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 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 main.cf.
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 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.
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 = 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
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. Oth-
erwise, %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.
Otherwise, %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 value is an
address of the form user@domain, %u is
replaced by the local part of the address.
Otherwise, %u is replaced by the entire
attribute value.
%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.
Otherwise, %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 = postfix.org, hash:/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 main.cf, it is not pos-
sible 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 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-
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 config-
ured 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 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 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.my.com
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
ldap.my.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
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)