Policy evaluation logic in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the effect that allows access in an IAM policy statement.

AWS

{
  "Effect": "[1]",
  "Action": "s3:ListBucket",
  "Resource": "arn:aws:s3:::example_bucket"
}

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

AAllow

BDeny

CPermit

DBlock

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Deny' when you want to allow access

Using unsupported values like 'Permit' or 'Block'

The Effect field in an IAM policy must be either Allow or Deny. To grant access, use Allow.

2fill in blank

medium

Complete the code to specify the action that allows reading objects from an S3 bucket.

AWS

{
  "Effect": "Allow",
  "Action": "[1]",
  "Resource": "arn:aws:s3:::example_bucket/*"
}

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

As3:GetObject

Bs3:PutObject

Cs3:DeleteObject

Ds3:ListBucket

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'PutObject' which is for writing

Using 'ListBucket' which lists bucket contents but not object read

The s3:GetObject action allows reading objects from an S3 bucket.

3fill in blank

hard

Fix the error in the policy statement by completing the missing resource ARN for an S3 bucket.

AWS

{
  "Effect": "Allow",
  "Action": "s3:ListBucket",
  "Resource": "[1]"
}

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

Aarn:aws:s3:::example_bucket/object

Barn:aws:s3:::example_bucket/*

Carn:aws:s3:::example_bucket

Darn:aws:s3:::*

Attempts:

3 left

💡 Hint

Common Mistakes

Using the ARN with '/*' which is for objects, not buckets

Using a wildcard ARN that is too broad

The s3:ListBucket action requires the bucket ARN without the trailing slash or wildcard.

4fill in blank

hard

Fill both blanks to complete the condition that allows access only if the request comes from a specific IP address.

AWS

{
  "Effect": "Allow",
  "Action": "s3:*",
  "Resource": "arn:aws:s3:::example_bucket/*",
  "Condition": {
    "IpAddress": {
      "aws:SourceIp": "[1]"
    },
    "Bool": {
      "aws:SecureTransport": "[2]"
    }
  }
}

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

A203.0.113.0/24

Btrue

Cfalse

D192.168.1.1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single IP instead of a CIDR block when a range is intended

Setting 'aws:SecureTransport' to 'false' which disables HTTPS enforcement

The IpAddress condition restricts access to the specified IP range. The aws:SecureTransport condition set to true requires HTTPS.

5fill in blank

hard

Fill all three blanks to complete the policy statement that denies all actions except listing the bucket and getting objects.

AWS

{
  "Effect": "[1]",
  "NotAction": ["[2]", "[3]"],
  "Resource": "arn:aws:s3:::example_bucket/*"
}

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

ADeny

Bs3:ListBucket

Cs3:GetObject

DAllow

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Allow' instead of 'Deny' for the effect

Listing wrong actions in 'NotAction'

The Effect is set to Deny to block all actions except those listed in NotAction. Here, listing the bucket and getting objects are allowed.

Practice

1. What happens if an AWS IAM policy has both an explicit Allow and an explicit Deny for the same action?

easy

A. The explicit Deny always overrides the Allow.

B. The Allow always overrides the Deny.

C. The action is allowed only if the user is an administrator.

D. The action is denied only if there is a condition attached.

Solution

1. Step 1: Understand explicit Deny effect

   In AWS IAM, an explicit Deny always takes priority over any Allow for the same action.

2. Step 2: Apply policy evaluation logic

   Even if a policy allows an action, if another policy explicitly denies it, the Deny wins and the action is blocked.

3. Final Answer:

   The explicit Deny always overrides the Allow. -> Option A

4. Quick Check:

   Explicit Deny > Allow [OK]

Hint: Remember: Deny always beats Allow in AWS policies [OK]

Common Mistakes:

• Thinking Allow can override Deny
• Ignoring explicit Deny effect
• Assuming conditions affect Deny priority

2. Which of the following is the correct JSON syntax to allow the s3:ListBucket action on a bucket named my-bucket?

easy

A. {\"Effect\": \"Deny\", \"Action\": \"s3:ListBucket\", \"Resource\": \"arn:aws:s3:::my-bucket\"}

B. {\"Effect\": \"Allow\", \"Action\": [\"s3:ListBucket\"], \"Resource\": \"arn:aws:s3:::my-bucket\"}

C. {\"Effect\": \"Allow\", \"Action\": \"s3:ListBucket\", \"Resource\": \"my-bucket\"}

D. {\"Effect\": \"Allow\", \"Action\": \"ListBucket\", \"Resource\": \"arn:aws:s3:::my-bucket\"}

Solution

1. Step 1: Check Action format

   The Action field must be a string or an array of strings. Using an array is valid and recommended for multiple actions.

2. Step 2: Verify Resource ARN format

   The Resource must be the full ARN: arn:aws:s3:::my-bucket for the bucket itself.

3. Final Answer:

   Action as array and correct ARN Resource -> Option B

4. Quick Check:

   Action array + correct ARN = D [OK]

Hint: Use full ARN and array for actions to avoid syntax errors [OK]

Common Mistakes:

• Using bucket name instead of ARN in Resource
• Omitting array brackets for multiple actions
• Using action name without service prefix

3. Given this policy snippet:

{
  "Effect": "Allow",
  "Action": "ec2:StartInstances",
  "Resource": "*",
  "Condition": {
    "IpAddress": {"aws:SourceIp": "203.0.113.0/24"}
  }
}

What happens if a user tries to start an EC2 instance from IP 198.51.100.10?

medium

A. The action is denied because the IP does not match the condition.

B. The action is allowed because the Effect is Allow.

C. The action is allowed only if the user has another policy allowing it.

D. The action is denied only if there is an explicit Deny policy.

Solution

1. Step 1: Understand Condition effect

   The policy allows the action only if the request comes from IPs in 203.0.113.0/24 range.

2. Step 2: Check IP address

   The user's IP 198.51.100.10 is outside the allowed range, so the condition fails.

3. Final Answer:

   The action is denied because the IP does not match the condition. -> Option A

4. Quick Check:

   Condition IP mismatch = Deny [OK]

Hint: Conditions restrict Allow; mismatch means Deny [OK]

Common Mistakes:

• Ignoring condition and assuming Allow always works
• Confusing explicit Deny with condition-based Deny
• Assuming multiple policies needed to allow

4. You have two policies attached to a user:
Policy 1: Allows s3:GetObject on bucket my-bucket.
Policy 2: Denies s3:GetObject on bucket my-bucket if the request is from outside office IP range.

The user tries to get an object from home IP. What is the result?

medium

A. The request is allowed because Policy 1 allows it.

B. The request is allowed only if the user is in the admin group.

C. The request is denied only if there is a service outage.

D. The request is denied because Policy 2 explicitly denies it from outside IPs.

Solution

1. Step 1: Identify explicit Deny with condition

   Policy 2 denies the action if the IP is outside the office range, which applies here.

2. Step 2: Apply evaluation logic

   Explicit Deny overrides any Allow, so the request is denied.

3. Final Answer:

   The request is denied because Policy 2 explicitly denies it from outside IPs. -> Option D

4. Quick Check:

   Explicit Deny with condition blocks request [OK]

Hint: Explicit Deny with condition beats Allow always [OK]

Common Mistakes:

• Ignoring condition in Deny policy
• Assuming Allow always wins
• Thinking user group affects Deny priority

5. You want to create a policy that allows ec2:StopInstances only during business hours (9 AM to 5 PM UTC) and denies it otherwise. Which policy logic correctly enforces this?

hard

A. Only use Deny with condition outside 9-17 UTC, no Allow needed.

B. Allow ec2:StopInstances with condition "DateGreaterThan": {"aws:CurrentTime": "09:00:00Z"}, no Deny needed.

C. Allow ec2:StopInstances unconditionally, and add a Deny with condition outside 9-17 UTC.

D. Allow ec2:StopInstances with condition for 9-17 UTC, and Deny unconditionally.

Solution

1. Step 1: Understand Deny override with time condition

   Unconditional Allow permits ec2:StopInstances, but explicit Deny applies outside 9-17 UTC overriding the Allow.

2. Step 2: Verify business hours enforcement

   During 9 AM-5 PM UTC: Deny condition false -> action allowed. Outside: Deny true -> denied.

3. Final Answer:

   Allow unconditionally, and add a Deny with condition outside 9-17 UTC. -> Option C

4. Quick Check:

   Allow + Deny conditions enforce time limits [OK]

Hint: Unconditional Allow + conditional Deny outside business hours [OK]

Common Mistakes:

• Relying only on Allow conditions without Deny
• Using unconditional Deny that blocks all
• Missing time range in conditions