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moby--moby/oci/defaults.go
Jonathan A. Schweder 64e52ff3db Masked /proc/asound
@sw-pschmied originally post this in #38285

While looking through the Moby source code was found /proc/asound to be
shared with containers as read-only (as defined in
https://github.com/moby/moby/blob/master/oci/defaults.go#L128).

This can lead to two information leaks.

---

**Leak of media playback status of the host**

Steps to reproduce the issue:

 - Listen to music/Play a YouTube video/Do anything else that involves
sound output
 - Execute docker run --rm ubuntu:latest bash -c "sleep 7; cat
/proc/asound/card*/pcm*p/sub*/status | grep state | cut -d ' ' -f2 |
grep RUNNING || echo 'not running'"
 - See that the containerized process is able to check whether someone
on the host is playing music as it prints RUNNING
 - Stop the music output
 - Execute the command again (The sleep is delaying the output because
information regarding playback status isn't propagated instantly)
 - See that it outputs not running

**Describe the results you received:**

A containerized process is able to gather information on the playback
status of an audio device governed by the host. Therefore a process of a
container is able to check whether and what kind of user activity is
present on the host system. Also, this may indicate whether a container
runs on a desktop system or a server as media playback rarely happens on
server systems.

The description above is in regard to media playback - when examining
`/proc/asound/card*/pcm*c/sub*/status` (`pcm*c` instead of `pcm*p`) this
can also leak information regarding capturing sound, as in recording
audio or making calls on the host system.

Signed-off-by: Jonathan A. Schweder <jonathanschweder@gmail.com>
2018-11-30 10:03:10 -02:00

212 lines
4.6 KiB
Go

package oci // import "github.com/docker/docker/oci"
import (
"os"
"runtime"
"github.com/opencontainers/runtime-spec/specs-go"
)
func iPtr(i int64) *int64 { return &i }
func u32Ptr(i int64) *uint32 { u := uint32(i); return &u }
func fmPtr(i int64) *os.FileMode { fm := os.FileMode(i); return &fm }
func defaultCapabilities() []string {
return []string{
"CAP_CHOWN",
"CAP_DAC_OVERRIDE",
"CAP_FSETID",
"CAP_FOWNER",
"CAP_MKNOD",
"CAP_NET_RAW",
"CAP_SETGID",
"CAP_SETUID",
"CAP_SETFCAP",
"CAP_SETPCAP",
"CAP_NET_BIND_SERVICE",
"CAP_SYS_CHROOT",
"CAP_KILL",
"CAP_AUDIT_WRITE",
}
}
// DefaultSpec returns the default spec used by docker for the current Platform
func DefaultSpec() specs.Spec {
return DefaultOSSpec(runtime.GOOS)
}
// DefaultOSSpec returns the spec for a given OS
func DefaultOSSpec(osName string) specs.Spec {
if osName == "windows" {
return DefaultWindowsSpec()
}
return DefaultLinuxSpec()
}
// DefaultWindowsSpec create a default spec for running Windows containers
func DefaultWindowsSpec() specs.Spec {
return specs.Spec{
Version: specs.Version,
Windows: &specs.Windows{},
Process: &specs.Process{},
Root: &specs.Root{},
}
}
// DefaultLinuxSpec create a default spec for running Linux containers
func DefaultLinuxSpec() specs.Spec {
s := specs.Spec{
Version: specs.Version,
Process: &specs.Process{
Capabilities: &specs.LinuxCapabilities{
Bounding: defaultCapabilities(),
Permitted: defaultCapabilities(),
Inheritable: defaultCapabilities(),
Effective: defaultCapabilities(),
},
},
Root: &specs.Root{},
}
s.Mounts = []specs.Mount{
{
Destination: "/proc",
Type: "proc",
Source: "proc",
Options: []string{"nosuid", "noexec", "nodev"},
},
{
Destination: "/dev",
Type: "tmpfs",
Source: "tmpfs",
Options: []string{"nosuid", "strictatime", "mode=755", "size=65536k"},
},
{
Destination: "/dev/pts",
Type: "devpts",
Source: "devpts",
Options: []string{"nosuid", "noexec", "newinstance", "ptmxmode=0666", "mode=0620", "gid=5"},
},
{
Destination: "/sys",
Type: "sysfs",
Source: "sysfs",
Options: []string{"nosuid", "noexec", "nodev", "ro"},
},
{
Destination: "/sys/fs/cgroup",
Type: "cgroup",
Source: "cgroup",
Options: []string{"ro", "nosuid", "noexec", "nodev"},
},
{
Destination: "/dev/mqueue",
Type: "mqueue",
Source: "mqueue",
Options: []string{"nosuid", "noexec", "nodev"},
},
{
Destination: "/dev/shm",
Type: "tmpfs",
Source: "shm",
Options: []string{"nosuid", "noexec", "nodev", "mode=1777"},
},
}
s.Linux = &specs.Linux{
MaskedPaths: []string{
"/proc/asound",
"/proc/acpi",
"/proc/kcore",
"/proc/keys",
"/proc/latency_stats",
"/proc/timer_list",
"/proc/timer_stats",
"/proc/sched_debug",
"/proc/scsi",
"/sys/firmware",
},
ReadonlyPaths: []string{
"/proc/bus",
"/proc/fs",
"/proc/irq",
"/proc/sys",
"/proc/sysrq-trigger",
},
Namespaces: []specs.LinuxNamespace{
{Type: "mount"},
{Type: "network"},
{Type: "uts"},
{Type: "pid"},
{Type: "ipc"},
},
// Devices implicitly contains the following devices:
// null, zero, full, random, urandom, tty, console, and ptmx.
// ptmx is a bind mount or symlink of the container's ptmx.
// See also: https://github.com/opencontainers/runtime-spec/blob/master/config-linux.md#default-devices
Devices: []specs.LinuxDevice{},
Resources: &specs.LinuxResources{
Devices: []specs.LinuxDeviceCgroup{
{
Allow: false,
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(1),
Minor: iPtr(5),
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(1),
Minor: iPtr(3),
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(1),
Minor: iPtr(9),
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(1),
Minor: iPtr(8),
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(5),
Minor: iPtr(0),
Access: "rwm",
},
{
Allow: true,
Type: "c",
Major: iPtr(5),
Minor: iPtr(1),
Access: "rwm",
},
{
Allow: false,
Type: "c",
Major: iPtr(10),
Minor: iPtr(229),
Access: "rwm",
},
},
},
}
// For LCOW support, populate a blank Windows spec
if runtime.GOOS == "windows" {
s.Windows = &specs.Windows{}
}
return s
}