How can you implement authentication and authorization in microservices? (2024)

Authentication verifies the identity of users or systems attempting to access resources, ensuring they are who they claim to be. It involves providing credentials such as passwords, biometric data, or digital certificates. Once authenticated, users gain access to specific services. Authorization, on the other hand, determines what actions authenticated users can perform. It involves granting or denying access based on predefined rules, roles, or attributes. Authorization ensures users only access resources they're permitted to, safeguarding system integrity and data security.

You can use keycloak identify providers for managing authentication and roles management also there is oauth2 and open id connect that are powerful when it comes to authentication and authorization

Authentication is the process of verifying the identity of a user, service, or application. The several common authentication mechanisms employed in microservices are Token-Based Authentication , OAuth2 , OpenID Connect , Certificates and API Keys.Authorization complements authentication by determining what actions an authenticated user or service is allowed to perform within the system. It involves enforcing access control policies based on the authenticated identity and associated permissions which can be implemented using techniques such as Role-Based Access Control (RBAC) , Attribute-Based Access Control (ABAC) , Policy-Based Access Control or Claims-Based Authorization.

OIDC and SAML authentication techniques are a popular choice for enabling SSO in microservices-based architectures. SAML for example requires/consists of a Service Provider (SP) and an Identity Provider (idP) like Google Workspace, Okta etc. SAML is XML-based (SAML assertion) which allows different microservices to trust the user by authenticating just once with the idP (by using the idP credentials in SP). In microservices, as expected this idP will be centralized.

Implementing authentication in microservices involves several steps. First, choose an authentication mechanism such as OAuth 2.0, OpenID Connect, or JSON Web Tokens (JWT). Next, centralize user identity management using an identity provider like LDAP, Active Directory, or a custom user store. Integrate authentication libraries or frameworks into each microservice to handle user authentication. Implement secure communication protocols like HTTPS to protect sensitive data during authentication. Lastly, enforce access control policies within microservices to ensure authenticated users only access authorized resources. Regularly update and review authentication mechanisms to address security vulnerabilities and adapt to evolving threats.

Based on my professional experience, I advocate for the utilization of gRPC as an efficient method for reducing latency in inter-service communication. Furthermore, I suggest the adoption of Internal APIs for authentication, coupled with the creation of a streamlined library for shared usage among services. It is important to acknowledge that while this approach can enhance security, it may lead to latency escalations due to SSL handshakes and associated performance impacts. Lastly, employing symmetric encryption and sharing a common private key among services warrants careful consideration for its potential implications.

In a microservices architecture, authorization is typically enforced at the service level or through a centralized authorization service. Services validate the authenticated user's identity and then check their permissions against the access control policies defined for the specific resource or operation being requested.It involves enforcing access control policies based on the authenticated identity and associated permissions which can be implemented using techniques such as Role-Based Access Control (RBAC) , Attribute-Based Access Control (ABAC) , Policy-Based Access Control or Claims-Based Authorization.

Implementing authorization in microservices involves defining access control policies for each service, specifying which users or roles can access specific resources. Use role-based access control (RBAC) or attribute-based access control (ABAC) models to manage permissions effectively. Integrate authorization logic directly into microservices, validating access requests before granting access. Ensure secure communication between microservices using protocols like HTTPS/TLS. Centralize authorization management for consistency and easier maintenance. Regularly audit and review authorization policies to address any security gaps or compliance issues.

Overcoming the challenges of authentication and authorization in microservices requires a combination of careful planning, architectural considerations, and the adoption of appropriate technologies and best practices. Some strategies to overcome challenges are centralized authentication and authorization Services ( for e.g. use identity and access management (IAM) platforms ), standardized authentication mechanisms such as OAuth2, OpenID Connect, or SAML (Security Assertion Markup Language) ,and secure communication channels ( TLS (Transport Layer Security) and mutual TLS (mTLS) authentication for service to service communications etc.