Re: Strategy to Verify Python Program is POST'ing to a web server.

[Eden Kirin]

On 18.06.2011 13:34, mzagu...@gmail.com wrote:

Hello Folks,

I am wondering what your strategies are for ensuring that data
transmitted to a website via a python program is indeed from that
program, and not from someone submitting POST data using some other
means.  I find it likely that there is no solution, in which case what
is the best solution for sending data to a remote server from a python
program and ensuring that it is from that program?

For example, if I create a website that tracks some sort of
statistical information and don't ensure that my program is the one
that is uploading it, the statistics can be thrown off by people
entering false POST data onto the data upload page.  Any remedy?


Include some hash check in hidden field.

For example, from your python program you will include hidden fields 
random_number and hash:


import random, hashlib
my_secret_key = "MySecretKey"
random_number = "%f" % random.random()
hash = hashlib.sha1("%s %s" % (my_secret_key, random_number)).hexdigest()

On the server side check hash with random_number and secret key to 
ensure the data is POSTed from your application.


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SCGIServer and unusal termination

[Eden Kirin]

Hi there,

I'm playing with SCGIServer 
(http://vmlinux.org/cgi-bin/dwww/usr/share/doc/python-scgi/guide.html), 
everything works just fine, but one thing bothers me. All prints after 
try-except block are executed twice after the Ctrl+C is pressed!


test.py:
#-
from scgi.scgi_server import SCGIServer

n = 0
print "Starting server."

try:
SCGIServer().serve()
except (KeyboardInterrupt, SystemExit):
print "Exception!"

# print lines are executed twice (?!)
n += 1
print "Terminating server, attempt %d." % n
n += 1
print "Check n: %d." % n
#-

This is the output:

e...@sunce:~/data/project/ScgiServer/src> python test.py
Starting server.
^CException!
Exception!
Terminating server, attempt 1.
Check n: 2.
Terminating server, attempt 1.
Check n: 2.
e...@sunce:~/data/project/ScgiServer/src>


If I put something else in try-except block, code after is executed 
normally:


try:
while 1:
pass
except (KeyboardInterrupt, SystemExit):
print "Exception!"

e...@sunce:~/data/project/ScgiServer/src> python test.py
Starting server.
^CException!
Terminating server, attempt 1.
Check n: 2.
e...@sunce:~/data/project/ScgiServer/src>

Environment is 64bit Ubuntu with Python v2.6.4.

Is there some reasonable explanation for this behaviour? Thanks in advance.

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Re: SCGIServer and unusal termination

[Eden Kirin]

Anyone?

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Re: SCGIServer and unusal termination

[Eden Kirin]

Diez B. Roggisch wrote:


Is there some reasonable explanation for this behaviour? Thanks in
advance.


I can only guess that SCGIServer does something to stdout. Your code isn't
executed twice, so the doubling seems to come from writing it twice.


Yes I know that code isn't executed twice since the value of n remains 
the same, only print lines are doubled.



Try e.g. redirecting stdout and stderr to different files, and see if things
appear once in both.


Redirection of stdout:

e...@sunce:~/data/project/ScgiServer/test> python test.py 1> output.txt
^ce...@sunce:~/data/project/ScgiServer/test> cat output.txt
Starting server.
Exception!
Terminating server, attempt 1.
Check n: 2.
Starting server.
Exception!
Terminating server, attempt 1.
Check n: 2.

Redirecting stderr creates an empty file. I still haven't found the 
solution.


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Re: SCGIServer and unusal termination

[Eden Kirin]

Diez B. Roggisch wrote:


 - save a reference to sys.stdout *before* invoking the server
 - compare to it after interruption. If it has changed, you at least know
that somebody messed with it, and can beat him or whatever you see fit.


Thanks for the help. Finally, I dropped python-scgi module and I wrote 
my own SCGI server. There was not only the problem with stdout, but one 
much serious which made it unusable to me. Every SCGI request was forked 
as a new process, without the ability to access the shared globals 
within the project.


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Re: SCGIServer and unusal termination

[Eden Kirin]

Дамјан Георгиевски wrote:

SCGIServer().serve() forks, so it seems that there are 2 python 
processes continuing to run after SCGIServer().serve()


I noticed that which makes it unusable to me. Also, it took me almost 
whole day to realize this. I'm adopting a huge application to work with 
SCGI which shares a certain amount of data between working threads and 
SCGI handler. I couldn't realize the cause of erratic and unconsistent 
data behaviour. After diving into python-scgi code, I gave it up and 
wrote my own SCGI server.


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Re: simple and fast platform independent IPC

[Eden Kirin]

On 03.02.2010 09:32, News123 wrote:

Hi,

I wondered what IPC library might be best simplest for following task?


Consider using Thrift (http://incubator.apache.org/thrift/). It is 
multiplatform multilanguage RPC and IPC solution. I implemented it in 
couple of my projects and it works seamlessly.


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