digit

digit 👉

WebFinger for Go

Digit implements the WebFinger protocol. It includes type definitions for WebFinger data structures, along with some utilities for sending and receiving WebFinger requests

Generating WebFinger Data

Digit provides data types with a simple, chainable API for creating new resources.

resource := digit.NewResource("acct:sarah@sky.net").
	Alias("http://sky.net/sarah").
	Alias("http://other.website.com/sarah-connor").
	Property("http://sky.net/ns/role", "employee").
	Link(RelationTypeProfile, "text/html", "https://sky.net/sarah")

result, err := json.Marshal(resource)

Retrieving WebFinger Data

Digit can look up WebFinger metadata using a variety of identifiers

resource, err := digit.Lookup("sarah@sky.net") // Email construction
resource, err := digit.Lookup("sarah@sky.net") // Fediverse "@username" construction
resource, err := digit.Lookup("http://sky.net/sarah") // Canonical URL construction

What matters here

A handful of non-obvious behaviors that bite if you don't know them:

• Lookup blocks private/loopback IPs by default. It uses benpate/remote, whose SSRF guard refuses to connect to non-public addresses unless AllowPrivateIPs(true) is set. This is correct for production (WebFinger queries arbitrary hosts), but tests against a 127.0.0.1 httptest server must pass a remote.Option that flips the guard — otherwise the request fails before it is sent.

• NewLink silently moves Href into Template for two relation types. For oStatus subscribe requests (RelationTypeSubscribeRequest) and FEP-3b86 intent links (RelationTypeFEP3b86Prefix), the constructed Link has an empty Href and the URL in Template instead. Read Template, not Href, for those links.

• LinkSet mutators change the slice in place. Remove, RemoveBy, Apply, and ApplyBy rewrite the receiver's backing array, so any other slice header aliasing the same data will be corrupted. Clone first if you need an independent copy. Note also the asymmetry: Remove deletes all matches; RemoveBy deletes only the first.

• The chainable builder methods return copies; the Set/LinkSet methods mutate. Resource.Alias/Property/Link and Link.Title/Property take value receivers and return a modified copy (safe to chain). The *LinkSet and Link.SetString methods take pointer receivers and mutate.

WebFinger Resources

• https://webfinger.net - primary website for WebFinger protocol
• https://tools.ietf.org/html/rfc7033 - IETF specification

Pull Requests Welcome

Digit is relatively stable and is performing well in Emissary. However, it is still a work in progress, and will benefit from your experience reports, use cases, and contributions. If you have an idea for making this library better, send in a pull request. We're all in this together! 👉