Category Archives: Open Source

FreeBSD, Linux, OpenBSD, Unix

Mutt account passwords

First, to give credit where it’s due, I started here. That said, here’s how I store and access account passwords in mutt on Linux.

## -- Passwords: encrypted by gpg --------------------------------------------------------------

source “/bin/gpg -d ~/.keychain/mutt.password.neopost.gpg 2>/dev/null |”

The source line in gpg tells mutt to decrypt a file at startup. The file .keychain/mutt… contains two mutt configuration lines:

set imap_pass = "<my_email_password>"
set smtp_pass = "<my_email_password>"

I created it as follows:

$ cat <<EOF | gpg -r <my_gpg_id> ~/.keychain/mutt.password.neopost.gpg
set imap_pass = "<my_email_password>"
set smtp_pass = "<my_email_password>"
EOF
$

Gpg knows how to decrypt this file and retrieve the plain text configuration. Note well that I used a “Here” document to create the file. This keeps mail password out of the filesystem. Simple stuff, at mutt startup the first time I use it, gpg-agent asks for my gpg key and unlocks the configuration snippet.

FreeBSD, OpenBSD, Unix

Submission brutes

Brush aside vandals attacking my submission daemon with a little sed:


submission_brutes=$(bzcat /var/log/maillog.0.bz2 | \
cat - /var/log/maillog | \
sed -Ene '/postfix\/submission\/smtpd.*errors after AUTH/s/^.*[^0-9]+(([0-9]+\.){3}[0-9]*).*$/\1/p' | sort -u)
[[ ! -z "${submission_brutes}" ]] && pfctl -t blackhole -T add ${submission_brutes}

FreeBSD

pf required: pass proto ipv6-frag all

FreeBSD’s pf has serious problems with ipv6 fragment handling. The problems cascade into other issues like named axfr time outs.  Add this, “pass proto ipv6-frag all”, to your ruleset somewhere near your antispoof rules to fix this.

Much of the issue is that the FreeBSD team has diverged their version of the pf firewall so far from the OpenBSD version that they cannot incorporate upstream fixes. I’m not making my situation any better by sticking with FreeBSD 9. Some of this is probably addressed in FreeBSD 10.

While this persists the best course of action is probably to make sure it works on OpenBSD first, then figure out how to deal with any FreeBSD issues.

SysAdmin

More WiFi isn’t always better WiFi

I generally like my Cable TV company. This is mostly because they have realized that they won’t be a Cable TV company in ten years and they are running their business according to that mantra. In English, this means that they are putting their effort in being a very very good consumer grade ISP. One of the side benefits that Cable Internet has been offering is access to public hotspots. As a consortium these companies have nearly every urban area that I’ve been to covered in WiFi. On the surface this seems to be a good thing but it has some downsides. Most WiFi uses the 2.4GHz frequency band. WiFi routers ship with a range in open air of about 450m. There are only three non-overlapping channels in the 2.4GHz band. If you’ve debugged WiFi in an urban setting, you are probably painfully aware of these three characteristics of 2.4GHz WiFi. When they Cable TV company starts deploying open hotspots in your neighborhood, they aren’t pushing the system to a solution for this problem.

I have to qualify this as a rant though since there isn’t much that anyone can do to fix the problem. Especially since the Cable TV companies have started enhancing their WiFi offering by giving away high powered WiFi routers which that offer dual SSID to their customers. It won’t be long before anyone who want’s to do anything will be in 5GHz.

SysAdmin

Apple’s Captive Network Assistant

In an attempt to make life easier Apple added the Captive Network Assistant App to OS X. I think this addition was made sometime around Lion. Captive Network Assistant is an App that can display a little the very simple web page you get when you connect to a wifi network that has Captive Portal. These are the pages you get when you first log onto your coffee shop WiFi. They usually ask you to agree to some terms and conditions before you can use the network. In the case of hotels, resorts, and cruise ships they will also tie to the site billing system so you can be charged if that’s appropriate. Lately I’ve started to get these sites on both my MiFi hotspot and most lately, my home WiFi. This article explains three major drawbacks to Apple’s approach here. The authors of these web pages will frequently embed logout information into the page when the captive portal mechanism is being used to track usage for billing. In this use case, the app is a hinderance because when it disappears, it takes the logout link with it. Also, Apple triggers the app by attempting to fetch a known page over the web when your WiFi first connects. If it doesn’t get what it expects, it knows it’s behind a Captive Portal. In my case, the Captive Portal App is displaying Apple’s static page which indicates that you aren’t behind a portal.

When I started seeing captive portal on my home network, I decided the turn the thing off. To turn captive portal off do this command:

sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.captive.control Active -boolean false

To restore the old behavior, do this, again in a terminal window:

sudo defaults delete /Library/Preferences/SystemConfiguration/com.apple.captive.control Active

Other people including the article linked above recommend renaming the App. I’m not in love with that solution, mostly because two months from now I don’t expect to remember that I did this in the first place. My solution isn’t much better. One could argue it’s worse because it requires terminal and sudo. It’s the one I went with though.

FreeBSD

FreeBSD cross compiling or “Thanks Captain Obvious…”

It would be nice to manage my fleet of FreeBSD machines from one place. But I’ve diversified from i386 only to i386 and amd64 as I start doing more and more stuff with virtual machines; single purpose servers and less power usage for-the-win. The question comes up, do I need build-i386.vindaloo.com and build-amd64.vindaloo.com — Nope:

# env TARGET=i386 MAKEOBJDIRPREFIX=/usr/obj/i386 make buildworld...

SysAdmin

NFS – Old habits die hard

Old habits and myths die hard. Conventional wisdom asserts that UDP is better because it has lower overhead; then conventional wisdom suggests that you tune the buffer sizes to improve performance. On the face of things that would seem to work but once the the write size exceeds the max packet size, NFS delivers the packet by using multiple packets. Sending multiple packets triggers the issue because dropping just one UDP packet means the whole buffer must be resent. Contrast with TCP: yes the packet header is larger so less data can be sent and yes the receiving side has to ack each packet. But: with TCP if a packet gets dropped, only that packet needs to be resent; with a modern TCP stack the kernel will constantly adjust the window size to make the best use the available bandwidth. In other words NFS over tcp will automatically tune the buffer sizes for the current conditions.