mobilizon/lib/federation/http_signatures/signature.ex

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# Portions of this file are derived from Pleroma:
# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social>
# SPDX-License-Identifier: AGPL-3.0-only
# Upstream: https://git.pleroma.social/pleroma/pleroma/blob/develop/lib/pleroma/signature.ex
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defmodule Mobilizon.Federation.HTTPSignatures.Signature do
@moduledoc """
Adapter for the `HTTPSignatures` lib that handles signing and providing public keys to verify HTTPSignatures
"""
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@behaviour HTTPSignatures.Adapter
alias Mobilizon.Actors.Actor
alias Mobilizon.Federation.ActivityPub.Actor, as: ActivityPubActor
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require Logger
@spec key_id_to_actor_url(String.t()) :: String.t()
def key_id_to_actor_url(key_id) do
%URI{path: path} =
uri =
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key_id
|> URI.parse()
|> Map.put(:fragment, nil)
uri =
if is_nil(path) do
uri
else
%URI{uri | path: String.trim_trailing(path, "/publickey")}
end
URI.to_string(uri)
end
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@doc """
Convert internal PEM encoded keys to public key format.
"""
@spec prepare_public_key(String.t()) :: {:ok, tuple} | {:error, :pem_decode_error}
def prepare_public_key(public_key_code) do
case :public_key.pem_decode(public_key_code) do
[public_key_entry] ->
{:ok, :public_key.pem_entry_decode(public_key_entry)}
_ ->
{:error, :pem_decode_error}
end
end
# Gets a public key for a given ActivityPub actor ID (url).
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@spec get_public_key_for_url(String.t()) ::
{:ok, String.t()}
| {:error, :actor_not_found | :pem_decode_error}
defp get_public_key_for_url(url) do
with {:ok, %Actor{} = actor} <-
ActivityPubActor.get_or_fetch_actor_by_url(url, ignore_sign_object_fetches: true) do
get_actor_public_key(actor)
end
end
@spec get_actor_public_key(Actor.t()) :: {:ok, String.t()} | {:error, :pem_decode_error}
defp get_actor_public_key(%Actor{keys: keys}) do
case prepare_public_key(keys) do
{:ok, public_key} ->
{:ok, public_key}
{:error, :pem_decode_error} ->
Logger.error("Error while decoding PEM")
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{:error, :pem_decode_error}
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end
end
@spec fetch_public_key(Plug.Conn.t()) ::
{:ok, String.t()}
| {:error, :actor_not_found | :pem_decode_error | :no_signature_in_conn}
def fetch_public_key(conn) do
case HTTPSignatures.signature_for_conn(conn) do
%{"keyId" => kid} ->
actor_id = key_id_to_actor_url(kid)
Logger.debug("Fetching public key for #{actor_id}")
get_public_key_for_url(actor_id)
_ ->
{:error, :no_signature_in_conn}
end
end
@spec refetch_public_key(Plug.Conn.t()) ::
{:ok, String.t()}
| {:error, :actor_fetch_error | :actor_not_fetchable | :pem_decode_error,
:actor_is_local}
def refetch_public_key(conn) do
%{"keyId" => kid} = HTTPSignatures.signature_for_conn(conn)
actor_url = key_id_to_actor_url(kid)
Logger.debug("Refetching public key for #{actor_url}")
# In this specific case we don't sign object fetches because
# this would cause infinite recursion when servers both need
# to fetch each other's keys
with {:ok, %Actor{} = actor} <-
ActivityPubActor.make_actor_from_url(actor_url, ignore_sign_object_fetches: true) do
get_actor_public_key(actor)
end
end
@spec sign(Actor.t(), map()) :: String.t() | {:error, :pem_decode_error} | no_return
def sign(%Actor{domain: domain, keys: keys, url: url} = actor, headers) when is_nil(domain) do
Logger.debug("Signing a payload on behalf of #{url}")
Logger.debug("headers")
Logger.debug(inspect(headers))
case prepare_public_key(keys) do
{:ok, key} ->
if Application.get_env(:sentry, :dsn) != nil do
Sentry.Context.set_extra_context(%{"actor_url" => url})
end
HTTPSignatures.sign(key, url <> "#main-key", headers)
{:error, :pem_decode_error} ->
raise ArgumentError, message: "Failed to prepare public keys for #{actor.url}"
end
end
def sign(%Actor{url: url}, _) do
Logger.error("Can't do a signature on remote actor #{url}")
raise ArgumentError, message: "Can't do a signature on remote actor #{url}"
end
@spec generate_date_header :: String.t()
def generate_date_header, do: generate_date_header(NaiveDateTime.utc_now())
@spec generate_date_header(NaiveDateTime.t()) :: String.t()
def generate_date_header(%NaiveDateTime{} = date) do
# We make sure the format is correct
# TODO: Remove Timex, as this is the only usage (with parsing)
Timex.lformat!(date, "{WDshort}, {0D} {Mshort} {YYYY} {h24}:{m}:{s} GMT", "en")
end
@spec generate_request_target(String.t(), String.t()) :: String.t()
def generate_request_target(method, path), do: "#{method} #{path}"
@spec build_digest(String.t()) :: String.t()
def build_digest(body) do
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"SHA-256=#{:sha256 |> :crypto.hash(body) |> Base.encode64()}"
end
end