Initial commit

Proof-of-concept implementation. Bugs will occur.

vendor/github.com/hanwen/go-fuse/v2/internal/access.go

@@ -0,0 +1,60 @@
+// Copyright 2019 the Go-FUSE Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package internal
+
+import (
+	"os/user"
+	"strconv"
+)
+
+// HasAccess tests if a caller can access a file with permissions
+// `perm` in mode `mask`
+func HasAccess(callerUid, callerGid, fileUid, fileGid uint32, perm uint32, mask uint32) bool {
+	if callerUid == 0 {
+		// root can do anything.
+		return true
+	}
+	mask = mask & 7
+	if mask == 0 {
+		return true
+	}
+
+	if callerUid == fileUid {
+		if perm&(mask<<6) != 0 {
+			return true
+		}
+	}
+	if callerGid == fileGid {
+		if perm&(mask<<3) != 0 {
+			return true
+		}
+	}
+	if perm&mask != 0 {
+		return true
+	}
+
+	// Check other groups.
+	if perm&(mask<<3) == 0 {
+		// avoid expensive lookup if it's not allowed anyway
+		return false
+	}
+
+	u, err := user.LookupId(strconv.Itoa(int(callerUid)))
+	if err != nil {
+		return false
+	}
+	gs, err := u.GroupIds()
+	if err != nil {
+		return false
+	}
+
+	fileGidStr := strconv.Itoa(int(fileGid))
+	for _, gidStr := range gs {
+		if gidStr == fileGidStr {
+			return true
+		}
+	}
+	return false
+}