Make Use of OBIEE’s Command Line Tools with Reduced Exposure of Plain Text Passwords

November 20th, 2013 by

Introduction

We all love a good commandline utility. It gives us that warm feeling of control and puts hairs on our chests. Either that, or it means we can script the heck out of a system, automate many processes, and concentrate on more important matters.

However, some of the OBIEE commandline utilities can’t be used in Production environments at many sites because they need the credentials for OBIEE stored in a plain-text file. Passwords in plain-text are bad, mmmm’kay?

Two of the utilities in particular that it is a shame that can’t be scripted up and deployed in Production because of this limitation are the Presentation Services Catalog Manager, and the Presentation Services Replication Agent. Both these perform very useful purposes, and what I want to share here is a way of invoking them more securely.

Caveat

IANAC : I Am Not A Cryptographer! Nor am I a trained security professional. Always consult a security expert for the final word on security matters.

The rationale behind developing the method described below is that some some sites will have a “No Plaintext Passwords” policy which flatout prevents the use of these OBIEE utilities. However, at the same sites the use of SSH keys to enable one server to connect to another automatically is permitted. On that basis, the key-based encryption for the OBIEE credentials may therefore be considered an acceptable risk. As per Culp’s 9th law of security administration, it’s all about striking the balance between enabling functionality and mitigating risk.

The method described below I believe is a bit more secure that plaintext credentials, but it is not totally secure. It uses key based encryption to secure the previously-plaintext credentials that the OBI utility requires. This is one step better than plaintext alone, but is still not perfect. If an attacker gained access to the machine they could still decrypt the file, because the key is held on the machine without a passphrase to protect it. The risk here is that we are using security by obscurity (because the OBIEE credentials are in an encrypted file it appears secure, even though the key is held locally), and like the emperor’s new clothes, if someone takes the time to look closely enough there is still a security vulnerability.

My final point on this caveat is that you should always bear in mind that if an attacker gains access to your OBIEE machine then they will almost certainly be able to do whatever they want regardless, including decrypting the weblogic superuser credentials or reseting it to a password of their own choosing.

Overview

Two new shiny tools I’ve acquired recently and am going to put to use here are GnuPG (gpg) and mkfifo. GPG provides key-based encryption and decryption and is available by default on common Linux distributions including Oracle Linux. mkfifo is also commonly available and is a utility that creates named pipes, enabling two unreleated processes to communicate. For a detailed description and advanced usage of named pipes, see here

Setting up a secure credentials file

This is a one-time set up activity. We create a key in gpg, and then encrypt the plain text credentials file using it.

The first step is to create a gpg key, using gpg --gen-key. You need to specify a “Real name” to associate with the key, I just used “obiee”. Make sure you don’t specify a passphrase (otherwise you’ll be back in the position of passing plain text credentials around when you use this script).

Once this is done, you can encrypt the credentials file you need for the utility. For example, the Catalog Manager credentials file has the format:

To encrypt it use gpg --encrypt

Now remove the plaintext password file

Using the secure credentials file

Once we have our encrypted credentials file we need a way of using it with the utility it is intended for. The main thing we’re doing is making sure we don’t expose the plaintext contents. We do this using the named pipes method:

In this example I am going to show how to use the secure credentials file with runcat.sh, the Catalog Manager utility, to purge the Presentation Services cache. However it should work absolutely fine with any utility that expects credentials passed to it in a file (or stdin).

There is a three step process:

  1. Create a named pipe with mkfifo. This appears on a disk listing with the p bit to indicate that it is a pipe. Access to it can be controlled by the same chmod process as a regular file. With a pipe, a process can request to consume from it, and anything that is passed to it by another process will go straight to the consuming process, in a FIFO fashion. What we’re doing through the use of a named pipe is ensuring that the plain text credentials are not visible in a plain text file on the disk.

  2. Invoke the OBIEE utility that we want to run. Where it expects the plaintext credentials file, we pass it the named pipe. The important bit here is that the utility will wait until it receives the input from the named pipe – so we call the utility with an ampersand so that it returns control whilst still running in the background

  3. Use gpg to decrypt the credentials file, and pass the decrypted contents to the named pipe. The OBIEE utility is already running and listening on the named pipe, so will receive (and remove from the pipe) the credentials as soon as they are passed from gpg.

The script that will do this is as follows:

Depending on the utility that you are invoking, you may need to customise this script. For example, if the utility reads the credentials file multiple times then using the named pipes method it will fail after the first read. Your option would be to read the credentials into the pipe multiple times (possibly a bit hacky), or land the plaintext credentials to disk and delete them after the utility complete (could be less secure if the delete doesn’t get invoked)

Using a secure credentials file for command line arguments

Whilst the sticking point that triggered this article was around utilities requiring whole files with credentials in, it is also common to see command line utilities that want a password passed as an argument to them. For example, nqcmd :

Let’s assume we’ve created an encrypted file containing “Password01” (using the gpg --encrypt method shown above) and saved it as password.gpg.
To invoke the utility and pass across the decrypted password, there’s no need for named pipes. Instead we can just use a normal (“unnamed”) pipe to send the output straight from gpg to the target utility (nqcmd in this example), via xargs:

Tip: xargs has a --interactive option that makes it a lot easier when developing piped commands such as the above

Limitations

Because there is no passphrase on the gpg key, a user who obtained access to the server would still be able to decrypt the credentials file. In many ways this is the same situation that would arise if a server was configured to use ssh-key authentication to carry out tasks or transfer files on another server.

Uses

Here are some of the utilities that the above now enables us to run more securely:

  • nqcmd is a mainstay of my OBIEE toolkit, being useful for performance testing, regression testing, aggregate building, and more. Using the method above, it’s now easy to avoid storing a plaintext password in a script that calls it.
  • Keeping the Presentation Catalog in sync on an OBIEE warm standby server, using Presentation Services Replication
  • Purging the Presentation Services Cache from the command line (with Catalog Manager, per the above example)
  • SampleApp comes with four excellent utilities that Oracle have provided, however all but one by default requires plaintext credentials. If you’ve not looked at the utilities closely yet, you should! You can see them in action in SampleApp itself, or get an idea of what they do looking at the SampleApp User Guide pages 14–17 or watching the YouTube video.

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