In this paper, we developed a Blockchain-based User Authentication Data-Sharing (BC-UADS) framework. In BC-UADS, several hospital servers form a consortium blockchain network to maintain the transparency, immutability, and authenticity of the patient's Electronic Healthcare (Record EHR) medical data. The BC-UADS framework allows doctors to share or retrieve a patient's EHR metadata from the blockchain network. Since, the metadata is stored on a blockchain platform, it is more secure and trusted for real-time applications to utilize the medical data. The data-sharing protocol of the BC-UADS framework is implemented based on Proof-of-Reputation consensus algorithm in a blockchain network. The BC-UADS framework is analyzed in the AVISPA (Automated Validation of Internet Security Protocols and Applications) tool, demonstrating that it is secure against active and passive attacks. Besides, the BC-UADS framework is provably secure in the random oracle model based on the hardness assumption of Elliptic Curve-based Computational Diffie-Hellman (ECCDH) problem. The mutual authentication property of the BC-UADS framework is analyzed in the BAN (Burrows-Abadi-Needham) logic model. We have computed the communication, execution, and storage costs of the BC-UADS framework in different security levels: 80-bit, 112-bit, 128-bit, 192-bit, and 256-bit using PBC library. The proposed BC-UADS framework is compared with the state-of-the-art schemes.