""> LDAP_TABLE(5) LDAP_TABLE(5) NAME ldap_table - Postfix LDAP client configuration SYNOPSIS postmap -q "string" ldap:/usr/local/etc/postfix/filename postmap -q - ldap:/usr/local/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, for example: alias_maps = ldap:/usr/local/etc/postfix/ The file /usr/local/etc/postfix/ has the same format as the Postfix file, and can specify the parame- ters described below. An example is given at the end of this manual. This configuration method is available with Postfix ver- sion 2.1 and later. See the section "BACKWARDS COMPATI- BILITY" 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 Specify as LDAP source a name that doesn't begin with a slash or a dot. The LDAP parameters will then be accessi- ble as the name you've given the source in its definition, an underscore, and the name of the parameter. For exam- ple, if the map is specified as "ldap:ldapsource", the "server_host" parameter below would be defined in as "ldapsource_server_host". Note: with this form, the passwords for the LDAP sources are written in, which is normally world-readable. Support for this form will be removed in a future Postfix version. 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 dis- cussion. 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 $mydestina- tion: 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 parenthe- ses. 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 = 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 = With OpenLDAP, a (list of) LDAP URLs can be used to specify both the hostname(s) and the port(s): server_host = ldap:// 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 server_host = ldaps:// server_port (default: 389) The port the LDAP server listens on, e.g. server_port = 778 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 timeout (default: 10 seconds) The number of seconds a search can take before tim- ing out, e.g. timeout = 5 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 '%' expan- sions: %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. If no domain is specified, %u is replaced by the entire search string. %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. When the input key has no domain qualifier, %d is replaced by the entire search string. 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. result_filter (default: %s) Format template applied to result attributes. Sup- ports the same expansions as the query_filter, and can be easily used to append (or prepend) text. This parameter supports the following '%' expan- sions: %s This is replaced by the value of the result attribute. %u When the result attribute is an address of the form user@domain, %u is replaced local part of the address, if the result attribute is unqualified, %u is replaced by the entire attribute value. %d When a result attribute is an address of the form user@domain, %d is replaced by the domain part of the attribute value. If an attribute value is unqualified %d is replaced by the entire attribute value. For example, using "result_filter = smtp:[%s]" allows one to use a mailHost attribute as the basis of a transport(5) table. After applying the result filter, multiple values are concatenated as comma separated strings. The expansion_limit and size_limit parameters explained below allow one to restrict the number of values in the result, which is especially useful for maps that should return a single value. The default value %s specifies that each attribute value should be used as is. NOTE: DO NOT put quotes around the result filter! 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 =, hash:/usr/local/etc/postfix/search- domains 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. result_attribute (default: maildrop) The attribute(s) Postfix will read from any direc- tory entries returned by the lookup, to be resolved to an email address. result_attribute = mailbox,maildrop special_result_attribute (No default) The attribute(s) of directory entries that can con- tain DNs or URLs. If found, a recursive subsequent search is done using their values. special_result_attribute = member 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. 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 config- uring 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 distin- guished 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 syn- tax, with map parameters in, it is not pos- sible to securely store the bind password. This is because needs to be world readable to allow local accounts to submit mail via the sendmail com- mand. 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 query performed as part of the lookup. A setting of 0 disables the limit. Expan- sion 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 multi- ple lookup results, via multiple result attributes and/or multi-valued result attributes. This limit caps the per query resource utilization on the LDAP server, not the final multiplicity of the lookup result. It is analogous to the "-z" option of "ldapsearch". dereference (default: 0) When to dereference LDAP aliases. (Note that this has nothing do with Postfix aliases.) The permitted values are those legal for the OpenLDAP/UM LDAP implementations: 0 never 1 when searching 2 when locating the base object for the search 3 always See ldap.h or the ldap_open(3) or ldapsearch(1) man pages for more information. And if you're using an LDAP package that has other possible values, please bring it to the attention of the postfix- 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:// 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 config- ured in 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 connec- tion 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 recog- nized 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 cer- tificates 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. 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, you have: alias_maps = hash:/etc/aliases, ldap:/usr/local/etc/postfix/ and in ldap:/usr/local/etc/postfix/ you have: server_host = search_base = dc=my, 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 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 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)