118 lines
3.5 KiB
Elixir
118 lines
3.5 KiB
Elixir
# https://tools.ietf.org/html/draft-cavage-http-signatures-08
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defmodule Mobilizon.Service.HTTPSignatures do
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@moduledoc """
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# HTTP Signatures
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Generates and checks HTTP Signatures
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"""
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alias Mobilizon.Actors.Actor
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alias Mobilizon.Service.ActivityPub
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require Logger
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def split_signature(sig) do
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default = %{"headers" => "date"}
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sig =
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sig
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|> String.trim()
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|> String.split(",")
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|> Enum.reduce(default, fn part, acc ->
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[key | rest] = String.split(part, "=")
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value = Enum.join(rest, "=")
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Map.put(acc, key, String.trim(value, "\""))
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end)
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Map.put(sig, "headers", String.split(sig["headers"], ~r/\s/))
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end
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def validate(headers, signature, public_key) do
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sigstring = build_signing_string(headers, signature["headers"])
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Logger.debug(fn ->
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"Signature: #{signature["signature"]}"
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end)
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Logger.debug(fn ->
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"Sigstring: #{sigstring}"
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end)
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{:ok, sig} = Base.decode64(signature["signature"])
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:public_key.verify(sigstring, :sha256, sig, public_key)
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end
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def validate_conn(conn) do
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# TODO: How to get the right key and see if it is actually valid for that request.
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# For now, fetch the key for the actor.
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with {:ok, public_key} <- conn.params["actor"] |> Actor.get_public_key_for_url() do
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if validate_conn(conn, public_key) do
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true
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else
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Logger.info("Could not validate request, re-fetching user and trying one more time")
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# Fetch user anew and try one more time
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with actor_id <- conn.params["actor"],
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{:ok, _actor} <- ActivityPub.make_actor_from_url(actor_id),
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{:ok, public_key} <- actor_id |> Actor.get_public_key_for_url() do
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validate_conn(conn, public_key)
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end
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end
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else
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e ->
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Logger.debug("Could not found url for actor!")
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Logger.debug(inspect(e))
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false
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end
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end
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def validate_conn(conn, public_key) do
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headers = Enum.into(conn.req_headers, %{})
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host_without_port = String.split(headers["host"], ":") |> hd
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headers = Map.put(headers, "host", host_without_port)
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signature = split_signature(headers["signature"])
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validate(headers, signature, public_key)
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end
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def build_signing_string(headers, used_headers) do
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used_headers
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|> Enum.map(fn header -> "#{header}: #{headers[header]}" end)
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|> Enum.join("\n")
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end
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def sign(%Actor{} = actor, headers) do
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with sigstring <- build_signing_string(headers, Map.keys(headers)),
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{:ok, key} <- actor.keys |> Actor.prepare_public_key(),
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signature <- sigstring |> :public_key.sign(:sha256, key) |> Base.encode64() do
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[
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keyId: actor.url <> "#main-key",
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algorithm: "rsa-sha256",
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headers: headers |> Map.keys() |> Enum.join(" "),
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signature: signature
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]
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|> Enum.map(fn {k, v} -> "#{k}=\"#{v}\"" end)
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|> Enum.join(",")
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else
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err ->
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Logger.error("Unable to sign headers")
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Logger.error(inspect(err))
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nil
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end
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end
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def generate_date_header(date \\ Timex.now("GMT")) do
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with {:ok, date} <- Timex.format(date, "%a, %d %b %Y %H:%M:%S %Z", :strftime) do
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date
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else
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{:error, err} ->
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Logger.error("Unable to generate date header")
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Logger.error(inspect(err))
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nil
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end
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end
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def generate_request_target(method, path), do: "#{method} #{path}"
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def build_digest(body) do
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"SHA-256=" <> (:crypto.hash(:sha256, body) |> Base.encode64())
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end
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end
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