security(desktop): IPC serial-command-injection + over-broad shell capability + ADR-178 (#1100)

* fix(security): desktop IPC serial-command-injection + over-broad shell capability (ADR-178)

Beyond-SOTA security review of wifi-densepose-desktop (Tauri v2). Two real
findings, each MEASURED on Windows (crate builds + tests under
--no-default-features):

WDP-DESK-01 (MODERATE) — serial command injection via configure_esp32_wifi.
The #[tauri::command] handler concatenated webview-supplied ssid/password into
newline-terminated serial commands with no validation; a \r\n let a compromised
webview inject an arbitrary follow-up firmware command (reboot/erase). Added
validate_wifi_credentials() enforcing WPA2 length bounds and rejecting all
control characters, called fail-closed before any serial write. Pinned by 3
new tests (rejects \r\n / \n / NUL injection, rejects out-of-range, accepts
valid boundaries).

WDP-DESK-02 (MODERATE) — removed unused shell:allow-execute / shell:allow-open
from capabilities/default.json. The Rust backend spawns processes via
std::process::Command (bypassing the allowlist) and the UI only uses
dialog.open; the shell perms were unused privilege granting the webview
arbitrary host command execution on compromise. Regenerated capabilities.json
confirms only core:default + dialog perms remain.

lib tests 18 -> 21 (+3 pins), integration 21 -> 21, 0 failed. Python
deterministic proof unchanged (f8e76f21...46f7a; desktop off the signal path).

Co-Authored-By: claude-flow <ruv@ruv.net>

* docs(adr): ADR-178 — desktop IPC injection fix + capability least-privilege

Records the 2 MEASURED MODERATE fixes in feddcde9d: WDP-DESK-01 (webview
ssid/password \r\n-injected arbitrary firmware serial commands → validated
fail-closed) and WDP-DESK-02 (unused shell:allow-execute/open capability
granted to the webview → removed). 30-command IPC surface + capability scope
audited; 6 dimensions clean-with-evidence. desktop 18→21.

Co-Authored-By: claude-flow <ruv@ruv.net>

docs/adr/ADR-178-desktop-ipc-injection-and-capability-least-privilege.md

@@ -0,0 +1,87 @@
+# ADR-178: `wifi-densepose-desktop` IPC Injection Fix + Capability Least-Privilege
+
+| Field | Value |
+|-------|-------|
+| **Status** | Accepted — 2 real MODERATE bugs fixed + pinned (MEASURED on Windows) |
+| **Date** | 2026-06-15 |
+| **Deciders** | ruv |
+| **Codename** | **DESK-LOCKDOWN** |
+| **Reviews** | `wifi-densepose-desktop` (Tauri v2 desktop app) |
+| **Milestone** | #9 (ungated-crate security sweep) — crate 3 of 4 |
+
+## Context
+
+`wifi-densepose-desktop` is the Tauri v2 desktop app (ESP32 discovery, firmware
+flashing, OTA, provisioning, server control). The real attack surface is the
+**Tauri IPC boundary** — `#[tauri::command]` handlers that take arguments from the
+webview/JS — and the **capability/allowlist scope**. The crate **builds and tests
+on Windows** (Tauri 2.10.3, webview2 path, no GTK), so both findings are MEASURED,
+not source-analysis-only.
+
+## Decision
+
+Fix the two real findings; attest the rest of the surface clean with evidence.
+
+### Findings fixed (both MEASURED)
+
+| # | Severity | Location | Issue | Fix |
+|---|----------|----------|-------|-----|
+| WDP-DESK-01 | MODERATE | `src/commands/discovery.rs:438` (`configure_esp32_wifi`) | Webview-supplied `ssid`/`password` are concatenated into newline-terminated serial commands (`wifi_config {} {}\r\n`, `set ssid {}\r\n`) with **no validation** → a `\r\n` in either field **injects an arbitrary follow-up firmware command** (`reboot`, `erase_nvs`) across the IPC trust boundary. | `validate_wifi_credentials()` — WPA2 length bounds (SSID 1–32, password 8–63) **+ reject all control chars** (`char::is_control()`), called fail-closed before any serial write. |
+| WDP-DESK-02 | MODERATE | `capabilities/default.json:7-8` | `shell:allow-execute` + `shell:allow-open` granted to the webview but **unused** (Rust spawns via `std::process::Command`; the UI uses only `dialog.open`). A webview compromise (a UI-dependency XSS) → arbitrary **unscoped host command execution**. | Removed both `shell:` permissions (kept `core:default` + the two in-use `dialog:` perms); regenerated `gen/schemas/capabilities.json` now asserts `["core:default","dialog:allow-open","dialog:allow-save"]`. |
+
+Both are MODERATE (not HIGH): each requires a webview compromise or a malicious
+local caller to weaponize. The unifying lesson is **least privilege at the IPC
+boundary** — validate every webview-supplied argument that reaches a serial/FS/
+process sink, and grant only the capabilities actually exercised.
+
+### Tauri-command + capability audit (every handler)
+
+All 30+ command handlers were mapped. Only `configure_esp32_wifi` lacked input
+validation on a string that reached a command sink (WDP-DESK-01). Every
+subprocess uses `Command::new(prog).args([...])` (argv vector — no shell-string
+interpolation), so `port`/`source`/`chip`/`baud` cannot inject a second command
+even unvalidated. `tauri.conf.json` ships **no** `fs`/`http` plugin and **no**
+`"all":true`/`"$HOME/**"` scope; after WDP-DESK-02 the allowlist is minimal.
+
+### Dimensions confirmed clean (with evidence)
+
+1. **Directory traversal / arbitrary file** — path args (`firmware_path`/`wasm_path`)
+   are blobs the local user selects via the native `dialog.open` picker; settings
+   I/O is a fixed filename under `app_data_dir`. No attacker-named path sink.
+2. **Shell-string injection** — every subprocess is an argv vector; grep found no
+   shell-string interpolation anywhere.
+3. **SSRF-to-secret** — `node_ip`-built URLs target the local ESP32 mesh and return
+   only device status JSON; no credential returned to the webview.
+4. **Panic-on-input** — handlers use `.map_err(|e| e.to_string())?`; the one
+   `expect` is guarded by an `is_none()` early-return; provision/discovery
+   deserializers bounds-check every slice index (NVS size capped ≤ 4096).
+5. **Hardcoded secrets** — `ota_psk` is a per-call `Option<String>`, never embedded;
+   grep for embedded keys/tokens over `src/` is empty.
+6. **Shell plugin genuinely unused** — `tauri_plugin_shell` is `init()`-ed but its
+   `Command`/`open` API is never invoked from Rust or the TS UI (which imports only
+   `@tauri-apps/plugin-dialog`) — confirming WDP-DESK-02 is safe to remove.
+
+## Validation
+
+- `cargo check -p wifi-densepose-desktop --no-default-features` → `Finished` (Windows, MEASURED).
+- `cargo test -p wifi-densepose-desktop --no-default-features` → lib **18 → 21** (+3 validator pins:
+  `test_validate_wifi_credentials_rejects_injection` / `_rejects_out_of_range` / `_accepts_valid`),
+  integration 21/21, **0 failed**.
+- Capability narrowing MEASURED: regenerated `capabilities.json` permission set verified.
+- `python archive/v1/data/proof/verify.py` → **VERDICT: PASS**, hash `f8e76f21…46f7a`
+  unchanged (desktop off the signal proof path).
+
+## Consequences
+
+### Positive
+- An IPC serial-command-injection path and an over-broad shell capability are
+  closed in the desktop app, each pinned / verified, with the rest of the
+  30-command IPC surface attested clean.
+
+### Negative / Neutral
+- None. The removed shell capability was unused; the validator rejects only
+  malformed/hostile credentials.
+
+## Links
+- ADR-176 / ADR-177 — sibling Milestone-#9 reviews (ruview-swarm, nvsim)
+- ADR-172 — core/cli review