OPENPGPKEY and DANE

As a long time PGP user I wanted to improve the key landscape and offer my public key via DANE. This is quite simple, if you have a DNS host, that supports DNSSEC and the different needed DANE types. (Note: I use core-networks.de)

The principle behind this: You publish your PGP key in your signed DNS and by that a correctly configured mail system could opt into sending you encrypted E-Mails even without having exchanged keys before.

I have tried to use the gpg2 function “–print-dane-records” (available from 2.1.9 upwards), however could not generate a usable data part of the DNS record via this.

So what is the solution

As a prerequisite you need to have created your own PGP keys with the E-Mail you want to use as an User ID. Note: I am only doing a per E-Mail Setup.

Use the following website: https://www.huque.com/bin/openpgpkey
Generate an OPENPGPKEY output pretty much does the trick.

The generated output is sorted as follows:

  • Owner Name goes into the record. Be careful, if your DNS provider automatically adds the domain.If you used “–print-dane-records” you need to concatenate the ID of the key (before TYPE61) and string after $ORIGIN
    The syntax is “<SHA256 hash of your e-mail name before the @>._openpgpkey.<your domain>”
  • Out of Generated DNS OPENPGPKEY Record you take the part within the () into the data part of the record. Here you need to transform the key into one line string.
    If you used “–print-dane-records”, I discarded the data part, as I could not get it to work. Simply use your key data exported with ASCII armor (-a parameter) without the last line. Of course leaving headers and footers out as well.
  • The type is OPENPGPKEY
  • Class is IN
  • TTL you can set on a decent value. For testing I used a hour.

To test the setup use

dig OPENPGPKEY <Owner Name goes here>

This will simply send back the data block and test the DNS setup.

To test the DANE lookup do the following

gpg2 --auto-key-locate clear,dane,local -v --locate-key <your e-mail goes here>

This gives quite a good feedback on the setup and tells you if the key was fetched via DANE or not.

 

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SendXMPP mail forward on Debian Jessie

To have a more comfortable way of receiving messages by my servers, I wanted all my root E-Mails to be forwarded to my mobile via XMPP. I only have a limited exim4 on my machine running, configured for local mail delivery only.

So what is the solution

1. Install sendxmpp

apt-get install sendxmpp

2. Create config file as “/etc/sendxmpp.conf”

@

as an example:

sendinguser@jabber.mydomain.com supersecretpassword! mydomain.com

3. Set the right permissions and owner

chmod 600 /etc/sendxmpp.conf
chown Debian-exim:Debian-exim /etc/sendxmpp.conf

4. Create a script to call sendxmpp as “/usr/sbin/mail2xmpp”. It might be that you could put this completely into the alias, however I decided to use the script.
Exchange with your receiving ID. “-t” enables the TLS connection for sending the message.

#!/bin/bash 
echo "$(cat)" | sendxmpp -t  -f /etc/sendxmpp.conf

5. Make script executable

chmod 755 /usr/sbin/mail2xmpp

6. Create the alias for the user, which E-Mails you want to forward in “/etc/aliases”

root: , |/usr/sbin/mail2xmpp

7. To activate pipe forwarding we have to create “/etc/exim4/exim4.conf.localmacros”

SYSTEM_ALIASES_PIPE_TRANSPORT = address_pipe

8. Run newaliases and restart exim4 for config to take effect

newaliases
service exim4 restart

Now you should be able to test if it works, by simply sending a local test E-Mail to user “root”.