fix: don't require secret if auth disabled

backend/app/core/auth.py

@@ -46,6 +46,8 @@ def _get_auth_credentials(db: Session) -> dict:
 
 def create_access_token(data: dict, expires_delta: timedelta | None = None):
     """Create a new access token."""
+    if not env_settings.secret_key:
+        raise ValueError("SECRET_KEY is not set, cannot create access tokens.")
     to_encode = data.copy()
     if expires_delta:
         expire = datetime.now(UTC) + expires_delta
@@ -81,6 +83,14 @@ def protected_route(
         detail="Could not validate credentials",
         headers={"WWW-Authenticate": "Bearer"},
     )
+
+    if not env_settings.secret_key:
+        # This is an internal server error because auth is configured but the key is missing.
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail="SECRET_KEY is not configured on the server.",
+        )
+
     try:
         payload = jwt.decode(
             token, env_settings.secret_key, algorithms=[env_settings.algorithm]

backend/app/core/config.py

@@ -29,8 +29,9 @@ class Settings(BaseSettings):
     auto_add_new_senders: bool = False
     auth_username: str | None = None
     auth_password: str | None = None
-    secret_key: str = Field(
-        ..., validation_alias=AliasChoices("SECRET_KEY", "LETTERFEED_SECRET_KEY")
+    secret_key: str | None = Field(
+        default=None,
+        validation_alias=AliasChoices("SECRET_KEY", "LETTERFEED_SECRET_KEY"),
     )
     algorithm: str = "HS256"
     access_token_expire_minutes: int = 30

backend/app/routers/auth.py

@@ -49,7 +49,13 @@ def login_for_access_token(
         )
 
     access_token_expires = timedelta(minutes=settings.access_token_expire_minutes)
-    access_token = create_access_token(
-        data={"sub": form_data.username}, expires_delta=access_token_expires
-    )
+    try:
+        access_token = create_access_token(
+            data={"sub": form_data.username}, expires_delta=access_token_expires
+        )
+    except ValueError as e:
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=str(e),
+        )
     return {"access_token": access_token, "token_type": "bearer"}