AXP-Resurection/specs/005-restricted-signature-spoofing/spec.md

# Feature Specification: Restricted native signature spoofing

**Feature Branch**: `005-restricted-signature-spoofing`  
**Created**: 2026-09-15  
**Status**: Draft  
**Input**: Advance spoofing after `004` packaging: LAB Play/microG Self-Check and
Google auth fail without AXP-style restricted signature spoofing. GOLDEN capture
2026-09-15 is the behavioural oracle. Prefer modern LOS 23.2 / A16 path to the
**same end state** as AXP (not Magisk modules).

## First working stack (this phase — before `006`/`007`)

This feature closes the **first usable Google-compat stack on LAB**:

| Must work in this phase | Owner |
|-------------------------|--------|
| Official microG + GSF (PRESIGNED, F-Droid-updatable) | `004` packaging + `005` ship |
| Patched Phonesky priv-app (project-signed, disable/enable OK) | `004` + `005` ship |
| Restricted spoofing (Developer Options + grants) | **`005` core** |
| Self-Check correct signature + Play auth (no API-console mismatch) | **`005`** |
| Modern network location (BeaconDB / Ichnaea-compatible URL; not Déjà Vu NLP) | `005` validation / docs |
| `004` packaging leftovers that block a clean flashable zip | **`005` ship gate** (`REPLACE_PREBUILT`, Play FGS privapp) |

**Explicitly later (do not pull forward):**

- `006` — Insular / Yuh / Swissquote banking hard-gates  
- `007` — KernelSU-Next / SusFS / root hide  

## User Scenarios & Testing *(mandatory)*

### User Story 1 - Developer Options master switch (Priority: P1)

As the developer (and later daily-driver user), I can enable **Allow signature
spoofing** under Developer Options. When off, spoofing has no effect even if
per-app grants remain. When on, authorized apps may use spoofing after grant.

**Why this priority**: Matches GOLDEN/AXP (`settings secure allow_signature_fake`)
and constitution (not unrestricted platform fake-signature).

**Independent Test**: On LAB build with `005`, toggle the setting; read
`settings get secure allow_signature_fake` (0/1); confirm UI strings exist.

**Acceptance Scenarios**:

1. **Given** a `005` build on LAB, **When** Developer Options is opened,
   **Then** a **Signature spoofing support** category exposes **Allow signature
   spoofing** (AXP-equivalent UX).
2. **Given** the toggle is OFF, **When** an app holds a prior spoofing grant,
   **Then** spoofing has **no effect** (same as AXP documented behaviour).
3. **Given** the toggle is ON, **When** `settings get secure allow_signature_fake`
   is read, **Then** the value is `1`.

---

### User Story 2 - microG + Phonesky Self-Check signatures (Priority: P1)

As the developer, with global spoofing ON and spoofing permission granted to
microG GmsCore and patched Phonesky, microG Self-Check marks **correct
signature** for both `com.google.android.gms` and `com.android.vending`
(Companion/Play Store line), not only “installed”.

**Why this priority**: Unblocks the `004` gap that packaging alone cannot fix;
required before Play OAuth works.

**Independent Test**: LAB only; no GOLDEN modification; screenshots/log of
Self-Check before/after grants.

**Acceptance Scenarios**:

1. **Given** `004` packages present and global spoofing ON, **When**
   `FAKE_PACKAGE_SIGNATURE` is granted to GmsCore and Phonesky, **Then**
   Self-Check shows positive **correct signature** for both.
2. **Given** Self-Check, **When** the user taps the resolution for correct
   signature on Play/microG, **Then** a grant path exists (system permission UI
   or equivalent) — not a missing activity / unknown permission.
3. **Given** global spoofing OFF, **When** Self-Check runs, **Then** correct
   signature checks fail even if packages are installed.

---

### User Story 3 - Play login / auth without API-console mismatch (Priority: P1)

As the developer, after spoofing is enabled and granted for Phonesky, Google
account sign-in in Play no longer fails with
`UNREGISTERED_ON_API_CONSOLE` / “SHA-1 certificate fingerprint” mismatch caused
by presenting the project signing key as the Play identity.

**Why this priority**: Owner-observed LAB failure; AXP GOLDEN works with spoofing.

**Independent Test**: LAB logcat during Play sign-in; compare to pre-`005`
failure mode.

**Acceptance Scenarios**:

1. **Given** spoofing ON + Phonesky granted, **When** signing into Play,
   **Then** auth token acquisition does not fail with `UNREGISTERED_ON_API_CONSOLE`
   due to project cert fingerprint.
2. **Given** Play update prompts that AXP intentionally blocks, **When** the
   user tries in-app self-update, **Then** failure remains acceptable (out of
   scope to enable stock Play self-update).

---

### User Story 4 - Restricted allow-list only (Priority: P1)

As the project owner, spoofing is **not** a general capability for arbitrary
apps. Only explicitly authorized packages/signers may obtain effective spoofing
(at minimum official microG GmsCore and project-signed patched Phonesky).

**Why this priority**: Constitution: native, restricted, auditable; no LSPosed.

**Independent Test**: Attempt spoofing from a third-party test APK that requests
`FAKE_PACKAGE_SIGNATURE` without being allow-listed → denied.

**Acceptance Scenarios**:

1. **Given** global spoofing ON, **When** a non-authorized app requests
   spoofing, **Then** it cannot effectively impersonate Google/platform
   signatures.
2. **Given** documentation, **When** reviewed, **Then** the authorized set and
   how to extend it are written (for future packages if needed).

---

### User Story 5 - Survives without root (Priority: P2)

As the developer, microG and Phonesky spoofing keep working when optional root /
Zygisk-style functionality is unavailable (Compatibility MVP is rootless).

**Why this priority**: Constitution Compatibility MVP ends at `006` rootless.

**Independent Test**: LAB build without Magisk/KSU; spoofing + Self-Check still
pass.

**Acceptance Scenarios**:

1. **Given** no Magisk/KSU on the `005` validation build, **When** spoofing is
   configured, **Then** Self-Check signature lines and basic Play auth path
   still succeed.

---

### User Story 6 - First working stack ship gate (Priority: P1)

As the developer, one LAB flash of the `005` validation build includes a
**complete** first stack: packaging fixes from `004` that never landed in a
clean zip, spoofing, and documented modern location setup — without waiting for
banking (`006`) or root (`007`).

**Why this priority**: Owner: this phase must work before later features.

**Independent Test**: Single zip flash on LAB; follow quickstart; no Magisk/KSU.

**Acceptance Scenarios**:

1. **Given** the `005` artifact zip, **When** flashed to LAB, **Then** Phonesky
   registers (`pm path`) without remount hacks; APK signatures verify (no
   PRESIGNED strip).
2. **Given** that build, **When** spoofing is configured per quickstart,
   **Then** Self-Check signature lines and Play auth meet SC-003/SC-004.
3. **Given** microG Location settings, **When** configured for a modern
   Ichnaea-compatible endpoint (BeaconDB), **Then** the procedure is documented
   and does not depend on legacy UnifiedNlp backend APKs.

---

### Edge Cases

- Stock LOS 23.2 tree on `rom-dev01` has **no** `FAKE_PACKAGE_SIGNATURE` /
  `allow_signature_fake` (inventory 2026-09-15) → must port/adapt from
  AXP/EXTENDROM patterns, not “enable a hidden LOS flag”.
- Phonesky privapp XML on AXP binds permissions to **cert SHA-256 digest**; our
  project digest differs from AXP’s — XML must use **our** digest.
- Play 52.x FGS / privapp extras (`FOREGROUND_SERVICE_SYSTEM_EXEMPTED`, etc.)
  remain packaging/`004` follow-ups; `005` must not regress them.
- Disabling Play via App info remains supported (owner: useful on AXP).
- Island/work profile: spoofing grants may need to exist per user — verify at
  least owner user 0 for P1; note multi-user as follow-up if broken.

## Requirements *(mandatory)*

### Functional Requirements

- **FR-001**: ROM MUST provide a Developer Options control equivalent to AXP
  **Allow signature spoofing**, persisted as a global setting (GOLDEN:
  `settings secure allow_signature_fake`).
- **FR-002**: ROM MUST define and enforce `android.permission.FAKE_PACKAGE_SIGNATURE`
  (or AOSP-equivalent restricted spoofing permission) so PackageManager can
  honour `meta-data fake-signature` for authorized packages when the global
  toggle is ON and the permission is granted.
- **FR-003**: Spoofing MUST be restricted to an explicit allow-list of packages
  and/or signers; at minimum `com.google.android.gms` (official microG signer)
  and `com.android.vending` (project Phonesky signer). Unrestricted spoofing is
  forbidden.
- **FR-004**: With toggle ON and grants present, microG Self-Check MUST report
  positive **correct signature** for GmsCore and Phonesky/Play.
- **FR-005**: With toggle ON and Phonesky granted, Play account auth MUST NOT
  fail with `UNREGISTERED_ON_API_CONSOLE` caused by exposing the project signing
  certificate as Play’s identity.
- **FR-006**: Spoofing MUST NOT depend on Magisk, Zygisk, LSPosed, or other
  root modules.
- **FR-007**: Behaviour and UX SHOULD match GOLDEN/AXP where compatible with
  Android 16 / LOS 23.2; if the AXP patch set does not apply cleanly, redesign
  the path to the **same end state** and record deltas in `docs/a15-a16-delta.md`.
- **FR-008**: Validation MUST be LAB-only (`11231JEC207477`); GOLDEN remains
  sample-only.
- **FR-009**: Implementation MUST be attributable (source-linked patches /
  EXTENDROM/AXP/LOS references); no opaque megapatch.

- **FR-010**: The `005` validation build MUST incorporate outstanding `004`
  packaging fixes required for a clean flashable image: PRESIGNED APKs installed
  via replace-prebuilt (no v2/v3 strip), and Phonesky privapp entries needed for
  Android 16 / Play 52 FGS (e.g. system-exempted foreground service + exact
  alarm) so Play does not crash on setup/download services.
- **FR-011**: First-stack validation MUST document modern microG network
  location configuration (Ichnaea-compatible service URL such as BeaconDB); MUST
  NOT require shipping legacy UnifiedNlp backend packages (Déjà Vu, Nominatim
  NLP apps).

### Key Entities

- **Global spoofing toggle**: User-facing Developer Options switch; gates all
  spoofing effect.
- **Spoofing permission**: Per-app dangerous/runtime-style permission the user
  (or approved default path) grants to authorized packages.
- **Authorized package set**: microG GmsCore + patched Phonesky (extensible
  later under constitution rules).
- **Oracle capture**: `.local-artifacts/002-golden/20260915-spoofing-phonesky/`
  (settings, `er_*` XMLs, framework strings, dumpsys grants).

## Success Criteria *(mandatory)*

### Measurable Outcomes

- **SC-001**: On LAB, Developer Options exposes the spoofing master switch;
  `allow_signature_fake` reads `1` when enabled.
- **SC-002**: `pm` / permission APIs show `FAKE_PACKAGE_SIGNATURE` defined;
  grants visible for GmsCore and Phonesky when configured.
- **SC-003**: microG Self-Check shows **correct signature** checked for GmsCore
  and Play/Companion within one configuration session after flash.
- **SC-004**: Play sign-in logcat no longer shows `UNREGISTERED_ON_API_CONSOLE`
  fingerprint mismatch for Phonesky under the spoofed identity.
- **SC-005**: A non-allow-listed test app cannot obtain effective Google
  signature spoofing with the global toggle ON.
- **SC-007**: One LAB flash of the `005` zip boots without remount overlays for
  Phonesky; `apksigner verify` equivalent on-device package is registered; Play
  does not crash-loop on VpaService/DownloadService for missing FGS privapp
  allowlist entries.
- **SC-008**: Quickstart includes BeaconDB (or successor) location steps;
  Self-Check / location UI does not depend on empty UnifiedNlp backend lists.

## Assumptions

- `004` packaging (PRESIGNED `LOCAL_REPLACE_PREBUILT_APK_INSTALLED`, Phonesky
  patch with `fake-signature`, privapp XMLs) remains the base; `005` does not
  replace FakeStore for Play. Unmerged `004` leftovers ship in the same `005`
  validation build (single first-stack artifact).
- Default for the global toggle is **OFF** until the user enables it (AXP
  “explicitly enable” model), unless plan proves a safer first-boot prompt.
- Official microG continues to update via F-Droid same-signer; Phonesky via
  project JKS.
- Primary patch reference: AXP/EXTENDROM signature spoofing + GOLDEN 2026-09-15
  capture; inventory shows stock LOS 23.2 lacks these hooks. Spoofing MUST also
  cover modern `PackageInfo.signingInfo` (not only legacy `signatures[]`).
- Play self-update remaining broken/blocked is acceptable (AXP parity).
- Multi-user/Island spoofing parity is best-effort for P1 (user 0 first).
- MLS (Mozilla Location Service) is retired; BeaconDB (or documented successor)
  is the modern network-location endpoint for microG 0.3.x.

## Out of Scope

- KernelSU / Magisk / DenyList (`007`)
- Banking Insular hard-gates / Yuh / Swissquote (`006`)
- Call recording / FLAG_SECURE (`008`/`009`)
- Changing Phonesky to Google’s proprietary signer
- Unrestricted signature spoofing for all apps
- Reintroducing UnifiedNlp backend APKs as the primary location design