Hi Jeff,

You may modify this plugin using Integration Studio. Add a new field in the S3_AuthenticationInfo Structure for the session token.

After you publish it, modify the source code.
First thing you need to do is to install the needed package using Nuget Manager and install awssdk.securitytoken

Then, modify the AmazonS3.cs Login function to receive and set the sessiontoken parameter.

public void Login(string pInAwsAccessKeyId, string pInAwsSecretAccessKey, string pInAwsSessionKey, string region)

        {

            //Create credential object

            _amazonS3Credentials = new AmazonS3Credentials();

            _amazonS3Credentials.AwsAccessKeyId = pInAwsAccessKeyId;

            _amazonS3Credentials.AwsSecretAccessKey = pInAwsSecretAccessKey;

            _amazonS3Credentials.AwsSessionKey = pInAwsSessionKey;

            try

            {

                _amazonS3Credentials.AwsRegion = (RegionEndpoint)typeof(RegionEndpoint).GetField(region).GetValue(null); ;

            }

            catch (Exception)

            {

                throw new ArgumentException(string.Format("Invalid region {0}", region));

            }

        }

Then Modify the private function GetClient()

private AmazonS3Client GetClient()

        {

            //Check c

            if (_amazonS3Credentials == null)

            {

                throw (new ArgumentException("Amazon S3 credentials are not properly defined."));

            }

            //Create amazon client

            AmazonS3Config amazonS3Config = new AmazonS3Config();

            amazonS3Config.ServiceURL = _amazonS3Credentials.AwsServiceUrl;

            amazonS3Config.RegionEndpoint = _amazonS3Credentials.AwsRegion;

            SessionAWSCredentials tempCredentials = new SessionAWSCredentials(_amazonS3Credentials.AwsAccessKeyId, _amazonS3Credentials.AwsSecretAccessKey, _amazonS3Credentials.AwsSessionKey); 

            return (new AmazonS3Client(tempCredentials, amazonS3Config));

        }

I have based it in the AWS documentation you have given.

Hope this helps