Troubleshooting AWS PostgreSQL ODBC Failures in Toad: IAM Authentication Error

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If you’re having trouble connecting to your AWS RDS PostgreSQL database using the AWS ODBC driver and get an error about IAM authentication failing, you’re not alone. Many users find that connecting directly through tools like Toad Data Point works fine, but setting up a System DSN or using ADO (ActiveX Data Objects) in VBA throws an authentication error. Here’s a straightforward way to troubleshoot and fix this issue.

First, understand that AWS uses temporary IAM tokens for database authentication. These tokens are long strings—usually between 1400 and 1700 characters—that expire after about 15 minutes. When you generate an IAM token from the command line or AWS console, it’s essential to ensure it’s correctly captured and used.

In your setup, you’re generating the token by logging into AWS via a browser, then running a command in the command prompt. This token is then used in your connection string or DSN configuration, with the Auth Type set to “database.” Toad Data Point connects successfully because it can handle the token correctly when connecting directly through the driver.

However, the problem occurs when creating a System DSN or connecting through ADO, which sometimes can have trouble handling very long tokens. This is because these methods might have length restrictions or may not process the token correctly if it’s truncated or if there are issues with how the token is passed in the connection string.

Given this scenario, here are some steps to resolve the problem:

Ensure Proper Token Generation and Usage: Make sure the token is fully captured and correctly copied. Test by saving the token to a text file and confirm its length matches what you expect. Avoid truncating the token at any point.
Check Connection String Parameters: When configuring your ADO connection or DSN, double-check that the token parameter is set exactly as generated by AWS. Avoid manual editing that might cut off part of the token.
Update or Use Different Drivers: Sometimes, driver versions might have limitations. Confirm you are using the latest AWS ODBC driver designed for your system (x64). Also, verify if the driver version fully supports IAM authentication with long tokens.
Experiment with SSL Mode Settings: Although changing SSL modes (disabled, prefer, require) doesn’t usually fix authentication issues, it can help rule out SSL-related conflicts.
Consider Alternative Methods for Passing the Token: If length is an issue, see if you can use environment variables or scripts to pass the token dynamically during connection setup, rather than embedding it directly in the connection string.
Test with Different Tools: Since direct connection via Toad works successfully, try creating a simplified test script that uses the same connection string parameters. If it works outside of the DSN and ADO, the problem is likely related to how these methods handle the token.
Consult Documentation and Support: AWS documentation details the IAM token handling process. If the problem persists, contact AWS support with details of your setup and error messages—they can provide guidance specific to your environment.

In summary, the key issue appears to be related to handling the lengthy IAM token in the System DSN setup or ADO connection string. Ensuring the token is fully captured, correctly used, and that your driver and connection methods support such long tokens should resolve the problem. Keep your tools updated, and don’t hesitate to try generating tokens dynamically at runtime for more reliable authentication.