digiRunner Foundations: Identity Authentication and API Authorization

In today’s microservices and GenAI-driven world, API security is mission-critical. This technical article series walks software developers through everything from foundational concepts to real-world implementation within the digiRunner Open Source Project—covering identity authentication (OAuth 2.0, OIDC, API Keys), authorization policies, key-lifecycle management, and compliance challenges. Each post will help you that includes best Practices, Hands-on, and Q&A originated from digiRunner API Management Platform.

Importance of Securing APIs

APIs (Application Programming Interfaces) serve as essential building blocks for modern applications, enabling seamless communication between services, devices, and users. However, their increasing adoption has also made them prime targets for cyber threats. Securing APIs is crucial for protecting sensitive data, preventing unauthorized access, and maintaining the integrity and availability of business operations.

Understanding API Vulnerabilities and Attack Vectors

APIs expose functionalities that can be exploited if not properly secured. According to OWASP API Security Top 10, common vulnerabilities include:

Broken Authentication and Unauthorized Access: APIs lacking strong authentication allow attackers to impersonate users. OpenID Connect (OIDC) mitigates this by using secure, standardized identity verification protocols.
Token Leakage and Replay Attacks: Improper handling of JWTs or API keys can expose them to interception. Implementing HTTPS, cryptographic token signing, and secure token storage prevents such leaks.
Weak Access Controls: Without proper scope-based access restrictions, users may gain elevated privileges. API Keys and JWTs help enforce fine-grained access control.

The Business Impact of Security Breaches

API security breaches can have severe repercussions, including significant financial loss, regulatory fines, loss of customer trust, and damage to brand reputation. High-profile breaches have highlighted the critical need for robust API security strategies, demonstrating that inadequate API protection can quickly escalate into costly incidents. Organizations should proactively implement robust API security mechanisms such as OIDC, JWTs, and API keys to mitigate these risks..

Role of Authentication and Authorization

Authentication: Verifies the identity of users or systems accessing an API. Common authentication mechanisms include API keys, OAuth 2.0, OpenID Connect (OIDC), and mutual TLS.
Authorization: Ensures that authenticated users or services have the appropriate permissions to access specific resources. This is typically enforced through role-based access control (RBAC), attribute-based access control (ABAC), and policy-based authorization models.

Strong authentication and authorization policies directly reduce the likelihood of OWASP-listed vulnerabilities.

Common Threats and Vulnerabilities

APIs are vulnerable to a wide array of security threats. Understanding these risks is essential for building secure and resilient API infrastructure.

Injection Attacks, Broken Authentication, and Data Exposure

Injection attacks involve malicious input aimed at executing unintended commands or accessing unauthorized data. Broken authentication occurs when authentication mechanisms are compromised, allowing unauthorized access. Data exposure happens when sensitive data is inadequately protected.

Mitigation through OIDC, API Keys, and JWT: OIDC strengthens authentication by using secure identity providers and robust authentication protocols. JWT ensures secure transmission and validation of claims, preventing unauthorized data access. API Keys facilitate controlled access, limiting the scope of operations available to a client.

Man-in-the-Middle (MITM) Attacks and Replay Attacks

MITM attacks involve attackers intercepting communication between clients and servers, while replay attacks involve attackers reusing previously captured legitimate requests or tokens.

Mitigation through JWT and API Keys: JWTs utilize cryptographic signatures, ensuring token integrity and preventing replay attacks. API keys combined with secure transmission protocols (HTTPS) help reduce the effectiveness of MITM attacks by ensuring keys are securely exchanged and validated.

Security Risks in Public and Private APIs

Public APIs are openly accessible and face higher risks of misuse and attacks, while private APIs, although restricted, can still be vulnerable to unauthorized internal or external access.

Mitigation through Client Authorization and JWT: Client Authorization (such as OAuth 2.0) ensures secure and controlled access to private APIs by defining and enforcing strict scopes and permissions. JWT provides secure and efficient token management, allowing API providers to clearly define and enforce user permissions across public and private API endpoints.

How Standards Help Mitigate These Threats

OIDC enhances authentication robustness using identity providers.
JWTs enforce token integrity with cryptographic signatures.
API Keys offer scoped and limited access, helping prevent unauthorized access and abuse.

Overview of Security Mechanisms

In the previous sections, we explored the increasing importance of securing APIs in modern digital ecosystems and examined common threats and vulnerabilities—including broken authentication, replay attacks, excessive data exposure, and insufficient access control—many of which are emphasized in the OWASP API Security Top 10.

To effectively address these risks, organizations must implement a layered security approach rooted in widely accepted industry standards. These standards not only provide reliable authentication and authorization mechanisms, but also help establish trust, enforce boundaries, and maintain token integrity across distributed API systems.

This section introduces three foundational security standards—OpenID Connect (OIDC), API Keys, and JSON Web Tokens (JWT)—and explains how they mitigate specific threats outlined in earlier chapters.

✅ OpenID Connect (OIDC): Enforcing Trust in Identity

Broken authentication and impersonation are among the most dangerous API vulnerabilities. OpenID Connect (OIDC) is an identity layer built on top of OAuth 2.0 that enables applications to authenticate users through trusted identity providers (IdPs), reducing the likelihood of unauthorized access.

Why it matters: OIDC helps prevent impersonation and unauthorized access by ensuring a user’s identity is verified through a secure, centralized mechanism.
Key components:
- ID Token: A signed JWT that carries verifiable identity information.
- UserInfo Endpoint: Allows selective retrieval of user profile attributes, minimizing overexposure of data.
- Authorization Code Flow with PKCE: Provides a secure method for exchanging tokens, especially for public clients such as mobile and SPA applications.

Learn more:

🔗 OpenID Connect (OIDC)

🔗 OIDC Mode – digiRunner Docs

✅ API Keys & Client Authorization: Managing Access Boundaries

Overly broad or undefined access control is a common weakness in API security. While not as robust as OAuth, API Keys offer a simple and effective way to manage and restrict access—when implemented with best practices.

Why it matters: Helps prevent unauthorized or excessive access by tying specific API requests to identifiable clients.
Best practices:
- Define API Key scopes and enforce expiration or usage limits.
- Associate keys with roles or permissions to restrict sensitive endpoints.
- Strengthen communication security using mutual TLS (mTLS), especially for service-to-service APIs.

📖 Learn more:

🔗 OWASP Key Management Cheat Sheet

🔗 OWASP Secrets Management Cheat Sheet

🔗 API Client – digiRunner Docs

✅ JSON Web Tokens (JWT): Ensuring Secure and Stateless Access

As discussed in Section 1.2, token replay, leakage, and tampering are serious concerns in API environments. JWTs provide a compact, cryptographically signed format to transmit claims between clients and servers.

Why it matters: JWTs ensure token integrity and allow stateless authentication and authorization across services.
Security advantages:
- Integrity: Tokens are signed with HMAC or RSA, preventing unauthorized modification.
- Efficiency: Eliminates the need for server-side session state.
- Flexibility: Allows embedding custom claims (e.g., user roles, scopes) to support granular access control.

📖 Learn more:

🔗 JWT

🔗 Token Lifecycle Management – digiRunner Docs

Together, these mechanisms form a multi-layered defense model that aligns with the threats discussed in earlier sections. OIDC tackles broken authentication by verifying identities through trusted sources; API Keys enable controlled access and help prevent over-permissioning; and JWTs maintain data integrity while supporting scalable, stateless authorization.

By adopting these standards and implementing them according to best practices, organizations can lay the foundation for a secure and resilient API ecosystem—one that is not only protected from common threats, but also aligned with modern identity and access management principles.

Conclusion

API security is an essential component of modern digital infrastructure. By understanding API vulnerabilities, mitigating common threats, and implementing strong authentication and authorization controls, organizations can protect sensitive data, comply with security regulations, and ensure the reliability of their API ecosystems. The next sections will explore advanced security strategies, including rate limiting, logging, anomaly detection, and API security testing methodologies to further enhance API protection.

digiRunner Playbook I: Introduction to API Security