From a848231ae0f346dc7cc000973fbeb65b0894ee92 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 10 Apr 2024 21:59:03 +0200 Subject: Adding upstream version 3.8.5. Signed-off-by: Daniel Baumann --- html/LDAP_README.html | 633 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 633 insertions(+) create mode 100644 html/LDAP_README.html (limited to 'html/LDAP_README.html') diff --git a/html/LDAP_README.html b/html/LDAP_README.html new file mode 100644 index 0000000..ce77f94 --- /dev/null +++ b/html/LDAP_README.html @@ -0,0 +1,633 @@ + + + + + + +Postfix LDAP Howto + + + + + + + + +

Postfix LDAP Howto

+ +
+ +

LDAP Support in Postfix

+ +

Postfix can use an LDAP directory as a source for any of its +lookups: aliases(5), virtual(5), canonical(5), etc. This allows +you to keep information for your mail service in a replicated +network database with fine-grained access controls. By not storing +it locally on the mail server, the administrators can maintain it +from anywhere, and the users can control whatever bits of it you +think appropriate. You can have multiple mail servers using the +same information, without the hassle and delay of having to copy +it to each.

+ +

Topics covered in this document:

+ + + +

Building Postfix with LDAP support

+ +

These instructions assume that you build Postfix from source +code as described in the INSTALL document. Some modification may +be required if you build Postfix from a vendor-specific source +package.

+ +

Note 1: Postfix no longer supports the LDAP version 1 interface. +

+ +

Note 2: to use LDAP with Debian GNU/Linux's Postfix, all you +need is to install the postfix-ldap package and you're done. There +is no need to recompile Postfix.

+ +

You need to have LDAP libraries and include files installed +somewhere on your system, and you need to configure the Postfix +Makefiles accordingly.

+ +

For example, to build the OpenLDAP libraries for use with +Postfix (i.e. LDAP client code only), you could use the following +command:

+ +
+
+% ./configure  --without-kerberos --without-cyrus-sasl --without-tls \
+    --without-threads --disable-slapd --disable-slurpd \
+    --disable-debug --disable-shared
+
+
+ +

If you're using the libraries from the UM distribution +(http://www.umich.edu/~dirsvcs/ldap/ldap.html) or OpenLDAP +(http://www.openldap.org), something like this in the top level of +your Postfix source tree should work:

+ +
+
+% make tidy
+% make makefiles CCARGS="-I/usr/local/include -DHAS_LDAP" \
+    AUXLIBS_LDAP="-L/usr/local/lib -lldap -L/usr/local/lib -llber"
+
+
+ +

If your LDAP shared library is in a directory that the RUN-TIME +linker does not know about, add a "-Wl,-R,/path/to/directory" option after +"-lldap".

+ +

Postfix versions before 3.0 use AUXLIBS instead of AUXLIBS_LDAP. +With Postfix 3.0 and later, the old AUXLIBS variable still supports +building a statically-loaded LDAP database client, but only the new +AUXLIBS_LDAP variable supports building a dynamically-loaded or +statically-loaded LDAP database client.

+ +
+ +

Failure to use the AUXLIBS_LDAP variable will defeat the purpose +of dynamic database client loading. Every Postfix executable file +will have LDAP database library dependencies. And that was exactly +what dynamic database client loading was meant to avoid.

+ +
+ +

On Solaris 2.x you may have to specify run-time link information, +otherwise ld.so will not find some of the shared libraries:

+ +
+
+% make tidy
+% make makefiles CCARGS="-I/usr/local/include -DHAS_LDAP" \
+    AUXLIBS_LDAP="-L/usr/local/lib -R/usr/local/lib -lldap \
+            -L/usr/local/lib -R/usr/local/lib -llber"
+
+
+ +

The 'make tidy' command is needed only if you have previously +built Postfix without LDAP support.

+ +

Instead of '/usr/local' specify the actual locations of your +LDAP include files and libraries. Be sure to not mix LDAP include +files and LDAP libraries of different versions!!

+ +

If your LDAP libraries were built with Kerberos support, you'll +also need to include your Kerberos libraries in this line. Note +that the KTH Kerberos IV libraries might conflict with Postfix's +lib/libdns.a, which defines dns_lookup. If that happens, you'll +probably want to link with LDAP libraries that lack Kerberos support +just to build Postfix, as it doesn't support Kerberos binds to the +LDAP server anyway. Sorry about the bother.

+ +

If you're using one of the Netscape LDAP SDKs, you'll need to +change the AUXLIBS line to point to libldap10.so or libldapssl30.so +or whatever you have, and you may need to use the appropriate linker +option (e.g. '-R') so the executables can find it at runtime.

+ +

If you are using OpenLDAP, and the libraries were built with SASL +support, you can add -DUSE_LDAP_SASL to the CCARGS to enable SASL support. +For example:

+ +
+
+     CCARGS="-I/usr/local/include -DHAS_LDAP -DUSE_LDAP_SASL"
+
+
+ +

Configuring LDAP lookups

+ +

In order to use LDAP lookups, define an LDAP source +as a table lookup in main.cf, for example:

+ +
+
+alias_maps = hash:/etc/aliases, ldap:/etc/postfix/ldap-aliases.cf
+
+
+ +

The file /etc/postfix/ldap-aliases.cf can specify a great number +of parameters, including parameters that enable LDAP SSL or STARTTLS, +and LDAP SASL. For a complete description, see the ldap_table(5) +manual page.

+ +

Example: local(8) aliases

+ +

Here's a basic example for using LDAP to look up local(8) +aliases. Assume that in main.cf, you have:

+ +
+
+alias_maps = hash:/etc/aliases, ldap:/etc/postfix/ldap-aliases.cf
+
+
+ +

and in ldap:/etc/postfix/ldap-aliases.cf you have:

+ +
+
+server_host = ldap.example.com
+search_base = dc=example, dc=com
+
+
+ +

Upon receiving mail for a local address "ldapuser" that isn't +found in the /etc/aliases database, Postfix will search the LDAP +server listening at port 389 on ldap.example.com. It will bind anonymously, +search for any directory entries whose mailacceptinggeneralid +attribute is "ldapuser", read the "maildrop" attributes of those +found, and build a list of their maildrops, which will be treated +as RFC822 addresses to which the message will be delivered.

+ +

Example: virtual domains/addresses

+ +

If you want to keep information for virtual lookups in your +directory, it's only a little more complicated. First, you need to +make sure Postfix knows about the virtual domain. An easy way to +do that is to add the domain to the mailacceptinggeneralid attribute +of some entry in the directory. Next, you'll want to make sure all +of your virtual recipient's mailacceptinggeneralid attributes are +fully qualified with their virtual domains. Finally, if you want +to designate a directory entry as the default user for a virtual +domain, just give it an additional mailacceptinggeneralid (or the +equivalent in your directory) of "@fake.dom". That's right, no +user part. If you don't want a catchall user, omit this step and +mail to unknown users in the domain will simply bounce.

+ +

In summary, you might have a catchall user for a virtual domain +that looks like this:

+ +
+
+     dn: cn=defaultrecipient, dc=fake, dc=dom
+     objectclass: top
+     objectclass: virtualaccount
+     cn: defaultrecipient
+     owner: uid=root, dc=someserver, dc=isp, dc=dom
+1 -> mailacceptinggeneralid: fake.dom
+2 -> mailacceptinggeneralid: @fake.dom
+3 -> maildrop: realuser@real.dom         
+
+
+ +
+ +

1: Postfix knows fake.dom is a valid virtual domain when +it looks for this and gets something (the maildrop) back.

+ +

2: This causes any mail for unknown users in fake.dom to +go to this entry ...

+ +

3: ... and then to its maildrop.

+ +
+ +

Normal users might simply have one mailacceptinggeneralid and +maildrop, e.g. "normaluser@fake.dom" and "normaluser@real.dom". +

+ +

Example: expanding LDAP groups

+ +

+LDAP is frequently used to store group member information. There are a +number of ways of handling LDAP groups. We will show a few examples in +order of increasing complexity, but owing to the number of independent +variables, we can only present a tiny portion of the solution space. +We show how to: +

+ +
    + +

  1. query groups as lists of addresses;

    + +

  2. query groups as lists of user objects containing addresses;

    + +

  3. forward special lists unexpanded to a separate list server, +for moderation or other processing;

    + +

  4. handle complex schemas by controlling expansion and by treating +leaf nodes specially, using features that are new in Postfix 2.4.

    + +
+ +

+The example LDAP entries and implied schema below show two group entries +("agroup" and "bgroup") and four user entries ("auser", "buser", "cuser" +and "duser"). The group "agroup" has the users "auser" (1) and "buser" (2) +as members via DN references in the multi-valued attribute "memberdn", and +direct email addresses of two external users "auser@example.org" (3) and +"buser@example.org" (4) stored in the multi-valued attribute "memberaddr". +The same is true of "bgroup" and "cuser"/"duser" (6)/(7)/(8)/(9), but +"bgroup" also has a "maildrop" attribute of "bgroup@mlm.example.com" +(5):

+ +
+
+     dn: cn=agroup, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapgroup
+     cn: agroup
+     mail: agroup@example.com
+1 -> memberdn: uid=auser, dc=example, dc=com
+2 -> memberdn: uid=buser, dc=example, dc=com
+3 -> memberaddr: auser@example.org
+4 -> memberaddr: buser@example.org
+
+
+ +
+     dn: cn=bgroup, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapgroup
+     cn: bgroup
+     mail: bgroup@example.com
+5 -> maildrop: bgroup@mlm.example.com
+6 -> memberdn: uid=cuser, dc=example, dc=com
+7 -> memberdn: uid=duser, dc=example, dc=com
+8 -> memberaddr: cuser@example.org
+9 -> memberaddr: duser@example.org
+
+
+ +
+     dn: uid=auser, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapuser
+     uid: auser
+10 -> mail: auser@example.com
+11 -> maildrop: auser@mailhub.example.com
+
+
+ +
+     dn: uid=buser, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapuser
+     uid: buser
+12 -> mail: buser@example.com
+13 -> maildrop: buser@mailhub.example.com
+
+
+ +
+     dn: uid=cuser, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapuser
+     uid: cuser
+14 -> mail: cuser@example.com
+
+
+ +
+     dn: uid=duser, dc=example, dc=com
+     objectclass: top
+     objectclass: ldapuser
+     uid: duser
+15 -> mail: duser@example.com
+
+
+ +
+ +

Our first use case ignores the "memberdn" attributes, and assumes +that groups hold only direct "memberaddr" strings as in (3), (4), (8) and +(9). The goal is to map the group address to the list of constituent +"memberaddr" values. This is simple, ignoring the various connection +related settings (hosts, ports, bind settings, timeouts, ...) we have: +

+ +
+
+    simple.cf:
+        ...
+        search_base = dc=example, dc=com
+        query_filter = mail=%s
+        result_attribute = memberaddr
+    $ postmap -q agroup@example.com ldap:/etc/postfix/simple.cf \
+        auser@example.org,buser@example.org
+
+
+ +

We search "dc=example, dc=com". The "mail" attribute is used in the +query_filter to locate the right group, the "result_attribute" setting +described in ldap_table(5) is used to specify that "memberaddr" values +from the matching group are to be returned as a comma separated list. +Always check tables using postmap(1) with the "-q" option, before +deploying them into production use in main.cf.

+ +

Our second use case instead expands "memberdn" attributes (1), (2), +(6) and (7), follows the DN references and returns the "maildrop" of the +referenced user entries. Here we use the "special_result_attribute" +setting from ldap_table(5) to designate the "memberdn" attribute +as holding DNs of the desired member entries. The "result_attribute" +setting selects which attributes are returned from the selected DNs. It +is important to choose a result attribute that is not also present in +the group object, because result attributes are collected from both +the group and the member DNs. In this case we choose "maildrop" and +assume for the moment that groups never have a "maildrop" (the "bgroup" +"maildrop" attribute is for a different use case). The returned data for +"auser" and "buser" is from items (11) and (13) in the example data.

+ +
+
+    special.cf:
+        ...
+        search_base = dc=example, dc=com
+        query_filter = mail=%s
+        result_attribute = maildrop
+        special_result_attribute = memberdn
+    $ postmap -q agroup@example.com ldap:/etc/postfix/special.cf \
+        auser@mailhub.example.com,buser@mailhub.example.com
+
+
+ +

Note: if the desired member object result attribute is always also +present in the group, you get surprising results: the expansion also +returns the address of the group. This is a known limitation of Postfix +releases prior to 2.4, and is addressed in the new with Postfix 2.4 +"leaf_result_attribute" feature described in ldap_table(5).

+ +

Our third use case has some groups that are expanded immediately, +and other groups that are forwarded to a dedicated mailing list manager +host for delayed expansion. This uses two LDAP tables, one for users +and forwarded groups and a second for groups that can be expanded +immediately. It is assumed that groups that require forwarding are +never nested members of groups that are directly expanded.

+ +
+
+    no_expand.cf:
+        ...
+        search_base = dc=example, dc=com
+        query_filter = mail=%s
+        result_attribute = maildrop
+    expand.cf
+        ...
+        search_base = dc=example, dc=com
+        query_filter = mail=%s
+        result_attribute = maildrop
+        special_result_attribute = memberdn
+    $ postmap -q auser@example.com \
+        ldap:/etc/postfix/no_expand.cf ldap:/etc/postfix/expand.cf \
+        auser@mailhub.example.com
+    $ postmap -q agroup@example.com \
+        ldap:/etc/postfix/no_expand.cf ldap:/etc/postfix/expand.cf \
+        auser@mailhub.example.com,buser@mailhub.example.com
+    $ postmap -q bgroup@example.com \
+        ldap:/etc/postfix/no_expand.cf ldap:/etc/postfix/expand.cf \
+        bgroup@mlm.example.com
+
+
+ +

Non-group objects and groups with delayed expansion (those that have a +maildrop attribute) are rewritten to a single maildrop value. Groups that +don't have a maildrop are expanded as the second use case. This admits +a more elegant solution with Postfix 2.4 and later.

+ +

Our final use case is the same as the third, but this time uses new +features in Postfix 2.4. We now are able to use just one LDAP table and +no longer need to assume that forwarded groups are never nested inside +expanded groups.

+ +
+
+    fancy.cf:
+        ...
+        search_base = dc=example, dc=com
+        query_filter = mail=%s
+        result_attribute = memberaddr
+        special_result_attribute = memberdn
+        terminal_result_attribute = maildrop
+        leaf_result_attribute = mail
+    $ postmap -q auser@example.com ldap:/etc/postfix/fancy.cf \
+        auser@mailhub.example.com
+    $ postmap -q cuser@example.com ldap:/etc/postfix/fancy.cf \
+        cuser@example.com
+    $ postmap -q agroup@example.com ldap:/etc/postfix/fancy.cf \
+        auser@mailhub.example.com,buser@mailhub.example.com,auser@example.org,buser@example.org
+    $ postmap -q bgroup@example.com ldap:/etc/postfix/fancy.cf \
+        bgroup@mlm.example.com
+
+
+ +

Above, delayed expansion is enabled via "terminal_result_attribute", +which, if present, is used as the sole result and all other expansion is +suppressed. Otherwise, the "leaf_result_attribute" is only returned for +leaf objects that don't have a "special_result_attribute" (non-groups), +while the "result_attribute" (direct member address of groups) is returned +at every level of recursive expansion, not just the leaf nodes. This fancy +example illustrates all the features of Postfix 2.4 group expansion.

+ +

Other uses of LDAP lookups

+ +Other common uses for LDAP lookups include rewriting senders and +recipients with Postfix's canonical lookups, for example in order +to make mail leaving your site appear to be coming from +"First.Last@example.com" instead of "userid@example.com". + +

Notes and things to think about

+ + + +

Feedback

+ +

If you have questions, send them to postfix-users@postfix.org. Please +include relevant information about your Postfix setup: LDAP-related +output from postconf, which LDAP libraries you built with, and which +directory server you're using. If your question involves your directory +contents, please include the applicable bits of some directory entries.

+ +

Credits

+ + + +And of course Wietse. + + + + -- cgit v1.2.3