project-2501.net

Post-Increment Variable Bug

Matthew — Tue, 08 Nov 2011 10:38:06 +0000

Found this little bug today in some old (untested code). I was amused that the code would have worked using pre-increment operator (and yet, still been wrong).

# Simplified example, in the original code this was 3 lines long
# Assume use_record_map = false;
record_id = (use_record_map) ? lookup_record_id(foo) : record_id++;

Pythons lack of ++ / — operators makes a little more sense now (one extra character in exchange for removing several type of bugs. Even if they are rather obvious bugs).

New Car :)

Matthew — Tue, 18 Oct 2011 11:27:21 +0000

Guild Wars: E/Me Vaettir Farm

Matthew — Thu, 13 Oct 2011 03:14:28 +0000

E/Me Obsidian Flesh Vaettir Farm (HM)

Skills

OgVFI7QIlMPkLo0n2wXlBgMwSgWF

Elemental Lord (Optional)
Glyph of Swiftness
Obsidian Flesh
Stoneflesh Aura
Mantra of Earth
Wastrel’s Worry
Arcane Echo
Storm Djinn’s Haste (Optional)

Attributes

12 + 3 + 1 Earth Magic
3 + 1 Energy Storage
4 Air Magic
4 Inspiration Magic
11 Domination

Weapon

+20% Enchantment length

Armor

5x Geomancer Runes (I think you can get away with a +10 earth shield instead)
Sup Earth Magic
Minor Energy Storage

Notes

If you get attacked by the Wurm in Bjora Marches, just put up Obsidian Flesh right away and you’ll be fine

When you have all 60 mobs drag them in between the building + wall to stop them scattering

Be careful not to let them body block you

Elemental Lord isn’t required, and only gives you an extra 1s on Obsidian flesh.

A faster, nicer A/Me run can be found here: http://www.youtube.com/watch?v=zZ1h2GoOpag

Recorded 2011-10-12

In other news, currently at 29/50 points in the Hall of Monuments.

Guild Wars: Capturing a Black Widow spider

Matthew — Tue, 20 Sep 2011 12:18:37 +0000

Some more random Fraps footage this time from Guild Wars. Been busy getting points in the Hall of Monuments.

Nothing impressive, but I had never done much end-game content, and maybe it will help save someone else some gold after seeing how easy it is.

I took 6 heros: Three Discordway Necros, Prot Monk, Panic Mesmer and a SoS Ritulist. Ump came with me on his Barrage Ranger, and I had some stupid Ele/R spec (with unspent points…).

The entire run took less than 30 minutes and I’m sure if you had a real build and knew where you were going, it would be very fast.

Walk-through:

Clear out the spawn area without accepting any quests

Take the Clear the Chamber quest from the spawn area and clear out the new mobs

Head north/west and take out all the mobs on the way

Talk to the Reaper of the Labyrinth and take the quest Restoring Grenth’s Monuments

Head south until you reach the Reaper of the Forgotten Vale

Clear out any nearby Coldfire Nights to the north

Take the quest Wrathful Spirits and kill all the Wrathful Spirits (Making sure not to let the Mayor die)

Hand in the quest and capture your spider (remember to flag the Heros well away from you, or they’ll kill the spider as you start to charm it)

Recorded 2011-09-20

Diablo 2 Fun

Matthew — Fri, 26 Aug 2011 14:40:06 +0000

Just some fraps footage I had on my HDD taking up space

I follow Umpa around as he kills Lilith, Uber Izual, Uber Duriel, Uber Mephisto, Uber Baal and finally Pandemonium Diablo.

Recorded 2nd July 2011

US West Ladder

My Character

Roman Numerals

Matthew — Mon, 08 Aug 2011 10:00:13 +0000

From reddit.com/r/programingchallenges:

I googled this and I haven’t found a similar challenge, so I’d like to pose this question to you all!
Let’s say I give you a range from 1 to 2000. Within this range, find the number that yields the most characters. I asked a friend of mine and he worked out that 1888 has a lot of characters (MDCCCLXXXVIII).

Solution

import time

SYMBOLS = [
('M', 1000),
('CM', 900),
('D', 500),
('CD', 400),
('C', 100),
('XC', 90),
('L', 50),
('XL', 40),
('X', 10),
('IX', 9),
('V', 5),
('IV', 4),
('I', 1)]

def roman_numeral(number):
roman_number = [];
for (symbol, value) in SYMBOLS:
while value <= number:
roman_number.append(symbol)
number -= value
return ''.join(roman_number);

start = time.time();

pairs = [(i, roman_numeral(i)) for i in range(1, 2000)]
pairs.sort(lambda a,b: cmp(len(a[1]), len(b[1])))

print 'Longest roman numeral for numbers 1-2000 = %d -> %s' % \
(pairs[-1][0], pairs[-1][1])

print 'Took: %.2fsec' % (time.time() - start,)

Output

Longest roman numeral for numbers 1-2000 = 1888 -> MDCCCLXXXVIII
Took: 0.14sec

Notes
Turns out historically there wasn’t a strict set of rules for Roman numerals, for example IV and IIII are both valid representations of the number 4. Only recent rules have added limits on the number of repeated characters and what values can be subtracted from other values. Reference.

IP Address Range PHP Class

Matthew — Thu, 28 Jul 2011 12:00:10 +0000

I’m not sure how useful this piece of code really is, but it gave me the chance to write some funky PHP code (have a look at the next() method).

Example usage

// Single host:
foreach(new IpRange('10.10.10.10') as $ip)
{
echo $ip . "\n"
}

// >>> 10.10.10.10

// All hosts on a private network:
foreach(new IpRange('192.168.0.1-255') as $ip)
{
echo $ip . "\n";
}

// >>> 192.168.0.1
// >>> 192.168.0.2
// >>> ...
// >>> 192.168.0.254
// >>> 192.168.0.255

// All normal (not broadcast, or multicast) IP addresses:
foreach(new IpRange('1-232.0-255.0-255.0-255') as $k => $v)
{
echo "$k => $v\n";
}

// >>> 0 => 1.0.0.0
// >>> 1 => 1.0.0.1
// >>> 2 => 1.0.0.2
// >>> ...
// >>> 7315795 => 1.111.161.83
// >>> 7315796 => 1.111.161.84
// >>> etc

?>

Source

/*

Copyright (c) 2011, Matthew Davey
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

/*

IpRange Class

Given an IP address where each octet can either be a number between 0 and
255, or a range i.e. 100-200. Return an iterable object that returns all
IP addresses in between.

Examples
--------

Single host:
foreach(new IpRange('10.10.10.10') as $ip)
{
echo $ip . "\n"
}

>>> 10.10.10.10

All hosts on a private network:
foreach(new IpRange('192.168.0.1-255') as $ip)
{
echo $ip . "\n";
}

>>> 192.168.0.1
>>> 192.168.0.2
>>> ...
>>> 192.168.0.254
>>> 192.168.0.255

All normal (not broadcast, or multicast) IP addresses:
foreach(new IpRange('1-232.0-255.0-255.0-255') as $key => $value)
{
echo "$key => $value\n";
}

>>> 0 => 1.0.0.0
>>> 1 => 1.0.0.1
>>> 2 => 1.0.0.2
>>> ...
>>> 7315795 => 1.111.161.83
>>> 7315796 => 1.111.161.84
>>> etc

*/

class IpRange implements Iterator
{
protected $count; // Current position, used as the key

protected $a; // ranges for each octet, l => low, h => high
protected $b; //
protected $c; // Most significant to least is aaa.bbb.ccc.ddd
protected $d; //

protected $ca; // current value of a
protected $cb; // current value of b
protected $cc; // current value of c
protected $cd; // current value of d

protected $isValid; // flag set when next() is call at end of ranges

public function __construct($string)
{
if(preg_match('#^(\d+|\d+-\d+)\.(\d+|\d+-\d+)\.(\d+|\d+-\d+)\.(\d+|\d+-\d+)$#', $string, $matches) !== 1)
{
throw new InvalidArgumentException('Invalid format. Each octet should either be a number between 0 and 255, or a range "40-120"');
}

// Parse each octet and find the low/high values (high === low if there is no range specified)
foreach(array(1 => 'a', 2 => 'b', 3 => 'c', 4 => 'd') as $i => $position)
{
$range = $matches[$i];

if(strpos($range, '-') !== false)
{
list($low, $high) = explode('-', $range);
}
else
{
list($low, $high) = array($range, $range);
}

// Check the IP address is at least mostly valid. We don't need to check for <0 as our regex will reject it first.
if($high > 255) throw new InvalidArgumentException("Invalid IP address. The octet '$high' cannot be greater than 255");

// If given a range like 255-0, flip the high/low value over
if($low > $high) list($high, $low) = array($low, $high);

$this->{$position} = array('l' => $low, 'h' => $high);
}

$this->rewind();
}

public function current()
{
return "{$this->ca}.{$this->cb}.{$this->cc}.{$this->cd}";
}

public function key()
{
return $this->count;
}

public function rewind()
{
$this->ca = $this->a['l'];
$this->cb = $this->b['l'];
$this->cc = $this->c['l'];
$this->cd = $this->d['l'];

$this->count = 0;

$this->isValid = true;
}

public function valid()
{
return $this->isValid;
}

public function next()
{
$this->count++;

// Least significant to most. Null is our guard.
foreach(array('d', 'c', 'b', 'a', null) as $position)
{
// Check if unable to generate the next IP address
if($position === null)
{
$this->isValid = false;
break;
}

// Check if the value is less than the maximum for this
// position, if so increment the value and stop. Otherwise set
// this position to its lowest value, and continue onto the next
// highest position.
if($this->{"c$position"} < $this->{$position}['h'])
{
$this->{"c$position"}++;
break;
}
else
{
$this->{"c$position"} = $this->{$position}['l'];
}
}
}
}

VPN Week – IPSec on OpenBSD

Matthew — Sat, 16 Jul 2011 19:12:50 +0000

This week I’ve spent a lot of time mucking around with IPSec VPNs. I thought I should informally document some of my settings in the hope that in a years time, when I’ve forgotten everything, I have some sort of base to build on.

OS: OpenBSD >= 3.8 / Windows 7
Protocol: IPSec

Part 1 – Common Configuration

Make sure the following are enabled (via /etc/sysctl.conf or the sysctl command)

net.inet.ip.forwarding=1
net.inet.esp.enable=1
net.inet.ah.enable=1

OpenBSD is awesome thanks to ipsecctl; a 4 line configuration file is all you need for a basic setup. But first we need to start isakmpd the IKEv1 key management daemon. As we are using ipsecctl to manage most of the setup, we use the -K option to ignore the isakmpd.policy file.

To see the log files for isakmpd use -DA=nn to set the debug level of all classes to nn (where nn is between 0 and 99; I’d suggest 50). Combine with with -d to keep the daemon running in the foreground.

isakmpd -K -DA=50 -d > /tmp/isakmpd.log 2>&1

ipsecctl is used in a similar way to everyone favourite tool pfctl. To load a configuration just run:

ipsecctl -f /etc/ipsec.conf

Don’t forget to check your firewall as well, you’ll need to open up port 500 (UDP) and if you want to see the unencrypted traffic set skip on enc0.

(TODO: I also have “pass in on $if_ext inet proto esp from any to $server_me_ext” is this actually needed?)

Part 2 – Site to Site IPSec OpenBSD <-> OpenBSD

Open up /etc/ipsec.conf with vim, and then curse and moan that OpenBSD still doesn’t include vim in a default install.

Our site-site config looks like:

ike esp from 10.10.42.0/24 to 192.168.1.0/24 \
peer 103.103.103.103 \
main auth hmac-sha1 enc aes \
quick auth hmac-sha1 enc aes \
srcid 204.204.204.204 psk "put a real pre shared key here"

Where 10.10.42.0/24 is the local internal network, 192.168.1.0/24 is the remote network, 103.103.103.103 is the remote external IP and our eternal IP is 204.204.204.204.

(TODO: Fix this to use macros and define this nicely)

All that’s left is to run ipsecctl and then replicate these settings on your other OpenBSD box (all the settings will just be reversed) and you’re done.

Part 3 – Road Warrior IPSec OpenBSD <-> Windows 7

As you can see, still super simple. We are using passive mode here so our server will not try to make a VPN connection, just listen for one.

ike passive from any to any \
main auth hmac-sha1 enc aes group modp1024 \
quick auth hmac-sha1 enc aes \
psk "good pre shared secrets are important"

(TODO: from any to any, will this give access to the entire network? Wouldn’t from 10.10.42.0/24 to any be better?)

(TODO: Why do we use DH Group 2 (modep1024) here and not above?)

On the Windows side I’m using Shrew Soft’s VPN client which is not only free, but works well.

I created a new Site Configuration and used the follow settings (click the image for a full view).

Of note:

Disable auto configuration
Change authentication to mutual PSK and entered the PSK
Set exchange type to main
Set DH Exchange to Group 2 for both phase 1 and phase 2

Part 4 – Summary

As you can tell I’m still learning this myself, and hopefully I’ll come back to this is a year, call my old-self an idiot and write a far better post.

Note: I wrote this at 5am in the morning, so please excuse all the mistakes

Code Smell

Matthew — Mon, 04 Jul 2011 03:26:06 +0000

“In computer programming, code smell is any symptom in the source code of a program that possibly indicates a deeper problem.” — Wikipedia

I found this piece of code this morning, I think it counts as something gone terribly, terribly wrong:

return displayItemDetails(this.parentNode.parentNode.parentNode.parentNode.parentNode.parentNode, 14059111);

(The code was in-line JavaScript, inserted into a onclick handler, generated in PHP)

Perlbal as a reverse proxy

Matthew — Thu, 09 Jun 2011 03:15:14 +0000

I recently needed to set up a new reverse proxy as an alternative to pound, and for no particularly good reason chose Perlbal.

The documentation is fairly good, but I didn’t find many (good) examples of working configurations. So I thought I’d include my very simple conf.

LOAD vhosts

# Management service via telnet
CREATE SERVICE mgmt
SET role = management
SET listen = 127.0.0.1:16000
ENABLE mgmt

# Web server
CREATE POOL web
POOL web ADD 10.10.42.41:80

# Trac server
CREATE POOL trac
POOL trac ADD 10.10.42.42:80

CREATE SERVICE web_proxy
SET role = reverse_proxy
SET pool = web
ENABLE web_proxy

CREATE SERVICE trac_proxy
SET role = reverse_proxy
SET pool = trac
ENABLE trac_proxy

# Internally we use 'trac.internal.com' but externally it would
# be 'trac.external.com'. So rather than creating a second
# virtual host on our trac webserver, we re-write the header
HEADER trac_proxy REMOVE Host
HEADER trac_proxy INSERT Host:trac.internal.com

# Listen on our external IP
CREATE SERVICE selector
SET listen = 100.110.120.130:80
SET role = selector
SET plugins = vhosts

VHOST external.com.au = web_proxy
VHOST www.external.com.au = web_proxy
VHOST trac.external.com.au = trac_proxy
ENABLE selector