add SSE-KMS support and use SSE-KMS for auto encryption (#12237)

This commit adds basic SSE-KMS support.
Now, a client can specify the SSE-KMS headers
(algorithm, optional key-id, optional context)
such that the object gets encrypted using the
SSE-KMS method. Further, auto-encryption now
defaults to SSE-KMS.

This commit does not try to do any refactoring
and instead tries to implement SSE-KMS as a minimal
change to the code base. However, refactoring the entire
crypto-related code is planned - but needs a separate
effort.

Signed-off-by: Andreas Auernhammer <aead@mail.de>

cmd/tier.go

@@ -29,7 +29,9 @@ import (
 	"sync"
 
 	"github.com/minio/madmin-go"
+	"github.com/minio/minio/cmd/crypto"
 	"github.com/minio/minio/pkg/hash"
+	"github.com/minio/minio/pkg/kms"
 )
 
 //go:generate msgp -file $GOFILE
@@ -236,9 +238,7 @@ func (config *TierConfigMgr) configReader() (*PutObjReader, *ObjectOptions, erro
 
 	// Encrypt json encoded tier configurations
 	metadata := make(map[string]string)
-	sseS3 := true
-	var extKey [32]byte
-	encBr, oek, err := newEncryptReader(hr, extKey[:], minioMetaBucket, tierConfigPath, metadata, sseS3)
+	encBr, oek, err := newEncryptReader(hr, crypto.S3, "", nil, minioMetaBucket, tierConfigPath, metadata, kms.Context{})
 	if err != nil {
 		return nil, nil, err
 	}