1 files changed, 60 insertions, 23 deletions

diff --git a/filesystem/path.go b/filesystem/path.go
index d788a6b..8cfb235 100644
--- a/filesystem/path.go
+++ b/filesystem/path.go
@@ -20,18 +20,26 @@
 package filesystem
 
 import (
+	"fmt"
 	"log"
 	"os"
 	"path/filepath"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/pkg/errors"
 )
 
-// We only check the unix permissions and the sticky bit
-const permMask = os.ModeSticky | os.ModePerm
+// OpenFileOverridingUmask calls os.OpenFile but with the umask overridden so
+// that no permission bits are masked out if the file is created.
+func OpenFileOverridingUmask(name string, flag int, perm os.FileMode) (*os.File, error) {
+	oldMask := unix.Umask(0)
+	defer unix.Umask(oldMask)
+	return os.OpenFile(name, flag, perm)
+}
 
-// cannonicalizePath turns path into an absolute path without symlinks.
-func cannonicalizePath(path string) (string, error) {
+// canonicalizePath turns path into an absolute path without symlinks.
+func canonicalizePath(path string) (string, error) {
 	path, err := filepath.Abs(path)
 	if err != nil {
 		return "", err
@@ -56,36 +64,65 @@ func loggedStat(name string) (os.FileInfo, error) {
 	return info, err
 }
 
+// loggedLstat runs os.Lstat (doesn't dereference trailing symlink), but it logs
+// the error if lstat returns any error other than nil or IsNotExist.
+func loggedLstat(name string) (os.FileInfo, error) {
+	info, err := os.Lstat(name)
+	if err != nil && !os.IsNotExist(err) {
+		log.Print(err)
+	}
+	return info, err
+}
+
 // isDir returns true if the path exists and is that of a directory.
 func isDir(path string) bool {
 	info, err := loggedStat(path)
 	return err == nil && info.IsDir()
 }
 
-// isDevice returns true if the path exists and is that of a directory.
-func isDevice(path string) bool {
+// isRegularFile returns true if the path exists and is that of a regular file.
+func isRegularFile(path string) bool {
 	info, err := loggedStat(path)
-	return err == nil && info.Mode()&os.ModeDevice != 0
+	return err == nil && info.Mode().IsRegular()
 }
 
-// isDirCheckPerm returns true if the path exists and is a directory. If the
-// specified permissions and sticky bit of mode do not match the path, and error
-// is logged.
-func isDirCheckPerm(path string, mode os.FileMode) bool {
-	info, err := loggedStat(path)
-	// Check if directory
-	if err != nil || !info.IsDir() {
-		return false
+// HaveReadAccessTo returns true if the process has read access to a file or
+// directory, without actually opening it.
+func HaveReadAccessTo(path string) bool {
+	return unix.Access(path, unix.R_OK) == nil
+}
+
+// DeviceNumber represents a combined major:minor device number.
+type DeviceNumber uint64
+
+func (num DeviceNumber) String() string {
+	return fmt.Sprintf("%d:%d", unix.Major(uint64(num)), unix.Minor(uint64(num)))
+}
+
+func newDeviceNumberFromString(str string) (DeviceNumber, error) {
+	var major, minor uint32
+	if count, _ := fmt.Sscanf(str, "%d:%d", &major, &minor); count != 2 {
+		return 0, errors.Errorf("invalid device number string %q", str)
 	}
-	// Check for bad permissions
-	if info.Mode()&permMask != mode&permMask {
-		log.Printf("directory %s has incorrect permissions", path)
+	return DeviceNumber(unix.Mkdev(major, minor)), nil
+}
+
+// getDeviceNumber returns the device number of the device node at the given
+// path.  If there is a symlink at the path, it is dereferenced.
+func getDeviceNumber(path string) (DeviceNumber, error) {
+	var stat unix.Stat_t
+	if err := unix.Stat(path, &stat); err != nil {
+		return 0, err
 	}
-	return true
+	return DeviceNumber(stat.Rdev), nil
 }
 
-// isRegularFile returns true if the path exists and is that of a regular file.
-func isRegularFile(path string) bool {
-	info, err := loggedStat(path)
-	return err == nil && info.Mode().IsRegular()
+// getNumberOfContainingDevice returns the device number of the filesystem which
+// contains the given file.  If the file is a symlink, it is not dereferenced.
+func getNumberOfContainingDevice(path string) (DeviceNumber, error) {
+	var stat unix.Stat_t
+	if err := unix.Lstat(path, &stat); err != nil {
+		return 0, err
+	}
+	return DeviceNumber(stat.Dev), nil
 }