OCSP stapling in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is OCSP stapling in simple terms?

OCSP stapling is a way for a website to quickly prove its security certificate is still valid without making your browser check with the certificate authority every time.

beginner

Why is OCSP stapling better than traditional OCSP checks?

Because it reduces delays and saves bandwidth by letting the server send the certificate status directly, so browsers don’t have to ask the certificate authority each time.

beginner

Which nginx directive enables OCSP stapling?

The directive is ssl_stapling on; inside the server block where SSL is configured.

intermediate

What additional directive should be set with ssl_stapling on; for OCSP stapling to work properly in nginx?

You should also set ssl_stapling_verify on; to make nginx verify the OCSP response from the certificate authority.

intermediate

What files are important for OCSP stapling to work in nginx?

You need your SSL certificate file, the private key file, and the trusted certificate chain file (usually the CA bundle) for nginx to verify OCSP responses.

What does OCSP stapling help improve?

A Website loading speed and security certificate validation

B Database query performance

C User interface design

D Server hardware cooling

OCSP stapling helps by speeding up certificate validation and improving security during HTTPS connections.

Which nginx directive turns on OCSP stapling?

A ssl_certificate on;

B ssl_stapling on;

C ssl_verify_client on;

D ssl_protocols on;

The directive ssl_stapling on; enables OCSP stapling in nginx.

What must nginx verify to ensure OCSP stapling works securely?

A The OCSP response from the certificate authority

B The server's IP address

C The user's browser version

D The server's disk space

Nginx verifies the OCSP response to ensure the certificate status is valid and trustworthy.

What file is NOT needed for OCSP stapling in nginx?

A SSL private key file

B Trusted CA certificate chain file

C SSL certificate file

D User's browser cache

User's browser cache is unrelated to nginx's OCSP stapling configuration.

What problem does OCSP stapling solve?

A Increases server CPU speed

B Fixes broken HTML tags

C Avoids delays caused by browsers checking certificate status directly

D Improves database indexing

OCSP stapling avoids delays by letting the server provide certificate status, so browsers don’t check directly.

Explain how to enable OCSP stapling in nginx and why it is useful.

Think about what directives you add in the server block and the benefit to users.

Describe the files nginx needs to support OCSP stapling and their roles.

Consider what nginx needs to prove the certificate is valid and trusted.

Practice

1. What is the main purpose of enabling OCSP stapling in nginx?

easy

A. To encrypt the website traffic with a stronger cipher

B. To block unauthorized IP addresses automatically

C. To speed up HTTPS by caching the certificate status

D. To compress website content for faster loading

Solution

1. Step 1: Understand OCSP stapling concept

   OCSP stapling allows the server to cache the certificate status from the certificate authority, reducing the need for clients to query it directly.

2. Step 2: Identify the main benefit in nginx

   This caching speeds up HTTPS connections by reducing latency and improving performance.

3. Final Answer:

   To speed up HTTPS by caching the certificate status -> Option C

4. Quick Check:

   OCSP stapling = speed up HTTPS [OK]

Hint: OCSP stapling caches cert status to speed HTTPS [OK]

Common Mistakes:

• Confusing OCSP stapling with encryption methods
• Thinking it blocks IP addresses
• Assuming it compresses website content

2. Which of the following is the correct nginx directive to enable OCSP stapling?

easy

A. ssl_ocsp on;

B. ssl_stapling_enable true;

C. ssl_ocsp_stapling enable;

D. ssl_stapling on;

Solution

1. Step 1: Recall nginx directive syntax for OCSP stapling

   The correct directive to enable OCSP stapling in nginx is ssl_stapling on;.

2. Step 2: Check each option for syntax correctness

   Options A, B, and C use incorrect directive names or syntax.

3. Final Answer:

   ssl_stapling on; -> Option D

4. Quick Check:

   Enable OCSP stapling with ssl_stapling on; [OK]

Hint: Use ssl_stapling on; to enable OCSP stapling [OK]

Common Mistakes:

• Using incorrect directive names like ssl_ocsp
• Adding extra words like _enable or enable
• Using true/false instead of on/off

3. Given this nginx snippet, what will happen if ssl_stapling is enabled but resolver is not set?

server {
  listen 443 ssl;
  ssl_certificate /etc/ssl/cert.pem;
  ssl_certificate_key /etc/ssl/key.pem;
  ssl_stapling on;
}

medium

A. nginx will log errors but continue running without stapling

B. nginx will fail to start due to missing resolver

C. OCSP stapling will be disabled silently

D. OCSP stapling will work normally without issues

Solution

1. Step 1: Understand resolver role in OCSP stapling

   nginx needs a DNS resolver configured to fetch OCSP responses from the certificate authority.

2. Step 2: Analyze behavior without resolver

   If no resolver is set, nginx cannot fetch OCSP responses, so it logs errors but continues running without stapling.

3. Final Answer:

   nginx will log errors but continue running without stapling -> Option A

4. Quick Check:

   Missing resolver = errors logged, no stapling [OK]

Hint: Missing resolver logs errors, disables stapling silently [OK]

Common Mistakes:

• Assuming nginx fails to start
• Thinking stapling works without resolver
• Believing stapling disables silently without logs

4. You enabled ssl_stapling on; and set a resolver, but nginx still does not staple OCSP responses. What is the most likely cause?

medium

A. The SSL certificate does not include the OCSP responder URL

B. The ssl_certificate_key file is missing

C. The server is listening on port 80 instead of 443

D. The ssl_protocols directive is missing

Solution

1. Step 1: Check prerequisites for OCSP stapling

   OCSP stapling requires the SSL certificate to include an OCSP responder URL to fetch status.

2. Step 2: Identify why stapling fails despite correct config

   If the certificate lacks the OCSP responder URL, nginx cannot get the status, so stapling fails.

3. Final Answer:

   The SSL certificate does not include the OCSP responder URL -> Option A

4. Quick Check:

   Missing OCSP URL in cert = stapling fails [OK]

Hint: Cert must have OCSP URL for stapling to work [OK]

Common Mistakes:

• Thinking missing key file causes stapling failure
• Confusing HTTP port with SSL port
• Assuming ssl_protocols affects stapling directly

5. You want to enable OCSP stapling in nginx with these requirements: - Use Google's public DNS resolver - Enable stapling - Ensure nginx reloads config safely Which configuration snippet correctly achieves this?

server {
  listen 443 ssl;
  ssl_certificate /etc/ssl/cert.pem;
  ssl_certificate_key /etc/ssl/key.pem;
  # Your config here
}

hard

A. resolver 8.8.8.8;
ssl_stapling off;
ssl_stapling_verify on;

B. resolver 8.8.8.8 8.8.4.4 valid=300s;
ssl_stapling on;
ssl_stapling_verify on;

C. ssl_stapling on;
ssl_stapling_verify off;
resolver 1.1.1.1;

D. resolver 8.8.8.8 8.8.4.4;
ssl_stapling on;
ssl_stapling_verify off;

Solution

1. Step 1: Set resolver with Google's DNS and validity

   Use resolver 8.8.8.8 8.8.4.4 valid=300s; to specify DNS servers and cache time.

2. Step 2: Enable OCSP stapling and verification

   Set ssl_stapling on; and ssl_stapling_verify on; to enable stapling and verify OCSP responses.

3. Step 3: Confirm safe reload

   After config changes, run nginx -t to test and nginx -s reload to reload safely.

4. Final Answer:

   resolver 8.8.8.8 8.8.4.4 valid=300s; ssl_stapling on; ssl_stapling_verify on; -> Option B

5. Quick Check:

   Correct resolver + stapling on + verify on = resolver 8.8.8.8 8.8.4.4 valid=300s; ssl_stapling on; ssl_stapling_verify on; [OK]

Hint: Use resolver with valid=, enable stapling and verify on [OK]

Common Mistakes:

• Forgetting ssl_stapling_verify on
• Using only one resolver without valid time
• Disabling stapling or verification accidentally