Turn the Beaglebone Black into a personal communications server
Author: Bob Mottram
Keywords: freedombox, debian, beaglebone, red matrix, email, web server, home server, internet, censorship, surveillance, social network, irc, jabber

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Home
Why not supply a disk image download?
Is metadata protected?
How do I get a domain name?
How do I get a "real" SSL certificate?
Why use self-signed certificates?
Why not use the services of $company instead? They took the Seppuku pledge

## Why not supply a disk image download?

Shipping a Freedombone disk image ready to install on a flash disk would be easy, but disk images are relatively opaque. It would be quite easy to hide something nasty within a disk image and the user might never know. To guard against that possibility installing via the install-freedombone.sh script is a lot more transparent. You can check the code to see exactly what it's doing, and the packages are all downloaded from standard Debian repos (you can even choose which one you trust) or git repos. Doing it this way the system is fully auditable, whereas when shipping a disk image it's harder to be confident that no nefarious extras have been added.

## Is metadata protected?

Even when using Freedombone metadata analysis by third parties is still possible. They might have a much harder time knowing what the content is, but they can potentially construct extensive dossiers based upon who communicated with your server when. Metadata leakage is a general problem with most current web systems and it is hoped that more secure technology will become available in future. But for now if metadata protection is your main concern using Freedombone won't help.

## How do I get a domain name?

Suppose that you have bought a domain name (rather than using a free subdomain on freedns) and you want to use that instead.

Remove any existing nameservers for your domain (or select "custom" nameservers), then add:

    NS1.AFRAID.ORG
    NS2.AFRAID.ORG
    NS3.AFRAID.ORG
    NS4.AFRAID.ORG

It might take a few minutes for the above change to take effect. Within freedns click on "Domains" and add your domains (this might only be available to paid members). Make sure that they're marked as "private".

Select "Subdomains" from the menu on the left then select the MX entry for your domain and change the destination to 10:mydomainname rather than 10:mail.mydomainname.

To route email to one of your freedns domains:

    editor /etc/mailname

Add any extra domains which you own, then save and exit.

    editor /etc/exim4/update-exim4.conf.conf

Within dc_other_hostnames add your extra domain names, separated by a colon ':' character.

Save and exit, then restart exim.

    update-exim4.conf.template -r
    update-exim4.conf
    service exim4 restart

You should now be able to send an email from postmaster@mynewdomainname and it should arrive in your inbox.

## How do I get a "real" SSL certificate?

You can obtain a free "official" (as in recognised by default by web browsers) SSL certificate from StartSSL. You will first need to have bought a domain name, since it's not possible to obtain one for a freedns subdomain, so see Using your own domain for details of how to do that. You should also have tested that you can send email to the domain and receive it on the Freedombone (via Mutt or any other email client).

When creating a SSL certificate it's important that the private key (the private component of the public/private pair in public key cryptography) be generated on the Freedombone and remain there. Don't generate the private key via the StartSSL certificate wizard because this means that potentially they may retain a copy of it which could then be exfiltrated either via Lavabit style methodology, "implants", compromised sysadmins or other "side channel" methods. So that the private key isn't broadcast on the internet we can instead generate a certificate request, which is really just a request for authorisation of a public key.

Firstly you should have a web server site configuration ready to go. See Setting up a web site for details.

Within StartSSL under the validations wizard validate your domain, which means sending an email to it and confirming a code.

Now we can generate the certificate request as follows.

    export HOSTNAME=mydomainname.com
    openssl genrsa -out /etc/ssl/private/$HOSTNAME.key 2048
    chown root:ssl-cert /etc/ssl/private/$HOSTNAME.key
    chmod 440 /etc/ssl/private/$HOSTNAME.key
    mkdir /etc/ssl/requests

Now make a certificate request as follows. You should copy and paste the whole of this, not just line by line.

    openssl req -new -sha256 -key /etc/ssl/private/$HOSTNAME.key -out /etc/ssl/requests/$HOSTNAME.csr

For the email address it's a good idea to use postmaster@mydomainname.

Use a random 20 character password, and keep a note of it. We'll remove this later.

View the request with:

    cat /etc/ssl/requests/$HOSTNAME.csr

You can then click on "skip" within the StartSSL certificates wizard and copy and paste the encrypted request into the text entry box. A confirmation will be emailed back to you normally within a few hours.

Log into your StartSSL account and select Retrieve Certificate from the Tool Box tab. Copy the text.

    editor /etc/ssl/certs/$HOSTNAME.crt

Paste the public key, then save and exit. Then on the Freedombone.

    mkdir /etc/ssl/roots
    mkdir /etc/ssl/chains
    wget "http://www.startssl.com/certs/ca.pem" --output-document="/etc/ssl/roots/startssl-root.ca"
    wget "http://www.startssl.com/certs/sub.class1.server.ca.pem" --output-document="/etc/ssl/chains/startssl-sub.class1.server.ca.pem"
    wget "http://www.startssl.com/certs/sub.class2.server.ca.pem" --output-document="/etc/ssl/chains/startssl-sub.class2.server.ca.pem"
    wget "http://www.startssl.com/certs/sub.class3.server.ca.pem" --output-document="/etc/ssl/chains/startssl-sub.class3.server.ca.pem"
    ln -s "/etc/ssl/roots/startssl-root.ca" "/etc/ssl/roots/$HOSTNAME-root.ca"
    ln -s "/etc/ssl/chains/startssl-sub.class1.server.ca.pem" "/etc/ssl/chains/$HOSTNAME.ca"
    cp "/etc/ssl/certs/$HOSTNAME.crt" "/etc/ssl/certs/$HOSTNAME.crt+chain+root"
    test -e "/etc/ssl/chains/$HOSTNAME.ca" && cat "/etc/ssl/chains/$HOSTNAME.ca" >> "/etc/ssl/certs/$HOSTNAME.crt+chain+root"
    test -e "/etc/ssl/roots/$HOSTNAME-root.ca" && cat "/etc/ssl/roots/$HOSTNAME-root.ca" >> "/etc/ssl/certs/$HOSTNAME.crt+chain+root"

To avoid any possibility of the certificates being accidentally overwritten by self-signed ones at a later date you can create backups.

    mkdir /etc/ssl/backups
    mkdir /etc/ssl/backups/certs
    mkdir /etc/ssl/backups/private
    cp /etc/ssl/certs/$HOSTNAME* /etc/ssl/backups/certs/
    cp /etc/ssl/private/$HOSTNAME* /etc/ssl/backups/private/
    chmod -R 400 /etc/ssl/backups/certs/*
    chmod -R 400 /etc/ssl/backups/private/*

Remove the certificate password, so if the server is rebooted then it won't wait indefinitely for a non-existant keyboard user to type in a password.

    openssl rsa -in /etc/ssl/private/$HOSTNAME.key -out /etc/ssl/private/$HOSTNAME.new.key
    cp /etc/ssl/private/$HOSTNAME.new.key /etc/ssl/private/$HOSTNAME.key
    shred -zu /etc/ssl/private/$HOSTNAME.new.key

Create a bundled certificate which joins the certificate and chain file together.

    cat /etc/ssl/certs/$HOSTNAME.crt /etc/ssl/chains/startssl-sub.class1.server.ca.pem > /etc/ssl/certs/$HOSTNAME.bundle.crt

And also add it to the overall bundle of certificates for the Freedombone. This will allow you to easily install the certificates onto other systems.

    mkdir /etc/ssl/mycerts
    cp /etc/ssl/certs/$HOSTNAME.bundle.crt /etc/ssl/mycerts
    cat /etc/ssl/mycerts/*.crt > /etc/ssl/freedombone-bundle.crt
    tar -czvf /etc/ssl/freedombone-certs.tar.gz /etc/ssl/mycerts/*.crt

Edit your configuration file.

    editor /etc/nginx/sites-available/$HOSTNAME

Add the following to the section which starts with listen 443

    ssl_certificate /etc/ssl/certs/mydomainname.com.bundle.crt;

Save and exit, then restart the web server.

    service nginx restart

Now visit your web site at https://mydomainname.com/ and you should notice that there is no certificate warning displayed. You will now be able to install systems which don't allow the use of self-signed certificates, such as Red Matrix.

## Why use self-signed certificates?

Almost everywhere on the web you will read that self-signed certificates are worthless. They bring up scary looking browser warnings and gurus will advise you not to use them. Self-signed certificates are quite useful though. What the scary warnings mean - and it would be good if they explained this more clearly - is that you have an encrypted connection established but there is no certainty about who that connection is with. The usual solution to this is to get a "real" SSL certificate from one of the certificate authorities, but it's far from clear that such authorities can be trusted. There have been various scandals involving such organisations, and it does not seem plausible to assume that they are somehow immune to the sort of treatment which Lavabit received. So although most internet users have been trained to look for the lock icon as an indication that the connection is secured that belief may not always be well founded.

Security of web sites on the internet is still a somewhat unsolved problem, and what we have now is a less than ideal but good enough to fool most of the people most of the time kind of arrangement. Long term a better solution might be to have a number of certificate authorities in a number of different jurisdictions vote on whether a given certificate actually belongs to a given domain name. Experimental systems like this exist, but they're not widely used. Since the current certificate system has an enormous amount of inertia behind it change could be slow in arriving.

For now a self-signed certificate will probably in most cases protect your communications from "bulk" passive surveillance. Once you've got past the scary browser warning and accepted the certificate under most conditions (except when starting up the Tor browser) you should not repeatedly see that warning. If you do then someone may be trying to meddle with your connection to the server. You can also take a note of the fingerprint of the certificate and verify that if you are especially concerned. If the fingerprint remains the same then you're probably ok.

## Why not use the services of $company instead? They took the Seppuku pledge

That pledge is utterly worthless. Years ago people trusted Google in the same sort of way, because they promised not be be evil and because a lot of the engineers working for them seemed like honest types who were "on our side". Post-nymwars and post-PRISM we know exactly how much Google cared about the privacy and security of its users. But Google is only one particular example. In general don't trust pledges made by companies, even if the people running them seem really sincere.

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