Capability-based security in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define capability-based security.

Operating Systems

In capability-based security, a [1] is a communicable, unforgeable token of authority.

Drag options to blanks, or click blank then click option'

Acapability

Bpassword

Cfirewall

Dencryption

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing capabilities with passwords or encryption.

A capability is a token that grants access rights to an object or resource in capability-based security.

2fill in blank

medium

Complete the sentence to explain how capabilities are used.

Operating Systems

A process must present a valid [1] to access a resource in capability-based security.

Drag options to blanks, or click blank then click option'

Atoken

Bcertificate

Cusername

Dcapability

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing general terms like 'token' or 'certificate' instead of the specific term.

In capability-based security, a process uses a capability as proof of its right to access a resource.

3fill in blank

hard

Fix the error in the statement about capability-based security.

Operating Systems

[1] are used to restrict access by identity rather than by possession of tokens.

Drag options to blanks, or click blank then click option'

Aaccess control lists

Bpasswords

Ccapabilities

Dencryption keys

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing capabilities with ACLs or passwords.

Access control lists (ACLs) restrict access by identity, while capability-based security restricts access by possession of capabilities (tokens).

4fill in blank

hard

Fill both blanks to complete the dictionary comprehension that filters capabilities with read access.

Operating Systems

read_caps = {obj: cap for obj, cap in caps.items() if cap [1] 'read' and cap [2] 'write'}

Drag options to blanks, or click blank then click option'

A==

B!=

Cand

Dor

Attempts:

3 left

💡 Hint

Common Mistakes

Using logical operators incorrectly or mixing equality and inequality.

The code selects capabilities equal to 'read' and not equal to 'write'.

5fill in blank

hard

Fill all three blanks to create a dictionary of capabilities with 'execute' permission and object names in uppercase.

Operating Systems

exec_caps = [1]: cap for obj, cap in caps.items() if cap [2] 'execute' and obj.[3]()

Drag options to blanks, or click blank then click option'

Aobj.upper()

B==

Cupper

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing method names or using wrong comparison operators.

The dictionary uses the uppercase object name as key, checks if capability equals 'execute', and calls upper() method on the object name.

Practice

1. What is the main idea behind capability-based security?

easy

A. Access is controlled only by usernames and passwords

B. Permissions are granted randomly to users

C. Security is based on firewall rules only

D. Users or programs get tokens that directly grant permissions

Solution

1. Step 1: Understand capability-based security concept

   It means giving users or programs special tokens that say what they can do.

2. Step 2: Compare with other methods

   Unlike passwords or firewalls, capability tokens directly grant permission.

3. Final Answer:

   Users or programs get tokens that directly grant permissions -> Option D

4. Quick Check:

   Capability tokens = direct permission [OK]

Hint: Focus on tokens that grant direct access [OK]

Common Mistakes:

• Confusing capability tokens with passwords
• Thinking security is only about firewalls
• Believing permissions are random

2. Which of the following is a correct way to describe a capability in capability-based security?

easy

A. A token that grants specific access rights

B. A password string stored in a file

C. A firewall rule blocking IP addresses

D. A username used for login

Solution

1. Step 1: Define what a capability is

   A capability is a token that grants specific access rights to a resource.

2. Step 2: Eliminate incorrect options

   Passwords, firewall rules, and usernames are not capabilities.

3. Final Answer:

   A token that grants specific access rights -> Option A

4. Quick Check:

   Capability = access token [OK]

Hint: Remember capability means access token, not password [OK]

Common Mistakes:

• Mixing capabilities with passwords
• Thinking firewall rules are capabilities
• Confusing usernames with capabilities

3. Consider a system where a program holds a capability token allowing it to read a file. What happens if the program tries to write to the file?

medium

A. The write operation fails because the capability only allows reading

B. The write operation succeeds because the program has access

C. The system asks the user for permission

D. The file is deleted automatically

Solution

1. Step 1: Understand capability permissions

   Capabilities specify exact rights, here only read permission is given.

2. Step 2: Predict system behavior on unauthorized action

   Trying to write without write permission causes failure.

3. Final Answer:

   The write operation fails because the capability only allows reading -> Option A

4. Quick Check:

   Capability limits action to allowed rights [OK]

Hint: Check if capability includes the requested permission [OK]

Common Mistakes:

• Assuming any access means all actions allowed
• Thinking system prompts user for permission
• Believing unauthorized actions delete files

4. A program tries to use a capability token but gets an error. Which of these is the most likely cause?

medium

A. The user forgot their password

B. The capability token was revoked or expired

C. The system has no internet connection

D. The program has too many tokens

Solution

1. Step 1: Identify common reasons for capability errors

   Revoked or expired tokens cause access errors.

2. Step 2: Eliminate unrelated causes

   Too many tokens, internet issues, or user passwords do not affect capability token validity.

3. Final Answer:

   The capability token was revoked or expired -> Option B

4. Quick Check:

   Revoked/expired token = error cause [OK]

Hint: Check if token is still valid before use [OK]

Common Mistakes:

• Blaming network issues for capability errors
• Thinking password affects capability tokens
• Assuming token count causes errors

5. In a capability-based system, how can you safely share access to a resource with another program without giving full control?

hard

A. Allow the other program to run as administrator

B. Share your password with the other program

C. Give the other program a capability token with limited permissions

D. Disable all security checks temporarily

Solution

1. Step 1: Understand safe sharing in capability systems

   Sharing limited permission tokens lets others access only what you allow.

2. Step 2: Avoid unsafe methods

   Sharing passwords, admin rights, or disabling security risks full control and breaches.

3. Final Answer:

   Give the other program a capability token with limited permissions -> Option C

4. Quick Check:

   Limited capability token = safe sharing [OK]

Hint: Share only limited tokens, never passwords or full rights [OK]

Common Mistakes:

• Sharing passwords instead of tokens
• Granting full admin rights unnecessarily
• Turning off security checks