Use AssumeRole with an Amazon SDK or command line tool

using System;
using System.Threading.Tasks;
using Amazon;
using Amazon.SecurityToken;
using Amazon.SecurityToken.Model;

namespace AssumeRoleExample
{
    class AssumeRole
    {
        /// <summary>
        /// This example shows how to use the AWS Security Token
        /// Service (AWS STS) to assume an IAM role.
        ///
        /// NOTE: It is important that the role that will be assumed has a
        /// trust relationship with the account that will assume the role.
        ///
        /// Before you run the example, you need to create the role you want to
        /// assume and have it trust the IAM account that will assume that role.
        ///
        /// See https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create.html
        /// for help in working with roles.
        /// </summary>

        private static readonly RegionEndpoint REGION = RegionEndpoint.USWest2;

        static async Task Main()
        {
            // Create the SecurityToken client and then display the identity of the
            // default user.
            var roleArnToAssume = "arn:aws:iam::123456789012:role/testAssumeRole";

            var client = new Amazon.SecurityToken.AmazonSecurityTokenServiceClient(REGION);

            // Get and display the information about the identity of the default user.
            var callerIdRequest = new GetCallerIdentityRequest();
            var caller = await client.GetCallerIdentityAsync(callerIdRequest);
            Console.WriteLine($"Original Caller: {caller.Arn}");

            // Create the request to use with the AssumeRoleAsync call.
            var assumeRoleReq = new AssumeRoleRequest()
            {
                DurationSeconds = 1600,
                RoleSessionName = "Session1",
                RoleArn = roleArnToAssume
            };

            var assumeRoleRes = await client.AssumeRoleAsync(assumeRoleReq);

            // Now create a new client based on the credentials of the caller assuming the role.
            var client2 = new AmazonSecurityTokenServiceClient(credentials: assumeRoleRes.Credentials);

            // Get and display information about the caller that has assumed the defined role.
            var caller2 = await client2.GetCallerIdentityAsync(callerIdRequest);
            Console.WriteLine($"AssumedRole Caller: {caller2.Arn}");
        }
    }
}

###############################################################################
# function iecho
#
# This function enables the script to display the specified text only if
# the global variable $VERBOSE is set to true.
###############################################################################
function iecho() {
  if [[ $VERBOSE == true ]]; then
    echo "$@"
  fi
}

###############################################################################
# function errecho
#
# This function outputs everything sent to it to STDERR (standard error output).
###############################################################################
function errecho() {
  printf "%s\n" "$*" 1>&2
}

###############################################################################
# function sts_assume_role
#
# This function assumes a role in the AWS account and returns the temporary
#  credentials.
#
# Parameters:
#       -n role_session_name -- The name of the session.
#       -r role_arn -- The ARN of the role to assume.
#
# Returns:
#       [access_key_id, secret_access_key, session_token]
#     And:
#       0 - If successful.
#       1 - If an error occurred.
###############################################################################
function sts_assume_role() {
  local role_session_name role_arn response
  local option OPTARG # Required to use getopts command in a function.

  # bashsupport disable=BP5008
  function usage() {
    echo "function sts_assume_role"
    echo "Assumes a role in the AWS account and returns the temporary credentials:"
    echo "  -n role_session_name -- The name of the session."
    echo "  -r role_arn -- The ARN of the role to assume."
    echo ""
  }

  while getopts n:r:h option; do
    case "${option}" in
      n) role_session_name=${OPTARG} ;;
      r) role_arn=${OPTARG} ;;
      h)
        usage
        return 0
        ;;
      \?)
        ech o"Invalid parameter"
        usage
        return 1
        ;;
    esac
  done

  response=$(aws sts assume-role \
    --role-session-name "$role_session_name" \
    --role-arn "$role_arn" \
    --output text \
    --query "Credentials.[AccessKeyId, SecretAccessKey, SessionToken]")

  local error_code=${?}

  if [[ $error_code -ne 0 ]]; then
    aws_cli_error_log $error_code
    errecho "ERROR: AWS reports create-role operation failed.\n$response"
    return 1
  fi

  echo "$response"

  return 0
}

bool AwsDoc::STS::assumeRole(const Aws::String &roleArn,
                             const Aws::String &roleSessionName,
                             const Aws::String &externalId,
                             Aws::Auth::AWSCredentials &credentials,
                             const Aws::Client::ClientConfiguration &clientConfig) {
    Aws::STS::STSClient sts(clientConfig);
    Aws::STS::Model::AssumeRoleRequest sts_req;

    sts_req.SetRoleArn(roleArn);
    sts_req.SetRoleSessionName(roleSessionName);
    sts_req.SetExternalId(externalId);

    const Aws::STS::Model::AssumeRoleOutcome outcome = sts.AssumeRole(sts_req);

    if (!outcome.IsSuccess()) {
        std::cerr << "Error assuming IAM role. " <<
                  outcome.GetError().GetMessage() << std::endl;
    }
    else {
        std::cout << "Credentials successfully retrieved." << std::endl;
        const Aws::STS::Model::AssumeRoleResult result = outcome.GetResult();
        const Aws::STS::Model::Credentials &temp_credentials = result.GetCredentials();

        // Store temporary credentials in return argument.
        // Note: The credentials object returned by assumeRole differs
        // from the AWSCredentials object used in most situations.
        credentials.SetAWSAccessKeyId(temp_credentials.GetAccessKeyId());
        credentials.SetAWSSecretKey(temp_credentials.GetSecretAccessKey());
        credentials.SetSessionToken(temp_credentials.GetSessionToken());
    }

    return outcome.IsSuccess();
}

To assume a role

The following assume-role command retrieves a set of short-term credentials for the IAM role s3-access-example.

aws sts assume-role \
    --role-arn arn:aws:iam::123456789012:role/xaccounts3access \
    --role-session-name s3-access-example

Output:

{
    "AssumedRoleUser": {
        "AssumedRoleId": "AROA3XFRBF535PLBIFPI4:s3-access-example",
        "Arn": "arn:aws:sts::123456789012:assumed-role/xaccounts3access/s3-access-example"
    },
    "Credentials": {
        "SecretAccessKey": "9drTJvcXLB89EXAMPLELB8923FB892xMFI",
        "SessionToken": "AQoXdzELDDY//////////wEaoAK1wvxJY12r2IrDFT2IvAzTCn3zHoZ7YNtpiQLF0MqZye/qwjzP2iEXAMPLEbw/m3hsj8VBTkPORGvr9jM5sgP+w9IZWZnU+LWhmg+a5fDi2oTGUYcdg9uexQ4mtCHIHfi4citgqZTgco40Yqr4lIlo4V2b2Dyauk0eYFNebHtYlFVgAUj+7Indz3LU0aTWk1WKIjHmmMCIoTkyYp/k7kUG7moeEYKSitwQIi6Gjn+nyzM+PtoA3685ixzv0R7i5rjQi0YE0lf1oeie3bDiNHncmzosRM6SFiPzSvp6h/32xQuZsjcypmwsPSDtTPYcs0+YN/8BRi2/IcrxSpnWEXAMPLEXSDFTAQAM6Dl9zR0tXoybnlrZIwMLlMi1Kcgo5OytwU=",
        "Expiration": "2016-03-15T00:05:07Z",
        "AccessKeyId": "ASIAJEXAMPLEXEG2JICEA"
    }
}

The output of the command contains an access key, secret key, and session token that you can use to authenticate to Amazon.

For Amazon CLI use, you can set up a named profile associated with a role. When you use the profile, the Amazon CLI will call assume-role and manage credentials for you. For more information, see Use an IAM role in the Amazon CLI in the Amazon CLI User Guide.

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.sts.StsClient;
import software.amazon.awssdk.services.sts.model.AssumeRoleRequest;
import software.amazon.awssdk.services.sts.model.StsException;
import software.amazon.awssdk.services.sts.model.AssumeRoleResponse;
import software.amazon.awssdk.services.sts.model.Credentials;
import java.time.Instant;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.FormatStyle;
import java.util.Locale;

/**
 * To make this code example work, create a Role that you want to assume.
 * Then define a Trust Relationship in the AWS Console. You can use this as an
 * example:
 *
 * {
 * "Version": "2012-10-17",
 * "Statement": [
 * {
 * "Effect": "Allow",
 * "Principal": {
 * "AWS": "<Specify the ARN of your IAM user you are using in this code
 * example>"
 * },
 * "Action": "sts:AssumeRole"
 * }
 * ]
 * }
 *
 * For more information, see "Editing the Trust Relationship for an Existing
 * Role" in the AWS Directory Service guide.
 *
 * Also, set up your development environment, including your credentials.
 *
 * For information, see this documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */
public class AssumeRole {
    public static void main(String[] args) {
        final String usage = """

                Usage:
                    <roleArn> <roleSessionName>\s

                Where:
                    roleArn - The Amazon Resource Name (ARN) of the role to assume (for example, rn:aws:iam::000008047983:role/s3role).\s
                    roleSessionName - An identifier for the assumed role session (for example, mysession).\s
                """;

        if (args.length != 2) {
            System.out.println(usage);
            System.exit(1);
        }

        String roleArn = args[0];
        String roleSessionName = args[1];
        Region region = Region.US_EAST_1;
        StsClient stsClient = StsClient.builder()
                .region(region)
                .build();

        assumeGivenRole(stsClient, roleArn, roleSessionName);
        stsClient.close();
    }

    public static void assumeGivenRole(StsClient stsClient, String roleArn, String roleSessionName) {
        try {
            AssumeRoleRequest roleRequest = AssumeRoleRequest.builder()
                    .roleArn(roleArn)
                    .roleSessionName(roleSessionName)
                    .build();

            AssumeRoleResponse roleResponse = stsClient.assumeRole(roleRequest);
            Credentials myCreds = roleResponse.credentials();

            // Display the time when the temp creds expire.
            Instant exTime = myCreds.expiration();
            String tokenInfo = myCreds.sessionToken();

            // Convert the Instant to readable date.
            DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT)
                    .withLocale(Locale.US)
                    .withZone(ZoneId.systemDefault());

            formatter.format(exTime);
            System.out.println("The token " + tokenInfo + "  expires on " + exTime);

        } catch (StsException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
    }
}

Create the client.

import { STSClient } from "@aws-sdk/client-sts";
// Set the AWS Region.
const REGION = "us-east-1";
// Create an AWS STS service client object.
export const client = new STSClient({ region: REGION });

Assume the IAM role.

import { AssumeRoleCommand } from "@aws-sdk/client-sts";

import { client } from "../libs/client.js";

export const main = async () => {
  try {
    // Returns a set of temporary security credentials that you can use to
    // access Amazon Web Services resources that you might not normally
    // have access to.
    const command = new AssumeRoleCommand({
      // The Amazon Resource Name (ARN) of the role to assume.
      RoleArn: "ROLE_ARN",
      // An identifier for the assumed role session.
      RoleSessionName: "session1",
      // 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.
      DurationSeconds: 900,
    });
    const response = await client.send(command);
    console.log(response);
  } catch (err) {
    console.error(err);
  }
};

// Load the AWS SDK for Node.js
const AWS = require("aws-sdk");
// Set the region
AWS.config.update({ region: "REGION" });

var roleToAssume = {
  RoleArn: "arn:aws:iam::123456789012:role/RoleName",
  RoleSessionName: "session1",
  DurationSeconds: 900,
};
var roleCreds;

// Create the STS service object
var sts = new AWS.STS({ apiVersion: "2011-06-15" });

//Assume Role
sts.assumeRole(roleToAssume, function (err, data) {
  if (err) console.log(err, err.stack);
  else {
    roleCreds = {
      accessKeyId: data.Credentials.AccessKeyId,
      secretAccessKey: data.Credentials.SecretAccessKey,
      sessionToken: data.Credentials.SessionToken,
    };
    stsGetCallerIdentity(roleCreds);
  }
});

//Get Arn of current identity
function stsGetCallerIdentity(creds) {
  var stsParams = { credentials: creds };
  // Create STS service object
  var sts = new AWS.STS(stsParams);

  sts.getCallerIdentity({}, function (err, data) {
    if (err) {
      console.log(err, err.stack);
    } else {
      console.log(data.Arn);
    }
  });
}

Example 1: Returns a set of temporary credentials (access key, secret key and session token) that can be used for one hour to access Amazon resources that the requesting user might not normally have access to. The returned credentials have the permissions that are allowed by the access policy of the role being assumed and the policy that was supplied (you cannot use the supplied policy to grant permissions in excess of those defined by the access policy of the role being assumed).

Use-STSRole -RoleSessionName "Bob" -RoleArn "arn:aws:iam::123456789012:role/demo" -Policy "...JSON policy..." -DurationInSeconds 3600

Example 2: Returns a set of temporary credentials, valid for one hour, that have the same permissions that are defined in the access policy of the role being assumed.

Use-STSRole -RoleSessionName "Bob" -RoleArn "arn:aws:iam::123456789012:role/demo" -DurationInSeconds 3600

Example 3: Returns a set of temporary credentials supplying the serial number and generated token from an MFA associated with the user credentials used to execute the cmdlet.

Use-STSRole -RoleSessionName "Bob" -RoleArn "arn:aws:iam::123456789012:role/demo" -DurationInSeconds 3600 -SerialNumber "GAHT12345678" -TokenCode "123456"

Example 4: Returns a set of temporary credentials that have assumed a role defined in a customer account. For each role that the third party can assume, the customer account must create a role using an identifier that must be passed in the -ExternalId parameter each time the role is assumed.

Use-STSRole -RoleSessionName "Bob" -RoleArn "arn:aws:iam::123456789012:role/demo" -DurationInSeconds 3600 -ExternalId "ABC123"

Assume an IAM role that requires an MFA token and use temporary credentials to list Amazon S3 buckets for the account.

def list_buckets_from_assumed_role_with_mfa(
    assume_role_arn, session_name, mfa_serial_number, mfa_totp, sts_client
):
    """
    Assumes a role from another account and uses the temporary credentials from
    that role to list the Amazon S3 buckets that are owned by the other account.
    Requires an MFA device serial number and token.

    The assumed role must grant permission to list the buckets in the other account.

    :param assume_role_arn: The Amazon Resource Name (ARN) of the role that
                            grants access to list the other account's buckets.
    :param session_name: The name of the STS session.
    :param mfa_serial_number: The serial number of the MFA device. For a virtual MFA
                              device, this is an ARN.
    :param mfa_totp: A time-based, one-time password issued by the MFA device.
    :param sts_client: A Boto3 STS instance that has permission to assume the role.
    """
    response = sts_client.assume_role(
        RoleArn=assume_role_arn,
        RoleSessionName=session_name,
        SerialNumber=mfa_serial_number,
        TokenCode=mfa_totp,
    )
    temp_credentials = response["Credentials"]
    print(f"Assumed role {assume_role_arn} and got temporary credentials.")

    s3_resource = boto3.resource(
        "s3",
        aws_access_key_id=temp_credentials["AccessKeyId"],
        aws_secret_access_key=temp_credentials["SecretAccessKey"],
        aws_session_token=temp_credentials["SessionToken"],
    )

    print(f"Listing buckets for the assumed role's account:")
    for bucket in s3_resource.buckets.all():
        print(bucket.name)

  # Creates an AWS Security Token Service (AWS STS) client with specified credentials.
  # This is separated into a factory function so that it can be mocked for unit testing.
  #
  # @param key_id [String] The ID of the access key used by the STS client.
  # @param key_secret [String] The secret part of the access key used by the STS client.
  def create_sts_client(key_id, key_secret)
    Aws::STS::Client.new(access_key_id: key_id, secret_access_key: key_secret)
  end

  # Gets temporary credentials that can be used to assume a role.
  #
  # @param role_arn [String] The ARN of the role that is assumed when these credentials
  #                          are used.
  # @param sts_client [AWS::STS::Client] An AWS STS client.
  # @return [Aws::AssumeRoleCredentials] The credentials that can be used to assume the role.
  def assume_role(role_arn, sts_client)
    credentials = Aws::AssumeRoleCredentials.new(
      client: sts_client,
      role_arn: role_arn,
      role_session_name: "create-use-assume-role-scenario"
    )
    @logger.info("Assumed role '#{role_arn}', got temporary credentials.")
    credentials
  end

async fn assume_role(config: &SdkConfig, role_name: String, session_name: Option<String>) {
    let provider = aws_config::sts::AssumeRoleProvider::builder(role_name)
        .session_name(session_name.unwrap_or("rust_sdk_example_session".into()))
        .configure(config)
        .build()
        .await;

    let local_config = aws_config::from_env()
        .credentials_provider(provider)
        .load()
        .await;
    let client = Client::new(&local_config);
    let req = client.get_caller_identity();
    let resp = req.send().await;
    match resp {
        Ok(e) => {
            println!("UserID :               {}", e.user_id().unwrap_or_default());
            println!("Account:               {}", e.account().unwrap_or_default());
            println!("Arn    :               {}", e.arn().unwrap_or_default());
        }
        Err(e) => println!("{:?}", e),
    }
}

    public func assumeRole(role: IAMClientTypes.Role, sessionName: String)
                    async throws -> STSClientTypes.Credentials {
        let input = AssumeRoleInput(
            roleArn: role.arn,
            roleSessionName: sessionName
        )
        do {
            let output = try await stsClient.assumeRole(input: input)

            guard let credentials = output.credentials else {
                throw ServiceHandlerError.authError
            }

            return credentials
        } catch {
            throw error
        }
    }