dilemma what to use c++ or script for demon process Post: 302285432

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Top Forums Shell Programming and Scripting dilemma what to use c++ or script for demon process Post 302285432 by ddreggors on Monday 9th of February 2009 02:00:10 AM

02-09-2009

Registered User

We use a similar process to manage several hundred servers. We have taken 3 approaches over the last 3 years.

1. Daemon (c++) that listens on a port and runs the passed args as command.
2. Bash script using ssh to issue command using ssh keys to make this a password-less process.
3. Bash script using expect.

Using a compiled c++ app running as a listening daemon was great for ease but very bad for security. We had to add in the ability to only allow admin IP's set in a conf file and in the end realized that this was a real bad security risk even with IP based ACL's.

The second method, worked well also. Again having ssh keys laying around on a file system was not the best idea either.This method was also ultimately aborted. PCI compliance prohibited usage of both the above.

In the end we agreed that using expect was less of a risk. We can use bash to script the things we need and use expect (inline in the bash) to handle the ssh login and pass the command and exit.

We use the read command to take in user and password as the script runs and store the user/pass in a variable and then pass to expect as needed.

While this is what we use it may or may not be your best approach. This all boils down to YOUR needs and requirements.

Also note that using read to store user and pass and then passing to expect will allow a non-admin to see the password if they run the "ps" command. This is only possible for a split second while expect spawns the ssh command to the remote host and is FAR better than having an ssh key or worse a user/password hard coded in a file somewhere.

The c++ approach will expose a port that can be seen and runs all the time. It will only take minutes for a good hacker to target that port. If that daemon is running as root then you are in real jeopardy at that point of having your whole system compromised! To make matters worse if (as you say) you have multiple machines using this daemon then all are at risk of this compromise.

Not sure if you have heard of webmin, but many also use webmin for this purpose as webmin allows you to "cluster" groups of machines and send commands, update packages/applications, add/update/delete users, edit configurations, and way more of all machines you have added to webmin console at once.

Webmin is quite mature and has very good security tools (SSL login, and user/host based ACL's as well).

EDIT:

Also, another good thing to use, no matter which method you decide to use. If at all possibe, create a shared location (NFS?) to store scripts that are for admin type processes. Then all you have to do is cycle through the list of hosts and all the command from the common nfs location.

Example:

Create an NFS export on your NFS server.
On hosts 1-4 have them all mount the share as "/nfs1"

Place admin scripts in "/nfs1/admin" (/nfs1/admin/update_users.sh or whatever).

Now hosts 1-4 can all use the script from the same location so all you have to do is this:

Code:

HOSTS="host1 host2 host2 host4" 
# This can also be stored in a table in a database and retrived via sql so you do not have to change all files every time you add a host!

for SRV in $HOSTS
do
    ssh $SRV /nfs1/admin/update_users.sh
done

Of course this is assuming an ssh connection and NOT a daemon, and does not show any expect examples but you get the idea.

Last edited by ddreggors; 02-09-2009 at 03:17 AM..

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LEARN ABOUT DEBIAN

passmass

PASSMASS(1)						      General Commands Manual						       PASSMASS(1)

NAME

       passmass - change password on multiple machines

SYNOPSIS

       passmass [ host1 host2 host3 ...  ]

INTRODUCTION

       Passmass  changes a password on multiple machines.  If you have accounts on several machines that do not share password databases, Passmass
       can help you keep them all in sync.  This, in turn, will make it easier to change them more frequently.

       When Passmass runs, it asks you for the old and new passwords.  (If you are changing root passwords and have equivalencing, the	old  pass-
       word is not used and may be omitted.)

       Passmass  understands  the  "usual"  conventions.   Additional  arguments may be used for tuning.  They affect all hosts which follow until
       another argument overrides it.  For example, if you are known as "libes" on host1 and host2, but "don" on host3, you would say:

	    passmass host1 host2 -user don host3

       Arguments are:

	      -user
		  User whose password will be changed.	By default, the current user is used.

	      -rlogin
		  Use rlogin to access host.  (default)

	      -slogin
		  Use slogin to access host.

	      -ssh
		  Use ssh to access host.

	      -telnet
		  Use telnet to access host.

	      -program

		  Next argument is a program to run to set the password.  Default is "passwd".	Other  common  choices	are  "yppasswd"  and  "set
		  passwd"  (e.g.,  VMS hosts).	A program name such as "password fred" can be used to create entries for new accounts (when run as
		  root).

	      -prompt
		  Next argument is a prompt suffix pattern.  This allows the script to know when the shell is prompting.  The default is "# "  for
		  root and "% " for non-root accounts.

	      -timeout
		  Next argument is the number of seconds to wait for responses.  Default is 30 but some systems can be much slower logging in.

	      -su

		  Next	argument is 1 or 0.  If 1, you are additionally prompted for a root password which is used to su after logging in.  root's
		  password is changed rather than the user's.  This is useful for hosts which do not allow root to log in.

HOW TO USE

       The best way to run Passmass is to put the command in a one-line shell script or alias.	Whenever you get a new account on a  new  machine,
       add the appropriate arguments to the command.  Then run it whenever you want to change your passwords on all the hosts.

CAVEATS

       Using  the  same  password on multiple hosts carries risks.  In particular, if the password can be stolen, then all of your accounts are at
       risk.  Thus, you should not use Passmass in situations where your password is visible, such as across a network which hackers are known	to
       eavesdrop.

       On  the	other  hand,  if you have enough accounts with different passwords, you may end up writing them down somewhere - and that can be a
       security problem.  Funny story: my college roommate had an 11"x13" piece of paper on which he had listed accounts and passwords all  across
       the  Internet.	This  was  several  years worth of careful work and he carried it with him everywhere he went.	Well one day, he forgot to
       remove it from his jeans, and we found a perfectly blank sheet of paper when we took out the wash the following day!

SEE ALSO

       "Exploring Expect: A Tcl-Based Toolkit for Automating Interactive Programs" by Don Libes, O'Reilly and Associates, January 1995.

AUTHOR

       Don Libes, National Institute of Standards and Technology

								  7 October 1993						       PASSMASS(1)