73 lines
2.3 KiB
Elixir
73 lines
2.3 KiB
Elixir
defmodule Pleroma.Web.Salmon do
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use Bitwise
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def decode(salmon) do
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{doc, _rest} = :xmerl_scan.string(to_charlist(salmon))
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{:xmlObj, :string, data} = :xmerl_xpath.string('string(//me:data[1])', doc)
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{:xmlObj, :string, sig} = :xmerl_xpath.string('string(//me:sig[1])', doc)
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{:xmlObj, :string, alg} = :xmerl_xpath.string('string(//me:alg[1])', doc)
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{:xmlObj, :string, encoding} = :xmerl_xpath.string('string(//me:encoding[1])', doc)
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{:xmlObj, :string, type} = :xmerl_xpath.string('string(//me:data[1]/@type)', doc)
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{:ok, data} = Base.url_decode64(to_string(data), ignore: :whitespace)
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{:ok, sig} = Base.url_decode64(to_string(sig), ignore: :whitespace)
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alg = to_string(alg)
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encoding = to_string(encoding)
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type = to_string(type)
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[data, type, encoding, alg, sig]
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end
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def fetch_magic_key(salmon) do
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[data, _, _, _, _] = decode(salmon)
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{doc, _rest} = :xmerl_scan.string(to_charlist(data))
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{:xmlObj, :string, uri} = :xmerl_xpath.string('string(//author[1]/uri)', doc)
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uri = to_string(uri)
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base = URI.parse(uri).host
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# TODO: Find out if this endpoint is mandated by the standard.
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{:ok, response} = HTTPoison.get(base <> "/.well-known/webfinger", ["Accept": "application/xrd+xml"], [params: [resource: uri]])
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{doc, _rest} = :xmerl_scan.string(to_charlist(response.body))
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{:xmlObj, :string, magickey} = :xmerl_xpath.string('string(//Link[@rel="magic-public-key"]/@href)', doc)
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"data:application/magic-public-key," <> magickey = to_string(magickey)
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magickey
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end
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def decode_and_validate(magickey, salmon) do
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[data, type, encoding, alg, sig] = decode(salmon)
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signed_text = [data, type, encoding, alg]
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|> Enum.map(&Base.url_encode64/1)
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|> Enum.join(".")
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key = decode_key(magickey)
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verify = :public_key.verify(signed_text, :sha256, sig, key)
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if verify do
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{:ok, data}
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else
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:error
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end
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end
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defp decode_key("RSA." <> magickey) do
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make_integer = fn(bin) ->
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list = :erlang.binary_to_list(bin)
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Enum.reduce(list, 0, fn (el, acc) -> (acc <<< 8) ||| el end)
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end
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[modulus, exponent] = magickey
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|> String.split(".")
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|> Enum.map(&Base.url_decode64!/1)
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|> Enum.map(make_integer)
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{:RSAPublicKey, modulus, exponent}
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end
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end
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