feat: Phase 2 - Authentication and authorization (T-010 to T-013)

backend/app/dependencies/auth.py

@@ -0,0 +1,89 @@
+"""
+Authentication and RBAC dependencies for FastAPI.
+
+Provides:
+- ``get_current_user``: decodes JWT, fetches user from DB, raises 401 on failure.
+- ``require_role``: factory that returns a dependency enforcing a specific role
+  (admins always pass).
+"""
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import JWTError, jwt
+from sqlalchemy.orm import Session
+
+from app.config import settings
+from app.database import get_db
+from app.models.user import User
+
+# ---------------------------------------------------------------------------
+# OAuth2 scheme
+# ---------------------------------------------------------------------------
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")
+
+# ---------------------------------------------------------------------------
+# Current-user dependency
+# ---------------------------------------------------------------------------
+
+
+async def get_current_user(
+    token: str = Depends(oauth2_scheme),
+    db: Session = Depends(get_db),
+) -> User:
+    """Decode the JWT *token*, look up the user in *db*, and return it.
+
+    Raises :class:`~fastapi.HTTPException` **401** when:
+    - the token cannot be decoded,
+    - the ``sub`` claim is missing, or
+    - no matching active user exists in the database.
+    """
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+
+    try:
+        payload = jwt.decode(
+            token,
+            settings.SECRET_KEY,
+            algorithms=[settings.ALGORITHM],
+        )
+        username: str | None = payload.get("sub")
+        if username is None:
+            raise credentials_exception
+    except JWTError:
+        raise credentials_exception
+
+    user = db.query(User).filter(User.username == username).first()
+    if user is None:
+        raise credentials_exception
+
+    return user
+
+
+# ---------------------------------------------------------------------------
+# Role-based access control dependency
+# ---------------------------------------------------------------------------
+
+
+def require_role(required_role: str):
+    """Return a FastAPI dependency that enforces *required_role*.
+
+    The dependency allows the request to proceed when
+    ``user.role == required_role`` **or** ``user.role == "admin"``.
+    Otherwise it raises :class:`~fastapi.HTTPException` **403**.
+    """
+
+    async def role_checker(
+        current_user: User = Depends(get_current_user),
+    ) -> User:
+        if current_user.role != required_role and current_user.role != "admin":
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail="Not enough permissions",
+            )
+        return current_user
+
+    return role_checker