Add managed SigV4a signer.

[teo-tsirpanis]

Describe the feature

Using the AWS SigV4a signature scheme it in the AWS SDK for .NET currently requires an extra NuGet dependency to the native aws-c-auth library. However, all the frameworks supported by V4 have the required elliptic curve cryptography APIs to implement SigV4a entirely in managed code.

Use Case

Eliminate optional dependency to native code and increase platform compatibility.

Proposed Solution

• AWS4aSigner class gets added.
• AWS4aSignerCRTWrapper class and all related APIs in AWSSDK.Core and AWSSDK.Extensions.CrtIntegration get deprecated.

Other Information

I have started an implementation on my machine, will open a PR soon.

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

AWS .NET SDK and/or Package version used

AWSSDK.Core V4

Targeted .NET Platform

All supported frameworks

Operating System and version

All supported operating systems

[dscpinheiro]

We have the intent to create a SigV4A signer that doesn't require the CRT (it was one of the reasons we chose net472 as the minimum TFM for V4 - it includes the APIs we need), but to be transparent with you this is something we need to work with our AppSec team to ensure its correctness (a PR from an external contributor reviewed by our team would not be enough).

If you want to create a draft PR to start that process that'd be welcomed but we cannot commit to release it until we go through our internal review process.