How enable access to AWS STS AssumeRole - node.js

Question

I am getting an error when calling to assume role method of STS. It says that the user is not authorized to perform sts:AsumeRole on resource xxx.
I did the following:
I created a role to access to S3 bucket.
I ran a test over policy simulator and works fine
I created a new group, and in it, i created a new policy that
enables all sts actions, over all resources.
I ran a test with the policy simulator, to sts assume role, pointing
to the ARN of role created at step one; and it works fine
I created a new user, and put it in group created at step 3
With the credentials of the new user, i try to get a new credentials
using sts asume role, but throw me an error that say my user is not
authorized to perform sts:AssumeRole
What am I doing wrong?
Policy in Group
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "some-large-id",
"Effect": "Allow",
"Action": [
"sts:*"
],
"Resource": [
"*"
]
}
]
}
Policy in role
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "another-large-id",
"Effect": "Allow",
"Action": [
"s3:PutObject"
],
"Resource": [
"arn:aws:s3:::my-bucket-name/*"
]
}
]
}
And finally calling like this
let policy = {
"Version": "2012-10-17",
"Statement": [
{
"Sid": "new-custom-id",
"Effect": "Allow",
"Action": ["s3:PutObject"],
"Resource": ["arn:aws:s3:::my-bucket-name/*"]
}
]
};
let params = {
DurationSeconds: 3600,
ExternalId: 'some-value',
Policy: JSON.stringify(policy),
RoleArn: "arn:aws:iam::NUMBER:role/ROLE-NAME", //Cheked, role is the same that step one
RoleSessionName: this.makeNewSessionId()
};
let sts = new AWS.STS({ apiVersion: '2012-08-10' });
sts.assumeRole(params, (err, data) => {
if(err) console.log(err);
else console.log(data);
});

Answer 1

There is a step that was missing: set trust relationship on role created in step one. No matter what privileges the user had, if the trust relationship is not set, STS will refuse the request.
Troubleshooting IAM Roles explain how it works.

Answer 2

On the role that you want to assume, for example using the STS Java V2 API (not Node), you need to set a trust relationship. In the trust relationship, specify the user to trust. For example:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::<AWS Account ID>:user/JohnDoe” //Specify the AWS ARN of your IAM user.
},
"Action": "sts:AssumeRole"
}
]
}
Now you can, for example, run a Java program to invoke the assumeRole operation.
package com.example.sts;
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.
*/
public class AssumeRole {
public static void main(String[] args) {
String roleArn = "arn:aws:iam::000540000000:role/s3role" ; // args[0];
String roleSessionName = "mysession101"; // args[1];
Region region = Region.US_EAST_1;
StsClient stsClient = StsClient.builder()
.region(region)
.build();
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();
// 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 temporary credentials expire on " + exTime );
} catch (StsException e) {
System.err.println(e.getMessage());
System.exit(1);
}
}
}
Without setting the Trust Relationship, this code does not work.

Answer 3

I met the same problem. These steps I fixed as below:
create new Role attach the policy: AmazonS3FullAccess, (copy the role ARN, use in code below)
Select Trust relationships tab - Edit Trust Relationship
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::IAM_USER_ID:user/haipv",//the roleARN need to be granted, use * for all
"Service": "s3.amazonaws.com"
},
"Action": "sts:AssumeRole"
}
]
}
update Trust relationships
Example code:
import com.amazonaws.AmazonServiceException;
import com.amazonaws.SdkClientException;
import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.auth.BasicSessionCredentials;
import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.services.s3.model.ObjectListing;
import com.amazonaws.services.securitytoken.AWSSecurityTokenService;
import com.amazonaws.services.securitytoken.AWSSecurityTokenServiceClientBuilder;
import com.amazonaws.services.securitytoken.model.AssumeRoleRequest;
import com.amazonaws.services.securitytoken.model.AssumeRoleResult;
import com.amazonaws.services.securitytoken.model.Credentials;
public class Main {
public static void main(String[] args) {
Regions clientRegion = Regions.AP_SOUTHEAST_1;
String roleARN = "arn:aws:iam::IAM_USER_ID:role/haipvRole"; // the roleARN coppied above
String roleSessionName = "haipv-session";
String bucketName = "haipv.docketName";//file_example_MP4_640_3MG.mp4
String accesskey = "YOURKEY";
String secretkey = "YOUR SECRET KEY";
try {
BasicAWSCredentials credentials = new BasicAWSCredentials(accesskey, secretkey);
// Creating the STS client is part of your trusted code. It has
// the security credentials you use to obtain temporary security credentials.
AWSSecurityTokenService stsClient = AWSSecurityTokenServiceClientBuilder.standard()
.withCredentials(new AWSStaticCredentialsProvider(credentials))
.withRegion(clientRegion)
.build();
// Obtain credentials for the IAM role. Note that you cannot assume the role of an AWS root account;
// Amazon S3 will deny access. You must use credentials for an IAM user or an IAM role.
AssumeRoleRequest roleRequest = new AssumeRoleRequest()
.withRoleArn(roleARN)
.withRoleSessionName(roleSessionName);
AssumeRoleResult roleResponse = stsClient.assumeRole(roleRequest);
Credentials sessionCredentials = roleResponse.getCredentials();
// Create a BasicSessionCredentials object that contains the credentials you just retrieved.
BasicSessionCredentials awsCredentials = new BasicSessionCredentials(
sessionCredentials.getAccessKeyId(),
sessionCredentials.getSecretAccessKey(),
sessionCredentials.getSessionToken());
// Provide temporary security credentials so that the Amazon S3 client
// can send authenticated requests to Amazon S3. You create the client
// using the sessionCredentials object.
AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
.withCredentials(new AWSStaticCredentialsProvider(awsCredentials))
.withRegion(clientRegion)
.build();
// Verify that assuming the role worked and the permissions are set correctly
// by getting a set of object keys from the bucket.
ObjectListing objects = s3Client.listObjects(bucketName);
System.out.println("No. of Objects: " + objects.getObjectSummaries().size());
}
catch(AmazonServiceException e) {
// The call was transmitted successfully, but Amazon S3 couldn't process
// it, so it returned an error response.
e.printStackTrace();
}
catch(SdkClientException e) {
// Amazon S3 couldn't be contacted for a response, or the client
// couldn't parse the response from Amazon S3.
e.printStackTrace();
}
}
}
Refer the official document in this link
It works for me.

Answer 4

In my case, in addition to adding the "Action": "sts:AssumeRole" (for the specific ARN) under the Trust relationship tab, I also had to add the following in Permissions tab:
{
"Version": "2012-10-17",
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": "*"
}
]
}

Answer 5

In addition to setting a trust relationship, if the region configured in your environment, is one of the enabled regions, e.g. af-south-1 and that region is not enabled in the account of the role you assume, you will get unauthorized error. This is even if all your permissions are configured correctly.

Answer 6

Just putting this here for people also encountering this. In my .aws/config file I had a line for role_arn and I mistakenly put in my user arn. You don't need to have that in there if you were assuming a role beforehand.