• Ssh Chrootdirectory Not Working
• Ssh Chroot Authorized_keys
• Sftp Chroot Jail

To chroot an SFTP directory, you must. Create a user and force root to be owner of it. Sudo mkdir /home/john useradd -d /home/john -M -N -g users john sudo chown root:root /home/john sudo chmod 755 /home/john. You may grant a user ssh access, whom you do not completely trust. You can limit what that user can see or run only ls, date, and internal bash commands by setting up a SSH chroot jail. Let us see how to create the chrooted jail for OpenSSH server on a Debain or Ubuntu Linux server. The following tutorial is tested on a Debian Linux server v8.1. The chrooted SSH will be installed in such a way that it will still use the configuration files of the standard OpenSSH Debian package which are in /etc/ssh/, and you will be able to use the standard OpenSSH Debian init script /etc/init.d/ssh. Therefore you do not have to create your own init script and configuration file. This type of chrooted ssh setup is commonly referred to as a chroot jail and we will be explaining it’s configuration step by step in this article. Chrooted jails are a means of separating specific user operations from the rest of the Linux system.

Parameter ChrootDirectory in /etc/ssh/sshd_config allows the specification of a chroot target directory which will then be used for all ssh and sftp sessions to this server. The target directory definition can utilize the %u and %h tokens to customize the target directory based on the username or the users home directory. Below are various scenarious and their configuration steps.

Case 1 : One common chroot directory for all users

In this example we will configure one target directory which will be used for all users. This is the simplest setup. We will use the directory /export/home/chroot in this example.

1. Create the chroot area by using the ftpconfig command:

2. Create the user and assign a password:

3. Add the following chroot option to the file /etc/ssh/sshd_config

4. Restart the ssh service to activate the configuration changes:

Case 2 : One common chroot directory for all users, but each user has its own home directory inside this area

In this example we will configure one target directory which will be used for chroot but each user has its own home directory inside this area. Opera gx ios. After a login the user will find himself inside the home directory but can still navigate inside the entire chroot area. The user is therefore not restricted to his own home directory. We will use /export/home/chroot as the common chroot directory.

1. Create the chroot area by using the ftpconfig command:

2. Create the user with its own home directory inside the chroot area and assign a password to the user:

3. Change the users home directory to make it valid and relative inside the chroot area. In this example it would be /testuser

4. Add the following chroot option to the file /etc/ssh/sshd_config file.

5. Restart the ssh service to activate the configuration change:

Case 3 : Each user has a separate chroot environment

In this example we will setup an individual chroot area for each user. Please note that this needs more disk space than the first two options as each area needs to be populated with a few required files. We will setup the user home directories under /export/home/chroot where each user will have its own full populated environment.

1. Create the target chroot environment by using the ftpconfig command:

2. Create the user and assign a password:

3. Add the following chroot configuration line to the file /etc/ssh/sshd_config:

4. Restart the ssh service to activate the configuration change:

Ssh Chrootdirectory Not Working

Jailkit howto - creating an SSH only shell in a chroot jail

Objectives

We want to create an account that can only do ssh in a chroot. This is for example useful on a firewall machine. Users can login to the firewall, but the only thing they can use the account for is to login to the next machine. Possibly the firewall machine only allows RSA key authentication, and the next machine allows only password authentication. Such a setup requires double authentication for a login.

There is a shell needed in the jail, because some program is required to start the ssh binary. We will look at a normal shell (bash), and the jailkit limited shell (jk_lsh).

Assumptions

Suppose the jail is /home/chrootusers and the user we want to jail is user john in group users. User john wants to login to our filewall (called firewall) using ssh, and then continue to another server (called realserver).

Ssh in a chroot jail

There are several requirements to get ssh working in a jail. First you need the /usr/bin/ssh binary. It needs two devices, /dev/urandom and /dev/tty. Obviously it needs several libraries as well, you can find them using ldd /usr/bin/ssh. The latest version of jk_init can do most of these things:

Note that the jk_init.ini file in the Jailkit tarball has defaults for Debian and Ubuntu. If you use jk_init on other operating systems you may need to use a different jk_init.ini file, or update the file locations in jk_init.ini yourself.

Getting the user into the chroot jail

To jail user john, he should have jk_chrootsh as shell in /etc/passwd. The entry in /etc/passwd should look like:

Inside the jail, user john needs to get his normal shell. We will discuss both bash and jk_lsh.

Bash in the chroot jail

Copy bash and it's libraries into the chroot jail using jk_cp:

Now edit /home/chrootusers/etc/passwd and make sure it contains a line like:

and make sure the group exists in /home/chrootusers/etc/group like this:

Now try to login using ssh john@firewall, and look for any errors in /var/log/auth.log.

Ssh Chroot Authorized_keys

Now user john can start his ssh session to john@realserver:

We can also do this in one go, by giving the second commandline as argument to the first commandline. This only works if the first commandline uses the option -t like this: Adobe photoshop mac download free. full version.

Jk_lsh in the chroot jail

Copy jk_lsh and it's libraries into the chroot jail, this can be done using jk_cp or with jk_init:

Now edit the /home/chrootusers/etc/passwd file, it should show something like:

jk_lsh can do some logging, but in order to do so it needs to have a /dev/log socket. This can be done using syslog, or by the jk_socketd. Edit /etc/jailkit/jk_socketd.ini and make sure it shows a section like:

Now restart jk_socketd, for example, kill it and restart it:

Any jk_socketd errors are logged into /var/log/daemon.log. If you try to login right now, you will find an error in /var/log/auth.log saying that john is not allowed to run a regular shell. And that is true, he's only allowed to do ssh, right!

To allow john to use ssh, we have to allow that, so we edit /home/chrootusers/etc/jailkit/jk_lsh.ini so it should allow ssh:

Now we can start ssh, but only ssh, and we do this by starting ssh immediately from the first ssh commandline. As with the previous example, also in this case we need to pass the -t option to the first ssh command:

If your configuration is correct, you should get both logins now, otherwise look for errors in /var/log/daemon.log or /var/log/auth.log.

Getting X forwarding to work trough the jail.

Ssh can do X forwarding. It creates a fake X-server and every X-client program can send it's data to this fake server, and ssh will forward it to the real server. Because we use two ssh sessions, the first ssh session needs to pass the X-client data to the second ssh session. This needs to be enabled on the ssh server, edit /etc/ssh/sshd_config and restart the ssh server afterwards, the file should have this line enabled:

There are also some environment variables that need to be passed on. Normally jk_chrootsh blocks all environment variables, so we edit /etc/jailkit/jk_chrootsh.ini and make it look like:

The sessions use an authorization protocol, handled by the xauth program. That means that we need the xauth program inside the jail. The xauth program needs libraries, and these libraries or not in the standard directories, that means that we need to add /etc/ld.so.conf and /etc/ld.so.cache to the jail. The ssh client has the path hardcoded into the executable, usually this path is /usr/bin/X11/xauth. It also needs /dev/null. Luckily the jk_init program can take care of this:

The ssh program tries to start xauth using /bin/sh, so we have to create /bin/sh as a symlink to /usr/sbin/jk_lsh:

Now ssh will try to start xauth using jk_lsh, so we have to allow that in the jk_lsh config file in the jail as well, edit /home/chrootusers/etc/jailkit/jk_lsh.ini and change it to this:

Sftp Chroot Jail

Now ssh with X-forwarding should be possible. Test it using:

If your configuration is correct, you should get both logins now, otherwise look for errors in /var/log/daemon.log or /var/log/auth.log. Getting debug output from your ssh program can help as well, use the commandline:

Finalizing

If you use procmail for email delivery, users can execute commands outside the jail using a .procmailrc in their homedir. You should use jk_procmailwrapper so users inside a jail cannot use mail delivery, or use aliases so procmail is not executed for these users.

To make things complete, we can edit the ssh server file /etc/ssh/sshd_config on the firewall and disable any password logins.

Because user john cannot login to the firewall using a password anymore, the system administrator (you) should edit the /home/chrootusers/home/john/.ssh/authorized_keys file and add john his public key there.

We should also add this jail to the jk_check config file, and run jk_check from the cron daemon every night.