LDAP_TABLE 5
NAME
ldap_table
-
Postfix LDAP client configuration
"SYNOPSIS"
postmap -q "string" ldap:/etc/postfix/filename postmap -q - ldap:/etc/postfix/filename <inputfileThe 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:DESCRIPTION
alias_maps = ldap:/etc/postfix/ldap-aliases.cfThe 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. For backwards compatibility with the pre 2.2 LDAP clients, 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 = domainDo 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.comDepending 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:1444With 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:1444All 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=comWith 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.
"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.
"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/searchdomainsIt 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, maildropDon't rely on the default value ("maildrop"). Set the result_attribute 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_result_attribute are used instead. The default value is harmless if "maildrop" is also listed as a leaf or terminal result attribute, 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 = memberdnDN 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 attributes will be the full set of result attributes in the Postfix 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 exactly. 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 nuanced 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 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.
result_attribute = terminal_result_attribute = maildropWhen using terminal and/or leaf result attributes, the result_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 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 = mailWhen using terminal and/or leaf result attributes, the result_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
implementations don't require clients to bind, which saves
time. Example:
# Don't bind bind = no # Use SIMPLE bind bind = yes # Use SASL bind bind = saslPostfix 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 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=comWith "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 because main.cf needs to be world readable
to allow local accounts to submit mail via the sendmail
command. Example:
bind_pw = postfixpwWith "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
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
"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 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 settings 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 "version = 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, 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:636STARTTLS can be turned on with the start_tls parameter:
start_tls = yesBoth forms require LDAP protocol version 3, which has to be set explicitly with:
version = 3If 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 "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 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.cfand in ldap:/etc/postfix/ldap-aliases.cf you have:
server_host = ldap.example.com search_base = dc=example, dc=comUpon 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.