[Python-Dev] is this a bug? no environment variables

[Glenn Linderman]

On 11/23/2010 3:55 AM, "Martin v. Löwis" wrote:
> Am 23.11.2010 11:55, schrieb Amaury Forgeot d'Arc:
>> Hi,
>>
>> 2010/11/23 Glenn Linderman<v+python at g.nevcal.com>:
>>>    File "C:\Python32\lib\random.py", line 108, in seed
>>>      a = int.from_bytes(_urandom(32), 'big')
>>> WindowsError: [Error -2146893818] Invalid Signature
>> In the subprocess documentation http://docs.python.org/library/subprocess.html
>> """On Windows, in order to run a side-by-side assembly the specified
>> env *must* include a valid SystemRoot."""
> Indeed, setting SystemRoot might solve this problem. According to
>
> http://jpassing.com/2009/12/28/the-hidden-danger-of-forgetting-to-specify-systemroot-in-a-custom-environment-block/
>
> CrypoAPI, in Windows 7, requires this variable be set. Failure to
> find the enhanced crypto provider would explain why the "random"
> module of Python fails to work.
>
> The specific cause is in the registry:
> HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Cryptography\Defaults\Provider\Microsoft
> Strong Cryptographic Provider has as it's ImagePath value
>
> %SystemRoot%\system32\rsaenh.dll
>
> So the registry (and COM) do rely on environment variables.
>
> Regards,
> Martin

I find it sad but hilarious that after working so hard to remove the 
need for environment variables from Windows that M$ has introduced new 
dependencies on them.

I wonder if this particular registry variable is simply an oversight/bug 
on M$' part, that they will eventually fix, or if it a turnaround toward 
the use of more environment variables in the future.  Hmm.  Time will 
tell, I suppose.  I'm unaware of any benefits in _changing_ SystemRoot 
to other values, so not pre-expanding it in that registry location seems 
only to add an unnecessary dependency on the environment.

Indeed, preserving that one environment variable allows my version of 
http.server to proceed with, as far as initial testing can determine, 
proper behavior.  Thanks for your help in figuring this out.  That was a 
lot faster than a "binary search" to choose which variable(s) to preserve.

My purpose in such testing was two-fold: firstly, web servers, for 
security purposes, generally limit the number of environment variables 
that are seen by CGI programs, and secondly, in debugging whether or not 
http.server was properly setting the necessary environment variables, 
the many other environment variables were cluttering up log dumps of all 
environment variables.  It will be nicer to limit the "passed through" 
environment variables to SystemRoot, as see how things go.

I have read some about side-by-side assemblies but had considered them a 
good reason to stick with the outdated M$VC 6.0 compiler, which doesn't 
seem to need to create them, and their myriad requirements, which seem 
far from necessary for simply compiling a program.  I was disappointed 
to realize that Python was heading down the path of using the newer 
tools that create side-by-side assemblies, but I suppose using an old 
and crufty compiler like M$VC 6.0 cannot support some of the newer 
features of Windows, which may seem to be necessary to some.... like 
64-bit support, which does seem necessary, even to me.

I was well aware that shortcuts and the registry _may_ refer to 
environment variables, and have a number of environment variables of my 
own which leverage that capability, to avoid hard-coded drive letters 
and paths in certain areas, and for the convenience of shorting the 
specification of some of the long-winded path names that Windows foists 
upon us (some of those have been significantly shortened in Windows 6.1, 
and maybe 6.0 which I used only for 2 months with disgust; 6.1 has 
helped alleviate the disgust, but I still recommend XP for people that 
don't need 64-bit capabilities).


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