[HACKERS] Re: BUG #13755: pgwin32_is_service not checking ifSECURITY_SERVICE_SID is disabled

On 11/08/2016 07:56 AM, Michael Paquier wrote:
> On Tue, Nov 8, 2016 at 2:25 PM, Tsunakawa, Takayuki
> <tsunakawa.takay@jp.fujitsu.com> wrote:
>> From: pgsql-hackers-owner@postgresql.org
>>> [mailto:pgsql-hackers-owner@postgresql.org] On Behalf Of Michael Paquier
>>> Things are this way since b15f9b08 that introduced pgwin32_is_service().
>>> Still, by considering what you say, you definitely have a point that if
>>> postgres is started by another service running as Local System logs are
>>> going where they should not. Let's remove the check for LocalSystem but
>>> still check for SE_GROUP_ENABLED.

I did some testing on patch v5, on my Windows 8 VM. I launched cmd as 
Administrator, and registered the service with:

pg_ctl register -D data

I.e. without specifying a user. When I start the service with "net 
start", it refuses to start, and there are no messages in the event log. 
It refuses to start because "data" is not a valid directory, so that's 
correct. But the error message about that is lost.

Added some debugging messages to win32_is_service(), and it confirms 
that with this patch (v5), win32_is_service() incorrectly returns false, 
while unmodified git master returns true, and writes the error message 
to the event log.

So, I think we still need the check for Local System.

>>> So, without any refactoring work, isn't the attached patch just but fine?
>>> That seems to work properly for me.
>>
>> Just taking a look at the patch, I'm sure it will work.
>>
>> Committer (Heikki?),
>> v5 is refactored for HEAD, and v6 is for previous releases without refactoring.  I'd like v5 to be applied to at
leastHEAD, as it removes a lot of unnecessary code.
 
>
> +    if (!CheckTokenMembership(NULL, AdministratorsSid, &IsAdministrators) ||
> +        !CheckTokenMembership(NULL, PowerUsersSid, &IsPowerUsers))
>      {
> -        if ((EqualSid(AdministratorsSid, Groups->Groups[x].Sid) &&
> -             (Groups->Groups[x].Attributes & SE_GROUP_ENABLED)) ||
> -            (EqualSid(PowerUsersSid, Groups->Groups[x].Sid) &&
> -             (Groups->Groups[x].Attributes & SE_GROUP_ENABLED)))
> -        {
> -            success = TRUE;
> -            break;
> -        }
> +        log_error("could not check access token membership: error code %lu\n",
> +                GetLastError());
> +        exit(1);
>      }
> I just looked more deeply at your refactoring patch, and I didn't know
> about CheckTokenMembership()... The whole logic of your patch depends
> on it. That's quite a cleanup that you have here. It looks that the
> former implementation just had no knowledge of this routine or it
> would just have been used.

Yeah, CheckTokenMembership() seems really handy. Let's switch to that, 
but without removing the checks for Local System.

- Heikki