Authentication with requirepass in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What happens when you try to run a command without AUTH after setting requirepass?

Assume Redis is configured with requirepass mysecret. What is the output of running GET key1 without authenticating first?

Redis

GET key1

A Error: NOAUTH Authentication required.

B key1's value

C nil

D OK

💡 Hint

Think about what Redis requires before allowing commands when requirepass is set.

When requirepass is set, Redis blocks all commands except AUTH until the client authenticates. So running GET without AUTH returns an error.

❓ query_result

intermediate

What is the output of AUTH with wrong password?

If Redis is configured with requirepass mysecret, what is the output of AUTH wrongpass?

Redis

AUTH wrongpass

A +OK

B -ERR invalid password

C -ERR wrong number of arguments for 'auth' command

D -ERR Authentication required.

💡 Hint

What does Redis reply when the password is incorrect?

Redis replies with an error message indicating the password is invalid when AUTH is called with a wrong password.

📝 Syntax

advanced

Which AUTH command syntax is correct to authenticate with password 'mypassword'?

Choose the correct Redis AUTH command syntax to authenticate with password 'mypassword'.

A AUTH mypassword

B AUTH password='mypassword'

C AUTH 'mypassword'

D AUTH password mypassword

💡 Hint

AUTH command takes the password as a single argument without quotes or keywords.

The AUTH command syntax is AUTH without quotes or keywords.

🧠 Conceptual

advanced

Why is setting requirepass important in Redis?

Select the best reason why setting requirepass in Redis configuration is important.

A It compresses Redis data to save memory.

B It encrypts all data stored in Redis automatically.

C It requires clients to authenticate before running commands, protecting data.

D It enables Redis to run on multiple CPUs.

💡 Hint

Think about what security feature requirepass provides.

requirepass forces clients to authenticate before executing commands, preventing unauthorized access.

🔧 Debug

expert

Why does this Redis client fail to authenticate?

A Redis client runs these commands: 1. SET key1 value1 2. AUTH mysecret 3. GET key1 Redis is configured with requirepass mysecret. The client gets an error on the SET command. Why?

Redis

SET key1 value1
AUTH mysecret
GET key1

A Redis does not support AUTH command.

B The password 'mysecret' is incorrect.

C GET command must come before AUTH.

D The client must authenticate before running any commands, so SET fails because it runs before AUTH.

💡 Hint

Consider the order of commands and when authentication is required.

When requirepass is set, Redis blocks all commands except AUTH until the client authenticates. Running SET before AUTH causes an error.

Practice

1. What does the requirepass directive do in Redis?

easy

A. It sets a password that clients must use to authenticate before accessing Redis.

B. It disables all client connections to Redis.

C. It automatically encrypts all data stored in Redis.

D. It sets the maximum number of clients allowed to connect.

Solution

1. Step 1: Understand the purpose of requirepass

   The requirepass directive is used to protect Redis by requiring clients to authenticate with a password.

2. Step 2: Compare options with this purpose

   Only It sets a password that clients must use to authenticate before accessing Redis. describes setting a password for client authentication, matching the purpose of requirepass.

3. Final Answer:

   It sets a password that clients must use to authenticate before accessing Redis. -> Option A

4. Quick Check:

   requirepass = password protection [OK]

Hint: requirepass means password required to connect [OK]

Common Mistakes:

• Thinking requirepass disables connections
• Confusing requirepass with encryption
• Assuming requirepass limits client count

2. Which of the following is the correct way to authenticate a Redis client after requirepass is set?

easy

A. AUTH mypassword

B. LOGIN mypassword

C. CONNECT mypassword

D. PASSWORD mypassword

Solution

1. Step 1: Identify the Redis command for authentication

   Redis uses the AUTH command followed by the password to authenticate clients.

2. Step 2: Check the options for the AUTH command

   Only AUTH mypassword uses the correct AUTH command syntax.

3. Final Answer:

   AUTH mypassword -> Option A

4. Quick Check:

   AUTH command = authenticate password [OK]

Hint: Use AUTH command to send password [OK]

Common Mistakes:

• Using LOGIN instead of AUTH
• Using CONNECT or PASSWORD commands which don't exist
• Forgetting to include the password after AUTH

3. Given the Redis configuration has requirepass foobar set, what will be the output of the following commands sequence?

SET key1 value1
GET key1
AUTH foobar
GET key1

medium

A. OK
(error) NOAUTH Authentication required.
OK
"value1"

B. OK
"value1"
OK
"value1"

C. OK
(error) NOAUTH Authentication required.
(error) NOAUTH Authentication required.
"value1"

D. (error) NOAUTH Authentication required.
(error) NOAUTH Authentication required.
OK
(nil)

Solution

1. Step 1: Understand requirepass effect on commands

   When requirepass is set, all commands except AUTH fail with NOAUTH error until the client authenticates.

2. Step 2: Analyze command sequence

   SET key1 value1 fails with NOAUTH (unauthenticated). GET key1 fails with NOAUTH. AUTH foobar succeeds (OK). GET key1 returns (nil) because the key was never successfully set.

3. Final Answer:

   (error) NOAUTH Authentication required. (error) NOAUTH Authentication required. OK (nil) -> Option D

4. Quick Check:

   Pre-AUTH: NOAUTH errors; post-AUTH: (nil) since key unset [OK]

Hint: Non-AUTH commands fail with NOAUTH before successful AUTH [OK]

Common Mistakes:

• Assuming commands work before AUTH
• Thinking AUTH returns error
• Confusing order of outputs

4. You set requirepass mysecret in your Redis config. A client tries to run AUTH wrongpass followed by GET key. What is the problem and how to fix it?

medium

A. The client must restart Redis; fix by restarting server.

B. The client used wrong password; fix by using correct password with AUTH.

C. requirepass disables GET command; fix by removing requirepass.

D. The client must run AUTH after GET; fix by swapping commands.

Solution

1. Step 1: Identify the error cause

   Using a wrong password with AUTH means client is not authenticated, so GET command will fail with NOAUTH error.

2. Step 2: Correct the authentication process

   Client must provide the correct password with AUTH to authenticate and access commands like GET.

3. Final Answer:

   The client used wrong password; fix by using correct password with AUTH. -> Option B

4. Quick Check:

   Wrong password = no access; correct password fixes it [OK]

Hint: AUTH password must match requirepass exactly [OK]

Common Mistakes:

• Trying commands before successful AUTH
• Thinking requirepass disables commands permanently
• Restarting server unnecessarily

5. You want to change the Redis password without restarting the server. Which command should you use to set a new password newpass123 dynamically?

hard

A. AUTH newpass123

B. SET requirepass newpass123

C. CONFIG SET requirepass newpass123

D. CONFIG GET requirepass

Solution

1. Step 1: Understand how to change requirepass dynamically

   Redis allows changing configuration parameters at runtime using CONFIG SET command.

2. Step 2: Identify correct command to change password

   To change the password, use CONFIG SET requirepass newpass123. AUTH is for client login, SET is for keys, CONFIG GET only reads.

3. Final Answer:

   CONFIG SET requirepass newpass123 -> Option C

4. Quick Check:

   CONFIG SET changes config without restart [OK]

Hint: Use CONFIG SET requirepass to change password live [OK]

Common Mistakes:

• Using AUTH to change password
• Trying SET command for config
• Using CONFIG GET which only reads