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Signature mismatch error in SAP CPI
How to fix this error
Canonical Request(see attached), StringtoSignin(see attached), signature is same with the authorization header.
<ErrorResponse xmlns="https://iam.amazonaws.com/doc/2010-05-08/">
<Error>
<Type>Sender</Type>
<Code>SignatureDoesNotMatch</Code>
<Message>The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.</Message>
</Error>
<RequestId>734a9c31-ffd7-4647-9d85-104aa78330b2</RequestId>
</ErrorResponse>
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The "SignatureDoesNotMatch" error you're encountering in SAP CPI (Cloud Platform Integration) when interacting with AWS services indicates that the signature calculated by AWS does not match the one provided in your request. This can occur due to several reasons, even if the Canonical Request and StringToSign appear to be correct. Here are some steps to troubleshoot and potentially resolve the issue:
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Verify credentials: Ensure you're using the correct Access Key ID and Secret Access Key for your AWS account. Even a slight mismatch can cause this error.
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Check timestamp: Make sure the timestamp in your request is accurate and within 15 minutes of the AWS server time. Significant time differences can cause signature mismatches.
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Examine headers: Verify that all required headers, especially the 'host' header and any 'x-amz-*' headers, are included in the signature calculation. These headers must be in lowercase and sorted alphabetically.
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Trim whitespace: Ensure there are no leading or trailing spaces in header values. Convert any sequential spaces to a single space.
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URI encoding: Use the correct URI encoding for the canonical request. Some standard encoding functions may not work correctly for AWS signatures, so you might need to use a custom UriEncode function.
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Signing algorithm: Confirm you're using the correct signing algorithm (AWS Signature Version 4) and following the exact steps for creating the canonical request, string to sign, and final signature.
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Line endings: Check that you're using the correct line endings (newline characters) when concatenating parts of the canonical request and string to sign.
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Multi-value headers: If you have headers with multiple values, ensure they are combined correctly (comma-separated) in the canonical request.
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Payload hash: Verify that the payload hash (x-amz-content-sha256 header) is calculated correctly and matches the actual request body.
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Library version: If you're using an AWS SDK or library, ensure it's up-to-date, as older versions might not implement the latest signature requirements.
If you've verified all these points and the issue persists, you may need to implement a step-by-step debug process, comparing your signature calculation with AWS's expected calculation at each stage. This can help pinpoint exactly where the mismatch is occurring.
Remember, even small discrepancies in how the signature is calculated can lead to this error, so meticulous attention to detail is crucial when troubleshooting.
Sources
Getting "SignatureDoesNotMatch" from cloudfront | AWS re:Post
Create a signed AWS API request - AWS Identity and Access Management
The request signature we calculated does not match the signature you provided. When I tried to access cloudfront. | AWS re:Post
Authenticating requests to the Amazon SES API - Amazon Simple Email Service
