Initial commit: hello-agent — headless RustDesk-protocol-compatible Windows agent

A single-binary, Flutter-free remote-support agent that speaks the stock
RustDesk wire protocol. Designed for one-line MDM deployment against a
self-hosted rustdesk-server: a supporter using the unmodified rustdesk.exe
client connects, the controlled-side user gets a native Win32 approval
prompt, click Yes / No.

CLI surface

    hello-agent.exe --install                # register + start service
    hello-agent.exe --uninstall              # stop, delete, clean up
    hello-agent.exe --config <BLOB>          # admin-UI deploy string
    hello-agent.exe --install --config <BLOB>   # MDM one-liner

--config accepts both forms emitted by the rustdesk-server admin UI: the
reversed-base64 deploy string and the host=,key=,api=,relay= filename
form. Decoded via the upstream custom_server module, persisted via
hbb_common::config::Config::set_option.

Architecture

    --service runs as a Session 0 LocalSystem service. It polls
    WTSGetActiveConsoleSessionId and (re)spawns hello-agent.exe --server
    into the active console session via librustdesk::platform::run_as_user,
    handling the Session 0 → user-session token impersonation.

    --server is the worker. It boots three concurrent components:
      1. cm_popup: an IPC listener on the rustdesk `_cm` named pipe
      2. librustdesk::start_server(true, false): the upstream protocol
         stack — rendezvous mediator, NAT punch, IPC server, screen
         capture, login validation, hbbs_http heartbeat / sysinfo sync
      3. (implicit) ApproveMode::Click is pinned in config, so every
         incoming connection routes through cm_popup

The popup mechanism reuses an existing upstream contract without any
patches to the protocol code: when a peer connects with no password,
Connection::start in the upstream code calls try_start_cm_ipc, which
ipc::connect-s the `_cm` pipe before falling back to spawning a Flutter
CM child. Since cm_popup is up first, step 1 succeeds; we read the
Data::Login{authorized:false} frame, show MessageBoxTimeoutW (Yes/No,
60s, top-most, system-modal), and reply Data::Authorize or Data::Close.

Source tree

    src/main.rs             CLI dispatcher + run_server() composition
    src/cli.rs              hand-rolled argv parser + unit tests
    src/service.rs          windows-service install/uninstall/dispatcher
    src/config_import.rs    --config blob decoding + persistence
    src/cm_popup.rs         _cm IPC listener + Win32 approval dialog

Vendoring

The upstream RustDesk crate is vendored under vendor/rustdesk/ — full
workspace including libs/{hbb_common, scrap, enigo, clipboard,
virtual_display, remote_printer}. This makes the build self-contained
(no submodules, no sibling-repo checkout in CI) and gives us freedom to
fork in a different direction later. Excluded from the vendor: .git,
target/, flutter/, appimage/, flatpak/, fastlane/, docs/, examples/,
ci/, build.py, Dockerfile, upstream README/CLAUDE/AGENTS/GEMINI.

One local divergence vs. upstream: vendor/rustdesk/src/lib.rs flips
`mod custom_server` → `pub mod custom_server` so config_import.rs can
call get_custom_server_from_string without going through the
ui_interface shim. Documented in README.md → "Re-syncing the vendored
copy".

CI

.gitea/workflows/build-windows.yml builds on a self-hosted Windows
runner with Rust 1.75, LLVM 15.0.6 (libclang for bindgen via libvpx-sys),
and a vcpkg cache. The vendored vcpkg.json drives x64-windows-static
deps. The workflow stages the resulting hello-agent.exe into
SignOutput\, reports authenticode signing status (warns on unsigned),
and uploads as artifact. ~15 min full build, faster on incremental.

Out of scope for this commit: Linux/macOS builds, code signing, MSI
packaging, coexistence with stock rustdesk on the same box (currently
shares the RustDesk APP_NAME and config dir).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

build.rs

@@ -0,0 +1,40 @@
+// Embed the application icon and EXE metadata on Windows.
+//
+// The icon (`resources/icon.ico`, multi-frame: 16/32/48/64/128/256) ends
+// up as the executable's IDI_ICON1 resource — that's what Explorer, the
+// taskbar, Alt+Tab, the Task Manager, and the title-bar of any dialog
+// hosted by this process pick up. Regenerate the .ico from the source
+// PNG by running `python3 resources/build_ico.py`.
+//
+// The version-info block populates the "Details" tab in the EXE's
+// Properties dialog (ProductName / FileDescription / etc.). winres
+// derives FileVersion / ProductVersion from CARGO_PKG_VERSION
+// automatically.
+//
+// We gate on `CARGO_CFG_TARGET_OS` (the *target* OS, not the host) so a
+// cross-compile from Linux/macOS to Windows still embeds the icon. winres
+// inspects the active linker/toolchain (windres for GNU, rc.exe for MSVC)
+// when invoked.
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=resources/icon.ico");
+
+    let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+    if target_os != "windows" {
+        return;
+    }
+
+    let mut res = winres::WindowsResource::new();
+    res.set_icon("resources/icon.ico")
+        .set("ProductName", "HelloAgent")
+        .set("FileDescription", "HelloAgent — RustDesk-protocol support agent")
+        .set("CompanyName", "cStudio GmbH")
+        .set("LegalCopyright", "Copyright © 2026 cStudio GmbH")
+        .set("OriginalFilename", "hello-agent.exe")
+        .set("InternalName", "hello-agent");
+    if let Err(e) = res.compile() {
+        eprintln!("winres: failed to compile icon resource: {e}");
+        std::process::exit(1);
+    }
+}