ACL-based authorization in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kafka ACL command?

Given the following Kafka ACL command, what will be the result when trying to produce to topic 'orders' as user 'alice'?

Kafka

kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 \
  --add --allow-principal User:alice --operation Write --topic orders

A The command will fail due to missing consumer permission.

B Alice will get a 'Not authorized' error when producing to 'orders'.

C Alice can produce messages to the 'orders' topic successfully.

D The ACL will allow Alice to consume but not produce to 'orders'.

💡 Hint

The command explicitly grants write permission to Alice on the 'orders' topic.

The command adds an ACL that allows user 'alice' to perform the Write operation on the 'orders' topic. This means Alice can produce messages to that topic.

❓ Predict Output

intermediate

What error occurs with this ACL command?

What error will this command produce when executed?

Kafka

kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 \
  --add --allow-principal User:bob --operation Read --topic

A Error: Missing topic name argument.

B Error: Invalid principal format.

C Error: Unknown operation 'Read'.

D No error, ACL added successfully.

💡 Hint

Check if all required arguments are provided.

The command is missing the topic name after --topic, so it will fail with a missing argument error.

🔧 Debug

advanced

Why does this ACL not allow user 'carol' to consume?

User 'carol' cannot consume from topic 'payments' despite this ACL. Identify the issue.

Kafka

kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 \
  --add --allow-principal User:carol --operation Write --topic payments

A The ACL only grants Write permission, not Read, so Carol cannot consume.

B The principal format 'User:carol' is incorrect.

C Zookeeper connection string is invalid.

D The topic name 'payments' is misspelled.

💡 Hint

Check the operation type granted by the ACL.

The ACL grants only Write permission, which allows producing messages. To consume, Read permission is required.

🧠 Conceptual

advanced

What is the effect of this ACL wildcard?

What does this ACL command do?

Kafka

kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 \
  --add --allow-principal User:dave --operation Read --topic '*'

A Allows user 'dave' to read only from a topic literally named '*'.

B Allows user 'dave' to read from all topics.

C Denies user 'dave' from reading any topic.

D Causes a syntax error due to invalid wildcard usage.

💡 Hint

The '*' wildcard matches all topics.

Using '*' as the topic name grants the permission on all topics in the cluster.

❓ Predict Output

expert

How many ACL entries exist after these commands?

After running these commands, how many ACL entries are present for user 'eve'?

Kafka

kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 --add --allow-principal User:eve --operation Read --topic logs
kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 --add --allow-principal User:eve --operation Write --topic logs
kafka-acls --authorizer-properties zookeeper.connect=localhost:2181 --remove --allow-principal User:eve --operation Read --topic logs

A Three ACL entries exist including the removed one.

B Two ACL entries remain: Read and Write permissions on 'logs'.

C No ACL entries remain for user 'eve'.

D One ACL entry remains: Write permission on 'logs' for user 'eve'.

💡 Hint

Removing an ACL deletes only the specified permission.

The Read permission ACL was removed, leaving only the Write permission ACL for user 'eve' on 'logs'.

Practice

1. What is the main purpose of ACL-based authorization in Kafka?

easy

A. To control who can access Kafka topics and perform operations

B. To speed up message processing in Kafka

C. To store messages in a compressed format

D. To monitor Kafka cluster health

Solution

1. Step 1: Understand ACL-based authorization

   ACL-based authorization is used to manage permissions for users or clients in Kafka.

2. Step 2: Identify its main role

   Its main role is to control access to Kafka topics and operations, ensuring security.

3. Final Answer:

   To control who can access Kafka topics and perform operations -> Option A

4. Quick Check:

   ACL controls access = B [OK]

Hint: ACL means controlling access rights in Kafka [OK]

Common Mistakes:

• Confusing ACL with performance tuning
• Thinking ACL compresses data
• Assuming ACL monitors cluster health

2. Which of the following is the correct command to add an ACL for a user named alice to read from topic orders?

easy

A. kafka-acls --add --allow-principal User:alice --operation Read --topic orders

B. kafka-acls --remove --allow-principal User:alice --operation Read --topic orders

C. kafka-acls --add --deny-principal User:alice --operation Write --topic orders

D. kafka-acls --add --allow-principal User:bob --operation Read --topic orders

Solution

1. Step 1: Identify the command to add ACL

   The command to add an ACL uses --add and specifies the principal and operation.

2. Step 2: Match user, operation, and topic

   We want to add read permission for user alice on topic orders, so the command must include these exactly.

3. Final Answer:

   kafka-acls --add --allow-principal User:alice --operation Read --topic orders -> Option A

4. Quick Check:

   Add ACL for alice to read orders = D [OK]

Hint: Add ACL uses --add and --allow-principal [OK]

Common Mistakes:

• Using --remove instead of --add
• Using deny instead of allow
• Specifying wrong user or operation

3. Given the following ACLs:

kafka-acls --add --allow-principal User:bob --operation Write --topic payments
kafka-acls --add --allow-principal User:bob --operation Read --topic payments

What will happen if user bob tries to consume messages from topic payments?

medium

A. Bob can only produce messages but not consume

B. Bob will get a permission denied error when consuming messages

C. Bob can neither produce nor consume messages

D. Bob will be able to consume messages from the payments topic

Solution

1. Step 1: Analyze the ACLs for user bob

   Bob has both Write and Read permissions on the payments topic.

2. Step 2: Understand consuming messages requires Read permission

   Since Bob has Read permission, he can consume messages from the payments topic.

3. Final Answer:

   Bob will be able to consume messages from the payments topic -> Option D

4. Quick Check:

   Read permission allows consume = C [OK]

Hint: Read permission lets user consume messages [OK]

Common Mistakes:

• Assuming Write permission alone allows consuming
• Confusing produce and consume permissions
• Ignoring the Read permission present

4. You run the command:

kafka-acls --add --allow-principal User:carol --operation Read --topic sales

But Carol still cannot read from the sales topic. What is the most likely cause?

medium

A. The ACL was added but the Kafka broker was not restarted

B. Carol needs Write permission to read messages

C. Carol's client is not authenticating as User:carol

D. The ACL was added for the wrong user

Solution

1. Step 1: Check if ACL command syntax is correct

   The command correctly adds Read permission for User:carol on topic sales.

2. Step 2: Consider authentication and identity

   If Carol cannot read despite ACL, likely her client is not authenticating as User:carol, so ACL does not apply.

3. Final Answer:

   Carol's client is not authenticating as User:carol -> Option C

4. Quick Check:

   ACL needs matching user identity = A [OK]

Hint: ACLs depend on correct user authentication [OK]

Common Mistakes:

• Thinking Write permission is needed to read
• Assuming Kafka broker restart is required for ACL changes
• Confusing user names in ACL commands

5. You want to allow a group of users to produce messages to topic logs but deny them from deleting the topic. Which ACL commands correctly achieve this?

hard

A. Add allow ACL for Produce operation only; deny is not needed because deny is default

B. Add allow ACL for Produce operation and add deny ACL for Delete operation for the user group

C. Add allow ACL for Produce and Delete operations for the user group

D. Add deny ACL for Produce and allow ACL for Delete operations for the user group

Solution

1. Step 1: Understand permission requirements

   The users should be allowed to produce messages but denied from deleting the topic.

2. Step 2: Use allow and deny ACLs appropriately

   We add an allow ACL for Produce operation and explicitly add a deny ACL for Delete operation to prevent deletion.

3. Final Answer:

   Add allow ACL for Produce operation and add deny ACL for Delete operation for the user group -> Option B

4. Quick Check:

   Allow produce + deny delete = A [OK]

Hint: Use allow for produce and deny for delete explicitly [OK]

Common Mistakes:

• Assuming deny is default without adding deny ACL
• Allowing delete by mistake
• Mixing up allow and deny commands