Lab 33.1 - changes to /etc/pam.d/sshd don't work on Ubuntu
I see this has been mentioned before but I just want to let you know it's still a problem.
On Ubuntu 18.04, if you add the lines to /etc/pam.d/sshd to try and lock out users after 3 failed login attempts:
auth required pam_tally2.so deny=3 onerr=fail account required pam_tally2.so
It has no effect, users can still try to log in as many times as they want. pam_tally2 doesn't seem to record anything.
➜ ~ ssh rocky@localhost rocky@localhost's password: Permission denied, please try again. rocky@localhost's password: Permission denied, please try again. rocky@localhost's password: rocky@localhost: Permission denied (publickey,password). ➜ ~ sudo pam_tally2 -u rocky Login Failures Latest failure From rocky 0 ➜ ~ ssh rocky@localhost rocky@localhost's password: Welcome to Ubuntu 18.04.2 LTS (GNU/Linux 4.15.0-52-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage ....
I gather from this AskUbuntu thread maybe it's something quirky about Ubuntu? I'm not sure how to make it work though.
Comments
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Hi @ronniegane ,
I'll do a test case on Ubuntu 18.10 and I'll let you know of my findings as soon as I can.
Regards,
Luis.0 -
Hi @ronniegane ,
I was able to reproduce the issue on Ubuntu 18.10. I'm working on this and I'll provide you an update as soon as I have a fix.
Regards,
Luis.0 -
Hi @ronniegane ,
I was able to get it working. Please follow these steps:
1.- Edit file /etc/pam.d/common-auth , and put the lines at the beginning of the file:
auth required pam_tally2.so file=/var/log/tallylog onerr=fail deny=3
account required pam_tally2.soNote: remove these lines from any other file under /etc/pam.d/* .
2.- Try an ssh connection and fail once. Then, before trying again, check as root if pam_tally2 is getting the failure. You should see the following:
root@ubuntu-18:~# pam_tally2 -u luis
Login Failures Latest failure From
luis 1 07/04/19 22:39:04 127.0.0.1Note: change with your own user.
3.- Fail for second time in the ssh connection and see in another window if it's getting to pam_tally2.
root@ubuntu-18:~# pam_tally2 -u luis
Login Failures Latest failure From
luis 2 07/04/19 22:40:47 127.0.0.14.- Fail for third time and check the count again:
root@ubuntu-18:~# pam_tally2 -u luis
Login Failures Latest failure From
luis 3 07/04/19 22:41:47 127.0.0.15.- Now try entering the right password. You should not be able to connect.
luis@ubuntu-18:~$ ssh -l luis localhost
luis@localhost's password:
Permission denied, please try again.
luis@localhost's password:So, in short terms, it's working. It should give an error like "the account is locked" anyway, but I'm not getting it.
Regards,
Luis.0 -
Here are a couple things to try:
1/ The auth line must be before "common-auth" in the /etc/pam/sshd file, I insert it as the first line in the file.
2/ A bad password of does not count, type anything in as a password. With one bad password entered the command "pam_tally2 -u student" should have an error recorded.
3/ pam_tally2 no longer gives any type of failure other than permission denied.
4/ The account line to reset the pam_tally2 counter is no longer necessary. A successful login will reset the counter.I have used this in Ubuntu 16.04 ->19.10
Regards Lee
0 -
Sorry for the duplication of information, I didn't refresh the screen before replying.
One key element is that the pam_tally2 auth line comes before pam_unix.so as pam_unix.so can exit the authentication test sequence before pam_tally2 is called. Pam_tally 2 can go in either sshd or common-auth. If it is in common-auth then it may impact more than just ssh logins. Putting the pam_tally2 test in the pam/sshd file will affect only ssh connections.
Going for coffee now, Lee
0
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