# Identity and access management for Amazon Verified Permissions
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Amazon Identity and Access Management (IAM) is an Amazon Web Services service that helps an administrator securely control access to Amazon resources. IAM administrators control who can be *authenticated* (signed in) and *authorized* (have permissions) to use Verified Permissions resources. IAM is an Amazon Web Services service that you can use with no additional charge.

**Topics**
+ [Audience](#security_iam_audience)
+ [Authenticating with identities](#security_iam_authentication)
+ [Managing access using policies](#security_iam_access-manage)
+ [How Amazon Verified Permissions works with IAM](security_iam_service-with-iam.md)
+ [IAM policies for Verified Permissions](security-iam-getting-started-policies.md)
+ [Identity-based policy examples for Amazon Verified Permissions](security_iam_id-based-policy-examples.md)
+ [Amazon managed policies for Amazon Verified Permissions](security-iam-awsmanpol.md)
+ [Troubleshooting Amazon Verified Permissions identity and access](security_iam_troubleshoot.md)

## Audience
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How you use Amazon Identity and Access Management (IAM) differs based on your role:
+ **Service user** - request permissions from your administrator if you cannot access features (see [Troubleshooting Amazon Verified Permissions identity and access](security_iam_troubleshoot.md))
+ **Service administrator** - determine user access and submit permission requests (see [How Amazon Verified Permissions works with IAM](security_iam_service-with-iam.md))
+ **IAM administrator** - write policies to manage access (see [Identity-based policy examples for Amazon Verified Permissions](security_iam_id-based-policy-examples.md))

## Authenticating with identities
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Authentication is how you sign in to Amazon using your identity credentials. You must be authenticated as the Amazon Web Services account root user, an IAM user, or by assuming an IAM role.

For programmatic access, Amazon provides an SDK and CLI to cryptographically sign requests. For more information, see [Amazon Signature Version 4 for API requests](https://docs.amazonaws.cn/IAM/latest/UserGuide/reference_sigv.html) in the *IAM User Guide*.

### Amazon Web Services account root user
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 When you create an Amazon Web Services account, you begin with one sign-in identity called the Amazon Web Services account *root user* that has complete access to all Amazon Web Services services and resources. We strongly recommend that you don't use the root user for everyday tasks. For tasks that require root user credentials, see [Tasks that require root user credentials](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_root-user.html#root-user-tasks) in the *IAM User Guide*. 

### Federated identity
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As a best practice, require human users to use federation with an identity provider to access Amazon Web Services services using temporary credentials.

A *federated identity* is a user from your enterprise directory, web identity provider, or Amazon Directory Service that accesses Amazon Web Services services using credentials from an identity source. Federated identities assume roles that provide temporary credentials.

### IAM users and groups
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An *[IAM user](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_users.html)* is an identity with specific permissions for a single person or application. We recommend using temporary credentials instead of IAM users with long-term credentials. For more information, see [Require human users to use federation with an identity provider to access Amazon using temporary credentials](https://docs.amazonaws.cn/IAM/latest/UserGuide/best-practices.html#bp-users-federation-idp) in the *IAM User Guide*.

An [https://docs.amazonaws.cn/IAM/latest/UserGuide/id_groups.html](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_groups.html) specifies a collection of IAM users and makes permissions easier to manage for large sets of users. For more information, see [Use cases for IAM users](https://docs.amazonaws.cn/IAM/latest/UserGuide/gs-identities-iam-users.html) in the *IAM User Guide*.

### IAM roles
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An *[IAM role](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles.html)* is an identity within your Amazon Web Services account that has specific permissions. It is similar to an IAM user, but is not associated with a specific person. You can temporarily assume an IAM role in the Amazon Web Services Management Console by [switching roles](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles_use_switch-role-console.html). You can assume a role by calling an Amazon CLI or Amazon API operation or by using a custom URL. For more information about methods for using roles, see [Using IAM roles](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles_use.html) in the *IAM User Guide*.

IAM roles with temporary credentials are useful in the following situations:
+ **Federated user access** – To assign permissions to a federated identity, you create a role and define permissions for the role. When a federated identity authenticates, the identity is associated with the role and is granted the permissions that are defined by the role. For information about roles for federation, see [ Create a role for a third-party identity provider (federation)](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles_create_for-idp.html) in the *IAM User Guide*. 
+ **Temporary IAM user permissions** – An IAM user or role can assume an IAM role to temporarily take on different permissions for a specific task.
+ **Cross-account access** – You can use an IAM role to allow someone (a trusted principal) in a different account to access resources in your account. Roles are the primary way to grant cross-account access. However, with some Amazon Web Services services, you can attach a policy directly to a resource (instead of using a role as a proxy). To learn the difference between roles and resource-based policies for cross-account access, see [How IAM roles differ from resource-based policies](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles_compare-resource-policies.html) in the *IAM User Guide*.
+ **Applications running on Amazon EC2** – You can use an IAM role to manage temporary credentials for applications that are running on an EC2 instance and making Amazon CLI or Amazon API requests. This is preferable to storing access keys within the EC2 instance. To assign an Amazon role to an EC2 instance and make it available to all of its applications, you create an instance profile that is attached to the instance. An instance profile contains the role and enables programs that are running on the EC2 instance to get temporary credentials. For more information, see [Use an IAM role to grant permissions to applications running on Amazon EC2 instances](https://docs.amazonaws.cn/IAM/latest/UserGuide/id_roles_use_switch-role-ec2.html) in the *IAM User Guide*. 

To learn whether to use IAM roles or IAM users, see [When to create an IAM role (instead of a user)](https://docs.amazonaws.cn/IAM/latest/UserGuide/id.html#id_which-to-choose_role) in the *IAM User Guide*.

## Managing access using policies
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You control access in Amazon by creating policies and attaching them to Amazon identities or resources. A policy defines permissions when associated with an identity or resource. Amazon evaluates these policies when a principal makes a request. Most policies are stored in Amazon as JSON documents. For more information about JSON policy documents, see [Overview of JSON policies](https://docs.amazonaws.cn/IAM/latest/UserGuide/access_policies.html#access_policies-json) in the *IAM User Guide*.

Using policies, administrators specify who has access to what by defining which **principal** can perform **actions** on what **resources**, and under what **conditions**.

By default, users and roles have no permissions. An IAM administrator creates IAM policies and adds them to roles, which users can then assume. IAM policies define permissions regardless of the method used to perform the operation.

### Identity-based policies
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Identity-based policies are JSON permissions policy documents that you attach to an identity (user, group, or role). These policies control what actions identities can perform, on which resources, and under what conditions. To learn how to create an identity-based policy, see [Define custom IAM permissions with customer managed policies](https://docs.amazonaws.cn/IAM/latest/UserGuide/access_policies_create.html) in the *IAM User Guide*.

Identity-based policies can be *inline policies* (embedded directly into a single identity) or *managed policies* (standalone policies attached to multiple identities). To learn how to choose between managed and inline policies, see [Choose between managed policies and inline policies](https://docs.amazonaws.cn/IAM/latest/UserGuide/access_policies-choosing-managed-or-inline.html) in the *IAM User Guide*.

### Resource-based policies
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Resource-based policies are JSON policy documents that you attach to a resource. Examples include IAM *role trust policies* and Amazon S3 *bucket policies*. In services that support resource-based policies, service administrators can use them to control access to a specific resource. You must [specify a principal](https://docs.amazonaws.cn/IAM/latest/UserGuide/reference_policies_elements_principal.html) in a resource-based policy.

Resource-based policies are inline policies that are located in that service. You can't use Amazon managed policies from IAM in a resource-based policy.

### Access control lists (ACLs)
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Access control lists (ACLs) control which principals (account members, users, or roles) have permissions to access a resource. ACLs are similar to resource-based policies, although they do not use the JSON policy document format.

Amazon S3, Amazon WAF, and Amazon VPC are examples of services that support ACLs. To learn more about ACLs, see [Access control list (ACL) overview](https://docs.amazonaws.cn/AmazonS3/latest/userguide/acl-overview.html) in the *Amazon Simple Storage Service Developer Guide*.

### Other policy types
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Amazon supports additional policy types that can set the maximum permissions granted by more common policy types:
+ **Permissions boundaries** – Set the maximum permissions that an identity-based policy can grant to an IAM entity. For more information, see [Permissions boundaries for IAM entities](https://docs.amazonaws.cn/IAM/latest/UserGuide/access_policies_boundaries.html) in the *IAM User Guide*.
+ **Service control policies (SCPs)** – Specify the maximum permissions for an organization or organizational unit in Amazon Organizations. For more information, see [Service control policies](https://docs.amazonaws.cn/organizations/latest/userguide/orgs_manage_policies_scps.html) in the *Amazon Organizations User Guide*.
+ **Resource control policies (RCPs)** – Set the maximum available permissions for resources in your accounts. For more information, see [Resource control policies (RCPs)](https://docs.amazonaws.cn/organizations/latest/userguide/orgs_manage_policies_rcps.html) in the *Amazon Organizations User Guide*.
+ **Session policies** – Advanced policies passed as a parameter when creating a temporary session for a role or federated user. For more information, see [Session policies](https://docs.amazonaws.cn/IAM/latest/UserGuide/access_policies.html#policies_session) in the *IAM User Guide*.

### Multiple policy types
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When multiple types of policies apply to a request, the resulting permissions are more complicated to understand. To learn how Amazon determines whether to allow a request when multiple policy types are involved, see [Policy evaluation logic](https://docs.amazonaws.cn/IAM/latest/UserGuide/reference_policies_evaluation-logic.html) in the *IAM User Guide*.