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https://issues.apache.org/jira/browse/YARN-7197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16225452#comment-16225452
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Eric Yang commented on YARN-7197:
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[~jlowe]
{quote}Either /run isn't in the whitelist in the first place rendering the
blacklist entry moot or /run is in the whitelist and the user can simply mount
/run and access the blacklist path.{quote}
Let's expand on the real world example. A hacker tries to take control of
{{/run/docker.socket}} to acquire root privileges and spawn root containers to
access vital system area to become root on the host system. The system admin
placed {{/var}} in read-write white list for ability to write to database and
log directories, without black list capability. Hacker explicitly specify
{{/var/run/docker.socket}} to be included, put the socket in
{{/tmp/docker.socket}}. Hacker generates a docker image with /etc/group
modified to include his own name or setuid bit binary in container. Hack can
successfully gain control to host level docker without much effort.
{{/run}} contains a growing list of software that put their pid file or socket
in this location. System admin can't say no to not allow other software to
place their socket in {{/run}} location and share between containers due to
company requirement. However, he still doesn't want to let hacker gain root
access.
Solution 1:
System admin placed {{/var/*}} and {{/run/*}} (except /run/docker.socket),
carefully in read-write white list. None of the symlink is exposed. Hacker
can not get in.
Solution 2 (All symlinks are banned and explicit hardcoded locations):
(Current proposed patch)
System admin specifies:
white-list-read-write: {{/var}}, {{/run/*}} (except /run/docker.socket),
{{/mnt/hdfs/user/*}} (exception yarn)
black-list: {{/var/run}},{{/run/docker.socket}},{{/mnt/hdfs/user/yarn}}
Hacker attempt to mount a symlink location resulting in access denied from
container startup, or explicit hard coded location also result in ban.
Solution 3: (Ban symlink and replace black list location with empty directory):
(Jason proposed implementation)
System admin specifies:
white-list-read-write: {{/var}},{{/run}},{{/mnt/hdfs/user}}
black-list: {{/run/docker.socket}},{{/mnt/hdfs/user/yarn}}
Hacker attempt to mount a symlink location resulting in access denied from
container startup, or mount /run/docker.socket manually, but result in empty
file.
All solutions requires system administrator to enforce ability to upload secure
image to private registry to prevent torjan horse in docker image.
I can see the appeal that without having to do a high upkeep of
white-list-read-write directories by the new proposal. The third solution can
throw people off, if they do not know about black-list is hijacked to empty
location. However, the deeper nested directories, it would be harder to secure
by second solution. If community favors the third solution, I can revise patch
accordingly.
> Add support for a volume blacklist for docker containers
> --------------------------------------------------------
>
> Key: YARN-7197
> URL: https://issues.apache.org/jira/browse/YARN-7197
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: yarn
> Reporter: Shane Kumpf
> Assignee: Eric Yang
> Attachments: YARN-7197.001.patch, YARN-7197.002.patch
>
>
> Docker supports bind mounting host directories into containers. Work is
> underway to allow admins to configure a whilelist of volume mounts. While
> this is a much needed and useful feature, it opens the door for
> misconfiguration that may lead to users being able to compromise or crash the
> system.
> One example would be allowing users to mount /run from a host running
> systemd, and then running systemd in that container, rendering the host
> mostly unusable.
> This issue is to add support for a default blacklist. The default blacklist
> would be where we put files and directories that if mounted into a container,
> are likely to have negative consequences. Users are encouraged not to remove
> items from the default blacklist, but may do so if necessary.
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