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API authentication and authorization is the user management process of verifying the identity of a user or application that is requesting access to an API. API authentication is the process of verifying the identity of the user or application making the request, while API authorization is the process of verifying that the authenticated user or application has permission to access the requested resources.
API authentication can be performed using various methods, such as providing a username and password, or using a token-based system such as OAuth or JWT. API authorization is typically performed using access tokens, which are issued to the client upon successful authentication and can be used to access specific resources for a limited period of time.
The purpose of API authentication and authorization is to ensure that only authorized users or applications are able to access the API and the resources it provides. This helps to protect sensitive data and ensures that the API is used in a manner that is consistent with its intended purpose.
API authentication and authorization are important for several use cases:
When building secure APIs, choosing the right authentication method is essential to protect sensitive data and prevent unauthorized access.
Basic authentication is one of the simplest authentication methods. It’s an HTTP-based authentication scheme that allows clients to authenticate with a server by sending a username and password in plain text as part of the HTTP request.
When a client makes a request to a server that requires basic authentication, the server responds with a 401 Unauthorized status code, which indicates that authentication is required. The response also includes a WWW-Authenticate header that specifies that the server is using basic authentication.
To authenticate, the client sends another request to the server with the authorization header included in the HTTP request header, which contains the word “Basic” followed by a base64-encoded string of the username and password. For example, “Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=” represents the credentials “username:password” encoded in base64.
While basic authentication is easy to implement, it has several security limitations. The most significant being that usernames and passwords are sent in plain text, making them susceptible to eavesdropping and man-in-the-middle attacks, amongst others.
Always use HTTPS when implementing Basic Authentication, as user credentials are sent in unencrypted plain text. Without TLS, attackers can intercept the authorization header and access protected resources.
API key-based authentication involves sending an API key along with a request. An API key is a unique identifier that is issued by the API provider to authorized users or applications and is used to identify and track API usage.
To use an API that requires key-based authentication, the user or application includes the API key as a parameter in the request, typically as a header (recommended) or as a query parameter. Using headers improves security by preventing API keys from being exposed in URLs, which may be logged or cached.
API key-based authentication provides a more secure and scalable alternative to basic authentication, since the API key can be easily revoked or regenerated if it is compromised, and it allows the API provider to monitor and provide access control to the API more granularly.
However, API key-based authentication has some limitations. For example, if an API key is compromised, an attacker can gain access to the API until the key is revoked. Additionally, API keys can be difficult to manage and distribute in large-scale environments.
TLS (Transport Layer Security) encryption is a secure method of authentication that involves encrypting the communication between a client and a server using the TLS protocol, which provides secure communication over a network by encrypting data in transit and providing authentication of the server and client.
A client initiates a secure connection with a server by sending a request to establish a TLS session. The server responds by sending its public key to the client, which uses the key to encrypt a session key that will be used to encrypt all subsequent communication between the client and server.
Once the TLS session is established, the client and server can authenticate each other using digital certificates. The server presents its certificate to the client, which verifies that the certificate was issued by a trusted certificate authority and that the certificate matches the hostname of the server. The client can also present its own certificate to the server for authentication.
TLS-based authentication provides a high level of security and is widely supported by web browsers and web servers. Mutual TLS, also known as mTLS, is a form of TLS authentication in which both the client and the server present and verify digital certificates.
Many API gateways now support mutual TLS (mTLS) for stronger two-way authentication between API clients and servers. This is especially valuable for securing internal APIs, microservices, and financial transactions.
OAuth 2.0 is an authorization framework that allows users or applications to access resources from an API without giving the API access to their credentials, such as a username and password. It is widely used to grant third-party applications access to resources on behalf of a user, without requiring the user to disclose their credentials to the third party.
It’s important to note that OAuth 2.0 is not an authentication protocol. It’s designed strictly for authorization. When identity verification is needed, it should be combined with OpenID Connect (OIDC).
OAuth 2.0 involves several roles, including the resource owner, the client, the authorization server, and the resource server. The client requests authorization from the resource owner to access resources on the resource server, which is authenticated by the authorization server.
If authorization is granted, the client receives an authorization code, which it can exchange for an access token to access the resources. This multi-step process helps prevent unauthorized access by ensuring that the token is only issued after user consent and identity verification.
OAuth 2.0 is widely used by social media platforms, cloud service providers, and other web applications to provide a secure and standardized way of granting access to resources. It offers several security advantages over traditional authentication schemes, including the ability to revoke access to a specific application or user, the ability to grant limited access to specific resources, and the ability to delegate authentication to a trusted third party.
JWTs (JSON Web Tokens) are a compact and URL-safe means of representing claims to be transferred between parties. JWTs consist of three parts separated by dots: a header, a payload, and a signature. The header specifies the algorithm used to sign the token, the payload contains the claims, and the signature is used to verify the integrity of the token.
JWTs are often used for authentication and authorization in web applications. When a user logs in, the server generates a JWT that contains information about the user, such as the client ID and permissions. The JWT is then signed using a secret key that only the server knows. The server sends the JWT to the client, which can then use it to access protected resources on the server.
While commonly used with OAuth and OIDC, JWTs are not limited to any one protocol. They can be used independently in custom token-based authentication schemes where stateless session handling is desired.
When the client sends a request to the server, it includes the JWT in an authorization header. The server verifies the signature of the JWT using the secret key, and if the signature is valid, it extracts the claims and uses them to authorize the request.
JWTs are widely used in REST APIs, as they allow the stateless transmission of authentication and authorization data between the client and the server. They are also portable, since they can be easily shared between different services and systems.
OpenID Connect (OIDC) is an authentication protocol that extends the OAuth 2.0 framework by providing an identity layer on top of it. OIDC enables users to authenticate with a web application using an identity provider, such as Google or Facebook. OIDC supports both enterprise SSO and consumer-facing logins, making it flexible for a wide range of web applications, mobile apps, and multi-tenant SaaS platforms.
OIDC provides a mechanism for requesting specific user information, such as name or email address, and allows users to grant or deny access to this information. This enables applications to tailor the user experience based on the user’s identity and preferences.
OIDC is widely used in web applications and single sign-on (SSO) systems to provide secure and easy-to-use authentication for users. It is supported by a wide range of identity providers and is built on top of existing web standards, making it easy to integrate into existing systems.
Tokens used in API authentication, especially access tokens in OAuth 2.0, are often short-lived to reduce risk. To maintain a seamless user experience without reauthentication, clients can request a refresh token during the initial auth flow. This token allows them to obtain a new access token after expiration.
Proper token management includes:
For stateless systems, it’s critical to implement token validation that checks expiration, scopes, and signatures on every API request.
Here are some best practices for ensuring secure, manageable authentication and authorization.
Create multiple API keys with different levels of access to the API, rather than using a single API key for all users or applications. If each API key has different permissions, API providers can control the level of access that each user or application has to the API.
This provides a more granular and secure approach to authentication, as it allows the API provider to restrict access to certain resources or actions based on the user’s role or level of access.
For example, an API provider might create an API key with read-only access to certain resources for a reporting application, while creating another API key with full access to all resources for an internal application.
This approach defines authorization rules based on the application’s business logic. These rules determine whether a user or application is allowed to access a resource or perform an action.
By embedding authorization into the application logic, API providers can:
This setup is typically more efficient and adaptable to real-world use cases.
For example, an eCommerce application might define authorization rules that allow only authenticated users to access their purchase history, while restricting access to other users. The application could also define rules that restrict access to certain resources based on the user’s role, such as allowing only administrators to manage user accounts.
OAuth 2 can be implemented in either a stateful or stateless mode to provide a secure and efficient way of granting access to resources. Stateful modes involve storing the user’s authentication state on the server, while stateless modes involve passing the state with the request.
Stateful mode is more secure, as it prevents unauthorized access to the user’s authentication state. However, it can also be less efficient, as it requires the server to store and manage user sessions.
Stateless mode, on the other hand, is more efficient and scalable, as it allows the server to process requests without the need for session management. However, it also requires additional security measures, such as the use of secure tokens and encrypted communications, to prevent unauthorized access to the user’s state.
SSO can be implemented using OAuth 2 and OIDC to provide a secure and user-friendly way of authenticating users across multiple applications and services. OAuth 2 provides the authorization framework, while OIDC provides the identity layer on top of it.
By implementing SSO using OAuth2 and OIDC, users can authenticate once with an identity provider and then access multiple applications and services without having to re-enter their credentials. This improves the user experience while also reducing the risk of credential theft or misuse.
OAuth2 and OIDC also provide a standardized and secure way of exchanging user information and authentication data between applications and services. This allows applications to share user data and provide a more personalized experience, while also ensuring that user data is protected and controlled.
Implement rate limiting to prevent abuse of authenticated endpoints, especially in public APIs or usage-based pricing models. Pair this with access scopes to enforce least-privilege access, ensuring each token or key only grants permission to specific API operations.
For example:
These authentication mechanisms improve both API security and resource efficiency, helping protect against misuse and maintaining consistent performance.
The industry standard today is to use authentication providers to “build the door,” but what about authorization (the door knob)? Most authentication vendors don’t go that extra mile, leaving SaaS teams to either build custom solutions from scratch or depend on fragmented third-party tools or external agencies. This often delays investment in core technology development, which negatively impacts innovation, hampers productivity, and time-to-market (TTM) metrics.
As APIs become central to product delivery, Frontegg helps modern SaaS platforms manage secure access and multi-tenant authorization with clarity, speed, and precision.
Frontegg’s end-to-end user management platform allows you to authenticate and authorize users with just a few clicks, all via a centralized dashboard that allows seamless role and permission management. Integration also takes just a few minutes, thanks to its plug-and-play nature. It’s also multi-tenant by design.
