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87 lines
2.5 KiB
Elixir
87 lines
2.5 KiB
Elixir
defmodule PhilomenaWeb.ContentSecurityPolicyPlug do
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import PhilomenaWeb.Config
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import Plug.Conn
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@allowed_sources [
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:script_src,
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:frame_src,
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:style_src
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]
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def init(opts) do
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opts
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end
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def call(conn, _opts) do
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cdn_uri = cdn_uri()
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camo_uri = camo_uri()
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register_before_send(conn, fn conn ->
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config = get_config(conn)
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script_src = Keyword.get(config, :script_src, [])
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style_src = Keyword.get(config, :style_src, [])
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frame_src = Keyword.get(config, :frame_src, nil)
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csp_config = [
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{:default_src, ["'self'"]},
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{:script_src, [default_script_src() | script_src]},
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{:connect_src, [default_connect_src()]},
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{:style_src, [default_style_src() | style_src]},
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{:object_src, ["'none'"]},
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{:frame_ancestors, ["'none'"]},
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{:frame_src, frame_src || ["'none'"]},
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{:form_action, ["'self'"]},
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{:manifest_src, ["'self'"]},
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{:img_src, ["'self'", "blob:", "data:", cdn_uri, camo_uri]},
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{:media_src, ["'self'", "blob:", "data:", cdn_uri, camo_uri]}
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]
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csp_value = Enum.map_join(csp_config, "; ", &cspify_element/1)
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csp_relaxed? do
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if conn.status == 500 do
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# Allow Plug.Debugger to function in this case
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delete_resp_header(conn, "content-security-policy")
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else
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# Enforce CSP otherwise
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put_resp_header(conn, "content-security-policy", csp_value)
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end
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else
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put_resp_header(conn, "content-security-policy", csp_value)
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end
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end)
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end
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def permit_source(conn, key, value) when key in @allowed_sources do
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conn
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|> get_config()
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|> Keyword.update(key, value, &(value ++ &1))
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|> set_config(conn)
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end
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defp get_config(conn), do: conn.private[:csp] || []
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defp set_config(value, conn), do: put_private(conn, :csp, value)
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defp cdn_uri, do: Application.get_env(:philomena, :cdn_host) |> to_uri()
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defp camo_uri, do: Application.get_env(:philomena, :camo_host) |> to_uri()
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defp default_script_src, do: vite_hmr?(do: "*", else: "'self'")
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defp default_connect_src,
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do: vite_hmr?(do: "*", else: "'self'")
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defp default_style_src, do: vite_hmr?(do: "'unsafe-inline' *", else: "'self'")
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defp to_uri(host) when host in [nil, ""], do: ""
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defp to_uri(host), do: URI.to_string(%URI{scheme: "https", host: host})
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defp cspify_element({key, value}) do
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key =
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key
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|> Atom.to_string()
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|> String.replace("_", "-")
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Enum.join([key | value], " ")
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end
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end
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