RFC: Default File Permissions

[Josh Cooper]

Recently, the issue of copying file modes from remote sources was discussed on the puppet-users mailing list[1], although it equally applies to owner and group.

One issue is what permissions to apply to newly created files when none are specified? Historically, Puppet has always copied the permissions from the file source to the newly created one. However, this causes problems on Windows[2] agents due to the way that Puppet emulates POSIX permissions. We break NTFS access control inheritance to ensure the effective permissions are not greater than what Puppet has granted. It also causes problems on *nix agents, when the files' source is remote and uid/gids are not synchronized.

A second, but related issue, is that Puppet applies the same copy-permissions logic to files that already exist. This goes against what jcbollinger said, "unmanaged resources and resource properties should not be modified by Puppet"[3], and what Nigel said, "A core principle of Puppet is that you can choose to only manage the attributes of a resource that you care about, and can leave the rest unmanaged."[4] However, this "bug" has been around so long, at least 0.24.8, that we can't change behaviors in a minor release.[5]

Patrick and I talked about this and would like to propose adding a file parameter, something like `use_source_permissions`. If true and permissions are unspecified, Puppet would continue copying source permissions as it does today, for both newly created and existing files. This would be the default.

If false and permission are unspecified, Puppet would never copy them from the source. Instead the permission defaults for newly created files would be based on the user that Puppet is running as. And the permissions for existing files would be unmodified.

Doing so would provide a mechanism for resolving both #5240 and #18931.

Comments and feedback welcome.

Josh

[1] https://groups.google.com/forum/#!msg/puppet-users/CI7pEUHknm4/x-hCGJn6Ms8J
[2] https://projects.puppetlabs.com/issues/18931
[3] https://groups.google.com/d/msg/puppet-users/CI7pEUHknm4/VtCl9YmeIS0J
[4] http://projects.puppetlabs.com/issues/5240#note-16
[5] https://projects.puppetlabs.com/issues/5240

[Nikola Petrov]

I have seen this issue for sure many times. I always forget this and
when I see it while running with --noop, I change the owner and the
group on the file resource. I am +1 on fixing this to have a more
deterministic behaviour

Best, Nikola

[llowder]

On Friday, February 8, 2013 6:56:55 AM UTC-6, nikolavp wrote:

I have seen this issue for sure many times. I always forget this and
when I see it while running with --noop, I change the owner and the
group on the file resource. I am +1 on fixing this to have a more
deterministic behaviour

It seems like a good idea, though to maintain backwards compatibilty, would it be better to have the proposed fixed default to false (ie, maintain current behavior)?

[jcbollinger]

On Thursday, February 7, 2013 7:48:58 PM UTC-6, Josh Cooper wrote:

Recently, the issue of copying file modes from remote sources was discussed on the puppet-users mailing list[1], although it equally applies to owner and group.

One issue is what permissions to apply to newly created files when none are specified? Historically, Puppet has always copied the permissions from the file source to the newly created one. However, this causes problems on Windows[2] agents due to the way that Puppet emulates POSIX permissions. We break NTFS access control inheritance to ensure the effective permissions are not greater than what Puppet has granted. It also causes problems on *nix agents, when the files' source is remote and uid/gids are not synchronized.

A second, but related issue, is that Puppet applies the same copy-permissions logic to files that already exist. This goes against what jcbollinger said, "unmanaged resources and resource properties should not be modified by Puppet"[3], and what Nigel said, "A core principle of Puppet is that you can choose to only manage the attributes of a resource that you care about, and can leave the rest unmanaged."[4] However, this "bug" has been around so long, at least 0.24.8, that we can't change behaviors in a minor release.[5]

Patrick and I talked about this and would like to propose adding a file parameter, something like `use_source_permissions`. If true and permissions are unspecified, Puppet would continue copying source permissions as it does today, for both newly created and existing files. This would be the default.

If false and permission are unspecified, Puppet would never copy them from the source. Instead the permission defaults for newly created files would be based on the user that Puppet is running as. And the permissions for existing files would be unmodified.

Doing so would provide a mechanism for resolving both #5240 and #18931.

Comments and feedback welcome.

I think this is a fine and useful idea, but I'm not sure it goes far enough.  In the first place, it says nothing about uid / gid, even though it is acknowledged that the same problem applies to them.  Is that just an oversight?

In the second place, there is another usage mode to consider: what if you want to copy source permissions / uid / gid in the event that Puppet creates the file (since you cannot create the file without choosing those properties somehow), but you do not want to enforce those properties on the file if it already exists?  I'm not convinced that this case needs to be supported, but it should at least be considered.


John

[Josh Cooper]

Hi,

On Fri, Feb 8, 2013 at 5:42 AM, llowder <llow...@gmail.com> wrote:
>
>
> On Friday, February 8, 2013 6:56:55 AM UTC-6, nikolavp wrote:
>>
>> I have seen this issue for sure many times. I always forget this and
>> when I see it while running with --noop, I change the owner and the
>> group on the file resource. I am +1 on fixing this to have a more
>> deterministic behaviour
>>
>
> It seems like a good idea, though to maintain backwards compatibilty, would
> it be better to have the proposed fixed default to false (ie, maintain
> current behavior)?

"If true and permissions are unspecified, Puppet would continue
copying source permissions as it does today, for both newly created
and existing files. This would be the default."

Josh

--
Josh Cooper
Developer, Puppet Labs

[Josh Cooper]

Hi John,

Good point, I didn't explicitly mention this, but yes, I am proposing
that this behavior affect all file permissions - uid, gid, and mode.

> In the second place, there is another usage mode to consider: what if you
> want to copy source permissions / uid / gid in the event that Puppet creates
> the file (since you cannot create the file without choosing those properties
> somehow), but you do not want to enforce those properties on the file if it
> already exists? I'm not convinced that this case needs to be supported, but
> it should at least be considered.

So this is really the heart of issue #5240. Perhaps
use_source_permissions needs to be more than a boolean? Something
like:

use_source_permissions
:always - what puppet does today (default)
:creates - only apply source permissions when creating a file
:never - what I was proposing

Also, I didn't explicitly mention this, but I am proposing that this
affect all types of file resources (file, dir, link), not just files.

[Jakov Sosic]

Could this attribute be shorter? Like 'use_source_perm' or just
'source_perms'?

And I agree with this solution, and in the next major version simply
change default to never and that's it :)


--
Jakov Sosic
www.srce.unizg.hr

[Keith Burdis]

Since it would apply to more than just permissions perhaps 'source_attributes' would be better?

  - Keith

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[Klavs Klavsen]

This would be a GREAT benefit, and I for one, would definetely make it my File default :)

source_permissions is a fine name for it.

[Kylo Ginsberg]

Hello all,

Just a quick update on this issue.  We're planning to fix this for 3.4 and there's a pull request at:

https://github.com/puppetlabs/puppet/pull/2087

Also, after some discussion with Nick F, we renamed the 3 values of source_permissions to: 

use, use_when_creating, ignore

Thanks for any comments.  It will be great to have this issue addressed!

Kylo

--

Kylo Ginsberg

ky...@puppetlabs.com

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