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archive: prevent breakout in Untar

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Signed-off-by: Tibor Vass <teabee89@gmail.com>
This commit is contained in:
Tibor Vass 2014-10-20 15:36:28 -04:00 committed by unclejack
parent 1752a203af
commit aa62eca940
2 changed files with 24 additions and 2 deletions
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22
archive/archive.go
View file

@ -22,6 +22,7 @@ import (
"github.com/docker/docker/pkg/fileutils"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/promise"
"github.com/docker/docker/pkg/symlink"
"github.com/docker/docker/pkg/system"
)
@ -292,11 +293,23 @@ func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, L
}
case tar.TypeLink:
if err := os.Link(filepath.Join(extractDir, hdr.Linkname), path); err != nil {
targetPath := filepath.Join(extractDir, hdr.Linkname)
// check for hardlink breakout
if !strings.HasPrefix(targetPath, extractDir) {
return breakoutError(fmt.Errorf("invalid hardlink %q -> %q", targetPath, hdr.Linkname))
}
if err := os.Link(targetPath, path); err != nil {
return err
}
case tar.TypeSymlink:
// check for symlink breakout
if _, err := symlink.FollowSymlinkInScope(filepath.Join(filepath.Dir(path), hdr.Linkname), extractDir); err != nil {
if _, ok := err.(symlink.ErrBreakout); ok {
return breakoutError(fmt.Errorf("invalid symlink %q -> %q", path, hdr.Linkname))
}
return err
}
if err := os.Symlink(hdr.Linkname, path); err != nil {
return err
}
@ -456,6 +469,8 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
// identity (uncompressed), gzip, bzip2, xz.
// FIXME: specify behavior when target path exists vs. doesn't exist.
func Untar(archive io.Reader, dest string, options *TarOptions) error {
dest = filepath.Clean(dest)
if options == nil {
options = &TarOptions{}
}
@ -493,6 +508,7 @@ loop:
}
// Normalize name, for safety and for a simple is-root check
// This keeps "../" as-is, but normalizes "/../" to "/"
hdr.Name = filepath.Clean(hdr.Name)
for _, exclude := range options.Excludes {
@ -513,7 +529,11 @@ loop:
}
}
// Prevent symlink breakout
path := filepath.Join(dest, hdr.Name)
if !strings.HasPrefix(path, dest) {
return breakoutError(fmt.Errorf("%q is outside of %q", path, dest))
}
// If path exits we almost always just want to remove and replace it
// The only exception is when it is a directory *and* the file from

4
symlink/fs.go
View file

@ -10,6 +10,8 @@ import (
const maxLoopCounter = 100
type ErrBreakout error
// FollowSymlink will follow an existing link and scope it to the root
// path provided.
// The role of this function is to return an absolute path in the root
@ -34,7 +36,7 @@ func FollowSymlinkInScope(link, root string) (string, error) {
}
if !strings.HasPrefix(filepath.Dir(link), root) {
return "", fmt.Errorf("%s is not within %s", link, root)
return "", ErrBreakout(fmt.Errorf("%s is not within %s", link, root))
}
prev := "/"