The problem stemming from object keys starting with a period (or containing special characters not typically used in filenames) is indeed a tricky one to catch, primarily because the significance of such characters may not be immediately apparent.
For the benefit of others facing similar issues with AWS S3 or the AWS SDK in general, here are some steps to troubleshoot the “The request signature we calculated does not match the signature you provided. Check your key and signing method” error:
- Double-check AWS Credentials: Ensure that the AWS access key ID and secret access key are correctly entered, with no leading or trailing whitespace. As a best practice, always rotate these keys regularly and keep them secure.
- Verify the Bucket and Object Key Names: Special characters or leading/trailing spaces in bucket or object key names can cause issues. In your case, a leading period in the object key was the culprit.
- Time Synchronization: Ensure the system time is accurately synchronized. AWS request signatures include a timestamp, and significant skew between your system’s clock and AWS’s servers can cause this error.
- Encoding and Special Characters: When using special characters in object keys, ensure they are correctly URL-encoded. Some SDKs handle this automatically, but it’s something to be aware of if manually constructing requests.
- SDK and Library Versions: Using older versions of SDKs can sometimes lead to compatibility issues. While you resolved your issue with the version you’re on, it’s generally a good idea to use the most recent stable SDK version, as long as it’s compatible with your runtime environment.
- Request Headers: If you’re setting custom headers, ensure they’re correctly formatted and valid. Incorrect headers or missing required headers can lead to signature mismatches.
- HTTPS vs. HTTP: Use HTTPS to ensure that your requests are secure and that headers are not modified in transit.
For future troubleshooting, enabling detailed logging for the SDK can provide more insights into the request and response process, which can be invaluable for diagnosing issues like this.
Sharing your solution is immensely helpful, as it highlights how seemingly minor details can lead to significant issues. It also serves as a reminder of the importance of paying close attention to all aspects of request construction, especially in environments as sensitive to details as AWS.