admin: Move SetCredentials from Service to Generic (#3805)

Setting credentials doesn't belong to service management API
anymore.

pkg/madmin/generic-commands.go

@@ -0,0 +1,72 @@
+/*
+ * Minio Cloud Storage, (C) 2016, 2017 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 (
+	"bytes"
+	"encoding/xml"
+	"errors"
+	"net/http"
+	"net/url"
+)
+
+// setCredsReq - xml to send to the server to set new credentials
+type setCredsReq struct {
+	Username string `xml:"username"`
+	Password string `xml:"password"`
+}
+
+// SetCredentials - Call Set Credentials API to set new access and secret keys in the specified Minio server
+func (adm *AdminClient) SetCredentials(access, secret string) error {
+
+	// Disallow sending with the server if the connection is not secure
+	if !adm.secure {
+		return errors.New("setting new credentials requires HTTPS connection to the server")
+	}
+
+	// Setup new request
+	reqData := requestData{}
+	reqData.queryValues = make(url.Values)
+	reqData.queryValues.Set("service", "")
+	reqData.customHeaders = make(http.Header)
+	reqData.customHeaders.Set(minioAdminOpHeader, "set-credentials")
+
+	// Setup request's body
+	body, err := xml.Marshal(setCredsReq{Username: access, Password: secret})
+	if err != nil {
+		return err
+	}
+	reqData.contentBody = bytes.NewReader(body)
+	reqData.contentLength = int64(len(body))
+	reqData.contentMD5Bytes = sumMD5(body)
+	reqData.contentSHA256Bytes = sum256(body)
+
+	// Execute GET on bucket to list objects.
+	resp, err := adm.executeMethod("POST", reqData)
+
+	defer closeResponse(resp)
+	if err != nil {
+		return err
+	}
+
+	// Return error to the caller if http response code is different from 200
+	if resp.StatusCode != http.StatusOK {
+		return httpRespToErrorResponse(resp)
+	}
+	return nil
+}