introduce new package pkg/kms (#12019)

This commit introduces a new package `pkg/kms`.
It contains basic types and functions to interact
with various KMS implementations.

This commit also moves KMS-related code from `cmd/crypto`
to `pkg/kms`. Now, it is possible to implement a KMS-based
config data encryption in the `pkg/config` package.

cmd/config/crypto_test.go

@@ -0,0 +1,116 @@
+// MinIO Cloud Storage, (C) 2021 MinIO, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"bytes"
+	"encoding/hex"
+	"io"
+	"io/ioutil"
+	"testing"
+
+	"github.com/minio/minio/pkg/kms"
+)
+
+var encryptDecryptTests = []struct {
+	Data    []byte
+	Context kms.Context
+}{
+	{
+		Data:    nil,
+		Context: nil,
+	},
+	{
+		Data:    []byte{1},
+		Context: nil,
+	},
+	{
+		Data:    []byte{1},
+		Context: kms.Context{"key": "value"},
+	},
+	{
+		Data:    make([]byte, 1<<20),
+		Context: kms.Context{"key": "value", "a": "b"},
+	},
+}
+
+func TestEncryptDecrypt(t *testing.T) {
+	key, err := hex.DecodeString("ddedadb867afa3f73bd33c25499a723ed7f9f51172ee7b1b679e08dc795debcc")
+	if err != nil {
+		t.Fatalf("Failed to decode master key: %v", err)
+	}
+	KMS, err := kms.New("my-key", key)
+	if err != nil {
+		t.Fatalf("Failed to create KMS: %v", err)
+	}
+
+	for i, test := range encryptDecryptTests {
+		ciphertext, err := Encrypt(KMS, bytes.NewReader(test.Data), test.Context)
+		if err != nil {
+			t.Fatalf("Test %d: failed to encrypt stream: %v", i, err)
+		}
+		data, err := ioutil.ReadAll(ciphertext)
+		if err != nil {
+			t.Fatalf("Test %d: failed to encrypt stream: %v", i, err)
+		}
+
+		plaintext, err := Decrypt(KMS, bytes.NewReader(data), test.Context)
+		if err != nil {
+			t.Fatalf("Test %d: failed to decrypt stream: %v", i, err)
+		}
+		data, err = ioutil.ReadAll(plaintext)
+		if err != nil {
+			t.Fatalf("Test %d: failed to decrypt stream: %v", i, err)
+		}
+
+		if !bytes.Equal(data, test.Data) {
+			t.Fatalf("Test %d: decrypted data does not match original data", i)
+		}
+	}
+}
+
+func BenchmarkEncrypt(b *testing.B) {
+	key, err := hex.DecodeString("ddedadb867afa3f73bd33c25499a723ed7f9f51172ee7b1b679e08dc795debcc")
+	if err != nil {
+		b.Fatalf("Failed to decode master key: %v", err)
+	}
+	KMS, err := kms.New("my-key", key)
+	if err != nil {
+		b.Fatalf("Failed to create KMS: %v", err)
+	}
+
+	benchmarkEncrypt := func(size int, b *testing.B) {
+		var (
+			data      = make([]byte, size)
+			plaintext = bytes.NewReader(data)
+			context   = kms.Context{"key": "value"}
+		)
+		b.SetBytes(int64(size))
+		for i := 0; i < b.N; i++ {
+			ciphertext, err := Encrypt(KMS, plaintext, context)
+			if err != nil {
+				b.Fatal(err)
+			}
+			if _, err = io.Copy(ioutil.Discard, ciphertext); err != nil {
+				b.Fatal(err)
+			}
+			plaintext.Reset(data)
+		}
+	}
+	b.Run("1KB", func(b *testing.B) { benchmarkEncrypt(1*1024, b) })
+	b.Run("512KB", func(b *testing.B) { benchmarkEncrypt(512*1024, b) })
+	b.Run("1MB", func(b *testing.B) { benchmarkEncrypt(1024*1024, b) })
+	b.Run("10MB", func(b *testing.B) { benchmarkEncrypt(10*1024*1024, b) })
+}