AWS Security Token Service

2015/05/07 - AWS Security Token Service - 6 new api methods

DecodeAuthorizationMessage (new) Link ¶

Decodes additional information about the authorization status of a request from an encoded message returned in response to an AWS request.

For example, if a user is not authorized to perform an action that he or she has requested, the request returns a Client.UnauthorizedOperation response (an HTTP 403 response). Some AWS actions additionally return an encoded message that can provide details about this authorization failure.

The message is encoded because the details of the authorization status can constitute privileged information that the user who requested the action should not see. To decode an authorization status message, a user must be granted permissions via an IAM policy to request the DecodeAuthorizationMessage ( sts:DecodeAuthorizationMessage) action.

The decoded message includes the following type of information:

  • Whether the request was denied due to an explicit deny or due to the absence of an explicit allow. For more information, see Determining Whether a Request is Allowed or Denied in Using IAM.

  • The principal who made the request.

  • The requested action.

  • The requested resource.

  • The values of condition keys in the context of the user's request.

Request Syntax

client.decode_authorization_message(
    EncodedMessage='string'
)
type EncodedMessage:

string

param EncodedMessage:

[REQUIRED]

The encoded message that was returned with the response.

rtype:

dict

returns:

Response Syntax

{
    'DecodedMessage': 'string'
}

Response Structure

  • (dict) --

    A document that contains additional information about the authorization status of a request from an encoded message that is returned in response to an AWS request.

    • DecodedMessage (string) --

      An XML document that contains the decoded message. For more information, see DecodeAuthorizationMessage.

GetSessionToken (new) Link ¶

Returns a set of temporary credentials for an AWS account or IAM user. The credentials consist of an access key ID, a secret access key, and a security token. Typically, you use GetSessionToken if you want to use MFA to protect programmatic calls to specific AWS APIs like Amazon EC2 StopInstances. MFA-enabled IAM users would need to call GetSessionToken and submit an MFA code that is associated with their MFA device. Using the temporary security credentials that are returned from the call, IAM users can then make programmatic calls to APIs that require MFA authentication.

The GetSessionToken action must be called by using the long-term AWS security credentials of the AWS account or an IAM user. Credentials that are created by IAM users are valid for the duration that you specify, between 900 seconds (15 minutes) and 129600 seconds (36 hours); credentials that are created by using account credentials have a maximum duration of 3600 seconds (1 hour).

The permissions associated with the temporary security credentials returned by GetSessionToken are based on the permissions associated with account or IAM user whose credentials are used to call the action. If GetSessionToken is called using root account credentials, the temporary credentials have root account permissions. Similarly, if GetSessionToken is called using the credentials of an IAM user, the temporary credentials have the same permissions as the IAM user.

For more information about using GetSessionToken to create temporary credentials, go to Creating Temporary Credentials to Enable Access for IAM Users in Using Temporary Security Credentials.

Request Syntax

client.get_session_token(
    DurationSeconds=123,
    SerialNumber='string',
    TokenCode='string'
)
type DurationSeconds:

integer

param DurationSeconds:

The duration, in seconds, that the credentials should remain valid. Acceptable durations for IAM user sessions range from 900 seconds (15 minutes) to 129600 seconds (36 hours), with 43200 seconds (12 hours) as the default. Sessions for AWS account owners are restricted to a maximum of 3600 seconds (one hour). If the duration is longer than one hour, the session for AWS account owners defaults to one hour.

type SerialNumber:

string

param SerialNumber:

The identification number of the MFA device that is associated with the IAM user who is making the GetSessionToken call. Specify this value if the IAM user has a policy 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). You can find the device for an IAM user by going to the AWS Management Console and viewing the user's security credentials.

type TokenCode:

string

param TokenCode:

The value provided by the MFA device, if MFA is required. If any policy requires the IAM user to submit an MFA code, specify this value. If MFA authentication is required, and the user does not provide a code when requesting a set of temporary security credentials, the user will receive an "access denied" response when requesting resources that require MFA authentication.

rtype:

dict

returns:

Response Syntax

{
    'Credentials': {
        'AccessKeyId': 'string',
        'SecretAccessKey': 'string',
        'SessionToken': 'string',
        'Expiration': datetime(2015, 1, 1)
    }
}

Response Structure

  • (dict) --

    Contains the response to a successful GetSessionToken request, including temporary AWS credentials that can be used to make AWS requests.

    • Credentials (dict) --

      The session credentials for API authentication.

      • AccessKeyId (string) --

        The access key ID that identifies the temporary security credentials.

      • SecretAccessKey (string) --

        The secret access key that can be used to sign requests.

      • SessionToken (string) --

        The token that users must pass to the service API to use the temporary credentials.

      • Expiration (datetime) --

        The date on which the current credentials expire.

AssumeRoleWithWebIdentity (new) Link ¶

Returns a set of temporary security credentials for users who have been authenticated in a mobile or web application with a web identity provider, such as Amazon Cognito, Login with Amazon, Facebook, Google, or any OpenID Connect-compatible identity provider.

Calling AssumeRoleWithWebIdentity does not require the use of AWS security credentials. Therefore, you can distribute an application (for example, on mobile devices) that requests temporary security credentials without including long-term AWS credentials in the application, and without deploying server-based proxy services that use long-term AWS credentials. Instead, the identity of the caller is validated by using a token from the web identity provider.

The temporary security credentials returned by this API consist of an access key ID, a secret access key, and a security token. Applications can use these temporary security credentials to sign calls to AWS service APIs. The credentials are valid for the duration that you specified when calling AssumeRoleWithWebIdentity, which can be from 900 seconds (15 minutes) to 3600 seconds (1 hour). By default, the temporary security credentials are valid for 1 hour.

Optionally, you can pass an IAM access policy to this operation. If you choose not to pass a policy, the temporary security credentials that are returned by the operation have the permissions that are defined in the access policy of the role that is being assumed. If you pass a policy to this operation, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRoleWithWebIdentity in Using Temporary Security Credentials.

Before your application can call AssumeRoleWithWebIdentity, you must have an identity token from a supported identity provider and create a role that the application can assume. The role that your application assumes must trust the identity provider that is associated with the identity token. In other words, the identity provider must be specified in the role's trust policy.

For more information about how to use web identity federation and the AssumeRoleWithWebIdentity API, see the following resources:

Request Syntax

client.assume_role_with_web_identity(
    RoleArn='string',
    RoleSessionName='string',
    WebIdentityToken='string',
    ProviderId='string',
    Policy='string',
    DurationSeconds=123
)
type RoleArn:

string

param RoleArn:

[REQUIRED]

The Amazon Resource Name (ARN) of the role that the caller is assuming.

type RoleSessionName:

string

param RoleSessionName:

[REQUIRED]

An identifier for the assumed role session. Typically, you pass the name or identifier that is associated with the user who is using your application. That way, the temporary security credentials that your application will use are associated with that user. This session name is included as part of the ARN and assumed role ID in the AssumedRoleUser response element.

type WebIdentityToken:

string

param WebIdentityToken:

[REQUIRED]

The OAuth 2.0 access token or OpenID Connect ID token that is provided by the identity provider. Your application must get this token by authenticating the user who is using your application with a web identity provider before the application makes an AssumeRoleWithWebIdentity call.

type ProviderId:

string

param ProviderId:

The fully qualified host component of the domain name of the identity provider.

Specify this value only for OAuth 2.0 access tokens. Currently www.amazon.com and graph.facebook.com are the only supported identity providers for OAuth 2.0 access tokens. Do not include URL schemes and port numbers.

Do not specify this value for OpenID Connect ID tokens.

type Policy:

string

param Policy:

An IAM policy in JSON format.

The policy parameter is optional. If you pass a policy, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRoleWithWebIdentity in Using Temporary Security Credentials.

type DurationSeconds:

integer

param DurationSeconds:

The duration, in seconds, of the role session. The value can range from 900 seconds (15 minutes) to 3600 seconds (1 hour). By default, the value is set to 3600 seconds.

rtype:

dict

returns:

Response Syntax

{
    'Credentials': {
        'AccessKeyId': 'string',
        'SecretAccessKey': 'string',
        'SessionToken': 'string',
        'Expiration': datetime(2015, 1, 1)
    },
    'SubjectFromWebIdentityToken': 'string',
    'AssumedRoleUser': {
        'AssumedRoleId': 'string',
        'Arn': 'string'
    },
    'PackedPolicySize': 123,
    'Provider': 'string',
    'Audience': 'string'
}

Response Structure

  • (dict) --

    Contains the response to a successful AssumeRoleWithWebIdentity request, including temporary AWS credentials that can be used to make AWS requests.

    • Credentials (dict) --

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

      • AccessKeyId (string) --

        The access key ID that identifies the temporary security credentials.

      • SecretAccessKey (string) --

        The secret access key that can be used to sign requests.

      • SessionToken (string) --

        The token that users must pass to the service API to use the temporary credentials.

      • Expiration (datetime) --

        The date on which the current credentials expire.

    • SubjectFromWebIdentityToken (string) --

      The unique user identifier that is returned by the identity provider. This identifier is associated with the WebIdentityToken that was submitted with the AssumeRoleWithWebIdentity call. The identifier is typically unique to the user and the application that acquired the WebIdentityToken (pairwise identifier). For OpenID Connect ID tokens, this field contains the value returned by the identity provider as the token's sub (Subject) claim.

    • AssumedRoleUser (dict) --

      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.

      • AssumedRoleId (string) --

        A unique identifier that contains the role ID and the role session name of the role that is being assumed. The role ID is generated by AWS when the role is created.

      • Arn (string) --

        The ARN of the temporary security credentials that are returned from the AssumeRole action. For more information about ARNs and how to use them in policies, see Identifiers for IAM Entities in Using IAM.

    • PackedPolicySize (integer) --

      A percentage value that indicates the size of the policy in packed form. The service rejects any policy with a packed size greater than 100 percent, which means the policy exceeded the allowed space.

    • Provider (string) --

      The issuing authority of the web identity token presented. For OpenID Connect ID Tokens this contains the value of the iss field. For OAuth 2.0 access tokens, this contains the value of the ProviderId parameter that was passed in the AssumeRoleWithWebIdentity request.

    • Audience (string) --

      The intended audience (also known as client ID) of the web identity token. This is traditionally the client identifier issued to the application that requested the web identity token.

AssumeRoleWithSAML (new) Link ¶

Returns a set of temporary security credentials for users who have been authenticated via a SAML authentication response. This operation provides a mechanism for tying an enterprise identity store or directory to role-based AWS access without user-specific credentials or configuration.

The temporary security credentials returned by this operation consist of an access key ID, a secret access key, and a security token. Applications can use these temporary security credentials to sign calls to AWS services. The credentials are valid for the duration that you specified when calling AssumeRoleWithSAML, which can be up to 3600 seconds (1 hour) or until the time specified in the SAML authentication response's SessionNotOnOrAfter value, whichever is shorter.

Optionally, you can pass an IAM access policy to this operation. If you choose not to pass a policy, the temporary security credentials that are returned by the operation have the permissions that are defined in the access policy of the role that is being assumed. If you pass a policy to this operation, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRoleWithSAML in Using Temporary Security Credentials.

Before your application can call AssumeRoleWithSAML, you must configure your SAML identity provider (IdP) to issue the claims required by AWS. Additionally, you must use AWS Identity and Access Management (IAM) to create a SAML provider entity in your AWS account that represents your identity provider, and create an IAM role that specifies this SAML provider in its trust policy.

Calling AssumeRoleWithSAML does not require the use of AWS security credentials. The identity of the caller is validated by using keys in the metadata document that is uploaded for the SAML provider entity for your identity provider.

For more information, see the following resources:

Request Syntax

client.assume_role_with_saml(
    RoleArn='string',
    PrincipalArn='string',
    SAMLAssertion='string',
    Policy='string',
    DurationSeconds=123
)
type RoleArn:

string

param RoleArn:

[REQUIRED]

The Amazon Resource Name (ARN) of the role that the caller is assuming.

type PrincipalArn:

string

param PrincipalArn:

[REQUIRED]

The Amazon Resource Name (ARN) of the SAML provider in IAM that describes the IdP.

type SAMLAssertion:

string

param SAMLAssertion:

[REQUIRED]

The base-64 encoded SAML authentication response provided by the IdP.

For more information, see Configuring a Relying Party and Adding Claims in the Using IAM guide.

type Policy:

string

param Policy:

An IAM policy in JSON format.

The policy parameter is optional. If you pass a policy, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRoleWithSAML in Using Temporary Security Credentials.

type DurationSeconds:

integer

param DurationSeconds:

The duration, in seconds, of the role session. The value can range from 900 seconds (15 minutes) to 3600 seconds (1 hour). By default, the value is set to 3600 seconds. An expiration can also be specified in the SAML authentication response's SessionNotOnOrAfter value. The actual expiration time is whichever value is shorter.

rtype:

dict

returns:

Response Syntax

{
    'Credentials': {
        'AccessKeyId': 'string',
        'SecretAccessKey': 'string',
        'SessionToken': 'string',
        'Expiration': datetime(2015, 1, 1)
    },
    'AssumedRoleUser': {
        'AssumedRoleId': 'string',
        'Arn': 'string'
    },
    'PackedPolicySize': 123,
    'Subject': 'string',
    'SubjectType': 'string',
    'Issuer': 'string',
    'Audience': 'string',
    'NameQualifier': 'string'
}

Response Structure

  • (dict) --

    Contains the response to a successful AssumeRoleWithSAML request, including temporary AWS credentials that can be used to make AWS requests.

    • Credentials (dict) --

      AWS credentials for API authentication.

      • AccessKeyId (string) --

        The access key ID that identifies the temporary security credentials.

      • SecretAccessKey (string) --

        The secret access key that can be used to sign requests.

      • SessionToken (string) --

        The token that users must pass to the service API to use the temporary credentials.

      • Expiration (datetime) --

        The date on which the current credentials expire.

    • AssumedRoleUser (dict) --

      The identifiers for the temporary security credentials that the operation returns.

      • AssumedRoleId (string) --

        A unique identifier that contains the role ID and the role session name of the role that is being assumed. The role ID is generated by AWS when the role is created.

      • Arn (string) --

        The ARN of the temporary security credentials that are returned from the AssumeRole action. For more information about ARNs and how to use them in policies, see Identifiers for IAM Entities in Using IAM.

    • PackedPolicySize (integer) --

      A percentage value that indicates the size of the policy in packed form. The service rejects any policy with a packed size greater than 100 percent, which means the policy exceeded the allowed space.

    • Subject (string) --

      The value of the NameID element in the Subject element of the SAML assertion.

    • SubjectType (string) --

      The format of the name ID, as defined by the Format attribute in the NameID element of the SAML assertion. Typical examples of the format are transient or persistent.

      If the format includes the prefix urn:oasis:names:tc:SAML:2.0:nameid-format, that prefix is removed. For example, urn:oasis:names:tc:SAML:2.0:nameid-format:transient is returned as transient. If the format includes any other prefix, the format is returned with no modifications.

    • Issuer (string) --

      The value of the Issuer element of the SAML assertion.

    • Audience (string) --

      The value of the Recipient attribute of the SubjectConfirmationData element of the SAML assertion.

    • NameQualifier (string) --

      A hash value based on the concatenation of the Issuer response value, the AWS account ID, and the friendly name (the last part of the ARN) of the SAML provider in IAM. The combination of NameQualifier and Subject can be used to uniquely identify a federated user.

      The following pseudocode shows how the hash value is calculated:

      BASE64 ( SHA1 ( "https://example.com/saml" + "123456789012" + "/MySAMLIdP" ) )

GetFederationToken (new) Link ¶

Returns a set of temporary security credentials (consisting of an access key ID, a secret access key, and a security token) for a federated user. A typical use is in a proxy application that gets temporary security credentials on behalf of distributed applications inside a corporate network. Because you must call the GetFederationToken action using the long-term security credentials of an IAM user, this call is appropriate in contexts where those credentials can be safely stored, usually in a server-based application.

The GetFederationToken action must be called by using the long-term AWS security credentials of an IAM user. You can also call GetFederationToken using the security credentials of an AWS account (root), but this is not recommended. Instead, we recommend that you create an IAM user for the purpose of the proxy application and then attach a policy to the IAM user that limits federated users to only the actions and resources they need access to. For more information, see IAM Best Practices in Using IAM.

The temporary security credentials that are obtained by using the long-term credentials of an IAM user are valid for the specified duration, between 900 seconds (15 minutes) and 129600 seconds (36 hours). Temporary credentials that are obtained by using AWS account (root) credentials have a maximum duration of 3600 seconds (1 hour)

Permissions

The permissions for the temporary security credentials returned by GetFederationToken are determined by a combination of the following:

  • The policy or policies that are attached to the IAM user whose credentials are used to call GetFederationToken.

  • The policy that is passed as a parameter in the call.

The passed policy is attached to the temporary security credentials that result from the GetFederationToken API call--that is, to the federated user. When the federated user makes an AWS request, AWS evaluates the policy attached to the federated user in combination with the policy or policies attached to the IAM user whose credentials were used to call GetFederationToken. AWS allows the federated user's request only when both the federated user and the IAM user are explicitly allowed to perform the requested action. The passed policy cannot grant more permissions than those that are defined in the IAM user policy.

A typical use case is that the permissions of the IAM user whose credentials are used to call GetFederationToken are designed to allow access to all the actions and resources that any federated user will need. Then, for individual users, you pass a policy to the operation that scopes down the permissions to a level that's appropriate to that individual user, using a policy that allows only a subset of permissions that are granted to the IAM user.

If you do not pass a policy, the resulting temporary security credentials have no effective permissions. The only exception is when the temporary security credentials are used to access a resource that has a resource-based policy that specifically allows the federated user to access the resource.

For more information about how permissions work, see Permissions for GetFederationToken in Using Temporary Security Credentials. For information about using GetFederationToken to create temporary security credentials, see Creating Temporary Credentials to Enable Access for Federated Users in Using Temporary Security Credentials.

Request Syntax

client.get_federation_token(
    Name='string',
    Policy='string',
    DurationSeconds=123
)
type Name:

string

param Name:

[REQUIRED]

The name of the federated user. The name is used as an identifier for the temporary security credentials (such as Bob). For example, you can reference the federated user name in a resource-based policy, such as in an Amazon S3 bucket policy.

type Policy:

string

param Policy:

An IAM policy in JSON format that is passed with the GetFederationToken call and evaluated along with the policy or policies that are attached to the IAM user whose credentials are used to call GetFederationToken. The passed policy is used to scope down the permissions that are available to the IAM user, by allowing only a subset of the permissions that are granted to the IAM user. The passed policy cannot grant more permissions than those granted to the IAM user. The final permissions for the federated user are the most restrictive set based on the intersection of the passed policy and the IAM user policy.

If you do not pass a policy, the resulting temporary security credentials have no effective permissions. The only exception is when the temporary security credentials are used to access a resource that has a resource-based policy that specifically allows the federated user to access the resource.

For more information about how permissions work, see Permissions for GetFederationToken in Using Temporary Security Credentials.

type DurationSeconds:

integer

param DurationSeconds:

The duration, in seconds, that the session should last. Acceptable durations for federation sessions range from 900 seconds (15 minutes) to 129600 seconds (36 hours), with 43200 seconds (12 hours) as the default. Sessions obtained using AWS account (root) credentials are restricted to a maximum of 3600 seconds (one hour). If the specified duration is longer than one hour, the session obtained by using AWS account (root) credentials defaults to one hour.

rtype:

dict

returns:

Response Syntax

{
    'Credentials': {
        'AccessKeyId': 'string',
        'SecretAccessKey': 'string',
        'SessionToken': 'string',
        'Expiration': datetime(2015, 1, 1)
    },
    'FederatedUser': {
        'FederatedUserId': 'string',
        'Arn': 'string'
    },
    'PackedPolicySize': 123
}

Response Structure

  • (dict) --

    Contains the response to a successful GetFederationToken request, including temporary AWS credentials that can be used to make AWS requests.

    • Credentials (dict) --

      Credentials for the service API authentication.

      • AccessKeyId (string) --

        The access key ID that identifies the temporary security credentials.

      • SecretAccessKey (string) --

        The secret access key that can be used to sign requests.

      • SessionToken (string) --

        The token that users must pass to the service API to use the temporary credentials.

      • Expiration (datetime) --

        The date on which the current credentials expire.

    • FederatedUser (dict) --

      Identifiers for the federated user associated with the credentials (such as arn:aws:sts::123456789012:federated-user/Bob or 123456789012:Bob). You can use the federated user's ARN in your resource-based policies, such as an Amazon S3 bucket policy.

      • FederatedUserId (string) --

        The string that identifies the federated user associated with the credentials, similar to the unique ID of an IAM user.

      • Arn (string) --

        The ARN that specifies the federated user that is associated with the credentials. For more information about ARNs and how to use them in policies, see Identifiers for IAM Entities in Using IAM.

    • PackedPolicySize (integer) --

      A percentage value indicating the size of the policy in packed form. The service rejects policies for which the packed size is greater than 100 percent of the allowed value.

AssumeRole (new) Link ¶

Returns a set of temporary security credentials (consisting of an access key ID, a secret access key, and a security token) that you can use to access AWS resources that you might not normally have access to. Typically, you use AssumeRole for cross-account access or federation.

Important: You cannot call AssumeRole by using AWS account credentials; access will be denied. You must use IAM user credentials or temporary security credentials to call AssumeRole.

For cross-account access, imagine that you own multiple accounts and need to access resources in each account. You could create long-term credentials in each account to access those resources. However, managing all those credentials and remembering which one can access which account can be time consuming. Instead, you can create one set of long-term credentials in one account and then use temporary security credentials to access all the other accounts by assuming roles in those accounts. For more information about roles, see Roles in Using IAM.

For federation, you can, for example, grant single sign-on access to the AWS Management Console. If you already have an identity and authentication system in your corporate network, you don't have to recreate user identities in AWS in order to grant those user identities access to AWS. Instead, after a user has been authenticated, you call AssumeRole (and specify the role with the appropriate permissions) to get temporary security credentials for that user. With those temporary security credentials, you construct a sign-in URL that users can use to access the console. For more information, see Scenarios for Granting Temporary Access in Using Temporary Security Credentials.

The temporary security credentials are valid for the duration that you specified when calling AssumeRole, which can be from 900 seconds (15 minutes) to 3600 seconds (1 hour). The default is 1 hour.

Optionally, you can pass an IAM access policy to this operation. If you choose not to pass a policy, the temporary security credentials that are returned by the operation have the permissions that are defined in the access policy of the role that is being assumed. If you pass a policy to this operation, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRole in Using Temporary Security Credentials.

To assume a role, your AWS account must be trusted by the role. The trust relationship is defined in the role's trust policy when the role is created. You must also have a policy that allows you to call sts:AssumeRole.

Using MFA with AssumeRole

You can optionally include multi-factor authentication (MFA) information when you call AssumeRole. This is useful for cross-account scenarios in which you want to make sure that the user who is assuming the role has been authenticated using an AWS 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": {"Null": {"aws:MultiFactorAuthAge": false}}

For more information, see Configuring MFA-Protected API Access in the Using IAM 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 devices produces.

Request Syntax

client.assume_role(
    RoleArn='string',
    RoleSessionName='string',
    Policy='string',
    DurationSeconds=123,
    ExternalId='string',
    SerialNumber='string',
    TokenCode='string'
)
type RoleArn:

string

param RoleArn:

[REQUIRED]

The Amazon Resource Name (ARN) of the role that the caller is assuming.

type RoleSessionName:

string

param RoleSessionName:

[REQUIRED]

An identifier for the assumed role session. The session name is included as part of the AssumedRoleUser.

type Policy:

string

param Policy:

An IAM policy in JSON format.

The policy parameter is optional. If you pass a policy, the temporary security credentials that are returned by the operation have the permissions that are allowed by both the access policy of the role that is being assumed, and the policy that you pass. This gives you a way to further restrict the permissions for the resulting temporary security credentials. You cannot use the passed policy to grant permissions that are in excess of those allowed by the access policy of the role that is being assumed. For more information, see Permissions for AssumeRole in Using Temporary Security Credentials.

type DurationSeconds:

integer

param DurationSeconds:

The duration, in seconds, of the role session. The value can range from 900 seconds (15 minutes) to 3600 seconds (1 hour). By default, the value is set to 3600 seconds.

type ExternalId:

string

param ExternalId:

A unique identifier that is used by third parties to assume a role in their customers' accounts. For each role that the third party can assume, they should instruct their customers to create a role with the external ID that the third party generated. Each time the third party assumes the role, they must pass the customer's external ID. The external ID is useful in order to help third parties bind a role to the customer who created it. For more information about the external ID, see About the External ID in Using Temporary Security Credentials.

type SerialNumber:

string

param 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).

type TokenCode:

string

param TokenCode:

The value provided by the MFA device, if the trust policy of the role being assumed requires MFA (that is, 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.

rtype:

dict

returns:

Response Syntax

{
    'Credentials': {
        'AccessKeyId': 'string',
        'SecretAccessKey': 'string',
        'SessionToken': 'string',
        'Expiration': datetime(2015, 1, 1)
    },
    'AssumedRoleUser': {
        'AssumedRoleId': 'string',
        'Arn': 'string'
    },
    'PackedPolicySize': 123
}

Response Structure

  • (dict) --

    Contains the response to a successful AssumeRole request, including temporary AWS credentials that can be used to make AWS requests.

    • Credentials (dict) --

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

      • AccessKeyId (string) --

        The access key ID that identifies the temporary security credentials.

      • SecretAccessKey (string) --

        The secret access key that can be used to sign requests.

      • SessionToken (string) --

        The token that users must pass to the service API to use the temporary credentials.

      • Expiration (datetime) --

        The date on which the current credentials expire.

    • AssumedRoleUser (dict) --

      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.

      • AssumedRoleId (string) --

        A unique identifier that contains the role ID and the role session name of the role that is being assumed. The role ID is generated by AWS when the role is created.

      • Arn (string) --

        The ARN of the temporary security credentials that are returned from the AssumeRole action. For more information about ARNs and how to use them in policies, see Identifiers for IAM Entities in Using IAM.

    • PackedPolicySize (integer) --

      A percentage value that indicates the size of the policy in packed form. The service rejects any policy with a packed size greater than 100 percent, which means the policy exceeded the allowed space.