LDAP_TABLE(5) LDAP_TABLE(5)
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 spec-
ify 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 "BACK-WARDS "BACKWARDS
WARDS 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 param-eters parameters
eters 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_recipi-ent_maps, $local_recipient_maps,
ent_maps, etc., it is important to understand that the table must store each list member as a sepa-rate separate
rate 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 vari-ables; variables;
ables; 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 compo-nent component
nent 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 sup-pressed suppressed
pressed 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 (previ-ously (previously
ously 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 compo-nent component
nent 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 sup-pressed suppressed
pressed 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 sup-ports supports
ports 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_fil-ter, query_filter,
ter, 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 concate-nated concatenated
nated 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_for-mat" "result_format"
mat" 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 sub-sequent subsequent
sequent 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 "mail-drop" "maildrop"
drop" 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 sup-port support
port 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 uti-lization utilization
lization 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 dif-ferent different
ferent (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 rec-ognized recognized
ognized 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.
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 anony-mously, anonymously,
mously, 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.
LDAP_TABLE(5)
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