RDS IAM authentication and MySQL ERROR 1045

May 3, 2024 #aws #iam #database #cloud9

Are you trying to connect to your MySQL DB instance using IAM authentication using the AWS CLI and mysql client and getting this error?

ERROR 1045 (28000): Access denied for user ‘user1’@‘’ (using password: YES)

Lucky you! Well not lucky so far, but hopefully lucky now. I fought with a scenario for longer than I will admit in public, but this post documents my struggle and how I ended up blaming AWS Cloud9.

✅ Watched IAM Authentication with Amazon Aurora MySQL to see how everything works.

Created an IAM policy for database access after finding DB instance resource ID using CLI

aws rds describe-db-instances --db-instance-identifier database-1-instance-1 | jq -r ".DBInstances[].DbiResourceId"
  "Version": "2012-10-17",
  "Statement": [
      "Effect": "Allow",
      "Action": [
      "Resource": [

Since I want to follow Security best practices for Amazon RDS for MySQL and MariaDB instances, my database is only accessible from its VPC. I created a Cloud9 instance with the right security groups to access the database host and port.

✅ Downloaded the Certificate bundles for all AWS Regions to Cloud9 using wget


✅ Connected to database as admin without having my password appear in .bash_history

mysql --host=$RDSHOST --port=3306 --ssl-ca=global-bundle.pem  --user=admin --password=$(read -s;echo $REPLY)
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 8128
Server version: 8.0.28 Source distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]>

✅ Create user1 in the database using IAM authentication

CREATE USER user1 IDENTIFIED WITH AWSAuthenticationPlugin as 'RDS';

✅ Generated token using bash command copied from Connecting to a DB instance

TOKEN="$(aws rds generate-db-auth-token --hostname $RDSHOST --port 3306 --region us-east-1 --username user1 )"

❌ Failed to connect to database using $TOKEN

mysql --host=$RDSHOST --port=3306 --ssl-ca=global-bundle.pem  --user=user1 --password=$TOKEN
ERROR 1045 (28000): Access denied for user 'user1'@'' (using password: YES)

✅ Verified from RDS logs that I connected to the database

RDS > Databases > database-1 > database-1-instance-1 > error/mysql-error.log

2024-05-03T00:00:00.000000Z 5281 [Note] [MY-010926] [Server] Access denied for user ‘user1’@‘’ (using password: YES) (

This must be an IAM issue - I even changed the IAM policy to use resource arn:aws:rds-db:us-east-1:123456789012:dbuser:*/* and after another aws rds generate-db-auth-token there was still access denied.

✅ Verified user1 was created correctly

MySQL [(none)]> SELECT User, Host, plugin, authentication_string FROM mysql.user WHERE user = "user1";
| User  | Host | plugin                  | authentication_string |
| user1 | %    | AWSAuthenticationPlugin | RDS                   |
1 row in set (0.063 sec)

✅ Be confused, but eventually blame AWS managed temporary credentials and their restrictions on iam and sts actions.

I temporarily solved this by running aws rds generate-db-auth-token outside of Cloud9, copying that string value, and pasting into my Cloud9 terminal session (e.g. TOKEN="<pasted token>"). After that I was able to connect as expected and have the SELECT CURRENT_USER() to prove it.

| user1@%        |
1 row in set (0.073 sec)

Kevin Hakanson

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