53 lines
1.5 KiB
Go
53 lines
1.5 KiB
Go
// +build linux
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package restrict
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import (
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"fmt"
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"os"
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"syscall"
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"time"
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"github.com/dotcloud/docker/pkg/system"
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)
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const defaultMountFlags = syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NODEV
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func mountReadonly(path string) error {
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for i := 0; i < 5; i++ {
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if err := system.Mount("", path, "", syscall.MS_REMOUNT|syscall.MS_RDONLY, ""); err != nil {
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switch err {
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case syscall.EINVAL:
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// Probably not a mountpoint, use bind-mount
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if err := system.Mount(path, path, "", syscall.MS_BIND, ""); err != nil {
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return err
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}
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return system.Mount(path, path, "", syscall.MS_BIND|syscall.MS_REMOUNT|syscall.MS_RDONLY|syscall.MS_REC|defaultMountFlags, "")
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case syscall.EBUSY:
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time.Sleep(100 * time.Millisecond)
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continue
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default:
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return err
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}
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}
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return nil
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}
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return fmt.Errorf("unable to mount %s as readonly max retries reached", path)
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}
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// This has to be called while the container still has CAP_SYS_ADMIN (to be able to perform mounts).
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// However, afterwards, CAP_SYS_ADMIN should be dropped (otherwise the user will be able to revert those changes).
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func Restrict(mounts ...string) error {
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// remount proc and sys as readonly
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for _, dest := range mounts {
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if err := mountReadonly(dest); err != nil {
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return fmt.Errorf("unable to remount %s readonly: %s", dest, err)
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}
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}
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if err := system.Mount("/dev/null", "/proc/kcore", "", syscall.MS_BIND, ""); err != nil && !os.IsNotExist(err) {
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return fmt.Errorf("unable to bind-mount /dev/null over /proc/kcore: %s", err)
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}
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return nil
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}
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