LDAP_TABLESection: File Formats (5)
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NAMEldap_table - Postfix LDAP client configuration
postmap -q "string" ldap:/etc/postfix/filename postmap -q - ldap:/etc/postfix/filename <inputfile
DESCRIPTIONThe 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.
BACKWARDS COMPATIBILITYFor 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 MEMBERSHIPWhen 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 PARAMETERSIn 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.
- This is replaced by the input key. RFC 2253 quoting is used to make sure that the input key does not add unexpected metacharacters.
- When the input key is an address of the form [email protected], %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.
- When the input key is an address of the form [email protected], %d is replaced by the (RFC 2253) quoted domain part of the address. Otherwise, the search is suppressed and returns no results.
- 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.
- The patterns %1, %2, ... %9 are replaced by the corresponding most significant component of the input key's domain. If the input key is [email protected], 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,
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).
- This is replaced by the input key. RFC 2254 quoting is used to make sure that the input key does not add unexpected metacharacters.
- When the input key is an address of the form [email protected], %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.
- When the input key is an address of the form [email protected], %d is replaced by the (RFC 2254) quoted domain part of the address. Otherwise, the search is suppressed and returns no results.
- 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.
- 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).
- This is replaced by the value of the result attribute. When result is empty it is skipped.
- When the result attribute value is an address of the form [email protected], %u is replaced by the local part of the address. When the result has an empty localpart it is skipped.
- When a result attribute value is an address of the form [email protected], %d is replaced by the domain part of the attribute value. When the result is unqualified it is skipped.
- 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
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
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
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
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:
- when searching
- when locating the base object for the search
- 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 [email protected] 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 PARAMETERSIf 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.
EXAMPLEHere'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.
postmap(1), Postfix lookup table manager postconf(5), configuration parameters mysql_table(5), MySQL lookup tables pgsql_table(5), PostgreSQL lookup tables
README FILESUse "postconf readme_directory" or "postconf html_directory" to locate this information.
DATABASE_README, Postfix lookup table overview LDAP_README, Postfix LDAP client guide
LICENSEThe 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.
- BACKWARDS COMPATIBILITY
- LIST MEMBERSHIP
- GENERAL LDAP PARAMETERS
- LDAP SSL AND STARTTLS PARAMETERS
- SEE ALSO
- README FILES
This document was created by man2html, using the manual pages.
Time: 05:34:00 GMT, December 24, 2015