Add IAM groups support (#7981)

This change adds admin APIs and IAM subsystem APIs to:

- add or remove members to a group (group addition and deletion is
  implicit on add and remove)

- enable/disable a group

- list and fetch group info

pkg/madmin/group-commands.go

@@ -0,0 +1,164 @@
+/*
+ * MinIO Cloud Storage, (C) 2018-2019 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"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+)
+
+// GroupAddRemove is type for adding/removing members to/from a group.
+type GroupAddRemove struct {
+	Group    string   `json:"group"`
+	Members  []string `json:"members"`
+	IsRemove bool     `json:"isRemove"`
+}
+
+// UpdateGroupMembers - adds/removes users to/from a group. Server
+// creates the group as needed. Group is removed if remove request is
+// made on empty group.
+func (adm *AdminClient) UpdateGroupMembers(g GroupAddRemove) error {
+	data, err := json.Marshal(g)
+	if err != nil {
+		return err
+	}
+
+	reqData := requestData{
+		relPath: "/v1/update-group-members",
+		content: data,
+	}
+
+	// Execute PUT on /minio/admin/v1/update-group-members
+	resp, err := adm.executeMethod("PUT", reqData)
+
+	defer closeResponse(resp)
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return httpRespToErrorResponse(resp)
+	}
+
+	return nil
+}
+
+// GroupDesc is a type that holds group info along with the policy
+// attached to it.
+type GroupDesc struct {
+	Name    string   `json:"name"`
+	Status  string   `json:"status"`
+	Members []string `json:"members"`
+	Policy  string   `json:"policy"`
+}
+
+// GetGroupDescription - fetches information on a group.
+func (adm *AdminClient) GetGroupDescription(group string) (*GroupDesc, error) {
+	v := url.Values{}
+	v.Set("group", group)
+	reqData := requestData{
+		relPath:     "/v1/group",
+		queryValues: v,
+	}
+
+	resp, err := adm.executeMethod("GET", reqData)
+	defer closeResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp)
+	}
+
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	gd := GroupDesc{}
+	if err = json.Unmarshal(data, &gd); err != nil {
+		return nil, err
+	}
+
+	return &gd, nil
+}
+
+// ListGroups - lists all groups names present on the server.
+func (adm *AdminClient) ListGroups() ([]string, error) {
+	reqData := requestData{
+		relPath: "/v1/groups",
+	}
+
+	resp, err := adm.executeMethod("GET", reqData)
+	defer closeResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp)
+	}
+
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	groups := []string{}
+	if err = json.Unmarshal(data, &groups); err != nil {
+		return nil, err
+	}
+
+	return groups, nil
+}
+
+// GroupStatus - group status.
+type GroupStatus string
+
+// GroupStatus values.
+const (
+	GroupEnabled  GroupStatus = "enabled"
+	GroupDisabled GroupStatus = "disabled"
+)
+
+// SetGroupStatus - sets the status of a group.
+func (adm *AdminClient) SetGroupStatus(group string, status GroupStatus) error {
+	v := url.Values{}
+	v.Set("group", group)
+	v.Set("status", string(status))
+
+	reqData := requestData{
+		relPath:     "/v1/set-group-status",
+		queryValues: v,
+	}
+
+	resp, err := adm.executeMethod("PUT", reqData)
+	defer closeResponse(resp)
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return httpRespToErrorResponse(resp)
+	}
+
+	return nil
+}