How AWS IoT Greengrass works with IAM

Before you use IAM to manage access to AWS IoT Greengrass, you should understand the IAM features that you can use with AWS IoT Greengrass.

For a high-level view of how other AWS services work with IAM, see AWS services that work with IAM in the IAM User Guide.

Identity-based policies for AWS IoT Greengrass

With IAM identity-based policies, you can specify allowed or denied actions and resources and the conditions under which actions are allowed or denied. AWS IoT Greengrass supports specific actions, resources, and condition keys. To learn about all of the elements that you use in a policy, see IAM JSON policy elements reference in the IAM User Guide.

Actions

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Action element of a JSON policy describes the actions that you can use to allow or deny access in a policy. Policy actions usually have the same name as the associated AWS API operation. There are some exceptions, such as permission-only actions that don't have a matching API operation. There are also some operations that require multiple actions in a policy. These additional actions are called dependent actions.

Include actions in a policy to grant permissions to perform the associated operation.

Policy actions for AWS IoT Greengrass use the greengrass: prefix before the action. For example, to allow someone to use the ListCoreDevices API operation to list the core devices in their AWS account, you include the greengrass:ListCoreDevices action in their policy. Policy statements must include either an Action or NotAction element. AWS IoT Greengrass defines its own set of actions that describe tasks that you can perform with this service.

To specify multiple actions in a single statement, list them between brackets ([ ]) and separate them with commas, as follows:

"Action": [
  "greengrass:action1",
  "greengrass:action2",
  "greengrass:action3"
]

You can use wildcards (*) to specify multiple actions. For example, to specify all actions that begin with the word List, include the following action:

"Action": "greengrass:List*"

For the complete list of AWS IoT Greengrass actions, see Actions Defined by AWS IoT Greengrass in the IAM User Guide.

Resources

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Resource JSON policy element specifies the object or objects to which the action applies. Statements must include either a Resource or a NotResource element. As a best practice, specify a resource using its Amazon Resource Name (ARN). You can do this for actions that support a specific resource type, known as resource-level permissions.

For actions that don't support resource-level permissions, such as listing operations, use a wildcard (*) to indicate that the statement applies to all resources.

"Resource": "*"

The following table contains the AWS IoT Greengrass resource ARNs that can be used in the Resource element of a policy statement. For a mapping of supported resource-level permissions for AWS IoT Greengrass actions, see Actions Defined by AWS IoT Greengrass in the IAM User Guide.

Some AWS IoT Greengrass actions (for example, some list operations), cannot be performed on a specific resource. In those cases, you must use the wildcard alone.

"Resource": "*"

To specify multiple resource ARNs in a statement, list them between brackets ([ ]) and separate them with commas, as follows:

"Resource": [
  "resource-arn1",
  "resource-arn2",
  "resource-arn3"
]

For more information about ARN formats, see Amazon Resource Names (ARNs) and AWS service namespaces in the Amazon Web Services General Reference.

Condition keys

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Condition element (or Condition block) lets you specify conditions in which a statement is in effect. The Condition element is optional. You can create conditional expressions that use condition operators, such as equals or less than, to match the condition in the policy with values in the request.

If you specify multiple Condition elements in a statement, or multiple keys in a single Condition element, AWS evaluates them using a logical AND operation. If you specify multiple values for a single condition key, AWS evaluates the condition using a logical OR operation. All of the conditions must be met before the statement's permissions are granted.

You can also use placeholder variables when you specify conditions. For example, you can grant an IAM user permission to access a resource only if it is tagged with their IAM user name. For more information, see IAM policy elements: variables and tags in the IAM User Guide.

AWS supports global condition keys and service-specific condition keys. To see all AWS global condition keys, see AWS global condition context keys in the IAM User Guide.

Examples

To view examples of AWS IoT Greengrass identity-based policies, see Identity-based policy examples for AWS IoT Greengrass.

Resource-based policies for AWS IoT Greengrass

AWS IoT Greengrass does not support resource-based policies.

Access control lists (ACLs)

AWS IoT Greengrass does not support ACLs.

Authorization based on AWS IoT Greengrass tags

You can attach tags to supported AWS IoT Greengrass resources or pass tags in a request to AWS IoT Greengrass. To control access based on tags, you provide tag information in the Condition element of a policy using the aws:ResourceTag/${TagKey}, aws:RequestTag/${TagKey}, or aws:TagKeys condition keys. For more information, see Tag your AWS IoT Greengrass Version 2 resources.

IAM roles for AWS IoT Greengrass

An IAM role is an entity within your AWS account that has specific permissions.

Using temporary credentials with AWS IoT Greengrass

Temporary credentials are used to sign in with federation, assume an IAM role, or to assume a cross-account role. You obtain temporary security credentials by calling AWS STS API operations such as AssumeRole or GetFederationToken.

On the Greengrass core, temporary credentials for the device role are made available to Greengrass components. If your components use the AWS SDK, you don't need to add logic to obtain the credentials because the AWS SDK does this for you.

Service-linked roles

AWS IoT Greengrass does not support service-linked roles.

Service roles

This feature allows a service to assume a service role on your behalf. This role allows the service to access resources in other services to complete an action on your behalf. Service roles appear in your IAM account and are owned by the account. This means that an IAM administrator can change the permissions for this role. However, doing so might break the functionality of the service.

AWS IoT Greengrass core devices use a service role to allow Greengrass components and Lambda functions to access some of your AWS resources on your behalf. For more information, see Authorize core devices to interact with AWS services.

AWS IoT Greengrass uses a service role to access some of your AWS resources on your behalf. For more information, see Greengrass service role.