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

   1 defmodule Pleroma.Web.Salmon do
   2   use Bitwise
   3
   4   def decode_and_validate(magickey, salmon) do
   5     {doc, _rest} = :xmerl_scan.string(to_charlist(salmon))
   6
   7     {:xmlObj, :string, data} = :xmerl_xpath.string('string(//me:data[1])', doc)
   8     {:xmlObj, :string, sig} = :xmerl_xpath.string('string(//me:sig[1])', doc)
   9     {:xmlObj, :string, alg} = :xmerl_xpath.string('string(//me:alg[1])', doc)
  10     {:xmlObj, :string, encoding} = :xmerl_xpath.string('string(//me:encoding[1])', doc)
  11     {:xmlObj, :string, type} = :xmerl_xpath.string('string(//me:data[1]/@type)', doc)
  12
  13
  14     {:ok, data} = Base.url_decode64(to_string(data), ignore: :whitespace)
  15     {:ok, sig} = Base.url_decode64(to_string(sig), ignore: :whitespace)
  16     alg = to_string(alg)
  17     encoding = to_string(encoding)
  18     type = to_string(type)
  19
  20     signed_text = [data, type, encoding, alg]
  21     |> Enum.map(&Base.url_encode64/1)
  22     |> Enum.join(".")
  23
  24     key = decode_key(magickey)
  25
  26     verify = :public_key.verify(signed_text, :sha256, sig, key)
  27
  28     if verify do
  29       {:ok, data}
  30     else
  31       :error
  32     end
  33   end
  34
  35   defp decode_key("RSA." <> magickey) do
  36     make_integer = fn(bin) ->
  37       list = :erlang.binary_to_list(bin)
  38       Enum.reduce(list, 0, fn (el, acc) -> (acc <<< 8) ||| el end)
  39     end
  40
  41     [modulus, exponent] = magickey
  42     |> String.split(".")
  43     |> Enum.map(&Base.url_decode64!/1)
  44     |> Enum.map(make_integer)
  45
  46     {:RSAPublicKey, modulus, exponent}
  47   end
  48 end