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Re: Reading subkeys from registry -- evil registry redirection?

by Discipulus (Monsignor)
on Nov 13, 2015 at 11:25 UTC ( #1147654=note: print w/replies, xml ) Need Help??


in reply to Reading subkeys from registry

ok gepebril69 I have not a solution as your code produces useful results for me and for others too(more about it below). But I have some suggestions.

Preamble: you said special access flags to make it happen on 64bit platforms and this ringed a bell in my mind: is this monk another victim of the evil microsoft redirection? you should already know, as you are using special access flags, but to fully understand read this post from me.

Filesystem redirection has two, equally evil, brothers: Registry redirection and COM object model. See what they say about Registry redirection.

Now that you know you are walking on mobile sands quicksand i can suggest to start with a little clean new code, instead of the code presented by you (even if it runs). In fact you are querying for unistallable programs and you know that your OS segregate 32bit from 64bit ones (with the funny WoW64 name..).

So i spoiled your code from unusefull things (delimiters, arrayvalues, the call of Dumper.. but also the dump af all keys) and i add just a little code to show if the Perl version is 64bit. Most important i removed your Access special keys (more on that below) part {Access=> 0x20019|0x0100} and used the standard flag imported from Win32API::Registry ie use Win32API::Registry qw(KEY_READ); .. Access=>KEY_READ()

So the code became:
use strict; use warnings; use Win32API::Registry qw(KEY_READ); use Config; print "\n\nPerl $Config{archname}\n"; use Win32::TieRegistry(Delimiter=>"/"); my $uninstall=$Registry->Open( "HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows/CurrentVersion/Unin +stall", { Access=>KEY_READ() #Access=> 0x20019|0x0100 } ); print "Number of subkeys found: ".scalar(keys %$uninstall)."\n";
With my little Perl version test program i got theese results:
| | | Perl MSWin32-x86-multi-thread | Number of subkeys found: 353 [OK] C:\ulisse\strawberry\perl\bin\perl.exe | | | Perl MSWin32-x86-multi-thread-64int | Number of subkeys found: 353 [OK] C:\ulisse\straw5.20-32b\perl\bin\perl.exe | | | Perl MSWin32-x64-multi-thread | Number of subkeys found: 77 <---- + look here [OK] C:\ulisse\straw64\perl\bin\perl.exe | | | Perl MSWin32-x86-multi-thread-64int | Number of subkeys found: 353 [OK] C:\ulisse\strP5.22-32\perl\bin\perl.exe
As the perl is 64bit the keys found are 77 on my workstation. 353 otherwise.

Now i understood why you used thees special keys (described here) because KEY_WOW64_64KEY (0x0100) is not exported by Win32API::Registry. and you used it diractly in junction with KEY_READ (0x20019).

using {Access=> 0x20019|0x0100} access (uncomment it in the above example and comment the Access=>KEY_READ()) give theese results:
| | | Perl MSWin32-x86-multi-thread | Number of subkeys found: 77 [OK] C:\ulisse\strawberry\perl\bin\perl.exe | | | Perl MSWin32-x86-multi-thread-64int | Number of subkeys found: 77 [OK] C:\ulisse\straw5.20-32b\perl\bin\perl.exe | | | Perl MSWin32-x64-multi-thread | Number of subkeys found: 77 [OK] C:\ulisse\straw64\perl\bin\perl.exe | | | Perl MSWin32-x86-multi-thread-64int | Number of subkeys found: 77 [OK] C:\ulisse\strP5.22-32\perl\bin\perl.exe
As you can see all Perls see only 77 unistallable programs. The description of the access mask tell us:KEY_WOW64_32KEY (0x0200) Indicates that an application on 64-bit Windows should operate on the 32-bit registry view... But is not true! is the opposite! UPDATE last senteces is wrong: see my last reply.

If you see zero key returned on your machine, with your original code, it means to me that you have no 64bit applications uninstallable on your system (the opposite of what i read from ms docs!! in fact in the 77 subkey i find programs that resides in the 64bit program folder "C:\Program Files").Or using other words: if you use your special access flag you are probably looking for the wrong thing. try just reading them and be aware of the possible redirection occuring when you play the three card game with that OS.

HtH and let us know
L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

Replies are listed 'Best First'.
Re^2: Reading subkeys from registry -- evil registry redirection?
by gepebril69 (Scribe) on Nov 13, 2015 at 18:52 UTC

    Hi Discipulus

    Thanks for all the effort so far

    When I run your code on both systems I get

    Perl MSWin32-x86-multi-thread-64int Number of subkeys found: 0
    and
    Perl MSWin32-x64-multi-thread Number of subkeys found: 0

    The used flags have little different background. Digging through Perlmonk history I found my old thread

    http://www.perlmonks.org/?node_id=1112763

    As you see, I got undef values on a different part of the registry
    Here I didn't get undef values, but empty results. Are you using Strawberry perl

      what do you mean with The used flags have little different background?

      Also note that Here I didn't get undef values, but empty results is not so true: if you put null values as hashref's keys and then you look for the number of keys, ie zero.

      If your last sentence is a question, yes i'm using strwaberryperl.

      As you understand the redirection, testing on 2008 OS you'll see that Perl 64bit always see it's own part of the registry (18 keys in this example) while 32Bit Perl see the 32bit part with KEY_READ() and the 64bit using the special flag 0x20019|0x0100. Thus confirm that official docs are wrong. See below:
      ###64bit Perl Perl MSWin32-x64-multi-thread access: 0x20019|0x0100 Number of subkeys found: 18 Perl MSWin32-x64-multi-thread access: KEY_READ() Number of subkeys found: 18 ###32bit Perl Perl MSWin32-x86-multi-thread access: 0x20019|0x0100 Number of subkeys found: 18 Perl MSWin32-x86-multi-thread access: KEY_READ() Number of subkeys found: 21

      HtH
      L*
      UPDATE: i was wrong (thanks Corion!) the docs are right:
      KEY_WOW64_32KEY (0x0200) Indicates that an application on 64-bit Windows should operate on the +32-bit registry view. KEY_WOW64_64KEY (0x0100) Indicates that an application on 64-bit Windows should operate on the +64-bit registry view.
      So the beahvior observed is rigtly documented.

      L*
      There are no rules, there are no thumbs..
      Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

        Thanks for the extended help sofar, in mean time I tried to work around this issue with 'reg query', but that gives different results running from CLI or batch/within Perl :(

        Q: what do you mean with The used flags have little different background?

        A: These were suggested with searching a different part of the registry with a different question

        Q:Also note that Here I didn't get undef values, but empty results is not so true: if you put null values as hashref's keys and then you look for the number of keys, ie zero.

        A: Well in this case I got a hasvalue returned, in the other case an undef value. Maybe that is similar, I thought that was different

        Will check this KEY_READ() solution, in the previous node. UPDATE! The KEY_READ() worked in the previous node. So that gives a good feeling.

        Anyway, no matter which access methode I use I get '0' results. Is there a way to switch on debuglevel to full so there is more data to work with

        Well the KEY_READ methode may be the right way to access the registry

        Unfortunately that doesn't explain why no keys are found in 32 and 64 Starwberry Perl versions on different Windows OS versions... ran in local user and admin mode (dos box)

        There must be some other access rule that prevents access to these subkeys as they are filled and accesible via othet tools..

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