135 lines
4.4 KiB
Elixir
135 lines
4.4 KiB
Elixir
defmodule BDS.Server do
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@moduledoc """
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Headless server mode (issue #26).
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Boots the app without any wx window and serves clients over a single SSH
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daemon: TUI sessions run server-side via `ExRatatui.SSH` (only terminal
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cells cross the wire), and GUI clients tunnel to the loopback HTTP
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endpoint through the same daemon (`tcpip_tunnel_out`). Authentication is
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public-key only; host key and `authorized_keys` live in the private app
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data dir next to the database — never in the repo or a priv dir.
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"""
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@doc """
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Resolves the boot mode from the `BDS_MODE` environment variable:
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`"server"` (headless + SSH daemon), `"tui"` (headless + SSH daemon +
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a TUI attached to the launching terminal), anything else is desktop.
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"""
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@spec mode(String.t() | nil) :: :desktop | :server | :tui
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def mode(value \\ System.get_env("BDS_MODE"))
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def mode(value) when is_binary(value) do
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case String.downcase(value) do
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"server" -> :server
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"tui" -> :tui
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_other -> :desktop
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end
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end
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def mode(nil), do: :desktop
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@doc """
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The mode the app actually boots in: the resolved `BDS_MODE`, except that
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desktop mode falls back to the TUI when no graphical display is available
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(issue #33). Starting the app on a display-less Linux server then still
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opens a UI — the terminal one — instead of crashing wx.
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Only non-Darwin unix systems fall back: they need `DISPLAY` or
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`WAYLAND_DISPLAY` to run wx, while macOS and Windows always have a
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graphical session for a launched app.
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"""
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@spec effective_mode(:desktop | :server | :tui, {atom(), atom()}, %{
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optional(String.t()) => String.t()
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}) :: :desktop | :server | :tui
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def effective_mode(mode \\ mode(), os_type \\ :os.type(), env \\ System.get_env())
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def effective_mode(:desktop, {:unix, os}, env) when os != :darwin do
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if Enum.any?(["DISPLAY", "WAYLAND_DISPLAY"], &(env[&1] not in [nil, ""])),
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do: :desktop,
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else: :tui
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end
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def effective_mode(mode, _os_type, _env), do: mode
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@doc """
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Whether the HTTP endpoint requires the desktop webview auth token. Only
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desktop mode does: in server/tui mode the endpoint stays loopback-only
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and clients arrive through the key-authenticated SSH tunnel, which the
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per-boot webview token would otherwise lock out.
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"""
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@spec desktop_auth_required?(:desktop | :server | :tui) :: boolean()
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def desktop_auth_required?(mode \\ effective_mode())
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def desktop_auth_required?(:desktop), do: true
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def desktop_auth_required?(_mode), do: false
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@doc "SSH key-material directory: `<data dir>/ssh` next to the database."
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@spec ssh_dir() :: Path.t()
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def ssh_dir do
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Application.get_env(:bds, BDS.Repo)[:database]
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|> Path.dirname()
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|> Path.join("ssh")
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end
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@doc """
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Ensures the SSH directory exists with an `authorized_keys` file (created
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empty and chmod 600 on first boot; existing keys are never touched).
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"""
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@spec ensure_ssh_dir!(Path.t()) :: Path.t()
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def ensure_ssh_dir!(dir) do
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File.mkdir_p!(dir)
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keys_path = Path.join(dir, "authorized_keys")
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unless File.exists?(keys_path) do
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File.write!(keys_path, "")
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File.chmod!(keys_path, 0o600)
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end
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dir
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end
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@doc """
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Options for `ExRatatui.SSH.Daemon`: serves `BDS.TUI`, public-key auth
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only, and allows TCP/IP tunneling out so GUI clients can reach the
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loopback HTTP endpoint through the SSH connection.
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"""
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@spec daemon_opts(Path.t()) :: keyword()
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def daemon_opts(dir \\ ssh_dir()) do
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dir = ensure_ssh_dir!(dir)
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system_dir = ExRatatui.SSH.Daemon.ensure_host_key!(dir)
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[
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mod: BDS.TUI,
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port: ssh_port(),
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system_dir: system_dir,
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user_dir: String.to_charlist(dir),
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auth_methods: ~c"publickey",
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tcpip_tunnel_out: true
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]
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end
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@doc "SSH listen port: `BDS_SSH_PORT` env or `:bds, :server` config."
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@spec ssh_port() :: pos_integer()
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def ssh_port do
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case System.get_env("BDS_SSH_PORT") do
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value when is_binary(value) and value != "" -> String.to_integer(value)
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_other -> Application.get_env(:bds, :server)[:ssh_port] || 2222
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end
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end
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@doc false
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# Child spec that defers all filesystem work (key generation) to process
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# start, so building a children list never touches the data dir.
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def child_spec(_opts) do
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%{
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id: __MODULE__,
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start: {__MODULE__, :start_link, []},
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type: :worker
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}
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end
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@doc false
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def start_link do
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ExRatatui.SSH.Daemon.start_link(daemon_opts())
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end
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end
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