On my system, /etc/group:
In the jail:robber:x:1003:
I don't understand this:$ whoami
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
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.
Why are group permissions seemingly ignored?
Why am I told that the directory can't be listed and then it goes ahead and lists it?
This is jailkit 2.17, built from tarball and debianized using debian/rules binary. The host system is Ubuntu 14.04.1.