zfisher

• Easy to hooking application in *nix

How to hook ?

• Google function prototype
• Write some code:

char sz_open[] = "open";

//--- open hook: open
typedef int (*hook_open)(char *filename, int access, int permission);
int open(char *filename, int access, int permission) {
	log_hook("open(\"%s\")", filename);
	struct handler* h = api_get(sz_open);
	if (!h) {
		log_fatal(" - api_get(\"%s\") fail", sz_open);
	}
	hook_open _open = h->original;
	return _open(filename, access, permission);
}
//--- close hook: open

• Hook by one line

api_register(sz_open);

• Compile source
• Use it by command

LD_PRELOAD=$LIB_HOOK application

Demo

• Hooking "open" API on /bin/cat:

khoai@khoai:bin$ LD_PRELOAD=.$LIB_HOOK /bin/cat /etc/issue
HOOK [init_fisher] pid: 21060
HOOK  - original("open") = 0x7f1b5b8a5150
HOOK open("/etc/issue")
Ubuntu 14.04.1 LTS \n \l

• Hooking "pread/pwrite" API on KyotoCabinet:

khoai@CPU11244:zkc$ LD_PRELOAD=$LIB_HOOK ./bin/zkcd debug get_rand
HOOK [init_fisher] pid: 17922
HOOK  - original("open") = 0x7fcea47dfbd0
HOOK  - original("pread") = 0x7fcea47dfc90
HOOK  - original("pwrite") = 0x7fcea47dfcf0
--- kcTest  !
HOOK open("db/kctest.kch")
HOOK open("db/kctest.kch.wal")
HOOK [fini_fisher] pid: 17922
HOOK --- pread: summary
HOOK  - pread(cnt: 206, total: 105574)
HOOK  - pwrite(cnt: 0, total: 0)
HOOK --- pony dump
 - pread(206): total(479882 us), avg(2329.52 us)
 - pwrite(0): total(0 us), avg(0.00 us)