Incorrect file ownership in chroot jail

I have set up a chroot jail for user chroottest in /home/chroot

Steps to reproduce:

root@pc# mkdir /home/chroot
root@pc# mkdir /home/chroot/dev
root@pc# mkdir /home/chroot/etc
root@pc# mkdir /home/chroot/bin
root@pc# mkdir /home/chroot/usr
root@pc# mkdir /home/chroot/usr/bin
root@pc# mkdir /home/chroot/usr/lib
root@pc# mkdir /home/chroot/usr/lib/terminfo
root@pc# mkdir /home/chroot/lib
root@pc# mkdir /home/chroot/lib/x86_64-linux-gnu
root@pc# mkdir /home/chroot/lib64
root@pc# 
root@pc# mknod -m 666 null c 1 3
root@pc# mknod -m 666 tty c 5 0
root@pc# mknod -m 666 zero c 1 5
root@pc# mknod -m 666 random c 1 8
root@pc# 
root@pc# cp /bin/bash /home/chroot/bin
root@pc# cp /usr/bin/ls /home/chroot/usr/bin
root@pc# cp /usr/bin/getent /home/chroot/usr/bin
root@pc# cp -av /usr/lib/terminfo /home/chroot/usr/lib/terminfo
root@pc#
root@pc# cp /lib/x86_64-linux-gnu/libtinfo.so.6 /home/chroot/lib/x86_64-linux-gnu/                           
root@pc# cp /lib/x86_64-linux-gnu/libdl.so.2 /home/chroot/lib/x86_64-linux-gnu/                    
root@pc# cp /lib/x86_64-linux-gnu/libc.so.6 /home/chroot/lib/x86_64-linux-gnu/
root@pc# cp /lib/x86_64-linux-gnu/libpthread.so.0 /home/chroot/lib/x86_64-linux-gnu/
root@pc# cp /lib/x86_64-linux-gnu/libselinux.so.1 /home/chroot/lib/x86_64-linux-gnu/
root@pc# cp /lib/x86_64-linux-gnu/libpcre2-8.so.0 /home/chroot/lib/x86_64-linux-gnu/
root@pc# cp /lib64/ld-linux-x86-64.so.2 /home/chroot/lib64/
root@pc#
root@pc# useradd chroottest -s /bin/bash
root@pc# passwd chroottest
root@pc#
root@pc# cp /etc/passwd /home/chroot/etc/
root@pc# cp /etc/group /home/chroot/etc/
root@pc# cp /etc/nsswitch.conf /home/chroot/etc/
root@pc# 
root@pc# echo -e "Match User chroottestntChrootDirectory /home/chroot" >> /etc/ssh/sshd_config
root@pc# systemctl reload sshd

When I connect via ssh as the user chroottest, I get chrooted correctly, but expected output of "ls -lh" would be

chroottest@pc# ls -lh
total 24K
drwxr-xr-x 2 root root 4.0K Nov  8 20:36 bin
drwxr-xr-x 2 root root 4.0K Nov  8 20:35 dev
drwxr-xr-x 2 root root 4.0K Nov  8 20:41 etc
drwxr-xr-x 3 root root 4.0K Nov  8 20:37 lib
drwxr-xr-x 2 root root 4.0K Nov  8 20:38 lib64
drwxr-xr-x 5 root root 4.0K Nov  8 21:00 usr

But it is

drwxr-xr-x  2   0   0 4.0K Nov  5 13:52 bin
drwxr-xr-x  2   0   0 4.0K Oct 22 05:47 dev
drwxr-xr-x  2   0   0 4.0K Nov  5 14:02 etc
drwxr-xr-x  4   0   0 4.0K Nov  5 13:57 lib
drwxr-xr-x  2   0   0 4.0K Oct 22 05:51 lib64
drwxr-xr-x  3   0   0 4.0K Nov  5 13:54 usr

I only see IDs instead of usernames and groups. File system rights are impossible to manage that way…

The content of nsswitch.conf ist:

root@pc# cat /home/chroot/etc/nsswitch.conf
passwd:         files systemd
group:          files systemd
shadow:         files
gshadow:        files

hosts:          files dns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

getent seems to be unable to get any information in the chroot environment:

chroottest@pc# getent passwd
chroottest@pc# getent passwd chroottest
chroottest@pc#

Any idea on what could be the problem?

Thanks, Mike

Asked By: mfischer

||

Ferenc W√°gner’s and Totor’s comments combined gave me the answer:

You have to copy /etc/nsswitch.conf and libnss.files.so.2 library to the chroot environment as well for the system to be able to interpret users and groups from passwd and group files.

Answered By: mfischer
Categories: Answers Tags: ,
Answers are sorted by their score. The answer accepted by the question owner as the best is marked with
at the top-right corner.