Azure API Management Policies and Custom Authentication Flows – Part 2: Authentication & Authorization Deep Dive

Azure API Management Policies and Custom Authentication Flows

• Azure API Management Policies and Custom Authentication Flows – Part 1: Fundamentals
• Azure API Management Policies and Custom Authentication Flows – Part 2: Authentication & Authorization Deep Dive
• Azure API Management Policies and Custom Authentication Flows – Part 3: Custom Authentication Implementation
• Azure API Management Policies and Custom Authentication Flows – Part 4: Advanced Scenarios & Best Practices

Azure API Management Policies and Custom Authentication Flows

Part 2: Authentication & Authorization Policies Deep Dive

Authentication and authorization are the cornerstones of API security. Azure API Management provides powerful built-in policies for JWT validation, OAuth 2.0 integration, certificate-based authentication, and API key management.

JWT Token Validation

<!-- Basic JWT validation with Azure AD -->
<validate-jwt header-name="Authorization" failed-validation-httpcode="401">
    <openid-config url="https://login.microsoftonline.com/{tenant-id}/.well-known/openid_configuration" />
    <required-claims>
        <claim name="aud">
            <value>api://your-api-client-id</value>
        </claim>
    </required-claims>
</validate-jwt>

OAuth 2.0 Integration

<!-- OAuth 2.0 token introspection -->
<inbound>
    <send-request mode="new" response-variable-name="tokenValidation" timeout="10">
        <set-url>https://oauth.provider.com/token/introspect</set-url>
        <set-method>POST</set-method>
        <set-body>@($"token={context.Request.Headers.GetValueOrDefault("Authorization", "").Replace("Bearer ", "")}")
    </send-request>
    
    <choose>
        <when condition="@(((IResponse)context.Variables["tokenValidation"]).StatusCode != 200)">
            <return-response>
                <set-status code="401" reason="Unauthorized" />
                <set-body>{"error": "invalid_token"}</set-body>
            </return-response>
        </when>
    </choose>
</inbound>

Certificate-Based Authentication

<!-- Client certificate validation -->
<inbound>
    <choose>
        <when condition="@(context.Request.Certificate == null)">
            <return-response>
                <set-status code="401" reason="Unauthorized" />
                <set-body>{"error": "client_certificate_required"}</set-body>
            </return-response>
        </when>
    </choose>
</inbound>

Role-Based Access Control

<!-- RBAC implementation -->
<inbound>
    <set-variable name="requiredRole" value="@{
        string path = context.Request.Url.Path.ToLower();
        if (path.Contains("/admin/")) return "admin";
        if (context.Request.Method == "POST") return "editor";
        return "user";
    }" />
    
    <choose>
        <when condition="@{
            // Extract and validate user role from JWT
            var requiredRole = (string)context.Variables["requiredRole"];
            // Implementation depends on your token structure
            return false; // Placeholder for role validation logic
        }">
            <return-response>
                <set-status code="403" reason="Forbidden" />
                <set-body>{"error": "insufficient_privileges"}</set-body>
            </return-response>
        </when>
    </choose>
</inbound>

Coming Up Next

In Part 3, we’ll implement custom authentication flows with practical examples of multi-step authentication and external identity provider integration.

Authentication policies provide the foundation for secure API access. Master these patterns to build robust, scalable authentication systems.