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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.WebFinger do
   6   alias Pleroma.HTTP
   7   alias Pleroma.User
   8   alias Pleroma.Web.Endpoint
   9   alias Pleroma.Web.Federator.Publisher
  10   alias Pleroma.Web.XML
  11   alias Pleroma.XmlBuilder
  12   require Jason
  13   require Logger
  14
  15   def host_meta do
  16     base_url = Endpoint.url()
  17
  18     {
  19       :XRD,
  20       %{xmlns: "http://docs.oasis-open.org/ns/xri/xrd-1.0"},
  21       {
  22         :Link,
  23         %{
  24           rel: "lrdd",
  25           type: "application/xrd+xml",
  26           template: "#{base_url}/.well-known/webfinger?resource={uri}"
  27         }
  28       }
  29     }
  30     |> XmlBuilder.to_doc()
  31   end
  32
  33   def webfinger(resource, fmt) when fmt in ["XML", "JSON"] do
  34     host = Pleroma.Web.Endpoint.host()
  35
  36     regex =
  37       if webfinger_domain = Pleroma.Config.get([__MODULE__, :domain]) do
  38         ~r/(acct:)?(?<username>[a-z0-9A-Z_\.-]+)@(#{host}|#{webfinger_domain})/
  39       else
  40         ~r/(acct:)?(?<username>[a-z0-9A-Z_\.-]+)@#{host}/
  41       end
  42
  43     with %{"username" => username} <- Regex.named_captures(regex, resource),
  44          %User{} = user <- User.get_cached_by_nickname(username) do
  45       {:ok, represent_user(user, fmt)}
  46     else
  47       _e ->
  48         with %User{} = user <- User.get_cached_by_ap_id(resource) do
  49           {:ok, represent_user(user, fmt)}
  50         else
  51           _e ->
  52             {:error, "Couldn't find user"}
  53         end
  54     end
  55   end
  56
  57   defp gather_links(%User{} = user) do
  58     [
  59       %{
  60         "rel" => "http://webfinger.net/rel/profile-page",
  61         "type" => "text/html",
  62         "href" => user.ap_id
  63       }
  64     ] ++ Publisher.gather_webfinger_links(user)
  65   end
  66
  67   defp gather_aliases(%User{} = user) do
  68     [user.ap_id | user.also_known_as]
  69   end
  70
  71   def represent_user(user, "JSON") do
  72     %{
  73       "subject" => "acct:#{user.nickname}@#{domain()}",
  74       "aliases" => gather_aliases(user),
  75       "links" => gather_links(user)
  76     }
  77   end
  78
  79   def represent_user(user, "XML") do
  80     aliases =
  81       user
  82       |> gather_aliases()
  83       |> Enum.map(&{:Alias, &1})
  84
  85     links =
  86       gather_links(user)
  87       |> Enum.map(fn link -> {:Link, link} end)
  88
  89     {
  90       :XRD,
  91       %{xmlns: "http://docs.oasis-open.org/ns/xri/xrd-1.0"},
  92       [
  93         {:Subject, "acct:#{user.nickname}@#{domain()}"}
  94       ] ++ aliases ++ links
  95     }
  96     |> XmlBuilder.to_doc()
  97   end
  98
  99   defp domain do
 100     Pleroma.Config.get([__MODULE__, :domain]) || Pleroma.Web.Endpoint.host()
 101   end
 102
 103   defp webfinger_from_xml(body) do
 104     with {:ok, doc} <- XML.parse_document(body) do
 105       subject = XML.string_from_xpath("//Subject", doc)
 106
 107       subscribe_address =
 108         ~s{//Link[@rel="http://ostatus.org/schema/1.0/subscribe"]/@template}
 109         |> XML.string_from_xpath(doc)
 110
 111       ap_id =
 112         ~s{//Link[@rel="self" and @type="application/activity+json"]/@href}
 113         |> XML.string_from_xpath(doc)
 114
 115       data = %{
 116         "subject" => subject,
 117         "subscribe_address" => subscribe_address,
 118         "ap_id" => ap_id
 119       }
 120
 121       {:ok, data}
 122     end
 123   end
 124
 125   defp webfinger_from_json(body) do
 126     with {:ok, doc} <- Jason.decode(body) do
 127       data =
 128         Enum.reduce(doc["links"], %{"subject" => doc["subject"]}, fn link, data ->
 129           case {link["type"], link["rel"]} do
 130             {"application/activity+json", "self"} ->
 131               Map.put(data, "ap_id", link["href"])
 132
 133             {"application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\"", "self"} ->
 134               Map.put(data, "ap_id", link["href"])
 135
 136             {nil, "http://ostatus.org/schema/1.0/subscribe"} ->
 137               Map.put(data, "subscribe_address", link["template"])
 138
 139             _ ->
 140               Logger.debug("Unhandled type: #{inspect(link["type"])}")
 141               data
 142           end
 143         end)
 144
 145       {:ok, data}
 146     end
 147   end
 148
 149   def get_template_from_xml(body) do
 150     xpath = "//Link[@rel='lrdd']/@template"
 151
 152     with {:ok, doc} <- XML.parse_document(body),
 153          template when template != nil <- XML.string_from_xpath(xpath, doc) do
 154       {:ok, template}
 155     end
 156   end
 157
 158   def find_lrdd_template(domain) do
 159     # WebFinger is restricted to HTTPS - https://tools.ietf.org/html/rfc7033#section-9.1
 160     meta_url = "https://#{domain}/.well-known/host-meta"
 161
 162     with {:ok, %{status: status, body: body}} when status in 200..299 <- HTTP.get(meta_url) do
 163       get_template_from_xml(body)
 164     else
 165       error ->
 166         Logger.warn("Can't find LRDD template in #{inspect(meta_url)}: #{inspect(error)}")
 167         {:error, :lrdd_not_found}
 168     end
 169   end
 170
 171   defp get_address_from_domain(domain, encoded_account) when is_binary(domain) do
 172     case find_lrdd_template(domain) do
 173       {:ok, template} ->
 174         String.replace(template, "{uri}", encoded_account)
 175
 176       _ ->
 177         "https://#{domain}/.well-known/webfinger?resource=#{encoded_account}"
 178     end
 179   end
 180
 181   defp get_address_from_domain(_, _), do: {:error, :webfinger_no_domain}
 182
 183   @spec finger(String.t()) :: {:ok, map()} | {:error, any()}
 184   def finger(account) do
 185     account = String.trim_leading(account, "@")
 186
 187     domain =
 188       with [_name, domain] <- String.split(account, "@") do
 189         domain
 190       else
 191         _e ->
 192           URI.parse(account).host
 193       end
 194
 195     encoded_account = URI.encode("acct:#{account}")
 196
 197     with address when is_binary(address) <- get_address_from_domain(domain, encoded_account),
 198          {:ok, %{status: status, body: body, headers: headers}} when status in 200..299 <-
 199            HTTP.get(
 200              address,
 201              [{"accept", "application/xrd+xml,application/jrd+json"}]
 202            ) do
 203       case List.keyfind(headers, "content-type", 0) do
 204         {_, content_type} ->
 205           case Plug.Conn.Utils.media_type(content_type) do
 206             {:ok, "application", subtype, _} when subtype in ~w(xrd+xml xml) ->
 207               webfinger_from_xml(body)
 208
 209             {:ok, "application", subtype, _} when subtype in ~w(jrd+json json) ->
 210               webfinger_from_json(body)
 211
 212             _ ->
 213               {:error, {:content_type, content_type}}
 214           end
 215
 216         _ ->
 217           {:error, {:content_type, nil}}
 218       end
 219     else
 220       error ->
 221         Logger.debug("Couldn't finger #{account}: #{inspect(error)}")
 222         error
 223     end
 224   end
 225 end