fix: support LDAP settings properly in ftp/sftp (#17536)

Bonus this PR enhances and supports creating
buckets via ftp `mkdir`

fixes #17526

cmd/ftp-server-driver.go

@@ -253,11 +253,7 @@ func (driver *ftpDriver) CheckPasswd(c *ftp.Context, username, password string)
 			return false, err
 		}
 		ldapPolicies, _ := globalIAMSys.PolicyDBGet(ldapUserDN, false, groupDistNames...)
-		if len(ldapPolicies) == 0 {
-			// no policy associated reject it.
-			return false, nil
-		}
-		return true, nil
+		return len(ldapPolicies) > 0, nil
 	}
 
 	ui, ok := globalIAMSys.GetUser(context.Background(), username)
@@ -362,12 +358,20 @@ func (driver *ftpDriver) DeleteDir(ctx *ftp.Context, path string) (err error) {
 	cctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
+	if prefix == "" {
+		// if all objects are not deleted yet this call may fail.
+		return clnt.RemoveBucket(cctx, bucket)
+	}
+
 	objectsCh := make(chan minio.ObjectInfo)
 
 	// Send object names that are needed to be removed to objectsCh
 	go func() {
 		defer close(objectsCh)
-		opts := minio.ListObjectsOptions{Prefix: prefix, Recursive: true}
+		opts := minio.ListObjectsOptions{
+			Prefix:    prefix,
+			Recursive: true,
+		}
 		for object := range clnt.ListObjects(cctx, bucket, opts) {
 			if object.Err != nil {
 				return
@@ -427,6 +431,10 @@ func (driver *ftpDriver) MakeDir(ctx *ftp.Context, path string) (err error) {
 		return err
 	}
 
+	if prefix == "" {
+		return clnt.MakeBucket(context.Background(), bucket, minio.MakeBucketOptions{Region: globalSite.Region})
+	}
+
 	dirPath := buildMinioDir(prefix)
 
 	_, err = clnt.PutObject(context.Background(), bucket, dirPath, bytes.NewReader([]byte("")), 0,