66ff12e5f7
* vendor: bump libcontainer and docker to remove Sirupsen imports * vendor: fix bad vendoring of archive package * vendor: fix api changes to cgroups in executor * vendor: fix docker api changes * vendor: update github.com/Azure/go-ansiterm to use non capitalized logrus import
2.1 KiB
filepath-securejoin
An implementation of SecureJoin, a candidate for inclusion in the Go
standard library. The purpose of this function is to be a "secure"
alternative to filepath.Join, and in particular it provides certain
guarantees that are not provided by filepath.Join.
This is the function prototype:
func SecureJoin(root, unsafePath string) (string, error)
This library guarantees the following:
-
If no error is set, the resulting string must be a child path of
SecureJoinand will not contain any symlink path components (they will all be expanded). -
When expanding symlinks, all symlink path components must be resolved relative to the provided root. In particular, this can be considered a userspace implementation of how
chroot(2)operates on file paths. Note that these symlinks will not be expanded lexically (filepath.Cleanis not called on the input before processing). -
Non-existant path components are unaffected by
SecureJoin(similar tofilepath.EvalSymlinks's semantics). -
The returned path will always be
filepath.Cleaned and thus not contain any..components.
A (trivial) implementation of this function on GNU/Linux systems could be done
with the following (note that this requires root privileges and is far more
opaque than the implementation in this library, and also requires that
readlink is inside the root path):
package securejoin
import (
"os/exec"
"path/filepath"
)
func SecureJoin(root, unsafePath string) (string, error) {
unsafePath = string(filepath.Separator) + unsafePath
cmd := exec.Command("chroot", root,
"readlink", "--canonicalize-missing", "--no-newline", unsafePath)
output, err := cmd.CombinedOutput()
if err != nil {
return "", err
}
expanded := string(output)
return filepath.Join(root, expanded), nil
}
License
The license of this project is the same as Go, which is a BSD 3-clause license
available in the LICENSE file.