103 lines
2.9 KiB
Elixir
103 lines
2.9 KiB
Elixir
# Pleroma: A lightweight social networking server
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# SPDX-FileCopyrightText: 2017-2019 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: LGPL-3.0-only
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# https://tools.ietf.org/html/draft-cavage-http-signatures-08
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defmodule HTTPSignatures do
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@moduledoc """
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HTTP Signatures library.
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"""
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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("Signature: #{signature["signature"]}")
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Logger.debug("Sigstring: #{sigstring}")
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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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adapter = Application.get_env(:http_signatures, :adapter)
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with {:ok, public_key} <- adapter.fetch_public_key(conn) 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.debug("Could not validate, trying to refetch any relevant keys")
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with {:ok, public_key} <- adapter.refetch_public_key(conn) 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 validate against known public keys: #{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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signature = split_signature(headers["signature"])
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validate(headers, signature, public_key)
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end
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@doc "Get signature for conn in split form."
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def signature_for_conn(conn) do
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with headers <- Enum.into(conn.req_headers, %{}),
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signature when is_binary(signature) <- headers["signature"] do
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split_signature(signature)
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else
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_ ->
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%{}
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end
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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_join("\n", fn header -> "#{header}: #{headers[header]}" end)
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end
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# Sort map alphabetically to ensure stability
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defp stable_sort_headers(headers) do
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headers
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|> Enum.into([])
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|> Enum.sort_by(fn {k, _v} -> k end)
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end
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def sign(private_key, key_id, headers) do
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headers = stable_sort_headers(headers)
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sigstring = build_signing_string(headers, Keyword.keys(headers))
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signature =
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:public_key.sign(sigstring, :sha256, private_key)
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|> Base.encode64()
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[
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keyId: key_id,
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algorithm: "rsa-sha256",
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headers: Keyword.keys(headers) |> Enum.join(" "),
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signature: signature
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]
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|> Enum.map_join(",", fn {k, v} -> "#{k}=\"#{v}\"" end)
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end
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end
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