AWS RDS PostgresSQL Rejects Client Certs but Requires Them and Does Not Provide a Way to Sign: Unraveling the Enigma

The Root Cause of the Issue: A Certificate Conundrum

So, why does AWS RDS PostgresSQL reject client certificates despite requiring them? The answer lies in the way certificates are handled in AWS RDS:

AWS RDS PostgresSQL uses a self-signed certificate, which is not trusted by default. This means that when you attempt to connect to your database using a client certificate, the connection is rejected because the self-signed certificate is not trusted.

The Catch-22 of Signing Client Certificates

The real kicker is that there’s no straightforward way to sign client certificates in AWS RDS PostgresSQL. You can’t use the AWS Certificate Manager (ACM) or Amazon IAM to sign your client certificates, as these services are not integrated with RDS PostgresSQL.

This creates a classic Catch-22 situation: you need a trusted certificate to connect to your database, but you can’t get a trusted certificate because there’s no way to sign it!

A Step-by-Step Guide to Overcoming the Client Certificate Conundrum

Fear not, dear reader, for we’ve got a solution that will help you navigate this complex issue. Follow these steps to overcome the client certificate conundrum:

Step 1: Create a Self-Signed Certificate Authority (CA)

Create a self-signed CA certificate using OpenSSL:

openssl req -x509 -newkey rsa:2048 -nodes -keyout ca.key -out ca.crt -days 3650 -subj "/C=US/ST=State/L=Locality/O=Organization/CN=Root CA"

This will generate a self-signed CA certificate (ca.crt) and a private key (ca.key).

Step 2: Generate a Client Certificate

Generate a client certificate using the self-signed CA certificate:

openssl req -newkey rsa:2048 -nodes -keyout client.key -out client.csr -subj "/C=US/ST=State/L=Locality/O=Organization/CN=Client Certificate"
openssl x509 -req -in client.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out client.crt -days 3650

This will generate a client certificate (client.crt) and a private key (client.key).

Step 3: Configure Your PostgresSQL Server to Use the Self-Signed CA

Update your PostgresSQL server configuration to use the self-signed CA certificate:

alter system set ssl_ca_file = '/path/to/ca.crt';
alter system set ssl_cert_file = '/path/to/server.crt';
alter system set ssl_key_file = '/path/to/server.key';

Restart your PostgresSQL server to apply the changes.

Step 4: Connect to Your PostgresSQL Server Using the Client Certificate

Now it’s time to connect to your PostgresSQL server using the client certificate:

psql "host=localhost port=5432 dbname=mydatabase user=myuser sslmode=verify-full sslcert=client.crt sslkey=client.key sslrootcert=ca.crt"

Congratulations! You’ve successfully connected to your PostgresSQL server using a client certificate.

Conclusion

AWS RDS PostgresSQL’s requirement for client certificates, followed by their rejection, can be a frustrating experience. However, by following the steps outlined in this article, you can overcome this hurdle and secure your database connections using client certificates. Remember to keep your certificates up-to-date and ensure that they’re properly signed to avoid any issues.

With this comprehensive guide, you’re now well-equipped to tackle the enigmatic world of AWS RDS PostgresSQL client certificates. Happy coding!

1. AWS RDS PostgresSQL Security
2. PostgresSQL SSL/TLS Configuration
3. OpenSSL Request Configuration

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