WIP

tar/verify/xattrs_linux.go

@@ -0,0 +1,114 @@
+package verify
+
+/*
+Lgetxattr and Lsetxattr are copied directly from https://github.com/docker/docker
+  ./pkg/system/xattr_linux.go commit 7e420ad8502089e66ce0ade92bf70574f894f287
+  Apache License Version 2.0, January 2004 https://www.apache.org/licenses/
+  Copyright 2013-2015 Docker, Inc.
+*/
+
+import (
+	"bytes"
+	"syscall"
+	"unsafe"
+)
+
+/*
+func main() {
+	for _, arg := range os.Args[1:] {
+		keys, err := Listxattr(arg)
+		if err != nil {
+			fmt.Println(err)
+			continue
+		}
+		if len(keys) > 0 {
+			fmt.Printf("%s : %q\n", arg, keys)
+			for _, key := range keys {
+				buf, err := Lgetxattr(arg, key)
+				if err != nil {
+					fmt.Printf("  ERROR: %s\n", err)
+					continue
+				}
+				fmt.Printf("  %s = %s\n", key, string(buf))
+			}
+		}
+	}
+}
+*/
+
+// Listxattr is a helper around the syscall.Listxattr
+func Listxattr(path string) ([]string, error) {
+	buf := make([]byte, 1024)
+	sz, err := syscall.Listxattr(path, buf)
+	if err == syscall.ENODATA {
+		return nil, nil
+	}
+	if err == syscall.ERANGE && sz > 0 {
+		buf = make([]byte, sz)
+		sz, err = syscall.Listxattr(path, buf)
+	}
+	keys := []string{}
+	for _, key := range bytes.Split(bytes.TrimSpace(buf), []byte{0x0}) {
+		if string(key) != "" {
+			keys = append(keys, string(key))
+		}
+	}
+	return keys, nil
+}
+
+// Lgetxattr retrieves the value of the extended attribute identified by attr
+// and associated with the given path in the file system.
+// It will returns a nil slice and nil error if the xattr is not set.
+func Lgetxattr(path string, attr string) ([]byte, error) {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return nil, err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return nil, err
+	}
+
+	dest := make([]byte, 128)
+	destBytes := unsafe.Pointer(&dest[0])
+	sz, _, errno := syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+	if errno == syscall.ENODATA {
+		return nil, nil
+	}
+	if errno == syscall.ERANGE {
+		dest = make([]byte, sz)
+		destBytes := unsafe.Pointer(&dest[0])
+		sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+	}
+	if errno != 0 {
+		return nil, errno
+	}
+
+	return dest[:sz], nil
+}
+
+var _zero uintptr
+
+// Lsetxattr sets the value of the extended attribute identified by attr
+// and associated with the given path in the file system.
+func Lsetxattr(path string, attr string, data []byte, flags int) error {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return err
+	}
+	var dataBytes unsafe.Pointer
+	if len(data) > 0 {
+		dataBytes = unsafe.Pointer(&data[0])
+	} else {
+		dataBytes = unsafe.Pointer(&_zero)
+	}
+	_, _, errno := syscall.Syscall6(syscall.SYS_LSETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(dataBytes), uintptr(len(data)), uintptr(flags), 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}