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On Linux (Debian Squeeze) I would like to disable SSH login using password to some users (selected group or all users except root). But I do not want to disable login using certificate for them.

edit: thanks a lot for detailed answer! For some reason this does not work on my server:

Match User !root
PasswordAuthentication no

...but can be easily replaced by

PasswordAuthentication no
Match User root
PasswordAuthentication yes
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5
  • Maybe it's because of your indentation?
    – nil
    Commented Jan 30, 2013 at 7:19
  • 8
    It's worth mentioning that those lines under match should be at the end of the file
    – zidarsk8
    Commented Dec 25, 2013 at 1:29
  • 2
    !root also doesn't work for me. The second approach did the trick.
    – natenho
    Commented Jun 5, 2015 at 18:25
  • 1
    I've seen cases where Match User "!root,*" did the job.
    – Roman Hocke
    Commented Jun 5, 2017 at 14:58
  • 3
    Apropos of nothing, allowing password authentication for root is a very bad idea security-wise.
    – Aaron Mason
    Commented Nov 10, 2022 at 22:44

6 Answers 6

Reset to default
214

Try Match in sshd_config:

Match User user1,user2,user3,user4
    PasswordAuthentication no

Or by group:

Match Group users
    PasswordAuthentication no

Or, as mentioned in the comment, by negation:

Match User !root
    PasswordAuthentication no

Note that match is effective "until either another Match line or the end of the file." (the indentation isn't significant)

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16
  • 6
    prefer Match user !root for this case
    – 84104
    Commented Jun 30, 2011 at 16:41
  • 4
    @SpacemanSpiff That's what a) strong passwords and b) denyhosts/fail2ban are for.
    – ceejayoz
    Commented Jul 4, 2011 at 19:56
  • 2
    @deed02392 You can consider a key to be a really, really strong password if you like.
    – ceejayoz
    Commented Jul 5, 2013 at 13:26
  • 4
    It's so much stronger it's not in the same ball-park, that was my point. Password authentication should be disabled for root too and keys only allowed for logins.
    – deed02392
    Commented Jul 6, 2013 at 11:49
  • 2
    As per Trevor Hateley's answer, you'll probably need Match all on a new line afterwards, otherwise sshd will attempt to treat the remainder of the file as part of your block, and either refuse to restart with the Directive Foo is not allowed errors, or worse, start silently, but apply subsequent settings to the wrong people.
    – William Turrell
    Commented Mar 18, 2019 at 15:13
38

Match in sshd_config works well. You should use Match all to end the match block if you're using openssh 6.5p1 or above. Example:

PasswordAuthentication no
Match User root
PasswordAuthentication yes
Match all
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5
  • It didn't work for me...
    – Dimitrios
    Commented May 23, 2019 at 10:28
  • 2
    "Match all" did the trick. Thank you. Without "Match all" sshd fails to start.
    – Vladimir Kondratyev
    Commented Oct 10, 2019 at 20:24
  • This does not work on Ubuntu 20.04.
    – UltimaWeapon
    Commented Jun 16, 2020 at 17:13
  • 1
    It is working now after putting in /etc/ssh/sshd_config instead of /etc/ssh/sshd_config.d.
    – UltimaWeapon
    Commented Jun 16, 2020 at 17:22
  • 1
    "Match all" made it work for me. Without "Match all" in the end, the ssh and sshd services were failing to restart.
    – TheHat
    Commented May 17, 2021 at 9:27
4

Due to some security reason, you may require to block certain user SSH access to Linux box.

Edit the sshd_config file, the location will sometimes be different depending on Linux distribution, but it’s usually in /etc/ssh/.

Open the file up while logged on as root:

# vi /etc/ssh/sshd_config

Insert a line to end of the config file:-

DenyUsers username1 username2 username3 username4

Save it and restart SSH services. Basically username1, username2, username3 & username4 SSH login is disallowed.

Run below command to restart the same:-

# systemctl restart sshd

The requirement has been done. Please take the ssh from that users and your will get error "Access Denied"

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1
  • 1
    The question was about disabling password login (but keeping login with key authentication).
    – Gerald Schneider
    Commented May 7, 2019 at 6:57
2

There are a few ways that you can do this - first, you could concievably run a second sshd daemon on a different port with different config - its a bit of a hack, but with some chroot work it should work just fine.

Also, you could allow password authentication, but lock the passwords for all but the one user. The users with locked passwords will still be able to authenticate with public keys.

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2

The order of config-statements counts ... my solution to the file

/etc/ssh/sshd_config:

Match User <username> 
PasswordAuthentication yes
Match User all
PasswordAuthentication no
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1
0

you can simply go to /etc/ssh/sshd_config file and add a line To allow --> AllowUsers user1 To Deny ---> DenyUsers user2

we can allow/deny login for a particular set of hosts using the hosts.allow or hosts.deny files located in /etc folder

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