184 lines
5.7 KiB
Markdown
184 lines
5.7 KiB
Markdown
<!-- [metadata]>
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+++
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title = "AppArmor security profiles for Docker"
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description = "Enabling AppArmor in Docker"
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keywords = ["AppArmor, security, docker, documentation"]
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[menu.main]
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parent= "smn_secure_docker"
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weight=5
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+++
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<![end-metadata]-->
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# AppArmor security profiles for Docker
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AppArmor (Application Armor) is a Linux security module that protects an
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operating system and its applications from security threats. To use it, a system
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administrator associates an AppArmor security profile with each program. Docker
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expects to find an AppArmor policy loaded and enforced.
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Docker automatically loads container profiles. The Docker binary installs
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a `docker-default` profile in the `/etc/apparmor.d/docker` file. This profile
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is used on containers, _not_ on the Docker Daemon.
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A profile for the Docker Engine Daemon exists but it is not currently installed
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with the deb packages. If you are interested in the source for the Daemon
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profile, it is located in
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[contrib/apparmor](https://github.com/docker/docker/tree/master/contrib/apparmor)
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in the Docker Engine source repository.
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## Understand the policies
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The `docker-default` profile is the default for running containers. It is
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moderately protective while providing wide application compatibility. The
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profile is the following:
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```
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#include <tunables/global>
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profile docker-default flags=(attach_disconnected,mediate_deleted) {
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#include <abstractions/base>
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network,
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capability,
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file,
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umount,
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deny @{PROC}/{*,**^[0-9*],sys/kernel/shm*} wkx,
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deny @{PROC}/sysrq-trigger rwklx,
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deny @{PROC}/mem rwklx,
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deny @{PROC}/kmem rwklx,
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deny @{PROC}/kcore rwklx,
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deny mount,
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deny /sys/[^f]*/** wklx,
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deny /sys/f[^s]*/** wklx,
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deny /sys/fs/[^c]*/** wklx,
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deny /sys/fs/c[^g]*/** wklx,
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deny /sys/fs/cg[^r]*/** wklx,
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deny /sys/firmware/efi/efivars/** rwklx,
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deny /sys/kernel/security/** rwklx,
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}
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```
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When you run a container, it uses the `docker-default` policy unless you
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override it with the `security-opt` option. For example, the following
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explicitly specifies the default policy:
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```bash
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$ docker run --rm -it --security-opt apparmor=docker-default hello-world
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```
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## Loading and Unloading Profiles
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To load a new profile into AppArmor, for use with containers:
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```
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$ apparmor_parser -r -W /path/to/your_profile
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```
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Then you can run the custom profile with `--security-opt` like so:
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```bash
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$ docker run --rm -it --security-opt apparmor=your_profile hello-world
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```
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To unload a profile from AppArmor:
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```bash
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# stop apparmor
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$ /etc/init.d/apparmor stop
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# unload the profile
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$ apparmor_parser -R /path/to/profile
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# start apparmor
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$ /etc/init.d/apparmor start
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```
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## Debugging AppArmor
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### Using `dmesg`
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Here are some helpful tips for debugging any problems you might be facing with
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regard to AppArmor.
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AppArmor sends quite verbose messaging to `dmesg`. Usually an AppArmor line
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will look like the following:
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```
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[ 5442.864673] audit: type=1400 audit(1453830992.845:37): apparmor="ALLOWED" operation="open" profile="/usr/bin/docker" name="/home/jessie/docker/man/man1/docker-attach.1" pid=10923 comm="docker" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
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```
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In the above example, the you can see `profile=/usr/bin/docker`. This means the
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user has the `docker-engine` (Docker Engine Daemon) profile loaded.
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> **Note:** On version of Ubuntu > 14.04 this is all fine and well, but Trusty
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> users might run into some issues when trying to `docker exec`.
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Let's look at another log line:
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```
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[ 3256.689120] type=1400 audit(1405454041.341:73): apparmor="DENIED" operation="ptrace" profile="docker-default" pid=17651 comm="docker" requested_mask="receive" denied_mask="receive"
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```
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This time the profile is `docker-default`, which is run on containers by
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default unless in `privileged` mode. It is telling us, that apparmor has denied
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`ptrace` in the container. This is great.
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### Using `aa-status`
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If you need to check which profiles are loaded you can use `aa-status`. The
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output looks like:
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```bash
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$ sudo aa-status
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apparmor module is loaded.
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14 profiles are loaded.
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1 profiles are in enforce mode.
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docker-default
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13 profiles are in complain mode.
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/usr/bin/docker
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/usr/bin/docker///bin/cat
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/usr/bin/docker///bin/ps
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/usr/bin/docker///sbin/apparmor_parser
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/usr/bin/docker///sbin/auplink
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/usr/bin/docker///sbin/blkid
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/usr/bin/docker///sbin/iptables
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/usr/bin/docker///sbin/mke2fs
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/usr/bin/docker///sbin/modprobe
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/usr/bin/docker///sbin/tune2fs
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/usr/bin/docker///sbin/xtables-multi
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/usr/bin/docker///sbin/zfs
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/usr/bin/docker///usr/bin/xz
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38 processes have profiles defined.
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37 processes are in enforce mode.
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docker-default (6044)
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...
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docker-default (31899)
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1 processes are in complain mode.
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/usr/bin/docker (29756)
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0 processes are unconfined but have a profile defined.
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```
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In the above output you can tell that the `docker-default` profile running on
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various container PIDs is in `enforce` mode. This means AppArmor will actively
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block and audit in `dmesg` anything outside the bounds of the `docker-default`
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profile.
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The output above also shows the `/usr/bin/docker` (Docker Engine Daemon)
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profile is running in `complain` mode. This means AppArmor will _only_ log to
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`dmesg` activity outside the bounds of the profile. (Except in the case of
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Ubuntu Trusty, where we have seen some interesting behaviors being enforced.)
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## Contributing to AppArmor code in Docker
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Advanced users and package managers can find a profile for `/usr/bin/docker`
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(Docker Engine Daemon) underneath
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[contrib/apparmor](https://github.com/docker/docker/tree/master/contrib/apparmor)
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in the Docker Engine source repository.
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The `docker-default` profile for containers lives in
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[profiles/apparmor](https://github.com/docker/docker/tree/master/profiles/apparmor).
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