config: add "umask" field to POSIX "user" section by cyphar · Pull Request #941 · opencontainers/runtime-spec

cyphar · 2017-12-06T12:33:15Z

Users may want to specify the umask(2) of the init process in a
container. This value is identical in semantics to POSIX. This is in
order to allow usage of an OCI container for a service which normally
only inherits the umask given to it.

See-also: opencontainers/runc#1650
Requested-by: @leberknecht
Signed-off-by: Aleksa Sarai asarai@suse.de

Users may want to specify the umask(2) of the init process in a container. This value is identical in semantics to POSIX. This is in order to allow usage of an OCI container for a service which normally only inherits the umask given to it. Signed-off-by: Aleksa Sarai <asarai@suse.de>

crosbymichael · 2017-12-06T15:45:30Z

When do you plan to set this during init? Right before exec or when the rootfs is being setup like the existing umask settings?

wking · 2017-12-06T18:40:19Z


 * **`uid`** (int, REQUIRED) specifies the user ID in the [container namespace](glossary.md#container-namespace).
 * **`gid`** (int, REQUIRED) specifies the group ID in the [container namespace](glossary.md#container-namespace).
+* **`umask`** (int, OPTIONAL) specifies the [umask][umask_2] of the user. If unspecified, the umask should not be changed from the calling process' umask.


nit: the possessive of “process” is “process's”, see us here and the Linux man pages here.
nit: the “If unspecified…” sentence should go on its own line.

wking · 2017-12-06T18:40:57Z

 "GID": {
 "$ref": "#/definitions/uint32"
 },
+ "Umask": {


The indent here is a bit strange. You can automatically format these files by running make fmt in the schema directory.

wking · 2017-12-06T18:42:47Z

When do you plan to set this during init? Right before exec or when the rootfs is being setup…

The way the spec reads now (#700), runtimes will be able to chose either of those as they see fit.

wking · 2017-12-06T18:54:04Z

 [selinux]:http://selinuxproject.org/page/Main_Page
 [no-new-privs]: https://www.kernel.org/doc/Documentation/prctl/no_new_privs.txt
 [proc_2]: https://www.kernel.org/doc/Documentation/filesystems/proc.txt
+[umask.2]: http://pubs.opengroup.org/onlinepubs/009695399/functions/umask.html


nit: POSIX functions should go be in section 3 (or 3p), so umask.2 should be umask.3. umask.2 would be the Linux kernel docs for umask.
nit: you're linking to the 2004 edition of POSIX. I'd rather stay consistent with our other links and use the 2016 edition (#858).

wking · 2017-12-06T19:02:28Z

 	// GID is the group id.
 	GID uint32 `json:"gid" platform:"linux,solaris"`
+	// Umask is the umask for the init process.
+	Umask uint32 `json:"umask,omitempty" platform:"linux,solaris"`


Zero is a valid umask (it means “leave the permissions entirely up to the process itself”), so I think we need a pointer here.

cyphar · 2017-12-06T23:46:53Z

@crosbymichael In runc I would want to do this right before exec because it refers to the container process, no? But maybe there's an argument for it to be done earlier -- I'm not sure?

vbatts · 2018-04-04T22:08:22Z

@cyphar @crosbymichael I interpret this as being set right before exec. Perhaps that could be clearer.

wking · 2018-04-04T22:38:33Z

On Wed, Apr 04, 2018 at 03:08:23PM -0700, Vincent Batts wrote: @cyphar @crosbymichael I interpret this as being set right before exec. Perhaps that could be clearer.

If you want that interpretation to be portable across compliant runtimes, I think you'd want to land wording to that effect around [1], with something like: Runtimes MUST NOT apply process.user.umask as part of creation; that property is only applied during [start](#start). [1]: https://github.com/opencontainers/runtime-spec/blame/v1.0.1/runtime.md#L103

stain · 2018-10-17T09:45:47Z

As this is still pending approval since April - what needs to be done to progress this PR?

leberknecht · 2018-11-19T15:49:26Z

Anything we can do here?

vbatts · 2018-11-19T16:36:08Z

 "user": {
 "uid": 1,
 "gid": 1,
+ "umask": 63,


i get that they're just ints, but i wish octals were a viewable in json, and 077 wouldn't be 77

vbatts · 2018-11-19T16:37:34Z

When do you plan to set this during init? Right before exec or when the rootfs is being setup like the existing umask settings?

I would see this as right before exec. What would you're hopes be?

cyphar · 2018-11-19T19:58:19Z

I think right before exec would be most reasonable, since it's a setting about the container and not about configuring devices and others such things. Generally most config.json options aren't meant to impact internal runtime setup (except in cases where it can't be avoided like cgroups).

rhatdan · 2019-08-06T12:52:41Z

This has come up again in a request for Podman. Is there anything we could do to move this forward?

giuseppe · 2019-08-06T13:20:18Z

@crosbymichael In runc I would want to do this right before exec because it refers to the container process, no? But maybe there's an argument for it to be done earlier -- I'm not sure?

doing it just before exec seems like the correct thing to me. Currently runc does it in finalizeRootfs (https://github.com/opencontainers/runc/blob/master/libcontainer/rootfs_linux.go#L151). The umask inside the container is always set to 022

crosbymichael · 2019-08-06T14:29:37Z

LGTM

leberknecht · 2019-10-07T09:57:10Z

@caniszczyk @dqminh @hqhq @mrunalp @philips @tianon @vbatts @vishh
sorry for spamming, but can someone please do the required second review here? :)

caniszczyk · 2019-10-07T12:20:09Z

RFC @opencontainers/runtime-spec-maintainers

tianon · 2019-10-07T14:21:31Z

I think @wking's comments look to be relevant and should be addressed (especially the inconsistent formatting). It also seems like a good idea IMO to clarify when this is expected to be applied, per @crosbymichael's comments.

vbatts · 2019-12-17T19:22:55Z

LGTM
And as this is OPTIONAL it is a non-breaking, forward compatible feature.

zhangyoufu · 2025-12-22T06:47:21Z

Why umask belongs to user? umask is a property of process, and has no relation to user.

cyphar force-pushed the config-umask-option branch from 34da7a6 to 6b04c63Compare December 6, 2017 12:36

cyphar mentioned this pull request Dec 6, 2017
Option to set umask of exec-user opencontainers/runc#1650
Closed

wking reviewed Dec 6, 2017
View reviewed changes

vbatts reviewed Nov 19, 2018
View reviewed changes

giuseppe mentioned this pull request Aug 6, 2019
Set umask in container cri-o/cri-o#2701
Closed

vbatts merged commit cd13d2d into opencontainers:masterDec 17, 2019

vbatts mentioned this pull request Jan 9, 2020
Release v1.0.2 #1026
Closed

cyphar deleted the config-umask-option branch February 24, 2020 00:09

kolyshkin mentioned this pull request Jul 21, 2022
Umask behavior doesn't match spec opencontainers/runc#3533
Open

zhangyoufu mentioned this pull request Dec 22, 2025
pkg/oci: add WithUmask for SpecOpts containerd/containerd#12719
Merged

zhangyoufu mentioned this pull request Jul 23, 2026
Add umask support moby/moby#53083
Closed

zhangyoufu mentioned this pull request Aug 25, 2026
Add umask support moby/moby#53463
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