[PATCH setup] Add new option --chown-admin

[Christian Franke]

Jon Turney wrote:
> On 07/07/2022 15:45, Christian Franke wrote:
>> Jon Turney wrote:
>>> On 06/07/2022 17:34, Christian Franke wrote:
>>>> Jon Turney wrote:
>>>>> On 06/07/2022 08:14, Christian Franke wrote:
> [...]
>>>>>>
>>>>>> BTW: 'nt_sec.setDefaultSecurity (isAdmin)' is never called with 
>>>>>> 'isAdmin==true' as 'root_scope' is always 0.
>>>>>
>>>>> root_scope is set later, by the "Install For" option on the 
>>>>> "Select Root Install Directory" page.
>>>>>
>>>>> To me, this looks like a (very long standing) bug that we 
>>>>> shouldn't be calling setAdminGroup() here, but after root_scope 
>>>>> has been set.
>>>>
>>>> If this bug is very old, I'm not sure whether this should be fixed. 
>>>> Setting admin group to files which are owned "only" by current user 
>>>> is possibly not very effective.
>>>
>>> It's true that some people might be relying on that buggy behaviour.
>>
>> I have one very old Cygwin installation from Win7 times. Very old 
>> installed files still have group="Administrator", newer files have 
>> group="None". The timestamps suggest that the regression was 
>> introduced early in 2012. The first file with group="None" is from 
>> March 2 2012.
>
> Hmm... [1] seems like the obvious suspect for the change responsible 
> for that, but I don't immediately see how...
>
> [1] 
> https://cygwin.com/git/?p=cygwin-apps/setup.git;a=commitdiff;h=befc9dd806824f22ebb740be96ba8c0ae8f63bb4;hp=34d534a6d74e5516d6691fb1d9cb6309682afa0b
>

Hmm... correct as this change moves UserSettings ctor behind 
setDefaultSecurity ():

Old version 34d534a:
...
UserSettings Settings (local_dir);
...
nt_sec.setDefaultSecurity ();
...
Main.WindowCreate()


New version befc9dd:
...
nt_sec.setDefaultSecurity ();
...
UserSettings Settings (local_dir);
...
Main.WindowCreate()


The UserSettings ctor has a somewhat hidden side effect which sets 
root_scope correctly:

  UserSettings::UserSettings(...);
   open_settings("setup.rc", ...);
    io_stream::open("cygfile:///etc/setup/setup.rc", ...);
     io_stream_cygfile::io_stream_cygfile("/etc/setup/setup.rc", ...);
      get_root_dir_now();
       read_mounts("");
        read_mounts_nt("");
         root_scope = isuser ? IDC_ROOT_USER : IDC_ROOT_SYSTEM;

Conclusion: Regression introduced Feb 24, 2012 (befc9dd).