Learn how to fix the “IncompleteSignature HTTP Status Code: 400” error in AWS Redshift Data API. Our AWS Support Team is here to help.

How to Fix the “IncompleteSignature HTTP Status Code: 400” Error in AWS Redshift Data API

When working with the AWS Redshift Data API, encountering HTTP status errors is not uncommon. One of the most frequent issues developers face is the “IncompleteSignature HTTP Status Code: 400” error.

This error usually points to problems with the request signature or authentication process.

Today, we will break down what the error means, why it happens, and how to fix it so we can keep our Redshift workflows running smoothly.

Understanding the IncompleteSignature Error

The IncompleteSignature error occurs when the AWS Redshift Data API receives a request with an improperly formatted or calculated signature. In simple terms, it means AWS cannot validate the request as authentic.

This error can be triggered by:

• Missing or misconfigured AWS credentials
• Incorrect AWS Access Key ID or Secret Access Key
• Using the wrong SES region
• A malformed request structure or incorrect request parameters
• Timestamps that don’t align with AWS server time
• Signature version mismatch

Beyond interrupting queries, the error also signals potential security and configuration issues that need immediate attention.

Common Causes

1. Misconfigured AWS Credentials

One of the most common culprits is incorrectly configured credentials in your application (e.g., Sendy).

• AWS Access Key ID or Secret Access Key may be wrong.
• Keys may be expired or disabled.
• Extra spaces in environment variables (like `AWS_ACCESS_KEY_ID`) can also cause signature failures.

2. Incorrect AWS SES Region

Amazon Simple Email Service (SES) approvals are tied to a specific region. For instance, we may be approved in N. Virginia (us-east-1), while the application is attempting to connect in Ireland (eu-west-1).

If the SES region is misconfigured in the application’s settings, authentication will fail.

3. Null Terminator in Region String

Another cause is when the region string is malformed due to an embedded null terminator (`\0`). This can happen when pulling region data from services like EC2 IMDSv2 and incorrectly parsing availability zones.

This issue has been reported especially in GitHub Actions when running CloudFront commands.

4. Other Factors

• Using an outdated signature version (must be SigV4).
• Timestamp mismatches between request and AWS server time.
• Incorrect request payload or missing parameters.

Solutions

Fix 1. Reconfigure AWS Credentials

1. Generate new access keys in the AWS Console (or use existing valid ones).
2. Add them to the application or service (e.g., Sendy’s settings).
3. Ensure no extra spaces or hidden characters are present in the keys.

Fix 2. Select the Correct SES Region

1. Log in to the AWS console.
2. Check which region the SES approval is active in.
3. Update the application’s settings (e.g., Sendy) to use that region.

The default region is often N. Virginia, so double-check if we are approved elsewhere.

Fix 3. Validate Request Structure

Ensure we are using Signature Version 4. Also double-check all request parameters, including cluster identifiers, database names, and SQL queries. Furthermore, confirm the request timestamp matches AWS server time.

Fix 4. Debug Null Terminator Errors

If using automation (such as GitHub Actions), inspect the code that builds the region string. Avoid overwriting characters with `\0` that may truncate the region name in the authorization header.

Fix 5. Check Environment Variables

Fix 5:
Sometimes an extra space at the end of `AWS_ACCESS_KEY_ID` or `AWS_SECRET_ACCESS_KEY` can cause authentication failures. Carefully re-check the environment configuration.

Python Example: Handling IncompleteSignature Errors

The boto3 library in Python handles most of the signing process automatically. Here’s an example of how to run a query safely and catch the `IncompleteSignature` error:

import boto3

from botocore.exceptions import ClientError

# Initialize a boto3 client for Redshift Data API

client = boto3.client('redshift-data', region_name='your-region')

try:

# Execute a sample query on Redshift

response = client.execute_statement(

ClusterIdentifier='your-cluster-identifier',

Database='your-database-name',

DbUser='your-db-user',

Sql='SELECT * FROM your_table LIMIT 10;'

)

print(response)

except ClientError as error:

if error.response['Error']['Code'] == 'IncompleteSignature':

print("Authentication failed: Check your AWS signature and credentials.")

else:

print(f"An error occurred: {error.response['Error']['Message']}")

This ensures that even if the error occurs, the application can handle it gracefully and provide a clear message.

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Conclusion

The “IncompleteSignature HTTP Status Code: 400” error in AWS Redshift is usually due to misconfigured credentials, a wrong SES region, or malformed requests. By carefully checking the keys, verifying regions, and ensuring proper request formatting, we can eliminate the issue and restore smooth operation.

In brief, our Support Experts demonstrated how to fix the “IncompleteSignature HTTP Status Code: 400” error in AWS Redshift Data API.