add HMAC API and use KMS secret key crypto (#433)

api_test.go

@@ -139,6 +139,7 @@ func testListAPIDefaults(t *testing.T) {
 		"/v1/key/generate/": {Method: http.MethodPut, MaxBody: 1 * mem.MB, Timeout: 15 * time.Second},
 		"/v1/key/encrypt/":  {Method: http.MethodPut, MaxBody: 1 * mem.MB, Timeout: 15 * time.Second},
 		"/v1/key/decrypt/":  {Method: http.MethodPut, MaxBody: 1 * mem.MB, Timeout: 15 * time.Second},
+		"/v1/key/hmac/":     {Method: http.MethodPut, MaxBody: 1 * mem.MB, Timeout: 15 * time.Second},
 
 		"/v1/policy/describe/": {Method: http.MethodGet, MaxBody: 0, Timeout: 15 * time.Second},
 		"/v1/policy/read/":     {Method: http.MethodGet, MaxBody: 0, Timeout: 15 * time.Second},

internal/api/api.go

@@ -35,6 +35,7 @@ const (
 	PathKeyGenerate = "/v1/key/generate/"
 	PathKeyEncrypt  = "/v1/key/encrypt/"
 	PathKeyDecrypt  = "/v1/key/decrypt/"
+	PathKeyHMAC     = "/v1/key/hmac/"
 
 	PathPolicyDescribe = "/v1/policy/describe/"
 	PathPolicyRead     = "/v1/policy/read/"

internal/api/request.go

@@ -26,3 +26,8 @@ type DecryptKeyRequest struct {
 	Ciphertext []byte `json:"ciphertext"`
 	Context    []byte `json:"context"` // optional
 }
+
+// HMACRequest is the request sent by clients when calling the HMAC API.
+type HMACRequest struct {
+	Message []byte `json:"message"`
+}

internal/api/response.go

@@ -71,6 +71,11 @@ type DecryptKeyResponse struct {
 	Plaintext []byte `json:"plaintext"`
 }
 
+// HMACResponse is the response sent to clients by the HMAC API.
+type HMACResponse struct {
+	Sum []byte `json:"hmac"`
+}
+
 // ReadPolicyResponse is the response sent to clients by the ReadPolicy API.
 type ReadPolicyResponse struct {
 	Name      string              `json:"name"`

internal/key/ciphertext.go → internal/crypto/ciphertext.go

@@ -1,43 +1,50 @@
-// Copyright 2022 - MinIO, Inc. All rights reserved.
+// Copyright 2024 - MinIO, Inc. All rights reserved.
 // Use of this source code is governed by the AGPLv3
 // license that can be found in the LICENSE file.
 
-package key
+package crypto
 
 import (
 	"encoding/json"
+	"slices"
 
 	"github.com/minio/kes-go"
 	"github.com/tinylib/msgp/msgp"
 )
 
-// decodeCiphertext parses the given bytes as
-// ciphertext. If it fails to unmarshal the
-// given bytes, decodeCiphertext returns
-// ErrDecrypt.
-func decodeCiphertext(bytes []byte) (ciphertext, error) {
-	if len(bytes) == 0 {
-		return ciphertext{}, kes.ErrDecrypt
+// parseCiphertext parses and converts a ciphertext into
+// the format expected by a SecretKey.
+//
+// Previous implementations of a SecretKey produced a structured
+// ciphertext. parseCiphertext converts all previously generated
+// formats into the one that SecretKey.Decrypt expects.
+func parseCiphertext(b []byte) []byte {
+	if len(b) == 0 {
+		return b
 	}
 
 	var c ciphertext
-	switch bytes[0] {
+	switch b[0] {
 	case 0x95: // msgp first byte
-		if err := c.UnmarshalBinary(bytes); err != nil {
-			return ciphertext{}, kes.ErrDecrypt
+		if err := c.UnmarshalBinary(b); err != nil {
+			return b
 		}
+
+		b = b[:0]
+		b = append(b, c.Bytes...)
+		b = append(b, c.IV...)
+		b = append(b, c.Nonce...)
 	case 0x7b: // JSON first byte
-		if err := c.UnmarshalJSON(bytes); err != nil {
-			return ciphertext{}, kes.ErrDecrypt
-		}
-	default:
-		if err := c.UnmarshalBinary(bytes); err != nil {
-			if err = c.UnmarshalJSON(bytes); err != nil {
-				return ciphertext{}, kes.ErrDecrypt
-			}
+		if err := c.UnmarshalJSON(b); err != nil {
+			return b
 		}
+
+		b = b[:0]
+		b = append(b, c.Bytes...)
+		b = append(b, c.IV...)
+		b = append(b, c.Nonce...)
 	}
-	return c, nil
+	return b
 }
 
 // ciphertext is a structure that contains the encrypted
@@ -51,22 +58,6 @@ type ciphertext struct {
 	Bytes     []byte
 }
 
-// MarshalBinary returns the ciphertext's binary representation.
-func (c *ciphertext) MarshalBinary() ([]byte, error) {
-	// We encode a ciphertext simply as message-pack
-	// flat array.
-	const Items = 5
-
-	var b []byte
-	b = msgp.AppendArrayHeader(b, Items)
-	b = msgp.AppendString(b, c.Algorithm.String())
-	b = msgp.AppendString(b, c.ID)
-	b = msgp.AppendBytes(b, c.IV)
-	b = msgp.AppendBytes(b, c.Nonce)
-	b = msgp.AppendBytes(b, c.Bytes)
-	return b, nil
-}
-
 // UnmarshalBinary parses b as binary-encoded ciphertext.
 func (c *ciphertext) UnmarshalBinary(b []byte) error {
 	const (
@@ -117,7 +108,7 @@ func (c *ciphertext) UnmarshalBinary(b []byte) error {
 	c.ID = id
 	c.IV = iv[:]
 	c.Nonce = nonce[:]
-	c.Bytes = clone(bytes...)
+	c.Bytes = slices.Clone(bytes)
 	return nil
 }