I've been trying to write a script that adds a non-root user. Is it possible to use variables and adduser to do it? I've tried just adduser bob and it works perfectly fine, so why does adduser $user return adduser: Only one or two names allowed.?
#!/bin/bash
read -p 'Do you want to add a non-root user? [y/N]' answer
case "${answer}" in
[yY]|[yY][eE][sS])
echo -e "What will the username be?"
read $user
adduser $user;;
[nN]|[nN][oO])
echo "Skipping";;
esac
Your problem is you are not adding anyone. In your script you have:
read $user
it should be
read user
Also note the correct command is useradd. adduser, if it exists, is generally just a link to useradd.
Related
I am trying to create a Shell script and (to avoid typing, furthermore ignoring security related issues for now) want to directly pass the password to the "sudo" command, e.g.,
pword="mypassword"
echo $pword | sudo -S whoami
This works just fine. But now when the command itself expects an input, this method seems to fail, e.g.,
echo $pword | sudo -S cat<<<"Hello"
This would lead to an 'incorrect password' error. Currently, my solution is to run a "dummy command" like in example one first, and use the fact that for the second command the system does not prompt for a password again. However, does anyone know a better solution to get it to work?
You can defer the activation of the "here document" (the <<< construct) by doing something like this:
echo $pw | sudo -S sh -c ' cat <<<"Hello" '
A better solution is to use sudo -A instead of sudo -S, after first defining a $SUDO_ASKPASS environment variable to refer to a program that will emit your password. Then you won't have to worry about competing for stdin with the rest of the command line. You should create that askpass program (it can be a shell script) to be readable, writable and executable only by yourself so that your password will be securely hidden inside the program.
The -v flag of sudo is also useful if you have just entered your password for the SSH connection, -v updates the cache and doesn't ask for a password again:
sudo -v -u UserName && bash -c 'cat <<<"Hello"'
In a shell script with sudo privileges, I'm trying to change another users password.
I tried sudo passwd username but didn't get anywhere.
You need to use the chpasswd command. You can try something like this:
echo "username:password" | sudo chpasswd
I used it many times. It worked for me.
We currently have several users that are using the admin user when logging into a server via SSH. They all have their own users but unfortunately they still occasionally use the admin one. We can lock this down of course and take action to make sure that user is never used, but I'm looking to see if there is a way to force each login to enter a reason why they are using that user, before they can login and access the server whenever they use the admin user.
This way we can have an easy way to compare access log files with employee names and the reason why they are using that user.
Any thoughts?
Here's what I would do.
Register everyone's ssh public key into admin user's authorized_keys. In each entry, set the environment EMPLOYEE to the employeename. This will require that PermitUserEnviroment be set to yes in /etc/ssh/sshd_config. A sample entry should look like below.
environment="EMPLOYEE=employee1" ssh-rsa AAAAB3NzaC1y.....EU88ovYKg4GfclWGCFYTuw8==
Now that we have an environment variable named EMPLOYEE, we can write a simple script to ask for the reason.
Create a file /etc/profile.d/reason.sh. The file does not need to be executable as it will be sourced.
if [[ $(whoami) = "admin" ]]; then
read -p "Please specify the reason for logging in as $USER user: " reason
if [ -z "$reason" ]; then
logout
fi
fi
Now you have $EMPLOYEE and $reason to log.
Here's a thought
#!/bin/bash
# if the user tries Ctrl+C to avoid this check
trap INT no_shell_for_you
no_shell_for_you() { exec /bin/false; }
read -p "Your username please: " username
if getent password "$username" >/dev/null 2>&1; then
echo "Welcome, $username"
# log $username somewhere
exec /bin/bash -l
else
no_shell_for_you
fi
Save that as ~admin_user/bin/get_real_user.sh
Add /full/path/to/admin_user/bin/get_real_user.sh to /etc/shells
Do sudo chsh -s /full/path/to/admin_user/bin/get_real_user.sh admin_user
This is untested. Test thoroughly before step 3.
I have created a shell script as follows.
username='root'
sudo -H -u "$username" bash 2<&0 << 'END_COMMAND'
useradd -m -s /bin/bash suhail
passwd suhail
mkdir ~/test
END_COMMAND
But i am getting the out put as follows when i trying to run this script file
user#uvais-desktop:~/ssp$ ./test
sudo: unable to resolve host uvais-desktop
Enter new UNIX password: Retype new UNIX password: Sorry, passwords do not match
passwd: Authentication token manipulation error
passwd: password unchanged
It is not prompting for password for the new user.Everything happened in a second. !!
Please help me if anyone could.
One problem is that you can't run passwd. It asks to write password twice which you can't do in the script. So you enter password once then for the second time you enter mkdir ~test, hence the message "Sorry, passwords do not match"
Instead of passwd suhail try:
echo suhail| passwd $username --stdin
I'm writing a UNIX shell function that is going to execute a command that will prompt the user for a password. I want to hard-code the password into the script and provide it to the command. I've tried piping the password into the command like this:
function() {
echo "password" | command
}
This may not work for some commands as the command may flush the input buffer before prompting for the password.
I've also tried redirecting standard input to a file containing the password like this, but that doesn't work either:
function() {
echo "password" > pass.tmp
command < pass.tmp
rm pass.tmp
}
I know that some commands allow for the password to be provided as an argument, but I'd rather go through standard input.
I'm looking for a quick and dirty way of piping a password into a command in bash.
How to use autoexpect to pipe a password into a command:
These steps are illustrated with an Ubuntu 12.10 desktop. The exact commands for your distribution may be slightly different.
This is dangerous because you risk exposing whatever password you use to anyone who can read the autoexpect script file.
DO NOT expose your root password or power user passwords by piping them through expect like this. Root kits WILL find this in an instant and your box is owned.
EXPECT spawns a process, reads text that comes in then sends text predefined in the script file.
Make sure you have expect and autoexpect installed:
sudo apt-get install expect
sudo apt-get install expect-dev
Read up on it:
man expect
man autoexpect
Go to your home directory:
cd /home/el
User el cannot chown a file to root and must enter a password:
touch testfile.txt
sudo chown root:root testfile.txt
[enter password to authorize the changing of the owner]
This is the password entry we want to automate. Restart the terminal to ensure that sudo asks us for the password again. Go to /home/el again and do this:
touch myfile.txt
autoexpect -f my_test_expect.exp sudo chown root:root myfile.txt
[enter password which authorizes the chown to root]
autoexpect done, file is my_test_expect.exp
You have created my_test_expect.exp file. Your super secret password is stored plaintext in this file. This should make you VERY uncomfortable. Mitigate some discomfort by restricting permissions and ownership as much as possible:
sudo chown el my_test_expect.exp //make el the owner.
sudo chmod 700 my_test_expect.exp //make file only readable by el.
You see these sorts of commands at the bottom of my_test_expect.exp:
set timeout -1
spawn sudo chown root:root myfile.txt
match_max 100000
expect -exact "\[sudo\] password for el: "
send -- "YourPasswordStoredInPlaintext\r"
expect eof
You will need to verify that the above expect commands are appropriate. If the autoexpect script is being overly sensitive or not sensitive enough then it will hang. In this case it's acceptable because the expect is waiting for text that will always arrive.
Run the expect script as user el:
expect my_test_expect.exp
spawn sudo chown root:root myfile.txt
[sudo] password for el:
The password contained in my_test_expect.exp was piped into a chown to root by user el. To see if the password was accepted, look at myfile.txt:
ls -l
-rw-r--r-- 1 root root 0 Dec 2 14:48 myfile.txt
It worked because it is root, and el never entered a password. If you expose your root, sudo, or power user password with this script, then acquiring root on your box will be easy. Such is the penalty for a security system that lets everybody in no questions asked.
Take a look at autoexpect (decent tutorial HERE). It's about as quick-and-dirty as you can get without resorting to trickery.
You can use the -S flag to read from std input. Find below an example:
function shutd()
{
echo "mySuperSecurePassword" | sudo -S shutdown -h now
}
Secure commands will not allow this, and rightly so, I'm afraid - it's a security hole you could drive a truck through.
If your command does not allow it using input redirection, or a command-line parameter, or a configuration file, then you're going to have to resort to serious trickery.
Some applications will actually open up /dev/tty to ensure you will have a hard time defeating security. You can get around them by temporarily taking over /dev/tty (creating your own as a pipe, for example) but this requires serious privileges and even it can be defeated.
with read
Here's an example that uses read to get the password and store it in the variable pass. Then, 7z uses the password to create an encrypted archive:
read -s -p "Enter password: " pass && 7z a archive.zip a_file -p"$pass"; unset pass
But be aware that the password can easily be sniffed.
Programs that prompt for passwords usually set the tty into "raw" mode, and read input directly from the tty. If you spawn the subprocess in a pty you can make that work. That is what Expect does...
Simply use :
echo "password" | sudo -S mount -t vfat /dev/sda1 /media/usb/;
if [ $? -eq 0 ]; then
echo -e '[ ok ] Usb key mounted'
else
echo -e '[warn] The USB key is not mounted'
fi
This code is working for me, and its in /etc/init.d/myscriptbash.sh
That's a really insecure idea, but:
Using the passwd command from within a shell script