akkoma/lib/pleroma/web/web_finger.ex

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# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Web.WebFinger do
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alias Pleroma.HTTP
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alias Pleroma.User
alias Pleroma.Web.Endpoint
alias Pleroma.Web.Federator.Publisher
alias Pleroma.Web.XML
alias Pleroma.XmlBuilder
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require Jason
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require Logger
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def host_meta do
base_url = Endpoint.url()
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{
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:XRD,
%{xmlns: "http://docs.oasis-open.org/ns/xri/xrd-1.0"},
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{
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:Link,
%{
rel: "lrdd",
type: "application/xrd+xml",
template: "#{base_url}/.well-known/webfinger?resource={uri}"
}
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}
}
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|> XmlBuilder.to_doc()
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end
def webfinger(resource, fmt) when fmt in ["XML", "JSON"] do
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host = Pleroma.Web.Endpoint.host()
regex =
if webfinger_domain = Pleroma.Config.get([__MODULE__, :domain]) do
~r/(acct:)?(?<username>[a-z0-9A-Z_\.-]+)@(#{host}|#{webfinger_domain})/
else
~r/(acct:)?(?<username>[a-z0-9A-Z_\.-]+)@#{host}/
end
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with %{"username" => username} <- Regex.named_captures(regex, resource),
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%User{} = user <- User.get_cached_by_nickname(username) do
{:ok, represent_user(user, fmt)}
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else
_e ->
with %User{} = user <- User.get_cached_by_ap_id(resource) do
{:ok, represent_user(user, fmt)}
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else
_e ->
{:error, "Couldn't find user"}
end
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end
end
defp gather_links(%User{} = user) do
[
%{
"rel" => "http://webfinger.net/rel/profile-page",
"type" => "text/html",
"href" => user.ap_id
}
] ++ Publisher.gather_webfinger_links(user)
end
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defp gather_aliases(%User{} = user) do
[user.ap_id]
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end
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def represent_user(user, "JSON") do
%{
"subject" => "acct:#{user.nickname}@#{domain()}",
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"aliases" => gather_aliases(user),
"links" => gather_links(user)
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}
end
def represent_user(user, "XML") do
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aliases =
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user
|> gather_aliases()
|> Enum.map(&{:Alias, &1})
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links =
gather_links(user)
|> Enum.map(fn link -> {:Link, link} end)
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{
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:XRD,
%{xmlns: "http://docs.oasis-open.org/ns/xri/xrd-1.0"},
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[
{:Subject, "acct:#{user.nickname}@#{domain()}"}
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] ++ aliases ++ links
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}
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|> XmlBuilder.to_doc()
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end
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def domain do
Pleroma.Config.get([__MODULE__, :domain]) || Pleroma.Web.Endpoint.host()
end
@spec webfinger_from_xml(binary()) :: {:ok, map()} | nil
defp webfinger_from_xml(body) do
with {:ok, doc} <- XML.parse_document(body) do
subject = XML.string_from_xpath("//Subject", doc)
subscribe_address =
~s{//Link[@rel="http://ostatus.org/schema/1.0/subscribe"]/@template}
|> XML.string_from_xpath(doc)
ap_id =
~s{//Link[@rel="self" and @type="application/activity+json"]/@href}
|> XML.string_from_xpath(doc)
data = %{
"subject" => subject,
"subscribe_address" => subscribe_address,
"ap_id" => ap_id
}
{:ok, data}
end
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end
defp webfinger_from_json(body) do
with {:ok, doc} <- Jason.decode(body) 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, "ap_id", link["href"])
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{"application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\"", "self"} ->
Map.put(data, "ap_id", link["href"])
{nil, "http://ostatus.org/schema/1.0/subscribe"} ->
Map.put(data, "subscribe_address", link["template"])
_ ->
Logger.debug("Unhandled type: #{inspect(link["type"])}")
data
end
end)
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{:ok, data}
end
end
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def get_template_from_xml(body) do
xpath = "//Link[@rel='lrdd']/@template"
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with {:ok, doc} <- XML.parse_document(body),
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template when template != nil <- XML.string_from_xpath(xpath, doc) do
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{:ok, template}
end
end
@cachex Pleroma.Config.get([:cachex, :provider], Cachex)
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def find_lrdd_template(domain) do
@cachex.fetch!(:host_meta_cache, domain, fn _ ->
{:commit, fetch_lrdd_template(domain)}
end)
rescue
e -> {:error, "Cachex error: #{inspect(e)}"}
end
defp fetch_lrdd_template(domain) do
# WebFinger is restricted to HTTPS - https://tools.ietf.org/html/rfc7033#section-9.1
meta_url = "https://#{domain}/.well-known/host-meta"
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with {:ok, %{status: status, body: body}} when status in 200..299 <-
HTTP.Backoff.get(meta_url) do
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get_template_from_xml(body)
else
error ->
Logger.warning("Can't find LRDD template in #{inspect(meta_url)}: #{inspect(error)}")
{:error, :lrdd_not_found}
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end
end
defp get_address_from_domain(domain, "acct:" <> _ = encoded_account) when is_binary(domain) do
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case find_lrdd_template(domain) do
{:ok, template} ->
String.replace(template, "{uri}", encoded_account)
_ ->
"https://#{domain}/.well-known/webfinger?resource=#{encoded_account}"
end
end
defp get_address_from_domain(domain, account) when is_binary(domain) do
encoded_account = URI.encode("acct:#{account}")
get_address_from_domain(domain, encoded_account)
end
defp get_address_from_domain(_, _), do: {:error, :webfinger_no_domain}
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@spec finger(String.t()) :: {:ok, map()} | {:error, any()}
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def finger(account) do
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account = String.trim_leading(account, "@")
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domain =
with [_name, domain] <- String.split(account, "@") do
domain
else
_e ->
URI.parse(account).host
end
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with address when is_binary(address) <- get_address_from_domain(domain, account),
{:ok, %{status: status, body: body, headers: headers}} when status in 200..299 <-
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HTTP.Backoff.get(
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address,
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[{"accept", "application/xrd+xml,application/jrd+json"}]
) do
case List.keyfind(headers, "content-type", 0) do
{_, content_type} ->
case Plug.Conn.Utils.media_type(content_type) do
{:ok, "application", subtype, _} when subtype in ~w(xrd+xml xml) ->
webfinger_from_xml(body)
{:ok, "application", subtype, _} when subtype in ~w(jrd+json json) ->
webfinger_from_json(body)
_ ->
{:error, {:content_type, content_type}}
end
_ ->
{:error, {:content_type, nil}}
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end
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|> case do
{:ok, data} -> validate_webfinger(address, data)
error -> error
end
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else
error ->
Logger.debug("Couldn't finger #{account}: #{inspect(error)}")
error
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end
end
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defp validate_webfinger(request_url, %{"subject" => "acct:" <> acct = subject} = data) do
with [_name, acct_host] <- String.split(acct, "@"),
{_, url} <- {:address, get_address_from_domain(acct_host, subject)},
%URI{host: request_host} <- URI.parse(request_url),
%URI{host: acct_host} <- URI.parse(url),
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{_, true} <- {:hosts_match, acct_host == request_host} do
{:ok, data}
else
_ -> {:error, {:webfinger_invalid, request_url, data}}
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end
end
defp validate_webfinger(url, data), do: {:error, {:webfinger_invalid, url, data}}
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end