On my system, /etc/group:
www-data:x:33:p
robber:x:1003:
In the jail:
robber:x:1003:
www-data:x:33:p,robber
I don't understand this:
$ whoami
robber
$ ll
total 4.0K
drwxrwxr-- 3 www-data www-data 4.0K Jan 4 16:08 2015/
$ cd 2015/
bash: cd: 2015/: Permission denied
So, despite the fact that user robber is part of group 33,
www-data, he still can't cd into 2015/, even though that
directory has group permissions of rwx!
The only way robber can access 2015 is if I use my root
account and change the permissions of that directory to
rwxrwxrwx.
This is even stranger:
$ ls 2015/
ls: cannot access 2015/01: Permission denied
01
The directory structure is 2015/01/, and when I try to list
2015/ it tells me "permission denied" and then goes ahead and
lists the directory.