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.
For backwards compatibility with the pre 2.2 LDAP clients,
result_filter can for now be used instead of result_for-
mat, 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 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
timeout (default: 10 seconds)
The number of seconds a search can take before tim-
ing 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 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 param-
eter (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 [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 speci-
fied 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 '%' expan-
sions:
%% 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 param-
eter identically to their lower-case
counter-parts. With the result_format param-
eter (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 [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 speci-
fied patterns, the search is suppressed and
returns no results.
The above %1, ..., %9 expansions are avail-
able 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).
%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_fil-
ter, 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 expan-
sions 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 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 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 direc-
tory 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_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 termi-
nal_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 con-
tain DNs or RFC 2255 LDAP URLs. If found, a recur-
sive search is performed to retrieve the entry ref-
erenced 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 ter-
minal) 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 corre-
sponding 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 expan-
sion 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 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 expan-
sion 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
When 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 = 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 avail-
able with "bind = sasl".
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
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 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
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 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. 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 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
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-
[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 SASL PARAMETERS
If you're using the OpenLDAP libraries compiled with SASL
support, Postfix 2.8 and later built with LDAP SASL sup-
port as described in LDAP_README can authenticate to LDAP
servers via SASL.
This enables authentication to the LDAP server via mecha-
nisms 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 prox-
ymap(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_environ-
ment setting in master.cf(5). Special environment settings
may be needed to configure GSSAPI credential caches or
other SASL mechanism specific options. The GSSAPI creden-
tials 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 compati-
bility. 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: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. 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 con-
figuration 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.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.exam-
ple.com. It will bind anonymously, search for any direc-
tory 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 deliv-
ered.
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)