# Feature Specification: KernelSU-Next on sunfish (LAB)

**Feature Branch**: `007-kernelsu-sunfish`  
**Created**: 2026-09-15  
**Status**: In progress (LAB)  
**Session handoff**: `docs/session-20260916-handoff.md` (2026-09-16)  
**Input**: After `005` first Google-compat stack works on LAB, skip forcing a
rootless Yuh green gate. Prioritize **ReSukiSU** (not Magisk; KSU-Next only as
history) on the LineageOS 23.2 sunfish kernel, verified hide for banking UIDs,
then SusFS / TEESimulator-class LAB experiments aimed at Yuh KeyMint/RKP
failures already logged in `002`. LAB only; never GOLDEN. Personal stock
handset for banks remains an optional operator fallback outside this feature.

**Spine reminder:** product path is **our** LOS 23.2 (`003`→`004`/`005` bacon)
then `007`. Community abu/torukk ROMs and Downloads boots are reference only.

## Context / sequencing vs `006`

Constitution originally ordered a **rootless** banking baseline (`006`) before
root (`007`). Evidence already shows:

| Device | Stack | Swissquote | Yuh |
|--------|-------|------------|-----|
| GOLDEN | AXP + Magisk DenyList | PASS (owner) | FAIL — HA / “certificate invalid”; KeyMint/`HARDWARE_TYPE_UNAVAILABLE` |
| LAB (iodé A16) | No Magisk; BL locked | — | FAIL — same KeyMint/RKP class |

So a “rootless Yuh must pass” gate is **not** a credible start condition.
This feature **absorbs** the banking regression that `006` would have owned:
measure owner + Island UIDs on **our** ROM with root hidden. A separate `006`
spec may stay deferred or become a thin historical note — it must not block
`007` work.

**Explicitly later (do not pull into this feature):** call recording (`008`),
`FLAG_SECURE` (`009`), AXP UX leftovers (`010`), project signing/AVB (`011`),
incremental Graphene/AXP/Divest **hardening** ports (`012`–`013`).

## User Scenarios & Testing *(mandatory)*

### User Story 1 - Bootable rooted LAB image (Priority: P1)

As the developer, I can flash a LAB build whose kernel includes KernelSU-Next
compatible with non-GKI Linux 4.14 / sunfish, boot to the lock screen, and
confirm root is available only through the KernelSU manager to apps I approve.

**Why this priority**: Without a working integrated root path, hide/SusFS/banking
experiments cannot run on *our* ROM.

**Independent Test**: Flash LAB only; manager shows installed; `su` works for one
approved test app and fails for an unapproved app.

**Acceptance Scenarios**:

1. **Given** a `007` LAB flash, **When** the device boots, **Then** telephony,
   Wi‑Fi, and basic UI work at least as well as the last `005` image.
2. **Given** KernelSU manager, **When** root is granted to a single debug app,
   **Then** that app can obtain root and an unapproved app cannot.
3. **Given** documentation, **When** reviewed, **Then** the exact KernelSU-Next
   revision (tag/commit) used for the accepted POC is recorded for reproducibility.

---

### User Story 2 - Banking apps never get root; mounts hidden (Priority: P1)

As the developer, Yuh and Swissquote (owner and Island/work profile UIDs) are
configured so they **never** receive root, and module/overlay mounts that would
expose root or custom ROM fingerprints to those UIDs are removed or hidden —
verified by a real check, not only a UI toggle.

**Why this priority**: Constitution root architecture; Magisk DenyList on GOLDEN
is oracle-only, not our production model.

**Independent Test**: Per-UID checks (process view of mounts / root binaries)
for banking packages on user 0 and work profile; screenshots/logs stored under
artifacts.

**Acceptance Scenarios**:

1. **Given** Yuh and Swissquote installed (Aurora → Island workflow preferred),
   **When** root grant lists are reviewed, **Then** those packages are denied
   root on every relevant user ID.
2. **Given** a module or overlay that would be visible to a normal app,
   **When** the banking UID is inspected, **Then** that mount is absent or
   otherwise hidden per the verified umount/profile mechanism.
3. **Given** only a manager “hide” toggle without mount evidence, **When**
   validation runs, **Then** the story is **not** marked pass.

---

### User Story 3 - SusFS after profiles work (Priority: P2)

As the developer, once KernelSU profiles and verified hide work, I can enable a
SusFS-capable kernel/config on LAB and confirm the device still boots and that
selected path-hiding behaviours are measurable for banking UIDs.

**Why this priority**: Needed for hard banks on community sunfish reports; must
not destabilize before basic KSU works. Constitution: SusFS only after KernelSU
and application profiles work.

**Independent Test**: LAB boot + documented SusFS enablement + before/after
visibility check for at least one sensitive path from a banking or probe UID.

**Acceptance Scenarios**:

1. **Given** US1–US2 green, **When** SusFS is enabled on LAB, **Then** the
   device boots and KernelSU manager still functions.
2. **Given** SusFS on, **When** a probe from a denied banking UID runs,
   **Then** at least one previously visible root/custom indicator is hidden
   (evidence logged).
3. **Given** SusFS causes repeated spontaneous reboot or severe thermal
   instability, **When** triage completes, **Then** SusFS is reverted or pinned
   to a known-good revision before continuing banking claims.

---

### User Story 4 - Attestation / KeyMint experiment track (Priority: P1)

As the developer, I can run a **LAB-only** attestation-compatibility experiment
(TrickyStore-class or equivalent, plus any required microG hardware-attestation
toggles) aimed at the Yuh failure mode already captured in `002` (KeyMint /
`HARDWARE_TYPE_UNAVAILABLE` / “certificate invalid”), without modifying GOLDEN.

**Why this priority**: Root hide alone did not fix Yuh on GOLDEN or iodé LAB;
attestation is the open hypothesis. **Yuh PASS is mandatory** for feature
acceptance — otherwise root is not worth carrying vs NeoBackup + native
`008`/`009` and a stock banking phone.

**Independent Test**: Reproduce Yuh launch with logcat focused on `keystore2` /
KeyMint / RKP; compare to `002` baselines; diagnostic results required with artifact paths; US5 owns PASS.

**Acceptance Scenarios**:

1. **Given** `002` Yuh failure signatures, **When** the experiment stack is
   applied on LAB, **Then** a new log capture exists that either shows the same
   class of error or a clear change.
2. **Given** a candidate experiment, **When** the same attestation probe and
   bank attempt are repeated, **Then** record the before/after result, limitations
   and rollback outcome. US4 owns diagnostic evidence, not banking acceptance.
3. **Given** persistent KeyMint/RKP messages, **When** results are interpreted,
   **Then** do not infer causality or failure from those messages alone. US5
   exclusively owns the end-to-end banking acceptance decision.

---

### User Story 5 - Banking regression on our ROM (Priority: P1)

As the project owner, after hide (and any accepted SusFS/attestation experiments)
I have a written regression for **Swissquote** and **Yuh** inside Island on the
`007` LAB image: install path, profile UIDs, biometrics if used, and outcome.
Revolut/N26 remain non-blocking.

**Why this priority**: Compatibility hard-gates; replaces the deferred `006`
oracle for “does banking work on our stack”.

**Independent Test**: End-to-end on LAB only; evidence under
`/srv/rom/artifacts/007-…` (and optional laptop rsync). No GOLDEN flash/wipe.

**Acceptance Scenarios**:

1. **Given** Island (or documented equivalent), **When** Swissquote is used in
   the work profile with root denied + hide verified, **Then** Swissquote MUST PASS with a usable authenticated session, date and build id.
2. **Given** the same setup for Yuh, **When** login/attestation is attempted,
   **Then** the session MUST **PASS**; an unusable session means
   `007` is not accepted.
3. **Given** Magisk, **When** proposed as production root, **Then** it is
   rejected; Magisk A/B diagnostic builds are allowed only as temporary
   reference per constitution.

---

### Edge Cases

- KernelSU-Next revision incompatible with 4.14 → evaluate alternate pin /
  ReSukiSU only as documented POC fork, not silent default change.
- Work-profile UIDs differ from owner → hide/root denial must be tested on both.
- `path_umount` missing/broken on 4.14 → story 2 fails until backport/verify.
- Attestation modules break Play/microg → revert experiment; keep iterating
  until both banks PASS or declare `007` blocked/cancelled.
- Operator chooses a separate stock phone for banks → interim fallback only;
  does **not** satisfy the Yuh hard-gate on LAB.

## Requirements *(mandatory)*

### Functional Requirements

- **FR-001**: Project MUST integrate KernelSU-Next into the LineageOS
  23.2–compatible sunfish kernel built with the ROM (not Magisk as production
  root).
- **FR-002**: Root MUST be grantable only to explicitly approved apps; banking
  packages (at least Yuh and Swissquote) MUST never receive root on owner or
  work-profile user IDs used in the regression.
- **FR-003**: Module/overlay mounts MUST be removable or hidden from selected
  app processes, with verification beyond manager UI toggles; `path_umount` (or
  equivalent) support on this kernel MUST be confirmed or explicitly failed.
- **FR-004**: The accepted KernelSU-Next revision MUST be pinned and recorded
  (tag/commit) for reproducible builds.
- **FR-005**: SusFS MUST only be enabled after FR-001–FR-003 work on LAB; if
  enabled, boot stability and at least one measurable hide effect MUST be
  evidenced.
- **FR-006**: Evaluate an attestation candidate with exact source URL, immutable
  revision or release plus binary hash, dependencies, auditability, baseline,
  before/after evidence and rollback. KeyMint/RKP causality remains a hypothesis.
  Banking acceptance is owned solely by FR-007 / US5.
- **FR-007**: Both Yuh and Swissquote MUST PASS usable authenticated sessions in
  the LAB managed profile on the same accepted stack with root denied and hide
  verified. Failure of either bank leaves `007` incomplete or cancelled.
  N26/Revolut are non-blocking.
- **FR-008**: All flashing, kernel experiments, and attestation modules MUST
  target LAB (`11231JEC207477`) only; GOLDEN MUST remain read-only oracle.
- **FR-009**: Zygisk/LSPosed MUST NOT be introduced as the initial architecture
  unless a later feature proves no native alternative (out of default `007`
  scope).
- **FR-010**: Feature docs MUST state that deferred `006` rootless-Yuh-pass is
  not a prerequisite, and must link `002` Yuh/Swissquote evidence paths.

### Key Entities

- **LAB device**: Experimental sunfish; only flash target for `007`.
- **KernelSU profile**: Per-app (and per-user) root grant / umount policy.
- **Banking target apps**: Yuh (`com.yuh`), Swissquote (`com.swissquote.android`).
- **Managed profile**: Island (or equivalent) work user hosting banking apps.
- **Attestation experiment stack**: Optional LAB modules/toggles aimed at
  hardware attestation / KeyMint behaviour.
- **Pinned root revision**: Exact KernelSU-Next (and SusFS, if used) identifiers.

## Success Criteria *(mandatory)*

### Measurable Outcomes

- **SC-001**: LAB boots a `007` image with working selective root within one
  flash cycle after the accepted kernel build.
- **SC-002**: For Yuh and Swissquote on every tested user ID, root grant is
  denied and mount-hide is evidenced (not toggle-only) for every applicable contract checklist row, for both packages and every tested user ID; no failed or unverified mandatory row is allowed.
- **SC-003**: **Yuh PASS** on LAB Island under the `007` stack (root denied +
  verified hide + accepted SusFS/attestation experiments), with build id and
  evidence — required to close the feature.
- **SC-004**: Swissquote MUST PASS a usable authenticated session on the same
  image/stack as SC-003, with dated evidence; both are required for acceptance.
- **SC-005**: If SusFS is claimed in the release notes for this phase, LAB
  completes ≥24h soak without SusFS-driven reboot loops, or SusFS is withdrawn
  from the claim.
- **SC-006**: Artifact package contains before/after attestation probe results
  and correlated banking logs, including unresolved messages and limitations.
  Absence of a log string alone is not proof of successful attestation.
- **SC-007**: No Magisk-based production image is published as the project
  default root path.

## Assumptions

- `005` stack (microG + patched Phonesky + restricted spoofing) remains the
  userspace base on LAB before/while bringing up `007`.
- Island (already used on LAB/GOLDEN) remains the managed-profile vehicle unless
  a documented substitute is chosen during implementation planning.
- If EOL sunfish cannot satisfy Yuh even with SusFS/TrickyStore-class stacks,
  **`007` stays incomplete** (or is explicitly cancelled) — not “done with Yuh
  documented FAIL”. Rationale: without Yuh, root adds little over NeoBackup +
  native `008`/`009`; a stock handset becomes the banking plan instead.
- Operator may still use a separate stock phone as interim fallback; that does
  not count as `007` acceptance.
- Full GrapheneOS/AXP/Divest kernel hardening ports remain `013`, not this
  feature — `007` only changes the kernel as needed for KSU/SusFS/umount.
- Community sunfish LOS+KSU+SusFS reports are inspiration, not a drop-in base.

## Out of scope

- Flashing or modifying GOLDEN.
- Magisk/Magia as default project root.
- Making Revolut/N26 hard-gates.
- Call recording, FLAG_SECURE, WebView provider work, project AVB lock.
- Purchasing or provisioning a second physical phone (operator choice).