CTF常用python库PwnTools的使用学习

  之前主要是使用zio库,对pwntools的了解仅限于DynELF,以为zio就可以取代pwntools。后来发现pwntools有很多的高级用法都不曾听说过,这次学习一下用法,希望可以在以后的exp编写中能提供效率。

  PwnTools的官网如下:http://pwntools.com/

  安装方法是使用pip命令,pip install pwn。这样就可以安装上pwn库了。使用时用from pwn import *来进行调用。

连接

本地process()、远程remote()。对于remote函数可以接url并且指定端口。

IO模块

下面给出了PwnTools中的主要IO函数。这个比较容易跟zio搞混,记住zio是read、write,pwn是recv、send就可以了。

send(data) : 发送数据
sendline(data) : 发送一行数据,相当于在末尾加\n

recv(numb=4096, timeout=default) : 给出接收字节数,timeout指定超时
recvuntil(delims, drop=False) : 接收到delims的pattern
(以下可以看作until的特例)
recvline(keepends=True) : 接收到\n,keepends指定保留\n
recvall() : 接收到EOF
recvrepeat(timeout=default) : 接收到EOF或timeout

interactive() : 与shell交互

ELF模块

ELF模块用于获取ELF文件的信息,首先使用ELF()获取这个文件的句柄,然后使用这个句柄调用函数,和IO模块很相似。

下面演示了:获取基地址、获取函数地址(基于符号)、获取函数got地址、获取函数plt地址

>>> e = ELF('/bin/cat')
>>> print hex(e.address)  # 文件装载的基地址
0x400000
>>> print hex(e.symbols['write']) # 函数地址
0x401680
>>> print hex(e.got['write']) # GOT表的地址
0x60b070
>>> print hex(e.plt['write']) # PLT的地址
0x401680

数据处理

主要是对整数进行打包,就是转换成二进制的形式,比如转换成地址。p32、p64是打包,u32、u64是解包。

DynELF

DynELF是leak信息的神器。前提条件是要提供一个输入地址,输出此地址最少1byte数的函数。官网给出的说明是:Given a function which can leak data at an arbitrary address, any symbol in any loaded library can be resolved.

很叼啊,有木有。以下是官方例程

# Assume a process or remote connection
p = process('./pwnme')

# Declare a function that takes a single address, and
# leaks at least one byte at that address.
def leak(address):
    data = p.read(address, 4)
    log.debug("%#x => %s" % (address, (data or '').encode('hex')))
    return data

# For the sake of this example, let's say that we
# have any of these pointers.  One is a pointer into
# the target binary, the other two are pointers into libc
main   = 0xfeedf4ce
libc   = 0xdeadb000
system = 0xdeadbeef

# With our leaker, and a pointer into our target binary,
# we can resolve the address of anything.
#
# We do not actually need to have a copy of the target
# binary for this to work.
d = DynELF(leak, main)
assert d.lookup(None,     'libc') == libc
assert d.lookup('system', 'libc') == system

# However, if we *do* have a copy of the target binary,
# we can speed up some of the steps.
d = DynELF(leak, main, elf=ELF('./pwnme'))
assert d.lookup(None,     'libc') == libc
assert d.lookup('system', 'libc') == system

# Alternately, we can resolve symbols inside another library,
# given a pointer into it.
d = DynELF(leak, libc + 0x1234)
assert d.lookup('system')      == system

 

posted @ 2016-08-02 09:48  Ox9A82  阅读(36586)  评论(0编辑  收藏