_input_buffer_address, user_input_buffer_length)#让angr从内存中把输入的东西提取出来
desired = 'WQNDNKKWAWOLXBAC'
return claripy.If(desired == angr_bvs, claripy.BVV(1, 32), claripy.BVV(0, 32))
check_symbol = "check_equals_WQNDNKKWAWOLXBAC"#函数名称
p.hook_symbol(check_symbol, mySimPro())
sm = p.factory.simgr(init_state)
def is_good(state):
return b"Good Job" in state.posix.dumps(1)
def is_bad(state):
return b"Try again" in state.posix.dumps(1)
sm.explore(find=is_good, avoid=is_bad)
if sm.found:
found_state = sm.found[0]
password = found_state.posix.dumps(0)
print("Solution: {}".format(password.decode("utf-8")))
else:
raise Exception("Solution not found")
if __name__ == '__main__':
main(sys.argv)
未完待续
标签：angrctf,__,sm,init,state,解题,angr,found 来源： https://www.cnblogs.com/p0lar1s/p/14503379.html
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