v4 authentication - payload verification with sha256 [JIRA: RCS-114]

[Basho-JIRA]

• Implement query parameter style auth case
• Test query parameter style case
  • boto?
  • Does ceph test support v4?

[shino]

As for Multipart Upload Part, AWS S3 adds 'ETag' which is MD5 hash of the content of part object.
Also, ETag of completed object is MD5 hash of concatenated parts' MD5 hash values. [1]

If riak cs follow this S3 behaivior, both MD5 and SHA256 of payload should be calculated.

[1] https://gist.github.com/shino/29676f0cf438fb56f3df

[shino]

For faked x-amx-contet-sha256, S3 responds with error
XAmzContentSHA256Mismatch [1]. It can be thought that
authentication is 2-phase, signature calculation (require headers
only) and post accept body sha256 verification.

<?xml version="1.0" encoding="UTF-8"?>
<Error>
  <Code>XAmzContentSHA256Mismatch</Code>
  <Message>The provided 'x-amz-content-sha256' header does not match what was computed.</Message>
  <ClientComputedContentSHA256>0000000000000000000000000000000000000000000000000000000000000000</ClientComputedContentSHA256>
  <S3ComputedContentSHA256>809fa1ed21450f59827d1e9aec720bbc4b687434fa22283c6cb5dd82a47ab9c0</S3ComputedContentSHA256>
  <RequestId>A3D32EA3F062DB15</RequestId>
  <HostId>vE48bS9V+VHXMkrCiKdcTGbL/wiRPzFhOor4O5TV1ZT5NUeOFvHx9dOjkHvFrwCv21CvQOXJH4w=</HostId>
</Error>

[1] https://gist.github.com/shino/54cdcb2c8475d9699789 (it includes
faked Content-MD5 case too)