mobilizon/lib/federation/web_finger/web_finger.ex

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# Portions of this file are derived from Pleroma:
# Copyright © 2017-2018 Pleroma Authors <https://pleroma.social>
# SPDX-License-Identifier: AGPL-3.0-only
# Upstream: https://git.pleroma.social/pleroma/pleroma/blob/develop/lib/pleroma/web/web_finger/web_finger.ex
defmodule Mobilizon.Federation.WebFinger do
@moduledoc """
2020-01-22 01:14:42 +00:00
Performs the WebFinger requests and responses (JSON only).
"""
alias Mobilizon.Actors
alias Mobilizon.Actors.Actor
alias Mobilizon.Federation.ActivityPub.Actor, as: ActivityPubActor
alias Mobilizon.Federation.WebFinger.XmlBuilder
alias Mobilizon.Service.HTTP.{HostMetaClient, WebfingerClient}
alias Mobilizon.Web.Endpoint
alias Mobilizon.Web.Router.Helpers, as: Routes
require Jason
require Logger
import SweetXml
@doc """
Returns the Web Host Metadata (for `/.well-known/host-meta`) representation for the instance, following RFC6414.
"""
@spec host_meta :: String.t()
def host_meta do
base_url = Endpoint.url()
%URI{host: host} = URI.parse(base_url)
XmlBuilder.to_doc({
:XRD,
%{
xmlns: "http://docs.oasis-open.org/ns/xri/xrd-1.0",
"xmlns:hm": "http://host-meta.net/ns/1.0"
},
[
{
:"hm:Host",
host
},
{
:Link,
%{
rel: "lrdd",
type: "application/jrd+json",
template: "#{base_url}/.well-known/webfinger?resource={uri}"
}
}
]
})
end
@doc """
Returns the Webfinger representation for the instance, following RFC7033.
"""
@spec webfinger(String.t(), String.t()) :: {:ok, map} | {:error, :actor_not_found}
def webfinger(resource, "JSON") do
host = Endpoint.host()
regex = ~r/(acct:)?(?<name>\w+)@#{host}/
with %{"name" => name} <- Regex.named_captures(regex, resource),
%Actor{} = actor <- Actors.get_local_actor_by_name(name) do
{:ok, represent_actor(actor, "JSON")}
else
_e ->
case ActivityPubActor.get_or_fetch_actor_by_url(resource) do
{:ok, %Actor{} = actor} when not is_nil(actor) ->
{:ok, represent_actor(actor, "JSON")}
_e ->
{:error, :actor_not_found}
end
end
end
@doc """
Return an `Mobilizon.Actors.Actor` Webfinger representation (as JSON)
"""
@spec represent_actor(Actor.t(), String.t()) :: map()
def represent_actor(%Actor{} = actor, "JSON") do
links =
[
%{"rel" => "self", "type" => "application/activity+json", "href" => actor.url},
%{
"rel" => "http://ostatus.org/schema/1.0/subscribe",
"template" => "#{Routes.page_url(Endpoint, :interact, uri: nil)}{uri}"
}
]
|> maybe_add_avatar(actor)
|> maybe_add_profile_page(actor)
%{
"subject" => "acct:#{actor.preferred_username}@#{Endpoint.host()}",
"aliases" => [actor.url],
"links" => links
}
end
@spec maybe_add_avatar(list(map()), Actor.t()) :: list(map())
defp maybe_add_avatar(data, %Actor{avatar: avatar}) when not is_nil(avatar) do
data ++
[
%{
"rel" => "http://webfinger.net/rel/avatar",
"type" => avatar.content_type,
"href" => avatar.url
}
]
end
defp maybe_add_avatar(data, _actor), do: data
@spec maybe_add_profile_page(list(map()), Actor.t()) :: list(map())
defp maybe_add_profile_page(data, %Actor{type: :Group, url: url}) do
data ++
[
%{
"rel" => "http://webfinger.net/rel/profile-page/",
"type" => "text/html",
"href" => url
}
]
end
defp maybe_add_profile_page(data, _actor), do: data
@type finger_errors ::
:host_not_found
| :address_invalid
| :http_error
| :webfinger_information_not_json
| :no_url_in_webfinger_data
@doc """
Finger an actor to retreive it's ActivityPub ID/URL
Fetches the Extensible Resource Descriptor endpoint `/.well-known/host-meta` to find the Webfinger endpoint (usually `/.well-known/webfinger?resource=`) and then performs a Webfinger query to get the ActivityPub ID associated to an actor.
"""
@spec finger(String.t()) ::
{:ok, String.t()}
| {:error, finger_errors}
def finger(actor) do
actor = String.trim_leading(actor, "@")
case validate_endpoint(actor) do
{:ok, address} ->
case fetch_webfinger_data(address) do
{:ok, %{"url" => url}} ->
{:ok, url}
{:ok, _} ->
Logger.debug("No URL found for actor from webfinger data")
{:error, :no_url_in_webfinger_data}
{:error, err} ->
Logger.debug("Couldn't process webfinger data for #{actor}")
{:error, err}
end
{:error, err} ->
Logger.debug("Couldn't find webfinger endpoint for #{actor}")
{:error, err}
end
end
@spec fetch_webfinger_data(String.t()) ::
{:ok, map()} | {:error, :webfinger_information_not_json | :http_error}
defp fetch_webfinger_data(address) do
Logger.debug("Calling WebfingerClient with #{inspect(address)}")
case WebfingerClient.get(address) do
{:ok, %{body: body, status: code}} when code in 200..299 ->
webfinger_from_json(body)
err ->
Logger.debug("Failed to fetch webfinger data #{inspect(err)}")
{:error, :http_error}
end
end
@spec validate_endpoint(String.t()) ::
{:ok, String.t()} | {:error, :address_invalid | :host_not_found}
defp validate_endpoint(actor) do
case apply_webfinger_endpoint(actor) do
address when is_binary(address) ->
if address_invalid(address) do
Logger.info("Webfinger endpoint seems to be an invalid URL #{inspect(address)}")
{:error, :address_invalid}
else
{:ok, address}
end
_ ->
Logger.info("Host not found in actor address #{inspect(actor)}")
{:error, :host_not_found}
end
end
# Fetches the Extensible Resource Descriptor endpoint `/.well-known/host-meta`
# to find the Webfinger endpoint (usually `/.well-known/webfinger?resource=`)
@spec find_webfinger_endpoint(String.t()) ::
{:ok, String.t()} | {:error, :link_not_found} | {:error, any()}
defp find_webfinger_endpoint(domain) when is_binary(domain) do
Logger.debug("Calling HostMetaClient for #{domain}")
with {:ok, %Tesla.Env{status: 200, body: body}} <-
HostMetaClient.get("https://#{domain}/.well-known/host-meta"),
link_template when is_binary(link_template) <- find_link_from_template(body) do
{:ok, link_template}
else
{:ok, %Tesla.Env{status: 404}} -> {:error, :entity_not_found}
{:ok, %Tesla.Env{}} -> {:error, :http_error}
{:error, :link_not_found} -> {:error, :link_not_found}
{:error, error} -> {:error, error}
end
end
@spec apply_webfinger_endpoint(String.t()) :: String.t() | {:error, :host_not_found}
defp apply_webfinger_endpoint(actor) do
with {:ok, domain} <- domain_from_federated_actor(actor) do
case find_webfinger_endpoint(domain) do
{:ok, link_template} ->
Logger.debug("Using webfinger location provided by host-meta endpoint")
String.replace(link_template, "{uri}", "acct:#{actor}")
_ ->
Logger.debug("Using default webfinger location")
"https://#{domain}/.well-known/webfinger?resource=acct:#{actor}"
end
end
end
@spec domain_from_federated_actor(String.t()) :: {:ok, String.t()} | {:error, :host_not_found}
defp domain_from_federated_actor(actor) do
case String.split(actor, "@") do
[_name, domain] ->
{:ok, domain}
_e ->
host = URI.parse(actor).host
if is_nil(host), do: {:error, :host_not_found}, else: {:ok, host}
end
end
@spec webfinger_from_json(map() | String.t()) ::
{:ok, map()} | {:error, :webfinger_information_not_json}
defp webfinger_from_json(doc) when is_map(doc) do
data =
Enum.reduce(doc["links"], %{"subject" => doc["subject"]}, fn link, data ->
case {link["type"], link["rel"]} do
{"application/activity+json", "self"} ->
Map.put(data, "url", link["href"])
{nil, _rel} ->
Logger.debug("No type declared for the following link #{inspect(link)}")
data
_ ->
Logger.debug(fn ->
"Unhandled type to finger: #{inspect(link["type"])}"
end)
data
end
end)
{:ok, data}
end
defp webfinger_from_json(_doc), do: {:error, :webfinger_information_not_json}
@spec find_link_from_template(String.t()) :: String.t() | {:error, :link_not_found}
defp find_link_from_template(doc) do
with res when res in [nil, ""] <-
xpath(doc, ~x"//Link[@rel=\"lrdd\"][@type=\"application/json\"]/@template"s),
res when res in [nil, ""] <- xpath(doc, ~x"//Link[@rel=\"lrdd\"]/@template"s),
do: {:error, :link_not_found}
catch
:exit, _e ->
{:error, :link_not_found}
end
@spec address_invalid(String.t()) :: false | {:error, :invalid_address}
defp address_invalid(address) do
with %URI{host: host, scheme: scheme} <- URI.parse(address),
true <- is_nil(host) or is_nil(scheme) do
{:error, :invalid_address}
end
end
end