up vote 16 down vote favorite
5

Is it possible to disable PASSWORD SSH access to user but to allow Key authentication on a per user basis ? I mean, I have a userA whom I don't want to give Password based access BUT I wan't him to only use key authentication to access the server(s). Thanks

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Possible duplicate of how to disable SSH login with password for some users? – Josip Rodin Apr 4 '17 at 12:41
up vote 44 down vote accepted

You can add "Match" sections to match on particular users or groups at the bottom of sshd_config, like:

Match user stew
PasswordAuthentication no

or

Match group dumbusers
PasswordAuthentication no
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7  
I would avoid indenting as it suggests that only the indented lines are affected by Match when in reality, all configuration is affected until the next Match directive. Could be confusing to someone not familiar with with the syntax. – Michael Mior Dec 29 '13 at 7:25
1  
@MichaelMior is there a way to "EndMatch"? – Nick T Feb 7 '17 at 20:16
2  
@NickT Match works up until the next Match or Host keyword. You could just use Match user *. – Michael Mior Feb 8 '17 at 13:05
up vote 4 down vote

Just lock the passwords of the users you don't want to log in with passwords:

usermod -L <user>

Then, place a valid public key in their .ssh/authorized_keys file and they will be only able to log in with the corresponding private key, but not with a password.

Note: This will break sudo unless the user has NOPASSWD: in their visudo entry

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8  
That also will break sudo. Perhaps not an issue in this case, but it bears mention. – EEAA♦ May 8 '12 at 15:25
    
Yes, that is true. I should have mentioned it. – Oliver May 8 '12 at 15:26
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Some OpenSSH setups (e.g. i think Ubuntu 14.04 in default config) do not let locked users in, not even via authorized_keys – Nils Toedtmann Sep 18 '14 at 12:38
    
@NilsToedtmann can you cite a source for verification? This would be very important to note in the answer, as well, if so. – Metagrapher Sep 23 '15 at 2:06
up vote -3 down vote

you should look into

/etc/ssh/sshd_config

I think what you're looking for is

PasswordAuthentication yes

change it to no and don't forget to restart sshd

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2  
I'm aware of this - this is a GLOBAL settings though - I want more granular option - that's why I said "per-user basis" - I want this only for some users (used for innercluster communication between the servers in the cluster) - not for all users – gyre May 8 '12 at 15:22
    
oh right, i'm sorry i didn't read it correctly then what @stew recommended is a way to go – alexus May 8 '12 at 15:57

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