Pluggable Authentication Modules handle authentication tasks of applications or services running on the system.

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52
votes
3answers
13k views

Why is there a big delay after entering a wrong password?

I notice a weird (well, according to me) thing about passwords. For example, if I type an incorrect password during login, there will be a few seconds' delay before the system tells me so. When I try ...
19
votes
2answers
5k views

How does one change the delay that occurs after entering an incorrect password?

After entering an incorrect password at a login prompt, there s an approximately 3-second delay. How can I change that on a Linux system with PAM?
18
votes
3answers
2k views

How to prevent shutdown when an SSH user is logged in?

I'm administrating a networked environment and I had an interesting situation arise yesterday. When a host is required to shutdown by a regular user, it refuses to do so if other users are logged in ...
12
votes
2answers
4k views

How do I force a user to change a password at the first time login using ssh?

I'm trying to force a newly created user to change a password at the first time login using ssh. For security reasons I want to give him a secure password until he logs in for the first time. I did ...
12
votes
4answers
818 views

Groups differ from the local ones when logging in remotely

We store our users in LDAP, alongside some groups that have meaning across different systems (organizational roles including wheel). There are also groups local to workstations, e.g. audio or video ...
9
votes
2answers
224 views

How to automatically enter sudo's grace period upon CLI login?

What I would like to do is be able to login and sudo commands immediately without entering a password again. It is very redundant to type my password twice in a row when I need to login and run a ...
8
votes
2answers
18k views

Effect of entries in /etc/securetty

By default on RHEL 5.5 I have [deuberger@saleen trunk]$ sudo cat /etc/securetty console vc/1 vc/2 vc/3 vc/4 vc/5 vc/6 vc/7 vc/8 vc/9 vc/10 vc/11 tty1 tty2 tty3 tty4 tty5 tty6 tty7 tty8 tty9 tty10 ...
8
votes
1answer
102 views

How to add additional steps to login?

What I would like to achieve is an interactive program that runs either before or after asking the user for the password, but won't handle over the access to the computer unless it exited with ...
7
votes
5answers
28k views

Program for decrypt linux shadow file

Is there any program or script available for decrypt Linux shadow file ?
7
votes
3answers
9k views

Allow user1 to “su - user2” without password

I need to allow user martin to switch to user martin-test without password su - martin-test I think this can be configured in /etc/pam.d/su. There are already some lines in that file which can be ...
7
votes
1answer
786 views

What steps does the system go through when handling an SSH connection?

What steps does the system go through when handling an SSH connection? We try to log in via ssh sshd starts pam and pam module to authenticate us Depending on pam configuration, we need to provide ...
7
votes
4answers
1k views

How to set up two-factor authentication with OTP on FreeBSD?

I have a FreeBSD hosted server that I like to be able to get to from anywhere. Normally I use SSH publickey to log in, or if I don't have my SSH private key available then I might use regular password ...
7
votes
3answers
182 views

Restrict the times a user is allowed to log in

We have several Backbox 3.13 systems built on Ubuntu 12.04. One of my teenagers does not understand the concept of this thing called "sleep" and tends to get up to play on the computer. I'm trying to ...
6
votes
4answers
2k views

Is it possible to change password database file(/etc/passwd) in linux?

Is it possible to change password database file(/etc/passwd) to some other file. How does this authentication mechanism work internally ? Does it depend on pam ?
6
votes
1answer
4k views

What happens when your password expires and you're using key authentication?

on one of the boxes I don't control at work I use ssh keys to log in. Our passwords are set to expire after a few months. What happens if I don't reset my password and it expires? will I still be able ...
6
votes
4answers
3k views

SSH authentication: either SSH keys or one time password

I have an Ubuntu 10.04 Linux server that I normally ssh into (from my home machine) using ssh key authentication. However, sometimes I need to ssh remotely from potentially insecure machines (like ...
6
votes
3answers
68 views

different passwords depending on plugged-in devices

I would like to have different passwords for my account(s): When (e.g.) a certain USB stick is plugged in then an easy password is to be used. The idea is: If I leave my computer then I take the stick ...
6
votes
1answer
303 views

When running 'su - username', pam_group doesn't add additional groups from /etc/security/group.conf but sshd login does?

I am having trouble determining why su doesn't behave as the PAM configuration would imply. In short, using su to become another user should load secondary groups according to PAM configuration, but ...
6
votes
1answer
518 views

First sudo always slow

The first sudo I enter on my Ubuntu 14.04 server is always slow. The password prompt displays immediately, but after I press enter it takes about 10-15 seconds until the output is printed. All sudo ...
6
votes
1answer
1k views

2 Factor Authentication in SSH using public key and PAM

I'm trying to setup 2 Factor Authentication. I want the user to login successfully if: The public private/public key matches (authentication method: publickey) or the password is correct My pam ...
6
votes
1answer
123 views

Send only one warning when the private key is not available

For added security, I would like to require a private key to use sudo on my Ubuntu Server box. I've added private key authentication for sudo as described at ...
6
votes
1answer
723 views

Default umask 077 not applied at session start

I cannot get the default umask for a session to be 0077. I have edited /etc/login.defs and set the value to 077 there: UMASK 077 Also I've made sure the following entry exists in ...
6
votes
1answer
1k views

How to make a system lock when the USB pendrive with authentication key is removed?

Say, I have USB drive authentication up and working. So far, so hoopy. But now I want to take the next step, which is locking the machine when I eject the medium. I know there is udev I can script, ...
6
votes
1answer
578 views

Backing up and restoring a system user account

How would I go about completely backing up a user account and restoring it on a new system? The Home directory is just 'copy-and-paste'. But then what about things like the account password; and its ...
5
votes
4answers
364 views

Howto find and move a text line inside a file?

I need to change a text line position inside a file; from one line position to another one, underneath a defined text. For example, I have the following text block (on /etc/pam.d/system-auth file) ...
5
votes
1answer
1k views

Escape hash mark (#) in /etc/environment

I am adding an env variable to /etc/environment but because the variable value contains # sign, string is striped. MYSQL_PWD="something#no" Now if I do env above code yields MYSQL_PWD=something. ...
5
votes
1answer
860 views

Custom PAM modules and security considerations

I am writing my own PAM module that will be part of an application that I am developing, but I'm not sure exactly where to put it. My module basically does network-level authentication (with other ...
5
votes
2answers
327 views

PAM - required and sufficient control flag

I'm studying PAM, and I'm a bit clueless about the meaning of some combination of control flags. From the Red Hat documentation we have: *required failure of such a PAM will ultimately lead to the ...
5
votes
1answer
4k views

Preventing `passwd` for asking for the local password

I have setup the sever to only use LDAP for authentication by using authconfig-tui. Everything works well but, when I run passwd, I get two prompts for a password: [beamin@rhel6-test-server1 ~]$ ...
5
votes
1answer
1k views

Allow su without password for users in a particular Active Directory group when using pam_winbind

I know on my Gentoo system, the /etc/pam.d/su file comes with the following commented out: auth sufficient pam_wheel.so use_uid trust Which allows a user to su to root without a password as ...
4
votes
5answers
21k views

vsftpd fails pam authentication

Moving a tried-and-true vsftpd configuration onto a new server with Fedora 16, I ran into a problem. All seems to go as it should, but user authentication fails. I cannot find any entry in any log ...
4
votes
6answers
1k views

Identity Management with ActiveDirectory

What is the best, or most reliable, way to manage my Unix/Linux user accounts with ActiveDirectory? Or, is this even feasible?
4
votes
2answers
9k views

Avoid “Authentication token manipulation error” on password change

I'm implementing a security policy that will force the users to introduce stricter passwords when they change their own: The /etc/pam.d/passwd configuration file is: #%PAM-1.0 auth include ...
4
votes
1answer
30k views

How to lock users after 5 unsuccessful login tries?

How to lock users after 5 unsuccessful login tries? I gathered a few distributions/versions to how to do it, but I can't test it. RHEL4: by adding the: auth required ...
4
votes
1answer
3k views

How to have pam_exec run the script as the current user?

I need to run a script, when the session is opened, as the user who's opening the session. I have added in /etc/pam.d/common-session : session optional pam_exec.so ...
4
votes
2answers
2k views

What are the reasons Slackware still refuses to include PAM?

I know that Pat Volkerding didn't include PAM back in the day when it was considered by some to be messy or inconsistent, although that doesn't really seem to be the case today with PAM being ...
4
votes
3answers
2k views

Restrict ssh login from LDAP to users who have a /home directory

I have an Apache server (RHEL 6) hosting multiple user web pages which currently is connected to my Active Directory environment to authenticate users. The server is used to automatically host content ...
4
votes
1answer
277 views

Confused about PAM configuration stanza and the roles of the control-flag parameters

I just begun studying for the RHCE. While on the topic of PAM configuration, I was a little perplexed with this stanza from /etc/pam.d/system-auth: auth required pam_env.so auth ...
4
votes
2answers
5k views

Can I create a local only guest account?

Is it possible to create a "guest" account in Linux? by "guest" account I mean an account that does not require a password to log in graphically. I want this account for when people come over and are ...
4
votes
1answer
2k views

Automatically mount encrypted home folder on login

I'm looking into encrypting my home folder with Truecrypt, and mounting it after I've logged in, which should be pretty straightforward. However, it occurred to me that it should be theoretically ...
4
votes
1answer
140 views

Why libpam-systemd run interactively on apt upgrade, even when specified force-confdef/force-confold

I upgrade my packages using aptitude, specifying the apt options --force-confdef and --force-confold. This generally works, but the package libpam-systemd (204-5ubuntu20.8, on Ubuntu 14.04) still ...
3
votes
2answers
4k views

Ubuntu password policy

I want to set the system-wide password policy on an Ubuntu 12.04 LTS server. Googling around, a lot of people point to this (very old) document: ...
3
votes
2answers
869 views

allow only specific users to login via sshd, but refuse connect to non-listed users

I'm running a CentOS server (7.0) and I'd like to login via sshd as a user, not root. So I set PermitRootLogin no in the config file and su - after login. I've received lots of hacking activities and ...
3
votes
1answer
474 views

pam: action on (unsuccessful) login

I know how to execute an action on login, by adding a line to /etc/profile. But that only gets executed, if the login was successful. I would like to have action executed even when login fails. For ...
3
votes
1answer
984 views

Setting ulimits without PAM

How to do that? Without PAM on my GNU/Linux OS the number of open files is 1024 by default and cannot be raised above 4096 (via ulimit -n NNNN command) despiting what is written in ...
3
votes
2answers
37 views

How to stop sudo PAM messages in auth.log for a specific user?

I am using Zabbix for monitoring my environment and zabbix_agentd executes as user zabbix one custom script every 60 seconds; it uses sudo to run this script as root. In /var/log/auth.log I see every ...
3
votes
1answer
861 views

Is /sbin/sulogin safe?

Lately my machine's authentication system broke twice: once because I messed up with PAM/LDAP and the other one because I messed up with /etc/passwd or /etc/shadow. In order to recover things I had ...
3
votes
1answer
347 views

Run Script at fail login attempt?

Lately, I've been trying to create a Bash script to capture a webcam photo when a fail attempt to login is registered. First of all, I found 2 guides related to this (links at the end), they explained ...
3
votes
1answer
66 views

How to lock users with PAM in Scientific Linux 5.5? [duplicate]

I need to lock the users that are trying to log in via SSHD after 5 unsuccessful login tries. I already googled for it, but I just can see it working: root@server:~# faillog -u testuser Login ...
3
votes
1answer
384 views

Configure SCP access for login without a local account

Can I set up accounts that can do SCP that are NOT local users (i.e. users with an entry in /etc/passwd)? I've tried googling for SCP "without PAM authentication" or alternative authenication for sshd ...