path: root/src/conf_mode/system-login.py

#!/usr/bin/env python3
#
# Copyright (C) 2020-2023 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import os

from passlib.hosts import linux_context
from psutil import users
from pwd import getpwall
from pwd import getpwnam
from sys import exit
from time import sleep

from vyos.config import Config
from vyos.configverify import verify_vrf
from vyos.defaults import directories
from vyos.template import render
from vyos.template import is_ipv4
from vyos.utils.boot import boot_configuration_complete
from vyos.utils.dict import dict_search
from vyos.utils.process import cmd
from vyos.utils.process import call
from vyos.utils.process import rc_cmd
from vyos.utils.process import run
from vyos.utils.process import DEVNULL
from vyos import ConfigError
from vyos import airbag
airbag.enable()

autologout_file = "/etc/profile.d/autologout.sh"
limits_file = "/etc/security/limits.d/10-vyos.conf"
radius_config_file = "/etc/pam_radius_auth.conf"
tacacs_pam_config_file = "/etc/tacplus_servers"
tacacs_nss_config_file = "/etc/tacplus_nss.conf"
nss_config_file = "/etc/nsswitch.conf"

# Minimum UID used when adding system users
MIN_USER_UID: int = 1000
# Maximim UID used when adding system users
MAX_USER_UID: int = 59999
# LOGIN_TIMEOUT from /etc/loign.defs minus 10 sec
MAX_RADIUS_TIMEOUT: int = 50
# MAX_RADIUS_TIMEOUT divided by 2 sec (minimum recomended timeout)
MAX_RADIUS_COUNT: int = 8
# Maximum number of supported TACACS servers
MAX_TACACS_COUNT: int = 8

# List of local user accounts that must be preserved
SYSTEM_USER_SKIP_LIST: list = ['radius_user', 'radius_priv_user', 'tacacs0', 'tacacs1',
                              'tacacs2', 'tacacs3', 'tacacs4', 'tacacs5', 'tacacs6',
                              'tacacs7', 'tacacs8', 'tacacs9', 'tacacs10',' tacacs11',
                              'tacacs12', 'tacacs13', 'tacacs14', 'tacacs15']

def get_local_users():
    """Return list of dynamically allocated users (see Debian Policy Manual)"""
    local_users = []
    for s_user in getpwall():
        if getpwnam(s_user.pw_name).pw_uid < MIN_USER_UID:
            continue
        if getpwnam(s_user.pw_name).pw_uid > MAX_USER_UID:
            continue
        if s_user.pw_name in SYSTEM_USER_SKIP_LIST:
            continue
        local_users.append(s_user.pw_name)

    return local_users

def get_shadow_password(username):
    with open('/etc/shadow') as f:
        for user in f.readlines():
            items = user.split(":")
            if username == items[0]:
                return items[1]
    return None

def get_config(config=None):
    if config:
        conf = config
    else:
        conf = Config()
    base = ['system', 'login']
    login = conf.get_config_dict(base, key_mangling=('-', '_'),
                                 no_tag_node_value_mangle=True,
                                 get_first_key=True,
                                 with_recursive_defaults=True)

    # users no longer existing in the running configuration need to be deleted
    local_users = get_local_users()
    cli_users = []
    if 'user' in login:
        cli_users = list(login['user'])

    # prune TACACS global defaults if not set by user
    if login.from_defaults(['tacacs']):
        del login['tacacs']

    # create a list of all users, cli and users
    all_users = list(set(local_users + cli_users))
    # We will remove any normal users that dos not exist in the current
    # configuration. This can happen if user is added but configuration was not
    # saved and system is rebooted.
    rm_users = [tmp for tmp in all_users if tmp not in cli_users]
    if rm_users: login.update({'rm_users' : rm_users})

    return login

def verify(login):
    if 'rm_users' in login:
        # This check is required as the script is also executed from vyos-router
        # init script and there is no SUDO_USER environment variable available
        # during system boot.
        if 'SUDO_USER' in os.environ:
            cur_user = os.environ['SUDO_USER']
            if cur_user in login['rm_users']:
                raise ConfigError(f'Attempting to delete current user: {cur_user}')

    if 'user' in login:
        system_users = getpwall()
        for user, user_config in login['user'].items():
            # Linux system users range up until UID 1000, we can not create a
            # VyOS CLI user which already exists as system user
            for s_user in system_users:
                if s_user.pw_name == user and s_user.pw_uid < MIN_USER_UID:
                    raise ConfigError(f'User "{user}" can not be created, conflict with local system account!')

            for pubkey, pubkey_options in (dict_search('authentication.public_keys', user_config) or {}).items():
                if 'type' not in pubkey_options:
                    raise ConfigError(f'Missing type for public-key "{pubkey}"!')
                if 'key' not in pubkey_options:
                    raise ConfigError(f'Missing key for public-key "{pubkey}"!')

    if {'radius', 'tacacs'} <= set(login):
        raise ConfigError('Using both RADIUS and TACACS at the same time is not supported!')

    # At lease one RADIUS server must not be disabled
    if 'radius' in login:
        if 'server' not in login['radius']:
            raise ConfigError('No RADIUS server defined!')
        sum_timeout: int = 0
        radius_servers_count: int = 0
        fail = True
        for server, server_config in dict_search('radius.server', login).items():
            if 'key' not in server_config:
                raise ConfigError(f'RADIUS server "{server}" requires key!')
            if 'disable' not in server_config:
                sum_timeout += int(server_config['timeout'])
                radius_servers_count += 1
                fail = False

        if fail:
            raise ConfigError('All RADIUS servers are disabled')

        if radius_servers_count > MAX_RADIUS_COUNT:
            raise ConfigError(f'Number of RADIUS servers exceeded maximum of {MAX_RADIUS_COUNT}!')

        if sum_timeout > MAX_RADIUS_TIMEOUT:
            raise ConfigError('Sum of RADIUS servers timeouts '
                              'has to be less or eq 50 sec')

        verify_vrf(login['radius'])

        if 'source_address' in login['radius']:
            ipv4_count = 0
            ipv6_count = 0
            for address in login['radius']['source_address']:
                if is_ipv4(address): ipv4_count += 1
                else:                ipv6_count += 1

            if ipv4_count > 1:
                raise ConfigError('Only one IPv4 source-address can be set!')
            if ipv6_count > 1:
                raise ConfigError('Only one IPv6 source-address can be set!')

    if 'tacacs' in login:
        tacacs_servers_count: int = 0
        fail = True
        for server, server_config in dict_search('tacacs.server', login).items():
            if 'key' not in server_config:
                raise ConfigError(f'TACACS server "{server}" requires key!')
            if 'disable' not in server_config:
                tacacs_servers_count += 1
                fail = False

        if fail:
            raise ConfigError('All RADIUS servers are disabled')

        if tacacs_servers_count > MAX_TACACS_COUNT:
            raise ConfigError(f'Number of TACACS servers exceeded maximum of {MAX_TACACS_COUNT}!')

        verify_vrf(login['tacacs'])

    if 'max_login_session' in login and 'timeout' not in login:
        raise ConfigError('"login timeout" must be configured!')

    return None


def generate(login):
    # calculate users encrypted password
    if 'user' in login:
        for user, user_config in login['user'].items():
            tmp = dict_search('authentication.plaintext_password', user_config)
            if tmp:
                encrypted_password = linux_context.hash(tmp)
                login['user'][user]['authentication']['encrypted_password'] = encrypted_password
                del login['user'][user]['authentication']['plaintext_password']

                # remove old plaintext password and set new encrypted password
                env = os.environ.copy()
                env['vyos_libexec_dir'] = directories['base']

                # Set default commands for re-adding user with encrypted password
                del_user_plain = f"system login user {user} authentication plaintext-password"
                add_user_encrypt = f"system login user {user} authentication encrypted-password '{encrypted_password}'"

                lvl = env['VYATTA_EDIT_LEVEL']
                # We're in config edit level, for example "edit system login"
                # Change default commands for re-adding user with encrypted password
                if lvl != '/':
                    # Replace '/system/login' to 'system login'
                    lvl = lvl.strip('/').split('/')
                    # Convert command str to list
                    del_user_plain = del_user_plain.split()
                    # New command exclude level, for example "edit system login"
                    del_user_plain = del_user_plain[len(lvl):]
                    # Convert string to list
                    del_user_plain = " ".join(del_user_plain)

                    add_user_encrypt = add_user_encrypt.split()
                    add_user_encrypt = add_user_encrypt[len(lvl):]
                    add_user_encrypt = " ".join(add_user_encrypt)

                ret, out = rc_cmd(f"/opt/vyatta/sbin/my_delete {del_user_plain}", env=env)
                if ret: raise ConfigError(out)
                ret, out = rc_cmd(f"/opt/vyatta/sbin/my_set {add_user_encrypt}", env=env)
                if ret: raise ConfigError(out)
            else:
                try:
                    if get_shadow_password(user) == dict_search('authentication.encrypted_password', user_config):
                        # If the current encrypted bassword matches the encrypted password
                        # from the config - do not update it. This will remove the encrypted
                        # value from the system logs.
                        #
                        # The encrypted password will be set only once during the first boot
                        # after an image upgrade.
                        del login['user'][user]['authentication']['encrypted_password']
                except:
                    pass

    ### RADIUS based user authentication
    if 'radius' in login:
        render(radius_config_file, 'login/pam_radius_auth.conf.j2', login,
                   permission=0o600, user='root', group='root')
    else:
        if os.path.isfile(radius_config_file):
            os.unlink(radius_config_file)

    ### TACACS+ based user authentication
    if 'tacacs' in login:
        render(tacacs_pam_config_file, 'login/tacplus_servers.j2', login,
                   permission=0o644, user='root', group='root')
        render(tacacs_nss_config_file, 'login/tacplus_nss.conf.j2', login,
                   permission=0o644, user='root', group='root')
    else:
        if os.path.isfile(tacacs_pam_config_file):
            os.unlink(tacacs_pam_config_file)
        if os.path.isfile(tacacs_nss_config_file):
            os.unlink(tacacs_nss_config_file)

    # NSS must always be present on the system
    render(nss_config_file, 'login/nsswitch.conf.j2', login,
               permission=0o644, user='root', group='root')

    # /etc/security/limits.d/10-vyos.conf
    if 'max_login_session' in login:
        render(limits_file, 'login/limits.j2', login,
                   permission=0o644, user='root', group='root')
    else:
        if os.path.isfile(limits_file):
            os.unlink(limits_file)

    if 'timeout' in login:
        render(autologout_file, 'login/autologout.j2', login,
                   permission=0o755, user='root', group='root')
    else:
        if os.path.isfile(autologout_file):
            os.unlink(autologout_file)

    return None


def apply(login):
    # Script is invoked from vyos-router.service during startup.
    # While configuration mounting and so on is not yet complete,
    # skip any code that messes with the local user database
    if not boot_configuration_complete():
        return None

    if 'user' in login:
        for user, user_config in login['user'].items():
            # make new user using vyatta shell and make home directory (-m),
            # default group of 100 (users)
            command = 'useradd --create-home --no-user-group '
            # check if user already exists:
            if user in get_local_users():
                # update existing account
                command = 'usermod'

            # all accounts use /bin/vbash
            command += ' --shell /bin/vbash'
            # we need to use '' quotes when passing formatted data to the shell
            # else it will not work as some data parts are lost in translation
            tmp = dict_search('authentication.encrypted_password', user_config)
            if tmp: command += f" --password '{tmp}'"

            tmp = dict_search('full_name', user_config)
            if tmp: command += f" --comment '{tmp}'"

            tmp = dict_search('home_directory', user_config)
            if tmp: command += f" --home '{tmp}'"
            else: command += f" --home '/home/{user}'"

            command += f' --groups frr,frrvty,vyattacfg,sudo,adm,dip,disk {user}'
            try:
                cmd(command)

                # we should not rely on the value stored in
                # user_config['home_directory'], as a crazy user will choose
                # username root or any other system user which will fail.
                #
                # XXX: Should we deny using root at all?
                home_dir = getpwnam(user).pw_dir
                render(f'{home_dir}/.ssh/authorized_keys', 'login/authorized_keys.j2',
                       user_config, permission=0o600,
                       formater=lambda _: _.replace("&quot;", '"'),
                       user=user, group='users')

            except Exception as e:
                raise ConfigError(f'Adding user "{user}" raised exception: "{e}"')

            # Generate 2FA/MFA One-Time-Pad configuration
            if dict_search('authentication.otp.key', user_config):
                render(f'{home_dir}/.google_authenticator', 'login/pam_otp_ga.conf.j2',
                       user_config, permission=0o400, user=user, group='users')
            else:
                # delete configuration as it's not enabled for the user
                if os.path.exists(f'{home_dir}/.google_authenticator'):
                    os.remove(f'{home_dir}/.google_authenticator')

    if 'rm_users' in login:
        for user in login['rm_users']:
            try:
                # Disable user to prevent re-login
                call(f'usermod -s /sbin/nologin {user}')

                # Logout user if he is still logged in
                if user in list(set([tmp[0] for tmp in users()])):
                    print(f'{user} is logged in, forcing logout!')
                    # re-run command until user is logged out
                    while run(f'pkill -HUP -u {user}'):
                        sleep(0.250)

                # Remove user account but leave home directory in place. Re-run
                # command until user is removed - userdel might return 8 as
                # SSH sessions are not all yet properly cleaned away, thus we
                # simply re-run the command until the account wen't away
                while run(f'userdel {user}', stderr=DEVNULL):
                    sleep(0.250)

            except Exception as e:
                raise ConfigError(f'Deleting user "{user}" raised exception: {e}')

    # Enable RADIUS in PAM configuration
    pam_cmd = '--remove'
    if 'radius' in login:
        pam_cmd = '--enable'
    cmd(f'pam-auth-update --package {pam_cmd} radius')

    # Enable/Disable TACACS in PAM configuration
    pam_cmd = '--remove'
    if 'tacacs' in login:
        pam_cmd = '--enable'
    cmd(f'pam-auth-update --package {pam_cmd} tacplus')

    return None


if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)