IAM roles concept in AWS - Step-by-Step Execution

Process Flow - IAM roles concept

User or Service Requests Access

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Assume IAM Role

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Temporary Credentials Issued

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Access AWS Resources with Permissions

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Access Complete

This flow shows how a user or service requests access by assuming an IAM role, receives temporary credentials, and then accesses AWS resources with the permissions granted by that role.

Execution Sample

AWS

1. User calls AssumeRole API
2. AWS returns temporary credentials
3. User uses credentials to access S3 bucket
4. Access allowed or denied based on role permissions

This example shows how a user assumes an IAM role to get temporary credentials and then accesses an AWS S3 bucket using those credentials.

Process Table

Step	Action	Input	Output	Result
1	User requests to assume role	Role ARN	Temporary credentials request	Request sent to AWS STS
2	AWS STS validates request	Role ARN, User identity	Temporary credentials (AccessKeyId, SecretAccessKey, SessionToken)	Credentials issued with limited duration
3	User uses temporary credentials	Temporary credentials	API call to S3 bucket	Request authenticated with role permissions
4	S3 evaluates permissions	Role permissions, bucket policy	Allow or Deny	Access granted or denied
5	User completes operation	N/A	N/A	Access complete or error returned

💡 Process ends after user completes access or is denied based on role permissions

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
User Identity	User credentials	Request to assume role	Validated by STS	Uses temporary credentials	Access granted or denied
Temporary Credentials	None	Requested	Issued by STS	Used for API calls	Expired after duration

Key Moments - 3 Insights

Why does the user need to assume a role instead of using their own credentials?

Because the role provides temporary credentials with specific permissions, limiting access scope and duration, as shown in execution_table step 2 and 3.

What happens if the role permissions do not allow access to the resource?

The access is denied at step 4 when S3 evaluates permissions, resulting in an error returned to the user.

Are the temporary credentials permanent?

No, they are temporary and expire after a set duration, as tracked in variable_tracker under Temporary Credentials.

Visual Quiz - 3 Questions

Look at the execution_table, what is issued by AWS STS at step 2?

A Temporary credentials with limited duration

B Permanent user credentials

C Access denied message

D Role ARN

💡 Hint

Check the Output column in execution_table row 2

At which step does the S3 bucket decide to allow or deny access?

A Step 1

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the Action and Result columns in execution_table row 4

If the temporary credentials expire, what happens to the user's access?

A Access continues without interruption

B User must request new temporary credentials

C User can use original credentials instead

D Access is permanently revoked

💡 Hint

See variable_tracker row for Temporary Credentials and their expiration

Concept Snapshot

IAM Roles let users or services get temporary credentials.
They assume a role to get these credentials.
Temporary credentials have limited permissions and duration.
Use these credentials to access AWS resources securely.
Access is controlled by the role's permissions and resource policies.

Full Transcript

IAM roles allow users or services to request temporary access to AWS resources. The process starts when a user or service requests to assume a role by providing the role's ARN. AWS Security Token Service (STS) validates this request and issues temporary credentials with limited permissions and a set expiration time. The user then uses these temporary credentials to make API calls to AWS services like S3. The service evaluates the permissions associated with the role and the resource policies to allow or deny access. This approach enhances security by limiting access scope and duration. Temporary credentials expire after their duration, requiring the user to assume the role again to continue access.