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Package software.amazon.awscdk.services.iam

AWS Identity and Access Management Construct Library

See: Description

Package software.amazon.awscdk.services.iam Description

AWS Identity and Access Management Construct Library

---

cfn-resources: Stable

cdk-constructs: Stable


Define a role and add permissions to it. This will automatically create and attach an IAM policy to the role:

 Role role = Role.Builder.create(this, "MyRole")
         .assumedBy(new ServicePrincipal("sns.amazonaws.com"))
         .build();
 
 role.addToPolicy(PolicyStatement.Builder.create()
         .resources(List.of("*"))
         .actions(List.of("lambda:InvokeFunction"))
         .build());
 

Define a policy and attach it to groups, users and roles. Note that it is possible to attach the policy either by calling xxx.attachInlinePolicy(policy) or policy.attachToXxx(xxx).

 User user = User.Builder.create(this, "MyUser").password(SecretValue.plainText("1234")).build();
 Group group = new Group(this, "MyGroup");
 
 Policy policy = new Policy(this, "MyPolicy");
 policy.attachToUser(user);
 group.attachInlinePolicy(policy);
 

Managed policies can be attached using xxx.addManagedPolicy(ManagedPolicy.fromAwsManagedPolicyName(policyName)):

 Group group = new Group(this, "MyGroup");
 group.addManagedPolicy(ManagedPolicy.fromAwsManagedPolicyName("AdministratorAccess"));
 

Granting permissions to resources

Many of the AWS CDK resources have grant* methods that allow you to grant other resources access to that resource. As an example, the following code gives a Lambda function write permissions (Put, Update, Delete) to a DynamoDB table.

 Function fn;
 Table table;
 
 
 table.grantWriteData(fn);
 

The more generic grant method allows you to give specific permissions to a resource:

 Function fn;
 Table table;
 
 
 table.grant(fn, "dynamodb:PutItem");
 

The grant* methods accept an IGrantable object. This interface is implemented by IAM principlal resources (groups, users and roles) and resources that assume a role such as a Lambda function, EC2 instance or a Codebuild project.

You can find which grant* methods exist for a resource in the AWS CDK API Reference.

Roles

Many AWS resources require Roles to operate. These Roles define the AWS API calls an instance or other AWS service is allowed to make.

Creating Roles and populating them with the right permissions Statements is a necessary but tedious part of setting up AWS infrastructure. In order to help you focus on your business logic, CDK will take care of creating roles and populating them with least-privilege permissions automatically.

All constructs that require Roles will create one for you if don't specify one at construction time. Permissions will be added to that role automatically if you associate the construct with other constructs from the AWS Construct Library (for example, if you tell an AWS CodePipeline to trigger an AWS Lambda Function, the Pipeline's Role will automatically get lambda:InvokeFunction permissions on that particular Lambda Function), or if you explicitly grant permissions using grant functions (see the previous section).

Opting out of automatic permissions management

You may prefer to manage a Role's permissions yourself instead of having the CDK automatically manage them for you. This may happen in one of the following cases:

To prevent constructs from updating your Role's policy, pass the object returned by myRole.withoutPolicyUpdates() instead of myRole itself.

For example, to have an AWS CodePipeline not automatically add the required permissions to trigger the expected targets, do the following:

 Role role = Role.Builder.create(this, "Role")
         .assumedBy(new ServicePrincipal("codepipeline.amazonaws.com"))
         // custom description if desired
         .description("This is a custom role...")
         .build();
 
 Pipeline.Builder.create(this, "Pipeline")
         // Give the Pipeline an immutable view of the Role
         .role(role.withoutPolicyUpdates())
         .build();
 
 // You now have to manage the Role policies yourself
 role.addToPolicy(PolicyStatement.Builder.create()
         .actions(List.of())
         .resources(List.of())
         .build());
 

Using existing roles

If there are Roles in your account that have already been created which you would like to use in your CDK application, you can use Role.fromRoleArn to import them, as follows:

 IRole role = Role.fromRoleArn(this, "Role", "arn:aws:iam::123456789012:role/MyExistingRole", FromRoleArnOptions.builder()
         // Set 'mutable' to 'false' to use the role as-is and prevent adding new
         // policies to it. The default is 'true', which means the role may be
         // modified as part of the deployment.
         .mutable(false)
         .build());
 

Configuring an ExternalId

If you need to create Roles that will be assumed by third parties, it is generally a good idea to require an ExternalId to assume them. Configuring an ExternalId works like this:

 Role role = Role.Builder.create(this, "MyRole")
         .assumedBy(new AccountPrincipal("123456789012"))
         .externalIds(List.of("SUPPLY-ME"))
         .build();
 

Principals vs Identities

When we say Principal, we mean an entity you grant permissions to. This entity can be an AWS Service, a Role, or something more abstract such as "all users in this account" or even "all users in this organization". An Identity is an IAM representing a single IAM entity that can have a policy attached, one of Role, User, or Group.

IAM Principals

When defining policy statements as part of an AssumeRole policy or as part of a resource policy, statements would usually refer to a specific IAM principal under Principal.

IAM principals are modeled as classes that derive from the iam.PolicyPrincipal abstract class. Principal objects include principal type (string) and value (array of string), optional set of conditions and the action that this principal requires when it is used in an assume role policy document.

To add a principal to a policy statement you can either use the abstract statement.addPrincipal, one of the concrete addXxxPrincipal methods:

If multiple principals are added to the policy statement, they will be merged together:

 PolicyStatement statement = new PolicyStatement();
 statement.addServicePrincipal("cloudwatch.amazonaws.com");
 statement.addServicePrincipal("ec2.amazonaws.com");
 statement.addArnPrincipal("arn:aws:boom:boom");
 

Will result in:

 {
   "Principal": {
     "Service": [ "cloudwatch.amazonaws.com", "ec2.amazonaws.com" ],
     "AWS": "arn:aws:boom:boom"
   }
 }
 

The CompositePrincipal class can also be used to define complex principals, for example:

 Role role = Role.Builder.create(this, "MyRole")
         .assumedBy(new CompositePrincipal(
         new ServicePrincipal("ec2.amazonaws.com"),
         new AccountPrincipal("1818188181818187272")))
         .build();
 

The PrincipalWithConditions class can be used to add conditions to a principal, especially those that don't take a conditions parameter in their constructor. The principal.withConditions() method can be used to create a PrincipalWithConditions from an existing principal, for example:

 IPrincipal principal = new AccountPrincipal("123456789000").withConditions(Map.of("StringEquals", Map.of("foo", "baz")));
 

NOTE: If you need to define an IAM condition that uses a token (such as a deploy-time attribute of another resource) in a JSON map key, use CfnJson to render this condition. See this test for an example.

The WebIdentityPrincipal class can be used as a principal for web identities like Cognito, Amazon, Google or Facebook, for example:

 IPrincipal principal = new WebIdentityPrincipal("cognito-identity.amazonaws.com").withConditions(Map.of(
         "StringEquals", Map.of("cognito-identity.amazonaws.com:aud", "us-east-2:12345678-abcd-abcd-abcd-123456"),
         "ForAnyValue:StringLike", Map.of("cognito-identity.amazonaws.com:amr", "unauthenticated")));
 

Parsing JSON Policy Documents

The PolicyDocument.fromJson and PolicyStatement.fromJson static methods can be used to parse JSON objects. For example:

 Map<String, Object> policyDocument = Map.of(
         "Version", "2012-10-17",
         "Statement", List.of(Map.of(
                 "Sid", "FirstStatement",
                 "Effect", "Allow",
                 "Action", List.of("iam:ChangePassword"),
                 "Resource", "*"), Map.of(
                 "Sid", "SecondStatement",
                 "Effect", "Allow",
                 "Action", "s3:ListAllMyBuckets",
                 "Resource", "*"), Map.of(
                 "Sid", "ThirdStatement",
                 "Effect", "Allow",
                 "Action", List.of("s3:List*", "s3:Get*"),
                 "Resource", List.of("arn:aws:s3:::confidential-data", "arn:aws:s3:::confidential-data/*"),
                 "Condition", Map.of("Bool", Map.of("aws:MultiFactorAuthPresent", "true")))));
 
 PolicyDocument customPolicyDocument = PolicyDocument.fromJson(policyDocument);
 
 // You can pass this document as an initial document to a ManagedPolicy
 // or inline Policy.
 ManagedPolicy newManagedPolicy = ManagedPolicy.Builder.create(this, "MyNewManagedPolicy")
         .document(customPolicyDocument)
         .build();
 Policy newPolicy = Policy.Builder.create(this, "MyNewPolicy")
         .document(customPolicyDocument)
         .build();
 

Permissions Boundaries

Permissions Boundaries can be used as a mechanism to prevent privilege esclation by creating new Roles. Permissions Boundaries are a Managed Policy, attached to Roles or Users, that represent the maximum set of permissions they can have. The effective set of permissions of a Role (or User) will be the intersection of the Identity Policy and the Permissions Boundary attached to the Role (or User). Permissions Boundaries are typically created by account Administrators, and their use on newly created Roles will be enforced by IAM policies.

It is possible to attach Permissions Boundaries to all Roles created in a construct tree all at once:

 // Directly apply the boundary to a Role you create
 Role role;
 
 // Apply the boundary to an Role that was implicitly created for you
 Function fn;
 
 // Remove a Permissions Boundary that is inherited, for example from the Stack level
 CustomResource customResource;
 // This imports an existing policy.
 IManagedPolicy boundary = ManagedPolicy.fromManagedPolicyArn(this, "Boundary", "arn:aws:iam::123456789012:policy/boundary");
 
 // This creates a new boundary
 ManagedPolicy boundary2 = ManagedPolicy.Builder.create(this, "Boundary2")
         .statements(List.of(
             PolicyStatement.Builder.create()
                     .effect(Effect.DENY)
                     .actions(List.of("iam:*"))
                     .resources(List.of("*"))
                     .build()))
         .build();
 PermissionsBoundary.of(role).apply(boundary);
 PermissionsBoundary.of(fn).apply(boundary);
 
 // Apply the boundary to all Roles in a stack
 PermissionsBoundary.of(this).apply(boundary);
 PermissionsBoundary.of(customResource).clear();
 

OpenID Connect Providers

OIDC identity providers are entities in IAM that describe an external identity provider (IdP) service that supports the OpenID Connect (OIDC) standard, such as Google or Salesforce. You use an IAM OIDC identity provider when you want to establish trust between an OIDC-compatible IdP and your AWS account. This is useful when creating a mobile app or web application that requires access to AWS resources, but you don't want to create custom sign-in code or manage your own user identities. For more information about this scenario, see [About Web Identity Federation] and the relevant documentation in the [Amazon Cognito Identity Pools Developer Guide].

The following examples defines an OpenID Connect provider. Two client IDs (audiences) are will be able to send authentication requests to https://openid/connect.

 OpenIdConnectProvider provider = OpenIdConnectProvider.Builder.create(this, "MyProvider")
         .url("https://openid/connect")
         .clientIds(List.of("myclient1", "myclient2"))
         .build();
 

You can specify an optional list of thumbprints. If not specified, the thumbprint of the root certificate authority (CA) will automatically be obtained from the host as described here.

Once you define an OpenID connect provider, you can use it with AWS services that expect an IAM OIDC provider. For example, when you define an Amazon Cognito identity pool you can reference the provider's ARN as follows:

 import software.amazon.awscdk.services.cognito.*;
 
 OpenIdConnectProvider myProvider;
 
 CfnIdentityPool.Builder.create(this, "IdentityPool")
         .openIdConnectProviderArns(List.of(myProvider.getOpenIdConnectProviderArn()))
         // And the other properties for your identity pool
         .allowUnauthenticatedIdentities(false)
         .build();
 

The OpenIdConnectPrincipal class can be used as a principal used with a OpenIdConnectProvider, for example:

 OpenIdConnectProvider provider = OpenIdConnectProvider.Builder.create(this, "MyProvider")
         .url("https://openid/connect")
         .clientIds(List.of("myclient1", "myclient2"))
         .build();
 OpenIdConnectPrincipal principal = new OpenIdConnectPrincipal(provider);
 

SAML provider

An IAM SAML 2.0 identity provider is an entity in IAM that describes an external identity provider (IdP) service that supports the SAML 2.0 (Security Assertion Markup Language 2.0) standard. You use an IAM identity provider when you want to establish trust between a SAML-compatible IdP such as Shibboleth or Active Directory Federation Services and AWS, so that users in your organization can access AWS resources. IAM SAML identity providers are used as principals in an IAM trust policy.

 SamlProvider.Builder.create(this, "Provider")
         .metadataDocument(SamlMetadataDocument.fromFile("/path/to/saml-metadata-document.xml"))
         .build();
 

The SamlPrincipal class can be used as a principal with a SamlProvider:

 SamlProvider provider = SamlProvider.Builder.create(this, "Provider")
         .metadataDocument(SamlMetadataDocument.fromFile("/path/to/saml-metadata-document.xml"))
         .build();
 SamlPrincipal principal = new SamlPrincipal(provider, Map.of(
         "StringEquals", Map.of(
                 "SAML:iss", "issuer")));
 

When creating a role for programmatic and AWS Management Console access, use the SamlConsolePrincipal class:

 SamlProvider provider = SamlProvider.Builder.create(this, "Provider")
         .metadataDocument(SamlMetadataDocument.fromFile("/path/to/saml-metadata-document.xml"))
         .build();
 Role.Builder.create(this, "Role")
         .assumedBy(new SamlConsolePrincipal(provider))
         .build();
 

Users

IAM manages users for your AWS account. To create a new user:

 User user = new User(this, "MyUser");
 

To import an existing user by name with path:

 IUser user = User.fromUserName(this, "MyImportedUserByName", "johnsmith");
 

To import an existing user by ARN:

 IUser user = User.fromUserArn(this, "MyImportedUserByArn", "arn:aws:iam::123456789012:user/johnsmith");
 

To import an existing user by attributes:

 IUser user = User.fromUserAttributes(this, "MyImportedUserByAttributes", UserAttributes.builder()
         .userArn("arn:aws:iam::123456789012:user/johnsmith")
         .build());
 

To add a user to a group (both for a new and imported user/group):

 User user = new User(this, "MyUser"); // or User.fromUserName(stack, 'User', 'johnsmith');
 Group group = new Group(this, "MyGroup"); // or Group.fromGroupArn(stack, 'Group', 'arn:aws:iam::account-id:group/group-name');
 
 user.addToGroup(group);
 // or
 group.addUser(user);
 

Features

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