ctypes wrapping libpam.so on FreeBSD 6.1 - Python Bus Error

[Martin P. Hellwig]

Hey all,

I'd like to wrap libpam so that I can use that for authentication and
password management. I build ctypes (0.9.9.6) on my platform via ports.

Now according to OpenPAM documentation all sessions start with pam_start().
According to the man page it should contain this:
pam_start(const char *service, const char *user,
const struct pam_conv *pam_conv, pam_handle_t **pamh)

Where service in my case should be 'auth' and user 'martin' with
pam_conv being 'PAM_PROMPT_ECH O_ON' for testing purposes (at least I
assumed it works this way, but probably I'm doing something wrong,
though I don't know what the correct way should be like).

When I tried it, python dumps the core with a Bus Error, I also tried
other combinations but it all ends in a Bus Error, any suggestion how I
should proceed? I don't know much about PAM or C so any help is much
appreciated.

This (and other things) is what I've done:

[martin@xinag /usr/home/martin]$ su
Password:
xinag# python
Python 2.4.3 (#2, May 24 2006, 00:05:56)
[GCC 3.4.4 [FreeBSD] 20050518] on freebsd6
Type "help", "copyright" , "credits" or "license" for more information.

>>from ctypes import *
>>libpam = cdll.LoadLibrar y('/usr/lib/libpam.so')
>>libpam.pam_st art('auth','mar tin','PAM_PROMP T_ECHO_ON')

Bus error (core dumped)


Thanks in advance,

Martin

[Fredrik Lundh]

Re: ctypes wrapping libpam.so on FreeBSD 6.1 - Python Bus Error

Martin P. Hellwig wrote:

I'd like to wrap libpam so that I can use that for authentication and
password management. I build ctypes (0.9.9.6) on my platform via ports.
>
Now according to OpenPAM documentation all sessions start with pam_start().
According to the man page it should contain this:
pam_start(const char *service, const char *user,
const struct pam_conv *pam_conv, pam_handle_t **pamh)
>
Where service in my case should be 'auth' and user 'martin' with
pam_conv being 'PAM_PROMPT_ECH O_ON' for testing purposes (at least I
assumed it works this way, but probably I'm doing something wrong,
though I don't know what the correct way should be like).

>from ctypes import *
>libpam = cdll.LoadLibrar y('/usr/lib/libpam.so')
>libpam.pam_sta rt('auth','mart in','PAM_PROMPT _ECHO_ON')

passing in a string where the function expects a "struct pam_conv" (i.e. a custom data
structure) is probably not a very good idea... (look up "structures " in the ctypes manual
for more info on how to handle this)

</F>

[Ganesan Rajagopal]

Re: ctypes wrapping libpam.so on FreeBSD 6.1 - Python Bus Error

>>>>"Martin" == Martin P Hellwig <mhellwig@xs4al l.nlwrites:

Now according to OpenPAM documentation all sessions start with pam_start().
According to the man page it should contain this:
pam_start(const char *service, const char *user,
const struct pam_conv *pam_conv, pam_handle_t **pamh)

Note that pam_conv is a structure. Passing a string 'PAM_PROMPT_ECH O_ON' and
not passing a pointer for getting the pam_handle_t are both candidates to
cause a crash.

Ganesan

--
Ganesan Rajagopal

[Martin P. Hellwig]

Re: ctypes wrapping libpam.so on FreeBSD 6.1 - Python Bus Error

Frederik & Ganesan,

Thanks for the explanation, it did me realize that I should learn some C
first before I'm going to start wrapping something :-)

At least I got a reason now to do something with C, though it should
take me some time.

But again, thanks!

Martin