Access control patterns in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple owner check function in a smart contract.

Blockchain / Solidity

function isOwner(address user) public view returns (bool) {
    return user == [1];
}

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

Amsg.sender

Bowner

Caddress(this)

Dadmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using msg.sender instead of the stored owner variable.

Comparing with address(this) which is the contract address.

The function checks if the given user address matches the stored owner address.

2fill in blank

medium

Complete the code to add a modifier that restricts function access to the owner only.

Blockchain / Solidity

modifier onlyOwner() {
    require([1] == owner, "Not owner");
    _;
}

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Aaddress(this)

Btx.origin

Cmsg.sender

Downer

Attempts:

3 left

💡 Hint

Common Mistakes

Using tx.origin which can be unsafe for access control.

Comparing owner to itself.

The modifier checks that the caller (msg.sender) is the owner before running the function.

3fill in blank

hard

Fix the error in the access control check that uses a mapping for roles.

Blockchain / Solidity

mapping(address => bool) public admins;

function restrictedAction() public {
    require([1][msg.sender], "Not admin");
    // action code
}

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Aadmins

BadminMapping

Cadmin

DadminList

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not exist.

Trying to access a mapping without brackets.

The mapping is named admins, so the require statement must check admins[msg.sender].

4fill in blank

hard

Fill both blanks to create a function that grants admin role only by the owner.

Blockchain / Solidity

function grantAdmin(address user) public [1] {
    admins[user] = true;
    emit AdminGranted(user);
}

modifier [2]() {
    require(msg.sender == owner, "Not owner");
    _;
}

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AonlyOwner

Bpublic

ConlyAdmin

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using public or external without access control.

Using a modifier name that does not exist.

The function uses the onlyOwner modifier to restrict access to the owner only.

5fill in blank

hard

Fill all three blanks to implement a role-based access control check inside a function.

Blockchain / Solidity

function performAction() public {
    require(roles[msg.sender] [1] [2], "Access denied");
    // action code
}

mapping(address => uint) public roles;
uint constant ADMIN_ROLE = [3];

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

A==

B>=

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality instead of greater or equal comparison.

Setting ADMIN_ROLE to 0 which usually means no role.

The function checks if the caller's role is at least ADMIN_ROLE (which is 1) to allow access.