KMS Admin-API: add route and handler for KMS key info

This commit adds an admin API route and handler for
requesting status information about a KMS key.

Therefore, the client specifies the KMS key ID (when
empty / not set the server takes the currently configured
default key-ID) and the server tries to perform a dummy encryption
and decryption operation. If both succeed we know that the
server can access the KMS and has permissions to generate and
decrypt data keys (policy is set correctly).

cmd/admin-handlers.go

@@ -19,6 +19,7 @@ package cmd
 import (
 	"bytes"
 	"context"
+	"crypto/subtle"
 	"encoding/base64"
 	"encoding/json"
 	"errors"
@@ -34,6 +35,7 @@ import (
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
 
+	"github.com/minio/minio/cmd/crypto"
 	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/cpu"
@@ -1519,3 +1521,70 @@ func (a adminAPIHandlers) TraceHandler(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 }
+
+// KMSKeyInfoHandler - GET /minio/admin/v1/kms/key/info?key-id=<master-key-id>
+func (a adminAPIHandlers) KMSKeyInfoHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := newContext(r, w, "KMSKeyInfoHandler")
+
+	objectAPI := validateAdminReq(ctx, w, r)
+	if objectAPI == nil {
+		return
+	}
+
+	if GlobalKMS == nil {
+		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrKMSNotConfigured), r.URL)
+		return
+	}
+
+	keyID, ok := mux.Vars(r)["key-id"]
+	if !ok || keyID == "" {
+		keyID = globalKMSKeyID
+	}
+	var response = madmin.KMSKeyInfoResponse{
+		KeyID: keyID,
+	}
+
+	kmsContext := crypto.Context{"MinIO admin API": "KMSKeyInfoHandler"} // Context for a test key operation
+	// 1. Generate a new key using the KMS.
+	key, sealedKey, err := GlobalKMS.GenerateKey(keyID, kmsContext)
+	if err != nil {
+		response.Status.EncryptionErr = err.Error()
+		resp, err := json.Marshal(response)
+		if err != nil {
+			writeCustomErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInternalError), err.Error(), r.URL)
+			return
+		}
+		writeSuccessResponseJSON(w, resp)
+		return
+	}
+	// 2. Verify that we can indeed decrypt the (encrypted) key
+	decryptedKey, err := GlobalKMS.UnsealKey(keyID, sealedKey, kmsContext)
+	if err != nil {
+		response.Status.DecryptionErr = err.Error()
+		resp, err := json.Marshal(response)
+		if err != nil {
+			writeCustomErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInternalError), err.Error(), r.URL)
+			return
+		}
+		writeSuccessResponseJSON(w, resp)
+		return
+	}
+	// 3. Compare generated key with decrypted key
+	if subtle.ConstantTimeCompare(key[:], decryptedKey[:]) != 1 {
+		response.Status.DecryptionErr = "The generated and the decrypted data key do not match"
+		resp, err := json.Marshal(response)
+		if err != nil {
+			writeCustomErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInternalError), err.Error(), r.URL)
+			return
+		}
+		writeSuccessResponseJSON(w, resp)
+		return
+	}
+
+	resp, err := json.Marshal(response)
+	if err != nil {
+		writeCustomErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInternalError), err.Error(), r.URL)
+		return
+	}
+	writeSuccessResponseJSON(w, resp)
+}

cmd/admin-router.go

@@ -120,6 +120,11 @@ func registerAdminRouter(router *mux.Router, enableConfigOps, enableIAMOps bool)
 
 	// HTTP Trace
 	adminV1Router.Methods(http.MethodGet).Path("/trace").HandlerFunc(adminAPI.TraceHandler)
+
+	// -- KMS APIs --
+	//
+	adminV1Router.Methods(http.MethodGet).Path("/kms/key/info").HandlerFunc(httpTraceAll(adminAPI.KMSKeyInfoHandler))
+
 	// If none of the routes match, return error.
 	adminV1Router.NotFoundHandler = http.HandlerFunc(httpTraceHdrs(notFoundHandlerJSON))
 }

pkg/madmin/examples/kms-status.go

@@ -0,0 +1,55 @@
+// +build ignore
+
+/*
+ * MinIO Cloud Storage, (C) 2018 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 main
+
+import (
+	"log"
+
+	"github.com/minio/minio/pkg/madmin"
+)
+
+func main() {
+	// Note: YOUR-ACCESSKEYID, YOUR-SECRETACCESSKEY and my-bucketname are
+	// dummy values, please replace them with original values.
+
+	// API requests are secure (HTTPS) if secure=true and insecure (HTTPS) otherwise.
+	// New returns an MinIO Admin client object.
+	madmClnt, err := madmin.New("your-minio.example.com:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	info, err := madmClnt.GetKeyInfo("") // empty string refers to the default master key
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	log.Printf("Key: %s\n", info.KeyID)
+	if info.Status.EncryptionErr == "" {
+		log.Println("\t • Encryption ✔")
+	}else {
+		log.Printf("\t • Encryption failed: %s\n", info.Status.EncryptionErr)
+	}
+	if info.Status.DecryptionErr == "" {
+		log.Println("\t • Decryption ✔")
+	}else {
+		log.Printf("\t •  Decryption failed: %s\n", info.Status.DecryptionErr)
+	}
+}

pkg/madmin/kms-commands.go

@@ -0,0 +1,66 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 madmin
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/url"
+)
+
+// GetKeyInfo requests information about the key referenced by keyID
+// from the KMS connected to a MinIO by performing a Admin-API request.
+// It basically hits the `/minio/admin/v1/kms/key/info` API endpoint.
+func (adm *AdminClient) GetKeyInfo(keyID string) (*KMSKeyInfoResponse, error) {
+	// GET /minio/admin/v1/kms/key/info?key-id=<keyID>
+	qv := url.Values{}
+	qv.Set("key-id", keyID)
+	reqData := requestData{
+		relPath:     "/v1/kms/key/info",
+		queryValues: qv,
+	}
+
+	resp, err := adm.executeMethod("GET", reqData)
+	defer closeResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp)
+	}
+	var keyInfo KMSKeyInfoResponse
+	if err = json.NewDecoder(resp.Body).Decode(&keyInfo); err != nil {
+		return nil, err
+	}
+	return &keyInfo, nil
+}
+
+// KMSKeyStatus is the status of a particular key at the KMS.
+// It indicates whether the key can be used by the MinIO server
+// for encryption as well as decryption.
+type KMSKeyStatus struct {
+	EncryptionErr string `json:"encryption-error,omitempty"` // An empty error == success
+	DecryptionErr string `json:"decryption-error,omitempty"` // An empty error == success
+}
+
+// KMSKeyInfoResponse is the response returned by a MinIO server
+// when the GetKeyInfo() call returns successfully. It contains
+// status information about one particular key at the KMS.
+type KMSKeyInfoResponse struct {
+	KeyID  string       `json:"key-id"`
+	Status KMSKeyStatus `json:"status"`
+}