Troubleshooting S3 Access Denied for IAM Role: Bucket Policy

• ✓ A.The user has an attached policy or SCP that explicitly denies ec2:RunInstances.
• B.The policy input has a syntax error.
• C.The simulate-custom-policy command does not support ec2:RunInstances.
• D.The resource ARN is incorrect for ec2:RunInstances.

Why A: The most likely reason is that the user has another policy attached (such as an identity-based policy or a service control policy) that explicitly denies ec2:RunInstances. The IAM Policy Simulator evaluates all applicable policies, so even if the provided policy only contains an Allow, an explicit deny from another policy overrides and results in an explicitDeny. Option B (syntax error) is not likely because a syntax error typically causes an error or implicit deny, not an explicit deny. Option C is incorrect because the simulate-custom-policy command does support ec2:RunInstances. Option D is incorrect because an incorrect resource ARN would result in an implicit deny, not an explicit deny.

• A.The user's IAM policy is not attached to the user.
• B.The bucket is in a different AWS region.
• C.The user needs to use MFA.
• ✓ D.The bucket policy explicitly denies the action for that user.

Why D: S3 bucket policies and IAM user policies are evaluated together; if the bucket policy denies access, it overrides the allow.

• A.The bucket policy denies access
• B.The instance profile is not attached to the EC2 instance
• C.The role's policy does not include s3:PutObject
• ✓ D.The policy condition key does not match the request context

Why D: The likely cause is that the policy condition key does not match the request context (Option D). Even though the role allows s3:PutObject, if the policy includes conditions (e.g., source IP, VPC, encryption) that are not met by the request, the effective permission becomes an implicit deny. Since the bucket policy does not explicitly deny, the problem lies in the role policy's conditions. Option A is incorrect because the stem explicitly states the bucket policy does not explicitly deny. Option B is incorrect because if the instance profile were not attached, the role would not be available; but the role is attached as stated. Option C is incorrect because the role policy does include s3:PutObject.

• A.The trust policy does not allow the EC2 service to assume the role.
• B.The policy does not grant s3:GetObject permission.
• ✓ C.The S3 bucket has a bucket policy that denies access.
• D.The role does not have any permissions policy attached.

Why C: Option C is correct because even if the IAM role allows s3:ListBucket on the bucket, an explicit deny in the S3 bucket policy will override any allow, resulting in an AccessDenied error. This is a common scenario where both IAM and bucket policies are evaluated, and a deny in either causes denial of access. Option A is incorrect because the trust policy must allow EC2 for the instance profile to work; if it were wrong, the instance wouldn't be able to assume the role at all. Option B is incorrect because the action required to list objects is s3:ListBucket, not s3:GetObject; the error is for listing, not retrieving. Option D is incorrect because the role has a permissions policy attached (as shown in the exhibit); the issue is the bucket policy denying the request.