[Pkg-shadow-devel] Bug#868568: Bug#868568: Bug#868568: Possible cause of deluser problem: subordinate user IDs

[Chris Hofstaedtler]

Control: retitle -1 adduser/useradd subid support lacking

Marc,

I have nothing new to add to this existing bug report, but its
something we need to figure out. Does adduser have any support for
subids nowadays?

On Tue, Mar 08, 2022 at 03:36:53PM -0500, Jason Franklin wrote:
> On Tue, 2022-03-08 at 18:39 +0000, Ben Harris wrote:
> > On Tue, 8 Mar 2022, Serge E. Hallyn wrote
> > > The bug is how you got into this state?  Either the adduser for
> > > the high uid should have checked for it being a delegated subuid,
> > > or the adduser which added the subuids to the lower subuid should
> > > have refused when the higher subuid existed as a uid.
> > 
> > As far as I can see, there is no checking for collisions in either 
> > direction: useradd depends on the ranges [UID_MIN,UID_MAX] and 
> > [SUB_UID_MIN,SUB_UID_MAX] not overlapping, and issues a warning if you 
> > assign a static UID outside the specified range.

[..]

> This is something that has recently gotten my attention in my adduser
> maintenance efforts. I am trying to help where I can to work around it
> and to collaborate with shadow on the issue to get at an optimal
> solution.
> 
> adduser has its own UID ranges set in /etc/adduser.conf. These variables
> are the ones that matter...
> 
> > FIRST_SYSTEM_UID=100
> > LAST_SYSTEM_UID=999
> > FIRST_SYSTEM_GID=100
> > LAST_SYSTEM_GID=999
> > FIRST_UID=1000
> > LAST_UID=59999
> > FIRST_GID=1000
> > LAST_GID=59999
> 
> As far as I can tell, adduser has no concept of a "subordinate UID"
> (neither do I for that matter). I was not familiar with this feature
> until recently. This is something I'll have to read about.
> 
> The latest upload of adduser (v3.120) uses a naive technique of passing
> through its own system user UID range settings to the useradd call. See
> below...
> 
>   &systemcall('/usr/sbin/useradd', '-r',
>       '-K', sprintf('SYS_UID_MIN=%d', $config{'first_system_uid'}),
>       '-K', sprintf('SYS_UID_MAX=%d', $config{'last_system_uid'}),
>       '-u', $new_uid,

[..]

> Other than having adduser pass through its own settings to avoid
> "useradd" warnings, I'm not sure what else can be done to reconcile this
> divergence.  It has existed for a while.

Indeed.

Chris