Lemur user-update path stores plaintext passwords

lemur.users.service.update() writes a user's new password as plaintext to the users.password column. The User model wires bcrypt hashing to SQLAlchemy's before_insert event but registers no equivalent listener for before_update, and service.update() does not call user.hash_password() after assigning the new value. Every password change performed through the admin-gated PUT /api/1/users/<id> endpoint persists the user's password to the database in cleartext.

lemur/users/models.py:

 1# line 38
 2class User(BaseModel):
 3    __tablename__ = "users"
 4    id = Column(Integer, primary_key=True)
 5    password = Column(String(128))            # plain column, no setter, no Vault descriptor
 6 
 7# line 74
 8    def hash_password(self):
 9        if self.password:
10            self.password = bcrypt.generate_password_hash(self.password).decode("utf-8")
11 
12# line 111
13listen(User, "before_insert", hash_password)  # only before_insert is wired

lemur/users/service.py:

 1# line 46
 2def update(user_id, username, email, active, profile_picture, roles, password=None):
 3    ...
 4    user = get(user_id)
 5    user.username = username
 6    user.email = email
 7    user.active = active
 8    user.profile_picture = profile_picture
 9    if password:
10        user.password = password              # raw assignment
11    update_roles(user, roles)
12    return database.update(user)              # commits, no hashing

No before_update listener exists. User.password is a plain Column(String(128)) with no property setter that hashes on assignment. The bcrypt code path is bypassed entirely on every UPDATE statement that touches this column.

lemur/auth/views.py:323 also calls user_service.update() during SSO/OAuth login, but passes only six positional arguments. password defaults to None on that path and the if password: guard short-circuits. The bug is triggered only through the admin-only PUT handler.

When an administrator changes a user's password via PUT /api/1/users/<id>, the cleartext password is persisted to users.password. Subsequent login attempts for that user will fail (check_password calls bcrypt.check_password_hash against an unhashed value), pushing operators toward workarounds.

The more serious consequence is a defense-in-depth bypass. Bcrypt is the protection that prevents a database compromise from yielding usable credentials. With plaintext rows present, an attacker who exfiltrates the users table, a backup, a read replica, or query logs obtains directly usable login credentials — no offline cracking required. Because users reuse passwords across services, the blast radius extends beyond Lemur.

The bug specifically affects admin-driven password resets, which are the normal post-incident workflow and exactly when plaintext storage is most harmful.

1. Install Lemur with default config. Create an admin user and a target user 'alice' (created via the standard flow, password will be hashed correctly on insert).

2. Verify the initial hash:
   psql lemur -c "SELECT password FROM users WHERE username='alice';"

   Output: $2b$12$N9Q... (bcrypt hash, as expected)

3. As admin, change alice's password via the API:
   curl -X PUT https://lemur.local/api/1/users/<alice_id>
   -H "Authorization: Bearer <admin_jwt>"
   -H "Content-Type: application/json"
   -d '{
   "username": "alice",
   "email": "alice@example.com",
   "active": true,
   "profile_picture": null,
   "roles": [{"name": "operator"}],
   "password": "ProofOfConcept_2026"
   }'

4. Read the column again:
   psql lemur -c "SELECT password FROM users WHERE username='alice';"

   Output: ProofOfConcept_2026 ← plaintext, not hashed

5. Confirm the failure mode: 'alice' can no longer log in with 'ProofOfConcept_2026'
   because check_password runs bcrypt.check_password_hash() against the cleartext column.

Register the listener for both events:

 1# lemur/users/models.py
 2listen(User, "before_insert", hash_password)
 3listen(User, "before_update", hash_password)

Alternative, equivalent fix in the service layer:

 1# lemur/users/service.py, in update()
 2    if password:
 3        user.password = password
 4        user.hash_password()

The listener fix is preferred because it closes the gap for any future code path that mutates user.password.

A one-time migration is recommended to detect and re-hash any rows already stored in cleartext. Bcrypt hashes begin with $2b$, $2a$, or $2y$. Any cleartext credential should be treated as compromised — rotate it, do not just re-hash it — since it has been at rest in plaintext and may exist in backups, audit logs, and replicas.