question 1 2 3 4 5 Papa brought me a packed present! let's open it. Download : http://pwnable.kr/bin/flag This is reversing task. all you need is binary
analyse 下载下来，先用pwntools来看下checksec
1 2 3 4 5 6 7 8 9 ubuntu@VM-0-3-ubuntu:~$ checksec flag [*] '/home/ubuntu/flag' Arch: amd64-64-little RELRO: No RELRO Stack: No canary found NX: NX disabled PIE: No PIE (0x400000) RWX: Has RWX segments Packer: Packed with UPX
可以看到有UPX的壳，使用UPX工具去壳 官方链接
1 2 3 4 5 6 7 8 9 10 ubuntu@VM-0-3-ubuntu:~/upx$ ./upx -d ../flag Ultimate Packer for eXecutables Copyright (C) 1996 - 2018 UPX 3.95 Markus Oberhumer, Laszlo Molnar & John Reiser Aug 26th 2018 File size Ratio Format Name -------------------- ------ ----------- ----------- 883745 <- 335288 37.94% linux/amd64 flag Unpacked 1 file.
看起来好像没什么了，flag文件也非常的大
get flag 用strings命令看下里面的字符串，得到flag
1 2 ubuntu@VM-0-3-ubuntu:~$ strings flag | grep ':)' UPX...? sounds like a delivery service :)
flag：UPX...? sounds like a delivery service :)
