Python, CGI and PGP

[Jim Dennis]

In article <3ca0b0f9 at peer1.news.newnet.co.uk>, Phil Edwards wrote:

>Jim Dennis wrote:

 ...

> Thanks, Jim, this is definitely one for the "little black book". When I see 
> things like this, I'm reminded just why I love UNIX so much...

>>  If you are reasonably persistent and a little clever you should be able

> Oh, that leaves me out, then :-)

> Managed to figure it all out with the help of the wrapper stuff above. It 
> turns out that both 'os.system' and 'commands.getoutput' (which I had 
> tried) trash so much of the execution environment that there's hardly 
> anything left for the binary to wprk with.

 I'd suspect that the web server is probably cleaning most of 
 the environment out.  I wouldn't immediately suspect Python of
 doing it (though I haven't looked through its code nor run
 an strace on it).

 A quick test from an interactive Python session (calling 
 os.system("bash") and also os.system("sh")) shows that they 
 have almost the same environment that I have from before 
 Python was loaded.  (The only discrepancies were SHLVL, which 
 is to be expected, and in the LINES and COLUMNS values, which 
 appeared in my sub-shells but not in the parent of my Python 
 process.  LINES and COLUMNS are set by bash for curses support
 --- but their omission should be innocuous for our purposes here.

 The web server, on the other hand, is well advised to execute
 CGIs in a "clean room" environment.  It probably uses one of the
 flavors of exec*() that passes a pointer to a new environment 
 to the system and thence to the child process.  You might be 
 able to modify your Apache (or other httpd / web server) configuration
 to retain more of your environment.

> I'm left with the following code in my CGI app:

>  cmd = 'export PGPPATH=/var/www/.pgp; /usr/local/bin/pgp -z windsurf -sta 
> -f - '
>  print 'content-type: text/html\n\n'
        
>  pw,pr = os.popen2(cmd)
>  pw.write(tdata)
>  pw.close()
>  junk = pr.read()
        
>  print string.replace(junk, '\n', '<br>\n')

> Thanks for your help! It's a shame there isn't a scheme for sending 
> beer/pizza vouchers over the 'net...

 You could send that to the Samba team in Canberra, Australia.
 I learned part of that trick from Tridge (Andre Tridgell, the
 creator of Samba).  They used to have an account with the local
 pizza shop.  I suppose you could follow the link on their web 
 site (http://www.samba.org/ ) to buy mugs or T-shirts.

 I've actually been considering creating a Paypal account for
 receiving payments from my remote consulting customers.  However,
 I'd never charge for answers to USENET.  

 I just consider the effort I put into my answers here to be a small 
 token of gratitude for the many answers I've received *from* netnews.  
 Despite all the flamers, trolls, and spam I've found that netnews is 
 the fastest way for me to learn a new technical subject.  
 
 Although I'll read any manuals I can find (I've got about a dozen 
 Python books at this point) and I'll even take the odd class if I can 
 find the time (they usually don't fit into my schedule, and they 
 usually go WAY TOO SLOW) and I go to user group meetings (too often 
 in a formal presentation style rather than a "workshop" gathering).

 Despite all these alternative approaches I find that the USENET 
 netnews medium affords the most practical way for me to learn.
 I do well when posed with lots of diverse questions around a subject
 and given the instant gratification of many answers (some wrong!).
 The game I play with myself, is that I try to guess the answer to 
 each puzzle and I try to critique each proposed answer.  As I 
 find that I can guess the "right" answers more often then not, I 
 move from lurker mode to active participant.  That forces me to 
 actually write and test my examples, which forces me to look up
 reference material on specific functions, which helps me gain
 practical proficiency.

 (I've been studying Python for about six months now).

 Anyway, glad I could help.