OAuth 2.0 for microservices - Architecture Diagram

System Overview - OAuth 2.0 for microservices

This system uses OAuth 2.0 to securely authorize users across multiple microservices. It ensures that users can access only the services they are allowed to, using tokens issued by a central authorization server.

Key requirements include secure token issuance, token validation by microservices, and seamless user experience without repeated logins.

Architecture Diagram

User
  |
  v
+----------------+
| Load Balancer  |
+----------------+
        |
        v
+-------------------+
| API Gateway       |
+-------------------+
   |           |
   v           v
+---------+  +---------+
| Service |  | Service |
| A       |  | B       |
+---------+  +---------+
    |           |
    v           v
+-------------------+
| Authorization     |
| Server (OAuth 2.0)|
+-------------------+
        |
        v
+----------------+
| Token Storage  |
+----------------+
        |
        v
+----------------+
| Database       |
+----------------+
        |
        v
+----------------+
| Cache (Redis)  |
+----------------+

Components

User

actor

Initiates requests and authenticates to access microservices

Load Balancer

load_balancer

Distributes incoming user requests evenly to API Gateway instances

API Gateway

api_gateway

Central entry point that validates OAuth tokens and routes requests to microservices

Service A

service

Microservice that serves specific business functionality after token validation

Service B

service

Another microservice that serves different business functionality

Authorization Server (OAuth 2.0)

authorization_server

Issues and validates OAuth 2.0 tokens for user authentication and authorization

Token Storage

database

Stores issued tokens and their metadata securely

Database

database

Stores application data accessed by microservices

Cache (Redis)

cache

Caches token validation results and frequently accessed data for performance

Request Flow - 17 Hops

User → Authorization Server (OAuth 2.0)

Authorization Server (OAuth 2.0) → Token Storage

Authorization Server (OAuth 2.0) → User

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Cache (Redis)

Cache (Redis) → API Gateway

API Gateway → Authorization Server (OAuth 2.0)

Authorization Server (OAuth 2.0) → Token Storage

Authorization Server (OAuth 2.0) → API Gateway

API Gateway → Cache (Redis)

API Gateway → Service A or Service B

Service A or Service B → Database

Database → Cache (Redis)

Service A or Service B → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Authorization Server (OAuth 2.0)

Impact:New token issuance and validation fail, blocking user authentication and authorization. Cached tokens may still allow some requests temporarily.

Mitigation:Use multiple authorization server instances with failover and replication. Cache token validation results to allow short-term continued access during failure.

Architecture Quiz - 3 Questions

Which component is responsible for issuing OAuth 2.0 tokens?

A Load Balancer

B API Gateway

C Authorization Server (OAuth 2.0)

D Service A

Design Principle

This architecture demonstrates secure, scalable authorization using OAuth 2.0 in microservices. It uses token caching to reduce latency and dependency on the authorization server for every request, improving performance and resilience.

Practice

1. What is the main purpose of using OAuth 2.0 in a microservices architecture?

easy

A. To allow microservices to securely share user permissions without sharing passwords

B. To encrypt all communication between microservices

C. To store user data centrally in one microservice

D. To replace HTTPS for secure communication

Solution

1. Step 1: Understand OAuth 2.0 role in microservices

   OAuth 2.0 is designed to delegate access without sharing user passwords, enabling secure permission sharing.

2. Step 2: Differentiate from other security methods

   OAuth 2.0 does not encrypt communication or replace HTTPS; it focuses on authorization, not data storage or transport security.

3. Final Answer:

   To allow microservices to securely share user permissions without sharing passwords -> Option A

4. Quick Check:

   OAuth 2.0 = Secure permission sharing [OK]

Hint: OAuth 2.0 is about permissions, not encryption or storage [OK]

Common Mistakes:

• Confusing OAuth 2.0 with encryption protocols
• Thinking OAuth 2.0 stores user data centrally
• Assuming OAuth 2.0 replaces HTTPS

2. Which of the following is the correct way to include an OAuth 2.0 access token in an HTTP request header?

easy

A. Auth-Token: <access_token>

B. Token: OAuth <access_token>

C. Authorization: Bearer <access_token>

D. Access: BearerToken <access_token>

Solution

1. Step 1: Recall OAuth 2.0 token header format

   The standard way to send an OAuth 2.0 token is using the Authorization header with the Bearer scheme.

2. Step 2: Verify header syntax

   Correct syntax is exactly "Authorization: Bearer <token>"; other options use incorrect header names or schemes.

3. Final Answer:

   Authorization: Bearer <access_token> -> Option C

4. Quick Check:

   OAuth token header = Authorization: Bearer [OK]

Hint: OAuth tokens go in Authorization header with Bearer prefix [OK]

Common Mistakes:

• Using wrong header names like Token or Auth-Token
• Missing the 'Bearer' keyword before the token
• Using incorrect capitalization or spacing

3. Given a microservice receiving a JWT access token, which step correctly validates the token before processing the request?

medium

A. Decrypt the token and store it in a database

B. Check token signature, verify expiration, and confirm required scopes

C. Send the token to the user service for validation every time

D. Ignore the token if the request comes from a trusted IP

Solution

1. Step 1: Understand JWT validation steps

   JWT tokens are validated by checking their signature, expiration time, and scopes to ensure authenticity and permission.

2. Step 2: Eliminate incorrect practices

   Decrypting JWT is incorrect because JWTs are signed, not encrypted; querying user service every time reduces scalability; trusting IP alone is insecure.

3. Final Answer:

   Check token signature, verify expiration, and confirm required scopes -> Option B

4. Quick Check:

   JWT validation = signature + expiry + scopes [OK]

Hint: Validate JWT by signature, expiry, and scopes locally [OK]

Common Mistakes:

• Trying to decrypt JWT instead of verifying signature
• Validating tokens by calling user service every request
• Trusting IP addresses instead of tokens

4. A microservice is failing to authenticate requests even though clients send valid OAuth 2.0 tokens. Which is the most likely cause?

medium

A. The microservice is not verifying the token signature correctly

B. The clients are sending tokens in the URL query parameters

C. The microservice is using HTTPS for communication

D. The tokens are expired but the microservice ignores expiration

Solution

1. Step 1: Analyze token verification failure

   If valid tokens are sent but authentication fails, incorrect signature verification is a common cause.

2. Step 2: Evaluate other options

   Sending tokens in URL is discouraged but may still work; HTTPS is required for security but not cause failure; ignoring expiration would allow some tokens through, not fail all.

3. Final Answer:

   The microservice is not verifying the token signature correctly -> Option A

4. Quick Check:

   Invalid signature verification = auth failure [OK]

Hint: Check token signature verification first when auth fails [OK]

Common Mistakes:

• Blaming HTTPS for authentication issues
• Assuming tokens in URL always cause failure
• Ignoring token expiration causes failure, not ignoring it

5. In a microservices system using OAuth 2.0, how can an API Gateway improve scalability and security when handling access tokens?

hard

A. By bypassing token validation to reduce latency

B. By storing all user passwords and tokens for microservices to access

C. By encrypting all tokens with a shared secret before sending to microservices

D. By centralizing token validation and forwarding only authorized requests to microservices

Solution

1. Step 1: Understand API Gateway role in OAuth 2.0

   The API Gateway can validate tokens centrally, so microservices do not need to validate tokens individually, improving performance and security.

2. Step 2: Eliminate incorrect options

   Storing passwords centrally is insecure; encrypting tokens unnecessarily adds complexity; bypassing validation reduces security and is unsafe.

3. Final Answer:

   By centralizing token validation and forwarding only authorized requests to microservices -> Option D

4. Quick Check:

   API Gateway = central token validation [OK]

Hint: Use API Gateway to validate tokens once for all microservices [OK]

Common Mistakes:

• Thinking API Gateway stores user passwords
• Assuming tokens must be encrypted again by gateway
• Skipping token validation to save time