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# Pleroma: A lightweight social networking server
# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Signature do
@behaviour HTTPSignatures.Adapter
alias Pleroma.EctoType.ActivityPub.ObjectValidators
alias Pleroma.Keys
alias Pleroma.User
alias Pleroma.Web.ActivityPub.ActivityPub
import Plug.Conn, only: [put_req_header: 3]
@http_signatures_impl Application.compile_env(
:pleroma,
[__MODULE__, :http_signatures_impl],
HTTPSignatures
)
@known_suffixes ["/publickey", "/main-key"]
def key_id_to_actor_id(key_id) do
uri =
key_id
|> URI.parse()
|> Map.put(:fragment, nil)
|> remove_suffix(@known_suffixes)
maybe_ap_id = URI.to_string(uri)
case ObjectValidators.ObjectID.cast(maybe_ap_id) do
{:ok, ap_id} ->
{:ok, ap_id}
_ ->
case Pleroma.Web.WebFinger.finger(maybe_ap_id) do
{:ok, %{"ap_id" => ap_id}} -> {:ok, ap_id}
_ -> {:error, maybe_ap_id}
end
end
end
defp remove_suffix(uri, [test | rest]) do
if not is_nil(uri.path) and String.ends_with?(uri.path, test) do
Map.put(uri, :path, String.replace(uri.path, test, ""))
else
remove_suffix(uri, rest)
end
end
defp remove_suffix(uri, []), do: uri
def fetch_public_key(conn) do
with {:ok, actor_id} <- get_actor_id(conn),
{:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
{:ok, public_key}
else
e ->
{:error, e}
end
end
def refetch_public_key(conn) do
with {:ok, actor_id} <- get_actor_id(conn),
{:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id),
{:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
{:ok, public_key}
else
e ->
{:error, e}
end
end
def get_actor_id(conn) do
with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
{:ok, actor_id} <- key_id_to_actor_id(kid) do
{:ok, actor_id}
else
e ->
{:error, e}
end
end
def sign(%User{keys: keys} = user, headers) do
with {:ok, private_key, _} <- Keys.keys_from_pem(keys) do
HTTPSignatures.sign(private_key, user.ap_id <> "#main-key", headers)
end
end
def signed_date, do: signed_date(NaiveDateTime.utc_now())
def signed_date(%NaiveDateTime{} = date) do
Timex.format!(date, "{WDshort}, {0D} {Mshort} {YYYY} {h24}:{m}:{s} GMT")
end
@spec validate_signature(Plug.Conn.t(), String.t()) :: boolean()
def validate_signature(%Plug.Conn{} = conn, request_target) do
# Newer drafts for HTTP signatures now use @request-target instead of the
# old (request-target). We'll now support both for incoming signatures.
conn =
conn
|> put_req_header("(request-target)", request_target)
|> put_req_header("@request-target", request_target)
@http_signatures_impl.validate_conn(conn)
end
@spec validate_signature(Plug.Conn.t()) :: boolean()
def validate_signature(%Plug.Conn{} = conn) do
# This (request-target) is non-standard, but many implementations do it
# this way due to a misinterpretation of
# https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-06
# "path" was interpreted as not having the query, though later examples
# show that it must be the absolute path + query. This behavior is kept to
# make sure most software (Pleroma itself, Mastodon, and probably others)
# do not break.
request_target = Enum.join([String.downcase(conn.method), conn.request_path], " ")
# This is the proper way to build the @request-target, as expected by
# many HTTP signature libraries, clarified in the following draft:
# https://www.ietf.org/archive/id/draft-ietf-httpbis-message-signatures-11.html#section-2.2.6
# It is the same as before, but containing the query part as well.
proper_target = Enum.join([request_target, "?", conn.query_string], "")
cond do
# Normal, non-standard behavior but expected by Pleroma and more.
validate_signature(conn, request_target) ->
true
# Has query string and the previous one failed: let's try the standard.
conn.query_string != "" ->
validate_signature(conn, proper_target)
# If there's no query string and signature fails, it's rotten.
true ->
false
end
end
end

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