LDAP_TABLE(5) File Formats Manual 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 lmdb:, cdb:, hash:, or dbm:
format.
Alternatively, lookup tables can be specified as LDAP databases. To
find out what types of lookup tables your Postfix system supports use
the "postconf -m" command.
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 Post‐
fix 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 "OBSOLETE MAIN.CF PARAMETERS" below for older
Postfix versions.
For details about LDAP SSL and STARTTLS, see the section on SSL and
STARTTLS below.
LIST MEMBERSHIP
When using LDAP to store lists such as $mynetworks, $mydestination,
$relay_domains, $local_recipient_maps, etc., it is important to under‐
stand 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 $mydesti‐
nation 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 try‐
ing them in order should the first one fail. It should also be
possible to give each server in the list a different port (over‐
riding server_port below), by naming them like
server_host = ldap.example.com:1444
NOTE: this client will reconnect immediately after a single
failure, and will fail a lookup request after a second attempt
also fails.
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 unex‐
pected 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 sup‐
pressed 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 re‐
turns 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 parame‐
ter (previously called result_filter see the OTHER OBSO‐
LETE FEATURES section and below), they expand to the cor‐
responding components of input key rather than the result
value.
%[1-9] The patterns %1, %2, ... %9 are replaced by the corre‐
sponding 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 sup‐
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 unex‐
pected 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 sup‐
pressed 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 re‐
turns 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 parame‐
ter (previously called result_filter see the OTHER OBSO‐
LETE FEATURES section and below), they expand to the cor‐
responding 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 corre‐
sponding 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 sup‐
pressed and returns no results.
The above %1, ..., %9 expansions are available with Post‐
fix 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 ap‐
pend (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 ad‐
dress. 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 at‐
tribute 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, and in fact because the input key is known in ad‐
vance, lookups whose key does not contain all the infor‐
mation 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 pa‐
rameters 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 de‐
fault 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 "type:table"
databases. 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
Don't rely on the default value ("maildrop"). Set the result_at‐
tribute explicitly in all ldap table configuration files. This
is particularly relevant when no result_attribute is applicable,
e.g. cases in which leaf_result_attribute and/or terminal_re‐
sult_attribute are used instead. The default value is harmless
if "maildrop" is also listed as a leaf or terminal result at‐
tribute, but it is best to not leave this to chance.
special_result_attribute (default: empty)
The attribute(s) of directory entries that can contain DNs or
RFC 2255 LDAP URLs. If found, a recursive search is performed to
retrieve the entry referenced by the DN, or the entries matched
by the URL query.
special_result_attribute = memberdn
DN recursion retrieves the same result_attributes as the main
query, including the special attributes for further recursion.
URL processing retrieves only those attributes that are included
in both the URL definition and as result attributes (ordinary,
special, leaf or terminal) in the Postfix table definition. If
the URL lists any of the table's special result attributes,
these are retrieved and used recursively. A URL that does not
specify any attribute selection, is equivalent (RFC 2255) to a
URL that selects all attributes, in which case the selected at‐
tributes will be the full set of result attributes in the Post‐
fix table.
If an LDAP URL attribute-descriptor or the corresponding Postfix
LDAP table result attribute (but not both) uses RFC 2255
sub-type options ("attr;option"), the attribute requested from
the LDAP server will include the sub-type option. In all other
cases, the URL attribute and the table attribute must match ex‐
actly. Attributes with options in both the URL and the Postfix
table are requested only when the options are identical. LDAP
attribute-descriptor options are very rarely used, most LDAP
users will not need to concern themselves with this level of nu‐
anced detail.
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 ter‐
minal result attributes are returned. This is useful for dele‐
gating 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.
result_attribute =
terminal_result_attribute = maildrop
When using terminal and/or leaf result attributes, the re‐
sult_attribute is best set to an empty value when it is not
used, or else explicitly set to the desired value, even if it is
the default value "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 at‐
tribute to the leaf_result_attribute list, and not the re‐
sult_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 "re‐
sult_attribute". The attributes that represent the email ad‐
dresses 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
When using terminal and/or leaf result attributes, the re‐
sult_attribute is best set to an empty value when it is not
used, or else explicitly set to the desired value, even if it is
the default value "maildrop".
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 how to bind to the LDAP server. Newer LDAP implemen‐
tations don't require clients to bind, which saves time. Exam‐
ple:
# Don't bind
bind = no
# Use SIMPLE bind
bind = yes
# Use SASL bind
bind = sasl
Postfix versions prior to 2.8 only support "bind = no" which
means don't bind, and "bind = yes" which means do a SIMPLE bind.
Postfix 2.8 and later also supports "bind = SASL" when compiled
with LDAP SASL support as described in LDAP_README, it also adds
the synonyms "bind = none" and "bind = simple" for "bind = no"
and "bind = yes" respectively. See the SASL section below for
additional parameters available with "bind = sasl".
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 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. Ex‐
ample:
bind_dn = uid=postfix, dc=your, dc=com
With "bind = sasl" (see above) the DN may be optional for some
SASL mechanisms, don't specify a DN if not needed.
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 be‐
cause main.cf needs to be world readable to allow local accounts
to submit mail via the sendmail command. Example:
bind_pw = postfixpw
With "bind = sasl" (see above) the password may be optional for
some SASL mechanisms, don't specify a password if not needed.
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 at‐
tribute evaluation. The limit must be a non-zero positive num‐
ber.
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 dis‐
ables 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 re‐
sults, 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 re‐
sult. 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: 3)
Specifies the LDAP protocol version to use.
debuglevel (default: 0)
What level to set for debugging in the OpenLDAP libraries.
LDAP SASL PARAMETERS
If you're using the OpenLDAP libraries compiled with SASL support,
Postfix 2.8 and later built with LDAP SASL support as described in
LDAP_README can authenticate to LDAP servers via SASL.
This enables authentication to the LDAP server via mechanisms other
than a simple password. The added flexibility has a cost: it is no
longer practical to set an explicit timeout on the duration of an LDAP
bind operation. Under adverse conditions, whether a SASL bind times
out, or if it does, the duration of the timeout is determined by the
LDAP and SASL libraries.
It is best to use tables that use SASL binds via proxymap(8), this way
the requesting process can time-out the proxymap request. This also
lets you tailer the process environment by overriding the proxymap(8)
import_environment setting in master.cf(5). Special environment set‐
tings may be needed to configure GSSAPI credential caches or other SASL
mechanism specific options. The GSSAPI credentials used for LDAP
lookups may need to be different than say those used for the Postfix
SMTP client to authenticate to remote servers.
Using SASL mechanisms requires LDAP protocol version 3, the default
protocol version is 2 for backwards compatibility. You must set "ver‐
sion = 3" in addition to "bind = sasl".
The following parameters are relevant to using LDAP with SASL
sasl_mechs (default: empty)
Space separated list of SASL mechanism(s) to try.
sasl_realm (default: empty)
SASL Realm to use, if applicable.
sasl_authz_id (default: empty)
The SASL authorization identity to assert, if applicable.
sasl_minssf (default: 0)
The minimum required sasl security factor required to establish
a connection.
LDAP SSL AND STARTTLS PARAMETERS
If you're using the OpenLDAP libraries compiled with SSL support, Post‐
fix 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 explic‐
itly with:
version = 3
If any of the Postfix programs querying the map is configured in mas‐
ter.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 automati‐
cally when the TCP connection is opened).
tls_ca_cert_dir (No default; set either this or tls_ca_cert_file)
Directory containing X509 Certification 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 prop‐
erties 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 Certification 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 sup‐
ported 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 certifi‐
cate 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 "allow" 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 veri‐
fied 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. As‐
sume 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 listen‐
ing 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.
OBSOLETE MAIN.CF PARAMETERS
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 def‐
inition, 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.
OTHER OBSOLETE FEATURES
result_filter (No default)
For backwards compatibility with the pre 2.2 LDAP clients, re‐
sult_filter can for now be used instead of result_format, when
the latter parameter is not also set. The new name better re‐
flects the function of the parameter. This compatibility inter‐
face may be removed in a future release.
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
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, LaM‐
ont Jones, Liviu Daia, Manuel Guesdon, Mike Mattice, Prabhat K Singh,
Sami Haahtinen, Samuel Tardieu, Victor Duchovni, and many others.
LDAP_TABLE(5)