Internet of Things-based environments collect and generate huge amounts of data about users, their activities, and their surroundings , which can disclose some sensitive information and threaten their privacy. Hence, the user's collected and handled data by IoT-based applications need to be exploited and secured in an appropriate way to protect personal data and user's privacy. Therefore, we aim at improving the data ownership, transparency, and auditability for users. To this end, we propose an end-to-end privacy-preserving framework for the IoT data using blockchain technology. The smart contract use in our framework will hence enforce the privacy requirement compliance according to the user's (i.e., data owner) privacy preferences and end-user's (i.e., data consumer) requests. To do so, we detail the design of the system architecture by introducing its core components and functionalities and highlight through an example of how it operates in a real-world use-case.