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2026-08-20 14:24:41 -04:00

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Python

"""
app/api/jwt_utils.py
--------------------
Thin wrappers around PyJWT for signing and verifying access tokens.
Access tokens are short-lived JWTs (default 60 minutes) signed with
HMAC-SHA256 using the app's SECRET_KEY. They carry only the minimum
claims needed to identify the caller:
{
"sub": "42", # user.id as string
"role": "inspector", # user.role
"tid": 3, # issuing tenant id (multi-tenant mode only)
"iat": 1710000000, # issued-at (UTC epoch)
"exp": 1710003600, # expiry (UTC epoch, 60 min later)
}
Refresh tokens are opaque random strings stored in the DB
(see app/models/api_token.py). This module only handles JWTs.
"""
import logging
from datetime import datetime, timezone, timedelta
import jwt
from flask import current_app
logger = logging.getLogger(__name__)
ACCESS_TOKEN_LIFETIME_MINUTES = 60
def _secret():
return current_app.config['SECRET_KEY']
def _current_tenant_id():
"""Resolved tenant id, or None in single-tenant / unbound contexts."""
from app.tenancy.session_binding import current_tenant_id
return current_tenant_id()
def generate_access_token(user, lifetime_minutes: int = ACCESS_TOKEN_LIFETIME_MINUTES) -> str:
"""
Create and sign a new access token for the given user.
Parameters
----------
user : User ORM instance
lifetime_minutes : Token validity window (default 60 min)
Returns
-------
str
Signed JWT string ready to include in Authorization header.
"""
now = datetime.now(timezone.utc)
payload = {
'sub': str(user.id),
'role': user.role,
'iat': now,
'exp': now + timedelta(minutes=lifetime_minutes),
}
# MT-21: bind the token to the issuing tenant. Every tenant is signed with
# the same SECRET_KEY, so without this claim a token minted at one tenant
# host verifies at another and 'sub' resolves against whichever database
# the middleware bound. Omitted in single-tenant mode so token shape is
# unchanged there.
tid = _current_tenant_id()
if tid is not None:
payload['tid'] = tid
return jwt.encode(payload, _secret(), algorithm='HS256')
def decode_access_token(token: str) -> dict | None:
"""
Decode and verify a JWT access token.
Returns the payload dict on success, or None if the token is invalid,
expired, or tampered with. Logs the failure reason at DEBUG level.
"""
try:
return jwt.decode(token, _secret(), algorithms=['HS256'])
except jwt.ExpiredSignatureError:
logger.debug('JWT decode failed: token expired')
return None
except jwt.InvalidTokenError as exc:
logger.debug('JWT decode failed: %s', exc)
return None