SLAPD-LDAP(5)

NAME
slapd-ldap - LDAP backend to slapd

SYNOPSIS
ETCDIR/slapd.conf

DESCRIPTION
The LDAP backend to slapd(8) is not an actual database; instead it acts as a proxy to forward incoming requests to another LDAP server. While processing requests it will also chase referrals, so that referrals are fully processed instead of being returned to the slapd client. Sessions that explicitly Bind to the back-ldap database always create their own private connection to the remote LDAP server. Anonymous sessions will share a single anonymous connection to the remote server. For sessions bound through other mechanisms, all sessions with the same DN will share the same connection. This connection pooling strategy can enhance the proxy's efficiency by reducing the overhead of repeatedly making/breaking multiple connections. The ldap database can also act as an information service, i.e. the identity of locally authenticated clients is asserted to the remote server, possibly in some modified form. For this purpose, the proxy binds to the remote server with some administrative identity, and, if required, authorizes the asserted identity. See the idassert-* rules below. The administrative identity of the proxy, on the remote server, must be allowed to authorize by means of appropriate authzTo rules; see slapd.conf(5) for details.

CONFIGURATION
These slapd.conf options apply to the LDAP backend database. That is, they must follow a "database ldap" line and come before any subsequent "backend" or "database" lines. Other database options are described in the slapd.conf(5) manual page.

Note: In early versions of back-ldap it was recommended to always set

    lastmod  off

for every ldap and meta database. This is because operational attributes related to entry creation and modification should not be used, as they could be passed to the target servers, generating an error. The current implementation automatically sets ldapmod to off, so its use is redundant and can be safely omitted.

uri <ldapurl>
    LDAP server to use. Multiple URIs can be set in in a single ldapurl argument, resulting in the underlying library automatically call the first server of the list that responds, e.g. uri "ldap://host/ ldap://backup-host" The URI list is space- or comma-separated.

acl-authcDN <administrative DN for access control purposes>
    DN which is used to query the target server for acl checking; it is supposed to have read access on the target server to attributes used on the proxy for acl checking. There is no risk of giving away such values; they are only used to check permissions. The acl-authcDN identity is by no means implicitly used by the proxy when the client connects anonymously. See the idassert-* feature instead.

acl-passwd <password>
    Password used with the acl-authcDN above.

idassert-authcdn <administrative DN for proxyAuthz purposes>
    DN which is used to propagate the client's identity to the target by means of the proxyAuthz control when the client does not belong to the DIT fragment that is being proxyied by back-ldap. This is useful when operations performed by users bound to another backend are propagated through back-ldap. This requires the entry with idassert-authcdn identity on the remote server to have proxyAuthz privileges on a wide set of DNs, e.g. authzTo=dn.subtree:"", and the remote server to have authz-policy set to to or both. See slapd.conf(5) for details on these statements and for remarks and drawbacks about their usage.

idassert-passwd <password>
    Password used with the idassert-authcdn above.

idassert-mode <mode> [<flags>]
    defines what type of identity assertion is used. The supported modes are: <mode> := {legacy|anonymous|none|<id>|self} <flags> := {override} <id> := {u:<ID>|[dn:]<DN>} The default is legacy, which implies that the proxy will bind as idassert-authcdn and assert the client's identity when it is not anonymous. Direct binds are always proxied. The other modes imply that the proxy will always bind as idassert-authcdn, unless restricted by idassert-authzFrom rules (see below), in which case the operation will fail; eventually, it will assert some other identity according to <mode>. Other identity assertion modes are anonymous and self, which respectively mean that the empty or the client's identity will be asserted; none, which means that no proxyAuthz control will be used, so the idassert-authcdn identity will be asserted. Moreover, if a string prefixed with u: or dn: is used as <mode>, that identity will be asserted. Ths string is also treated as a DN if it is not prefixed by any recognized type indicator. Whether or not the dn: prefix is present, the string must pass DN validation and normalization. For all modes that require the use of the proxyAuthz control, on the remote server the proxy identity must have appropriate authzTo permissions, or the asserted identities must have appropriate authzFrom permissions. Note, however, that the ID assertion feature is mostly useful when the asserted identities do not exist on the remote server. When the override flag is used, identity assertion takes place even when the database is authorizing for the identity of the client, i.e. after binding with the provided identity, and thus authenticating it, the proxy performs the identity assertion using the configured identity and authentication method.

idassert-authzFrom <authz-regexp>
    if defined, selects what local identities are authorized to exploit the identity assertion feature. The string <authz-regexp> follows the rules defined for the authzFrom attribute. See slapd.conf(5), section related to authz-policy, for details on the syntax of this field.

idassert-method <method> [<saslargs>]
    where valid method values are <method> := {none|simple|sasl} <saslargs> := [mech=<mech>] [realm=<realm>] [authcid=<authcid>] [cred=<cred>] [authz={native|proxyauthz}] If method is sasl, extra parameters can be given as described above. The default is simple; none inhibits proxy authorization; sasl uses a SASL bind with the above parameters; if required, authorization is performed by means of native SASL mechanism, and no proxyAuthz is used for subsequent operations.

proxy-whoami
    Turns on proxying of the WhoAmI extended operation. If this option is given, back-ldap will replace slapd's original WhoAmI routine with its own. On slapd sessions that were authenticated by back-ldap, the WhoAmI request will be forwarded to the remote LDAP server. Other sessions will be handled by the local slapd, as before. This option is mainly useful in conjunction with Proxy Authorization.

rebind-as-user
    If this option is given, the client's bind credentials are remembered for rebinds when chasing referrals. Useful in conjunction with chase-referrals, useless if dont-chase-referrals is set.

chase-referrals
dont-chase-referrals
    enable/disable automatic referral chasing, which is delegated to the underlying libldap, with rebinding eventually performed if the rebind-as-user directive is used. The default is to chase referrals.

tls-start
tls-try-start
tls-propagate
tls-try-propagate
    execute the start TLS extended operation when the connection is initialized; only works if the URI directive protocol scheme is not ldaps://. The tls-propagate version issues the Start TLS exop only if the original connection did. try-start-tls and try-propagate-tls continue operations if start TLS failed.

suffixmassage, map, rewrite*
    These directives are no longer supported by back-ldap; their functionality is now delegated to the rwm overlay; see slapo-rwm(5) for details. However, to ease update from existing configurations, back-ldap still recognizes them and automatically instantiates the rwm overlay if available and not instantiated yet. This behavior may change in the future.

PROXY CACHE OVERLAY
The proxy cache overlay allows caching of LDAP search requests (queries) in a local database. See slapo-pcache(5) for details.

FILES

ETCDIR/slapd.conf
    default slapd configuration file

SEE ALSO
slapd.conf(5), slapd-meta(5), slapo-pcache(5), slapo-rwm(5), slapd(8), ldap(3).

AUTHOR
Howard Chu, with enhancements by Pierangelo Masarati