AssumeRole - Amazon Security Token Service
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AssumeRole

Returns a set of temporary security credentials that you can use to access Amazon resources that you might not normally have access to. These temporary credentials consist of an access key ID, a secret access key, and a security token. Typically, you use AssumeRole within your account or for cross-account access. For a comparison of AssumeRole with other API operations that produce temporary credentials, see Requesting Temporary Security Credentials and Comparing the Amazon STS API operations in the IAM User Guide.

Permissions

The temporary security credentials created by AssumeRole can be used to make API calls to any Amazon service with the following exception: You cannot call the Amazon STS GetFederationToken or GetSessionToken API operations.

(Optional) You can pass inline or managed session policies to this operation. You can pass a single JSON policy document to use as an inline session policy. You can also specify up to 10 managed policies to use as managed session policies. The plaintext that you use for both inline and managed session policies can't exceed 2,048 characters. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent Amazon API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

To assume a role from a different account, your Amazon Web Services account must be trusted by the role. The trust relationship is defined in the role's trust policy when the role is created. That trust policy states which accounts are allowed to delegate that access to users in the account.

A user who wants to access a role in a different account must also have permissions that are delegated from the user account administrator. The administrator must attach a policy that allows the user to call AssumeRole for the ARN of the role in the other account. If the user is in the same account as the role, then you can do either of the following:

  • Attach a policy to the user (identical to the previous user in a different account).

  • Add the user as a principal directly in the role's trust policy.

In this case, the trust policy acts as an IAM resource-based policy. Users in the same account as the role do not need explicit permission to assume the role. For more information about trust policies and resource-based policies, see IAM Policies in the IAM User Guide.

Tags

(Optional) You can pass tag key-value pairs to your session. These tags are called session tags. For more information about session tags, see Passing Session Tags in Amazon STS in the IAM User Guide.

An administrator must grant you the permissions necessary to pass session tags. The administrator can also create granular permissions to allow you to pass only specific session tags. For more information, see Tutorial: Using Tags for Attribute-Based Access Control in the IAM User Guide.

You can set the session tags as transitive. Transitive tags persist during role chaining. For more information, see Chaining Roles with Session Tags in the IAM User Guide.

Using MFA with AssumeRole

(Optional) You can include multi-factor authentication (MFA) information when you call AssumeRole. This is useful for cross-account scenarios to ensure that the user that assumes the role has been authenticated with an Amazon MFA device. In that scenario, the trust policy of the role being assumed includes a condition that tests for MFA authentication. If the caller does not include valid MFA information, the request to assume the role is denied. The condition in a trust policy that tests for MFA authentication might look like the following example.

"Condition": {"Bool": {"aws:MultiFactorAuthPresent": true}}

For more information, see Configuring MFA-Protected API Access in the IAM User Guide guide.

To use MFA with AssumeRole, you pass values for the SerialNumber and TokenCode parameters. The SerialNumber value identifies the user's hardware or virtual MFA device. The TokenCode is the time-based one-time password (TOTP) that the MFA device produces.

Request Parameters

For information about the parameters that are common to all actions, see Common Parameters.

DurationSeconds

The duration, in seconds, of the role session. The value specified can range from 900 seconds (15 minutes) up to the maximum session duration set for the role. The maximum session duration setting can have a value from 1 hour to 12 hours. If you specify a value higher than this setting or the administrator setting (whichever is lower), the operation fails. For example, if you specify a session duration of 12 hours, but your administrator set the maximum session duration to 6 hours, your operation fails.

Role chaining limits your Amazon CLI or Amazon API role session to a maximum of one hour. When you use the AssumeRole API operation to assume a role, you can specify the duration of your role session with the DurationSeconds parameter. You can specify a parameter value of up to 43200 seconds (12 hours), depending on the maximum session duration setting for your role. However, if you assume a role using role chaining and provide a DurationSeconds parameter value greater than one hour, the operation fails. To learn how to view the maximum value for your role, see View the Maximum Session Duration Setting for a Role in the IAM User Guide.

By default, the value is set to 3600 seconds.

Note

The DurationSeconds parameter is separate from the duration of a console session that you might request using the returned credentials. The request to the federation endpoint for a console sign-in token takes a SessionDuration parameter that specifies the maximum length of the console session. For more information, see Creating a URL that Enables Federated Users to Access the Amazon Web Services Management Console in the IAM User Guide.

Type: Integer

Valid Range: Minimum value of 900. Maximum value of 43200.

Required: No

ExternalId

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. A cross-account role is usually set up to trust everyone in an account. Therefore, the administrator of the trusting account might send an external ID to the administrator of the trusted account. That way, only someone with the ID can assume the role, rather than everyone in the account. For more information about the external ID, see How to Use an External ID When Granting Access to Your Amazon Resources to a Third Party in the IAM User Guide.

The regex used to validate this parameter is a string of characters consisting of upper- and lower-case alphanumeric characters with no spaces. You can also include underscores or any of the following characters: =,.@:/-

Type: String

Length Constraints: Minimum length of 2. Maximum length of 1224.

Pattern: [\w+=,.@:\/-]*

Required: No

Policy

An IAM policy in JSON format that you want to use as an inline session policy.

This parameter is optional. Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent Amazon API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

The plaintext that you use for both inline and managed session policies can't exceed 2,048 characters. The JSON policy characters can be any ASCII character from the space character to the end of the valid character list (\u0020 through \u00FF). It can also include the tab (\u0009), linefeed (\u000A), and carriage return (\u000D) characters.

Note

An Amazon conversion compresses the passed session policies and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plaintext meets the other requirements. The PackedPolicySize response element indicates by percentage how close the policies and tags for your request are to the upper size limit.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 2048.

Pattern: [\u0009\u000A\u000D\u0020-\u00FF]+

Required: No

PolicyArns.member.N

The Amazon Resource Names (ARNs) of the IAM managed policies that you want to use as managed session policies. The policies must exist in the same account as the role.

This parameter is optional. You can provide up to 10 managed policy ARNs. However, the plaintext that you use for both inline and managed session policies can't exceed 2,048 characters. For more information about ARNs, see Amazon Resource Names (ARNs) and Amazon Service Namespaces in the Amazon General Reference.

Note

An Amazon conversion compresses the passed session policies and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plaintext meets the other requirements. The PackedPolicySize response element indicates by percentage how close the policies and tags for your request are to the upper size limit.

Passing policies to this operation returns new temporary credentials. The resulting session's permissions are the intersection of the role's identity-based policy and the session policies. You can use the role's temporary credentials in subsequent Amazon API calls to access resources in the account that owns the role. You cannot use session policies to grant more permissions than those allowed by the identity-based policy of the role that is being assumed. For more information, see Session Policies in the IAM User Guide.

Type: Array of PolicyDescriptorType objects

Required: No

RoleArn

The Amazon Resource Name (ARN) of the role to assume.

Type: String

Length Constraints: Minimum length of 20. Maximum length of 2048.

Pattern: [\u0009\u000A\u000D\u0020-\u007E\u0085\u00A0-\uD7FF\uE000-\uFFFD\u10000-\u10FFFF]+

Required: Yes

RoleSessionName

An identifier for the assumed role session.

Use the role session name to uniquely identify a session when the same role is assumed by different principals or for different reasons. In cross-account scenarios, the role session name is visible to, and can be logged by the account that owns the role. The role session name is also used in the ARN of the assumed role principal. This means that subsequent cross-account API requests that use the temporary security credentials will expose the role session name to the external account in their Amazon CloudTrail logs.

The regex used to validate this parameter is a string of characters consisting of upper- and lower-case alphanumeric characters with no spaces. You can also include underscores or any of the following characters: =,.@-

Type: String

Length Constraints: Minimum length of 2. Maximum length of 64.

Pattern: [\w+=,.@-]*

Required: Yes

SerialNumber

The identification number of the MFA device that is associated with the user who is making the AssumeRole call. Specify this value if the trust policy of the role being assumed includes a condition that requires MFA authentication. The value is either the serial number for a hardware device (such as GAHT12345678) or an Amazon Resource Name (ARN) for a virtual device (such as arn:aws:iam::123456789012:mfa/user).

The regex used to validate this parameter is a string of characters consisting of upper- and lower-case alphanumeric characters with no spaces. You can also include underscores or any of the following characters: =,.@-

Type: String

Length Constraints: Minimum length of 9. Maximum length of 256.

Pattern: [\w+=/:,.@-]*

Required: No

SourceIdentity

The source identity specified by the principal that is calling the AssumeRole operation.

You can require users to specify a source identity when they assume a role. You do this by using the sts:SourceIdentity condition key in a role trust policy. You can use source identity information in Amazon CloudTrail logs to determine who took actions with a role. You can use the aws:SourceIdentity condition key to further control access to Amazon resources based on the value of source identity. For more information about using source identity, see Monitor and control actions taken with assumed roles in the IAM User Guide.

The regex used to validate this parameter is a string of characters consisting of upper- and lower-case alphanumeric characters with no spaces. You can also include underscores or any of the following characters: =,.@-. You cannot use a value that begins with the text aws:. This prefix is reserved for Amazon internal use.

Type: String

Length Constraints: Minimum length of 2. Maximum length of 64.

Pattern: [\w+=,.@-]*

Required: No

Tags.member.N

A list of session tags that you want to pass. Each session tag consists of a key name and an associated value. For more information about session tags, see Tagging Amazon STS Sessions in the IAM User Guide.

This parameter is optional. You can pass up to 50 session tags. The plaintext session tag keys can’t exceed 128 characters, and the values can’t exceed 256 characters. For these and additional limits, see IAM and Amazon STS Character Limits in the IAM User Guide.

Note

An Amazon conversion compresses the passed session policies and session tags into a packed binary format that has a separate limit. Your request can fail for this limit even if your plaintext meets the other requirements. The PackedPolicySize response element indicates by percentage how close the policies and tags for your request are to the upper size limit.

You can pass a session tag with the same key as a tag that is already attached to the role. When you do, session tags override a role tag with the same key.

Tag key–value pairs are not case sensitive, but case is preserved. This means that you cannot have separate Department and department tag keys. Assume that the role has the Department=Marketing tag and you pass the department=engineering session tag. Department and department are not saved as separate tags, and the session tag passed in the request takes precedence over the role tag.

Additionally, if you used temporary credentials to perform this operation, the new session inherits any transitive session tags from the calling session. If you pass a session tag with the same key as an inherited tag, the operation fails. To view the inherited tags for a session, see the Amazon CloudTrail logs. For more information, see Viewing Session Tags in CloudTrail in the IAM User Guide.

Type: Array of Tag objects

Array Members: Maximum number of 50 items.

Required: No

TokenCode

The value provided by the MFA device, if the trust policy of the role being assumed requires MFA. (In other words, if the policy includes a condition that tests for MFA). If the role being assumed requires MFA and if the TokenCode value is missing or expired, the AssumeRole call returns an "access denied" error.

The format for this parameter, as described by its regex pattern, is a sequence of six numeric digits.

Type: String

Length Constraints: Fixed length of 6.

Pattern: [\d]*

Required: No

TransitiveTagKeys.member.N

A list of keys for session tags that you want to set as transitive. If you set a tag key as transitive, the corresponding key and value passes to subsequent sessions in a role chain. For more information, see Chaining Roles with Session Tags in the IAM User Guide.

This parameter is optional. When you set session tags as transitive, the session policy and session tags packed binary limit is not affected.

If you choose not to specify a transitive tag key, then no tags are passed from this session to any subsequent sessions.

Type: Array of strings

Array Members: Maximum number of 50 items.

Length Constraints: Minimum length of 1. Maximum length of 128.

Pattern: [\p{L}\p{Z}\p{N}_.:/=+\-@]+

Required: No

Response Elements

The following elements are returned by the service.

AssumedRoleUser

The Amazon Resource Name (ARN) and the assumed role ID, which are identifiers that you can use to refer to the resulting temporary security credentials. For example, you can reference these credentials as a principal in a resource-based policy by using the ARN or assumed role ID. The ARN and ID include the RoleSessionName that you specified when you called AssumeRole.

Type: AssumedRoleUser object

Credentials

The temporary security credentials, which include an access key ID, a secret access key, and a security (or session) token.

Note

The size of the security token that Amazon STS API operations return is not fixed. We strongly recommend that you make no assumptions about the maximum size.

Type: Credentials object

PackedPolicySize

A percentage value that indicates the packed size of the session policies and session tags combined passed in the request. The request fails if the packed size is greater than 100 percent, which means the policies and tags exceeded the allowed space.

Type: Integer

Valid Range: Minimum value of 0.

SourceIdentity

The source identity specified by the principal that is calling the AssumeRole operation.

You can require users to specify a source identity when they assume a role. You do this by using the sts:SourceIdentity condition key in a role trust policy. You can use source identity information in Amazon CloudTrail logs to determine who took actions with a role. You can use the aws:SourceIdentity condition key to further control access to Amazon resources based on the value of source identity. For more information about using source identity, see Monitor and control actions taken with assumed roles in the IAM User Guide.

The regex used to validate this parameter is a string of characters consisting of upper- and lower-case alphanumeric characters with no spaces. You can also include underscores or any of the following characters: =,.@-

Type: String

Length Constraints: Minimum length of 2. Maximum length of 64.

Pattern: [\w+=,.@-]*

Errors

For information about the errors that are common to all actions, see Common Errors.

ExpiredToken

The web identity token that was passed is expired or is not valid. Get a new identity token from the identity provider and then retry the request.

HTTP Status Code: 400

MalformedPolicyDocument

The request was rejected because the policy document was malformed. The error message describes the specific error.

HTTP Status Code: 400

PackedPolicyTooLarge

The request was rejected because the total packed size of the session policies and session tags combined was too large. An Amazon conversion compresses the session policy document, session policy ARNs, and session tags into a packed binary format that has a separate limit. The error message indicates by percentage how close the policies and tags are to the upper size limit. For more information, see Passing Session Tags in Amazon STS in the IAM User Guide.

You could receive this error even though you meet other defined session policy and session tag limits. For more information, see IAM and Amazon STS Entity Character Limits in the IAM User Guide.

HTTP Status Code: 400

RegionDisabled

Amazon STS is not activated in the requested region for the account that is being asked to generate credentials. The account administrator must use the IAM console to activate Amazon STS in that region. For more information, see Activating and Deactivating Amazon Amazon STS in an Amazon Region in the IAM User Guide.

HTTP Status Code: 403

Examples

Example

This example illustrates one usage of AssumeRole.

Sample Request

https://sts.amazonaws.com/ ?Version=2011-06-15 &Action=AssumeRole &RoleSessionName=testAR &RoleArn=arn:aws:iam::123456789012:role/demo &PolicyArns.member.1.arn=arn:aws:iam::123456789012:policy/demopolicy1 &PolicyArns.member.2.arn=arn:aws:iam::123456789012:policy/demopolicy2 &Policy={"Version":"2012-10-17","Statement":[{"Sid":"Stmt1", "Effect":"Allow","Action":"s3:*","Resource":"*"}]} &DurationSeconds=3600 &Tags.member.1.Key=Project &Tags.member.1.Value=Pegasus &Tags.member.2.Key=Team &Tags.member.2.Value=Engineering &Tags.member.3.Key=Cost-Center &Tags.member.3.Value=12345 &TransitiveTagKeys.member.1=Project &TransitiveTagKeys.member.2=Cost-Center &ExternalId=123ABC &SourceIdentity=Alice &AUTHPARAMS

Sample Response

<AssumeRoleResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/"> <AssumeRoleResult> <SourceIdentity>Alice</SourceIdentity> <AssumedRoleUser> <Arn>arn:aws:sts::123456789012:assumed-role/demo/TestAR</Arn> <AssumedRoleId>ARO123EXAMPLE123:TestAR</AssumedRoleId> </AssumedRoleUser> <Credentials> <AccessKeyId>ASIAIOSFODNN7EXAMPLE</AccessKeyId> <SecretAccessKey>wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY</SecretAccessKey> <SessionToken> AQoDYXdzEPT//////////wEXAMPLEtc764bNrC9SAPBSM22wDOk4x4HIZ8j4FZTwdQW LWsKWHGBuFqwAeMicRXmxfpSPfIeoIYRqTflfKD8YUuwthAx7mSEI/qkPpKPi/kMcGd QrmGdeehM4IC1NtBmUpp2wUE8phUZampKsburEDy0KPkyQDYwT7WZ0wq5VSXDvp75YU 9HFvlRd8Tx6q6fE8YQcHNVXAkiY9q6d+xo0rKwT38xVqr7ZD0u0iPPkUL64lIZbqBAz +scqKmlzm8FDrypNC9Yjc8fPOLn9FX9KSYvKTr4rvx3iSIlTJabIQwj2ICCR/oLxBA== </SessionToken> <Expiration>2019-11-09T13:34:41Z</Expiration> </Credentials> <PackedPolicySize>6</PackedPolicySize> </AssumeRoleResult> <ResponseMetadata> <RequestId>c6104cbe-af31-11e0-8154-cbc7ccf896c7</RequestId> </ResponseMetadata> </AssumeRoleResponse>

See Also

For more information about using this API in one of the language-specific Amazon SDKs, see the following: