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#!/usr/bin/python3
"""Msec plugin for enforcing pam-related settings"""
# main plugin class name
PLUGIN = "pam"
import os
import re
import gettext
import grp
# configuration
import config
# localization
try:
gettext.install('msec')
except IOError:
_ = str
class pam:
# configuration variables
SIMPLE_ROOT_AUTHEN = '/etc/pam.d/simple_root_authen'
SU = '/etc/pam.d/su'
SYSTEM_AUTH = '/etc/pam.d/system-auth'
OPASSWD = '/etc/security/opasswd'
# pam
SUCCEED_MATCH = '^auth\s+sufficient\s+pam_succeed_if.so\s+use_uid\s+user\s+ingroup\s+wheel\s*$'
SUCCEED_LINE = 'auth sufficient pam_succeed_if.so use_uid user ingroup wheel'
# password stuff
LENGTH_REGEXP = re.compile('^(password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*?)\sminlen=([0-9]+)\s(.*)')
NDIGITS_REGEXP = re.compile('^(password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*?)\sdcredit=([0-9]+)\s(.*)')
UCREDIT_REGEXP = re.compile('^(password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*?)\sucredit=([0-9]+)\s(.*)')
PASSWORD_REGEXP = '^\s*auth\s+sufficient\s+(?:/lib/security/)?pam_permit.so'
UNIX_REGEXP = re.compile('(^\s*password\s+sufficient\s+(?:/lib/security/)?pam_unix.so.*)\sremember=([0-9]+)(.*)')
PAM_TCB_REGEXP = re.compile('(^\s*password\s+sufficient\s+(?:/lib/security/)?pam_tcb.so.*)')
def __init__(self, log=None, configfiles=None, root=None):
# initializing plugin
self.log = log
self.configfiles = configfiles
self.root = root
# configuring entry in global settings
config.SETTINGS['ENABLE_PAM_WHEEL_FOR_SU'] = ("pam.enable_pam_wheel_for_su", ['yes', 'no'])
config.SETTINGS['ENABLE_PAM_ROOT_FROM_WHEEL'] = ("pam.enable_pam_root_from_wheel", ['yes', 'no'])
# password stuff
config.SETTINGS['ENABLE_PASSWORD'] = ("pam.enable_password", ['yes', 'no'])
config.SETTINGS['PASSWORD_HISTORY'] = ("pam.password_history", ['*'])
# format: min length, num upper, num digits
config.SETTINGS['PASSWORD_LENGTH'] = ("pam.password_length", ['*'])
# insert entry into system security settings
config.SETTINGS_SYSTEM.append('ENABLE_PAM_WHEEL_FOR_SU')
config.SETTINGS_SYSTEM.append('ENABLE_PAM_ROOT_FROM_WHEEL')
config.SETTINGS_SYSTEM.append('ENABLE_PASSWORD')
config.SETTINGS_SYSTEM.append('PASSWORD_HISTORY')
config.SETTINGS_SYSTEM.append('PASSWORD_LENGTH')
def enable_password(self, arg):
''' Use password to authenticate users. Take EXTREME care when disabling passwords, as it will leave the machine vulnerable.'''
system_auth = self.configfiles.get_config_file(self.SYSTEM_AUTH)
val = system_auth.get_match(self.PASSWORD_REGEXP)
if arg == "yes":
if val:
self.log.info(_('Using password to authenticate users'))
system_auth.remove_line_matching(self.PASSWORD_REGEXP)
else:
if not val:
self.log.info(_('Don\'t use password to authenticate users'))
system_auth.replace_line_matching(self.PASSWORD_REGEXP, 'auth sufficient pam_permit.so') or \
system_auth.insert_before('auth\s+sufficient', 'auth sufficient pam_permit.so')
def password_history(self, arg):
''' Set the password history length to prevent password reuse. This is not supported by pam_tcb. '''
system_auth = self.configfiles.get_config_file(self.SYSTEM_AUTH)
pam_tcb = system_auth.get_match(self.PAM_TCB_REGEXP)
if pam_tcb:
self.log.info(_('Password history not supported with pam_tcb.'))
return
# verify parameter validity
# max
try:
history = int(arg)
except:
self.log.error(_('Invalid maximum password history length: "%s"') % arg)
return
if system_auth.exists():
val = system_auth.get_match(self.UNIX_REGEXP, '@2')
if val and val != '':
val = int(val)
else:
val = 0
else:
val = 0
if history != val:
if history > 0:
self.log.info(_('Setting password history to %d.') % history)
system_auth.replace_line_matching(self.UNIX_REGEXP, '@1 remember=%d@3' % history) or \
system_auth.replace_line_matching('(^\s*password\s+sufficient\s+(?:/lib/security/)?pam_unix.so.*)', '@1 remember=%d' % history)
opasswd = self.configfiles.get_config_file(self.OPASSWD)
opasswd.exists() or opasswd.touch()
else:
self.log.info(_('Disabling password history'))
system_auth.replace_line_matching(self.UNIX_REGEXP, '@1@3')
def password_length(self, arg):
''' Set the password minimum length and minimum number of digit and minimum number of capitalized letters, using length,ndigits,nupper format.'''
try:
length, ndigits, nupper = arg.split(",")
length = int(length)
ndigits = int(ndigits)
nupper = int(nupper)
except:
self.log.error(_('Invalid password length "%s". Use "length,ndigits,nupper" as parameter') % arg)
return
passwd = self.configfiles.get_config_file(self.SYSTEM_AUTH)
val_length = val_ndigits = val_ucredit = 999999
if passwd.exists():
val_length = passwd.get_match(self.LENGTH_REGEXP, '@2')
if val_length:
val_length = int(val_length)
val_ndigits = passwd.get_match(self.NDIGITS_REGEXP, '@2')
if val_ndigits:
val_ndigits = int(val_ndigits)
val_ucredit = passwd.get_match(self.UCREDIT_REGEXP, '@2')
if val_ucredit:
val_ucredit = int(val_ucredit)
if passwd.exists() and (val_length != length or val_ndigits != ndigits or val_ucredit != nupper):
self.log.info(_('Setting minimum password length %d') % length)
(passwd.replace_line_matching(self.LENGTH_REGEXP,
'@1 minlen=%s @3' % length) or \
passwd.replace_line_matching('^password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*',
'@0 minlen=%s ' % length))
(passwd.replace_line_matching(self.NDIGITS_REGEXP,
'@1 dcredit=%s @3' % ndigits) or \
passwd.replace_line_matching('^password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*',
'@0 dcredit=%s ' % ndigits))
(passwd.replace_line_matching(self.UCREDIT_REGEXP,
'@1 ucredit=%s @3' % nupper) or \
passwd.replace_line_matching('^password\s+required\s+(?:/lib/security/)?pam_cracklib.so.*',
'@0 ucredit=%s ' % nupper))
def enable_pam_wheel_for_su(self, arg):
''' Allow only users in wheel group to su to root.'''
su = self.configfiles.get_config_file(self.SU)
val = su.get_match('^auth\s+required\s+(?:/lib/security/)?pam_wheel.so\s+use_uid\s*$')
if arg == "yes":
if not val:
self.log.info(_('Allowing su only from wheel group members'))
try:
ent = grp.getgrnam('wheel')
except KeyError:
error(_('no wheel group'))
return
members = ent[3]
if members == [] or members == ['root']:
self.log.error(_('Security configuration is defined to allow only members of the wheel group to su to root, but this group is empty. Please add the allowed users into the wheel group.'))
return
if su.exists():
(su.replace_line_matching('^[#\s]*auth\s+required\s+(?:/lib/security/)?pam_wheel.so\s+use_uid\s*$',
'auth required pam_wheel.so use_uid') or \
su.insert_before('^auth\s+include', 'auth required pam_wheel.so use_uid'))
else:
if val:
self.log.info(_('Allowing su for all'))
if su.exists():
su.replace_line_matching('^auth\s+required\s+(?:/lib/security/)?pam_wheel.so\s+use_uid\s*$',
'# auth required pam_wheel.so use_uid')
def enable_pam_root_from_wheel(self, arg):
''' Allow root access without password for the members of the wheel group.'''
su = self.configfiles.get_config_file(self.SU)
simple = self.configfiles.get_config_file(self.SIMPLE_ROOT_AUTHEN)
if not su.exists():
return
val = su.get_match(self.SUCCEED_MATCH)
val_simple = simple.get_match(self.SUCCEED_MATCH)
if arg == "yes":
if not val or not val_simple:
self.log.info(_('Allowing transparent root access for wheel group members'))
if not val:
su.insert_before('^auth\s+sufficient', self.SUCCEED_LINE)
if simple.exists() and not val_simple:
simple.insert_before('^auth\s+sufficient', self.SUCCEED_LINE)
else:
if val or val_simple:
self.log.info(_('Disabling transparent root access for wheel group members'))
if val:
su.remove_line_matching(self.SUCCEED_MATCH)
if simple.exists() and val_simple:
simple.remove_line_matching(self.SUCCEED_MATCH)
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