Add support for larger ECC curves (P521) in the PKCS11 implementation

[gregbreen]

Describe the feature

In attempting to use P521 with PKCS (SoftHSM), I encounter the AWS_ERROR_PKCS11_ENCODING_ERROR here:

aws-c-io/source/pkcs11_lib.c

Line 1173 in c4b661f

return aws_raise_error(AWS_ERROR_PKCS11_ENCODING_ERROR);

. It seems to be the case that the buffer is too small for P521. P256 and P384 are fine.

Use Case

AWS IoT Core recently added ECDSA-P521 as a supported key type: https://aws.amazon.com/about-aws/whats-new/2023/07/aws-iot-core-new-certificate-signing-key-generation-algorithms/. The SDK should support all key algorithms supported by IoT Core.

Proposed Solution

No response

Other Information

No response

Acknowledgements

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