add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

internal/crypto/key.go

@@ -90,7 +90,7 @@ func (key ObjectKey) Seal(extKey []byte, iv [32]byte, domain, bucket, object str
 		sealingKey   [32]byte
 		encryptedKey bytes.Buffer
 	)
-	mac := hmac.New(sha256.New, extKey[:])
+	mac := hmac.New(sha256.New, extKey)
 	mac.Write(iv[:])
 	mac.Write([]byte(domain))
 	mac.Write([]byte(SealAlgorithm))
@@ -118,7 +118,7 @@ func (key *ObjectKey) Unseal(extKey []byte, sealedKey SealedKey, domain, bucket,
 	default:
 		return Errorf("The sealing algorithm '%s' is not supported", sealedKey.Algorithm)
 	case SealAlgorithm:
-		mac := hmac.New(sha256.New, extKey[:])
+		mac := hmac.New(sha256.New, extKey)
 		mac.Write(sealedKey.IV[:])
 		mac.Write([]byte(domain))
 		mac.Write([]byte(SealAlgorithm))
@@ -126,7 +126,7 @@ func (key *ObjectKey) Unseal(extKey []byte, sealedKey SealedKey, domain, bucket,
 		unsealConfig = sio.Config{MinVersion: sio.Version20, Key: mac.Sum(nil), CipherSuites: fips.CipherSuitesDARE()}
 	case InsecureSealAlgorithm:
 		sha := sha256.New()
-		sha.Write(extKey[:])
+		sha.Write(extKey)
 		sha.Write(sealedKey.IV[:])
 		unsealConfig = sio.Config{MinVersion: sio.Version10, Key: sha.Sum(nil), CipherSuites: fips.CipherSuitesDARE()}
 	}

internal/crypto/key_test.go

@@ -164,7 +164,7 @@ func TestDerivePartKey(t *testing.T) {
 			t.Fatalf("Test %d failed to decode expected part-key: %v", i, err)
 		}
 		partKey := key.DerivePartKey(test.PartID)
-		if !bytes.Equal(partKey[:], expectedPartKey[:]) {
+		if !bytes.Equal(partKey[:], expectedPartKey) {
 			t.Errorf("Test %d derives wrong part-key: got '%s' want: '%s'", i, hex.EncodeToString(partKey[:]), test.PartKey)
 		}
 	}

internal/crypto/sse-kms.go

@@ -109,7 +109,7 @@ func (s3 ssekms) UnsealObjectKey(KMS kms.KMS, metadata map[string]string, bucket
 	if err != nil {
 		return key, err
 	}
-	err = key.Unseal(unsealKey[:], sealedKey, s3.String(), bucket, object)
+	err = key.Unseal(unsealKey, sealedKey, s3.String(), bucket, object)
 	return key, err
 }
 

internal/crypto/sse-s3.go

@@ -80,7 +80,7 @@ func (s3 sses3) UnsealObjectKey(KMS kms.KMS, metadata map[string]string, bucket,
 	if err != nil {
 		return key, err
 	}
-	err = key.Unseal(unsealKey[:], sealedKey, s3.String(), bucket, object)
+	err = key.Unseal(unsealKey, sealedKey, s3.String(), bucket, object)
 	return key, err
 }