DecodeAuthorizationMessage - AWS Security Token Service


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 operation that he or she has requested, the request returns a Client.UnauthorizedOperation response (an HTTP 403 response). Some AWS operations additionally return an encoded message that can provide details about this authorization failure.


Only certain AWS operations return an encoded authorization message. The documentation for an individual operation indicates whether that operation returns an encoded message in addition to returning an HTTP code.

The message is encoded because the details of the authorization status can contain privileged information that the user who requested the operation should not see. To decode an authorization status message, a user must be granted permissions through 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 the IAM User Guide.

  • 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 Parameters

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


The encoded message that was returned with the response.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 10240.

Required: Yes

Response Elements

The following element is returned by the service.


The API returns a response with the decoded message.

Type: String


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


The error returned if the message passed to DecodeAuthorizationMessage was invalid. This can happen if the token contains invalid characters, such as linebreaks.

HTTP Status Code: 400



The following code provides an example of a DecodeAuthorizationMessage policy:

{ "Version": "2012-10-17", "Statement": [ { "Sid": "decodepolicy", "Effect": "Allow", "Action": "sts:DecodeAuthorizationMessage", "Resource": "*" } ] }


This example illustrates one usage of DecodeAuthorizationMessage.

Sample Request

POST / HTTP/1.1 Content-Type: application/x-www-form-urlencoded; charset=utf-8 Host: Content-Length: 1148 Expect: 100-continue Connection: Keep-Alive Action=DecodeAuthorizationMessage &EncodedMessage=<encoded-message> &Version=2011-06-15 &AUTHPARAMS

Sample Response

<?xml version="1.0" encoding="UTF-8"?> <DecodeAuthorizationMessageResponse xmlns=""> <requestId>6624a9ca-cd25-4f50-b2a5-7ba65bf07453</requestId> <DecodedMessage> { "allowed": "false", "explicitDeny": "false", "matchedStatements": "", "failures": "", "context": { "principal": { "id": "AIDACKCEVSQ6C2EXAMPLE", "name": "Bob", "arn": "arn:aws:iam::123456789012:user/Bob" }, "action": "ec2:StopInstances", "resource": "arn:aws:ec2:us-east-1:123456789012:instance/i-dd01c9bd", "conditions": [ { "item": { "key": "ec2:Tenancy", "values": ["default"] }, { "item": { "key": "ec2:ResourceTag/elasticbeanstalk:environment-name", "values": ["Default-Environment"] } }, (Additional items ...) ] } } </DecodedMessage> </DecodeAuthorizationMessageResponse>

See Also

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