bash and konsole

So I've had lots of problems using a multi-tab xterminal, for the casual user I'm sure they'd not even notice them, or think I'm silly, but when you spend all day in a shell they become less so.

History

one of the big problems I've had is with history. see when you close a shell then it writes the history. well if you have 5 tabs open each with with a super long history they'll write those histories out in the order they close in. basically what happens is all the history saves at once so one of your open shells histories will be before another's and if each has like 50 entries it can be quite a way back. In fact I'm sure I've had it happen where parts of my history was lost. So what do you do? you have to separate them per tab. One way to do this is with gnu screen. I don't like screen's history because it records the output of the terminal as well as the command, so this wasn't a good solution for me. The solution is that each tab must have its own history file. Well how do we do that? before I get to it I have another problem.

PS1, umask, and default group

I also have a need to have different settings depending on what I'm working on. If I'm working on files that need to be read and written to by my web server they need to have a different group and umask. first I solved this by su - to a different user, then I solved it by having different bashrc's but neither fully solved the history problem.

howto do it

first you have to have one konsole profile for each of the different settings you need. so I have one for web development called webdev. Then you have to add an environment variable to it I'm going to call it KONSOLE_PROFILE and set that to whatever your profile is called. Neither name really matters so long as they don't conflict with others. Then you need to code your bashrc (or other shell to work with it). I have a shortened sample bashrc that you can use in a gist

iptables browsing samba shares

NOTE: this assumes that you've read my previous post on basic iptables setup on the desktop

So I just spent the longest time trying to determine what ports I needed to browse and use samba shares. The sad answer is it's just one.


iptables -A INPUT -p udp --sport 137 -j ACCEPT


the catch with all the information I found with google was that most of it was for samba servers. I didn't want that. I just want to be able to browse my roommates network shares, and download from them. None of the information google provided suggested I need to allow the source port on the other end.

iptables for the average desktop user

The Best guide for learning the basics of iptables is here
Linux 2.4 Stateful firewall design for the most part it continues to apply to the 2.6 kernel. The only things that won't apply to your linux system will be: emerge if you aren't on gentoo, and the kernel options which have changed since 2.4 and even a couple of times during 2.6.

I'm not going to cover those here. If you need help building your kernel or installing iptables I suggest that you consult with either the iptables home page or even better your distribution. Chances are it is already installed, and may even be configured.

First Let's see if we have any rules.

The following commands require root access, and can be run in a root shell, with sudo, or in a shell script by root

iptables -L -v

your output should look something like this if you have no rules

Chain INPUT (policy ACCEPT 211 packets, 27413 bytes)
pkts bytes target prot opt in out source destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination

Chain OUTPUT (policy ACCEPT 312 packets, 211K bytes)
pkts bytes target prot opt in out source destination


If it looks different no worries it just means that your distro has already installed rules.

If so make sure BEFORE CONTINUING to flush them. FIRST check to make sure your policies are set to accept (you can see that in caps above) if they are anything else run


iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT


now that your policies are clean you should flush the rules

iptables -F #flush all rules
iptables -X #delete all chains


all right now hopefully you are at a clean state. If you have ever used iptables for nat you may not be, but that is beyond the scope of this article.

Now we need to create rules, since this is for normal deskop users you shouldn't have any services listening, also you shoudn't be routing anything.

to disable routing with iptables (I'm ignoring the kernel setting for this)


iptables -P FORWARD DROP

# set all forwarded packets to go bye bye if they reach the end of the chain

the output chain is good on accept for the normal user, only a masochist would want to write rules for it. You generally should trust your outbound traffic.

Now to secure input

iptables -A INPUT -m state --state INVALID -j DROP
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -P INPUT DROP

#this rule drops all packets with a bad state
#accept any packets that have something to do with ones we've sent on outbound
#accept any packets coming or going on localhost (this can be very important
# set all packets not matching these rules to drop

Various linux distro's may require you to do something special to save these rules so that they survive a reboot. consult your distributions community.

If you have rules that you want to keep but also want to use mine I suggest putting mine first, you should do the -A rules in reverse but use a -I for insert.

When dealing with iptables always take care when applying iptables -P DROP. You can be locked out of the machine or the internet if you apply this without the appropriate rules in place.

That's it. your desktop should be secure from an attacker that you aren't allowing in. There are of course other things that you can do to make it even more secure but those are beyond the scope of this tutorial.