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cadcraft/crates/mcp/Cargo.toml
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Dylan M. Taylorandskylartaylor ca578a8fb7 security: authenticate the local control server with a per-session token (CWE-306) (#1844)
* security: authenticate the local control server with a per-session token (CWE-306)

The optional `--control PORT` server listens on loopback TCP and dispatched any
JSON request without authenticating the peer. Loopback TCP does not distinguish
operating-system users, so another local account could connect and drive the
desktop user's command and file authority (for example reading files through
native Lisp, or create/truncate writes).

Authenticate the peer with an unguessable per-session token:

- New `cadcraft_mcp::control_token` module: `issue(port)` generates a 256-bit
  token and writes it to `cadcraft-control-<port>.token` in the per-user runtime
  directory with owner-only permissions (0600 on Unix; per-user LOCALAPPDATA on
  Windows). `read(port)` reads it; `matches` compares in constant time.
- The control server issues the token at startup and requires every request to
  carry a matching `token` field; requests without one get an `unauthorized`
  reply and the connection is closed before dispatch.
- The MCP bridge (`Remote`) reads the token from the owner-only file — which
  needs the desktop user's own filesystem access — and sends it on every
  request, so the bridge keeps working unchanged for the legitimate user. A
  different local user cannot read the token and cannot authenticate.

Updates `docs/control-protocol.md`. New tests cover token issue/read/compare,
file permissions, and that the server refuses unauthenticated requests while
accepting authenticated ones.

Addresses finding row 48.

* fix: recover control authentication across server restarts

---------

Co-authored-by: skylartaylor <26588250+skylartaylor@users.noreply.github.com>
2026-10-22 17:35:18 -04:00

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TOML

[package]
name = "cadcraft-mcp"
description = "CADCraft MCP server: JSON-RPC 2.0 over stdio, driving a running app or a headless session"
version.workspace = true
edition.workspace = true
license.workspace = true
[lints]
workspace = true
[dependencies]
cadcraft-engine = { workspace = true }
cadcraft-render = { workspace = true }
cadcraft-io = { workspace = true }
serde_json = { workspace = true }
log = { workspace = true }
# Secure randomness for the per-session control token (MIT OR Apache-2.0).
getrandom = "0.3"