[stealth 4/4] static leakage checks, CI gates & release/QA policy

docs/stealth-leakage-checks.md

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+# Stealth Leakage Checks
+
+`scripts/stealth/check_leakage.py` scans built stealth artifacts for normal
+Lantern identifiers. It accepts APK, AAB, ZIP-like archives, and unpacked build
+directories. Archive entries are scanned recursively, and string matching checks
+UTF-8, UTF-16LE, and UTF-16BE encodings.
+
+Run the default stealth check:
+
+```sh
+make stealth-leakage-check \
+  STEALTH_LEAKAGE_PATHS="path/to/app.apk path/to/app.aab"
+```
+
+Run the stricter no-VPN variant:
+
+```sh
+make stealth-novpn-leakage-check \
+  STEALTH_LEAKAGE_PATHS="path/to/app.apk"
+```
+
+If the configured targets are absent, the Make targets skip successfully. This
+keeps normal builds and ordinary CI runs from failing on stealth-only checks.
+
+## Modes
+
+The forbidden-token config lives at
+`scripts/stealth/forbidden_tokens.json`.
+
+### `stealth` (base)
+
+Checks for normal Lantern package, brand, library, service, and organization
+identifiers; user-facing VPN strings; OAuth provider strings and method-channel
+entry points; billing and subscription entry points; app-link hosts, custom
+schemes, and deep-link paths; Lantern social/support URLs; and update feed and
+release URLs.
+
+### `stealth-vpn`
+
+Brand-only policy for the de-branded full-featured VPN variant. Checks the
+`lantern_identity` and `social_urls` categories only. Generic tokens such as
+`oauth`, `stripe`, `billing`, and `VPN` are intentionally allowed — login,
+payment, and VPN surfaces are retained in this variant. OAuth2 and the
+`lantern://` deep-link scheme are excluded at source (via `//go:build !stealth`
+build tags in `account/oauth.go`, `backend/oauth.go`, and `mobile_oauth.go`),
+so they are absent from the binary for the correct reason — not merely
+garble-encrypted. The `lantern_identity` tokens are case-insensitive substrings
+that catch all brand variants (`lantern.io`, `lantern://`, `org.getlantern.*`,
+etc.) without false positives on generic tokens.
+
+### `stealth-novpn`
+
+Scans the same brand-only token set as `stealth-vpn` (`lantern_identity` +
+`social_urls`), with an empty allowlist.
+
+VPN/TUN surfaces are **not** enforced by token scanning here. Native gomobile
+JNI class-name strings (e.g. `OverrideAndroidVPN`, `TunOptions`) cannot be
+scrubbed or scanned without breaking `FindClass` lookups at runtime. Instead,
+no-VPN VPN/TUN removal is **structural**: the Go `novpn` build tag excludes the
+tunnel code, and the no-VPN manifest declares no `VpnService`/`BIND_VPN_SERVICE`
+— verified by the manifest-diff tests, not by this leakage gate.
+
+## Scanner limitations
+
+`check_leakage` and raw `strings | grep` scan the post-garble binary. When a
+Go package is in `GARBLE_GOGARBLE` scope, garble `-literals` encrypts string
+literals at compile time, so brand strings in compiled-in garble packages are
+absent from the static binary but present at runtime. A pass from
+`check_leakage` alone is not sufficient evidence of brand removal for garbled
+packages.
+
+See `docs/stealth-builds.md` ("Garble string-literal obfuscation blind spot"
+and "Standing nm -D brand-symbol gate") for the required complementary checks.
+
+## Allowlists
+
+Each mode supports an `allowlist` in the JSON config. Allowlist entries can
+match by `token`, `category`, `location` glob, and `encoding`. Example:
+
+```json
+{
+  "token": "Lantern",
+  "location": "*.SF",
+  "reason": "example only"
+}
+```
+
+Keep allowlist entries narrow and mode-specific so real leaks still fail the
+scan.