AWS RDS: Access Denied Error When Granting All Privileges with @'%' - Solution Included

In AWS RDS for MySQL or MariaDB, attempting to grant all privileges to a user using GRANT ALL PRIVILEGES ON the_db.* TO 'the_user'@'%' results in an "Access denied" error. This occurs because the wildcard character % in the @ clause ('the_user'@'%') tries to grant access from any host, which is a security restriction in RDS.

Understanding the Code:

• GRANT ALL PRIVILEGES: This grants all available MySQL or MariaDB privileges to the user.
• ON the_db.*: This specifies that the privileges apply to all objects (tables, views, etc.) within the database named the_db.
• TO 'the_user': This defines the username receiving the privileges.
• @'%': This indicates the host from which the user can connect. Here, % is a wildcard that would allow connections from any host.

AWS RDS Security Restriction:

AWS RDS, for security reasons, restricts the master account (the administrative user) from having access to the underlying MySQL or MariaDB instance. Consequently, using % to allow connections from any host doesn't work as intended in the RDS environment.

Resolving the Issue:

Here's how to grant the user necessary privileges while maintaining security:

1. Specify a Specific Host: Replace @'%' with the actual hostname or IP address from where the user will connect. For example:

   GRANT ALL PRIVILEGES ON the_db.* TO 'the_user'@'allowed_host.com';
   

   Replace allowed_host.com with the authorized host.

Example with Specific Privileges:

GRANT SELECT, INSERT, UPDATE, DELETE ON the_db.* TO 'the_user'@'allowed_host.com';

GRANT ALL PRIVILEGES ON the_db.* TO 'the_user'@'allowed_host.com';

In this example:

• the_db: Replace this with the actual name of the database you want to grant access to.
• the_user: Replace this with the username you're creating or modifying.
• allowed_host.com: Replace this with the hostname or IP address from where the user will be connecting. This restricts access only to connections originating from that specific location.

Granting Specific Privileges to a User from a Specific Host (Recommended for Security):

GRANT SELECT, INSERT, UPDATE, DELETE ON the_db.* TO 'the_user'@'allowed_host.com';

Here, we're granting only the following privileges:

• SELECT: Allows the user to retrieve data from the database.
• UPDATE: Allows the user to modify existing data in the database.

Revoking Privileges from a User:

REVOKE ALL PRIVILEGES ON the_db.* FROM 'the_user'@'allowed_host.com';

This code revokes all privileges granted to the_user from allowed_host.com for the database the_db.

Important Notes:

• Remember to replace the placeholders (the_db, the_user, and allowed_host.com) with your actual values.
• Securely manage your RDS credentials and avoid using % (wildcard) for host access in production environments.
• Granting only the necessary privileges is a security best practice, as it minimizes the potential impact of unauthorized access.

Instead of relying on traditional MySQL/MariaDB user accounts, consider using AWS Identity and Access Management (IAM) for authentication. This eliminates the need to manage separate database credentials and provides more granular control over access permissions. You can create IAM roles with specific permissions and then map those roles to your application users.

Here's a high-level overview of the steps:

• Create an IAM role in your AWS account with the required RDS permissions (e.g., AmazonRDSFullAccess for full access or specific actions like rds:DescribeDBInstances, rds:CreateDBInstance, etc.).
• Configure your RDS instance to accept connections from IAM users.
• Create IAM user accounts for your application users.
• Attach the IAM role created in step 1 to the IAM user accounts.

Security Groups:

Utilize AWS security groups to further restrict access to your RDS instance. Security groups act as firewalls, controlling inbound and outbound traffic for your instances. You can create a security group that allows connections only from specific IP addresses or VPC subnets where your authorized applications reside.

Temporary Credentials:

For scenarios requiring short-lived access (e.g., database backups, administrative tasks), consider using temporary credentials generated through IAM roles and Security Token Service (STS). This grants temporary access tokens with a defined expiration time, minimizing the security risk associated with long-lasting credentials.

Choosing the Right Approach:

The best approach depends on your specific needs and security requirements. Here are some general guidelines:

• Simple Applications: For basic access control, granting specific privileges to users from authorized hosts within your network might suffice.
• Enhanced Security: If strict security is paramount, consider using IAM authentication with finely-grained IAM roles and security groups.
• Short-Term Access: For temporary access needs, leverage temporary credentials generated through IAM roles and STS.