Implement a dummy GetBucketACL for legacy reasons (#5906)

GetBucketACL call returns empty for all GET in ACL requests, 
the primary purpose of this PR is to provide legacy API support 
for legacy applications.

Fixes #5706

cmd/acl-handlers.go

@@ -0,0 +1,141 @@
+/*
+ * 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 cmd
+
+import (
+	"encoding/xml"
+	"net/http"
+
+	"github.com/gorilla/mux"
+	"github.com/minio/minio/pkg/policy"
+)
+
+// Data types used for returning dummy access control
+// policy XML, these variables shouldn't be used elsewhere
+// they are only defined to be used in this file alone.
+type grantee struct {
+	XMLNS       string `xml:"xmlns:xsi,attr"`
+	XMLXSI      string `xml:"xsi:type,attr"`
+	Type        string `xml:"Type"`
+	ID          string `xml:"ID,omitempty"`
+	DisplayName string `xml:"DisplayName,omitempty"`
+	URI         string `xml:"URI,omitempty"`
+}
+
+type grant struct {
+	Grantee    grantee `xml:"Grantee"`
+	Permission string  `xml:"Permission"`
+}
+
+type accessControlPolicy struct {
+	XMLName           xml.Name `xml:"AccessControlPolicy"`
+	Owner             Owner    `xml:"Owner"`
+	AccessControlList struct {
+		Grants []grant `xml:"Grant"`
+	} `xml:"AccessControlList"`
+}
+
+// GetBucketACLHandler - GET Bucket ACL
+// -----------------
+// This operation uses the ACL
+// subresource to return the ACL of a specified bucket.
+func (api objectAPIHandlers) GetBucketACLHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := newContext(r, "GetBucketACL")
+
+	vars := mux.Vars(r)
+	bucket := vars["bucket"]
+
+	objAPI := api.ObjectAPI()
+	if objAPI == nil {
+		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
+		return
+	}
+
+	// Allow getBucketACL if policy action is set, since this is a dummy call
+	// we are simply re-purposing the bucketPolicyAction.
+	if s3Error := checkRequestAuthType(ctx, r, policy.GetBucketPolicyAction, bucket, ""); s3Error != ErrNone {
+		writeErrorResponse(w, s3Error, r.URL)
+		return
+	}
+
+	// Before proceeding validate if bucket exists.
+	_, err := objAPI.GetBucketInfo(ctx, bucket)
+	if err != nil {
+		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
+		return
+	}
+
+	acl := &accessControlPolicy{}
+	acl.AccessControlList.Grants = append(acl.AccessControlList.Grants, grant{
+		Grantee: grantee{
+			Type: "CanonicalUser",
+		},
+		Permission: "FULL_CONTROL",
+	})
+	if err := xml.NewEncoder(w).Encode(acl); err != nil {
+		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
+		return
+	}
+
+	w.(http.Flusher).Flush()
+}
+
+// GetObjectACLHandler - GET Object ACL
+// -----------------
+// This operation uses the ACL
+// subresource to return the ACL of a specified object.
+func (api objectAPIHandlers) GetObjectACLHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := newContext(r, "GetObjectACL")
+
+	vars := mux.Vars(r)
+	bucket := vars["bucket"]
+	object := vars["object"]
+
+	objAPI := api.ObjectAPI()
+	if objAPI == nil {
+		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
+		return
+	}
+
+	// Allow getObjectACL if policy action is set, since this is a dummy call
+	// we are simply re-purposing the bucketPolicyAction.
+	if s3Error := checkRequestAuthType(ctx, r, policy.GetBucketPolicyAction, bucket, ""); s3Error != ErrNone {
+		writeErrorResponse(w, s3Error, r.URL)
+		return
+	}
+
+	// Before proceeding validate if object exists.
+	_, err := objAPI.GetObjectInfo(ctx, bucket, object)
+	if err != nil {
+		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
+		return
+	}
+
+	acl := &accessControlPolicy{}
+	acl.AccessControlList.Grants = append(acl.AccessControlList.Grants, grant{
+		Grantee: grantee{
+			Type: "CanonicalUser",
+		},
+		Permission: "FULL_CONTROL",
+	})
+	if err := xml.NewEncoder(w).Encode(acl); err != nil {
+		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
+		return
+	}
+
+	w.(http.Flusher).Flush()
+}

cmd/api-router.go

@@ -83,6 +83,10 @@ func registerAPIRouter(router *mux.Router) {
 		bucket.Methods("GET").HandlerFunc(httpTraceAll(api.GetBucketLocationHandler)).Queries("location", "")
 		// GetBucketPolicy
 		bucket.Methods("GET").HandlerFunc(httpTraceAll(api.GetBucketPolicyHandler)).Queries("policy", "")
+
+		// GetBucketACL -- this is a dummy call.
+		bucket.Methods("GET").HandlerFunc(httpTraceAll(api.GetBucketACLHandler)).Queries("acl", "")
+
 		// GetBucketNotification
 		bucket.Methods("GET").HandlerFunc(httpTraceAll(api.GetBucketNotificationHandler)).Queries("notification", "")
 		// ListenBucketNotification

cmd/generic-handlers.go

@@ -420,6 +420,11 @@ func setIgnoreResourcesHandler(h http.Handler) http.Handler {
 // Checks requests for not implemented Bucket resources
 func ignoreNotImplementedBucketResources(req *http.Request) bool {
 	for name := range req.URL.Query() {
+		// Enable GetBucketACL dummy call specifically.
+		if name == "acl" && req.Method == http.MethodGet {
+			return false
+		}
+
 		if notimplementedBucketResourceNames[name] {
 			return true
 		}
@@ -430,6 +435,10 @@ func ignoreNotImplementedBucketResources(req *http.Request) bool {
 // Checks requests for not implemented Object resources
 func ignoreNotImplementedObjectResources(req *http.Request) bool {
 	for name := range req.URL.Query() {
+		// Enable GetObjectACL dummy call specifically.
+		if name == "acl" && req.Method == http.MethodGet {
+			return false
+		}
 		if notimplementedObjectResourceNames[name] {
 			return true
 		}