NAME
ldap_table - Postfix LDAP client configuration
SYNOPSIS
postmap -q "string" ldap:/etc/postfix/filename
postmap -q - ldap:/etc/postfix/filename <inputfile
DESCRIPTION
The Postfix mail system uses optional tables for address rewriting or
mail routing. These tables are usually in dbm or db format.
Alternatively, lookup tables can be specified as LDAP databases.
In order to use LDAP lookups, define an LDAP source as a lookup table
in main.cf, for example:
alias_maps = ldap:/etc/postfix/ldap-aliases.cf
The file /etc/postfix/ldap-aliases.cf has the same format as the
Postfix main.cf file, and can specify the parameters described below.
An example is given at the end of this manual.
This configuration method is available with Postfix version 2.1 and
later. See the section "BACKWARDS COMPATIBILITY" below for older
Postfix versions.
For details about LDAP SSL and STARTTLS, see the section on SSL and
STARTTLS below.
BACKWARDS COMPATIBILITY
For backwards compatibility with Postfix version 2.0 and earlier, LDAP
parameters can also be defined in main.cf. Specify as LDAP source a
name that doesn’t begin with a slash or a dot. The LDAP parameters
will then be accessible as the name you’ve given the source in its
definition, an underscore, and the name of the parameter. For example,
if the map is specified as "ldap:ldapsource", the "server_host"
parameter below would be defined in main.cf as
"ldapsource_server_host".
Note: with this form, the passwords for the LDAP sources are written in
main.cf, which is normally world-readable. Support for this form will
be removed in a future Postfix version.
Postfix 2.2 has enhanced query interfaces for MySQL and PostgreSQL.
These include features that were previously available only in the
Postfix LDAP client. This work also created an opportunity for
improvements in the LDAP interface. The primary compatibility issue is
that result_filter (a name that has caused some confusion as to its
meaning in the past) has been renamed to result_format. For backwards
compatibility with the pre 2.2 LDAP client, result_filter can for now
be used instead of result_format, when the latter parameter is not also
set. The new name better reflects the function of the parameter. This
compatibility interface may be removed in a future release.
LIST MEMBERSHIP
When using LDAP to store lists such as $mynetworks, $mydestination,
$relay_domains, $local_recipient_maps, etc., it is important to
understand that the table must store each list member as a separate
key. The table lookup verifies the *existence* of the key. See "Postfix
lists versus tables" in the DATABASE_README document for a discussion.
Do NOT create tables that return the full list of domains in
$mydestination or $relay_domains etc., or IP addresses in $mynetworks.
DO create tables with each matching item as a key and with an arbitrary
value. With LDAP databases it is not uncommon to return the key itself.
For example, NEVER do this in a map defining $mydestination:
query_filter = domain=*
result_attribute = domain
Do this instead:
query_filter = domain=%s
result_attribute = domain
GENERAL LDAP PARAMETERS
In the text below, default values are given in parentheses. Note:
don’t use quotes in these variables; at least, not until the Postfix
configuration routines understand how to deal with quoted strings.
server_host (default: localhost)
The name of the host running the LDAP server, e.g.
server_host = ldap.example.com
Depending on the LDAP client library you’re using, it should be
possible to specify multiple servers here, with the library
trying them in order should the first one fail. It should also
be possible to give each server in the list a different port
(overriding server_port below), by naming them like
server_host = ldap.example.com:1444
With OpenLDAP, a (list of) LDAP URLs can be used to specify both
the hostname(s) and the port(s):
server_host = ldap://ldap.example.com:1444
ldap://ldap2.example.com:1444
All LDAP URLs accepted by the OpenLDAP library are supported,
including connections over UNIX domain sockets, and LDAP SSL
(the last one provided that OpenLDAP was compiled with support
for SSL):
server_host = ldapi://%2Fsome%2Fpath
ldaps://ldap.example.com:636
server_port (default: 389)
The port the LDAP server listens on, e.g.
server_port = 778
timeout (default: 10 seconds)
The number of seconds a search can take before timing out, e.g.
timeout = 5
search_base (No default; you must configure this)
The RFC2253 base DN at which to conduct the search, e.g.
search_base = dc=your, dc=com
With Postfix 2.2 and later this parameter supports the following
’%’ expansions:
%% This is replaced by a literal ’%’ character.
%s This is replaced by the input key. RFC 2253 quoting is
used to make sure that the input key does not add
unexpected metacharacters.
%u When the input key is an address of the form user@domain,
%u is replaced by the (RFC 2253) quoted local part of the
address. Otherwise, %u is replaced by the entire search
string. If the localpart is empty, the search is
suppressed and returns no results.
%d When the input key is an address of the form user@domain,
%d is replaced by the (RFC 2253) quoted domain part of
the address. Otherwise, the search is suppressed and
returns no results.
%[SUD] For the search_base parameter, the upper-case equivalents
of the above expansions behave identically to their
lower-case counter-parts. With the result_format
parameter (previously called result_filter see the
COMPATIBILITY section and below), they expand to the
corresponding components of input key rather than the
result value.
%[1-9] The patterns %1, %2, ... %9 are replaced by the
corresponding most significant component of the input
key’s domain. If the input key is user@mail.example.com,
then %1 is com, %2 is example and %3 is mail. If the
input key is unqualified or does not have enough domain
components to satisfy all the specified patterns, the
search is suppressed and returns no results.
query_filter (default: mailacceptinggeneralid=%s)
The RFC2254 filter used to search the directory, where %s is a
substitute for the address Postfix is trying to resolve, e.g.
query_filter = (&(mail=%s)(paid_up=true))
This parameter supports the following ’%’ expansions:
%% This is replaced by a literal ’%’ character. (Postfix 2.2
and later).
%s This is replaced by the input key. RFC 2254 quoting is
used to make sure that the input key does not add
unexpected metacharacters.
%u When the input key is an address of the form user@domain,
%u is replaced by the (RFC 2254) quoted local part of the
address. Otherwise, %u is replaced by the entire search
string. If the localpart is empty, the search is
suppressed and returns no results.
%d When the input key is an address of the form user@domain,
%d is replaced by the (RFC 2254) quoted domain part of
the address. Otherwise, the search is suppressed and
returns no results.
%[SUD] The upper-case equivalents of the above expansions behave
in the query_filter parameter identically to their lower-
case counter-parts. With the result_format parameter
(previously called result_filter see the COMPATIBILITY
section and below), they expand to the corresponding
components of input key rather than the result value.
The above %S, %U and %D expansions are available with
Postfix 2.2 and later.
%[1-9] The patterns %1, %2, ... %9 are replaced by the
corresponding most significant component of the input
key’s domain. If the input key is user@mail.example.com,
then %1 is com, %2 is example and %3 is mail. If the
input key is unqualified or does not have enough domain
components to satisfy all the specified patterns, the
search is suppressed and returns no results.
The above %1, ..., %9 expansions are available with
Postfix 2.2 and later.
The "domain" parameter described below limits the input keys to
addresses in matching domains. When the "domain" parameter is
non-empty, LDAP queries for unqualified addresses or addresses
in non-matching domains are suppressed and return no results.
NOTE: DO NOT put quotes around the query_filter parameter.
result_format (default: %s)
Called result_filter in Postfix releases prior to 2.2. Format
template applied to result attributes. Most commonly used to
append (or prepend) text to the result. This parameter supports
the following ’%’ expansions:
%% This is replaced by a literal ’%’ character. (Postfix 2.2
and later).
%s This is replaced by the value of the result attribute.
When result is empty it is skipped.
%u When the result attribute value is an address of the form
user@domain, %u is replaced by the local part of the
address. When the result has an empty localpart it is
skipped.
%d When a result attribute value is an address of the form
user@domain, %d is replaced by the domain part of the
attribute value. When the result is unqualified it is
skipped.
%[SUD1-9]
The upper-case and decimal digit expansions interpolate
the parts of the input key rather than the result. Their
behavior is identical to that described with
query_filter, and in fact because the input key is known
in advance, lookups whose key does not contain all the
information specified in the result template are
suppressed and return no results.
The above %S, %U, %D and %1, ..., %9 expansions are
available with Postfix 2.2 and later.
For example, using "result_format = smtp:[%s]" allows one to use
a mailHost attribute as the basis of a transport(5) table. After
applying the result format, multiple values are concatenated as
comma separated strings. The expansion_limit and size_limit
parameters explained below allow one to restrict the number of
values in the result, which is especially useful for maps that
should return a single value.
The default value %s specifies that each attribute value should
be used as is.
This parameter was called result_filter in Postfix releases
prior to 2.2. If no "result_format" is specified, the value of
"result_filter" will be used instead before resorting to the
default value. This provides compatibility with old
configuration files.
NOTE: DO NOT put quotes around the result format!
domain (default: no domain list)
This is a list of domain names, paths to files, or dictionaries.
When specified, only fully qualified search keys with a *non-
empty* localpart and a matching domain are eligible for lookup:
’user’ lookups, bare domain lookups and "@domain" lookups are
not performed. This can significantly reduce the query load on
the LDAP server.
domain = postfix.org, hash:/etc/postfix/searchdomains
It is best not to use LDAP to store the domains eligible for
LDAP lookups.
NOTE: DO NOT define this parameter for local(8) aliases.
This feature is available in Postfix 1.0 and later.
result_attribute (default: maildrop)
The attribute(s) Postfix will read from any directory entries
returned by the lookup, to be resolved to an email address.
result_attribute = mailbox, maildrop
special_result_attribute (default: empty)
The attribute(s) of directory entries that can contain DNs or
URLs. If found, a recursive subsequent search is done using
their values.
special_result_attribute = memberdn
DN recursion retrieves the same result_attributes as the main
query, including the special attributes for further recursion.
URI processing retrieves only those attributes that are included
in the URI definition and are *also* listed in
"result_attribute". If the URI lists any of the map’s special
result attributes, these are also retrieved and used
recursively.
terminal_result_attribute (default: empty)
When one or more terminal result attributes are found in an LDAP
entry, all other result attributes are ignored and only the
terminal result attributes are returned. This is useful for
delegating expansion of group members to a particular host, by
using an optional "maildrop" attribute on selected groups to
route the group to a specific host, where the group is expanded,
possibly via mailing-list manager or other special processing.
terminal_result_attribute = maildrop
This feature is available with Postfix 2.4 or later.
leaf_result_attribute (default: empty)
When one or more special result attributes are found in a non-
terminal (see above) LDAP entry, leaf result attributes are
excluded from the expansion of that entry. This is useful when
expanding groups and the desired mail address attribute(s) of
the member objects obtained via DN or URI recursion are also
present in the group object. To only return the attribute values
from the leaf objects and not the containing group, add the
attribute to the leaf_result_attribute list, and not the
result_attribute list, which is always expanded. Note, the
default value of "result_attribute" is not empty, you may want
to set it explicitly empty when using "leaf_result_attribute" to
expand the group to a list of member DN addresses. If groups
have both member DN references AND attributes that hold multiple
string valued rfc822 addresses, then the string attributes go in
"result_attribute". The attributes that represent the email
addresses of objects referenced via a DN (or LDAP URI) go in
"leaf_result_attribute".
result_attribute = memberaddr
special_result_attribute = memberdn
terminal_result_attribute = maildrop
leaf_result_attribute = mail
This feature is available with Postfix 2.4 or later.
scope (default: sub)
The LDAP search scope: sub, base, or one. These translate into
LDAP_SCOPE_SUBTREE, LDAP_SCOPE_BASE, and LDAP_SCOPE_ONELEVEL.
bind (default: yes)
Whether or not to bind to the LDAP server. Newer LDAP
implementations don’t require clients to bind, which saves time.
Example:
bind = no
If you do need to bind, you might consider configuring Postfix
to connect to the local machine on a port that’s an SSL tunnel
to your LDAP server. If your LDAP server doesn’t natively
support SSL, put a tunnel (wrapper, proxy, whatever you want to
call it) on that system too. This should prevent the password
from traversing the network in the clear.
bind_dn (default: empty)
If you do have to bind, do it with this distinguished name.
Example:
bind_dn = uid=postfix, dc=your, dc=com
bind_pw (default: empty)
The password for the distinguished name above. If you have to
use this, you probably want to make the map configuration file
readable only by the Postfix user. When using the obsolete
ldap:ldapsource syntax, with map parameters in main.cf, it is
not possible to securely store the bind password. This is
because main.cf needs to be world readable to allow local
accounts to submit mail via the sendmail command. Example:
bind_pw = postfixpw
cache (IGNORED with a warning)
cache_expiry (IGNORED with a warning)
cache_size (IGNORED with a warning)
The above parameters are NO LONGER SUPPORTED by Postfix. Cache
support has been dropped from OpenLDAP as of release 2.1.13.
recursion_limit (default: 1000)
A limit on the nesting depth of DN and URL special result
attribute evaluation. The limit must be a non-zero positive
number.
expansion_limit (default: 0)
A limit on the total number of result elements returned (as a
comma separated list) by a lookup against the map. A setting of
zero disables the limit. Lookups fail with a temporary error if
the limit is exceeded. Setting the limit to 1 ensures that
lookups do not return multiple values.
size_limit (default: $expansion_limit)
A limit on the number of LDAP entries returned by any single
LDAP search performed as part of the lookup. A setting of 0
disables the limit. Expansion of DN and URL references involves
nested LDAP queries, each of which is separately subjected to
this limit.
Note: even a single LDAP entry can generate multiple lookup
results, via multiple result attributes and/or multi-valued
result attributes. This limit caps the per search resource
utilization on the LDAP server, not the final multiplicity of
the lookup result. It is analogous to the "-z" option of
"ldapsearch".
dereference (default: 0)
When to dereference LDAP aliases. (Note that this has nothing do
with Postfix aliases.) The permitted values are those legal for
the OpenLDAP/UM LDAP implementations:
0 never
1 when searching
2 when locating the base object for the search
3 always
See ldap.h or the ldap_open(3) or ldapsearch(1) man pages for
more information. And if you’re using an LDAP package that has
other possible values, please bring it to the attention of the
postfix-users@postfix.org mailing list.
chase_referrals (default: 0)
Sets (or clears) LDAP_OPT_REFERRALS (requires LDAP version 3
support).
version (default: 2)
Specifies the LDAP protocol version to use.
debuglevel (default: 0)
What level to set for debugging in the OpenLDAP libraries.
LDAP SSL AND STARTTLS PARAMETERS
If you’re using the OpenLDAP libraries compiled with SSL support,
Postfix can connect to LDAP SSL servers and can issue the STARTTLS
command.
LDAP SSL service can be requested by using a LDAP SSL URL in the
server_host parameter:
server_host = ldaps://ldap.example.com:636
STARTTLS can be turned on with the start_tls parameter:
start_tls = yes
Both forms require LDAP protocol version 3, which has to be set
explicitly with:
version = 3
If any of the Postfix programs querying the map is configured in
master.cf to run chrooted, all the certificates and keys involved have
to be copied to the chroot jail. Of course, the private keys should
only be readable by the user "postfix".
The following parameters are relevant to LDAP SSL and STARTTLS:
start_tls (default: no)
Whether or not to issue STARTTLS upon connection to the server.
Don’t set this with LDAP SSL (the SSL session is setup
automatically when the TCP connection is opened).
tls_ca_cert_dir (No default; set either this or tls_ca_cert_file)
Directory containing X509 Certificate Authority certificates in
PEM format which are to be recognized by the client in SSL/TLS
connections. The files each contain one CA certificate. The
files are looked up by the CA subject name hash value, which
must hence be available. If more than one CA certificate with
the same name hash value exist, the extension must be different
(e.g. 9d66eef0.0, 9d66eef0.1 etc). The search is performed in
the ordering of the extension number, regardless of other
properties of the certificates. Use the c_rehash utility (from
the OpenSSL distribution) to create the necessary links.
tls_ca_cert_file (No default; set either this or tls_ca_cert_dir)
File containing the X509 Certificate Authority certificates in
PEM format which are to be recognized by the client in SSL/TLS
connections. This setting takes precedence over tls_ca_cert_dir.
tls_cert (No default; you must set this)
File containing client’s X509 certificate to be used by the
client in SSL/ TLS connections.
tls_key (No default; you must set this)
File containing the private key corresponding to the above
tls_cert.
tls_require_cert (default: no)
Whether or not to request server’s X509 certificate and check
its validity when establishing SSL/TLS connections. The
supported values are no and yes.
With no, the server certificate trust chain is not checked, but
with OpenLDAP prior to 2.1.13, the name in the server
certificate must still match the LDAP server name. With OpenLDAP
2.0.0 to 2.0.11 the server name is not necessarily what you
specified, rather it is determined (by reverse lookup) from the
IP address of the LDAP server connection. With OpenLDAP prior to
2.0.13, subjectAlternativeName extensions in the LDAP server
certificate are ignored: the server name must match the subject
CommonName. The no setting corresponds to the never value of
TLS_REQCERT in LDAP client configuration files.
Don’t use TLS with OpenLDAP 2.0.x (and especially with x <= 11)
if you can avoid it.
With yes, the server certificate must be issued by a trusted CA,
and not be expired. The LDAP server name must match one of the
name(s) found in the certificate (see above for OpenLDAP library
version dependent behavior). The yes setting corresponds to the
demand value of TLS_REQCERT in LDAP client configuration files.
The "try" and "never" values of TLS_REQCERT have no equivalents
here. They are not available with OpenLDAP 2.0, and in any case
have questionable security properties. Either you want TLS
verified LDAP connections, or you don’t.
The yes value only works correctly with Postfix 2.5 and later,
or with OpenLDAP 2.0. Earlier Postfix releases or later OpenLDAP
releases don’t work together with this setting. Support for LDAP
over TLS was added to Postfix based on the OpenLDAP 2.0 API.
tls_random_file (No default)
Path of a file to obtain random bits from when /dev/[u]random is
not available, to be used by the client in SSL/TLS connections.
tls_cipher_suite (No default)
Cipher suite to use in SSL/TLS negotiations.
EXAMPLE
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.
SEE ALSO
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
mysql_table(5), MySQL lookup tables
pgsql_table(5), PostgreSQL lookup tables
README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate
this information.
DATABASE_README, Postfix lookup table overview
LDAP_README, Postfix LDAP client guide
LICENSE
The Secure Mailer license must be distributed with this software.
AUTHOR(S)
Carsten Hoeger, Hery Rakotoarisoa, John Hensley, Keith Stevenson,
LaMont Jones, Liviu Daia, Manuel Guesdon, Mike Mattice, Prabhat K
Singh, Sami Haahtinen, Samuel Tardieu, Victor Duchovni, and many
others.