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# (c) 2007 Chris AtLee <chris@atlee.ca>
# Licensed under the MIT license:
# http://www.opensource.org/licenses/mit-license.php
"""
PAM module for python
Provides an authenticate function that will allow the caller to authenticate
a user against the Pluggable Authentication Modules (PAM) on the system.
Implemented using ctypes, so no compilation is necessary.
---
modified to work [better] with python3.2, 2011-12-6, david ford, <david@blue-labs.org>
i haven't paid any attention to making sure things work in python2. there may be
problems in my_conv()
---
Just some encoding fixes for python3, 2012-01-27 Matthias Schiffer <mschiffer@universe-factory.net>
"""
import sys
import locale
if sys.version_info >= (3,):
py3k = True
else:
py3k = False
from ctypes import CDLL, POINTER, Structure, CFUNCTYPE, cast, pointer, sizeof
from ctypes import c_void_p, c_uint, c_char_p, c_char, c_int
from ctypes import memmove
from ctypes.util import find_library
class PamHandle(Structure):
"""wrapper class for pam_handle_t"""
_fields_ = [
("handle", c_void_p)
]
def __init__(self):
Structure.__init__(self)
self.handle = 0
class PamMessage(Structure):
"""wrapper class for pam_message structure"""
_fields_ = [
("msg_style", c_int),
("msg", c_char_p),
]
def __repr__(self):
return "<PamMessage %i '%s'>" % (self.msg_style, self.msg)
class PamResponse(Structure):
"""wrapper class for pam_response structure"""
_fields_ = [
("resp", c_char_p),
("resp_retcode", c_int),
]
def __repr__(self):
return "<PamResponse %i '%s'>" % (self.resp_retcode, self.resp)
CONV_FUNC = CFUNCTYPE(
c_int,
c_int,
POINTER(POINTER(PamMessage)),
POINTER(POINTER(PamResponse)),
c_void_p)
class PamConv(Structure):
"""wrapper class for pam_conv structure"""
_fields_ = [
("conv", CONV_FUNC),
("appdata_ptr", c_void_p)
]
# Various constants
PAM_PROMPT_ECHO_OFF = 1
PAM_PROMPT_ECHO_ON = 2
PAM_ERROR_MSG = 3
PAM_TEXT_INFO = 4
LIBC = CDLL(find_library("c"))
LIBPAM = CDLL(find_library("pam"))
CALLOC = LIBC.calloc
CALLOC.restype = c_void_p
CALLOC.argtypes = [c_uint, c_uint]
PAM_START = LIBPAM.pam_start
PAM_START.restype = c_int
PAM_START.argtypes = [c_char_p, c_char_p, POINTER(PamConv), POINTER(PamHandle)]
PAM_STRERROR = LIBPAM.pam_strerror
PAM_STRERROR.restype = c_char_p
PAM_STRERROR.argtypes = [POINTER(PamHandle), c_int]
PAM_AUTHENTICATE = LIBPAM.pam_authenticate
PAM_AUTHENTICATE.restype = c_int
PAM_AUTHENTICATE.argtypes = [PamHandle, c_int]
class pam():
code = 0
reason = None
def __init__(self):
pass
def authenticate(self, username, password, service='login'):
"""username and password authenticate for the given service.
Returns True for success, or False. self.code is the integer
value representing the numerice failure reason, or 0 on success.
self.reason is the textual reason.
Python3 expects bytes() for ctypes inputs. This function will make
necessary conversions using the latin-1 coding.
username: the username to authenticate
password: the password in plain text
service: the PAM service to authenticate against.
Defaults to 'login' """
@CONV_FUNC
def my_conv(n_messages, messages, p_response, app_data):
"""Simple conversation function that responds to any
prompt where the echo is off with the supplied password"""
# Create an array of n_messages response objects
addr = CALLOC(n_messages, sizeof(PamResponse))
p_response[0] = cast(addr, POINTER(PamResponse))
for i in range(n_messages):
if messages[i].contents.msg_style == PAM_PROMPT_ECHO_OFF:
cs = c_char_p(password)
dst = CALLOC(sizeof(c_char_p), len(password)+1)
memmove(dst , cs, len(password))
p_response.contents[i].resp = dst
p_response.contents[i].resp_retcode = 0
return 0
# python3 ctypes prefers bytes, pretend everyone will be happy using latin-1
if py3k:
if isinstance(username, str):
username = bytes(username, locale.getpreferredencoding())
if isinstance(password, str):
password = bytes(password, locale.getpreferredencoding())
if isinstance(service, str):
service = bytes(service, locale.getpreferredencoding())
handle = PamHandle()
conv = PamConv(my_conv, 0)
retval = PAM_START(service, username, pointer(conv), pointer(handle))
if retval != 0:
# This is not an authentication error, something has gone wrong starting up PAM
self.code = retval
self.reason = str(PAM_STRERROR(pointer(handle), retval), locale.getpreferredencoding())
return False
retval = PAM_AUTHENTICATE(handle, 0)
if retval == 0:
# success
logic = True
else:
logic = False
# store information to inform the caller why we failed
self.code = retval
self.reason = str(PAM_STRERROR(pointer(handle), retval), locale.getpreferredencoding())
return logic
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