architex/lib/matrix_server_web/federation/authenticate_server.ex

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defmodule MatrixServerWeb.Federation.AuthenticateServer do
import MatrixServerWeb.Error
alias MatrixServer.{SigningKey, ServerKeyInfo}
@auth_header_regex ~r/^X-Matrix origin=(?<origin>.*),key="(?<key>.*)",sig="(?<sig>.*)"$/
def authenticate(%Plug.Conn{
body_params: body_params,
req_headers: headers,
request_path: path,
method: method,
query_string: query_string
}) do
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object_to_sign = %{
uri: path <> "?" <> URI.decode_www_form(query_string),
method: method,
destination: MatrixServer.server_name()
}
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object_to_sign =
if method != "GET", do: Map.put(object_to_sign, :content, body_params), else: object_to_sign
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object_fun = &Map.put(object_to_sign, :origin, &1)
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authenticate_with_headers(headers, object_fun)
end
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defp authenticate_with_headers(headers, object_fun) do
# TODO: Only query once per origin.
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headers
|> parse_authorization_headers()
|> Enum.find(:error, fn {origin, _, sig} ->
object = object_fun.(origin)
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with {:ok, raw_sig} <- MatrixServer.decode_base64(sig),
{:ok, encoded_object} <- MatrixServer.encode_canonical_json(object),
{:ok, %ServerKeyInfo{signing_keys: keys}} <-
ServerKeyInfo.with_fresh_signing_keys(origin) do
Enum.find_value(keys, false, fn %SigningKey{signing_key: signing_key} ->
with {:ok, decoded_key} <- MatrixServer.decode_base64(signing_key) do
MatrixServer.sign_verify(raw_sig, encoded_object, decoded_key)
else
_ -> false
end
end)
else
_ -> false
end
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end)
end
def parse_authorization_headers(headers) do
headers
|> Enum.filter(&(elem(&1, 0) == "authorization"))
|> Enum.map(fn {_, auth_header} ->
Regex.named_captures(@auth_header_regex, auth_header)
end)
|> Enum.reject(&Kernel.is_nil/1)
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|> Enum.map(fn %{"origin" => origin, "key" => key, "sig" => sig} ->
{origin, key, sig}
end)
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|> Enum.filter(fn {_, key, _} -> String.starts_with?(key, "ed25519:") end)
end
defmacro __using__(opts) do
except = Keyword.get(opts, :except) || []
quote do
def action(conn, _) do
action = action_name(conn)
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if action not in unquote(except) do
case MatrixServerWeb.Federation.AuthenticateServer.authenticate(conn) do
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{origin, _key, _sig} ->
conn = Plug.Conn.assign(conn, :origin, origin)
apply(__MODULE__, action, [conn, conn.params])
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:error ->
put_error(conn, :unauthorized, "Signature verification failed.")
end
else
apply(__MODULE__, action, [conn, conn.params])
end
end
end
end
end