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https://github.com/chillout2k/ldap-acl-milter.git
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69 lines
4.1 KiB
Markdown
69 lines
4.1 KiB
Markdown
# ldap-acl-milter
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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).
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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.
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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.
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### Deployment paradigm
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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 realy 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.
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### docker-compose.yml
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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.
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```
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version: '3'
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volumes:
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lam_socket:
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openldap_spool:
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openldap_socket:
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services:
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openldap:
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image: "your/favorite/openldap/image"
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restart: unless-stopped
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hostname: openldap
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volumes:
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- "./config/openldap:/etc/openldap:rw"
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- "openldap_spool:/var/openldap-data:rw"
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- "openldap_socket:/socket:rw"
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ldap-acl-milter:
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depends_on:
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- openldap
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image: "ldap-acl-milter/debian:19.02_master"
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restart: unless-stopped
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environment:
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#LDAP_SERVER: ldap://ldap-slave.example.local:389
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LDAP_SERVER: ldapi:///socket//slapd//slapd
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LDAP_BINDDN: uid=lam,ou=applications,dc=example,dc=org
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LDAP_BINDPW: TopSecret123!%&
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LDAP_BASE: ou=users,dc=example,dc=org
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# This example LDAP query is for inbound filtering
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# where the 'mail' attribute equals to the recipient
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# and the 'amavisWhitelistSender' attribute the eligible sender
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LDAP_QUERY: (&(mail=%rcpt%)(amavisWhitelistSender=%from%))
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# Default: UNIX-socket located under /socket/ldap-acl-milter
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# https://pythonhosted.org/pymilter/namespacemilter.html#a266a6e09897499d8b1ae0e20f0d2be73
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#MILTER_SOCKET: inet6:8020
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MILTER_REJECT_MESSAGE: Message rejected due to security policy
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hostname: ldap-acl-milter
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volumes:
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- "lam_socket:/socket/:rw"
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- "openldap_socket:/socket/slapd:ro"
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postfix:
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depends_on:
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- ldap-acl-milter
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image: "your/favorite/postfix/image"
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restart: unless-stopped
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hostname: postfix
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ports:
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- "25:25"
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volumes:
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- "./config/postfix:/etc/postfix:rw"
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- "lam_socket:/socket/ldap-acl-milter/:rw"
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- "openldap_socket:/socket/slapd:ro"
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```
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