Aug 26 - Enhance security 4

CLAUDE.md

@@ -118,6 +118,8 @@ passkeeper/
 │   ├── test_session_revocation.py   # token_epoch revocation; deleted-account 401
 │   ├── test_webauthn_uv.py          # user verification required on both ceremonies
 │   ├── test_sharing_expiry.py       # expires_days fails closed
+│   ├── test_registration_privacy.py # register does not disclose account existence
+│   ├── test_emergency_visibility.py # grantor sees requests + retrievals
 │   ├── test_deploy_config.py        # nginx/gunicorn/systemd/extension packaging guards
 │   └── js/test_psl.js               # PSL same-site matching (node, run in CI)
 ├── gunicorn.conf.py         # worker class, timeouts, preload_app=False
@@ -244,6 +246,7 @@ CREATE TABLE webauthn_credentials (
 | `i9j0k1l2m3n4`   | Add expires_at to shared_items                   |
 | `j0k1l2m3n4o5`   | Add recovery_verifier (decouple recovery proof)  |
 | `k1l2m3n4o5p6`   | Add token_epoch (revoke sessions on pw change)   |
+| `l2m3n4o5p6q7`   | Add emergency vault retrieval tracking           |
 
 ---
 
@@ -301,6 +304,20 @@ CREATE TABLE webauthn_credentials (
   possession of an unlocked device must not be sufficient.
 - **Account recovery:** challenge-response via HMAC-SHA256; `enc_key_salt` NOT returned by `/recovery/data` — client must derive it by decrypting the recovery blob (proves possession of recovery code without transmitting it); challenge rotated on each `/recovery/items` call to prevent proof replay; recovery key derived with the user's email as a per-user PBKDF2 salt — legacy fixed salt `'passkeeper-recovery'` accepted transparently for codes created before this change
 - **folder_id ownership:** validated server-side on all create/update/import operations — user cannot assign items to another user's folder
+- **Registration privacy:** `POST /api/auth/register` returns an identical 202
+  whether or not the address exists, and performs an equivalent Argon2id hash on
+  both branches so timing does not reinstate the oracle. Duplicate attempts are
+  audited under `auth.register_duplicate`. Fully closing this needs email
+  verification so the address owner is told — until then the oracle is removed
+  but the owner cannot be notified.
+- **Emergency access visibility:** `accept`, `request` and `vault_retrieved` are
+  audited under BOTH parties' user_ids. `/api/auth/audit-log` filters by
+  `user_id`, so an entry written only under the acting user is invisible to the
+  other — which meant a grantee could request and retrieve a vault snapshot
+  without anything reaching the grantor. `vault_retrieved_at` /
+  `vault_retrieval_count` on `emergency_access` record every fetch. Retrieval is
+  intentionally NOT blocked after the first time (the grantor may be unable to
+  re-provision); the wait period is the gate, and the grantor can revoke.
 - **Audit logs:** never contain plaintext item names, shared item names, or vault data
 
 ---
@@ -642,6 +659,8 @@ Audit log details **never** contain plaintext item names, shared item names, or
 - `password_changed_at` lives inside `plain` (encrypted) — never in the server schema
 - WebAuthn `attachment`: `"cross-platform"` for security keys; `"platform"` for device biometrics (default)
 - `enc_vault_is_legacy` check in `EmergencyAccess.to_dict()` is pure JSON inspection — no decryption
+- Audit entries are only visible to the user_id they are written under — mirror cross-party events (use `_log_for_both` in `emergency.py`) or the other party never sees them
+- `/register` must return the SAME body and status for new and existing addresses, and hash on both paths — returning early on duplicate reinstates a timing oracle
 - Never return `str(e)` from exception handlers — log with `_log.exception(...)` and return a generic user-facing message to avoid leaking DB schema details or query fragments
 - `extension/shared/psl.js` is GENERATED — never hand-edit; run `python scripts/update_psl.py`. It must load BEFORE content.js / popup.js / background.js in every manifest
 - Never reintroduce `endsWith("." + host)` host matching anywhere in the extension — `tests/test_deploy_config.py` fails the build if it reappears
@@ -661,6 +680,7 @@ Audit log details **never** contain plaintext item names, shared item names, or
 | Module         | Action                                                 | Trigger                        |
 | -------------- | ------------------------------------------------------ | ------------------------------ |
 | `auth.py`      | `auth.register`                                        | New account                    |
+| `auth.py`      | `auth.register_duplicate`                              | Register attempt on an existing address (no email in detail) |
 | `auth.py`      | `auth.login` / `auth.login_failed`                     | Login success/fail             |
 | `auth.py`      | `auth.account_locked`                                  | Failed login lockout           |
 | `auth.py`      | `auth.mfa_enable/disable/verify`                       | TOTP actions                   |
@@ -676,6 +696,7 @@ Audit log details **never** contain plaintext item names, shared item names, or
 | `sharing.py`   | `sharing_keys.create/update`                           | ECDH key setup                 |
 | `sharing.py`   | `shared_item.create/delete/accept`                     | Sharing (detail: type + id)    |
 | `emergency.py` | `emergency_access.*`                                   | All EA state transitions       |
+| `emergency.py` | `emergency_access.accept/request/vault_retrieved`      | Logged under BOTH grantor and grantee user_ids |
 | `webauthn.py`  | `webauthn.register`                                    | Passkey registered             |
 | `webauthn.py`  | `webauthn.auth_success` / `webauthn.auth_failed`       | Passkey login attempt          |
 | `webauthn.py`  | `webauthn.rename` / `webauthn.delete`                  | Credential management          |
@@ -857,7 +878,9 @@ Features planned for future implementation. Ordered by priority within each cate
 - Autofill matching moved onto the Public Suffix List (registrable domains)
 - Share `expires_days` fails closed instead of silently meaning "never"
 - nginx `api_limit` corrected from 60r/m to 10r/s
-- pytest suite (51 tests) + PSL node test + CI jobs; `gunicorn.conf.py`;
+- Registration no longer discloses account existence (status, body and timing)
+- Emergency access: requests and vault retrievals are now visible to the grantor
+- pytest suite (66 tests) + PSL node test + CI jobs; `gunicorn.conf.py`;
   systemd watchdog removed
 
 ### High priority — user-facing

app/models/emergency_access.py

@@ -16,6 +16,10 @@ class EmergencyAccess(db.Model):
       pending  → grantor calls /deny        → ready   (reset, grantee can request again)
       pending  (wait_days elapsed)          → grantable  (grantee fetches vault)
 
+    Retrieval does not change `status`: the grant stays 'pending' so the grantor
+    keeps seeing it as active and can revoke it. What retrieval does change is
+    vault_retrieved_at / vault_retrieval_count, which the grantor's UI surfaces.
+
     Zero-knowledge: enc_vault is a JSON array of vault items re-encrypted by the grantor
     using the ECDH shared secret (grantor private key + grantee public key).
     """
@@ -40,6 +44,12 @@ class EmergencyAccess(db.Model):
     # JSON string: [{ id, name, item_type, enc_data, iv }, ...]
     enc_vault = db.Column(db.Text, nullable=True)
     created_at = db.Column(db.DateTime, default=lambda: datetime.now(timezone.utc).replace(tzinfo=None), nullable=False)
+    # Retrieval tracking — makes grantee access to the snapshot visible to the
+    # grantor. Retrieval is not blocked after the first time (the grantor may be
+    # unable to re-provision, which is the entire premise of emergency access);
+    # the wait period is the gate, and these make use of it auditable.
+    vault_retrieved_at = db.Column(db.DateTime, nullable=True)
+    vault_retrieval_count = db.Column(db.Integer, default=0, nullable=False, server_default='0')
 
     @property
     def wait_elapsed(self):
@@ -62,6 +72,10 @@ class EmergencyAccess(db.Model):
                 self.request_initiated_at.isoformat() if self.request_initiated_at else None
             ),
             'created_at': self.created_at.isoformat() if self.created_at else None,
+            'vault_retrieved_at': (
+                self.vault_retrieved_at.isoformat() if self.vault_retrieved_at else None
+            ),
+            'vault_retrieval_count': self.vault_retrieval_count or 0,
             # True when enc_vault contains items in the old format (has a plaintext
             # 'name' field instead of enc_name/iv_name). Grantor should re-provision.
             'enc_vault_is_legacy': self._enc_vault_is_legacy(),

app/routes/auth.py

@@ -131,7 +131,7 @@ def _apply_reencrypted_items(user_id: int, items, allow_partial: bool = False) -
 
 
 @auth_bp.route('/register', methods=['POST'])
-@limiter.limit('10 per minute')
+@limiter.limit('5 per minute')
 def register():
     data = request.get_json(silent=True) or {}
     email = (data.get('email') or '').strip().lower()
@@ -147,8 +147,46 @@ def register():
     if not enc_key_salt:
         return jsonify({'error': 'enc_key_salt is required'}), 400
 
+    # ── Account-existence must not be observable ────────────────────────────
+    #
+    # This used to answer 409 "Email already registered", which let anyone probe
+    # whether a given address has a PassKeeper account — a useful target list for
+    # phishing, and exactly the kind of thing a password manager should not leak.
+    #
+    # Both branches now return the identical 202 body. The wording sends the user
+    # to the sign-in page either way, which is the correct next step in both
+    # cases: registering an address that already exists is harmless because the
+    # user simply signs in with the password they already have.
+    #
+    # Timing has to match too. Creating an account runs Argon2id (deliberately
+    # slow); returning early without it would make "exists" measurably faster and
+    # reinstate the oracle through the side door. So the existing-account branch
+    # performs and discards an equivalent hash.
+    #
+    # NOTE: fully closing this needs email verification (roadmap item 4) so the
+    # address owner is told when someone tries to register it. Until then this
+    # removes the oracle but cannot notify the legitimate owner.
+    generic_response = jsonify({
+        'message': (
+            'If that email address was available, your account has been created. '
+            'Please sign in.'
+        )
+    }), 202
+
+    time.sleep(0.1)  # flatten timing across both branches
+
     if User.query.filter_by(email=email).first():
-        return jsonify({'error': 'Email already registered'}), 409
+        hash_auth_token(auth_hash)  # equalise work; result intentionally discarded
+        AuditLog.log(
+            user_id=0,  # no account to attribute this to
+            action='auth.register_duplicate',
+            resource_type='user',
+            resource_id=None,
+            detail='Registration attempted for an address that already exists',
+            ip_address=client_ip(),
+        )
+        db.session.commit()
+        return generic_response
 
     master_hash = hash_auth_token(auth_hash)
     user = User(email=email, master_hash=master_hash, enc_key_salt=enc_key_salt)
@@ -165,7 +203,7 @@ def register():
     )
     db.session.commit()
 
-    return jsonify({'message': 'Account created successfully'}), 201
+    return generic_response
 
 
 @auth_bp.route('/login', methods=['POST'])

app/routes/emergency.py

@@ -41,6 +41,39 @@ def list_emergency():
     }), 200
 
 
+def _log_for_both(ea: EmergencyAccess, action: str, grantor_detail: str,
+                  grantee_detail: str) -> None:
+    """
+    Write the audit entry twice — once under each party's user_id.
+
+    /api/auth/audit-log filters by user_id, so an entry written only under the
+    acting user is invisible to the other party. That meant a grantee could
+    request access and retrieve the vault snapshot without a single line of it
+    appearing in the grantor's own audit log or security dashboard — the person
+    whose vault it was had no way to see it had happened.
+
+    Until email notifications exist (roadmap item 4), the grantor's audit log is
+    the only channel that reaches them, so it must carry these events.
+    """
+    AuditLog.log(
+        user_id=ea.grantor_id,
+        action=action,
+        resource_type='emergency_access',
+        resource_id=ea.id,
+        detail=grantor_detail,
+        ip_address=client_ip(),
+    )
+    if ea.grantee_id and ea.grantee_id != ea.grantor_id:
+        AuditLog.log(
+            user_id=ea.grantee_id,
+            action=action,
+            resource_type='emergency_access',
+            resource_id=ea.id,
+            detail=grantee_detail,
+            ip_address=client_ip(),
+        )
+
+
 def _ea_as_grantee(ea: EmergencyAccess, grantor: 'User | None' = None) -> dict:
     if grantor is None:
         grantor = db.session.get(User, ea.grantor_id)
@@ -150,14 +183,13 @@ def accept_emergency(ea_id):
 
     ea.status = 'accepted'
     ea.grantee_id = user.id
+    db.session.flush()
 
-    AuditLog.log(
-        user_id=g.current_user_id,
-        action='emergency_access.accept',
-        resource_type='emergency_access',
-        resource_id=ea.id,
-        detail=f'Accepted emergency access invitation from grantor_id={ea.grantor_id}',
-        ip_address=client_ip(),
+    _log_for_both(
+        ea,
+        'emergency_access.accept',
+        grantor_detail=f'{ea.grantee_email} accepted your emergency access invitation',
+        grantee_detail=f'Accepted emergency access invitation from grantor_id={ea.grantor_id}',
     )
     db.session.commit()
 
@@ -221,14 +253,21 @@ def request_access(ea_id):
 
     ea.status = 'pending'
     ea.request_initiated_at = datetime.now(timezone.utc).replace(tzinfo=None)
+    db.session.flush()
 
-    AuditLog.log(
-        user_id=g.current_user_id,
-        action='emergency_access.request',
-        resource_type='emergency_access',
-        resource_id=ea.id,
-        detail=f'Requested emergency vault access from grantor_id={ea.grantor_id} (wait: {ea.wait_days}d)',
-        ip_address=client_ip(),
+    # The grantor has `wait_days` to notice and deny this. If it only appeared in
+    # the grantee's audit log they would never see it in time.
+    _log_for_both(
+        ea,
+        'emergency_access.request',
+        grantor_detail=(
+            f'ACTION REQUIRED: {ea.grantee_email} requested emergency access to '
+            f'your vault. It unlocks in {ea.wait_days} day(s) unless you deny it.'
+        ),
+        grantee_detail=(
+            f'Requested emergency vault access from grantor_id={ea.grantor_id} '
+            f'(wait: {ea.wait_days}d)'
+        ),
     )
     db.session.commit()
 
@@ -291,13 +330,25 @@ def get_emergency_vault(ea_id):
             'error': f'Wait period not yet elapsed ({days_left:.1f} day(s) remaining)'
         }), 403
 
-    AuditLog.log(
-        user_id=g.current_user_id,
-        action='emergency_access.vault_retrieved',
-        resource_type='emergency_access',
-        resource_id=ea.id,
-        detail=f'Retrieved emergency vault from grantor_id={ea.grantor_id}',
-        ip_address=client_ip(),
+    # Record the retrieval. Access is deliberately not revoked afterwards — the
+    # grantor may be unable to re-provision, and a failed import must not strand
+    # the grantee — but every retrieval is counted and shown to the grantor, who
+    # can revoke the grant outright.
+    now = datetime.now(timezone.utc).replace(tzinfo=None)
+    is_first = ea.vault_retrieved_at is None
+    if is_first:
+        ea.vault_retrieved_at = now
+    ea.vault_retrieval_count = (ea.vault_retrieval_count or 0) + 1
+
+    _log_for_both(
+        ea,
+        'emergency_access.vault_retrieved',
+        grantor_detail=(
+            f'{ea.grantee_email} retrieved your emergency vault snapshot '
+            f'({"first" if is_first else f"retrieval #{ea.vault_retrieval_count}"}). '
+            'Remove the grant if this was not expected.'
+        ),
+        grantee_detail=f'Retrieved emergency vault from grantor_id={ea.grantor_id}',
     )
     db.session.commit()
 

app/static/css/app.css

@@ -953,6 +953,25 @@ ul {
   border: 1px solid #ffb74d;
 }
 
+/* Emergency access: a pending request or a retrieved snapshot is the one thing
+   in this list the grantor must not scroll past, so it gets the strongest
+   treatment available rather than the amber used for ordinary warnings. */
+.badge-danger {
+  background: #ffebee;
+  color: #b71c1c;
+  border: 1px solid #ef9a9a;
+}
+
+.share-item.em-alert {
+  border-left: 3px solid #c62828;
+  background: #fff5f5;
+}
+
+.share-meta.em-retrieved {
+  color: #b71c1c;
+  font-weight: 500;
+}
+
 .badge-info {
   background: #e3f2fd;
   color: #1565c0;

app/static/js/vault.js

@@ -2445,6 +2445,16 @@ const Vault = (() => {
     }
   }
 
+  /**
+   * Whole days left before a pending emergency request unlocks. Mirrors the
+   * server's wait_elapsed calculation in EmergencyAccess.wait_elapsed.
+   */
+  function _emDaysRemaining(g) {
+    if (!g.request_initiated_at) return g.wait_days;
+    const elapsedMs = Date.now() - new Date(g.request_initiated_at).getTime();
+    return Math.max(0, Math.ceil(g.wait_days - elapsedMs / 86400000));
+  }
+
   function renderEmergencyGrants(grants) {
     const ul = document.getElementById("em-grants-list");
     if (!ul) return;
@@ -2471,17 +2481,32 @@ const Vault = (() => {
           }
         }
         if (g.status === "pending") {
+          // The wait period is the only thing standing between a request and
+          // the grantee reading the vault, so make the countdown explicit
+          // rather than showing a bare status word.
           const waitInfo = g.wait_elapsed
-            ? "Wait period elapsed"
-            : "Access requested";
-          actions = `<span class="badge badge-warn">${waitInfo}</span>
-          <button class="btn-secondary btn-sm" data-deny="${g.id}">Deny</button>`;
+            ? "⚠ Wait elapsed — access is available now"
+            : `⏳ Unlocks in ${_emDaysRemaining(g)} day(s)`;
+          actions = `<span class="badge badge-danger">${waitInfo}</span>
+          <button class="btn-primary btn-sm" data-deny="${g.id}">Deny</button>`;
         }
-        return `<li class="share-item">
+
+        // Retrieval is not blocked after the wait elapses, so the grantor's
+        // signal that it happened is this badge plus their audit log.
+        const retrieved = g.vault_retrieval_count
+          ? `<span class="share-meta em-retrieved">⚠ Vault retrieved ${
+              g.vault_retrieval_count
+            }&times; · first on ${new Date(
+              g.vault_retrieved_at,
+            ).toLocaleDateString()} — remove this grant if unexpected</span>`
+          : "";
+
+        return `<li class="share-item${g.status === "pending" || g.vault_retrieval_count ? " em-alert" : ""}">
         <div class="share-icon">🚨</div>
         <div class="share-info">
           <span class="share-name">${escHtml(g.grantee_email)}</span>
           <span class="share-meta">Status: ${escHtml(g.status)} · Wait: ${g.wait_days} day(s)</span>
+          ${retrieved}
         </div>
         <div class="share-actions">
           ${actions}

app/templates/auth/login.html

@@ -7,8 +7,13 @@ block body_class %}auth-page{% endblock %} {% block body %}
       <span class="logo-text">PassKeeper</span>
     </div>
 
+    <!-- Deliberately non-committal: the server returns the same response whether
+         or not the address was already registered, so that registration cannot
+         be used to probe which addresses have PassKeeper accounts. Asserting
+         "account created" here would leak what the API withholds. -->
     <p id="register-notice" class="notice-success hidden">
-      Account created! Please sign in.
+      If that email address was available, your account has been created — please sign in below.
+      Already had an account? Sign in with your existing master password.
     </p>
 
     <!-- Step 1: Email + Master Password -->

migrations/versions/l2m3n4o5p6q7_add_emergency_retrieval_tracking.py

@@ -0,0 +1,49 @@
+"""add vault retrieval tracking to emergency_access
+
+Revision ID: l2m3n4o5p6q7
+Revises: k1l2m3n4o5p6
+Create Date: 2026-08-26 00:00:00.000000
+
+Makes emergency-vault retrieval visible to the grantor.
+
+Previously GET /api/emergency/<id>/vault neither changed the record nor recorded
+anything the grantor could see: the audit entry was written under the *grantee's*
+user_id, and /api/auth/audit-log filters by user_id, so it never appeared in the
+grantor's own log. Combined with the status never advancing past 'pending', a
+grantee could re-fetch the snapshot indefinitely with nothing surfacing to the
+person whose vault it was.
+
+  vault_retrieved_at    — when the snapshot was FIRST retrieved (NULL = never)
+  vault_retrieval_count — how many times, so repeated access is visible
+
+Retrieval is deliberately NOT blocked after the first time: the whole premise of
+emergency access is that the grantor may be unable to re-provision, and a browser
+crash mid-import must not permanently strand the grantee. The wait period remains
+the gate; these columns plus the dual audit entries make use of that access
+auditable, and the grantor can still revoke with DELETE at any point.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = 'l2m3n4o5p6q7'
+down_revision = 'k1l2m3n4o5p6'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column(
+        'emergency_access',
+        sa.Column('vault_retrieved_at', sa.DateTime, nullable=True),
+    )
+    op.add_column(
+        'emergency_access',
+        sa.Column('vault_retrieval_count', sa.Integer,
+                  nullable=False, server_default='0'),
+    )
+
+
+def downgrade():
+    op.drop_column('emergency_access', 'vault_retrieval_count')
+    op.drop_column('emergency_access', 'vault_retrieved_at')

tests/conftest.py

@@ -56,8 +56,13 @@ def auth_headers(token):
 
 def make_user(client, email='user@example.com', auth_hash='AUTH-HASH-V1',
               enc_key_salt='SALT-V1'):
-    """Register + log in. Returns (access_token, refresh_token)."""
-    assert register(client, email, auth_hash, enc_key_salt).status_code == 201
+    """
+    Register + log in. Returns (access_token, refresh_token).
+
+    Registration answers 202 for both new and duplicate addresses so it cannot
+    be used to probe account existence — see test_registration_privacy.py.
+    """
+    assert register(client, email, auth_hash, enc_key_salt).status_code == 202
     res = login(client, email, auth_hash)
     assert res.status_code == 200, res.get_json()
     body = res.get_json()

tests/test_emergency_visibility.py

@@ -0,0 +1,173 @@
+"""
+Regression tests for emergency-access visibility (finding #9).
+
+Two problems, both leaving the grantor blind to activity on their own vault:
+
+  1. Audit entries were written only under the acting user's id, and
+     /api/auth/audit-log filters by user_id — so a grantee could request access
+     and retrieve the snapshot without a single line appearing in the grantor's
+     log or security dashboard.
+  2. Retrieval left no trace on the record at all: status stayed 'pending' and
+     nothing counted, so repeated fetches were indistinguishable from none.
+
+Retrieval is deliberately still permitted after the first time — the grantor may
+be unable to re-provision, which is the whole premise — so the fix is visibility
+and revocability, not blocking.
+"""
+from datetime import datetime, timedelta, timezone
+
+from app import db
+from app.models.audit_log import AuditLog
+from app.models.emergency_access import EmergencyAccess
+from tests.conftest import auth_headers, make_user
+
+GRANTOR = 'owner@example.com'
+GRANTEE = 'trusted@example.com'
+
+
+def _pair(client):
+    """Create grantor + grantee, returns (grantor_token, grantee_token)."""
+    g_token, _ = make_user(client, GRANTOR, 'HASH-O', 'SALT-O')
+    t_token, _ = make_user(client, GRANTEE, 'HASH-T', 'SALT-T')
+    return g_token, t_token
+
+
+def _grant(client, grantor_token, grantee_token, wait_days=7):
+    res = client.post('/api/emergency', headers=auth_headers(grantor_token),
+                      json={'grantee_email': GRANTEE, 'wait_days': wait_days})
+    assert res.status_code == 201, res.get_json()
+    ea_id = res.get_json()['id']
+
+    assert client.post(f'/api/emergency/{ea_id}/accept',
+                       headers=auth_headers(grantee_token)).status_code == 200
+    assert client.post(f'/api/emergency/{ea_id}/provide',
+                       headers=auth_headers(grantor_token),
+                       json={'enc_vault': '[{"id":1,"enc_data":"X","iv":"Y","enc_name":"N","iv_name":"I"}]'}
+                       ).status_code == 200
+    return ea_id
+
+
+def _grantor_log(client, token):
+    res = client.get('/api/auth/audit-log?limit=200', headers=auth_headers(token))
+    assert res.status_code == 200
+    return res.get_json()['entries']
+
+
+def _elapse_wait(ea_id):
+    """Backdate the request so the wait period has passed."""
+    ea = db.session.get(EmergencyAccess, ea_id)
+    ea.request_initiated_at = (
+        datetime.now(timezone.utc).replace(tzinfo=None)
+        - timedelta(days=ea.wait_days + 1)
+    )
+    db.session.commit()
+
+
+def test_access_request_appears_in_the_grantors_audit_log(client, app):
+    """The grantor has wait_days to notice and deny — they must be able to see it."""
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+
+    assert client.post(f'/api/emergency/{ea_id}/request',
+                       headers=auth_headers(t_token)).status_code == 200
+
+    entries = _grantor_log(client, g_token)
+    requests = [e for e in entries if e['action'] == 'emergency_access.request']
+    assert requests, 'the access request is invisible in the grantor audit log'
+    assert 'ACTION REQUIRED' in requests[0]['detail']
+    assert GRANTEE in requests[0]['detail']
+
+
+def test_vault_retrieval_appears_in_the_grantors_audit_log(client, app):
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+    _elapse_wait(ea_id)
+
+    assert client.get(f'/api/emergency/{ea_id}/vault',
+                      headers=auth_headers(t_token)).status_code == 200
+
+    entries = _grantor_log(client, g_token)
+    retrievals = [e for e in entries
+                  if e['action'] == 'emergency_access.vault_retrieved']
+    assert retrievals, 'vault retrieval is invisible in the grantor audit log'
+    assert GRANTEE in retrievals[0]['detail']
+
+
+def test_retrieval_is_counted_and_exposed_to_the_grantor(client, app):
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+    _elapse_wait(ea_id)
+
+    grants = client.get('/api/emergency', headers=auth_headers(g_token)).get_json()['grants']
+    assert grants[0]['vault_retrieval_count'] == 0
+    assert grants[0]['vault_retrieved_at'] is None
+
+    for _ in range(3):
+        assert client.get(f'/api/emergency/{ea_id}/vault',
+                          headers=auth_headers(t_token)).status_code == 200
+
+    grants = client.get('/api/emergency', headers=auth_headers(g_token)).get_json()['grants']
+    assert grants[0]['vault_retrieval_count'] == 3, 'repeated retrieval not counted'
+    assert grants[0]['vault_retrieved_at'] is not None, 'first retrieval not timestamped'
+
+
+def test_first_retrieval_timestamp_does_not_move(client, app):
+    """vault_retrieved_at records FIRST access, so it cannot be reset by re-fetching."""
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+    _elapse_wait(ea_id)
+
+    client.get(f'/api/emergency/{ea_id}/vault', headers=auth_headers(t_token))
+    first = db.session.get(EmergencyAccess, ea_id).vault_retrieved_at
+    client.get(f'/api/emergency/{ea_id}/vault', headers=auth_headers(t_token))
+    assert db.session.get(EmergencyAccess, ea_id).vault_retrieved_at == first
+
+
+def test_grantor_can_still_revoke_after_retrieval(client, app):
+    """Visibility is only useful if the grantor can act on it."""
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+    _elapse_wait(ea_id)
+    client.get(f'/api/emergency/{ea_id}/vault', headers=auth_headers(t_token))
+
+    assert client.delete(f'/api/emergency/{ea_id}',
+                         headers=auth_headers(g_token)).status_code == 200
+    assert client.get(f'/api/emergency/{ea_id}/vault',
+                      headers=auth_headers(t_token)).status_code == 404
+
+
+def test_acceptance_is_visible_to_the_grantor(client, app):
+    g_token, t_token = _pair(client)
+    _grant(client, g_token, t_token)
+
+    accepts = [e for e in _grantor_log(client, g_token)
+               if e['action'] == 'emergency_access.accept']
+    assert accepts, 'grantee acceptance is invisible to the grantor'
+
+
+def test_retrieval_before_the_wait_elapses_is_still_refused(client, app):
+    """The wait period remains the gate — none of this loosens it."""
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+
+    res = client.get(f'/api/emergency/{ea_id}/vault', headers=auth_headers(t_token))
+    assert res.status_code == 403
+    assert db.session.get(EmergencyAccess, ea_id).vault_retrieval_count == 0
+
+
+def test_denying_a_request_stops_retrieval(client, app):
+    g_token, t_token = _pair(client)
+    ea_id = _grant(client, g_token, t_token)
+    client.post(f'/api/emergency/{ea_id}/request', headers=auth_headers(t_token))
+
+    assert client.post(f'/api/emergency/{ea_id}/deny',
+                       headers=auth_headers(g_token)).status_code == 200
+    _elapse_wait(ea_id)   # even with time passed, the request was cancelled
+
+    res = client.get(f'/api/emergency/{ea_id}/vault', headers=auth_headers(t_token))
+    assert res.status_code == 403

tests/test_registration_privacy.py

@@ -0,0 +1,111 @@
+"""
+Regression tests for registration account-existence disclosure (finding #8).
+
+/register answered 409 "Email already registered", which let anyone probe
+whether a given address has a PassKeeper account — a ready-made target list for
+phishing, and precisely what /login goes out of its way not to reveal.
+
+Both branches must now be indistinguishable in status, body, and timing.
+"""
+import time
+
+from app import db
+from app.models.audit_log import AuditLog
+from app.models.user import User
+from tests.conftest import login, register
+
+
+def test_duplicate_registration_is_indistinguishable(client, app):
+    first = register(client, 'user@example.com', 'HASH-1', 'SALT-1')
+    second = register(client, 'user@example.com', 'HASH-2', 'SALT-2')
+
+    assert first.status_code == second.status_code == 202
+    assert first.get_json() == second.get_json(), (
+        'the response differs for an existing address, so it can be probed'
+    )
+
+
+def test_duplicate_registration_does_not_touch_the_existing_account(client, app):
+    """The generic response must not come at the cost of overwriting credentials."""
+    register(client, 'user@example.com', 'HASH-1', 'SALT-1')
+    original = User.query.filter_by(email='user@example.com').first()
+    original_hash, original_salt = original.master_hash, original.enc_key_salt
+
+    register(client, 'user@example.com', 'ATTACKER-HASH', 'ATTACKER-SALT')
+
+    user = User.query.filter_by(email='user@example.com').first()
+    assert user.master_hash == original_hash, 'existing credentials overwritten'
+    assert user.enc_key_salt == original_salt
+    assert User.query.filter_by(email='user@example.com').count() == 1
+
+    # The original password must still be the one that works.
+    assert login(client, 'user@example.com', 'HASH-1').status_code == 200
+    assert login(client, 'user@example.com', 'ATTACKER-HASH').status_code == 401
+
+
+def test_registration_response_does_not_name_the_cause(client, app):
+    register(client, 'user@example.com')
+    body = register(client, 'user@example.com').get_json()
+    text = ' '.join(str(v) for v in body.values()).lower()
+
+    for leak in ('already', 'exists', 'taken', 'registered account', 'duplicate'):
+        assert leak not in text, f'response body leaks existence via {leak!r}: {body}'
+
+
+def test_timing_does_not_disclose_existence(client, app):
+    """
+    Creating an account runs Argon2id, which is deliberately slow. If the
+    duplicate branch returned early it would be measurably faster and the oracle
+    would survive in the timing even though the body is identical.
+
+    Uses a loose bound: this asserts the expensive work happens on both paths,
+    not that timing is cryptographically uniform.
+    """
+    register(client, 'taken@example.com')
+
+    def elapsed(email):
+        start = time.perf_counter()
+        register(client, email)
+        return time.perf_counter() - start
+
+    new_times = [elapsed(f'fresh{i}@example.com') for i in range(3)]
+    dup_times = [elapsed('taken@example.com') for _ in range(3)]
+
+    new_avg = sum(new_times) / len(new_times)
+    dup_avg = sum(dup_times) / len(dup_times)
+    slower, faster = max(new_avg, dup_avg), min(new_avg, dup_avg)
+
+    assert slower < faster * 4, (
+        f'timing distinguishes the branches: new={new_avg:.4f}s dup={dup_avg:.4f}s'
+    )
+
+
+def test_duplicate_attempt_is_audited(client, app):
+    """Invisible to the prober, but the operator should still see the attempts."""
+    register(client, 'user@example.com')
+    register(client, 'user@example.com')
+
+    entry = (AuditLog.query.filter_by(action='auth.register_duplicate')
+             .order_by(AuditLog.id.desc()).first())
+    assert entry is not None, 'duplicate registration attempt was not audited'
+    assert 'user@example.com' not in (entry.detail or ''), (
+        'audit detail should not need the probed address to be useful'
+    )
+
+
+def test_validation_errors_still_reported(client, app):
+    """Input validation does not reveal existence, so it stays specific."""
+    assert register(client, 'not-an-email').status_code == 400
+    assert client.post('/api/auth/register', json={'email': 'a@b.co'}).status_code == 400
+    assert client.post('/api/auth/register',
+                       json={'email': 'a@b.co', 'auth_hash': 'h'}).status_code == 400
+
+
+def test_new_registration_still_creates_a_usable_account(client, app):
+    """The privacy fix must not break the happy path."""
+    assert register(client, 'fresh@example.com', 'HASH', 'SALT').status_code == 202
+    assert User.query.filter_by(email='fresh@example.com').first() is not None
+
+    res = login(client, 'fresh@example.com', 'HASH')
+    assert res.status_code == 200
+    assert res.get_json()['enc_key_salt'] == 'SALT'