1 files changed, 30 insertions, 0 deletions
diff --git a/internal/lfsutil/oid.go b/internal/lfsutil/oid.go
new file mode 100644
index 00000000..899c7332
--- /dev/null
+++ b/internal/lfsutil/oid.go
@@ -0,0 +1,30 @@
+// Copyright 2020 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package lfsutil
+
+import (
+	"strings"
+)
+
+// OID is an LFS object ID.
+type OID string
+
+// ValidOID returns true if given oid is valid according to spec:
+// https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
+func ValidOID(oid OID) bool {
+	fields := strings.SplitN(string(oid), ":", 2)
+	if len(fields) != 2 {
+		return false
+	}
+	method := fields[0]
+	hash := fields[1]
+
+	switch method {
+	case "sha256":
+		// SHA256 produces 64-char lower case hexadecimal hash
+		return len(hash) == 64 && strings.ToLower(hash) == hash
+	}
+	return false
+}