snmp.py
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snmp.py
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	#!/usr/bin/env python3
	#
	# Copyright (C) 2018-2020 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.config import Config
	from vyos.configverify import verify_vrf
	from vyos.snmpv3_hashgen import plaintext_to_md5, plaintext_to_sha1, random
	from vyos.template import render
	from vyos.util import call, chmod_755
	from vyos.validate import is_ipv4, is_addr_assigned
	from vyos.version import get_version_data
	from vyos import ConfigError, 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'/etc/systemd/system/snmpd.service.d/override.conf'

	# SNMP OIDs used to mark auth/priv type
	OIDs = {
	'md5' : '.1.3.6.1.6.3.10.1.1.2',
	'sha' : '.1.3.6.1.6.3.10.1.1.3',
	'aes' : '.1.3.6.1.6.3.10.1.2.4',
	'des' : '.1.3.6.1.6.3.10.1.2.2',
	'none': '.1.3.6.1.6.3.10.1.2.1'
	}

	default_config_data = {
	'listen_on': [],
	'listen_address': [],
	'ipv6_enabled': 'True',
	'communities': [],
	'smux_peers': [],
	'location' : '',
	'description' : '',
	'contact' : '',
	'trap_source': '',
	'trap_targets': [],
	'vyos_user': '',
	'vyos_user_pass': '',
	'version': '',
	'v3_enabled': 'False',
	'v3_engineid': '',
	'v3_groups': [],
	'v3_traps': [],
	'v3_users': [],
	'v3_views': [],
	'script_ext': []
	}

	def rmfile(file):
	if os.path.isfile(file):
	os.unlink(file)

	def get_config():
	snmp = default_config_data
	conf = Config()
	if not conf.exists('service snmp'):
	return None
	else:
	if conf.exists('system ipv6 disable'):
	snmp['ipv6_enabled'] = False

	conf.set_level('service 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)

	if conf.exists('community'):
	for name in conf.list_nodes('community'):
	community = {
	'name': name,
	'authorization': 'ro',
	'network_v4': [],
	'network_v6': [],
	'has_source' : False
	}

	if conf.exists('community {0} authorization'.format(name)):
	community['authorization'] = conf.return_value('community {0} authorization'.format(name))

	# Subnet of SNMP client(s) allowed to contact system
	if conf.exists('community {0} network'.format(name)):
	for addr in conf.return_values('community {0} network'.format(name)):
	if is_ipv4(addr):
	community['network_v4'].append(addr)
	else:
	community['network_v6'].append(addr)

	# IP address of SNMP client allowed to contact system
	if conf.exists('community {0} client'.format(name)):
	for addr in conf.return_values('community {0} client'.format(name)):
	if is_ipv4(addr):
	community['network_v4'].append(addr)
	else:
	community['network_v6'].append(addr)

	if (len(community['network_v4']) > 0) or (len(community['network_v6']) > 0):
	community['has_source'] = True

	snmp['communities'].append(community)

	if conf.exists('contact'):
	snmp['contact'] = conf.return_value('contact')

	if conf.exists('description'):
	snmp['description'] = conf.return_value('description')

	if conf.exists('listen-address'):
	for addr in conf.list_nodes('listen-address'):
	port = '161'
	if conf.exists('listen-address {0} port'.format(addr)):
	port = conf.return_value('listen-address {0} port'.format(addr))

	snmp['listen_address'].append((addr, port))

	# 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://phabricator.vyos.net/T850
	if not '127.0.0.1' in conf.list_nodes('listen-address'):
	snmp['listen_address'].append(('127.0.0.1', '161'))

	if not '::1' in conf.list_nodes('listen-address'):
	snmp['listen_address'].append(('::1', '161'))

	if conf.exists('location'):
	snmp['location'] = conf.return_value('location')

	if conf.exists('smux-peer'):
	snmp['smux_peers'] = conf.return_values('smux-peer')

	if conf.exists('trap-source'):
	snmp['trap_source'] = conf.return_value('trap-source')

	if conf.exists('trap-target'):
	for target in conf.list_nodes('trap-target'):
	trap_tgt = {
	'target': target,
	'community': '',
	'port': ''
	}

	if conf.exists('trap-target {0} community'.format(target)):
	trap_tgt['community'] = conf.return_value('trap-target {0} community'.format(target))

	if conf.exists('trap-target {0} port'.format(target)):
	trap_tgt['port'] = conf.return_value('trap-target {0} port'.format(target))

	snmp['trap_targets'].append(trap_tgt)

	if conf.exists('script-extensions'):
	for extname in conf.list_nodes('script-extensions extension-name'):
	conf_script = conf.return_value('script-extensions extension-name {} script'.format(extname))
	# if script has not absolute path, use pre configured path
	if "/" not in conf_script:
	conf_script = default_script_dir + conf_script

	extension = {
	'name': extname,
	'script' : conf_script
	}

	snmp['script_ext'].append(extension)

	if conf.exists('vrf'):
	# Append key to dict but don't place it in the default dictionary.
	# This is required to make the override.conf.tmpl work until we
	# migrate to get_config_dict().
	snmp['vrf'] = conf.return_value('vrf')


	#########################################################################
	# ____ _ _ __ __ ____ _____ #
	# / ___\|\| \ \| \| \/ \| _ \ __ _\|___ / #
	# \___ \\| \\| \| \|\/\| \| \|_) \| \ \ / / \|_ \ #
	# ___) \| \|\ \| \| \| \| __/ \ V / ___) \| #
	# \|____/\|_\| \_\|_\| \|_\|_\| \_/ \|____/ #
	# #
	# now take care about the fancy SNMP v3 stuff, or bail out eraly #
	#########################################################################
	if not conf.exists('v3'):
	return snmp
	else:
	snmp['v3_enabled'] = True

	# 'set service snmp v3 engineid'
	if conf.exists('v3 engineid'):
	snmp['v3_engineid'] = conf.return_value('v3 engineid')

	# 'set service snmp v3 group'
	if conf.exists('v3 group'):
	for group in conf.list_nodes('v3 group'):
	v3_group = {
	'name': group,
	'mode': 'ro',
	'seclevel': 'auth',
	'view': ''
	}

	if conf.exists('v3 group {0} mode'.format(group)):
	v3_group['mode'] = conf.return_value('v3 group {0} mode'.format(group))

	if conf.exists('v3 group {0} seclevel'.format(group)):
	v3_group['seclevel'] = conf.return_value('v3 group {0} seclevel'.format(group))

	if conf.exists('v3 group {0} view'.format(group)):
	v3_group['view'] = conf.return_value('v3 group {0} view'.format(group))

	snmp['v3_groups'].append(v3_group)

	# 'set service snmp v3 trap-target'
	if conf.exists('v3 trap-target'):
	for trap in conf.list_nodes('v3 trap-target'):
	trap_cfg = {
	'ipAddr': trap,
	'secName': '',
	'authProtocol': 'md5',
	'authPassword': '',
	'authMasterKey': '',
	'privProtocol': 'des',
	'privPassword': '',
	'privMasterKey': '',
	'ipProto': 'udp',
	'ipPort': '162',
	'type': '',
	'secLevel': 'noAuthNoPriv'
	}

	if conf.exists('v3 trap-target {0} user'.format(trap)):
	# Set the securityName used for authenticated SNMPv3 messages.
	trap_cfg['secName'] = conf.return_value('v3 trap-target {0} user'.format(trap))

	if conf.exists('v3 trap-target {0} auth type'.format(trap)):
	# Set the authentication protocol (MD5 or SHA) used for authenticated SNMPv3 messages
	# cmdline option '-a'
	trap_cfg['authProtocol'] = conf.return_value('v3 trap-target {0} auth type'.format(trap))

	if conf.exists('v3 trap-target {0} auth plaintext-password'.format(trap)):
	# Set the authentication pass phrase used for authenticated SNMPv3 messages.
	# cmdline option '-A'
	trap_cfg['authPassword'] = conf.return_value('v3 trap-target {0} auth plaintext-password'.format(trap))

	if conf.exists('v3 trap-target {0} auth encrypted-password'.format(trap)):
	# Sets the keys to be used for SNMPv3 transactions. These options allow you to set the master authentication keys.
	# cmdline option '-3m'
	trap_cfg['authMasterKey'] = conf.return_value('v3 trap-target {0} auth encrypted-password'.format(trap))

	if conf.exists('v3 trap-target {0} privacy type'.format(trap)):
	# Set the privacy protocol (DES or AES) used for encrypted SNMPv3 messages.
	# cmdline option '-x'
	trap_cfg['privProtocol'] = conf.return_value('v3 trap-target {0} privacy type'.format(trap))

	if conf.exists('v3 trap-target {0} privacy plaintext-password'.format(trap)):
	# Set the privacy pass phrase used for encrypted SNMPv3 messages.
	# cmdline option '-X'
	trap_cfg['privPassword'] = conf.return_value('v3 trap-target {0} privacy plaintext-password'.format(trap))

	if conf.exists('v3 trap-target {0} privacy encrypted-password'.format(trap)):
	# Sets the keys to be used for SNMPv3 transactions. These options allow you to set the master encryption keys.
	# cmdline option '-3M'
	trap_cfg['privMasterKey'] = conf.return_value('v3 trap-target {0} privacy encrypted-password'.format(trap))

	if conf.exists('v3 trap-target {0} protocol'.format(trap)):
	trap_cfg['ipProto'] = conf.return_value('v3 trap-target {0} protocol'.format(trap))

	if conf.exists('v3 trap-target {0} port'.format(trap)):
	trap_cfg['ipPort'] = conf.return_value('v3 trap-target {0} port'.format(trap))

	if conf.exists('v3 trap-target {0} type'.format(trap)):
	trap_cfg['type'] = conf.return_value('v3 trap-target {0} type'.format(trap))

	# Determine securityLevel used for SNMPv3 messages (noAuthNoPriv\|authNoPriv\|authPriv).
	# Appropriate pass phrase(s) must provided when using any level higher than noAuthNoPriv.
	if trap_cfg['authPassword'] or trap_cfg['authMasterKey']:
	if trap_cfg['privProtocol'] or trap_cfg['privPassword']:
	trap_cfg['secLevel'] = 'authPriv'
	else:
	trap_cfg['secLevel'] = 'authNoPriv'

	snmp['v3_traps'].append(trap_cfg)

	# 'set service snmp v3 user'
	if conf.exists('v3 user'):
	for user in conf.list_nodes('v3 user'):
	user_cfg = {
	'name': user,
	'authMasterKey': '',
	'authPassword': '',
	'authProtocol': 'md5',
	'authOID': 'none',
	'group': '',
	'mode': 'ro',
	'privMasterKey': '',
	'privPassword': '',
	'privOID': '',
	'privProtocol': 'des'
	}

	# v3 user {0} auth
	if conf.exists('v3 user {0} auth encrypted-password'.format(user)):
	user_cfg['authMasterKey'] = conf.return_value('v3 user {0} auth encrypted-password'.format(user))

	if conf.exists('v3 user {0} auth plaintext-password'.format(user)):
	user_cfg['authPassword'] = conf.return_value('v3 user {0} auth plaintext-password'.format(user))

	# load default value
	type = user_cfg['authProtocol']
	if conf.exists('v3 user {0} auth type'.format(user)):
	type = conf.return_value('v3 user {0} auth type'.format(user))

	# (re-)update with either default value or value from CLI
	user_cfg['authProtocol'] = type
	user_cfg['authOID'] = OIDs[type]

	# v3 user {0} group
	if conf.exists('v3 user {0} group'.format(user)):
	user_cfg['group'] = conf.return_value('v3 user {0} group'.format(user))

	# v3 user {0} mode
	if conf.exists('v3 user {0} mode'.format(user)):
	user_cfg['mode'] = conf.return_value('v3 user {0} mode'.format(user))

	# v3 user {0} privacy
	if conf.exists('v3 user {0} privacy encrypted-password'.format(user)):
	user_cfg['privMasterKey'] = conf.return_value('v3 user {0} privacy encrypted-password'.format(user))

	if conf.exists('v3 user {0} privacy plaintext-password'.format(user)):
	user_cfg['privPassword'] = conf.return_value('v3 user {0} privacy plaintext-password'.format(user))

	# load default value
	type = user_cfg['privProtocol']
	if conf.exists('v3 user {0} privacy type'.format(user)):
	type = conf.return_value('v3 user {0} privacy type'.format(user))

	# (re-)update with either default value or value from CLI
	user_cfg['privProtocol'] = type
	user_cfg['privOID'] = OIDs[type]

	snmp['v3_users'].append(user_cfg)

	# 'set service snmp v3 view'
	if conf.exists('v3 view'):
	for view in conf.list_nodes('v3 view'):
	view_cfg = {
	'name': view,
	'oids': []
	}

	if conf.exists('v3 view {0} oid'.format(view)):
	for oid in conf.list_nodes('v3 view {0} oid'.format(view)):
	oid_cfg = {
	'oid': oid
	}
	view_cfg['oids'].append(oid_cfg)
	snmp['v3_views'].append(view_cfg)

	return snmp

	def verify(snmp):
	if snmp is None:
	# we can not delete SNMP when LLDP is configured with SNMP
	conf = Config()
	if conf.exists('service lldp snmp enable'):
	raise ConfigError('Can not delete SNMP service, as LLDP still uses SNMP!')

	return None

	### check if the configured script actually exist
	if snmp['script_ext']:
	for ext in snmp['script_ext']:
	if not os.path.isfile(ext['script']):
	print ("WARNING: script: {} doesn't exist".format(ext['script']))
	else:
	chmod_755(ext['script'])

	for listen in snmp['listen_address']:
	addr = listen[0]
	port = listen[1]

	if is_ipv4(addr):
	# example: udp:127.0.0.1:161
	listen = 'udp:' + addr + ':' + port
	elif snmp['ipv6_enabled']:
	# example: udp6:[::1]:161
	listen = 'udp6:' + '[' + addr + ']' + ':' + port

	# We only wan't to configure addresses that exist on the system.
	# Hint the user if they don't exist
	if is_addr_assigned(addr):
	snmp['listen_on'].append(listen)
	else:
	print('WARNING: SNMP listen address {0} not configured!'.format(addr))

	verify_vrf(snmp)

	# bail out early if SNMP v3 is not configured
	if not snmp['v3_enabled']:
	return None

	if 'v3_groups' in snmp.keys():
	for group in snmp['v3_groups']:
	#
	# A view must exist prior to mapping it into a group
	#
	if 'view' in group.keys():
	error = True
	if 'v3_views' in snmp.keys():
	for view in snmp['v3_views']:
	if view['name'] == group['view']:
	error = False
	if error:
	raise ConfigError('You must create view "{0}" first'.format(group['view']))
	else:
	raise ConfigError('"view" must be specified')

	if not 'mode' in group.keys():
	raise ConfigError('"mode" must be specified')

	if not 'seclevel' in group.keys():
	raise ConfigError('"seclevel" must be specified')

	if 'v3_traps' in snmp.keys():
	for trap in snmp['v3_traps']:
	if trap['authPassword'] and trap['authMasterKey']:
	raise ConfigError('Must specify only one of encrypted-password/plaintext-key for trap auth')

	if trap['authPassword'] == '' and trap['authMasterKey'] == '':
	raise ConfigError('Must specify encrypted-password or plaintext-key for trap auth')

	if trap['privPassword'] and trap['privMasterKey']:
	raise ConfigError('Must specify only one of encrypted-password/plaintext-key for trap privacy')

	if trap['privPassword'] == '' and trap['privMasterKey'] == '':
	raise ConfigError('Must specify encrypted-password or plaintext-key for trap privacy')

	if not 'type' in trap.keys():
	raise ConfigError('v3 trap: "type" must be specified')

	if not 'authPassword' and 'authMasterKey' in trap.keys():
	raise ConfigError('v3 trap: "auth" must be specified')

	if not 'authProtocol' in trap.keys():
	raise ConfigError('v3 trap: "protocol" must be specified')

	if not 'privPassword' and 'privMasterKey' in trap.keys():
	raise ConfigError('v3 trap: "user" must be specified')

	if 'v3_users' in snmp.keys():
	for user in snmp['v3_users']:
	#
	# Group must exist prior to mapping it into a group
	# seclevel will be extracted from group
	#
	if user['group']:
	error = True
	if 'v3_groups' in snmp.keys():
	for group in snmp['v3_groups']:
	if group['name'] == user['group']:
	seclevel = group['seclevel']
	error = False

	if error:
	raise ConfigError('You must create group "{0}" first'.format(user['group']))

	# Depending on the configured security level the user has to provide additional info
	if (not user['authPassword'] and not user['authMasterKey']):
	raise ConfigError('Must specify encrypted-password or plaintext-key for user auth')

	if user['privPassword'] == '' and user['privMasterKey'] == '':
	raise ConfigError('Must specify encrypted-password or plaintext-key for user privacy')

	if user['mode'] == '':
	raise ConfigError('Must specify user mode ro/rw')

	if 'v3_views' in snmp.keys():
	for view in snmp['v3_views']:
	if not view['oids']:
	raise ConfigError('Must configure an oid')

	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('systemctl stop snmpd.service')
	config_files = [config_file_client, config_file_daemon, config_file_access,
	config_file_user, systemd_override]
	for file in config_files:
	rmfile(file)

	if not snmp:
	return None

	if 'v3_users' in snmp.keys():
	# net-snmp is now regenerating the configuration file in the background
	# thus we need to re-open and re-read the file as the content changed.
	# After that we can no read the encrypted password from the config and
	# replace the CLI plaintext password with its encrypted version.
	os.environ["vyos_libexec_dir"] = "/usr/libexec/vyos"

	for user in snmp['v3_users']:
	if user['authProtocol'] == 'sha':
	hash = plaintext_to_sha1
	else:
	hash = plaintext_to_md5

	if user['authPassword']:
	user['authMasterKey'] = hash(user['authPassword'], snmp['v3_engineid'])
	user['authPassword'] = ''

	call('/opt/vyatta/sbin/my_set service snmp v3 user "{name}" auth encrypted-password "{authMasterKey}" > /dev/null'.format(**user))
	call('/opt/vyatta/sbin/my_delete service snmp v3 user "{name}" auth plaintext-password > /dev/null'.format(**user))

	if user['privPassword']:
	user['privMasterKey'] = hash(user['privPassword'], snmp['v3_engineid'])
	user['privPassword'] = ''

	call('/opt/vyatta/sbin/my_set service snmp v3 user "{name}" privacy encrypted-password "{privMasterKey}" > /dev/null'.format(**user))
	call('/opt/vyatta/sbin/my_delete service snmp v3 user "{name}" privacy plaintext-password > /dev/null'.format(**user))

	# Write client config file
	render(config_file_client, 'snmp/etc.snmp.conf.tmpl', snmp)
	# Write server config file
	render(config_file_daemon, 'snmp/etc.snmpd.conf.tmpl', snmp)
	# Write access rights config file
	render(config_file_access, 'snmp/usr.snmpd.conf.tmpl', snmp)
	# Write access rights config file
	render(config_file_user, 'snmp/var.snmpd.conf.tmpl', snmp)
	# Write daemon configuration file
	render(systemd_override, 'snmp/override.conf.tmpl', snmp)

	return None

	def apply(snmp):
	# Always reload systemd manager configuration
	call('systemctl daemon-reload')

	if not snmp:
	return None

	# start SNMP daemon
	call('systemctl restart snmpd.service')

	# Enable AgentX in FRR
	call('vtysh -c "configure terminal" -c "agentx" >/dev/null')

	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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