Re: [Tutor] login window using Tk

[Steven D'Aprano]

On Wed, 2 Nov 2011 11:54:17 am Alan Gauld wrote:
> On 01/11/11 21:15, Joel Montes de Oca wrote:
> > Question, once the code is compiled to a binary, can someone
> > inject code to cause the hidden window to show, skipping the
> > login altogether?
>
> In general you don't compile Python to a binary, although tools
> exist that give a good approximation to that. But to inject code
> would need access to the source files 

A sufficiently clever byte-code hacker can insert byte-code straight 
into the .pyc file, given write permission to the files -- or an 
exploit that allows writing to a file.

Since people can modify machine code executables (that's how most 
viruses work, and cracked applications), modifying byte-code is 
unlikely to give them any trouble.

Here's a proof-of-concept virus that does exactly that:

http://www.symantec.com/connect/blogs/python-has-venom



-- 
Steven D'Aprano 
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Re: [Tutor] login window using Tk

[Chris Hare]

Just thought I would drop y'all a note and say thank you for your help on this. 
 I have the login code working.

I learned a bunch from you guys.

Thanks!

Chris Hare
ch...@labr.net
http://www.labr.net

On Nov 2, 2011, at 5:02 AM, Alan Gauld wrote:

> On 02/11/11 05:05, Chris Hare wrote:
> 
>> def verifyLogin(self):
>> farmid = list.get(ACTIVE)
>> userid = login_userid.get()
>> login_passwd = login_passwd.get()
>> 
>> gets called, but I get the error
>> 
>> Exception in Tkinter callback
>> farmid = list.get(ACTIVE)
>> AttributeError: type object 'list' has no attribute 'get'
>> 
>> When the frame controls were added, list is defined as
>> 
>> list = Listbox(frame)
> 
> names defined in functions are local to that function. They can't be seen 
> outside of the function. So...
> To be able to access the controls you need to add themas instance attributes 
> to your class. so you should use
> 
> self.list = Listbox(
> 
> and
> 
> farmid = self.list.get(
> 
> What you are seeing is Python looking for something called list in your 
> methods namespace and not finding it. It can't see anything global either so 
> it picks up the built-in list() type.
> 
> HTH
> 
> -- 
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> 
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Re: [Tutor] login window using Tk

[Alan Gauld]

On 02/11/11 05:05, Chris Hare wrote:


 def verifyLogin(self):
 farmid = list.get(ACTIVE)
 userid = login_userid.get()
 login_passwd = login_passwd.get()

gets called, but I get the error

Exception in Tkinter callback
 farmid = list.get(ACTIVE)
AttributeError: type object 'list' has no attribute 'get'

When the frame controls were added, list is defined as

list = Listbox(frame)


names defined in functions are local to that function. They can't be 
seen outside of the function. So...
To be able to access the controls you need to add themas instance 
attributes to your class. so you should use


self.list = Listbox(

and

farmid = self.list.get(

What you are seeing is Python looking for something called list in your 
methods namespace and not finding it. It can't see anything global 
either so it picks up the built-in list() type.


HTH

--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Chris Hare]

Thanks everyone for all of the help.  I almost have this working.

Everything is written in a class.  I think I have that right, but that remains 
to be seen. :-)

I can create the login window and get all of the controls on it.  My function 
gets called to validate the information in the fields when the user presses the 
button.  

the function called however, can't seem to be able to get the items from the 
fields.  I get the error like list.get(ACTIVE) doesn't have a function for get. 
 (list was defined as a listbox.)  the same is true for the other form fields. 
I opted to use the root window and implement a frame in it for the login.  Once 
the login data has been validated, i can destroy the frame and reuse the 
window.  This may or may not work ;-)  I am a python newbie, biting off a big 
complicated chunk 

The class is defined:
class Login:
def __init__(self, parent):
self.window = parent

When I show the class instance, everything is displayed.  My verification code,

def verifyLogin(self):
farmid = list.get(ACTIVE)
userid = login_userid.get()
login_passwd = login_passwd.get()

gets called, but I get the error

Exception in Tkinter callback
Traceback (most recent call last):
  File 
"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py",
 line 1410, in __call__
return self.func(*args)
  File "z.py", line 229, in verifyLogin
farmid = list.get(ACTIVE)
AttributeError: type object 'list' has no attribute 'get'

When the frame controls were added, list is defined as

list = Listbox(frame)

What have I got messed up?  I have poked around the net but I can't find 
anything meaningful to me.

Thanks again


Chris Hare
ch...@labr.net
http://www.labr.net

On Nov 1, 2011, at 7:50 PM, Alan Gauld wrote:

> On 01/11/11 21:28, Chris Hare wrote:
>> 
>> Good feedback Alan, thanks.
>> 
>> I wasn't using the root window to hold the login form, although I
>> suppose I could. I guess where I am stuck is the login to control
>> displaying the login window, and hiding it to display the actual
>> application window once the user has authenticated.
> 
> Thats what your command function does. So when the button is pressed your 
> event handler authenticates the user details, if valid it closes the Login 
> and shows the main window(which could be root...)
> In pseudocode:
> 
> 
> def doLogin(self):
>userid = idField.get()
>passwd = pwField.get()
>if self.validateUser(userid,passwd):
>root.show()
>self.window.hide()
>else:
>self.beep()   # or whatever warning message you want
>self.logError("User authentication failed for " + userid)
>self.idField.clear()
>self.pwField.clear()
> 
> Then in creating the button you pass that as the command handler:
> 
> btnLogin = Button(self.window, text="Login", command=doLogin)
> 
> Now, when the user hits the button the doLogin function will be called.
> If the login is ok we show the main window and hide the login dialog.
> If the entry is invalid we beep, clear the fields for a retry and log an 
> error. We could also add a count so after, say, three attempts we close the 
> app.
> 
> HTH
> -- 
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> 
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Re: [Tutor] login window using Tk

[Alan Gauld]

On 02/11/11 00:16, Justin Straube wrote:


Have you looked into using a Frame to hold you input fields, and then
using .destroy() to remove it upon successful login?


This is a valid approach for some scenarios but its not the norm for 
login dialogs. They usually popup as fairly small standalone windows.
But what you suggest could be done in a banner frame at the top or 
bottom of the main window, then either replaced or removed from the 
geometry.



Im just a hobbyist, so if there are reasons not to use this approach,
I'd be interested in why.


Only user experience I think. Its usually best to make a GUI work like 
the other GUIs that the user is accustomed to. OTOH many web pages use 
the login style that you are suggesting so maybe the fashions will 
change for desktop apps too.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Alan Gauld]

On 01/11/11 21:15, Joel Montes de Oca wrote:

Question, once the code is compiled to a binary, can someone inject code
to cause the hidden window to show, skipping the login altogether?


In general you don't compile Python to a binary, although tools exist 
that give a good approximation to that. But to inject code would need 
access to the source files and if you have been sensible with 
permissions etc that would require admin access to the machine...


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Alan Gauld]

On 01/11/11 21:28, Chris Hare wrote:


Good feedback Alan, thanks.

I wasn't using the root window to hold the login form, although I
suppose I could. I guess where I am stuck is the login to control
displaying the login window, and hiding it to display the actual
application window once the user has authenticated.


Thats what your command function does. So when the button is pressed 
your event handler authenticates the user details, if valid it closes 
the Login and shows the main window(which could be root...)

In pseudocode:


def doLogin(self):
userid = idField.get()
passwd = pwField.get()
if self.validateUser(userid,passwd):
root.show()
self.window.hide()
else:
self.beep()   # or whatever warning message you want
self.logError("User authentication failed for " + userid)
self.idField.clear()
self.pwField.clear()

Then in creating the button you pass that as the command handler:

btnLogin = Button(self.window, text="Login", command=doLogin)

Now, when the user hits the button the doLogin function will be called.
If the login is ok we show the main window and hide the login dialog.
If the entry is invalid we beep, clear the fields for a retry and log an 
error. We could also add a count so after, say, three attempts we close 
the app.


HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Justin Straube]

On 11/1/2011 3:28 PM, Chris Hare wrote:


Good feedback Alan, thanks.

I wasn't using the root window to hold the login form, although I
suppose I could. I guess where I am stuck is the login to control
displaying the login window, and hiding it to display the actual
application window once the user has authenticated.

Chris Hare
ch...@labr.net 
http://www.labr.net


Hi Chris,

Have you looked into using a Frame to hold you input fields, and then 
using .destroy() to remove it upon successful login?


This would allow you to not have to worry about hiding windows, as you 
can just reuse the same root window.


Im just a hobbyist, so if there are reasons not to use this approach, 
I'd be interested in why.


Justin
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Re: [Tutor] login window using Tk

[Wayne Werner]

On Nov 1, 2011 4:17 PM, "Joel Montes de Oca"  wrote:
>
> On 11/01/2011 02:18 PM, Alan Gauld wrote:
>>
>> On 01/11/11 18:09, Alexander Etter wrote:
>>
>>> Hi, hopefully a more experience hacker can provide clarity, but how
>>> secure does this login need to be? I dont much about python in DRAM but
>>> your login sounds like it could be easily hacked.
>>
>>
>> That depends entirely on how the user is authenticated.
>> (assuming basic things like blanked password fields in the UI etc)
>>
>> For all we know the authentication could be against a central
>> Single Sign On authentication server someplace.
>> The OP didn't say.
>>
>
> Question, once the code is compiled to a binary, can someone inject code
to cause the hidden window to show, skipping the login altogether?

Technically speaking, you could do that with /any/ program in any language.
Good security is hard, and some things are just not worth spending that
much time on. If good security were easy then photoshop wouldn't be pirated
so much.

-Wayne
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Re: [Tutor] login window using Tk

[Chris Hare]

Good feedback Alan, thanks.

I wasn't using the root window to hold the login form, although I suppose I 
could.  I guess where I am stuck is the login to control displaying the login 
window, and hiding it to display the actual application window once the user 
has authenticated.  

Chris Hare
ch...@labr.net
http://www.labr.net

On Nov 1, 2011, at 3:49 PM, Alan Gauld wrote:

> 

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Re: [Tutor] login window using Tk

[Joel Montes de Oca]

On 11/01/2011 02:18 PM, Alan Gauld wrote:

On 01/11/11 18:09, Alexander Etter wrote:


Hi, hopefully a more experience hacker can provide clarity, but how
secure does this login need to be? I dont much about python in DRAM but
your login sounds like it could be easily hacked.


That depends entirely on how the user is authenticated.
(assuming basic things like blanked password fields in the UI etc)

For all we know the authentication could be against a central
Single Sign On authentication server someplace.
The OP didn't say.



Question, once the code is compiled to a binary, can someone inject code 
to cause the hidden window to show, skipping the login altogether?


--
-Joel M.

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Re: [Tutor] login window using Tk

[Alan Gauld]

On 01/11/11 18:57, Chris Hare wrote:

Here is a code snippet I have pulled out of the project. It is as bare
bones as I can make it to get the point across.


I think you could have dropped a lot more to be honst - like all the 
menu code for a start...



1. I would really like the window to be centered in the user's screen,
but setting the geometry doesn't place it there. (that isn't included here)


OK, But thats a problem for another day.
And some of these things are OS/UI dependent so you need to tell us what 
OS you are on.




2. When I click the Login button, nothing happens. I know I am missing
something but it just isn't obvious what it is.


You don't provide a command in the command parameter. You provide a 
string. When you click the button Python will try to call the string, 
which won't work. You should get an error message in the console -= how 
are you running this? Is it from a command prompt? If not you may not be 
seeing all the error messages Python is sending you...



3. Finally, I would like to be able to hide the root window until the
authentication is performed, but root.hide() gets me a getattr error.
root.withdraw() works, but I can't get the root window back


Really? You want the Login window to disappear even before you have 
authenticated the user? Thats very unusual behaviour. Usually the login 
window only goes away once you have been authenticated.




import sys
from Tkinter import *
import tkMessageBox
import tkFont

class Login:
def __init__(self,parent):
self.window = parent

def show(instance):
window = Toplevel()
frame = Frame(window,bg=backColor)

> ...

label2 = Label(frame, text = "Username", fg="Blue", bg=backColor)
label3 = Label(frame, text = "Password", fg="Blue", bg=backColor)
login_userid = Entry(frame,bg=outFocusColor)
login_passwd = Entry(frame,bg=outFocusColor,show="*")
login_userid.bind("", login_passwd.focus_set())
btnLogin = Button(frame, text="Login", command="print button
pressed",highlightbackground=backColor)


you need to provide the name of a function to the command parameter - or 
use a lambda expression if its just a one liner



frame.grid()
label2.grid(row=2, column=0,columnspan=3, sticky=W)
login_userid.grid(row=2, column=6, columnspan=5,sticky=W)
label3.grid(row=3, column=0,columnspan=3, sticky=W)
login_passwd.grid(row=3, column=6, columnspan=5,sticky=W)
btnLogin.grid(row=4, column=4, sticky=W)




if __name__ == "__main__":
root = Tk()
root.withdraw()
l = Login(root)
l.show()

root.mainloop()


HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Wayne Werner]

On Tue, Nov 1, 2011 at 1:57 PM, Chris Hare  wrote:

> Here is a code snippet I have pulled out of the project.  It is as bare
> bones as I can make it to get the point across.
>
> the problems I am having:
>
> 1.  I would really like the window to be centered in the user's screen,
> but setting the geometry doesn't place it there.  (that isn't included here)
>

Take a look at the winfo_screenwidth/height methods.


> 2.  When I click the Login button, nothing happens.  I know I am missing
> something but it just isn't obvious what it is.
>

In your code you have "print button pressed" as the command - this is a
string, and certainly wont do anything useful - you want to put a function
here, e.g. command=self.login or something to that effect. You don't want
parenthesis, or it will try to login as soon as python creates your button.


> 3.  Finally, I would like to be able to hide the root window until the
> authentication is performed, but root.hide() gets me a getattr error.
>  root.withdraw() works, but I can't get the root window back
>

root.deiconify() is the method you're looking for here.

HTH,
Wayne
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Re: [Tutor] login window using Tk

[Chris Hare]

Okay - that makes sense.  The login window uses the show="*" for the password 
field and is authenticated against a database where the passwords are 
encrypted.  I have this working in a text only environment, just struggling to 
get it right for the GUI

Thanks

Chris Hare
ch...@labr.net
http://www.labr.net

On Nov 1, 2011, at 1:02 PM, Alan Gauld wrote:

> 

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Re: [Tutor] login window using Tk

[Chris Hare]

Here is a code snippet I have pulled out of the project.  It is as bare bones 
as I can make it to get the point across.

the problems I am having:

1.  I would really like the window to be centered in the user's screen, but 
setting the geometry doesn't place it there.  (that isn't included here)
2.  When I click the Login button, nothing happens.  I know I am missing 
something but it just isn't obvious what it is.
3.  Finally, I would like to be able to hide the root window until the 
authentication is performed, but root.hide() gets me a getattr error.  
root.withdraw() works, but I can't get the root window back 

Thanks for your help.  

import sys
from Tkinter import *
import tkMessageBox
import tkFont

class Login:
def __init__(self,parent):
self.window = parent

def show(instance): 
window = Toplevel()
frame = Frame(window,bg=backColor)
menubar = Menu(window)
filemenu = Menu(menubar, tearoff=0)
filemenu.add_command(label="Exit", command="sys.exit()")
menubar.add_cascade(label="File", menu=filemenu)
window.config(menu=menubar)
programName = Label(frame, text = "test")
list = Listbox(frame)
list.insert( END,"test")
label1 = Label(frame, text = "Organization", fg="Blue", 
bg=backColor)
label2 = Label(frame, text = "Username", fg="Blue", 
bg=backColor)
label3 = Label(frame, text = "Password", fg="Blue", 
bg=backColor)
login_userid = Entry(frame,bg=outFocusColor)
login_passwd = Entry(frame,bg=outFocusColor,show="*")
login_userid.bind("", login_passwd.focus_set())
btnLogin = Button(frame, text="Login", command="print button 
pressed",highlightbackground=backColor)

frame.title = "Login to application" 
list.focus_set()
frame.grid()
programName.grid(row=0, column=0,columnspan=5,sticky=W)
label1.grid(row=1, column=0,columnspan=3, sticky=W)
list.grid(row=1, column=6, columnspan=5, sticky=W)
label2.grid(row=2, column=0,columnspan=3, sticky=W)
login_userid.grid(row=2, column=6, columnspan=5,sticky=W)
label3.grid(row=3, column=0,columnspan=3, sticky=W)
login_passwd.grid(row=3, column=6, columnspan=5,sticky=W)
btnLogin.grid(row=4, column=4, sticky=W)

if __name__ == "__main__":
backColor = "Gray"
entryColor = "Cyan"
okColor = "Green"
warnColor = "Red"
inFocusColor = "Cyan"
outFocusColor = "White"

root = Tk()
root.withdraw()
l = Login(root)
l.show()

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Re: [Tutor] login window using Tk

[Alan Gauld]

On 01/11/11 18:09, Alexander Etter wrote:


Hi, hopefully a more experience hacker can provide clarity, but how
secure does this login need to be? I dont much about python in DRAM but
your login sounds like it could be easily hacked.


That depends entirely on how the user is authenticated.
(assuming basic things like blanked password fields in the UI etc)

For all we know the authentication could be against a central
Single Sign On authentication server someplace.
The OP didn't say.

--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Alexander Etter]

On Nov 1, 2011, at 12:47, Chris Hare  wrote:

> 
> I am working on a python Tk program which involves a login window and I am 
> looking for some advice.
> 
> Currently the code I have creates a window (Toplevel) where the login 
> controls are and I am running that using a main loop for the window.  The 
> root window is hidden.  The objective is that when the user ha successfully 
> authenticated, the login window is closed or the main loop os exited and then 
> the root window is shown and the main loop started for the actual application.
> 
> Questions:
> 1.  Is this the best way of doing this or is there a better way?
> 2.  How do I exit the main loop when the user has authenticated?
> 
> Thanks
> 
> Chris Hare
> ch...@labr.net
> 
> Tutor maillist  -  Tutor@python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor

Hi, hopefully a more experience hacker can provide clarity, but how secure does 
this login need to be? I dont much about python in DRAM but your login sounds 
like it could be easily hacked. 
Alexander___
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Re: [Tutor] login window using Tk

[Alan Gauld]

On 01/11/11 16:47, Chris Hare wrote:


I am working on a python Tk program which involves a login window and I
am looking for some advice.

Currently the code I have creates a window (Toplevel) where the login
controls are and I am running that using a main loop for the window.


Don't do this, it is frought with difficulties. Have a single
mainloop for the program. Everything else should be driven by
events.

So you initialise your program including creating both the main and 
login windows. You show the login window. When the user logs in you
validate the login and if not valid return control to the login window. 
If it is valid close the login window and show the main window.


You then proceed to process all events for the main window.

Trying to synchronize and control multiple mainloops in a GUI 
environment is incredibly hard to get right.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] login window using Tk

[Joel M.]

I am also intrested in this topic.

Chris were you thinking of using the window.hide() method?

-Joel M
On Nov 1, 2011 1:21 PM, "Chris Hare"  wrote:

>
> I am working on a python Tk program which involves a login window and I am
> looking for some advice.
>
> Currently the code I have creates a window (Toplevel) where the login
> controls are and I am running that using a main loop for the window.  The
> root window is hidden.  The objective is that when the user ha successfully
> authenticated, the login window is closed or the main loop os exited and
> then the root window is shown and the main loop started for the actual
> application.
>
> Questions:
> 1.  Is this the best way of doing this or is there a better way?
> 2.  How do I exit the main loop when the user has authenticated?
>
> Thanks
>
> Chris Hare
> ch...@labr.net
> http://www.labr.net
>
>
>
> Chris Hare
> ch...@labr.net
> http://www.labr.net
>
>
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>
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Re: [Tutor] login window using Tk

[Steve Willoughby]

On 01-Nov-11 09:47, Chris Hare wrote:

Questions:
1. Is this the best way of doing this or is there a better way?
2. How do I exit the main loop when the user has authenticated?


Why stop the main loop and restart it?  Typically you'd setup the app, 
and start the main loop running for the duration.  Everything else is 
handled by the application's logic.


For example, you'd display the login toplevel window, and when it's 
satisfied, it can trigger the functionality which creates (or displays 
the pre-created but hidden) application window and dismisses the login 
toplevel.



--
Steve Willoughby / st...@alchemy.com
"A ship in harbor is safe, but that is not what ships are built for."
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