Ubuntu SCP/SFTP Chroot Helper Script

setupChroot.sh

#!/bin/bash

username="user"
chroot="/path/to/folder/to/chroot"

# create the chrooted directory structure
mkdir $chroot/bin
mkdir $chroot/usr
mkdir $chroot/usr/bin
mkdir $chroot/usr/lib
mkdir $chroot/usr/lib/x86_64-linux-gnu
mkdir $chroot/usr/lib/openssh
mkdir $chroot/lib/
mkdir $chroot/lib/x86_64-linux-gnu
mkdir $chroot/lib64/
mkdir $chroot/etc
mkdir $chroot/dev
mkdir $chroot/dev/pts

# copy all dependencies
cp --parents `ldd /bin/bash | cut -d " " -f 3` $chroot
cp --parents `ldd /usr/bin/scp | cut -d " " -f 3` $chroot
cp --parents `ldd /usr/lib/openssh/sftp-server | cut -d " " -f 3` $chroot
cp --parents `ldd /bin/ls | cut -d " " -f 3` $chroot/
cp /lib/x86_64-linux-gnu/libnss* $chroot/lib/x86_64-linux-gnu/
cp /lib/x86_64-linux-gnu/libtic.so* $chroot/lib/x86_64-linux-gnu/
cp /lib64/ld-linux-x86-64.so.2 $chroot/lib64/
cp /usr/lib/x86_64-linux-gnu/libssl.so.1.1 $chroot/usr/lib/x86_64-linux-gnu/
cp /bin/bash $chroot/bin/
cp /usr/bin/scp $chroot/usr/bin/scp
cp /usr/lib/openssh/sftp-server $chroot/usr/lib/openssh/
cp /bin/ls $chroot/bin/
cp -vf /etc/{passwd,group} $chroot/etc/
cp -r /etc/ld.so* $chroot/etc/

# create non-files
mknod -m 666 $chroot/dev/null c 1 3
mknod -m 666 $chroot/dev/tty c 5 0
mknod -m 666 $chroot/dev/zero c 1 5
mknod -m 666 $chroot/dev/random c 1 8
mount --bind /dev/pts $chroot/dev/pts

# get the directory permissions right
chown $username.$username $chroot/. -R
chmod 0755 $chroot/bin
chown root.root $chroot
chmod 0755 $chroot

This will allow you to set a ChrootDirectory for a user or group in the sshd_config file on the server. Users will be jailed to that folder without access to the wider filesystem.

This has been tested on Ubuntu 20.04, and was modified from a version that worked for Amazon Linux.