How to enable touch id for sudo in Terminal

So, you have a mac computer with touch id and you would like to use it also when you do "sudo su -" on Terminal but there is no menu to let you set up this.
You actually can, via Terminal :)
PS: there is one small downside. You need to do this after each OS upgrade. But since it doesn't happen so often and the procedure is very simple, I am ok with it.

1. Become root with sudo command (you will have to type the password this time):

fmbpro:~ florian$ sudo su -
Password:
fmbpro:~ root# 

2. Go to /private/etc/pam.d/ and you will find a file there named sudo. Change its permissions so it can be writable:

fmbpro:pam.d root# ls -la sudo
-r--r--r--  1 root  wheel  246 Jun  8 03:23 sudo
fmbpro:pam.d root# chmod gou+w sudo 
fmbpro:pam.d root# ls -la sudo
-rw-rw-rw-  1 root  wheel  246 Jun  8 03:23 sudo

3. Add "auth sufficient pam_tid.so" right after the first line (the commented one). The file should look like this afterwards:

fmbpro:pam.d root# cat sudo 
# sudo: auth account password session
auth       sufficient     pam_tid.so
auth       sufficient     pam_smartcard.so
auth       required       pam_opendirectory.so
account    required       pam_permit.so
password   required       pam_deny.so
session    required       pam_permit.so

4. Edit back the permissions:

fmbpro:pam.d root# chmod gou-w sudo 
fmbpro:pam.d root# ls -la sudo 
-r--r--r--@ 1 root  wheel  283 Sep  3 01:05 sudo

5. Enjoy sudo with touch id :)