libgocryptfs/internal/syscallcompat/open_nofollow.go
Jakob Unterwurzacher af4c1fb7a3 syscallcompat: retry ops on EINTR
Retry operations that have been shown to throw EINTR
errors on CIFS.

Todo: Solution for this pain in the back:

	warning: unix.Getdents returned errno 2 in the middle of data
	rm: cannot remove 'linux-3.0.old3/Documentation/ABI/removed': Input/output error

Progress towards fixing https://github.com/rfjakob/gocryptfs/issues/483 .
2020-10-14 00:35:16 +02:00

52 lines
1.5 KiB
Go

package syscallcompat
import (
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// OpenDirNofollow opens the dir at "relPath" in a way that is secure against
// symlink attacks. Symlinks that are part of "relPath" are never followed.
// This function is implemented by walking the directory tree, starting at
// "baseDir", using the Openat syscall with the O_NOFOLLOW flag.
// Symlinks that are part of the "baseDir" path are followed.
// Retries on EINTR.
func OpenDirNofollow(baseDir string, relPath string) (fd int, err error) {
if !filepath.IsAbs(baseDir) {
tlog.Warn.Printf("BUG: OpenDirNofollow called with relative baseDir=%q", baseDir)
return -1, syscall.EINVAL
}
if filepath.IsAbs(relPath) {
tlog.Warn.Printf("BUG: OpenDirNofollow called with absolute relPath=%q", relPath)
return -1, syscall.EINVAL
}
// Open the base dir (following symlinks)
dirfd, err := retryEINTR2(func() (int, error) {
return syscall.Open(baseDir, syscall.O_DIRECTORY|O_PATH, 0)
})
if err != nil {
return -1, err
}
// Caller wanted to open baseDir itself?
if relPath == "" {
return dirfd, nil
}
// Split the path into components
parts := strings.Split(relPath, "/")
// Walk the directory tree
var dirfd2 int
for _, name := range parts {
dirfd2, err = Openat(dirfd, name, syscall.O_NOFOLLOW|syscall.O_DIRECTORY|O_PATH, 0)
syscall.Close(dirfd)
if err != nil {
return -1, err
}
dirfd = dirfd2
}
// Return fd to final directory
return dirfd, nil
}