Invalidate existing sessions on password change/reset (B-34)

Neither self-service password change nor the admin reset invalidated
already-issued JWTs — a 24h-lifetime token stayed valid regardless, so
a stolen token (or an attacker who already had the old password) kept
working past a password change meant to lock them out. The admin reset
exists precisely for the "account compromised" case and didn't evict
the attacker at all.

Add User.token_version (migration 943dbd74d983), embedded in every JWT
as a "tv" claim and checked against the DB on every request in
get_current_user/get_optional_user; a mismatch reads as session_expired.
Both change-password and the admin reset bump it. change-password hands
back a freshly minted token so the caller's own session keeps working
instead of being logged out by its own request; the admin reset does
not, since that session isn't the one making the call.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/api/routes/admin.py

@@ -215,6 +215,11 @@ async def reset_user_password(
 
     new_password = secrets.token_urlsafe(12)
     user.password_hash = hash_password(new_password)
+    # B-34: this endpoint exists precisely for the "account compromised" case —
+    # without bumping token_version, whoever was already logged in (the
+    # attacker, if that's who prompted the reset) stayed logged in on their
+    # existing token until it naturally expired, unaffected by the reset.
+    user.token_version += 1
     await write_audit_log(session, "admin_password_reset", {"user_id": user_id}, user_id=user_id)
     await session.commit()
     return AdminPasswordResetResponse(username=user.username, new_password=new_password)

app/api/routes/users.py

@@ -5,7 +5,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.errors import http_error
 from app.auth.dependencies import get_current_user
-from app.auth.security import MIN_PASSWORD_LENGTH, hash_password, verify_password
+from app.auth.security import MIN_PASSWORD_LENGTH, create_access_token, hash_password, verify_password
 from app.db.models import Round, RoundParticipant, User
 from app.db.session import get_session
 from app.wallet.balance import compute_pending_balance
@@ -45,12 +45,16 @@ class ChangePasswordRequest(BaseModel):
     new_password: str
 
 
-@router.post("/me/change-password", status_code=status.HTTP_204_NO_CONTENT)
+class ChangePasswordResponse(BaseModel):
+    access_token: str
+
+
+@router.post("/me/change-password", response_model=ChangePasswordResponse)
 async def change_password(
     body: ChangePasswordRequest,
     user: User = Depends(get_current_user),
     session: AsyncSession = Depends(get_session),
-) -> None:
+) -> ChangePasswordResponse:
     """Self-service password change — requires the current password, unlike the
     admin-only /admin/users/{id}/reset-password (which is for a user who's
     actually locked out and can't provide it)."""
@@ -67,7 +71,15 @@ async def change_password(
         )
 
     user.password_hash = hash_password(body.new_password)
+    # B-34: bumping token_version invalidates every token issued before this
+    # point — including this very request's own bearer token, and any an
+    # attacker who knew the old password might be holding. A fresh token is
+    # handed back so *this* session keeps working without forcing a re-login;
+    # every other open session (this user's other devices, or an attacker's)
+    # gets "session_expired" on its next request.
+    user.token_version += 1
     await session.commit()
+    return ChangePasswordResponse(access_token=create_access_token(user.id, user.token_version))
 
 
 class LastRoundResultResponse(BaseModel):

app/auth/dependencies.py

@@ -16,13 +16,19 @@ async def get_current_user(
     session: AsyncSession = Depends(get_session),
 ) -> User:
     try:
-        user_id = decode_access_token(credentials.credentials)
+        user_id, token_version = decode_access_token(credentials.credentials)
     except Exception as exc:
         raise http_error(status.HTTP_401_UNAUTHORIZED, "session_expired", "invalid token") from exc
 
     user = await session.scalar(select(User).where(User.id == user_id))
     if user is None:
         raise http_error(status.HTTP_401_UNAUTHORIZED, "session_expired", "user not found")
+    if user.token_version != token_version:
+        # B-34: a password change (self-service or admin reset) bumps
+        # token_version, so a token issued before it — including one an
+        # attacker who had the old password is still holding — reads as
+        # expired rather than staying valid until it naturally times out.
+        raise http_error(status.HTTP_401_UNAUTHORIZED, "session_expired", "token has been superseded")
     return user
 
 
@@ -37,7 +43,10 @@ async def get_optional_user(
     if not auth_header.startswith("Bearer "):
         return None
     try:
-        user_id = decode_access_token(auth_header.removeprefix("Bearer "))
+        user_id, token_version = decode_access_token(auth_header.removeprefix("Bearer "))
     except Exception:
         return None
-    return await session.scalar(select(User).where(User.id == user_id))
+    user = await session.scalar(select(User).where(User.id == user_id))
+    if user is None or user.token_version != token_version:
+        return None
+    return user

app/auth/routes.py

@@ -111,7 +111,9 @@ async def register(
             continue
         await session.refresh(user)
         request.app.state.electrum_listener.address_for_new_user(user.id, user.address)
-        return TokenResponse(access_token=create_access_token(user.id), address=user.address)
+        return TokenResponse(
+            access_token=create_access_token(user.id, user.token_version), address=user.address
+        )
 
     raise http_error(
         status.HTTP_409_CONFLICT,
@@ -148,4 +150,6 @@ async def login(
     # on its own, so one correct login can't be used to wipe out an IP's failure
     # count while it's mid-attack against other accounts.
     limiters.login.record_success(username_key)
-    return TokenResponse(access_token=create_access_token(user.id), address=user.address)
+    return TokenResponse(
+        access_token=create_access_token(user.id, user.token_version), address=user.address
+    )

app/auth/security.py

@@ -39,12 +39,20 @@ def verify_password(password: str, password_hash: str) -> bool:
         return False
 
 
-def create_access_token(user_id: int) -> str:
+def create_access_token(user_id: int, token_version: int = 0) -> str:
     expires_at = datetime.now(timezone.utc) + timedelta(minutes=settings.jwt_expire_minutes)
-    payload = {"sub": str(user_id), "exp": expires_at}
+    # "tv" lets get_current_user (app/auth/dependencies.py) reject a token issued
+    # before the account's password was last changed (B-34): change-password and
+    # the admin reset both bump User.token_version, so every token that still
+    # carries the old value stops working immediately instead of staying valid
+    # for up to jwt_expire_minutes after a compromise is supposedly handled.
+    payload = {"sub": str(user_id), "tv": token_version, "exp": expires_at}
     return jwt.encode(payload, settings.jwt_secret, algorithm=settings.jwt_algorithm)
 
 
-def decode_access_token(token: str) -> int:
+def decode_access_token(token: str) -> tuple[int, int]:
     payload = jwt.decode(token, settings.jwt_secret, algorithms=[settings.jwt_algorithm])
-    return int(payload["sub"])
+    # .get(..., 0) covers tokens issued before "tv" existed (pre-B-34 deploy) —
+    # they carry no claim at all, and 0 is what a freshly migrated user's
+    # token_version starts at, so those sessions keep working across the deploy.
+    return int(payload["sub"]), int(payload.get("tv", 0))

app/db/models.py

@@ -21,6 +21,12 @@ class User(Base):
     # Read cache only; must always be written in the same transaction as the
     # utxo_events rows it summarizes. Source of truth is utxo_events.
     cached_balance_sats: Mapped[int] = mapped_column(BigInteger, default=0)
+    # Embedded in every issued JWT (app/auth/security.py) and checked on every
+    # request (app/auth/dependencies.py:get_current_user). Bumped on a
+    # self-service or admin password change so every token issued before that
+    # point stops working immediately, instead of staying valid for up to
+    # jwt_expire_minutes after a compromised account's password is reset (B-34).
+    token_version: Mapped[int] = mapped_column(default=0, server_default="0")
     created_at: Mapped[datetime] = mapped_column(default=utcnow)
 
 

app/static/app.js

@@ -749,10 +749,15 @@ async function changePassword() {
 
   await withLoading(btn, t('loading.updating'), async () => {
     try {
-      await call('POST', '/users/me/change-password', {
+      const data = await call('POST', '/users/me/change-password', {
         current_password: currentPassword,
         new_password: newPassword,
       });
+      // The server just invalidated every previously issued token (B-34) —
+      // including the one this very request was authenticated with — and
+      // handed back a fresh one so this tab doesn't get logged out too.
+      token = data.access_token;
+      localStorage.setItem('plm_token', token);
       document.getElementById('settings-current-password').value = '';
       document.getElementById('settings-new-password').value = '';
       document.getElementById('settings-new-password-confirm').value = '';