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Make /proc, /sys, /dev readonly for readonly containers

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If a container is read-only, also set /proc, /sys,
& /dev to read-only. This should apply to both privileged and
unprivileged containers.

Note that when /dev is read-only, device files may still be
written to. This change will simply prevent the device paths
from being modified, or performing mknod of new devices within
the /dev path.

Tests are included for all cases. Also adds a test to ensure
that /dev/pts is always mounted read/write, even in the case of a
read-write rootfs. The kernel restricts writes here naturally and
bad things will happen if we mount it ro.

Signed-off-by: Eric Windisch <eric@windisch.us>
This commit is contained in:
Eric Windisch 2015-06-02 12:16:43 -04:00
parent f58758ce36
commit 5400d8873f
2 changed files with 45 additions and 6 deletions
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26
daemon/execdriver/native/create.go
View file

@ -38,13 +38,16 @@ func (d *driver) createContainer(c *execdriver.Command) (*configs.Config, error)
}
if c.ProcessConfig.Privileged {
// clear readonly for /sys
for i := range container.Mounts {
if container.Mounts[i].Destination == "/sys" {
container.Mounts[i].Flags &= ^syscall.MS_RDONLY
if !container.Readonlyfs {
// clear readonly for /sys
for i := range container.Mounts {
if container.Mounts[i].Destination == "/sys" {
container.Mounts[i].Flags &= ^syscall.MS_RDONLY
}
}
container.ReadonlyPaths = nil
}
container.ReadonlyPaths = nil
container.MaskPaths = nil
if err := d.setPrivileged(container); err != nil {
return nil, err
@ -63,6 +66,19 @@ func (d *driver) createContainer(c *execdriver.Command) (*configs.Config, error)
return nil, err
}
if container.Readonlyfs {
for i := range container.Mounts {
switch container.Mounts[i].Destination {
case "/proc", "/dev", "/dev/pts":
continue
}
container.Mounts[i].Flags |= syscall.MS_RDONLY
}
/* These paths must be remounted as r/o */
container.ReadonlyPaths = append(container.ReadonlyPaths, "/proc", "/dev")
}
if err := d.setupMounts(container, c); err != nil {
return nil, err
}

25
integration-cli/docker_cli_run_test.go
View file

@ -2944,11 +2944,25 @@ func (s *DockerSuite) TestRunContainerWithWritableRootfs(c *check.C) {
func (s *DockerSuite) TestRunContainerWithReadonlyRootfs(c *check.C) {
testRequires(c, NativeExecDriver)
for _, f := range []string{"/file", "/etc/hosts", "/etc/resolv.conf", "/etc/hostname"} {
for _, f := range []string{"/file", "/etc/hosts", "/etc/resolv.conf", "/etc/hostname", "/proc/uptime", "/sys/kernel", "/dev/.dont.touch.me"} {
testReadOnlyFile(f, c)
}
}
func (s *DockerSuite) TestPermissionsPtsReadonlyRootfs(c *check.C) {
testRequires(c, NativeExecDriver)
// Ensure we have not broken writing /dev/pts
out, status := dockerCmd(c, "run", "--read-only", "--rm", "busybox", "mount")
if status != 0 {
c.Fatal("Could not obtain mounts when checking /dev/pts mntpnt.")
}
expected := "type devpts (rw,"
if !strings.Contains(string(out), expected) {
c.Fatalf("expected output to contain %s but contains %s", expected, out)
}
}
func testReadOnlyFile(filename string, c *check.C) {
testRequires(c, NativeExecDriver)
@ -2960,6 +2974,15 @@ func testReadOnlyFile(filename string, c *check.C) {
if !strings.Contains(string(out), expected) {
c.Fatalf("expected output from failure to contain %s but contains %s", expected, out)
}
out, err = exec.Command(dockerBinary, "run", "--read-only", "--privileged", "--rm", "busybox", "touch", filename).CombinedOutput()
if err == nil {
c.Fatal("expected container to error on run with read only error")
}
expected = "Read-only file system"
if !strings.Contains(string(out), expected) {
c.Fatalf("expected output from failure to contain %s but contains %s", expected, out)
}
}
func (s *DockerSuite) TestRunContainerWithReadonlyEtcHostsAndLinkedContainer(c *check.C) {