Add support for sse-s3 encryption with vault as KMS.
Also refactoring code to make use of headers and functions defined in
crypto package and clean up duplicated code.
This commit adds a basic KMS implementation for an
operator-specified SSE-S3 master key. The master key
is wrapped as KMS such that using SSE-S3 with master key
and SSE-S3 with KMS can use the same code.
Bindings for a remote / true KMS (like hashicorp vault)
will be added later on.
This commit updates the key derivation to reflect the
latest change of crypto/doc.go. This includes handling
the insecure legacy KDF.
Since #6064 is fixed, the 3. test case for object key
generation is enabled again.
This commit introduces a new crypto package providing
AWS S3 related cryptographic building blocks to implement
SSE-S3 (master key or KMS) and SSE-C.
This change only adds some basic functionallity esp.
related to SSE-S3 and documents the general approach
for SSE-S3 and SSE-C.
