diff --git a/README.md b/README.md index 897e5ed..c04c499 100644 --- a/README.md +++ b/README.md @@ -1,38 +1,68 @@ # 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). + +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. + +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. + +### 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. ### docker-compose.yml +The following [docker-compose](https://docs.docker.com/compose/) file demonstrates how such a setup could be orchestrated on a single docker host or on a docker swarm cluster. In this context we use [postfix](http://www.postfix.org) as our milter-capable MTA and OpenLDAP as local LDAP replica. ``` version: '3' volumes: lam_socket: + openldap_spool: + openldap_socket: services: + openldap: + image: "your/favorite/openldap/image" + restart: unless-stopped + hostname: openldap + volumes: + - "./config/openldap:/etc/openldap:rw" + - "openldap_spool:/var/openldap-data:rw" + - "openldap_socket:/socket:rw" + ldap-acl-milter: - image: "ldap-acl-milter/debian:19.02_devel" + depends_on: + - openldap + image: "ldap-acl-milter/debian:19.02_master" restart: unless-stopped environment: - LDAP_SERVER: ldap://ldap-slave.example.org:389 - LDAP_BINDDN: uid=lam,ou=apps,dc=example,dc=org - LDAP_BINDPW: TopSecret1! + #LDAP_SERVER: ldap://ldap-slave.example.local:389 + LDAP_SERVER: ldapi:///socket//slapd//slapd + LDAP_BINDDN: uid=lam,ou=applications,dc=example,dc=org + LDAP_BINDPW: TopSecret123!%& LDAP_BASE: ou=users,dc=example,dc=org - LDAP_QUERY: (&(mail=%rcpt%)(whitelistSender=%from%)) - # Socket default: /socket/ldap-acl-milter - # MILTER_SOCKET: inet6:8020 - MILTER_REJECT_MESSAGE: Rejected due to security policy violation + # 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%)) + # 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 hostname: ldap-acl-milter volumes: - "lam_socket:/socket/:rw" + - "openldap_socket:/socket/slapd:ro" + postfix: depends_on: - ldap-acl-milter - image: "postfix/alpine/amd64" + image: "your/favorite/postfix/image" restart: unless-stopped hostname: postfix ports: - "25:25" volumes: - "./config/postfix:/etc/postfix:rw" - - "lam_socket:/socket/:rw" + - "lam_socket:/socket/ldap-acl-milter/:rw" + - "openldap_socket:/socket/slapd:ro" ``` diff --git a/app/ldap-acl-milter.py b/app/ldap-acl-milter.py index f2f218a..b44afd3 100644 --- a/app/ldap-acl-milter.py +++ b/app/ldap-acl-milter.py @@ -1,11 +1,14 @@ import Milter -from ldap3 import Server,Connection,NONE,LDAPOperationResult +from ldap3 import ( + Server,ServerPool,Connection,NONE,LDAPOperationResult +) import sys import os import logging -from multiprocessing import Process,Queue +import string +import random +from timeit import default_timer as timer -log_queue = Queue(maxsize=32) g_milter_name = 'ldap-acl-milter' g_milter_socket = '/socket/' + g_milter_name g_milter_reject_message = 'Absender/Empfaenger passen nicht!' @@ -22,12 +25,18 @@ logging.basicConfig( ) class LdapAclMilter(Milter.Base): - def __init__(self): # A new instance with each new connection. + # 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 = [] + # https://stackoverflow.com/a/2257449 + self.mconn_id = ''.join( + random.choice(string.ascii_lowercase + string.digits) for _ in range(8) + ) - # Not registered callbacks + # Not registered/used callbacks @Milter.nocallback def connect(self, IPname, family, hostaddr): return self.CONTINUE @@ -46,7 +55,9 @@ class LdapAclMilter(Milter.Base): def envfrom(self, mailfrom, *str): if mailfrom == '<>': - self.setreply('550','5.7.1','Envelope null-sender not allowed!') + ex = str(self.mconn_id + '/FROM Envelope null-sender not allowed!') + logging.error(ex) + self.setreply('550','5.7.1',ex) Milter.REJECT mailfrom = mailfrom.replace("<","") mailfrom = mailfrom.replace(">","") @@ -54,54 +65,75 @@ class LdapAclMilter(Milter.Base): return Milter.CONTINUE def envrcpt(self, to, *str): + time_start = timer() to = to.replace("<","") to = to.replace(">","") + 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}) - self.setreply('550','5.7.1',g_milter_reject_message) + 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 except LDAPOperationResult as e: - self.log("LDAP Exception (envrcpt): " + str(e)) - self.setreply('451','4.7.1', str(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.' + ) return Milter.TEMPFAIL - self.R.append({"rcpt": to, "reason":'pass'}) + self.R.append({ + "rcpt": to, "reason":'pass',"time_start":time_start,"time_end":time_end + }) return Milter.CONTINUE def data(self): - # This callback is used only to log with queue-id - for rcpt in self.R: - self.log(self.getsymval('i') + - ": 5321.from=<" + self.F + "> 5321.rcpt=<" + - rcpt['rcpt'] + "> reason: " + rcpt['reason'] + # A queue-id will be generated after the first accepted RCPT TO + # and therefore not available until DATA command + self.queue_id = self.getsymval('i') + try: + for rcpt in self.R: + duration = rcpt['time_end'] - rcpt['time_start'] + logging.info(self.mconn_id + "/DATA " + self.queue_id + + ": 5321.from=<" + self.F + "> 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) + return Milter.TEMPFAIL return Milter.CONTINUE def eom(self): - # EOM will always be called - non-optional + # EOM is not optional and thus, always called by MTA + time_end = timer() + duration = time_end - self.time_start + logging.info(self.mconn_id + "/EOM " + self.queue_id + + " processing: " + str(duration) + " sec." + ) return Milter.CONTINUE def abort(self): - # client disconnected prematurely + # Client disconnected prematurely return Milter.CONTINUE def close(self): - # always called, even when abort is called. Clean up - # any external resources here. + # Always called, even when abort is called. + # Clean up any external resources here. return Milter.CONTINUE - def log(self,msg): - log_queue.put(msg) - -def logger_proc_loop(): - while True: - qmsg = log_queue.get() - if not qmsg: break - logging.info(qmsg) - if __name__ == "__main__": try: if 'LDAP_SERVER' not in os.environ: @@ -124,7 +156,12 @@ if __name__ == "__main__": 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) 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, @@ -135,18 +172,14 @@ if __name__ == "__main__": logging.error("LDAP Exception: " + str(e)) sys.exit(1) try: - logger_proc = Process(target=logger_proc_loop) - logger_proc.start() timeout = 600 # Register to have the Milter factory create instances of your class: Milter.factory = LdapAclMilter # Tell the MTA which features we use flags = Milter.ADDHDRS Milter.set_flags(flags) - logging.info("Startup " + g_milter_name + "@"+ g_milter_socket) + logging.info("Startup " + g_milter_name + "@socket: " + g_milter_socket) Milter.runmilter(g_milter_name,g_milter_socket,timeout,True) - log_queue.put(None) - logger_proc.join() logging.info("Shutdown " + g_milter_name) except: logging.error("MAIN-EXCEPTION: " + str(sys.exc_info()))