From af5420420bc8437e9c2cbf6efc0a0c1a7f8aa361 Mon Sep 17 00:00:00 2001 From: Michael Crosby Date: Thu, 1 May 2014 10:08:18 -0700 Subject: [PATCH] Update restrictions for better handling of mounts This also cleans up some of the left over restriction paths code from before. Docker-DCO-1.1-Signed-off-by: Michael Crosby (github: crosbymichael) --- libcontainer/mount/init.go | 7 +- libcontainer/nsinit/init.go | 4 +- libcontainer/security/restrict/restrict.go | 65 ++++++------------- libcontainer/security/restrict/unsupported.go | 2 +- 4 files changed, 25 insertions(+), 53 deletions(-) diff --git a/libcontainer/mount/init.go b/libcontainer/mount/init.go index cc3ce21..6a54f24 100644 --- a/libcontainer/mount/init.go +++ b/libcontainer/mount/init.go @@ -123,15 +123,12 @@ func newSystemMounts(rootfs, mountLabel string, mounts libcontainer.Mounts) []mo systemMounts := []mount{ {source: "proc", path: filepath.Join(rootfs, "proc"), device: "proc", flags: defaultMountFlags}, {source: "sysfs", path: filepath.Join(rootfs, "sys"), device: "sysfs", flags: defaultMountFlags}, + {source: "shm", path: filepath.Join(rootfs, "dev", "shm"), device: "tmpfs", flags: defaultMountFlags, data: label.FormatMountLabel("mode=1777,size=65536k", mountLabel)}, + {source: "devpts", path: filepath.Join(rootfs, "dev", "pts"), device: "devpts", flags: syscall.MS_NOSUID | syscall.MS_NOEXEC, data: label.FormatMountLabel("newinstance,ptmxmode=0666,mode=620,gid=5", mountLabel)}, } if len(mounts.OfType("devtmpfs")) == 1 { systemMounts = append(systemMounts, mount{source: "tmpfs", path: filepath.Join(rootfs, "dev"), device: "tmpfs", flags: syscall.MS_NOSUID | syscall.MS_STRICTATIME, data: label.FormatMountLabel("mode=755", mountLabel)}) } - systemMounts = append(systemMounts, - mount{source: "shm", path: filepath.Join(rootfs, "dev", "shm"), device: "tmpfs", flags: defaultMountFlags, data: label.FormatMountLabel("mode=1777,size=65536k", mountLabel)}, - mount{source: "devpts", path: filepath.Join(rootfs, "dev", "pts"), device: "devpts", flags: syscall.MS_NOSUID | syscall.MS_NOEXEC, data: label.FormatMountLabel("newinstance,ptmxmode=0666,mode=620,gid=5", mountLabel)}, - ) - return systemMounts } diff --git a/libcontainer/nsinit/init.go b/libcontainer/nsinit/init.go index 90b97a9..7558479 100644 --- a/libcontainer/nsinit/init.go +++ b/libcontainer/nsinit/init.go @@ -72,8 +72,8 @@ func Init(container *libcontainer.Container, uncleanRootfs, consolePath string, runtime.LockOSThread() - if restrictionPath := container.Context["restriction_path"]; restrictionPath != "" { - if err := restrict.Restrict("/", restrictionPath); err != nil { + if container.Context["restrictions"] != "" { + if err := restrict.Restrict(); err != nil { return err } } diff --git a/libcontainer/security/restrict/restrict.go b/libcontainer/security/restrict/restrict.go index a9bdc4b..2b7cea5 100644 --- a/libcontainer/security/restrict/restrict.go +++ b/libcontainer/security/restrict/restrict.go @@ -11,67 +11,42 @@ import ( "github.com/dotcloud/docker/pkg/system" ) -// "restrictions" are container paths (files, directories, whatever) that have to be masked. -// maskPath is a "safe" path to be mounted over maskedPath. It can take two special values: -// - if it is "", then nothing is mounted; -// - if it is "EMPTY", then an empty directory is mounted instead. -// If remountRO is true then the maskedPath is remounted read-only (regardless of whether a maskPath was used). -type restriction struct { - maskedPath string - maskPath string - remountRO bool -} - -var restrictions = []restriction{ - {"/proc", "", true}, - {"/sys", "", true}, - {"/proc/kcore", "/dev/null", false}, -} - // This has to be called while the container still has CAP_SYS_ADMIN (to be able to perform mounts). // However, afterwards, CAP_SYS_ADMIN should be dropped (otherwise the user will be able to revert those changes). -// "empty" should be the path to an empty directory. -func Restrict(rootfs, empty string) error { - for _, restriction := range restrictions { - dest := filepath.Join(rootfs, restriction.maskedPath) - if restriction.maskPath != "" { - var source string - if restriction.maskPath == "EMPTY" { - source = empty - } else { - source = filepath.Join(rootfs, restriction.maskPath) - } - if err := system.Mount(source, dest, "", syscall.MS_BIND, ""); err != nil { - return fmt.Errorf("unable to bind-mount %s over %s: %s", source, dest, err) - } - } - if restriction.remountRO { - if err := system.Mount("", dest, "", syscall.MS_REMOUNT|syscall.MS_RDONLY, ""); err != nil { - return fmt.Errorf("unable to remount %s readonly: %s", dest, err) - } +func Restrict() error { + // remount proc and sys as readonly + for _, dest := range []string{"proc", "sys"} { + if err := system.Mount("", dest, "", syscall.MS_REMOUNT|syscall.MS_RDONLY, ""); err != nil { + return fmt.Errorf("unable to remount %s readonly: %s", dest, err) } } + if err := system.Mount("/proc/kcore", "/dev/null", "", syscall.MS_BIND, ""); err != nil { + return fmt.Errorf("unable to bind-mount /dev/null over /proc/kcore") + } + // This weird trick will allow us to mount /proc read-only, while being able to use AppArmor. // This is because apparently, loading an AppArmor profile requires write access to /proc/1/attr. // So we do another mount of procfs, ensure it's write-able, and bind-mount a subset of it. - tmpProcPath := filepath.Join(rootfs, ".proc") - if err := os.Mkdir(tmpProcPath, 0700); err != nil { - return fmt.Errorf("unable to create temporary proc mountpoint %s: %s", tmpProcPath, err) + var ( + rwAttrPath = filepath.Join(".proc", "1", "attr") + roAttrPath = filepath.Join("proc", "1", "attr") + ) + + if err := os.Mkdir(".proc", 0700); err != nil { + return fmt.Errorf("unable to create temporary proc mountpoint .proc: %s", err) } - if err := system.Mount("proc", tmpProcPath, "proc", 0, ""); err != nil { + if err := system.Mount("proc", ".proc", "proc", 0, ""); err != nil { return fmt.Errorf("unable to mount proc on temporary proc mountpoint: %s", err) } - if err := system.Mount("proc", tmpProcPath, "", syscall.MS_REMOUNT, ""); err != nil { + if err := system.Mount("proc", ".proc", "", syscall.MS_REMOUNT, ""); err != nil { return fmt.Errorf("unable to remount proc read-write: %s", err) } - rwAttrPath := filepath.Join(rootfs, ".proc", "1", "attr") - roAttrPath := filepath.Join(rootfs, "proc", "1", "attr") if err := system.Mount(rwAttrPath, roAttrPath, "", syscall.MS_BIND, ""); err != nil { return fmt.Errorf("unable to bind-mount %s on %s: %s", rwAttrPath, roAttrPath, err) } - if err := system.Unmount(tmpProcPath, 0); err != nil { + if err := system.Unmount(".proc", 0); err != nil { return fmt.Errorf("unable to unmount temporary proc filesystem: %s", err) } - return nil + return os.RemoveAll(".proc") } diff --git a/libcontainer/security/restrict/unsupported.go b/libcontainer/security/restrict/unsupported.go index 6898baa..464e8d4 100644 --- a/libcontainer/security/restrict/unsupported.go +++ b/libcontainer/security/restrict/unsupported.go @@ -4,6 +4,6 @@ package restrict import "fmt" -func Restrict(rootfs, empty string) error { +func Restrict() error { return fmt.Errorf("not supported") }