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
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alias Mobilizon.Federation.ActivityPub
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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
%{path: path} =
uri =
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key_id
|> URI.parse()
|> Map.put(:fragment, nil)
uri =
if is_nil(path) do
uri
else
Map.put(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_fetch_error | :pem_decode_error}
defp get_public_key_for_url(url) do
with {:ok, %Actor{keys: keys}} <- ActivityPub.get_or_fetch_actor_by_url(url),
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{:ok, public_key} <- prepare_public_key(keys) do
{:ok, public_key}
else
{:error, :pem_decode_error} ->
Logger.error("Error while decoding PEM")
{:error, :pem_decode_error}
_ ->
Logger.error("Unable to fetch actor, so no keys for you")
{:error, :actor_fetch_error}
end
end
def fetch_public_key(conn) do
with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
actor_id <- key_id_to_actor_url(kid),
:ok <- Logger.debug("Fetching public key for #{actor_id}"),
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{:ok, public_key} <- get_public_key_for_url(actor_id) do
{:ok, public_key}
else
e ->
{:error, e}
end
end
def refetch_public_key(conn) do
with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
actor_id <- key_id_to_actor_url(kid),
:ok <- Logger.debug("Refetching public key for #{actor_id}"),
{:ok, _actor} <- ActivityPub.make_actor_from_url(actor_id),
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{:ok, public_key} <- get_public_key_for_url(actor_id) do
{:ok, public_key}
else
e ->
{:error, e}
end
end
def sign(%Actor{domain: domain, keys: keys} = actor, headers) when is_nil(domain) do
Logger.debug("Signing a payload on behalf of #{actor.url}")
Logger.debug("headers")
Logger.debug(inspect(headers))
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with {:ok, key} <- prepare_public_key(keys) do
HTTPSignatures.sign(key, actor.url <> "#main-key", headers)
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
def generate_date_header, do: generate_date_header(NaiveDateTime.utc_now())
def generate_date_header(%NaiveDateTime{} = date) do
Timex.format!(date, "{WDshort}, {0D} {Mshort} {YYYY} {h24}:{m}:{s} GMT")
end
def generate_request_target(method, path), do: "#{method} #{path}"
def build_digest(body) do
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"SHA-256=#{:sha256 |> :crypto.hash(body) |> Base.encode64()}"
end
end