AWS Identity and Access Management

User Guide

IAM and AWS STS Condition Context Keys

You can use the Condition element of a JSON policy in IAM to test the value of keys that are included in the evaluation context of all AWS API requests. These keys provide information about the request itself or the resources that the request references. You can check that keys have specified values before allowing the action requested by the user. This gives you granular control over when your JSON policy statements match or don't match an incoming API request. For information about how to use the Condition element in a JSON policy, see IAM JSON Policy Elements: Condition.

This topic describes the keys defined and provided by the IAM service (with an iam: prefix) and the AWS Security Token Service (AWS STS) service (with an sts: prefix). Several other AWS services also provide service-specific keys that are relevant to the actions and resources defined by that service. For more information, see Actions, Resources, and Condition Keys for AWS Services. The documentation for a service that supports condition keys often has additional information. For example, for information about keys that you can use in policies for Amazon S3 resources, see Amazon S3 Policy Keys in the Amazon Simple Storage Service Developer Guide.

Topics

Available Keys for IAM
Available Keys for AWS Web Identity Federation
Available Keys for SAML-Based AWS STS Federation
Available Keys for AWS STS

Available Keys for IAM

You can use the following condition keys in policies that control access to IAM resources:

iam:AWSServiceName

Works with string operators.

Specifies the AWS service to which this role is attached.

iam:PassedToService

Works with string operators.

Specifies the service principal of the service to which a role can be passed. A service principal is the name of a service that can be specified in the Principal element of a policy. This is the usual format: SERVICE_NAME_URL.amazonaws.com. In the iam:PassedToService condition key, provide the service principal of the service that will assume the role.

You can use iam:PassedToService to restrict your users so that they can pass roles only to specific services. For example, a user might create a service role that trusts CloudWatch to write log data to an Amazon S3 bucket on their behalf. Then the user must attach a permissions policy and a trust policy to the new service role. In this case, the trust policy must specify cloudwatch.amazonaws.com in the Principal element. Attach the following policy to allow the user to pass the role to CloudWatch:


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "iam:PassRole",
            "Resource": "*",
            "Condition": {"StringEquals": {"iam:PassedToService": "cloudwatch.amazonaws.com"}}
        }
    ]
}

By using this condition key, you can ensure that users create service roles only for the services that you specify. For example, if a user with the preceding policy attempts to create a service role for Amazon EC2, the operation will fail because the user does not have permission to pass the role to Amazon EC2.

iam:PermissionsBoundary

Works with string operators.

Checks that the specified policy is attached as permissions boundary on the IAM principal resource. For more information, see Permissions Boundaries for IAM Entities

iam:PolicyARN

Works with ARN operators.

Checks the Amazon Resource Name (ARN) of a managed policy in requests that involve a managed policy. For more information, see Controlling Access to Policies.

iam:ResourceTag/key-name

Works with string operators.

Checks that the tag attached to the identity resource (user or role) matches the specified key name and value.

You can add custom attributes to a user or role in the form of a key–value pair. For more information about IAM tags, see Tagging IAM Entities. You can use iam:ResourceTag to control access to IAM users and roles. However, because IAM does not support tags for groups, you cannot use tags to control access to groups.

This example shows how you might create a policy that allows deleting users with the status=terminated tag. To use this policy, replace the red italicized text in the example policy with your own information.


{
    "Version": "2012-10-17",
    "Statement": [{
        "Effect": "Allow",
        "Action": "iam:DeleteUser",
        "Resource": "*",
        "Condition": {"StringLike": {"iam:ResourceTag/status": "terminated"}}
    }]
}

Available Keys for AWS Web Identity Federation

You can use web identity federation to give temporary security credentials to users who have been authenticated through an identity provider (IdP). Examples of such providers include Login with Amazon, Amazon Cognito, Google, or Facebook. In that case, additional condition keys are available when the temporary security credentials are used to make a request. You can use these keys to write policies that make sure that federated users can get access only to resources that are associated with a specific provider, app, or user.

aws:FederatedProvider

Works with string operators.

The FederatedProvider key identifies which of the IdPs was used to authenticate the user. For example, if the user was authenticated through Amazon Cognito, the key would contain cognito-identity.amazonaws.com. Similarly, if the user was authenticated through Login with Amazon, the key would contain the value www.amazon.com. You might use the key in a resource policy like the following, which uses the aws:FederatedProvider key as a policy variable in the ARN of a resource. The policy allows any user who has been authenticated using an IdP to get objects out of a folder in an Amazon S3 bucket. However, the bucket must be specific to the provider that the user authenticates with.


{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Principal": "*",
    "Action": "s3:GetObject",
    "Resource": "arn:aws:s3:::BUCKET-NAME/${aws:FederatedProvider}/*"
  }
}

Application ID and User ID

Works with string operators.

You can also use two keys that provide a unique identifier for the user and an identifier for the application or site that the user authenticated with. These keys have the following IdP-specific names:

For Amazon Cognito users, the keys are cognito-identity.amazonaws.com:aud (for the identity pool ID) and cognito-identity.amazonaws.com:sub (for the user ID).
For Login with Amazon users, the keys are www.amazon.com:app_id and www.amazon.com:user_id
For Facebook users, the keys are graph.facebook.com:app_id and graph.facebook.com:id
For Google users, the keys are accounts.google.com:aud (for the app ID) and accounts.google.com:sub (for the user ID).

The amr Key in Amazon Cognito

Works with string operators.

If you are using Amazon Cognito for web identity federation, the cognito-identity.amazonaws.com:amr key (Authentication Methods Reference) in a trust policy includes login information about the user. The key is multivalued, meaning that you test it in a policy using condition set operators. The key can contain the following values:

If the user is unauthenticated, the key contains only unauthenticated.
If the user is authenticated, the key contains the value authenticated and the name of the login provider used in the call (graph.facebook.com, accounts.google.com, or www.amazon.com).

As an example, the following condition in the trust policy for an Amazon Cognito role tests whether the user is unauthenticated:


"Condition": {
  "StringEquals": 
    { "cognito-identity.amazonaws.com:aud": "us-east-2:identity-pool-id" },
  "ForAnyValue:StringLike": 
    { "cognito-identity.amazonaws.com:amr": "unauthenticated" }
}

More Information About Web Identity Federation

For more information about web identity federation, see the following:

Amazon Cognito Overview in the AWS Mobile SDK for Android Developer Guide guide
Amazon Cognito Overview in the AWS Mobile SDK for iOS Developer Guide guide
About Web Identity Federation

Available Keys for SAML-Based AWS STS Federation

If you are working with SAML-based federation using AWS Security Token Service (AWS STS), you can include additional condition keys in the policy.

SAML Role Trust Policies

In the trust policy of a role, you can include the following keys, which help you establish whether the caller is allowed to assume the role. Except for saml:doc, all the values are derived from the SAML assertion. Items in the list that are marked with an asterisk (*) are available in the console UI to create conditions. Items marked with [] can have a value that is a list of the specified type.

saml:aud

Works with string operators.

An endpoint URL to which SAML assertions are presented. The value for this key comes from the SAML Recipient field in the assertion, not the Audience field.

saml:cn[]

Works with string operators.

This is an eduOrg attribute.

saml:doc*

Works with string operators.

This represents the principal that was used to assume the role. The format is account-ID/provider-friendly-name, such as 123456789012/SAMLProviderName. The account-ID value refers to the account that owns the SAML provider.

saml:edupersonaffiliation[]

Works with string operators.

This is an eduPerson attribute.

saml:edupersonassurance[]

Works with string operators.

This is an eduPerson attribute.

saml:edupersonentitlement[]*

Works with string operators.

This is an eduPerson attribute.

saml:edupersonnickname[]

Works with string operators.

This is an eduPerson attribute.

saml:edupersonorgdn*

Works with string operators.

This is an eduPerson attribute.

saml:edupersonorgunitdn[]

Works with string operators.

This is an eduPerson attribute.

saml:edupersonprimaryaffiliation

Works with string operators.

This is an eduPerson attribute.

saml:edupersonprimaryorgunitdn

Works with string operators.

This is an eduPerson attribute.

saml:edupersonprincipalname

Works with string operators.

This is an eduPerson attribute.

saml:edupersonscopedaffiliation[]

Works with string operators.

This is an eduPerson attribute.

saml:edupersontargetedid[]

Works with string operators.

This is an eduPerson attribute.

saml:eduorghomepageuri[]

Works with string operators.

This is an eduOrg attribute.

saml:eduorgidentityauthnpolicyuri[]

Works with string operators.

This is an eduOrg attribute.

saml:eduorglegalname[]

Works with string operators.

This is an eduOrg attribute.

saml:eduorgsuperioruri[]

Works with string operators.

This is an eduOrg attribute.

saml:eduorgwhitepagesuri[]

Works with string operators.

This is an eduOrg attribute.

saml:namequalifier*

Works with string operators.

A hash value based on the concatenation of the Issuer response value (saml:iss), the AWS account ID and the friendly name (the last part of the ARN) of the SAML provider in IAM, separated by a '/' character. The concatenation of the account ID and friendly name of the SAML provider is available to IAM policies as the key saml:doc. For more information, see Uniquely Identifying Users in SAML-Based Federation.

saml:iss*

Works with string operators.

The issuer, which is represented by a URN.

saml:sub*

Works with string operators.

This is the subject of the claim, which includes a value that uniquely identifies an individual user within an organization (for example, _cbb88bf52c2510eabe00c1642d4643f41430fe25e3).

saml:sub_type*

Works with string operators.

This key can have the value persistent, transient, or consist of the full Format URI from the Subject and NameID elements used in your SAML assertion. A value of persistent indicates that the value in saml:sub is the same for a user between sessions. If the value is transient, the user has a different saml:sub value for each session. For information about the NameID element's Format attribute, see Configuring SAML Assertions for the Authentication Response.

For general information about eduPerson and eduOrg attributes, see the Internet2 website. For a list of eduPerson attributes, see eduPerson Object Class Specification (201203).

Condition keys whose type is a list can include multiple values. To create conditions in the policy for list values, you can use set operators (ForAllValues, ForAnyValue). For example, to allow any user whose affiliation is "faculty", "staff", or "employee" (but not "student", "alum", or other possible affiliations), you might use a condition like the following:


"Condition": {
   "ForAllValues:StringLike": {
     "saml:edupersonaffiliation":[ "faculty", "staff", "employee" ] 
   }
}

SAML Role Permission Policies

In the permission policy of a role for SAML federation that defines what users are allowed to access in AWS, you can include the following keys:

saml:namequalifier

Works with string operators.

This contains a hash value that represents the combination of the saml:doc and saml:iss values. It is used as a namespace qualifier; the combination of saml:namequalifier and saml:sub uniquely identifies a user.

saml:sub

Works with string operators.

This is the subject of the claim, which includes a value that uniquely identifies an individual user within an organization (for example, _cbb88bf52c2510eabe00c1642d4643f41430fe25e3).

saml:sub_type

Works with string operators.

This key can have the value persistent, transient, or consist of the full Format URI from the Subject and NameID elements used in your SAML assertion. A value of persistent indicates that the value in saml:sub is the same for a user between sessions. If the value is transient, the user has a different saml:sub value for each session. For information about the NameID element's Format attribute, see Configuring SAML Assertions for the Authentication Response.

For more information about using these keys, see About SAML 2.0-based Federation.

Available Keys for AWS STS

You can use the following condition keys in IAM role trust policies for roles that are assumed using AWS Security Token Service (AWS STS) operations.

sts:ExternalId

Works with string operators.

A unique identifier that might be required when you assume a role in another account. If the administrator of the account to which the role belongs provided you with an external ID, then provide that value in the ExternalId parameter. This value can be any string, such as a passphrase or account number. The primary function of the external ID is to address and prevent the confused deputy problem. For more information about the external ID and the confused deputy problem, see How to Use an External ID When Granting Access to Your AWS Resources to a Third Party.

The ExternalId value must have a minimum of 2 characters and a maximum of 1,224 characters. The value must be alphanumeric without white space. It can also include the following symbols: plus (+), equal (=), comma (,), period (.), at (@), colon (:), forward slash (/), and hyphen (-).

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On this page:

Available Keys for IAM
Available Keys for AWS Web Identity Federation
Available Keys for SAML-Based AWS STS Federation
Available Keys for AWS STS