IAM for Bedrock: The Guard at the Door

In AWS, nothing happens without permission. Before your Python code can call invoke_model, your Identity (User or Role) must be granted the specific right to do so. This is handled by IAM (Identity and Access Management).

1. The Core Permission: bedrock:InvokeModel

This is the most critical permission. Without it, you cannot get a single word out of an LLM.

Example JSON Policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "bedrock:InvokeModel",
                "bedrock:InvokeModelWithResponseStream"
            ],
            "Resource": [
                "arn:aws:bedrock:us-east-1::foundation-model/anthropic.claude-3-sonnet-20240229-v1:0"
            ]
        }
    ]
}

2. Bedrock Read-Only vs. Full Access

• AmazonBedrockFullAccess: (Managed Policy) Allows creating Knowledge Bases, Provisioning throughput, and calling models. (Use for Developers).
• AmazonBedrockReadOnly: Allows viewing models and settings but cannot invoke them. (Use for Auditors).

---

3. Best Practice: Least Privilege

You should specify exactly which models a service can call. Don't use Resource: "*".

• If your app only needs Llama 3 for translation, only give it permission for the Llama 3 ARN.

---

4. Visualizing IAM Logic

graph LR
    App[Your Python Script] --> Role[IAM Role]
    Role --> Policy[Policy: Allow InvokeModel]
    Policy --> Model[Claude 3]
    Model --> Success[AI Response]

---

💡 Guidance for Learners

If you get an error saying AccessDeniedException, it usually means one of two things:

1. Your IAM User/Role doesn't have the bedrock:InvokeModel permission.
2. You haven't Requested Access to that model in the AWS Console (we cover this in the next lesson).

---

Summary

• IAM Policies govern who can call which model.
• bedrock:InvokeModel is the primary action for AI applications.
• Use Model ARNs to restrict access to specific foundation models.
• Always follow the principle of Least Privilege.