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I created the user MY_USER. Set his home dir to /var/www/RESTRICTED_DIR, which is the path he should be restricted to. Then I edited sshd_config and set:

Match user MY_USER
  ChrootDirectory /var/www/RESTRICTED_DIR

Then I restarted ssh. Made MY_USER owner (and group owner) of RESTRICTED_DIR, and chmodded it to 755. I get

Accepted password for MY_USER
session opened for user MY_USER by (uid=0)
fatal: bad ownership or modes for chroot directory component "/var/www/RESTRICTED_DIR"
pam_unix(sshd:session): session closed for user MY_USER

If I removed the 2 lines from sshd_config the user can login successfully. Of course it can access all the server though. What's the problem? I even tried to chown RESTRICTED_DIR to root (as I read somewhere that someone solved this same problem doing it). No luck..

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5 Answers 5

Reset to default
112

From the man page:

ChrootDirectory
Specifies the pathname of a directory to chroot(2) to after authentication. All components of the pathname must be root-owned directories that are not writable by any other user or group. After the chroot, sshd(8) changes the working directory to the user's home directory.

My guess is one or more of the directories on the path do not meet those requirements (my suspicion is www is owned or writable by your web user, not root).
Go back and follow the directions, ensuring that the requirements above in bold italics are met.

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13
  • 3
    Ok! Solved. I set the chrooted dir a level up. Then I gave 777 perms to the original chrooted_dir. It's working :)
    – MultiformeIngegno
    Mar 30, 2014 at 18:34
  • 2
    Despite what the manpage says, and even with the group set to 'root', I had to set g-w permission before it would work (Ubuntu 14.04). The manpage should say All components of the pathname must be root-owned directories that are not writable by any other user or any group at all sudo chown root:root -R /path/to/home; sudo chmod 755 -R /path/to/home
    – mmell
    Jan 15, 2015 at 23:32
  • 4
    I know this is quite old, but instead of modifying the permissions for the /var/www path directly, which might break apache, you'd be far better off putting your sftp directory in another path, then using URL mapping in Apache to point to the other directory. Check the documentation here httpd.apache.org/docs/2.4/urlmapping.html under Files Outside DocumentRoot
    – Daniel
    Sep 3, 2016 at 2:58
  • 7
    This drives me crazy... If nobody excepted root has write access to it, how is the user logging in supposed to upload new files? It defeats the entire purpose why I set up sftp in the first place.
    – jlh
    Jun 26, 2018 at 20:47
  • 2
    @jlh Just create a dir owned by your user with write perms below your chroot dir: /var/www/RESTRICTED_DIR/<youruser>
    – Holger Böhnke
    Apr 3, 2022 at 9:01
46

ChrootDirectory directory must be owned by root and have 755 mode:

sudo chown root:root /var/www/RESTRICTED_DIR
sudo chmod 755 /var/www/RESTRICTED_DIR

Ok, now all files into /var/www/RESTRICTED_DIR must be owned by MY_USER, which must belong to www-data group, and have 775 mode to allow group permissions, like this:

sudo usermod -a -G www-data MY_USER
sudo chown MY_USER:www-data /var/www/RESTRICTED_DIR/*
sudo chmod 775 -R /var/www/RESTRICTED_DIR/*

NOTE: Remember is a good practice allow access only to an htdocs folder if you are configuring apache.

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3
  • 4
    Pretty sure it should be sudo usermod -a -G www-data MY_USER as the group should come after -G
    – sMyles
    Dec 21, 2016 at 17:28
  • 3
    This works but I cannot upload new files to the directory, I only can modify files created before with root account and with the user ownership.
    – dlopezgonzalez
    Jan 31, 2019 at 12:29
  • 1
    @dlopezgonzalez The same thing happens for me. The best solution I can come up with is to create another directory (e.g. /var/www/RESTRICTED_DIR/uploads) that is owned by the user. If this isn't ideal for you, you could relocated the ChrootDirectory and use a symlink (e.g. /var/www/RESTRICTED_DIR is a symlink that points to /sftp/uploads (where /sftp is owned by root and /sftp/uploads is owned by the user)
    – rinogo
    Feb 21, 2020 at 19:02
4

After some troubleshooting today, I realized that root must also be able to write to the directories.

The following did not work:

$ ls -ld /mnt/synology03/files/
dr-xr-xr-x 1 root root 156 Oct  8 20:10 /mnt/synology03/files/
$ ls -ld /mnt/synology03
drwxr-xr-x 7 root root 4096 Oct  1 21:26 /mnt/synology03
$ ls -ld /mnt
drwxr-xr-x 6 root root 4096 Feb  8 10:01 /mnt
$ ls -ld /
drwxr-xr-x 24 root root 4096 Jan 14 09:22 /

As soon as I fixed this, my chroot started working.

$ sudo chmod 755 /mnt/synology03/files/
$ ls -ld /mnt/synology03/files/
drwxr-xr-x 1 root root 156 Oct  8 20:10 /mnt/synology03/files/
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4

In my case below steps worked.

  1. useradd -d /data/ftp/user1 -s /bin/false -g users -G sftponly user1
  2. passwd user1
  3. chown root:root /data/ftp/user1
  4. rights for group & others chmod go+rx /data/ftp/user1
  5. mkdir /data/ftp/user1/{upload,download}
  6. chown user1:users /data/ftp/user1/{upload,download}
  7. sftp user1@ipaddress_server

Check if user1 can write to /data/ftp/user1/{upload,download}

Better if user1 is only allowed sftp and not ssh access. Also the user1 should be chroot to his home director. This will help https://medium.com/tensult/configure-ftp-on-aws-ec2-85b5b56b9c94

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3
  • What about the passwd of user1? Lock it??
    – John Greene
    Apr 24, 2022 at 18:51
  • Yes. Need to set a password for the user1. Missed that step which I have added to the answer now.
    – W R
    Apr 26, 2022 at 2:25
  • Just don’t lock the root account or you’ll get a cryptic error when trying sudo from within a root account. Caveat.
    – John Greene
    Apr 26, 2022 at 12:17
0

Made it work for /a/b/c/CHROOT/stuff like this:

  • a, b, c and CHROOT - root:root 755
  • stuff - root:CHROOTED_USER_GROUP 775

Then the user can login with sftp and upload files to the /stuff directory.

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