LDAP Authentication
+ +Introduction
+Getting started with ldap and docker-mailserver
we need to take 3 parts in account:
-
+
postfix
for incoming & outgoing email
+dovecot
for accessing mailboxes
+saslauthd
for SMTP authentication (this can also be delegated to dovecot)
+
Variables to Control Provisioning by the Container
+Have a look at the ENV page for information on the default values.
+LDAP_QUERY_FILTER_*
+Those variables contain the LDAP lookup filters for postfix, using %s
as the placeholder for the domain or email address in question. This means that...
-
+
- ...for incoming email, the domain must return an entry for the
DOMAIN
filter (seevirtual_alias_domains
).
+ - ...for incoming email, the inboxes which receive the email are chosen by the
USER
,ALIAS
andGROUP
filters.-
+
- The
USER
filter specifies personal mailboxes, for which only one should exist per address, for example(mail=%s)
(also seevirtual_mailbox_maps
)
+ - The
ALIAS
filter specifies aliases for mailboxes, usingvirtual_alias_maps
, for example(mailAlias=%s)
+ - The
GROUP
filter specifies the personal mailboxes in a group (for emails that multiple people shall receive), usingvirtual_alias_maps
, for example(mailGroupMember=%s)
.
+ - Technically, there is no difference between
ALIAS
andGROUP
, but ideally you should useALIAS
for personal aliases for a singular person (likeceo@example.org
) andGROUP
for multiple people (likehr@example.org
).
+
+ - The
- ...for outgoing email, the sender address is put through the
SENDERS
filter, and only if the authenticated user is one of the returned entries, the email can be sent.-
+
- This only applies if
SPOOF_PROTECTION=1
.
+ - If the
SENDERS
filter is missing, theUSER
,ALIAS
andGROUP
filters will be used in in a disjunction (OR).
+ - To for example allow users from the
admin
group to spoof any sender email address, and to force everyone else to only use their personal mailbox address for outgoing email, you can use something like this:(|(memberOf=cn=admin,*)(mail=%s))
+
+ - This only applies if
Example
+A really simple LDAP_QUERY_FILTER
configuration, using only the user filter and allowing only admin@*
to spoof any sender addresses.
- ENABLE_LDAP=1 # with the :edge tag, use ACCOUNT_PROVISIONER
+- LDAP_START_TLS=yes
+- ACCOUNT_PROVISIONER=LDAP
+- LDAP_SERVER_HOST=ldap.example.org
+- LDAP_SEARCH_BASE=dc=example,dc=org"
+- LDAP_BIND_DN=cn=admin,dc=example,dc=org
+- LDAP_BIND_PW=mypassword
+- SPOOF_PROTECTION=1
+
+- LDAP_QUERY_FILTER_DOMAIN=(mail=*@%s)
+- LDAP_QUERY_FILTER_USER=(mail=%s)
+- LDAP_QUERY_FILTER_ALIAS=(|) # doesn't match anything
+- LDAP_QUERY_FILTER_GROUP=(|) # doesn't match anything
+- LDAP_QUERY_FILTER_SENDERS=(|(mail=%s)(mail=admin@*))
+
DOVECOT_*_FILTER
& DOVECOT_*_ATTRS
+These variables specify the LDAP filters that dovecot uses to determine if a user can log in to their IMAP account, and which mailbox is responsible to receive email for a specific postfix user.
+This is split into the following two lookups, both using %u
as the placeholder for the full login name (see dovecot documentation for a full list of placeholders). Usually you only need to set DOVECOT_USER_FILTER
, in which case it will be used for both filters.
-
+
DOVECOT_USER_FILTER
is used to get the account details (uid, gid, home directory, quota, ...) of a user.
+DOVECOT_PASS_FILTER
is used to get the password information of the user, and is in pretty much all cases identical toDOVECOT_USER_FILTER
(which is the default behaviour if left away).
+
If your directory doesn't have the postfix-book schema installed, then you must change the internal attribute handling for dovecot. For this you have to change the pass_attr
and the user_attr
mapping, as shown in the example below:
- DOVECOT_PASS_ATTRS=<YOUR_USER_IDENTIFIER_ATTRIBUTE>=user,<YOUR_USER_PASSWORD_ATTRIBUTE>=password
+- DOVECOT_USER_ATTRS=<YOUR_USER_HOME_DIRECTORY_ATTRIBUTE>=home,<YOUR_USER_MAILSTORE_ATTRIBUTE>=mail,<YOUR_USER_MAIL_UID_ATTRIBUTE>=uid,<YOUR_USER_MAIL_GID_ATTRIBUTE>=gid
+
Note
+For DOVECOT_*_ATTRS
, you can replace ldapAttr=dovecotAttr
with =dovecotAttr=%{ldap:ldapAttr}
for more flexibility, like for example =home=/var/mail/%{ldap:uid}
or just =uid=5000
.
A list of dovecot attributes can be found in the dovecot documentation.
+Defaults
+- DOVECOT_USER_ATTRS=mailHomeDirectory=home,mailUidNumber=uid,mailGidNumber=gid,mailStorageDirectory=mail
+- DOVECOT_PASS_ATTRS=uniqueIdentifier=user,userPassword=password
+- DOVECOT_USER_FILTER=(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))
+
Example
+Setup for a directory that has the qmail-schema installed and uses uid
:
- DOVECOT_PASS_ATTRS=uid=user,userPassword=password
+- DOVECOT_USER_ATTRS=homeDirectory=home,qmailUID=uid,qmailGID=gid,mailMessageStore=mail
+- DOVECOT_USER_FILTER=(&(objectClass=qmailUser)(uid=%u)(accountStatus=active))
+
The LDAP server configuration for dovecot will be taken mostly from postfix, other options can be found in the environment section in the docs.
+DOVECOT_AUTH_BIND
+Set this to yes
to enable authentication binds (more details in the dovecot documentation). Currently, only DN lookup is supported without further changes to the configuration files, so this is only useful when you want to bind as a readonly user without the permission to read passwords.
SASLAUTHD_LDAP_FILTER
+This filter is used for saslauthd
, which is called by postfix when someone is authenticating through SMTP (assuming that SASLAUTHD_MECHANISMS=ldap
is being used). Note that you'll need to set up the LDAP server for saslauthd separately from postfix.
The filter variables are explained in detail in the LDAP_SASLAUTHD
file, but unfortunately, this method doesn't really support domains right now - that means that %U
is the only token that makes sense in this variable.
When to use this and how to avoid it
+Using a separate filter for SMTP authentication allows you to for example allow noreply@example.org
to send email, but not log in to IMAP or receive email: (&(mail=%U@example.org)(|(memberOf=cn=email,*)(mail=noreply@example.org)))
If you don't want to use a separate filter for SMTP authentication, you can set SASLAUTHD_MECHANISMS=rimap
and SASLAUTHD_MECH_OPTIONS=127.0.0.1
to authenticate against dovecot instead - this means that the DOVECOT_USER_FILTER
and DOVECOT_PASS_FILTER
will be used for SMTP authentication as well.
Configure LDAP with saslauthd
+- ENABLE_SASLAUTHD=1
+- SASLAUTHD_MECHANISMS=ldap
+- SASLAUTHD_LDAP_FILTER=(mail=%U@example.org)
+
Secure Connection with LDAPS or StartTLS
+To enable LDAPS, all you need to do is to add the protocol to LDAP_SERVER_HOST
, for example ldaps://example.org:636
.
To enable LDAP over StartTLS (on port 389), you need to set the following environment variables instead (the protocol must not be ldaps://
in this case!):
- LDAP_START_TLS=yes
+- DOVECOT_TLS=yes
+- SASLAUTHD_LDAP_START_TLS=yes
+
Active Directory Configurations (Tested with Samba4 AD Implementation)
+In addition to LDAP explanation above, when Docker Mailserver is intended to be used with Active Directory (or the equivelant implementations like Samba4 AD DC) the following points should be taken into consideration:
+-
+
- Samba4 Active Directory requires a secure connection to the domain controller (DC), either via SSL/TLS (LDAPS) or via StartTLS. +
- The username equivalent in Active Directory is:
sAMAccountName
.
+ proxyAddresses
can be used to store email aliases of single users. The convention is to prefix the email aliases withsmtp:
(e.g:smtp:some.name@example.com
).
+- Active Directory is used typically not only as LDAP Directory storage, but also as a domain controller, i.e., it will do many things including authenticating users. Mixing Linux and Windows clients requires the usage of RFC2307 attributes, namely
uidNumber
,gidNumber
instead of the typicaluid
. Assigning different owner to email folders can also be done in this approach, nevertheless there is a bug at the moment in Docker Mailserver that overwrites all permissions when starting the container. Either a manual fix is necessary now, or a temporary workaround to use a hard-codedldap:uidNumber
that equals to5000
until this issue is fixed.
+ - To deliver the emails to different members of Active Directory Security Group or Distribution Group (similar to mailing lists), use a
user-patches.sh
script to modifyldap-groups.cf
so that it includesleaf_result_attribute = mail
andspecial_result_attribute = member
. This can be achieved simply by:
+
The configuration shown to get the Group to work is from here and here.
+# user-patches.sh
+
+...
+grep -q '^leaf_result_attribute = mail$' /etc/postfix/ldap-groups.cf || echo "leaf_result_attribute = mail" >> /etc/postfix/ldap-groups.cf
+grep -q '^special_result_attribute = member$' /etc/postfix/ldap-groups.cf || echo "special_result_attribute = member" >> /etc/postfix/ldap-groups.cf
+...
+
-
+
- In
/etc/ldap/ldap.conf
, if theTLS_REQCERT
isdemand
/hard
(default), the CA certificate used to verify the LDAP server certificate must be recognized as a trusted CA. This can be done by volume mounting theca.crt
file and updating the trust store via auser-patches.sh
script:
+
# user-patches.sh
+
+...
+cp /MOUNTED_FOLDER/ca.crt /usr/local/share/ca-certificates/
+update-ca-certificates
+...
+
The changes on the configurations necessary to work with Active Directory (only changes are listed, the rest of the LDAP configuration can be taken from the other examples shown in this documentation):
+# If StartTLS is the chosen method to establish a secure connection with Active Directory.
+- LDAP_START_TLS=yes
+- SASLAUTHD_LDAP_START_TLS=yes
+- DOVECOT_TLS=yes
+
+- LDAP_QUERY_FILTER_USER=(&(objectclass=person)(mail=%s))
+- LDAP_QUERY_FILTER_ALIAS=(&(objectclass=person)(proxyAddresses=smtp:%s))
+# Filters Active Directory groups (mail lists). Additional changes on ldap-groups.cf are also required as shown above.
+- LDAP_QUERY_FILTER_GROUP=(&(objectClass=group)(mail=%s))
+- LDAP_QUERY_FILTER_DOMAIN=(mail=*@%s)
+# Allows only Domain admins to send any sender email address, otherwise the sender address must match the LDAP attribute `mail`.
+- SPOOF_PROTECTION=1
+- LDAP_QUERY_FILTER_SENDERS=(|(mail=%s)(proxyAddresses=smtp:%s)(memberOf=cn=Domain Admins,cn=Users,dc=*))
+
+- DOVECOT_USER_FILTER=(&(objectclass=person)(sAMAccountName=%n))
+# At the moment to be able to use %{ldap:uidNumber}, a manual bug fix as described above must be used. Otherwise %{ldap:uidNumber} %{ldap:uidNumber} must be replaced by the hard-coded value 5000.
+- DOVECOT_USER_ATTRS==uid=%{ldap:uidNumber},=gid=5000,=home=/var/mail/%Ln,=mail=maildir:~/Maildir
+- DOVECOT_PASS_ATTRS=sAMAccountName=user,userPassword=password
+- SASLAUTHD_LDAP_FILTER=(&(sAMAccountName=%U)(objectClass=person))
+
LDAP Setup Examples
+Basic Setup
+version: '3.8'
+services:
+ mailserver:
+ image: docker.io/mailserver/docker-mailserver:latest
+ container_name: mailserver
+ hostname: mail
+ domainname: example.com
+
+ ports:
+ - "25:25"
+ - "143:143"
+ - "587:587"
+ - "993:993"
+
+ volumes:
+ - ./docker-data/dms/mail-data/:/var/mail/
+ - ./docker-data/dms/mail-state/:/var/mail-state/
+ - ./docker-data/dms/mail-logs/:/var/log/mail/
+ - ./docker-data/dms/config/:/tmp/docker-mailserver/
+ - /etc/localtime:/etc/localtime:ro
+
+ environment:
+ - ENABLE_SPAMASSASSIN=1
+ - ENABLE_CLAMAV=1
+ - ENABLE_FAIL2BAN=1
+ - ENABLE_POSTGREY=1
+
+ # >>> Postfix LDAP Integration
+ - ENABLE_LDAP=1 # with the :edge tag, use ACCOUNT_PROVISIONER
+ - ACCOUNT_PROVISIONER=LDAP
+ - LDAP_SERVER_HOST=ldap.example.org
+ - LDAP_BIND_DN=cn=admin,ou=users,dc=example,dc=org
+ - LDAP_BIND_PW=mypassword
+ - LDAP_SEARCH_BASE=dc=example,dc=org
+ - LDAP_QUERY_FILTER_DOMAIN=(|(mail=*@%s)(mailAlias=*@%s)(mailGroupMember=*@%s))
+ - LDAP_QUERY_FILTER_USER=(&(objectClass=inetOrgPerson)(mail=%s))
+ - LDAP_QUERY_FILTER_ALIAS=(&(objectClass=inetOrgPerson)(mailAlias=%s))
+ - LDAP_QUERY_FILTER_GROUP=(&(objectClass=inetOrgPerson)(mailGroupMember=%s))
+ - LDAP_QUERY_FILTER_SENDERS=(&(objectClass=inetOrgPerson)(|(mail=%s)(mailAlias=%s)(mailGroupMember=%s)))
+ - SPOOF_PROTECTION=1
+ # <<< Postfix LDAP Integration
+
+ # >>> Dovecot LDAP Integration
+ - DOVECOT_USER_FILTER=(&(objectClass=inetOrgPerson)(mail=%u))
+ - DOVECOT_PASS_ATTRS=uid=user,userPassword=password
+ - DOVECOT_USER_ATTRS==home=/var/mail/%{ldap:uid},=mail=maildir:~/Maildir,uidNumber=uid,gidNumber=gid
+ # <<< Dovecot LDAP Integration
+
+ # >>> SASL LDAP Authentication
+ - ENABLE_SASLAUTHD=1
+ - SASLAUTHD_MECHANISMS=ldap
+ - SASLAUTHD_LDAP_FILTER=(&(mail=%U@example.org)(objectClass=inetOrgPerson))
+ # <<< SASL LDAP Authentication
+
+ - ONE_DIR=1
+ - SSL_TYPE=letsencrypt
+ - PERMIT_DOCKER=host
+
+ cap_add:
+ - NET_ADMIN
+
Kopano / Zarafa
+version: '3.8'
+
+services:
+ mailserver:
+ image: docker.io/mailserver/docker-mailserver:latest
+ container_name: mailserver
+ hostname: mail
+ domainname: example.com
+
+ ports:
+ - "25:25"
+ - "143:143"
+ - "587:587"
+ - "993:993"
+
+ volumes:
+ - ./docker-data/dms/mail-data/:/var/mail/
+ - ./docker-data/dms/mail-state/:/var/mail-state/
+ - ./docker-data/dms/config/:/tmp/docker-mailserver/
+
+ environment:
+ # We are not using dovecot here
+ - SMTP_ONLY=1
+ - ENABLE_SPAMASSASSIN=1
+ - ENABLE_CLAMAV=1
+ - ENABLE_FAIL2BAN=1
+ - ENABLE_POSTGREY=1
+ - SASLAUTHD_PASSWD=
+
+ # >>> SASL Authentication
+ - ENABLE_SASLAUTHD=1
+ - SASLAUTHD_LDAP_FILTER=(&(sAMAccountName=%U)(objectClass=person))
+ - SASLAUTHD_MECHANISMS=ldap
+ # <<< SASL Authentication
+
+ # >>> Postfix Ldap Integration
+ - ENABLE_LDAP=1 # with the :edge tag, use ACCOUNT_PROVISIONER
+ - ACCOUNT_PROVISIONER=LDAP
+ - LDAP_SERVER_HOST=<yourLdapContainer/yourLdapServer>
+ - LDAP_SEARCH_BASE=dc=mydomain,dc=loc
+ - LDAP_BIND_DN=cn=Administrator,cn=Users,dc=mydomain,dc=loc
+ - LDAP_BIND_PW=mypassword
+ - LDAP_QUERY_FILTER_USER=(&(objectClass=user)(mail=%s))
+ - LDAP_QUERY_FILTER_GROUP=(&(objectclass=group)(mail=%s))
+ - LDAP_QUERY_FILTER_ALIAS=(&(objectClass=user)(otherMailbox=%s))
+ - LDAP_QUERY_FILTER_DOMAIN=(&(|(mail=*@%s)(mailalias=*@%s)(mailGroupMember=*@%s))(mailEnabled=TRUE))
+ # <<< Postfix Ldap Integration
+
+ # >>> Kopano Integration
+ - ENABLE_POSTFIX_VIRTUAL_TRANSPORT=1
+ - POSTFIX_DAGENT=lmtp:kopano:2003
+ # <<< Kopano Integration
+
+ - ONE_DIR=1
+ - SSL_TYPE=letsencrypt
+ - PERMIT_DOCKER=host
+
+ cap_add:
+ - NET_ADMIN
+