ssh with rsa key asks for password

Question

I have a server with Ubuntu 14.04 x64 operation system.

Part of my sshd_config file (entire file):

Port 2202
Protocol 2
PermitRootLogin without-password
StrictModes yes
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile      /etc/ssh/keys/%u/authorized_keys
RhostsRSAAuthentication no
PermitEmptyPasswords no
ChallengeResponseAuthentication no
#PasswordAuthentication yes
UsePAM yes

In folder /etc/ssh/keys each system user has its own folder with authorized_keys file:

ls -l /etc/ssh/keys
drw------- 2 test.com  test.com   4096 Nov 20 06:53 test.com
drw------- 2 root      root       4096 Nov 20 02:29 root

The permissions of these authorized_keys files are correct:

ls -l /etc/ssh/keys/*
/etc/ssh/keys/test.com:
total 4
-r-------- 1 test.com test.com 960 Nov 20 07:17 authorized_keys

/etc/ssh/keys/root:
total 4
-r-------- 1 root root 395 Nov 20 02:29 authorized_keys

I have the same public id_rsa in root's and test.com's authorized_keys file.
I can login with root through ssh, but with test.com I am prompted for password.

Here is the debug info when trying to connect with test.com user:

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/Ivan/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /Users/Ivan/.ssh/id_dsa
debug1: Next authentication method: password

When I try to login with root I succeed:

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/Ivan/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: Authentication succeeded (publickey).

I have Googled a lot of things. Couldn't find anything that solves my problem.

I have a script which creates system users using useradd command and these users are without passwords by default. I've found that system users without password may not login through ssh so I added password to test.com user. Didn't work.

I saw that UsePAM yes may be a problem. I set it to UsePAM no. Didn't work.

And yes, I did service ssh restart after each change to the sshd_config file.

I think I've tried everything and now I am clueless.

Any help will be appreciated!

Answer 1

I had the same issue, and found that SELinux was preventing read access to /usr/bin/sshd when trying to remote in for some users. Typically for users that don't have a home folder under /home/. You can run

cat /var/log/messages | grep -i ssh

on the target server, and you should see a similar line indicating the error:

<Date/Time> <hostname> python: SELinux is preventing /usr/sbin/sshd from read access on the file authorized_keys.#012#012*****  Plugin catchall (100. confidence) suggests   **************************#012#012
If you believe that sshd should be allowed read access on the authorized_keys file by default.#012Then you should report this as a bug.#012
You can generate a local policy module to allow this access.#012Do#012allow this access for now by executing:#012# 
ausearch -c 'sshd' --raw | audit2allow -M my-sshd#012# semodule -i my-sshd.pp#012`

You can edit the SELinux permissions to allow ssh connections or simply turn it off (less secure) to get around this.

Answer 2

sshd is very picky when it comes to permissions!

It seems that the directory permissions of /etc/ssh/keys/test.com/ are wrong! Currently the directory is read/write but may not be entered. chmod u+x /etc/ssh/keys/test.com/ && chmod o+rx /etc/ssh/keys should solve your issue. While root may enter the directory, I assume that sshd checks the octal permissions to be 0700 or 0755 + 0600 for the authorized_keys file itself. Especially, when StrictMode yes.

Without access permission to the directory, and proper permissions the authorized_keys file cannot be read or is being ignored by sshd out of security concerns.

Answer 3

ls -l /etc/ssh/keys
drw------- 2 test.com  test.com   4096 Nov 20 06:53 test.com
drw------- 2 root      root       4096 Nov 20 02:29 root

No x permission to the directory = no permission to actually use anything inside the directory. With these permissions, sshd would be able to get the directory listing of /etc/ssh/keys/test.com/ but not able to access the contents of /etc/ssh/keys/test.com/authorized_keys.

For root, it works because root can access anything.