go-jammin' 🥞

Go module brainbaking.com/go-jamming:

A minimalistic Go-powered jamstack-augmented microservice for webmentions etc

✅️ This is a fork of serve-my-jams, the Node-powered original microservice, which is no longer being maintained.

Are you looking for a way to DO something with this? See https://github.com/wgroeneveld/jam-my-stack !

This is a set of minimalistic Go-based microservices that aid you in your IndieWeb Jamstack coolness 😎 (name-dropping). While jam-my-stack is a set of scripts used to run at checkin-time, this is a dymamic service that handles requests.

Inspect how it's used on https://brainbaking.com/ - usually, a <link/> in your <head/> suffices:

<link rel="webmention" href="https://jam.brainbaking.com/webmention" />
<link rel="pingback" href="https://webmention.io/webmention?forward=https://jam.brainbaking.com/webmention" />

If you want to support the older pingback protocol, you can leverage webmenton.io's forward capabilities. Although I developed this primarily because webmention.io is not reliable - you've been warned.

Building and running

Well, that's easy!

1. Build: go build
2. Run: ./go-jamming
3. ???
4. Profit!

It's very much a fire-and-forget thing. Put it behind a reverse proxy such as nginx using something like this:

server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;

        server_name [your-domain];

        location / {
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $remote_addr;
                proxy_set_header Host $host;
                proxy_pass http://127.0.0.1:[your-port];
        }
    ssl_certificate /etc/letsencrypt/live/[your-domain]/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/[your-domain]/privkey.pem;
}

Create a very simple Linux system service that fires up the jam:

[Unit]
Description=Go-Jamming
After=network.target

[Service]
User=[myuser]
WorkingDirectory=/var/www/gojamming
ExecStart=/var/www/gojamming/go-jamming
SuccessExitStatus=0

[Install]
WantedBy=multi-user.target

Now install using sudo systemctl enable/install gojamming and you're done!

Configuration

Place a config.json file in the same directory that looks like this: (below are the default values)

{
  "port": 1337,
  "host": "localhost",
  "token": "miauwkes",
  "dataPath": "data",
  "utcOffset": 60,
  "allowedWebmentionSources":  [
    "brainbaking.com",
    "jefklakscodex.com"
  ],
  "disallowedWebmentionDomains":  [
    "youtube.com"
  ]
}

• port, host: http server params
• token, allowedWebmentionSources: see below, used for authentication
• utcOffset: offset in minutes for date processing, starting from UTC time.
• dataPath: path to store all mentions as md5-encoded JSON filenames.

If a config file is missing, or required keys are missing, a warning will be generated and default values will be used instead. See common/config.go.

---

What's in it?

1. Webmentions

1.1 POST /webmention

Receive a webmention. Includes a lot of cross-checking and validating to guard against possible spam. See the W3C WebMention spec - or the source - for details.

Accepted form format:

    POST /webmention-endpoint HTTP/1.1
    Host: aaronpk.example
    Content-Type: application/x-www-form-urlencoded

    source=https://waterpigs.example/post-by-barnaby&
    target=https://aaronpk.example/post-by-aaron

Will result in a 202 Accepted - it handles things async. Stores in .json files in [dataPath]/domain.

1.2 GET /webmention/:domain/:token

Retrieves a JSON array with relevant webmentions stored for that domain. The token should match. See configuration to fiddle with it yourself. Environment variables are supported, although I haven't used them yet.

1.3 PUT /webmention/:domain/:token

Sends out both webmentions and pingbacks, based on the domain's index.xml RSS feed, and optionally, a since request query parameter that is supposed to be a string, fed through Dayjs to format. (e.g. 2021-03-16T16:00:00.000Z).

This does a couple of things:

1. Fetch RSS entries (since x, or everything)
2. Find outbound hrefs (starting with http)
3. Check if those domains have a webmention link endpoint installed, according to the w3.org rules. If not, check for a pingback endpoint. If not, bail out.
4. If webmention/pingback found: POST for each found href with source the own domain and target the outbound link found in the RSS feed, using either XML or form data according to the protocol.

As with the POST call, will result in a 202 Accepted and handles things async/in parallel.

Does this thing take updates into account?

Yes and no. It checks the <pubDate/> <item/> RSS tag by default. I decided against porting the more complicated <timestamp/> HTML check as it would only spam possible receivers. So if you consider your article to be updated, you should also update the publication date!

2. Pingbacks

Pingbacks are in here for two reasons:

1. I wanted to see how difficult it was to implement them. Turns out to be almost exactly the same as webmentions. This means the "new" W3 standards for webmentions are just as crappy as pingbacks... What's the difference between a form POST and an XML POST? Form factor?
2. Much more blogs (Wordpress-alike) support only pingbacks.

2.1 POST /pingback

Receive a pingback. Includes a lot of cross-checking and validating to guard against possible spam. Internally, converts it into a webmention and processes it just like that.

Accepted XML body:

<?xml version="1.0" encoding="UTF-8"?>
<methodCall>
    <methodName>pingback.ping</methodName>
    <params>
        <param>
            <value><string>https://brainbaking.com/kristien.html</string></value>
        </param>
        <param>
            <value><string>https://kristienthoelen.be/2021/03/22/de-stadia-van-een-burn-out-in-welk-stadium-zit-jij/</string></value>
        </param>
    </params>
</methodCall>

Will result in a 200 OK - that returns XML according to The W3 pingback XML-RPC spec. Processes async.

2.2 Sending pingbacks

Happens automatically through PUT /webmention/:domain/:token! Links that are discovered as rel="pingback" that do not already have a webmention link will be processed as XML-RPC requests to be send.

Troubleshooting

Run in verbose mode: use -verbose. This also logs debug info. Structured JSON is outputted through os.Stderr - which is usually /var/log/syslog.

If rolling files in a separate location is required, lumberjack could be added in main.go.

There's a rate limiting system implemented with a rate limit of 5 requests per second and a maximum burst rate of 10. That's pretty flexible. I have not taken the trouble to put this into the config, it should do in most cases. If you get a 429 too many requests, you've hit the limiter. A separate goroutine cleans up ips each 2 minutes, the TTL is 5 minutes. See limiter.go.