How to set up a SFTP server with users chrooted in their home directories?

Question

I have been trying to set up a SFTP server with multiple users chrooting into their home directories. I followed the advice on this guide (Archive.org link) and then executed the following commands on the user's directories

chown root:root /home/user/
chmod 755 /home/user/

There is an additional folder in every user's home directory called public, which is owned by its user so as to allow them to create directories and upload and remove files as needed. (This was advised in the guide I mentioned earlier)

Now when I execute sftp -P 435 user@localhost, I get this error:

Write failed: Broken pipe
Couldn't read packet: Connection reset by peer

How do I proceed from here? The ultimate idea is to have each user on some other machine use FileZilla to log into their chrooted home directories and then be able to upload directories and files. All this in SFTP (because it's more secure)

Solution 1

That article also describes how to get a chrooted shell access, but since you just want a sftp-only account, just follow these instructions:

Edit /etc/ssh/sshd_config and add the lines:

SubSystem sftp internal-sftp
Match Group sftp
ChrootDirectory %h
ForceCommand internal-sftp
AllowTcpForwarding no

Find the line UsePAM yes and comment it:

#UsePAM yes

Without disabling this, my SSH server would crash on reloading/ restarting. Since I do not need fancy functions of PAM, this is fine.

For extra security, restrict the users who can login. If you forget to add SFTP users to the sftp group, you give them free shell access. Not a nice scenario. Because SSH cannot combine AllowUsers and AllowGroups (a login has to fulfill both rules), you've to create an additional group, say ssh-users. Add the users who are allowed to login (youruser below) over SSH:

sudo groupadd ssh-users
sudo gpasswd -a youruser ssh-users

And add the next line to /etc/ssh/sshd_config:

AllowGroups ssh-users sftp

Now proceed with modifying the permissions of the users home directory to allow for chrooting (example user sftp-user):

sudo chown root:sftp-user /home/sftp-user
sudo chmod 750 /home/sftp-user

Create a directory in which sftp-user is free to put any files in it:

sudo mkdir /home/sftp-user/public
sudo chown sftp-user: /home/sftp-user/public
sudo chmod 750 /home/sftp-user/public

Should you run in any problems, check /var/log/syslog and /var/log/auth.log for details. Run ssh or sftp with the -vvv option for debugging messages. For sftp, the option must appear before the host as in sftp -vvv user@host.

Solution 2

Just wanted to add that folder permissions up the directory tree need to be set a certain way.

sshd's strict ownership/permissions requirements dictate that every directory in the chroot path must be owned by root and only writable by the owner.

Source

I was having a very similar error, and fixing my directory permissions fixed the issue for me.

Solution 3

I'm using Ubuntu LTS 12.04 and after a lot of pain, this worked for me.

My Settings for /etc/ssh/sshd_config

Subsystem sftp internal-sftp -f AUTH -l VERBOSE
UsePAM yes
Match group sftp
  ChrootDirectory %h
  ForceCommand internal-sftp
  AllowTcpForwarding no

1. create group sftp:

   groupadd sftp

2. Create user directly with new sftp group attached:

   sudo useradd -d /ftpusers/HomeFolder -m UserName -g sftp -s /bin/false

3. set permissions for use with ssh for sftp:

   chown root:root HomeFolder

   chmod 755 HomeFolder

4. restart service:

   service ssh restart

Note, the home folder for the new sftp user has to be given root owner.

Solution 4

Here is a step by step guide to allow:

1. SFTP access to /home/bob/uploads for user bob
2. Lock bob out of SSH
3. Use username/passwords rather than keys:

First, edit your /etc/ssh/sshd_config file:

sudo nano /etc/ssh/sshd

Scroll down and modify:

PasswordAuthentication yes

and add this at the bottom:

Match Group sftpusers
ChrootDirectory %h
ForceCommand internal-sftp
AllowTcpForwarding no  

Press Ctrl-X to exit and save.

Now add the user:

sudo useradd bob
sudo passwd bob

Now add the groups and disable ssh:

sudo groupadd sftpusers
sudo usermod  -g sftpusers bob
sudo usermod -s /usr/bin/rssh bob
sudo usermod -d /home/bob bob

Now set permissions:

sudo chown root:root /home/bob/
sudo chmod 755 /home/bob/
sudo mkdir /home/bob/uploads
sudo chown bob /home/bob/uploads

sudo service sshd restart

All this is while logged in as a root user (ec2-user on Amazon Linux AMIs)

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Comments

[Ash]

The link provided is broken are you able to update this?

[Nitin Venkatesh]

@ash : Updated with the Archive.org link

[Max Masnick]

The directions here did not work for me, but following the directions in this question and the answer did: askubuntu.com/questions/134425/…

[jnunn]

you need a step after step 2 for sudo passwd UserName in order to set the user's password

[Admin]

I think #4 should read: service sshd restart

[Lekensteyn]

To the anonymous editor: the Match block was not added just before the UsePAM line. Instead, the Match block was appended to the file and the UsePAM line was somewhere earlier.

[jwbensley]

No on 12.04 it is "ssh" not "sshd"

[Peter Lozovitskiy]

Make sure 'UseLogin yes' option presents in sshd_config file.

[Deian]

sshd is for redhad linux

[jamescampbell]

This was my issue. It worked for me by adding in specifics for the user I was adding: Match User ftpusername and then ChrootDirectory %h and then ForceCommand internal-sftp. I did not need to comment out UsePAM or make any other changes otherwise besides setting chown root /home/ftpusername. Until I did the chown, I could not connect via sftp.

[Thamaraiselvam]

PasswordAuthentication yes is solution for me

[Simon Woodside]

You need to close the Match Group block by putting Match all after AllowTcpForwarding no. Then you won't need to comment out UsePAM and any lines that occur later.