Authentication with requirepass in Redis - Step-by-Step Execution

Concept Flow - Authentication with requirepass

Start Redis Server

↓

Check requirepass set?

No→Allow all commands

Yes↓

Client connects

↓

Client sends AUTH command with password

↓

Check password correctness

↓

Allow commands

↓

Client executes allowed commands

↓

End or disconnect

This flow shows how Redis checks if a password is set, then requires clients to authenticate before allowing commands.

Execution Sample

Redis

requirepass mysecret
Client: AUTH mysecret
Client: SET key value
Client: GET key

This example shows a Redis server requiring a password, client authenticating, then setting and getting a key.

Execution Table

Step	Action	Input/Command	Check	Result	Client Allowed?
1	Start Redis server	requirepass mysecret	Is requirepass set?	Yes	No commands allowed until AUTH
2	Client connects	CONNECT	N/A	Connection accepted	No commands allowed until AUTH
3	Client sends AUTH	AUTH mysecret	Password matches?	Yes	Commands allowed
4	Client sends SET	SET key value	Authenticated?	Yes	Command executed, key set
5	Client sends GET	GET key	Authenticated?	Yes	Command executed, value returned
6	Client sends AUTH wrongpass	AUTH wrongpass	Password matches?	No	Command rejected with error
7	Client sends GET without AUTH	GET key	Authenticated?	No	Command rejected with error

💡 Commands are only allowed after successful AUTH; wrong or missing password causes rejection.

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7
Authenticated	False	True	True	True	False (for that AUTH attempt)	False
Key 'key'	None	None	"value"	"value"	"value"	"value"

Key Moments - 3 Insights

Why can't the client run SET before AUTH?

Because requirepass is set, Redis blocks all commands except AUTH until the client authenticates (see execution_table step 1 and 3).

What happens if the client sends the wrong password?

Redis rejects the AUTH command and does not allow further commands (see execution_table step 6).

Does the client stay authenticated after a failed AUTH attempt?

No, a failed AUTH does not grant access; the client remains unauthenticated (see variable_tracker 'Authenticated' after step 6).

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the client become authenticated?

A Step 3

B Step 4

C Step 2

D Step 6

💡 Hint

Check the 'Authenticated' variable in variable_tracker after each step.

According to the execution_table, what happens if the client sends GET before AUTH?

A Command executes and returns value

B Command rejected with error

C Client disconnects

D Password is requested again

💡 Hint

Look at step 7 in the execution_table for GET without AUTH.

If requirepass was not set, what would change in the execution flow?

A Server rejects all connections

B Client must still send AUTH

C All commands allowed without AUTH

D Server crashes

💡 Hint

See the decision at 'Is requirepass set?' in concept_flow.

Concept Snapshot

Redis requirepass sets a password for clients.
Clients must send AUTH with the correct password before running commands.
Without AUTH, commands are rejected.
Wrong password causes rejection.
If requirepass is not set, no authentication is needed.

Full Transcript

This visual execution shows how Redis uses requirepass to protect commands. When the server starts with requirepass set, clients must authenticate by sending AUTH with the correct password. Until then, commands like SET or GET are rejected. If the password is correct, commands are allowed. Wrong passwords cause rejection and no access. If requirepass is not set, clients can run commands immediately without AUTH. Variables like 'Authenticated' track client state. This helps beginners see step-by-step how authentication controls access in Redis.

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