fakegethostbyname library
It's mainly a quick hack, a library that overrides gethostbyname.
Once I had an account on a openbsd box where I wanted to run a closed source
network application that usually connects to an hardcoded hostname. Since I
wanted to make it change behaviour, I was trying to get it resolve another ip
for the hardcoded hostname, but I didn't had root access to the box, neither I
wanted to just quickhack the binary, so I coded a little wrapper for the
gethostbyname(3) function to make it resolve some hosts as I wanted, else just
act as system gethostbyname.
This silly trick uses the LD_PRELOAD loader variable, that forces the load of a library when linking.
An example of how fakegethostbyname library works:
$ ./resolve www.lupo.rm.it www.uniroma2.it www.google.com
www.lupo.rm.it resolved to 217.220.29.169
www.uniroma2.it resolved to 160.80.2.16
www.google.com resolved to 216.239.59.99
$ LD_PRELOAD=./fakegethostbyname.so \
HOSTS_OVERRIDE=www.uniroma2.it=1.2.3.4,www.google.com=5.6.7.8 \
./resolve www.lupo.rm.it www.uniroma2.it www.google.com
www.lupo.rm.it resolved to 217.220.29.169
www.uniroma2.it resolved to 1.2.3.4
www.google.com resolved to 5.6.7.8
Tested on:
Linux 2.4FreeBSD 5-CURRENT
Releases:
Tue Nov 11 22:10:34 CET 2003, first release
Files
fakegethostbyname-1.0.tar.bz2 (source)