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service_snmp.py
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service_snmp.py
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#!/usr/bin/env python3
#
# Copyright (C) 2018-2025 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 sys import exit
from vyos.base import Warning
from vyos.config import Config
from vyos.configdict import dict_merge
from vyos.configverify import verify_vrf
from vyos.defaults import systemd_services
from vyos.snmpv3_hashgen import plaintext_to_md5
from vyos.snmpv3_hashgen import plaintext_to_sha1
from vyos.snmpv3_hashgen import random
from vyos.template import render
from vyos.utils.configfs import delete_cli_node
from vyos.utils.configfs import add_cli_node
from vyos.utils.dict import dict_search
from vyos.utils.network import is_addr_assigned
from vyos.utils.process import call
from vyos.utils.permission import chmod_755
from vyos.version import get_version_data
from vyos import ConfigError
from vyos import airbag
airbag.enable()
config_file_client = r'/etc/snmp/snmp.conf'
config_file_daemon = r'/etc/snmp/snmpd.conf'
config_file_access = r'/usr/share/snmp/snmpd.conf'
config_file_user = r'/var/lib/snmp/snmpd.conf'
default_script_dir = r'/config/user-data/'
systemd_override = r'/run/systemd/system/snmpd.service.d/override.conf'
systemd_service = systemd_services['snmpd']
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['service', 'snmp']
snmp = conf.get_config_dict(base, key_mangling=('-', '_'),
get_first_key=True, no_tag_node_value_mangle=True)
if not conf.exists(base):
snmp.update({'deleted' : ''})
if conf.exists(['service', 'lldp', 'snmp']):
snmp.update({'lldp_snmp' : ''})
if 'deleted' in snmp:
return snmp
version_data = get_version_data()
snmp['version'] = version_data['version']
# create an internal snmpv3 user of the form 'vyosxxxxxxxxxxxxxxxx'
snmp['vyos_user'] = 'vyos' + random(8)
snmp['vyos_user_pass'] = random(16)
# We have gathered the dict representation of the CLI, but there are default
# options which we need to update into the dictionary retrived.
snmp = conf.merge_defaults(snmp, recursive=True)
if 'listen_address' in snmp:
# Always listen on localhost if an explicit address has been configured
# This is a safety measure to not end up with invalid listen addresses
# that are not configured on this system. See https://vyos.dev/T850
if '127.0.0.1' not in snmp['listen_address']:
tmp = {'127.0.0.1': {'port': '161'}}
snmp['listen_address'] = dict_merge(tmp, snmp['listen_address'])
if '::1' not in snmp['listen_address']:
tmp = {'::1': {'port': '161'}}
snmp['listen_address'] = dict_merge(tmp, snmp['listen_address'])
if 'script_extensions' in snmp and 'extension_name' in snmp['script_extensions']:
for key, val in snmp['script_extensions']['extension_name'].items():
if 'script' not in val:
continue
script_path = val['script']
# if script has not absolute path, use pre configured path
if not os.path.isabs(script_path):
script_path = os.path.join(default_script_dir, script_path)
snmp['script_extensions']['extension_name'][key]['script'] = script_path
return snmp
def verify(snmp):
if 'deleted' in snmp:
return None
if {'deleted', 'lldp_snmp'} <= set(snmp):
raise ConfigError('Can not delete SNMP service, as LLDP still uses SNMP!')
### check if the configured script actually exist
if 'script_extensions' in snmp and 'extension_name' in snmp['script_extensions']:
for extension, extension_opt in snmp['script_extensions']['extension_name'].items():
if 'script' not in extension_opt:
raise ConfigError(f'Script extension "{extension}" requires an actual script to be configured!')
tmp = extension_opt['script']
if not os.path.isfile(tmp):
Warning(f'script "{tmp}" does not exist!')
else:
chmod_755(extension_opt['script'])
if 'listen_address' in snmp:
for address in snmp['listen_address']:
# We only wan't to configure addresses that exist on the system.
# Hint the user if they don't exist
if 'vrf' in snmp:
vrf_name = snmp['vrf']
if not is_addr_assigned(address, vrf_name) and address not in ['::1','127.0.0.1']:
raise ConfigError(f'SNMP listen address "{address}" not configured in vrf "{vrf_name}"!')
elif not is_addr_assigned(address):
raise ConfigError(f'SNMP listen address "{address}" not configured in default vrf!')
if 'trap_target' in snmp:
for trap, trap_config in snmp['trap_target'].items():
if 'community' not in trap_config:
raise ConfigError(f'Trap target "{trap}" requires a community to be set!')
if 'oid_enable' in snmp:
Warning(f'Custom OIDs are enabled and may lead to system instability and high resource consumption')
verify_vrf(snmp)
# bail out early if SNMP v3 is not configured
if 'v3' not in snmp:
return None
if 'user' in snmp['v3']:
if 'engineid' not in snmp['v3']:
raise ConfigError(f'EngineID must be configured for SNMPv3!')
for user, user_config in snmp['v3']['user'].items():
if 'group' not in user_config:
raise ConfigError(f'Group membership required for user "{user}"!')
if 'plaintext_password' not in user_config['auth'] and 'encrypted_password' not in user_config['auth']:
raise ConfigError(f'Must specify authentication encrypted-password or plaintext-password for user "{user}"!')
if 'plaintext_password' not in user_config['privacy'] and 'encrypted_password' not in user_config['privacy']:
raise ConfigError(f'Must specify privacy encrypted-password or plaintext-password for user "{user}"!')
if 'group' in snmp['v3']:
for group, group_config in snmp['v3']['group'].items():
if 'seclevel' not in group_config:
raise ConfigError(f'Must configure "seclevel" for group "{group}"!')
if 'view' not in group_config:
raise ConfigError(f'Must configure "view" for group "{group}"!')
# Check if 'view' exists
view = group_config['view']
if 'view' not in snmp['v3'] or view not in snmp['v3']['view']:
raise ConfigError(f'You must create view "{view}" first!')
if 'view' in snmp['v3']:
for view, view_config in snmp['v3']['view'].items():
if 'oid' not in view_config:
raise ConfigError(f'Must configure an "oid" for view "{view}"!')
if 'trap_target' in snmp['v3']:
for trap, trap_config in snmp['v3']['trap_target'].items():
if 'plaintext_password' not in trap_config['auth'] and 'encrypted_password' not in trap_config['auth']:
raise ConfigError(f'Must specify one of authentication encrypted-password or plaintext-password for trap "{trap}"!')
if {'plaintext_password', 'encrypted_password'} <= set(trap_config['auth']):
raise ConfigError(f'Can not specify both authentication encrypted-password and plaintext-password for trap "{trap}"!')
if 'plaintext_password' not in trap_config['privacy'] and 'encrypted_password' not in trap_config['privacy']:
raise ConfigError(f'Must specify one of privacy encrypted-password or plaintext-password for trap "{trap}"!')
if {'plaintext_password', 'encrypted_password'} <= set(trap_config['privacy']):
raise ConfigError(f'Can not specify both privacy encrypted-password and plaintext-password for trap "{trap}"!')
if 'type' not in trap_config:
raise ConfigError('SNMP v3 trap "type" must be specified!')
return None
def generate(snmp):
# As we are manipulating the snmpd user database we have to stop it first!
# This is even save if service is going to be removed
call(f'systemctl stop {systemd_service}')
# Clean config files
config_files = [config_file_client, config_file_daemon,
config_file_access, config_file_user, systemd_override]
for file in config_files:
if os.path.isfile(file):
os.unlink(file)
if 'deleted' in snmp:
return None
if 'v3' in snmp:
# SNMPv3 uses a hashed password. If CLI defines a plaintext password,
# we will hash it in the background and replace the CLI node!
if 'user' in snmp['v3']:
for user, user_config in snmp['v3']['user'].items():
if dict_search('auth.type', user_config) == 'sha':
hash = plaintext_to_sha1
else:
hash = plaintext_to_md5
if dict_search('auth.plaintext_password', user_config) is not None:
tmp = hash(dict_search('auth.plaintext_password', user_config),
dict_search('v3.engineid', snmp))
snmp['v3']['user'][user]['auth']['encrypted_password'] = tmp
del snmp['v3']['user'][user]['auth']['plaintext_password']
cli_base = ['service', 'snmp', 'v3', 'user', user, 'auth']
delete_cli_node(cli_base + ['plaintext-password'])
add_cli_node(cli_base + ['encrypted-password'], value=tmp)
if dict_search('privacy.plaintext_password', user_config) is not None:
tmp = hash(dict_search('privacy.plaintext_password', user_config),
dict_search('v3.engineid', snmp))
snmp['v3']['user'][user]['privacy']['encrypted_password'] = tmp
del snmp['v3']['user'][user]['privacy']['plaintext_password']
cli_base = ['service', 'snmp', 'v3', 'user', user, 'privacy']
delete_cli_node(cli_base + ['plaintext-password'])
add_cli_node(cli_base + ['encrypted-password'], value=tmp)
# Write client config file
render(config_file_client, 'snmp/etc.snmp.conf.j2', snmp)
# Write server config file
render(config_file_daemon, 'snmp/etc.snmpd.conf.j2', snmp)
# Write access rights config file
render(config_file_access, 'snmp/usr.snmpd.conf.j2', snmp)
# Write access rights config file
render(config_file_user, 'snmp/var.snmpd.conf.j2', snmp)
# Write daemon configuration file
render(systemd_override, 'snmp/override.conf.j2', snmp)
return None
def apply(snmp):
# Always reload systemd manager configuration
call('systemctl daemon-reload')
if 'deleted' in snmp:
return None
# start SNMP daemon
call(f'systemctl reload-or-restart {systemd_service}')
return None
if __name__ == '__main__':
try:
c = get_config()
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)

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