ldap-acl-milter LDAP-schema

This commit is contained in:
Dominik Chilla 2019-03-27 20:12:34 +01:00
parent 683a9803a6
commit 5de8c5c8d9
4 changed files with 293 additions and 64 deletions

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@ -0,0 +1,89 @@
# ldap-acl-milter https://github.com/chillout2k/ldap-acl-milter
#
# https://www.iana.org/assignments/enterprise-numbers/enterprise-numbers
# DC IT-Consulting
# Dominik Chilla
#
# OID prefix: 1.3.6.1.4.1.53501
#
# Attributes: 1.3.6.1.4.1.53501.1.1
attributetype ( 1.3.6.1.4.1.53501.1.1.1
NAME 'policyID'
DESC 'Policy ID'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{128}
SINGLE-VALUE)
attributetype ( 1.3.6.1.4.1.53501.1.1.2
NAME 'authType'
DESC 'Authentication type: sasl_user, client_addr, none'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{256}
SINGLE-VALUE)
attributetype ( 1.3.6.1.4.1.53501.1.1.3
NAME 'allowedSenders'
DESC 'Allowed RFC5321.from'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{254})
attributetype ( 1.3.6.1.4.1.53501.1.1.4
NAME 'allowedRcpts'
DESC 'Denied RFC5321.to'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{254})
attributetype ( 1.3.6.1.4.1.53501.1.1.5
NAME 'deniedSenders'
DESC 'Allowed RFC5321.from'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{254})
attributetype ( 1.3.6.1.4.1.53501.1.1.6
NAME 'deniedRcpts'
DESC 'Denied RFC5321.to'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{254})
attributetype ( 1.3.6.1.4.1.53501.1.1.7
NAME 'allowedClientAddr'
DESC 'Allowed client IPv4/IPv6 address'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{64})
attributetype ( 1.3.6.1.4.1.53501.1.1.8
NAME 'deniedClientAddr'
DESC 'Denied client IPv4/IPv6 address'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{64})
attributetype ( 1.3.6.1.4.1.53501.1.1.9
NAME 'allowedSaslUser'
DESC 'Allowed SASL authentication user'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{64})
attributetype ( 1.3.6.1.4.1.53501.1.1.10
NAME 'extBLOB'
DESC 'placeholder for binary extensions'
EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{4096})
#
# Objects: 1.3.6.1.4.1.53501.1.2
#
objectclass ( 1.3.6.1.4.1.53501.1.2.1
NAME 'lamPolicy'
DESC 'ldap-acl-milter policy'
SUP top
STRUCTURAL
MUST ( policyID $ allowedRcpts $ allowedSenders )
MAY ( authType $ deniedSenders $ deniedRcpts $ allowedClientAddr $ deniedClientAddr $ allowedSaslUser $ extBLOB ))

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@ -1,10 +1,23 @@
# ldap-acl-milter
A lightweight, fast and thread-safe python3 [milter](http://www.postfix.org/MILTER_README.html) on top of [sdgathman/pymilter](https://github.com/sdgathman/pymilter) for basic Access Control (ACL) scenarios. The milter consumes policies from LDAP based on custom queries with trivial templating support (%from% = RFC5321.from; %rcpt% = RFC5321.rcpt).
A lightweight, fast and thread-safe python3 [milter](http://www.postfix.org/MILTER_README.html) on top of [sdgathman/pymilter](https://github.com/sdgathman/pymilter) for basic Access Control (ACL) scenarios. The milter consumes policies from LDAP based on custom queries with trivial templating support:
In the case, one already has a LDAP server running with the [amavis schema](https://www.ijs.si/software/amavisd/LDAP.schema.txt), the 'amavisWhitelistSender' attribute could be reused. The filtering direction (inbound or outbound) can be simply controlled by swapping the %from% and %rcpt% placeholders within the LDAP query template. Please have a look at the docker-compose.yml example.
* %client_addr% = IPv(4|6) address of SMTP client
* %sasl_user% = user name of SASL authenticated user
* %from% = RFC5321.from
* %from_domain% = RFC5321.from_domain
* %rcpt% = RFC5321.rcpt
* %rcpt_domain% RFC5321.rcpt_domain
In the case, one already has a LDAP server running with the [amavis schema](https://www.ijs.si/software/amavisd/LDAP.schema.txt), the 'amavisWhitelistSender' attribute could be reused. The filtering direction (inbound or outbound) can be simply controlled by swapping the %from% and %rcpt% placeholders within the LDAP query template. Please have a look at the docker-compose.yml example below.
The connection to the LDAP server is always persistent: one LDAP-bind is shared among all milter-threads, which makes it more efficient due to less communication overhead (which also implies transport encryption with TLS). Thus, LDAP interactions with 2 msec. and less are realistic, depending on your environment like network round-trip-times or the load of your LDAP server. A very swag LDAP setup is to use a local read-only LDAP replica, which syncs over network with a couple of LDAP masters: [OpenLDAP does it for free!](https://www.openldap.org/doc/admin24/replication.html). On the one hand, this aproach eliminates network round trip times while reading from a UNIX-socket, and on the other, performance bottlenecks on a shared, centralized and (heavy) utilized LDAP server.
### ldap-acl-milter´s own LDAP-schema
Yes, there´s one! Check out the LDAP-directory ;-)
### Uniqueness of LDAP attributes
In case of OpenLDAP, just use the [unique overlay](https://www.openldap.org/doc/admin24/overlays.html). Another aproach to ensure attribute uniqueness is to do it in some programmatic way which is more complex but more flexible.
### Deployment paradigm
The intention of this project is to deploy the milter ALWAYS AND ONLY as an [OCI compliant](https://www.opencontainers.org) container. In this case it´s [docker](https://www.docker.com). The main reason is that I´m not interested (and familiar with) in building distribution packages like .rpm, .deb, etc.. Furthermore I´m not really a fan of 'wild and uncontrollable' software deployments like: get the code, compile it and finaly install the results 'somewhere' in the filesystem. In terms of software deployment docker provides wonderful possibilities, which I don´t want to miss anymore... No matter if in development, QA or production stage.
@ -35,6 +48,8 @@ services:
image: "ldap-acl-milter/debian:19.02_master"
restart: unless-stopped
environment:
# default: info. Possible: info, warning, error and debug
LOG_LEVEL: debug
#LDAP_SERVER: ldap://ldap-slave.example.local:389
LDAP_SERVER: ldapi:///socket//slapd//slapd
LDAP_BINDDN: uid=lam,ou=applications,dc=example,dc=org
@ -43,11 +58,24 @@ services:
# This example LDAP query is for inbound filtering
# where the 'mail' attribute equals to the recipient
# and the 'amavisWhitelistSender' attribute the eligible sender
LDAP_QUERY: (&(mail=%rcpt%)(amavisWhitelistSender=%from%))
#LDAP_QUERY: (&(mail=%rcpt%)(amavisWhitelistSender=%from%))
#LDAP_QUERY: (&(mail=%rcpt%)(|(amavisWhitelistSender=*@%from_domain%)(amavisWhitelistSender=%from%)))
# LDAP_QUERY: (&(|(mail=%rcpt%)(mail=*@%rcpt_domain%))(|(amavisWhitelistSender=*@%from_domain%)(amavisWhitelistSender=%from%)))
# This enables the use of own ldap-acl-milter LDAP schema. Default: False
# Setting MILTER_SCHEMA: True disables the LDAP_QUERY parameter!
MILTER_SCHEMA: 'True'
# If MILTER_SCHEMA_WILDCARDS is set to True, the milter gets all valid senders
# per recipient and checks binary as well as per wildcard (*) if the senders
# matches. This only works if MILTER_SCHEMA is enabled!
MILTER_SCHEMA_WILDCARDS: 'False'
# default: test. Possible: test, reject
MILTER_MODE: 'reject'
MILTER_NAME: some-another-milter-name
# Default: UNIX-socket located under /socket/ldap-acl-milter
# https://pythonhosted.org/pymilter/namespacemilter.html#a266a6e09897499d8b1ae0e20f0d2be73
#MILTER_SOCKET: inet6:8020
MILTER_REJECT_MESSAGE: Message rejected due to security policy
#MILTER_REJECT_MESSAGE: Message rejected due to security policy
#MILTER_TMPFAIL_MESSAGE: Message temporary rejected. Please try again later ;)
hostname: ldap-acl-milter
volumes:
- "lam_socket:/socket/:rw"

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@ -7,90 +7,175 @@ import os
import logging
import string
import random
import re
from timeit import default_timer as timer
# Globals...
g_milter_name = 'ldap-acl-milter'
g_milter_socket = '/socket/' + g_milter_name
g_milter_reject_message = 'Absender/Empfaenger passen nicht!'
g_milter_reject_message = 'Security policy violation!'
g_milter_tmpfail_message = 'Service temporarily not available! Please try again later.'
g_ldap_conn = None
# ...with mostly senseless defaults ;)
g_ldap_server = 'ldap://127.0.0.1:389'
g_ldap_binddn = 'cn=ldap-reader,ou=binds,dc=example,dc=org'
g_ldap_bindpw = 'TopSecret;-)'
g_ldap_base = 'ou=users,dc=example,dc=org'
g_ldap_query = '(&(mail=%rcpt%)(allowedEnvelopeSender=%from%))'
logging.basicConfig(
filename=None, # log to stdout
format='%(asctime)s: %(levelname)s %(message)s',
level=logging.INFO
)
g_re_domain = re.compile(r'^\S+@(\S+)$')
g_loglevel = logging.INFO
g_milter_mode = 'test'
g_milter_schema = False
g_milter_schema_wildcards = False # works only if g_milter_schema == True
class LdapAclMilter(Milter.Base):
# Each new connection is handled in an own thread
def __init__(self):
self.time_start = timer()
self.id = Milter.uniqueID()
self.ldap_conn = g_ldap_conn
self.R = []
self.client_addr = None
self.env_from = None
self.env_from_domain = None
self.sasl_user = 'not_authenticated'
# recipients list
self.env_rcpts = []
# https://stackoverflow.com/a/2257449
self.mconn_id = ''.join(
self.mconn_id = g_milter_name + ': ' + ''.join(
random.choice(string.ascii_lowercase + string.digits) for _ in range(8)
)
# Not registered/used callbacks
@Milter.nocallback
def connect(self, IPname, family, hostaddr):
return self.CONTINUE
@Milter.nocallback
def hello(self, heloname):
return self.CONTINUE
return Milter.CONTINUE
@Milter.nocallback
def header(self, name, hval):
return self.CONTINUE
return Milter.CONTINUE
@Milter.nocallback
def eoh(self):
return self.CONTINUE
return Milter.CONTINUE
@Milter.nocallback
def body(self, chunk):
return self.CONTINUE
return Milter.CONTINUE
def connect(self, IPname, family, hostaddr):
self.client_addr = hostaddr[0]
logging.debug(self.mconn_id +
"/CONNECT client_addr=[" + self.client_addr + "]:" + str(hostaddr[1])
)
return Milter.CONTINUE
def envfrom(self, mailfrom, *str):
if mailfrom == '<>':
ex = str(self.mconn_id + '/FROM Envelope null-sender not allowed!')
logging.error(ex)
self.setreply('550','5.7.1',ex)
Milter.REJECT
try:
# this may fail, if no SASL authentication preceded
sasl_user = self.getsymval('{auth_authen}')
if sasl_user != None:
self.sasl_user = sasl_user
logging.debug(self.mconn_id + "/FROM sasl_user: " + self.sasl_user)
except:
logging.error(self.mconn_id + "/FROM " + str(sys.exc_info()))
mailfrom = mailfrom.replace("<","")
mailfrom = mailfrom.replace(">","")
self.F = mailfrom
self.env_from = mailfrom
m = g_re_domain.match(self.env_from)
if m == None:
logging.error(self.mconn_id + "/FROM " +
"Could not determine domain of 5321.from: " + self.env_from
)
self.setreply('450','4.7.1', g_milter_tmpfail_message)
return Milter.TEMPFAIL
self.env_from_domain = m.group(1)
logging.debug(self.mconn_id +
"/FROM env_from_domain: " + self.env_from_domain
)
return Milter.CONTINUE
def envrcpt(self, to, *str):
time_start = timer()
to = to.replace("<","")
to = to.replace(">","")
m = g_re_domain.match(to)
if m == None:
logging.error(self.mconn_id + "/RCPT " +
"Could not determine domain of 5321.to: " + to
)
self.setreply('450','4.7.1', g_milter_tmpfail_message)
return Milter.TEMPFAIL
rcpt_domain = m.group(1)
logging.debug(self.mconn_id +
"/RCPT rcpt_domain: " + rcpt_domain
)
time_end = None
try:
query = g_ldap_query.replace("%rcpt%",to)
query = query.replace("%from%", self.F)
self.ldap_conn.search(g_ldap_base, query)
time_end = timer()
if len(self.ldap_conn.entries) == 0:
self.R.append({
"rcpt": to, "reason": g_milter_reject_message,
"time_start":time_start, "time_end":time_end
})
self.setreply('550','5.7.1',
'Sender does not comply with recipients policy!'
)
logging.info(self.mconn_id + "/RCPT " + g_milter_reject_message)
return Milter.REJECT
if g_milter_schema == True:
# LDAP-ACL-Milter own schema
if g_milter_schema_wildcards == True:
# TODO!
pass
else:
# Authentication hierarchy!
# 1. SASL authenticated
# TODO: if auth_type sasl_user, check if authenticated user matches sasl_user and
# TODO: check if sender/recipient pair match
# 2. Client-IP authenticated
# TODO: if auth_type client_addr, check if client-ip matches client_addr
# TODO: check if sender/recipient pair match
# 3. not authenticated
# TODO: ldap-search with excluded sasl_user and client_addr attributes!
self.ldap_conn.search(g_ldap_base,
"(&(allowedRcpts="+to+")(allowedSenders="+self.env_from+"))"
)
time_end = timer()
if len(self.ldap_conn.entries) == 0:
self.env_rcpts.append({
"rcpt": to, "reason": g_milter_reject_message,
"time_start":time_start, "time_end":time_end
})
if g_milter_mode == 'reject':
logging.info(self.mconn_id + "/RCPT " + g_milter_reject_message)
self.setreply('550','5.7.1',
g_milter_reject_message + ' (' + self.mconn_id + ')'
)
return Milter.REJECT
else:
logging.info(self.mconn_id + "/RCPT TEST_MODE " +
g_milter_reject_message
)
return Milter.CONTINUE
else:
# Custom LDAP schema
# 'build' a LDAP query per recipient
# replace all placeholders in query templates
query = g_ldap_query.replace("%rcpt%",to)
query = query.replace("%from%", self.env_from)
query = query.replace("%client_addr%", self.client_addr)
query = query.replace("%sasl_user%", self.sasl_user)
query = query.replace("%from_domain%", self.env_from_domain)
query = query.replace("%rcpt_domain%", rcpt_domain)
logging.debug(self.mconn_id + "/RCPT " + query)
self.ldap_conn.search(g_ldap_base, query)
time_end = timer()
if len(self.ldap_conn.entries) == 0:
self.env_rcpts.append({
"rcpt": to, "reason": g_milter_reject_message,
"time_start":time_start, "time_end":time_end
})
if g_milter_mode == 'reject':
logging.info(self.mconn_id + "/RCPT " + g_milter_reject_message)
self.setreply('550','5.7.1',
g_milter_reject_message + ' (' + self.mconn_id + ')'
)
return Milter.REJECT
else:
logging.info(self.mconn_id + "/RCPT TEST_MODE " +
g_milter_reject_message
)
return Milter.CONTINUE
except LDAPOperationResult as e:
logging.warn(self.mconn_id + "/RCPT LDAP Exception (envrcpt): " + str(e))
self.setreply('451','4.7.1',
'Service temporarily not available! Please try again later.'
)
logging.warn(self.mconn_id + "/RCPT LDAP: " + str(e))
self.setreply('451', '4.7.1', g_milter_tmpfail_message)
return Milter.TEMPFAIL
self.R.append({
self.env_rcpts.append({
"rcpt": to, "reason":'pass',"time_start":time_start,"time_end":time_end
})
return Milter.CONTINUE
@ -100,19 +185,17 @@ class LdapAclMilter(Milter.Base):
# and therefore not available until DATA command
self.queue_id = self.getsymval('i')
try:
for rcpt in self.R:
for rcpt in self.env_rcpts:
duration = rcpt['time_end'] - rcpt['time_start']
logging.info(self.mconn_id + "/DATA " + self.queue_id +
": 5321.from=<" + self.F + "> 5321.rcpt=<" +
": 5321.from=<" + self.env_from + "> 5321.rcpt=<" +
rcpt['rcpt'] + "> reason: " + rcpt['reason'] +
" duration: " + str(duration) + " sec."
)
except:
ex = str(self.mconn_id + "/DATA " + self.queue_id +
": Exception (data): " + sys.exc_info()
)
logging.warn(ex)
self.setreply('451','4.7.1', ex)
logging.warn(self.mconn_id + "/DATA " + self.queue_id +
": " + str(sys.exc_info()))
self.setreply('451', '4.7.1', g_milter_tmpfail_message)
return Milter.TEMPFAIL
return Milter.CONTINUE
@ -121,7 +204,7 @@ class LdapAclMilter(Milter.Base):
time_end = timer()
duration = time_end - self.time_start
logging.info(self.mconn_id + "/EOM " + self.queue_id +
" processing: " + str(duration) + " sec."
" processed in " + str(duration) + " sec."
)
return Milter.CONTINUE
@ -136,6 +219,31 @@ class LdapAclMilter(Milter.Base):
if __name__ == "__main__":
try:
if 'LOG_LEVEL' in os.environ:
if re.match(r'^info$', os.environ['LOG_LEVEL'], re.IGNORECASE):
g_loglevel = logging.INFO
elif re.match(r'^warn|warning$', os.environ['LOG_LEVEL'], re.IGNORECASE):
g_loglevel = logging.WARN
elif re.match(r'^error$', os.environ['LOG_LEVEL'], re.IGNORECASE):
g_loglevel = logging.ERROR
elif re.match(r'debug', os.environ['LOG_LEVEL'], re.IGNORECASE):
g_loglevel = logging.DEBUG
logging.basicConfig(
filename=None, # log to stdout
format='%(asctime)s: %(levelname)s %(message)s',
level=g_loglevel
)
if 'MILTER_MODE' in os.environ:
if re.match(r'^test|reject$',os.environ['MILTER_MODE'], re.IGNORECASE):
g_milter_mode = os.environ['MILTER_MODE']
if 'MILTER_NAME' in os.environ:
g_milter_name = os.environ['MILTER_NAME']
if 'MILTER_SCHEMA' in os.environ:
if re.match(r'^true$', os.environ['MILTER_SCHEMA'], re.IGNORECASE):
g_milter_schema = True
if 'MILTER_SCHEMA_WILDCARDS' in os.environ:
if re.match(r'^true$', os.environ['MILTER_SCHEMA_WILDCARDS'], re.IGNORECASE):
g_milter_schema_wildcards = True
if 'LDAP_SERVER' not in os.environ:
logging.error("Missing ENV[LDAP_SERVER], e.g. " + g_ldap_server)
sys.exit(1)
@ -149,19 +257,20 @@ if __name__ == "__main__":
sys.exit(1)
g_ldap_base = os.environ['LDAP_BASE']
if 'LDAP_QUERY' not in os.environ:
logging.error("Missing ENV[LDAP_QUERY], e.g. " + g_ldap_query)
sys.exit(1)
g_ldap_query = os.environ['LDAP_QUERY']
if g_milter_schema == False:
logging.error(
"ENV[MILTER_SCHEMA] is disabled and ENV[LDAP_QUERY] is not set instead!"
)
sys.exit(1)
if 'LDAP_QUERY' in os.environ:
g_ldap_query = os.environ['LDAP_QUERY']
if 'MILTER_SOCKET' in os.environ:
g_milter_socket = os.environ['MILTER_SOCKET']
if 'MILTER_REJECT_MESSAGE' in os.environ:
g_milter_reject_message = os.environ['MILTER_REJECT_MESSAGE']
#server_pool = ServerPool(None, pool_strategy='ROUND_ROBIN', active=False, exhaust=False)
if 'MILTER_TMPFAIL_MESSAGE' in os.environ:
g_milter_tmpfail_message = os.environ['MILTER_TMPFAIL_MESSAGE']
server = Server(g_ldap_server, get_info=NONE)
#server_pool.add(server)
#server2 = Server('ldap://ldap-master-zdf.zwackl.local:389', get_info=NONE)
#server_pool.add(server2)
#g_ldap_conn = Connection(server_pool,
g_ldap_conn = Connection(server,
g_ldap_binddn, g_ldap_bindpw,
auto_bind=True, raise_exceptions=True,
@ -178,7 +287,10 @@ if __name__ == "__main__":
# Tell the MTA which features we use
flags = Milter.ADDHDRS
Milter.set_flags(flags)
logging.info("Startup " + g_milter_name + "@socket: " + g_milter_socket)
logging.info("Startup " + g_milter_name +
"@socket: " + g_milter_socket +
" in mode: " + g_milter_mode
)
Milter.runmilter(g_milter_name,g_milter_socket,timeout,True)
logging.info("Shutdown " + g_milter_name)
except:

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@ -22,9 +22,9 @@ fi
IMAGES="ldap-acl-milter"
for IMAGE in ${IMAGES}; do
# --build-arg http_proxy=http://wprx-zdf.zwackl.local:3128 \
# --build-arg https_proxy=http://wprx-zdf.zwackl.local:3128 \
/usr/bin/docker build \
--build-arg http_proxy=http://wprx-zdf.zwackl.local:3128 \
--build-arg https_proxy=http://wprx-zdf.zwackl.local:3128 \
-t "${IMAGE}/${BASEOS}:${VERSION}_${BRANCH}" \
-f "docker/${BASEOS}/Dockerfile" .
# /usr/bin/docker tag "${IMAGE}/${BASEOS}:${VERSION}_${BRANCH}" "${REGISTRY}/${IMAGE}/${BASEOS}:${VERSION}_${BRANCH}"