all/windows: Be case in-sensitive about pattern matching. (#3682)

Resource strings and paths are case insensitive on windows
deployments but if user happens to use upper case instead of
lower case for certain configuration params like bucket
policies and bucket notification config. We might not honor
them which leads to a wrong behavior on windows.

This is windows only behavior, for all other platforms case
is still kept sensitive.

cmd/object-api-utils.go

@@ -22,6 +22,7 @@ import (
 	"io"
 	"path"
 	"regexp"
+	"runtime"
 	"strings"
 	"unicode/utf8"
 
@@ -91,10 +92,10 @@ func IsValidObjectName(object string) bool {
 	if len(object) == 0 {
 		return false
 	}
-	if strings.HasSuffix(object, slashSeparator) {
+	if hasSuffix(object, slashSeparator) {
 		return false
 	}
-	if strings.HasPrefix(object, slashSeparator) {
+	if hasPrefix(object, slashSeparator) {
 		return false
 	}
 	return IsValidObjectPrefix(object)
@@ -159,6 +160,26 @@ func getCompleteMultipartMD5(parts []completePart) (string, error) {
 	return s3MD5, nil
 }
 
+// Prefix matcher string matches prefix in a platform specific way.
+// For example on windows since its case insensitive we are supposed
+// to do case insensitive checks.
+func hasPrefix(s string, prefix string) bool {
+	if runtime.GOOS == "windows" {
+		return strings.HasPrefix(strings.ToLower(s), strings.ToLower(prefix))
+	}
+	return strings.HasPrefix(s, prefix)
+}
+
+// Suffix matcher string matches suffix in a platform specific way.
+// For example on windows since its case insensitive we are supposed
+// to do case insensitive checks.
+func hasSuffix(s string, suffix string) bool {
+	if runtime.GOOS == "windows" {
+		return strings.HasSuffix(strings.ToLower(s), strings.ToLower(suffix))
+	}
+	return strings.HasSuffix(s, suffix)
+}
+
 // byBucketName is a collection satisfying sort.Interface.
 type byBucketName []BucketInfo