I got an idea to use users password and a local key to decrypt a dm-crypt partition with user home directory (and to mount it as a home).
But here is a problem: how can I get such script to be executed? It should be executed after successful authorization but before actual login, and it should have access to freshly inputted password.
Does someone know where to put such script?
This is a pretty common problem with a simple solution -- you use pam module.
Here is one example:
https://wiki.archlinux.org/index.php/Dm-crypt/Mounting_at_login
i want to save the user's IP when he connects to it's home folder, this is because i'm a user in a server where my team has a folder where our public_html is located, but we use the same account, so i just want to register who connected.
So i want to make a script that triggers when a connection is made and save the user's IP into a hidden file.
But i don't know if i could leave running a script in background to do it, and How?
If you're a root on that machine, you can simply check the auth log / messages / journal / ... (depends on the distribution). By default sshd logs all you need already.
If you're not a root, then you'll have to keep in mind this will never be secure. You can do this in the user's bash profile, but:
Since it's running as the same user, whoever logs in can just change the file (you can't hide it)
Anyone can workaround the script by executing some other command instead of the shell (for example ssh user#host /some/command will not be logged)
It's not secret.
If that's ok with you, then you just need to add this to bashrc
echo "new connection at $(date) from ${SSH_CLIENT}" >> ~/your_connection_log
Different solution, which should've been the default actually. Most distributions provide login history which you can request for your account without root privileges.
Running last your_username should give you the details of last few logins which cannot be manipulated by the user. (the log can possibly be spammed with entries however)
Here are some details about my setup...
Current environment:
40+ *nix systems managed by 6 admins
Highly secure, closed network (no internet access)
Regularly audited (all account passwords must be changed every 90 days)
Current procedures:
Each administrator has a personal account with sudo access. These admin accounts are managed via Active Directory so password changes are not an issue
Root account is also active for specific circumstances (i.e. admin account is locked out)
When it comes time to change the root passwords, an admin will do so by SSHing into each system (40+)
I want to write a script to make the root password changing process more efficient and everything I've read indicates that the most secure way to go about it is by using public key authentication. So my question is: If I log in as root to SYSTEM_1 and set up the public/private key pairs between that system and SYSTEM_2, SYSTEM_3, etc, does that mean I will only be able to run the script from SYSTEM_1? Is this even a good idea security wise? Are there any other ways to script this that I am missing?
You can use RSA Authentication and expect script
Let's say you are executing expect script on system 1, create public-private key pair and store public key on all the other systems you have to login (system 2.....n)
Now you wont need a password when you ssh into those system.
Now you can use expect script to change password for either root or any other user.
NOTE : usually expect interpreter is at /usr/bin/expect
you can find this my doing "whereis expect"
I hope it helps.
Try to use this algorithm and post your results.
Let's say I have a user "appuser" on a linux system with a number of public keys set up in their authorized_keys file where several different people can log in as "appuser".
When I log in using my private key that is linked to my public key, is what I do as the "appuser" traceable back to me? (I want it to be). If the activity is not traceable back to the identity of the user that logged in as app user, is there a way to make it traceable back to that identity?
The authorized_keys file allows for some options, including 'command' which will call a program or script you can write. I haven't tried this, but you might be able to perform whatever actions you need to in the script and then exec bash (or your shell of choice).
Another way you can match logins with keys is to turn LogLevel in sshd_config to VERBOSE and grep /var/log/secure (or whatever AUTHPRIV messages are going to) for 'Found matching .* key'. You can run the key found in the 'Found matching' line through 'ssh-keygen -l -f' which will dump the matching entry in authorized_keys.
I have a remote server to which I login using ssh. Is there a way to be notified through email (using a bash script) when someone changes the user password using passwd including the new password?
I am guessing it has to do with /etc/pam/passwd, but not entirely sure what the trigger and flags should be.
This would be useful if for example I give my access to a "friend" and they decide to lock me out of my account. Of course I could create a new account for them etc, but this is more of a "it should be possible" task rather than a practical one.
First, a Dope Slap
There's a rule that this question reminds me of... What is it? Oh yeah...
NEVER SHARE YOUR PASSWORDS WITH ANYONE!
Which also goes well with the rule.
NEVER SEND SOMETHING SECRET THROUGH EMAIL!
Sorry for the shouting. There's a rule in security that the likelihood a secret will get out is the square of the number of people who know it. My corollary is:
if ( people_who_know_secret > 1 ) {
It ain't a secret any more
}
In Unix, even the system administrator, the all powerful root, doesn't know your password.
Even worse, you want to email your password. Email is far from secure. It's normally just plain text sent over the Aether where anyone who's a wee bit curious can peek at it.
Method One: Allowing Users to use SSH without Knowing Your Password
Since you're using SSH, you should know that SSH has an alternate mechanism for verifying a user called Private/Public keys. It varies from system to system, but what you do is create a public/private key pair. You share your public key with the system you want to log into, but keep your private key private.
Once the remote machine has your public key, you can log into that system via ssh without knowing the password of that system.
The exact mechanism varies from machine to machine and it doesn't help that there are two different ssh protocols, so getting it to work will vary from system to system. On Linux and Macs, you generate your public/private key pair through the ssh-keygen command.
By default, ssh-keygen will produce a file called $HOME/.ssh/id_rsa.pub and $HOME/.ssh/id_rsa. The first one is your public key. You run ssh-keygen on both your machine and the machine you want to log into.
On the machine you're logging into, create a file called $HOME/.ssh/authorized_keys, and copy and paste your public key into this file. Have your friend also send you his public key, and paste that into the file too. Each public key will take up one line in the file.
If everything works, both you and your friend can use ssh to log into that remote machine without being asked for a password. This is very secure since your public key has to match your corresponding private key. If it doesn't you can't log in. That means even if other popel find your public key, they won't be able to log into that remote system.
Both you and your friend can log into that system without worrying about sharing a password.
Method Two: A Better Solution: Using SUDO
The other way to do this is to use sudo to allow your friend to act as you in certain respects. Sudo has a few advantages over actually sharing the account:
All use of SUDO is logged, so you have traceability. If something goes wrong, you know who to blame.
You can limit what people can do as SUDO. For example, your friend has to run a particular command as you, and nothing else. In this case, you can specify in the /etc/sudoers file that your friend can only run that one particular command. You can even specify if your friend can simply run the command, or require your friend to enter their password in order to run that command.
On Ubuntu Linux and on Macintoshes, the root password is locked, so you cannot log in as root. If you need to do something as root, you set yourself up as an administrator (I believe by putting yourself in the wheel group) and then using sudo to run required administrator functions.
The big disadvantage of Sudo is that it's more complex to setup and requires administrator access on the machine.
Try setting up public/private keys using SSH. It might take some tweaking to get it to work, but once it works, it's beautiful. Even better, you can run remote commands and use sep to copy files from one machine to the other -- all without the password prompt. This means that you can write shell scripts to do your work for you.
By the way, a sneaky trick is to set your remote shell to /bin/false. That way, you can't log into that system -- even using ssh, but you can run remote commands using ssh and use sep to copy files back and forth between systems.
Personal passwords are only supposed to be known by the user themselves. Not even the root user is supposed to know them, which is why they are stored encrypted. Of course, the root user has sufficient access to decrypt them, but the principle is the same.
If you are giving your "friend" access, them assign them proper privileges! Do not make them a root user, and you shouldn't be a root user either. Then you're "friend" won't have access to change your password, let along muck about in areas they aren't supposed to be in.
If you absolutely must monitor the passwd and shadow files, install iwatch. Then set it to watch the /etc/passwd and /etc/shadow files. If they change, it runs a script that decrypts the file and emails someone. If you keep a copy to diff against, you'll even know who changed. You should probably also gpg the email, so that it does not go over the internet in plain text, since it has everyone's password in it. Please note that any other users on the system will be upset by the dystopian world they find themselves in.
Just because root is the law of the land does not mean we want to be living in 1984.
Try some kind of:
alias passwd='passwd && echo 'Alert! Alert! Alert!' | mail -s 'pass change' alert#example.com'
Should be enough for you:)
Another possible solutions for those, who think, that alias is too mainstream)) :
1) You could make a cron job, that will be checking your /etc/shadow file every, for example, minute, and when the file changes, it will send you an alert-email. The easiest way here, I think, will be making md5 checksum
2) You can move /usr/bin/passwd to /usr/bin/passwd.sys and make a script with /usr/bin/passwd.sys && echo 'Alert! Alert! Alert!' | mail -s 'pass change' on it's place. And yes, this way is also could be discovered be the user and scrubed round:)