Cleanup and fixes (#3273)

* newRequestID() (previously generateUploadID()) returns string than byte array.
* Remove unclear comments and added appropriate comments.
* SHA-256, MD5 Hash functions return Hex/Base64 encoded string than byte array.
* Remove duplicate MD5 hasher functions.
* Rename listObjectsValidateArgs() into validateListObjectsArgs()
* Remove repeated auth check code in all bucket request handlers.
* Remove abbreviated names in bucket-metadata
* Avoid nested if in bucketPolicyMatchStatement()
* Use ioutil.ReadFile() instead of os.Open() and ioutil.ReadAll()
* Set crossDomainXML as constant.

cmd/event-notifier.go

@@ -18,7 +18,6 @@ package cmd
 
 import (
 	"bytes"
-	"encoding/hex"
 	"encoding/json"
 	"encoding/xml"
 	"fmt"
@@ -401,7 +400,7 @@ func persistNotificationConfig(bucket string, ncfg *notificationConfig, obj Obje
 	// build path
 	ncPath := path.Join(bucketConfigPrefix, bucket, bucketNotificationConfig)
 	// write object to path
-	sha256Sum := hex.EncodeToString(sum256(buf))
+	sha256Sum := getSHA256Hash(buf)
 	_, err = obj.PutObject(minioMetaBucket, ncPath, int64(len(buf)), bytes.NewReader(buf), nil, sha256Sum)
 	if err != nil {
 		errorIf(err, "Unable to write bucket notification configuration.")
@@ -421,7 +420,7 @@ func persistListenerConfig(bucket string, lcfg []listenerConfig, obj ObjectLayer
 	// build path
 	lcPath := path.Join(bucketConfigPrefix, bucket, bucketListenerConfig)
 	// write object to path
-	sha256Sum := hex.EncodeToString(sum256(buf))
+	sha256Sum := getSHA256Hash(buf)
 	_, err = obj.PutObject(minioMetaBucket, lcPath, int64(len(buf)), bytes.NewReader(buf), nil, sha256Sum)
 	if err != nil {
 		errorIf(err, "Unable to write bucket listener configuration to object layer.")