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Posts for year 2021

New maintainers needed for the Thunderbird Lookout Fix-version add-on

Lookout! In august 2018 I took over maintenance of the Thunderbird addon [Lookout-fix-version][e7c45433]. I soon set up a the Github Organization TB-throwback so that future development can be expanded and transferred easier if I stop work on it.

LookOut Fix-Version is a plugin which allows Thunderbird to interface with Microsoft’s mail tools by decoding metadata and attachments encapsulated/embedded in a TNEF (Transport Neutral Encapsulation Format) encoded attachment (aka winmail.dat).

Transport Neutral Encapsulation Format or TNEF is a proprietary email attachment format used by Microsoft Outlook and Microsoft Exchange Server. An attached file with TNEF encoding is most often named winmail.dat or win.dat, and has a MIME type of Application/MS-TNEF. The official (IANA) media type, however, is application/vnd.ms-tnef. Source: https://en.wikipedia.org/wiki/Transport_Neutral_Encapsulation_Format

Unfortunately I had to stop working on Lookout a while ago because my employer switched us back to Outlook leaving me with no company time to maintain the project any more. The last major release of Thunderbird I received a lot of help from the TB team's John Bieling to bootstrap a workaround to get things rolling again, now Thunderbird 91 is coming and it's another case of the old xul add-ons not working in the webextension world.

After receiving no takers to my maintainer request over on the mailing list I have decided if I am unable to locate new maintainers I will archive the project on Github. I hope the Thunderbird devs finally assign Bug 77811 to someone as I know that proper integration for decoding TNEF emails was added to the roadmap, however in the meantime you are interested in updating the project please let me know as I'll actively be monitoring the Github project and the issue calling for new maintainers


I shouldn't use sudo nano

Over on /r/linux a user going by /u/AlternOSx posted a short You should Know: YSK : Do not use 'sudo vim/nano/emacs..' to edit a file. Instead, set your $EDITOR and use sudoedit or sudo -e.

Long story short sudoedit copies the file you want to edit to /tmp/file.xxx and then opens it with an unprivileged instance of your editor of choice. It then overwrites the source file when you are finished editing, protecting from accidental privilege escalation of commands through your text editor.

Knowing this I came up with a quick way to enforce this best practice by added this function into my .bashrc file. Hopefully I can retrain myself not to use sudo nano all the time.

# Define the default editor in this case nano.
EDITOR=nano

# Catch calls to sudo.
function sudo() {
  if [[ $1 == "$EDITOR" ]]; then
    # The editor has been called

    if [ -w "$2" ]; then
      # If the file is writable by the current user just use the editor as normal.

      command $EDITOR "$2"
    else
      # The file is not writable use sudoedit.
      command sudoedit "$2"
    fi
  else
    # Use sudo as normal.
    command /usr/bin/sudo "[email protected]"
  fi
}

Caving and switching to Amazon SES

Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email entered limited use in the 1960s, but users could only send to users of the same computer, and some early email systems required the author and the recipient to both be online simultaneously, similar to instant messaging. Ray Tomlinson is credited as the inventor of email; in 1971, he developed the first system able to send mail between users on different hosts across the ARPANET, using the @ sign to link the user name with a destination server. By the mid-1970s, this was the form recognized as email. For almost 7 years I have run my own email server sending and receiving emails on it's own IP address. A few years ago I switched to Digital Ocean as a VPS to reduce deliverability issues, recently the IP block I was in got blacklisted by zen.spamhaus. The age of my 100% independent email server is now over.

Big players make it hard for small servers

As outlined with this blog post Google is eating out email and the resulting discussion on Hacker News the big players appear to have no interest following the standard rules when it comes to emails. All the tools are designed for big users, Google and Microsofts's postmaster tools don't even register any statistics for a domain unless your sending over 200 emails a day.

Unfortunately we find ourselves in the same position when it comes to something as simple as an SMTP relay service. If you search online for what an SMTP relay is you will only see the marketing material that claims it is a tool for large marketers to deliver massive volumes of emails into the inbox of their customers. Not what it actually is, a forwarding service that allows multiple email servers to send from one IP address to outsource reputation management.

Clearly the main advantage of an SMTP relay should be small time servers can pool together to achieve the volume the big players want to see to be able to judge if your emails are "worthy" of being treated fairly.

Imagine my frustration when trying to find any service that directly caters to this and finding that they don't appear to exist. It's all pitched as a service for marketing email delivery, if you're not sending thousands of emails you are not the target market anymore.

Can I use Mailgun for my personal email address?

It’s not recommended.

There are plenty of hosted email services better suited for this than Mailgun; Rackspace Email, Gmail / Google Apps, Outlook, etc.

Mailgun is meant to be a tool for developers and their applications.

Fair enough if you don't have a personal email server but if you have a server used by a family? Not clear. Then when you do sign up for any SMTP service they ask for your Business name, website and business use.

In the end as I technically have donations listed on the about page of this blog I simply used that and the Transactional emails from my Nextcloud instance as a sample of what I would be sending.

Getting out of the sandbox was a thing

I initially tried signing up for SendGrid but they immediately lock new accounts and you have to contact support to even login, let alone send an email. So after they straight up ignored what I wrote in the support email I signed up with AWS then immediately discovered that even though I could log in and set things up I was isolated in a sandbox not allowed to play with the other children.

Even though when signing up I selected an Individual account for side projects they still wanted a business use. After I finished banging my head against the desk I submitted what info I could. After four emails where among other things I updated my Privacy policy page to include Opt-in/out language, I was denied.

We reviewed your request and determined that your use of Amazon SES could have a negative impact on our service. We are denying this request to prevent other Amazon SES customers from experiencing interruptions in service.

There was one chance. In the correspondence they asked very specifically

How do you handle bounces and complaints?

Given they appeared to be concerned with negative service impacts I discovered a method of Automating handling this based on this xenforo plugin. Using Node-red as an endpoint I can receive a notification of a bounce/complaint and shut down the server for manual review.

Informing Amazon of this change was enough to get through the bureaucratic hurdles .

Making the switch was easy at least

Thankfully this was the least of my issues. First I created an SMTP identity in AWS, added that to my postfix postfix-relaymap.cf and postfix-sasl-password.cf as outlined in docker-mailserver documentation. Add the Amazon domain key, SPF record and CNAME records for DKIM and I was off to the races.


Minimizing my selfhosted attack surface

Tweeking my linux server I'm always fairly wary of opening my selfhosted services up to the internet, just how sure am I that the developer has done the right due-diligence? Thankfully it's relatively simple to at least limit parts of a service accessible to the open internet with Nginx and allow and deny options.


Update

Note: If you want a docker container to access a protected service you will have to set the subnet in your docker-compose file as below:

networks:
  node-red-network:
    ipam:
      config:
        - subnet: "172.16.0.0/24"

Update 2

A more generic change you can do is set the default address pools in docker's /etc/docker/daemon.json file. You then just have to whitelist 172.16.0.0/16 subnets

{
  "default-address-pools":
  [
    {"base":"172.16.0.0/16","size":24}
  ]
}

First you should store this in a file, that way you can then include it multiple times, this will make it trivial to update in the future. Create the file include_whitelist in your nginx folder, adding your own allow options between satisfy any; and deny all;.

satisfy any;

# allow localhost
allow 127.0.0.1;

# allow a single address
# allow 000.000.000.000;

# allow LAN network
allow 192.168.0.0/24;

# allow WLAN network
allow 192.168.2.0/24;

# allow VPN network
allow 10.1.4.0/24;

# drop rest of the world
deny all;

You then have to include the file in your nginx config. Here I am using TT-RSS as an example, Note that I'm excluding the API and the public.php by having it in a separate location block without including the include_whitelist. This allows me to keep accessing TT-RSS on my mobile phone through the mobile application.

  location ^~ /tt-rss/ {
      include /etc/nginx/include_whitelist;

      access_log off;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $remote_addr;
      proxy_set_header X-Forwarded-Proto $scheme;
      proxy_pass http://127.0.0.1:8280/tt-rss/;

  }

  location ^~ /tt-rss/api {

      access_log off;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $remote_addr;
      proxy_set_header X-Forwarded-Proto $scheme;
      proxy_pass http://127.0.0.1:8280/tt-rss/api;

  }

  location ^~ /tt-rss/public.php {

      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $remote_addr;
      proxy_set_header X-Forwarded-Proto $scheme;
      proxy_pass http://127.0.0.1:8280/tt-rss/public.php;

  }

For Node-Red I wanted an API endpoint for Tasker on my phone. Thankfully this is just as easy to define in Node-red as it is in nginx. In Node-Red open your GET node and just add another folder.

Add and extra folder to your Node-Red endpoints

An example of the Node-Red nginx configuration. Again just like the TT-RSS example above, I have excluded an api subdirectory by having a separate location block.

  location ^~ /node-red/ {
    include /etc/nginx/include_whitelist;

    proxy_set_header Host $http_host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_pass http://127.0.0.1:1880/node-red/;
  }

  location ^~ /node-red/api/ {
    proxy_set_header Host $http_host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_pass http://127.0.0.1:1880/node-red/api/;
  }

Now only your API endpoints are globally available. If like me you use a firewall, throwing a convenient geo-block up in front you can lower the exposure a bit more.


Removing 3g modem from a Kindle Paperwhite 2

Why do I need the cloud? Do I need the cloud connectivity on my kindle everywhere I go? Probably not.

A few years ago I received an old Kindle 3g Paperwhite 2 (2013) 6th from my mother. She wasn't a fan of the screen and decided she preferred a full tablet for reading while I quickly fell in love with the e-ink screen. However my use-case involves mainly e-novels/websites I scrape and upload via Calibre. Given how privacy conscious I have become, and how much of a power drain a 3g modem can be, I've basically had it in airplane mode since I received it.

But walking to my desktop to sync books when the device has wifi capability felt wasteful. Searches on the internet proved fruitless on ways to disable the 3g.

Modular hardware

While searching for a teardown video to determine what the internals even looked like I stumbled upon this video for an older kindle model where it was pointed out how modular Kindle hardware really is. After seeing the wifi paperwhite internals and seeing this video I felt it was likely they were still utilizing this modular design method (after all, if it works), so I cracked open my kindle following this ifixit guide.

Well that was simpler than it looked

Thankfully removing the 3g modem is a non-destructive process (apart from the glue when removing the bezel).

Kindle paperwhite 2 internals

  1. Is the 3g antenna - I didn't remove this.
  2. Is the 3g modem - Held in by 4 screws and attached with a tiny connection plug.
  3. Is simcard slot - Simply push the tray lid in the direction of the arrow to open.

3g Modem removed

  1. Is the 3g antenna connector - This is a simple push connector. A firm pull up away from the board will disconnect this without damage. I used some tape to secure the wire for re-assembly
  2. A loose metal washer, I secured this back in place with the screw I removed previously.
  3. A loose metal washer, I secured this back in place with the screw I removed previously.

Re-assembly

This was simply a matter of re-placing the board, screws and lightly clamping the bezel back in place. The glue on the bezel was, thankfully, still sticky enough to re-attach without any issue. As the bezel has no mechanical stresses on it I don't see this ever being and issue.

My next steps

My next steps where to jailbreak/root my kindle to install a couple of useful tools (i.e. a firewall). I plan to go over this in detail along with my remote book managment solution in another post so Stay tuned.