Archive for Computers & WWW

Hashing phpBB Passwords

At some point in the future I’ll be writing a more comprehensive article on linking external applications authentication to the phpBB user system, but in the meantime, if you just want to hash passwords or compare hashes then the following code is really useful

define('IN_PHPBB', true);
$phpbb_root_path = './';
$phpEx = substr(strrchr(__FILE__, '.'), 1);
include($phpbb_root_path . 'common.' . $phpEx);

$password = 'password';
$hash = phpbb_hash($password);

if (phpbb_check_hash($password, $hash)) {
echo '"Hash "'.$hash.'" matches password "'.$password.'"';
}

It allows you to run a separate php file which utilises phpBB functions to hash passwords; call it from a shell script, use it to login to servers etc.

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Renaming WordPress index.php

Now as any developer who’s dabbled with WordPress knows, it’s easy to change the root directory location of WordPress so that directory structure wise different CMS systems can play nicely alongside one another.

What about, however, the situation where two CMS systems both require a root file of index.php? Well there you have a problem because if you change the name of the WordPress index file, which on the face of it seems easiest, you break the search feature (and possibly other things I’ve not found yet).

Fortunately I found a simple 3 step method which requires modifying only 1 line in 1 core file, which compared to other CMS systems, is not that many.

  1. Firstly you’ll want to follow the instructions on the link at the start of the article to move your WordPress root away from the root of your site so that it can co-exist with your other app. Then, instead of creating a file named index.php in your website root, you create wordpress.php or another name of your choosing
  2. Secondly, in the .htaccess file you created as part of the aforementioned guide, replace instances of index.php with wordpress.php or whatever name you chose
  3. Now, for the final bit of magic, locate the following file wp-includes/class-wp-rewrite.php and replace

    public $index = 'index.php';

    with

    public $index = 'wordpress.php';

    taking care to use your alternative file name if it differs

That’s a wrap as they say! You should find that WordPress works fine, including the search feature, all the while leaving index.php free for use by another CMS. Do let me know in comments how you get along with this if you try it.

Oh and remember, if you upgrade WordPress, which will happen every now and again, do check to make sure your core file change gets put back – I hate to change core, but as index.php is hard-coded, it’s the only way.

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Let’s Encrypt – Doing it Properly

A while ago I made a passing comment about replacing StartSSL using Let’s Encrypt and while it’s true you can use it in the way I described, it’s not as simple as the command would imply and there are a number of pitfalls – not least that if you side-step most of them by going a truly manual route, your efforts only last for 3 months – let’s encrypt certificates expire after only 3 months.

What this all boils down to is that in order to make proper use of this excellent free service you have to automate the process of obtaining and renewing certificates. Not just that though, because their python tooling (certbot) will do this in a general fashion for you, but to truly implement a hands off one size fits all solution. I articulated this as the following requirements.

  • Tool must check for impending expiry and renew in time to avoid nag e-mails
  • Support should be available for adding new certificate requests to the “pool”, not just to renew existing ones
  • A fixed, permanent web server must not be required
  • Servers running on non-standard ports must be supproted
  • Servers not ordinarily accessible to the public must be supported
  • Firewall must not be required to always be open to Let’s Encrypt servers
  • Tool must support servers who’s control IP (SSH etc.) differs from that to which an SSL certificate is to be assigned (A record of SSL domain)

A evening of hacking around on a Raspberry Pi to get certbot running and some hasty coding in bash revealed a solution which essentially, does the following, in order, for each domain requiring a certificate.

  1. Checks to see if the domain has a cert and if it’s expiring
  2. Creates a remote directory from which files will be served as part of the renewal process
  3. Inserts a temporary firewall rule to allow Lets’ Encrypt servers to validate the served files
  4. Starts a temporary lightweight webserver to serve said files and runs it on a port that Let’s Encrypt supports (80)
  5. Mounts this served directory locally on the certbot machine so that certbot can load files into it
  6. Runs certbot to create/renew the certificate
  7. Unmounts the temporary server directory
  8. Stops the temporary webserver
  9. Removes the temporary firewall rule
  10. Cleans up temporary files
  11. Load the certificate files onto the remote server over SSH
  12. Bounces any services that use them so that they are picked up (e.g. Apache)

Before I share the script, a few words of warning and a few pointers

  • Everything needs to run as root
  • I mounted a NAS share of my certificate files so that they were stored and backed up centrally. Certbot expects to find everything in /etc/letsencrypt so that will need to be your mount point if you use the NAS option
  • The script assumes that the server on which it is running has SSH keys setup on all hosts it needs to connect to such that passwordless root is possible.

If you don’t know how to do any of these things then you probably shouldn’t try using the script. It’s not that you won’t be capable or anything, rather that there are a lot of moving parts and basic Linux knowledge that would allow you to achieve these 3 points will go a long way in helping you to debug any issues with the script.

Finally then, the script; configured for two dummy domains, running on the same box, one serving from apache, the other a custom process.

#!/bin/bash
# Configuration section
email=your.email@address.com
certPath=/etc/letsencrypt/live/
remotePort=80 # Lets encrypt only supports 80 - ouch - we'll need to stop servers while doing this
domains=('one.domain.com' 'two.domain.com')
hosts=('1.2.3.5' '1.2.3.6')
sshHosts=('1.2.3.4' '1.2.3.4')
sslPathOnServer=('/etc/apache2/ssl/' '/etc/specialprocess/ssl/')
keyFileNameOnServer=('www.key' 'pub.key')
certFileNameOnServer=('www.crt' 'cert.crt')
chainFileNameOnServer=('www-chain.pem' 'chain.pem')
serverStopCommand=('/etc/init.d/apache2 stop' '/etc/init.d/specialprocess stop')
serverStartCommand=('/etc/init.d/apache2 start' '/etc/init.d/specialprocess start')

# Work is done here, no further edits!
i=0
for domain in ${domains[@]}; do
        # Ascertain if the certificate will expire in 3 weeks or less - stops lets encrypt nagging e-mails
        new=0
        if [ -d "$certPath$domain" ]
        then
                openssl x509 -in $certPath$domain/cert.pem -checkend $(( 86400 * 21 )) -noout
                result=$?
        else
                new=1
                result=1
        fi
        if [[ $result == 1 ]]
        then
                # Report the status
                if [[ $new == 1 ]]
                then
                        echo "Certificate for $domain [New]"
                        echo "Running certificate creation process..."
                else
                        echo "Ceritificate for $domain [Expiring]"
                        echo "Running renewal process..."
                fi
                # Start renewal process; create remote directory, iptables rule, start remote server
                echo -n "       Setting up iptables rules on remote server, stopping server process using certs & starting temporary micro server..."
                rule="INPUT 1 -p tcp -m tcp --dport $remotePort -d ${hosts[i]} -j ACCEPT"
                ssh root@${sshHosts[i]} << ENDSSH > /dev/null 2>&1
                eval ${serverStopCommand[i]}
                mkdir /tmp/$domain
                iptables -I $rule
                cd /tmp/$domain
                python -m SimpleHTTPServer $remotePort > /dev/null 2>&1 &
ENDSSH
                echo " Done"

                # Mount remote directory locally over SSHFS
                echo -n "       Creating mount to directory served by temporary micro server..."
                if [ -d /tmp/certbot ]
                then
                        rm -rf /tmp/certbot
                fi
                mkdir /tmp/certbot
                sshfs ${sshHosts[i]}:/tmp/$domain /tmp/certbot
                echo " Done"

                # Call letsencrypt to renew/create
                echo -n "       Call letsencrypt to renew the certificate in our store..."
                letsencrypt certonly --webroot -n -w /tmp/certbot -m $email -d $domain > /dev/null 2>&1
                echo " Done"

                # Unmount remote SSHFS directory
                echo -n "       Unmounting micro server directory and cleaning mount point..."
                umount /tmp/certbot
                rm -rf /tmp/certbot
                echo " Done"

                # SCP certificate/chain/key files to remote host
                echo -n "       Copying new certificate files to the server..."
                scp $certPath$domain/cert.pem ${sshHosts[i]}:${sslPathOnServer[i]}${certFileNameOnServer[i]} > /dev/null 2>&1
                scp $certPath$domain/privkey.pem ${sshHosts[i]}:${sslPathOnServer[i]}${keyFileNameOnServer[i]} > /dev/null 2>&1
                scp $certPath$domain/chain.pem ${sshHosts[i]}:${sslPathOnServer[i]}${chainFileNameOnServer[i]} > /dev/null 2>&1
                echo " Done"

                # Cleanup remote host; stop temp server, reload default iptables, cleanup temp directory, restart server process
                echo -n "       Stop micro server, clean up iptables rule & start server process using certs... "
                ssh ${sshHosts[i]} << ENDSSH > /dev/null 2>&1
                kill \`ps -ef | grep SimpleHTTPServer | grep -v grep | awk '{ print \$2; }'\`
                iptables -D INPUT 1
                rm -rf /tmp/$domain
                eval ${serverStartCommand[i]}
ENDSSH
                echo " Done"

                # Confirm completion
                if [[ $new == 1 ]]
                then
                        echo "Certificate for $domain [Created]"
                        echo "Creation process complete"
                else
                        echo "Renewal process complete"
                        echo "Certificate for $domain [Renewed]"
                fi
        else
                # Certificate needs no renewal, indicate as such
                echo "Certificate for $domain [OK]"
        fi
        i=$i+1
done

You’ll need to modify the variables/arrays at the start to get it working, some are obvious, but I’ll explain them anyway.

  • email : This is used to create, recover and access your account. Once created, the private key for accessing your account will be stored in the let’s encrypt home directory (usully /etc/letsencrypt)
  • certPath : The path to the /live directory in your let’s encrypt home directory, usually /etc/letsencrypt/live
  • remotePort : Leave this at 80; it’s just here to help setup iptables rules – it cannot be changed in let’s encrypt config
  • domains : An array of domains for which you want certificates
  • hosts : An array of IP addresses corresponding to the aforementioned certificates – keep the ordering the same!
  • sshHosts : An array of IP addresses used for administering each of the aforementioned domains; for example you may have several web servers/domains all being served from the same physical host – this would then be an array of identical IPs, corresponding in array size with the number of domains
  • sslPathOnServer : What is the file system path to each domain’s certificates on the host server
  • keyFileNameOnServer : Within that directory, what is the key file name
  • certFileNameOnServer : Within that directory, what is the certificate file name
  • chainFileNameOnServer : Within that directory, what is the chain file name
  • serverStopCommand : For each domain, what command stops the server process the domain is used for
  • serverStartCommand : Likewise, what is the command to start the server process again

That’s it! Best of luck if you choose to go this way and do let me know if the script is useful to you.

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Raspberry Pi MAC Address Changing on Reboot

I recently did a apt-get dist-upgrade on my Raspberry Pi running Raspbian 8 and when I rebooted the device appeared to drop clean off my network. I was away from home at the time so I decided to fix it when I was next on the premises – it wasn’t a hugely important device to have running 24/7.

When I looked at the device in person I realised that it was in fact connected to the network, but with a different IP address to that it had held before. Having MAC address based IP allocation, this seemed rather strange. Looking at the MAC address in ifconfig revealed the problem – it had changed! Thinking this to just be a fluke, I rebooted. Now, not only was the MAC still different to that which it should have been, it had changed a third time!

Investigating what had happened during the upgrade revealed that both the bootloader and the kernel had both been upgraded, but for whatever reason, the new kernel wasn’t being loaded. Modifying the /boot/config.txt as follows along with a reboot fixed this discrepancy and lo and behold the MAC returned to it’s former value and the device picked up the IP address it was supposed to have over DHCP

From

[pi1]
kernel=vmlinuz-4.4.0-1-rpi
initramfs initrd.img-4.4.0-1-rpi followkernel
# to enable DeviceTree, comment out the next line
device_tree=

To

[pi1]
kernel=vmlinuz-4.9.0-2-rpi
initramfs initrd.img-4.9.0-2-rpi followkernel
# to enable DeviceTree, comment out the next line
device_tree=

It’s worth pointing out that you may have a similar problem with a similar cause but slightly different kernel versions to me. If this is the case, or to check if it is, verify the old/new versions in /boot as follows

ls -lha /boot | grep initrd.*rpi

Which will reveal your old/new versions

-rwxr-xr-x 1 root root 5.7M Jul 3 18:26 initrd.img-4.4.0-1-rpi
-rwxr-xr-x 1 root root 13M Jul 3 18:46 initrd.img-4.9.0-2-rpi

You should then modify /boot/config.txt from the old version to the new version as per my above example.

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Failed to connect to lockdownd

After a recent holiday I wanted to download the photos from my iPhone – something I’ve long been able to do in Linux. Upon following my well trodden process, I was greeted with an unfamiliar error message

$ ifuse /media/kieran/iphone
Failed to connect to lockdownd service on the device.
Try again. If it still fails try rebooting your device.

Some reading around the subject revealed that encryption needed to be disabled on the libimobiledevice module that is used under Linux to pair with the iPhone. Rather than go to the effort of modifying the source myself, some helpful chap has already done this and published the code and usage guide to GIT. Hope this pointer helps someone who is stuck trying to access their phone.

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Replacing StartSSL

A small service I created for personal use had its SSL certificate expire a few weeks ago. I replaced it using my go-to free certificate provider, StartSSL. Unfortunately, accessing this service from my iPhone still didn’t work afterwards, or rather it did, but the certificate still wasn’t trusted. I was forced to ignore this issue at the time due to other pressing matters and, as the service was just used by me, on my device, I simply set the app to ignore the issue until I had time to diagnose the problem properly.

Today I replaced my e-mail signing certificate, also from StartSSL. This time I knew something was wrong; adding the certificate to Thunderbird and sending a test e-mail to be retrieved by my iPhone, the certificate again wasn’t trusted.

Turns out that silently, unbeknownst to me and I’m sure many others, the following chain of events has occurred

  1. StartCom which runs StartSSL were taken over by WoSign
  2. Due to past issues with WoSign regarding the erroneous issuing of certificates for a domain that they had no authority to issue for, they had their root certificate rights revoked by Apple, Mozilla, Google and others
  3. Since the take over of StartSSL, the aforementioned device/software companies have also ceased to trust the root certificates of StartCom.

This has resulted in my having to spring into action. The silent take-over of a previously trusted organisation by a dubious one located in a political jurisdiction known to be questionable with respect to web security is worrying enough, but with the added pain of being unable to send signed e-mail and issue new certs for my soon to expire domains required to be addressed immediately.

I’ve found that comodo, a trusted certficate authority, will issue free e-mail signing certs so I’ve jumped over to that immediately for e-mail and that is running nicely.

In addition there is “LetsEncrypt”, which, once installed, allows you to generate trusted SSL certificates for your domains using the following command

letsencrypt certonly --manual -d my.domain.com

When running the above it’s important to remember that validation you have control over the domain for which the certificate will be issued requires you to

  • Be running a web server on port 80 on the domain
  • Said port 80 server to be accessible publicly through your firewall
  • For you to place a file to be served on the web root of this server

You can always stop apache (or whatever your web server is) and run up a simple stand-alone python server to do the job, but you won’t be able to get away without changing your firewall rules.

This is a departure from the way I’m used to doing things which used the administrative e-mail address registered to the domain and code sent to this for validating I owned the domain. This was nicer as it meant I didn’t have to play with my config all that much (some servers I run use non-standard ports and don’t have port 80 open by default for example).

Anyhow, from my reading of the documentation about LetsEncrypt, it seems that all major browsers and Apple iOS are trusting certificates signed this way. I’ll update this post if that turns out not to be the case, but I’m optimistic.

Hopefully this post will help to raise awareness and also assist some folk out of a bit of a pickle with their security arrangements.

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Draytek DNS Drops

Some time ago I wrote an article about fixing a VPN connection issue over a Draytek router concerning a UDP flood defense setting. Its turns out that the very same setting can also cause an issue with DNS, the symptoms of which I will outline below. For the fix, head over to the old article above.

Essentially the symptoms are simple. You browse the web as normal and then all of a sudden DNS for new sites (not in local cache) stops resolving. A router reboot is the only way to fix the issue. Increasing the flood defense packet ceiling as mentioned in the article above stops the issue from occurring. I said it was simple!

As to why this issue had happened to me once more, despite having applied an earlier fix, I can only conclude that the ceiling I setup earlier, being tailored to the speed of my ADSL link at the time, should now be higher as I have around twice the bandwidth I used to. I doubled the value and now all is well.

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Focusing on the Value-Add

It’s a common thing on e-commerce sites these days; we find a product we like, read all about it, but before committing to a purchase, we decide to have a quick search around to make sure we’re getting the best deal price-wise. It’s the online shopping equivalent of trying on a pair of shoes in the shop and then having a quick check on your phone to make sure you can’t get a better deal elsewhere.

Understandably, retailers are twitchy about this. They build sites jam packed full of information, the value-add if you will, to try and encourage confidence in buyers, only to lose the sale on the price point, despite having invested in the customer experience.

I came across a site a few months ago that was fighting back against this post-decision shopping around in a very innovative way.

The following image is the product on sale

And this is what happens when you select the product name text with the intention of copying and pasting into a search engine

Now, it doesn’t *prevent* you from doing the copy/paste, but it does ensure you stop and think, as a customer, about the realities of doing business and if, given the level of service you’re getting, if the price is actually *already* fair.

Food for thought for e-commerce operators and customers alike I’d say.

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Locked out of iPhone

The other day I had cause to turn off my iPhone. Unlike many who leave theirs permanently on, it’s something I often do; restaurants, theatre, cinema, church to name but a few places where it’s simply good etiquette to do so. Anyway, I digress.

When I switched the device back on again some hours later, I was greeted with a request to “re-activate” it using my apple ID. The problem with this is that for those security concious people like myself who place their iCloud password in LastPass, you cannot get access to the the LastPass app if your phone is locked, which a de-activated phone effectively is.

Fortunately I was within easy reach of a PC on which I could install LastPass, login, retrieve the requisite password and unlock the phone.

This could have been so much worse though; with a phone that could do nothing but call 999 and no PC to retrieve my password, I could have been incommunicado while abroad or some other such significant inconvenience.

I simply didn’t *know* that an iPhone could just de-activate its self like that – certainly a risk worth evaluating when you decide what password (random, unknown, in LastPass v.s. simpler, recallable) to utilise for the purpose!

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PPTP VPN in Ubuntu 15.10

Recently I had cause to connect to my home VPN from my laptop, being out of town and on a connection not part of my usual trusted network. I tried to connect as usual using PPTP via the network manager on the Xubuntu desktop but no dice – the connection was failing every time. After establishing my iPhone was able to connect from the same network, I realised that the last time my laptop had successfully connected to the VPN was prior to my upgrade to Ubuntu 15.10 and therefore something must have changed with the default settings under the hood to cause the problem.

To cut a long story short, after much digging and hair pulling, I established that you need to enable 3 kernel modules to get the PPTP VPN client back up and running in the latest version of Ubuntu. Add the following to /etc/modules and reboot

nf_nat_pptp
nf_conntrack_pptp
nf_conntrack_proto_gre

After that you should find that your PPTP VPN connection invoked in the usual way from the network manager no longer fails. Happy days!

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