Task Role — Bedrock Access

Overview

The Task Role Task Role
An IAM role assumed by ecs-tasks.amazonaws.com that grants the running container application-level permissions (Bedrock access in this project). is an IAM role assumed by the running container at runtime. Unlike the Task Execution Role (which handles image pulls and log writes), the Task Role grants your application the permissions it needs to interact with AWS services. In this project, the container calls Amazon Bedrock Bedrock
AWS fully managed service providing foundation models for generative AI applications. to run inference on foundation models, so the Task Role includes a policy that allows bedrock:InvokeModel on the required resource ARNs.

Trust Policy

The Task Role Task Role
An IAM role assumed by ecs-tasks.amazonaws.com that grants the running container application-level permissions (Bedrock access in this project). uses the same trust relationship as the Task Execution Role — it trusts ecs-tasks.amazonaws.com with an aws:SourceAccount condition to prevent cross-account confused deputy attacks.

main.tf

resource "aws_iam_role" "task" {
  name = "${var.name}-task"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect = "Allow"
        Principal = {
          Service = "ecs-tasks.amazonaws.com"
        }
        Action = "sts:AssumeRole"
        Condition = {
          StringEquals = {
            "aws:SourceAccount" = data.aws_caller_identity.current.account_id
          }
        }
      }
    ]
  })
}

Bedrock IAM Policy

The inline policy grants bedrock:InvokeModel permission on Bedrock Bedrock
AWS fully managed service providing foundation models for generative AI applications. resources with two distinct ARN patterns:

main.tf

resource "aws_iam_role_policy" "task_bedrock" {
  name = "${var.name}-bedrock"
  role = aws_iam_role.task.id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect = "Allow"
        Action = [
          "bedrock:InvokeModel"
        ]
        Resource = [
          "arn:aws:bedrock:*::foundation-model/*",
          "arn:aws:bedrock:*:*:inference-profile/*"
        ]
      }
    ]
  })
}

Why Both ARN Patterns Are Required

Foundation models Foundation Model
A pre-trained large language or multimodal model available through Amazon Bedrock. and inference profiles Inference Profile
A Bedrock configuration that specifies model parameters and routing for inference requests. use different ARN formats in Bedrock Bedrock
AWS fully managed service providing foundation models for generative AI applications. because they represent different resource types with different ownership models.

Resource	ARN Pattern	Account Field	Reason
Foundation Model	arn:aws:bedrock:::foundation-model/	Empty (no account)	Foundation models are AWS-managed global resources not owned by any customer account
Inference Profile	arn:aws:bedrock:::inference-profile/*	Wildcard (any account)	Inference profiles can be account-specific or cross-region, requiring the account field

Note

The foundation model ARN has an empty account field (double colon ::) because these models are owned by AWS, not by your account. Inference profiles include an account field because they can be configured per-account for cross-region routing and model parameter customization.

If you only include the foundation model ARN, direct InvokeModel calls using a model ID work, but requests routed through an inference profile fail with an AccessDeniedException. Including both ARN patterns ensures the application can invoke models regardless of whether the request targets a model directly or goes through an inference profile.

Tip

When the Bedrock SDK resolves a model identifier, it may route through a cross-region inference profile transparently. Always include both ARN patterns to avoid unexpected access errors in production.

Role Attachment to the Express Gateway Service

The Task Role Task Role
An IAM role assumed by ecs-tasks.amazonaws.com that grants the running container application-level permissions (Bedrock access in this project). ARN is passed to the Express Gateway Service resource via the primary_container block, making it available to the running container as instance credentials:

main.tf

resource "aws_ecs_express_gateway_service" "this" {
  # ...

  primary_container {
    # ...
    task_role_arn = aws_iam_role.task.arn
  }
}