368 lines
12 KiB
Elixir
368 lines
12 KiB
Elixir
# Pleroma: A lightweight social networking server
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# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Object.Fetcher do
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alias Pleroma.HTTP
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alias Pleroma.Instances
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alias Pleroma.Maps
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alias Pleroma.Object
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alias Pleroma.Object.Containment
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alias Pleroma.Repo
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alias Pleroma.Signature
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alias Pleroma.Web.ActivityPub.InternalFetchActor
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alias Pleroma.Web.ActivityPub.ObjectValidator
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alias Pleroma.Web.ActivityPub.Transmogrifier
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alias Pleroma.Web.Federator
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require Logger
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require Pleroma.Constants
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@moduledoc """
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This module deals with correctly fetching Acitivity Pub objects in a safe way.
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The core function is `fetch_and_contain_remote_object_from_id/1` which performs
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the actual fetch and common safety and authenticity checks. Other `fetch_*`
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function use the former and perform some additional tasks
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"""
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@mix_env Mix.env()
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defp touch_changeset(changeset) do
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updated_at =
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NaiveDateTime.utc_now()
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|> NaiveDateTime.truncate(:second)
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Ecto.Changeset.put_change(changeset, :updated_at, updated_at)
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end
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defp maybe_reinject_internal_fields(%{data: %{} = old_data}, new_data) do
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has_history? = fn
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%{"formerRepresentations" => %{"orderedItems" => list}} when is_list(list) -> true
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_ -> false
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end
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internal_fields = Map.take(old_data, Pleroma.Constants.object_internal_fields())
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remote_history_exists? = has_history?.(new_data)
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# If the remote history exists, we treat that as the only source of truth.
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new_data =
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if has_history?.(old_data) and not remote_history_exists? do
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Map.put(new_data, "formerRepresentations", old_data["formerRepresentations"])
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else
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new_data
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end
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# If the remote does not have history information, we need to manage it ourselves
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new_data =
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if not remote_history_exists? do
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changed? =
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Pleroma.Constants.status_updatable_fields()
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|> Enum.any?(fn field -> Map.get(old_data, field) != Map.get(new_data, field) end)
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%{updated_object: updated_object} =
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new_data
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|> Object.Updater.maybe_update_history(old_data,
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updated: changed?,
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use_history_in_new_object?: false
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)
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updated_object
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else
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new_data
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end
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Map.merge(new_data, internal_fields)
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end
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defp maybe_reinject_internal_fields(_, new_data), do: new_data
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@spec reinject_object(struct(), map()) :: {:ok, Object.t()} | {:error, any()}
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defp reinject_object(%Object{data: %{"type" => "Question"}} = object, new_data) do
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Logger.debug("Reinjecting object #{new_data["id"]}")
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with data <- maybe_reinject_internal_fields(object, new_data),
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{:ok, data, _} <- ObjectValidator.validate(data, %{}),
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changeset <- Object.change(object, %{data: data}),
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changeset <- touch_changeset(changeset),
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{:ok, object} <- Repo.insert_or_update(changeset),
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{:ok, object} <- Object.set_cache(object) do
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{:ok, object}
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else
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e ->
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Logger.error("Error while processing object: #{inspect(e)}")
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{:error, e}
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end
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end
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defp reinject_object(%Object{} = object, new_data) do
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Logger.debug("Reinjecting object #{new_data["id"]}")
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with new_data <- Transmogrifier.fix_object(new_data),
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data <- maybe_reinject_internal_fields(object, new_data),
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changeset <- Object.change(object, %{data: data}),
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changeset <- touch_changeset(changeset),
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{:ok, object} <- Repo.insert_or_update(changeset),
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{:ok, object} <- Object.set_cache(object) do
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{:ok, object}
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else
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e ->
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Logger.error("Error while processing object: #{inspect(e)}")
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{:error, e}
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end
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end
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@doc "Assumes object already is in our database and refetches from remote to update (e.g. for polls)"
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def refetch_object(%Object{data: %{"id" => id}} = object) do
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with {:local, false} <- {:local, Object.local?(object)},
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{:ok, new_data} <- fetch_and_contain_remote_object_from_id(id),
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{:id, true} <- {:id, new_data["id"] == id},
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{:ok, object} <- reinject_object(object, new_data) do
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{:ok, object}
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else
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{:local, true} -> {:ok, object}
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{:id, false} -> {:error, "Object id changed on refetch"}
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e -> {:error, e}
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end
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end
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@doc """
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Fetches a new object and puts it through the processing pipeline for inbound objects
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Note: will also insert a fake Create activity, since atm we internally
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need everything to be traced back to a Create activity.
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"""
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def fetch_object_from_id(id, options \\ []) do
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with %URI{} = uri <- URI.parse(id),
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# let's check the URI is even vaguely valid first
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{:scheme, true} <- {:scheme, uri.scheme == "http" or uri.scheme == "https"},
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# If we have instance restrictions, apply them here to prevent fetching from unwanted instances
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{:ok, nil} <- Pleroma.Web.ActivityPub.MRF.SimplePolicy.check_reject(uri),
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{:ok, _} <- Pleroma.Web.ActivityPub.MRF.SimplePolicy.check_accept(uri),
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{_, nil} <- {:fetch_object, Object.get_cached_by_ap_id(id)},
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{_, true} <- {:allowed_depth, Federator.allowed_thread_distance?(options[:depth])},
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{_, {:ok, data}} <- {:fetch, fetch_and_contain_remote_object_from_id(id)},
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{_, nil} <- {:normalize, Object.normalize(data, fetch: false)},
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params <- prepare_activity_params(data),
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{_, {:ok, activity}} <-
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{:transmogrifier, Transmogrifier.handle_incoming(params, options)},
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{_, _data, %Object{} = object} <-
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{:object, data, Object.normalize(activity, fetch: false)} do
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{:ok, object}
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else
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{:allowed_depth, false} ->
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{:error, "Max thread distance exceeded."}
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{:scheme, false} ->
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{:error, "URI Scheme Invalid"}
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{:containment, e} ->
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Logger.info("Error while fetching #{id}: Object containment failed. #{inspect(e)}")
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{:error, e}
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{:transmogrifier, {:error, {:reject, e}}} ->
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Logger.info("Rejected #{id} while fetching: #{inspect(e)}")
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{:reject, e}
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{:transmogrifier, {:reject, e}} ->
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Logger.info("Rejected #{id} while fetching: #{inspect(e)}")
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{:reject, e}
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{:transmogrifier, _} = e ->
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{:error, e}
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{:object, data, nil} ->
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reinject_object(%Object{}, data)
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{:normalize, object = %Object{}} ->
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{:ok, object}
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{:fetch_object, %Object{} = object} ->
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{:ok, object}
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{:fetch, {:error, error}} ->
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Logger.error("Error while fetching #{id}: #{inspect(error)}")
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{:error, error}
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{:reject, reason} ->
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{:reject, reason}
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e ->
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Logger.error("Error while fetching #{id}: #{inspect(e)}")
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{:error, e}
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end
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end
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defp prepare_activity_params(data) do
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%{
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"type" => "Create",
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# Should we seriously keep this attributedTo thing?
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"actor" => data["actor"] || data["attributedTo"],
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"object" => data
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}
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|> Maps.put_if_present("to", data["to"])
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|> Maps.put_if_present("cc", data["cc"])
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|> Maps.put_if_present("bto", data["bto"])
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|> Maps.put_if_present("bcc", data["bcc"])
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end
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defp make_signature(id, date) do
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uri = URI.parse(id)
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signature =
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InternalFetchActor.get_actor()
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|> Signature.sign(%{
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"(request-target)": "get #{uri.path}",
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host: uri.host,
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date: date
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})
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{"signature", signature}
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end
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defp sign_fetch(headers, id, date) do
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if Pleroma.Config.get([:activitypub, :sign_object_fetches]) do
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[make_signature(id, date) | headers]
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else
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headers
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end
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end
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defp maybe_date_fetch(headers, date) do
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if Pleroma.Config.get([:activitypub, :sign_object_fetches]) do
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[{"date", date} | headers]
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else
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headers
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end
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end
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@doc "Fetches arbitrary remote object and performs basic safety and authenticity checks"
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def fetch_and_contain_remote_object_from_id(id)
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def fetch_and_contain_remote_object_from_id(%{"id" => id}),
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do: fetch_and_contain_remote_object_from_id(id)
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def fetch_and_contain_remote_object_from_id(id) when is_binary(id) do
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Logger.debug("Fetching object #{id} via AP")
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with {:scheme, true} <- {:scheme, String.starts_with?(id, "http")},
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{_, :ok} <- {:local_fetch, Containment.contain_local_fetch(id)},
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{:ok, final_id, body} <- get_object(id),
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{:ok, data} <- safe_json_decode(body),
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{_, :ok} <- {:strict_id, Containment.contain_id_to_fetch(final_id, data)},
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{_, :ok} <- {:containment, Containment.contain_origin(final_id, data)} do
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unless Instances.reachable?(final_id) do
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Instances.set_reachable(final_id)
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end
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{:ok, data}
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else
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{:strict_id, _} ->
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{:error, "Object's ActivityPub id/url does not match final fetch URL"}
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{:scheme, _} ->
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{:error, "Unsupported URI scheme"}
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{:local_fetch, _} ->
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{:error, "Trying to fetch local resource"}
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{:containment, _} ->
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{:error, "Object containment failed."}
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{:error, e} ->
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{:error, e}
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e ->
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{:error, e}
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end
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end
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def fetch_and_contain_remote_object_from_id(_id),
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do: {:error, "id must be a string"}
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defp check_crossdomain_redirect(final_host, original_url)
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# HOPEFULLY TEMPORARY
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# Basically none of our Tesla mocks in tests set the (supposed to
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# exist for Tesla proper) url parameter for their responses
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# causing almost every fetch in test to fail otherwise
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if @mix_env == :test do
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defp check_crossdomain_redirect(nil, _) do
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{:cross_domain_redirect, false}
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end
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end
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defp check_crossdomain_redirect(final_host, original_url) do
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{:cross_domain_redirect, final_host != URI.parse(original_url).host}
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end
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if @mix_env == :test do
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defp get_final_id(nil, initial_url), do: initial_url
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defp get_final_id("", initial_url), do: initial_url
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end
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defp get_final_id(final_url, _intial_url) do
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final_url
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end
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@doc "Do NOT use; only public for use in tests"
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def get_object(id) do
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date = Pleroma.Signature.signed_date()
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headers =
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[
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# The first is required by spec, the second provided as a fallback for buggy implementations
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{"accept", "application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\""},
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{"accept", "application/activity+json"}
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]
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|> maybe_date_fetch(date)
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|> sign_fetch(id, date)
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with {:ok, %{body: body, status: code, headers: headers, url: final_url}}
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when code in 200..299 <-
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HTTP.get(id, headers),
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remote_host <-
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URI.parse(final_url).host,
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{:cross_domain_redirect, false} <-
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check_crossdomain_redirect(remote_host, id),
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{:has_content_type, {_, content_type}} <-
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{:has_content_type, List.keyfind(headers, "content-type", 0)},
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{:parse_content_type, {:ok, "application", subtype, type_params}} <-
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{:parse_content_type, Plug.Conn.Utils.media_type(content_type)} do
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final_id = get_final_id(final_url, id)
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case {subtype, type_params} do
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{"activity+json", _} ->
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{:ok, final_id, body}
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{"ld+json", %{"profile" => "https://www.w3.org/ns/activitystreams"}} ->
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{:ok, final_id, body}
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_ ->
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{:error, {:content_type, content_type}}
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end
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else
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{:ok, %{status: 403}} ->
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{:error, "Object fetch has been denied"}
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{:ok, %{status: code}} when code in [404, 410] ->
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{:error, {"Object has been deleted", id, code}}
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{:error, e} ->
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{:error, e}
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{:has_content_type, _} ->
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{:error, {:content_type, nil}}
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{:parse_content_type, e} ->
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{:error, {:content_type, e}}
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e ->
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{:error, e}
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end
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end
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defp safe_json_decode(nil), do: {:ok, nil}
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defp safe_json_decode(json), do: Jason.decode(json)
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end
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