git.squeep.com Git - akkoma/blob - lib/pleroma/web/http_signatures/http_signatures.ex

   1 # https://tools.ietf.org/html/draft-cavage-http-signatures-08
   2 defmodule Pleroma.Web.HTTPSignatures do
   3   alias Pleroma.User
   4   alias Pleroma.Web.ActivityPub.ActivityPub
   5   require Logger
   6
   7   def split_signature(sig) do
   8     default = %{"headers" => "date"}
   9
  10     sig =
  11       sig
  12       |> String.trim()
  13       |> String.split(",")
  14       |> Enum.reduce(default, fn part, acc ->
  15         [key | rest] = String.split(part, "=")
  16         value = Enum.join(rest, "=")
  17         Map.put(acc, key, String.trim(value, "\""))
  18       end)
  19
  20     Map.put(sig, "headers", String.split(sig["headers"], ~r/\s/))
  21   end
  22
  23   def validate(headers, signature, public_key) do
  24     sigstring = build_signing_string(headers, signature["headers"])
  25     Logger.debug("Signature: #{signature["signature"]}")
  26     Logger.debug("Sigstring: #{sigstring}")
  27     {:ok, sig} = Base.decode64(signature["signature"])
  28     :public_key.verify(sigstring, :sha256, sig, public_key)
  29   end
  30
  31   def validate_conn(conn) do
  32     # TODO: How to get the right key and see if it is actually valid for that request.
  33     # For now, fetch the key for the actor.
  34     with actor_id <- conn.params["actor"],
  35          {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
  36       if validate_conn(conn, public_key) do
  37         true
  38       else
  39         Logger.debug("Could not validate, re-fetching user and trying one more time.")
  40         # Fetch user anew and try one more time
  41         with actor_id <- conn.params["actor"],
  42              {:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id),
  43              {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
  44           validate_conn(conn, public_key)
  45         end
  46       end
  47     else
  48       e ->
  49         Logger.debug("Could not public key!")
  50         false
  51     end
  52   end
  53
  54   def validate_conn(conn, public_key) do
  55     headers = Enum.into(conn.req_headers, %{})
  56     signature = split_signature(headers["signature"])
  57     validate(headers, signature, public_key)
  58   end
  59
  60   def build_signing_string(headers, used_headers) do
  61     used_headers
  62     |> Enum.map(fn header -> "#{header}: #{headers[header]}" end)
  63     |> Enum.join("\n")
  64   end
  65
  66   def sign(user, headers) do
  67     with {:ok, %{info: %{"keys" => keys}}} <- Pleroma.Web.WebFinger.ensure_keys_present(user),
  68          {:ok, private_key, _} = Pleroma.Web.Salmon.keys_from_pem(keys) do
  69       sigstring = build_signing_string(headers, Map.keys(headers))
  70
  71       signature =
  72         :public_key.sign(sigstring, :sha256, private_key)
  73         |> Base.encode64()
  74
  75       [
  76         keyId: user.ap_id <> "#main-key",
  77         algorithm: "rsa-sha256",
  78         headers: Map.keys(headers) |> Enum.join(" "),
  79         signature: signature
  80       ]
  81       |> Enum.map(fn {k, v} -> "#{k}=\"#{v}\"" end)
  82       |> Enum.join(",")
  83     end
  84   end
  85 end