Basic authentication in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this command to create a password file?

You run the command htpasswd -c /etc/nginx/.htpasswd user1 and enter the password pass123. What will be the content format of the file /etc/nginx/.htpasswd?

Nginx

htpasswd -c /etc/nginx/.htpasswd user1

A A file with the username and an encrypted password hash, e.g., user1:$apr1$randomhash

B A JSON file containing username and password fields

C A plain text file with the username and password separated by a colon, e.g., user1:pass123

D An XML file with user credentials inside tags

💡 Hint

The password is not stored in plain text but hashed for security.

The htpasswd command creates a file where the password is stored as a hash, not plain text. This is to keep passwords secure.

❓ Configuration

intermediate

Which nginx configuration snippet correctly enables basic authentication for /admin path?

You want to protect the /admin URL path with basic authentication using the password file at /etc/nginx/.htpasswd. Which configuration snippet will work?

A

location /admin {
  auth_basic "Restricted Area";
  auth_basic_user_file /etc/nginx/.htpasswd;
  allow all;
}

B

location /admin {
  auth_basic "Restricted Area";
  auth_basic_user_file /etc/nginx/passwd;
}

C

location /admin {
  auth_basic "Restricted Area";
  auth_basic_user_file /etc/nginx/.htpasswd;
}

D

location /admin {
  auth_basic_user_file /etc/nginx/.htpasswd;
  auth_basic off;
}

💡 Hint

Check that auth_basic is enabled and the correct file path is used.

Option C correctly enables basic authentication with a realm name and points to the correct password file. Option C disables auth_basic. Option C uses a wrong file path. Option C includes an unnecessary 'allow all;' directive.

❓ Troubleshoot

advanced

Why does nginx ignore basic authentication despite correct config?

You configured nginx with basic authentication for /secure path, but users can access it without a password prompt. What is the most likely cause?

A The auth_basic directive is inside a location block but the location is overridden by another location without auth_basic.

B The password file /etc/nginx/.htpasswd is empty.

C The nginx service was restarted after configuration changes.

D The client browser does not support basic authentication.

💡 Hint

Check if another location block matches the request without authentication.

If another location block matches the request and does not have auth_basic enabled, nginx will serve that block without authentication, ignoring the intended protection.

🔀 Workflow

advanced

What is the correct workflow to enable basic authentication on nginx?

Arrange the steps in the correct order to enable basic authentication on nginx for a website.

A 2,1,3,4

B 1,2,3,4

C 1,3,2,4

D 2,3,1,4

💡 Hint

Think about creating credentials before telling nginx to use them.

You first create the password file, then configure nginx to use it, reload nginx to apply, and finally test the setup.

✅ Best Practice

expert

Which practice improves security when using basic authentication with nginx?

Basic authentication sends credentials encoded but not encrypted. Which practice best improves security when using it?

A Disable logging in nginx to avoid recording authentication attempts.

B Use longer usernames and passwords in the htpasswd file.

C Store the password file in the web root directory for easy access.

D Use HTTPS (TLS) to encrypt the connection so credentials are protected in transit.

💡 Hint

Think about protecting data sent over the network.

Basic authentication credentials are only base64 encoded, not encrypted. Using HTTPS encrypts the entire connection, protecting credentials from being intercepted.

Practice

1. What is the main purpose of basic authentication in nginx?

easy

A. To speed up the website loading time

B. To encrypt all website traffic automatically

C. To require users to enter a username and password before accessing content

D. To block all users except the server admin

Solution

1. Step 1: Understand basic authentication purpose

   Basic authentication prompts users for a username and password to restrict access.

2. Step 2: Compare options

   Only To require users to enter a username and password before accessing content describes this login prompt function; others describe unrelated features.

3. Final Answer:

   To require users to enter a username and password before accessing content -> Option C

4. Quick Check:

   Basic authentication = login prompt [OK]

Hint: Basic auth means login prompt for access control [OK]

Common Mistakes:

• Confusing basic auth with encryption
• Thinking it speeds up the site
• Assuming it blocks all users except admin

2. Which nginx directive is used to enable basic authentication in a server block?

easy

A. auth_basic_user_file

B. auth_user_file

C. basic_auth_enable

D. auth_basic

Solution

1. Step 1: Identify the directive for enabling basic auth

   The directive auth_basic enables basic authentication and sets the login prompt message.

2. Step 2: Check other directives

   auth_basic_user_file is incorrect; the correct directive for the password file is auth_basic_user_file but the enabling directive is auth_basic.

3. Final Answer:

   auth_basic -> Option D

4. Quick Check:

   Enable basic auth = auth_basic [OK]

Hint: Enable basic auth with auth_basic directive [OK]

Common Mistakes:

• Using auth_basic_user_file to enable auth
• Confusing directive names
• Using non-existent directives

3. Given this nginx config snippet:

location /secure/ {
  auth_basic "Restricted Area";
  auth_basic_user_file /etc/nginx/.htpasswd;
}

What happens when a user tries to access /secure/?

medium

A. User is prompted for username and password

B. User is redirected to /etc/nginx/.htpasswd

C. User accesses content without any prompt

D. User gets a 404 Not Found error

Solution

1. Step 1: Analyze auth_basic directive

   The auth_basic directive enables a login prompt with the message "Restricted Area".

2. Step 2: Analyze auth_basic_user_file directive

   The auth_basic_user_file points to the password file used to verify credentials.

3. Step 3: Determine user experience

   When accessing /secure/, the user is asked for username and password to proceed.

4. Final Answer:

   User is prompted for username and password -> Option A

5. Quick Check:

   auth_basic + user_file = login prompt [OK]

Hint: auth_basic triggers login prompt on matching location [OK]

Common Mistakes:

• Thinking user is redirected to password file
• Assuming no prompt appears
• Expecting 404 error without reason

4. You configured basic authentication but users are not prompted for credentials. Which is the most likely error?

medium

A. Missing auth_basic directive in the location block

B. Password file has wrong permissions

C. Using HTTP instead of HTTPS

D. Incorrect server_name directive

Solution

1. Step 1: Check required directives for basic auth

   Both auth_basic and auth_basic_user_file are needed; missing auth_basic disables the prompt.

2. Step 2: Evaluate other options

   Wrong permissions cause errors but usually show 500 errors; HTTP vs HTTPS affects security but not prompt; server_name unrelated.

3. Final Answer:

   Missing auth_basic directive in the location block -> Option A

4. Quick Check:

   No auth_basic = no login prompt [OK]

Hint: Always include auth_basic to enable prompt [OK]

Common Mistakes:

• Ignoring missing auth_basic directive
• Blaming HTTPS for prompt absence
• Confusing server_name with auth settings

5. You want to protect only the /admin path with basic authentication but allow /admin/public without login. Which nginx config achieves this?

hard

A. Use location /admin/public/ { auth_basic "Admin Area"; } and location /admin/ { auth_basic off; }

B. Use location /admin/ { auth_basic "Admin Area"; auth_basic_user_file /etc/nginx/.htpasswd; } and location /admin/public/ { auth_basic off; }

C. Use location /admin/ { auth_basic off; } only

D. Use location /admin/public/ { auth_basic_user_file /etc/nginx/.htpasswd; } only

Solution

1. Step 1: Protect /admin path with basic auth

   Set auth_basic and auth_basic_user_file in location /admin/ to require login.

2. Step 2: Disable auth for /admin/public

   Override with auth_basic off; in location /admin/public/ to allow open access.

3. Step 3: Confirm correct order and specificity

   More specific location /admin/public/ disables auth, while parent /admin/ requires it.

4. Final Answer:

   Use location /admin/ with auth_basic and location /admin/public/ with auth_basic off -> Option B

5. Quick Check:

   Parent location auth + child location off = selective protection [OK]

Hint: Disable auth in child location with auth_basic off [OK]

Common Mistakes:

• Reversing auth_basic on/off in locations
• Not using auth_basic off to disable
• Only configuring one location