* MCP bridge: send the control key, to loopback addresses only
`wordcraft-cli mcp --connect` now sends the app's control key with every
request. It takes the key from WORDCRAFT_CONTROL_KEY, or else from the
key file the app writes for that port, and reads it again on every new
connection, also after an `unauthorized` reply (the app restarted with
a new key).
The key goes only to loopback addresses: 127.0.0.0/8, ::1 and
`localhost`, and only when the connection really leads to a loopback
address. For any other host the bridge sends no key, prints why at
start, and turns the app's `unauthorized` into an error that says the
key was not sent and how to reach the app (through 127.0.0.1, for
example an SSH tunnel). Other host names are never resolved for this.
The new `wordcraft_mcp::control_key` module holds the rule the app and
the bridge share: the settings folder (the one with ui.json), the
Flatpak instance id and `<settings>/control-key.<instance>`
(`local-<port>` outside Flatpak). No new dependency; wasm-safe.
* Control port: every request needs the window's key
Any local program, and possibly a web page, could drive the app through
its loopback control port. Each window started with --control now has
a key:
- once the port is bound, the app writes a random key (32 bytes from
the OS, as hex) to <settings>/control-key.<instance>, mode 0600 on
Unix, replacing a stale file; it removes the file on a clean exit. A
failed bind writes nothing. <instance> is the Flatpak instance id, or
local-<port> outside Flatpak (wordcraft_mcp::control_key, the rule
the MCP bridge reads it with). The settings folder is the one that
holds ui.json; prefs_path now uses the same helper.
- every request needs the key: top-level "key", or
{"method":"auth","key":...} once per connection. Only auth reads
params.key; elsewhere it stays an ordinary parameter (ui.key). The key
is checked on every request, in time that does not depend on where a
wrong key differs. A missing or wrong key gets
{"ok":false,"error":"unauthorized"} and the connection is closed.
- a line over 1 MiB gets "line too long" and the connection is closed
(the rest of the line is drained first, so the client reads the
error).
- a connection that sends no authorised request within 30 s of being
accepted is closed; blank lines and bad JSON do not extend that
limit. After that it may stay idle.
* Docs: control-port keys
docs/control-protocol.md gets a Keys section: where the key file is
(per platform and per instance), top-level "key" or auth once per
connection, `unauthorized` and the closed connection, the 1 MiB line
limit, the 30 s limit for the first authorised request, and how the MCP
bridge finds the key and sends it only to loopback addresses (an SSH
tunnel for an app on another machine). docs/mcp.md points there, and
the agent guides (AGENTS.md, CLAUDE.md) show the key in their control
channel example.
* Control key: the key-file helpers in their own small crate
wordcraft-control-key (standard library only, Standalone in the layering
table) holds where the key file lives and how to read it. The app and the
MCP bridge both use it, so the app no longer depends on wordcraft-mcp.
* Cargo.lock: wordcraft-control-key follows the workspace version (0.4.0)
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: lpgn <2556951+lpgn@users.noreply.github.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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