How to automate kinit process to obtain TGT for Kerberos?

Question

I'm currently writing a puppet module to automate the process of joining RHEL servers to an AD domain, with support for Kerberos.

Currently, I have problems with automatically obtain and cache Kerberos ticket-granting ticket via kinit. If this were to be done manually, I would do this:

kinit [email protected]

This prompts for the AD user password, hence there is a problem with automate this.

How can I automate this? I've found some posts mentioning using kadmin to create a database with the AD users password in it, but I've had no luck.

Solution 1

Stupid me, you can simply use following command:

echo "password" | kinit aduser@REALM

Solution 2

While you can just hard-code the password into your automation, the more correct Kerberos way to do this is to create a keytab for the principal and then use that to authenticate. kinit supports authenticating from a keytab using the -k -t <keytab-path> options.

The primary advantage of a keytab is that it isolates the credentials in a separate file and can be used directly by various Kerberos software (so you don't have to add code to read a password from a separate file). It can also be created with standard commands (with an AD KDC, use ktpass). There are some more advantages if you had a Linux KDC, such as easily randomizing keys stored in the keytab rather than using a weaker password.

Solution 3

According to the man-page you might use:

kinit --password-file="~/my.secret" [email protected]

So you just might provide your password via a file.

Comments

[Dejan]

echo -n "$PASS" | kinit "$USER" do not output trailing newline

[Havnar]

Or print a poster with your password and hang it out! Storing your password in plain text is a no-no

[Dennis Jaheruddin]

Keytab definitely seems to be the way to go. If you generate this in kadmin, make sure to use the -norandkey flag in ktadd if you don't want to invalidate the existing password.

[Indranil Gayen]

does it work in windows ?

[Sam Morris]

FYI, --password-file= is available with the kinit command that comes as a part of Heimdal Kerberos. It's not available with MIT Kerberos' kinit command.