LDAP.CONF(5)

📦
version 2.6.16 · 23 versions
, in fedora 44

🌸 NAME 🌸

okay so this is ldap.conf(5), from the File Formats Manual, and it’s all about ldap.conf, .ldaprc — LDAP configuration file/environment variables. bestie, this is the file that tells LDAP clients how to behave before you even touch a command line 💅

✨ SYNOPSIS ✨

/etc/openldap/ldap.conf, ldaprc, .ldaprc, $LDAP<option-name>

💖 DESCRIPTION 💖

first thing’s first: if the environment variable LDAPNOINIT is defined, all defaulting is disabled. like, all of it. no defaults, no vibes, nothing 😭

The ldap.conf configuration file is used to set system-wide defaults to be applied when running ldap clients.

Users may create an optional configuration file, ldaprc or .ldaprc, in their home directory which will be used to override the system-wide defaults file. The file ldaprc in the current working directory is also used.

Additional configuration files can be specified using the LDAPCONF and LDAPRC environment variables. LDAPCONF may be set to the path of a configuration file. This path can be absolute or relative to the current working directory. The LDAPRC, if defined, should be the basename of a file in the current working directory or in the user's home directory.

Environmental variables may also be used to augment the file based defaults. The name of the variable is the option name with an added prefix of LDAP. For example, to define BASE via the environment, set the variable LDAPBASE to the desired value.

Some options are user-only. Such options are ignored if present in the ldap.conf (or file specified by LDAPCONF).

Thus the following files and variables are read, in order:

  • variable — $LDAPNOINIT, and if that is not set:
    • system file — /etc/openldap/ldap.conf,
    • user files — $HOME/ldaprc, $HOME/.ldaprc, ./ldaprc,
    • system file — $LDAPCONF,
    • user files — $HOME/$LDAPRC, $HOME/.$LDAPRC, ./$LDAPRC,
    • variables — $LDAP<uppercase option name>.

Settings late in the list override earlier ones. periodt 💅

🎀 SYNTAX 🎀

The configuration options are case-insensitive; their value, on a case by case basis, may be case-sensitive.

Blank lines are ignored. Lines beginning with a hash mark (#) are comments, and ignored.

Valid lines are made of an option's name (a sequence of non-blanks, conventionally written in uppercase, although not required), followed by a value. The value starts with the first non-blank character after the option's name, and terminates at the end of the line, or at the last sequence of blanks before the end of the line. The tokenization of the value, if any, is delegated to the handler(s) for that option, if any. Quoting values that contain blanks may be incorrect, as the quotes would become part of the value. For example,

# Wrong - erroneous quotes:
URI     "ldap:// ldaps://"

# Right - space-separated list of URIs, without quotes:
URI     ldap:// ldaps://

# Right - DN syntax needs quoting for Example, Inc:
BASE    ou=IT staff,o="Example, Inc",c=US
# or:
BASE    ou=IT staff,o=Example\2C Inc,c=US

# Wrong - comment on same line as option:
DEREF   never           # Never follow aliases

A line cannot be longer than LINE_MAX, which should be more than 2000 bytes on all platforms. There is no mechanism to split a long line on multiple lines, either for beautification or to overcome the above limit.

💅 OPTIONS 💅

The different configuration options are:

  • URI <ldap[si]://[name[:port]] ...> — Specifies the URI(s) of an LDAP server(s) to which the LDAP library should connect. The URI scheme may be any of ldap, ldaps or ldapi, which refer to LDAP over TCP, LDAP over SSL (TLS) and LDAP over IPC (UNIX domain sockets), respectively. Each server's name can be specified as a domain-style name or an IP address literal. Optionally, the server's name can be followed by a : and the port number the LDAP server is listening on. If no port number is provided, the default port for the scheme is used (389 for ldap://, 636 for ldaps://). For LDAP over IPC, name is the name of the socket, and no port is required, nor allowed; note that directory separators must be URL-encoded, like any other characters that are special to URLs; so the socket
/usr/local/var/ldapi

must be specified as

ldapi://%2Fusr%2Flocal%2Fvar%2Fldapi

A space separated list of URIs may be provided.

  • BASE <base> — Specifies the default base DN to use when performing ldap operations. The base must be specified as a Distinguished Name in LDAP format.
  • BINDDN <dn> — Specifies the default bind DN to use when performing ldap operations. The bind DN must be specified as a Distinguished Name in LDAP format. This is a user-only option.
  • DEREF <when> — Specifies how alias dereferencing is done when performing a search. The <when> can be specified as one of the following keywords:
    • never — Aliases are never dereferenced. This is the default.
    • searching — Aliases are dereferenced in subordinates of the base object, but not in locating the base object of the search.
    • finding — Aliases are only dereferenced when locating the base object of the search.
    • always — Aliases are dereferenced both in searching and in locating the base object of the search.
  • HOST <name[:port] ...> — Specifies the name(s) of an LDAP server(s) to which the LDAP library should connect. Each server's name can be specified as a domain-style name or an IP address and optionally followed by a : and the port number the ldap server is listening on. A space separated list of hosts may be provided. HOST is deprecated in favor of URI.
  • KEEPALIVE_IDLE — Sets/gets the number of seconds a connection needs to remain idle before TCP starts sending keepalive probes. Linux only.
  • KEEPALIVE_PROBES — Sets/gets the maximum number of keepalive probes TCP should send before dropping the connection. Linux only.
  • KEEPALIVE_INTERVAL — Sets/gets the interval in seconds between individual keepalive probes. Linux only.
  • NETWORK_TIMEOUT <integer> — Specifies the timeout (in seconds) after which the poll(2)/select(2) following a connect(2) returns in case of no activity.
  • PORT <port> — Specifies the default port used when connecting to LDAP servers(s). The port may be specified as a number. PORT is deprecated in favor of URI.
  • REFERRALS <on/true/yes/off/false/no> — Specifies if the client should automatically follow referrals returned by LDAP servers. The default is on. Note that the command line tools ldapsearch(1) &co always override this option.
  • SIZELIMIT <integer> — Specifies a size limit (number of entries) to use when performing searches. The number should be a non-negative integer. SIZELIMIT of zero (0) specifies a request for unlimited search size. Please note that the server may still apply any server-side limit on the amount of entries that can be returned by a search operation.
  • SOCKET_BIND_ADDRESSES <IP> — Specifies the source bind IP to be used for connecting to target LDAP server. Multiple IP addresses must be space separated. Only one valid IPv4 address and/or one valid IPv6 address are allowed in the list.
  • TIMELIMIT <integer> — Specifies a time limit (in seconds) to use when performing searches. The number should be a non-negative integer. TIMELIMIT of zero (0) specifies unlimited search time to be used. Please note that the server may still apply any server-side limit on the duration of a search operation.
  • VERSION {2|3} — Specifies what version of the LDAP protocol should be used.
  • TIMEOUT <integer> — Specifies a timeout (in seconds) after which calls to synchronous LDAP APIs will abort if no response is received. Also used for any ldap_result(3) calls where a NULL timeout parameter is supplied.

🦋 SASL OPTIONS 🦋

If OpenLDAP is built with Simple Authentication and Security Layer support, there are more options you can specify.

  • SASL_MECH <mechanism> — Specifies the SASL mechanism to use.
  • SASL_REALM <realm> — Specifies the SASL realm.
  • SASL_AUTHCID <authcid> — Specifies the authentication identity. This is a user-only option.
  • SASL_AUTHZID <authcid> — Specifies the proxy authorization identity. This is a user-only option.
  • SASL_SECPROPS <properties> — Specifies Cyrus SASL security properties. The <properties> can be specified as a comma-separated list of the following:
    • none — (without any other properties) causes the properties defaults ("noanonymous,noplain") to be cleared.
    • noplain — disables mechanisms susceptible to simple passive attacks.
    • noactive — disables mechanisms susceptible to active attacks.
    • nodict — disables mechanisms susceptible to passive dictionary attacks.
    • noanonymous — disables mechanisms which support anonymous login.
    • forwardsec — requires forward secrecy between sessions.
    • passcred — requires mechanisms which pass client credentials (and allows mechanisms which can pass credentials to do so).
    • minssf=<factor> — specifies the minimum acceptable security strength factor as an integer approximate to effective key length used for encryption. 0 (zero) implies no protection, 1 implies integrity protection only, 128 allows RC4, Blowfish and other similar ciphers, 256 will require modern ciphers. The default is 0.
    • maxssf=<factor> — specifies the maximum acceptable security strength factor as an integer (see minssf description). The default is INT_MAX.
    • maxbufsize=<factor> — specifies the maximum security layer receive buffer size allowed. 0 disables security layers. The default is 65536.
  • SASL_NOCANON <on/true/yes/off/false/no> — Do not perform reverse DNS lookups to canonicalize SASL host names. The default is off.
  • SASL_CBINDING <none/tls-unique/tls-endpoint> — The channel-binding type to use, see also LDAP_OPT_X_SASL_CBINDING. The default is none.

✨ GSSAPI OPTIONS ✨

Okay so if your OpenLDAP was built with Generic Security Services Application Programming Interface support (yes that's a mouthful, just say GSSAPI bestie), you get extra options to play with. Extra options = extra slay 💅

  • GSSAPI_SIGN <on/true/yes/off/false/no> — controls whether GSSAPI signing (GSS_C_INTEG_FLAG) gets used. Default is off. Turn it on if you want that integrity check energy 🔥
  • GSSAPI_ENCRYPT <on/true/yes/off/false/no> — controls whether GSSAPI encryption (GSS_C_INTEG_FLAG and GSS_C_CONF_FLAG) gets used. Default is off. Yes, both flags, it's giving full protection 🛡️
  • GSSAPI_ALLOW_REMOTE_PRINCIPAL <on/true/yes/off/false/no> — says whether GSSAPI-based auth should try to build the target principal name out of the ldapServiceName or dnsHostName attribute from the target's RootDSE entry. Default is off. Fancy remote principal behavior, iykyk ✨

🌈 TLS OPTIONS 🌈

If OpenLDAP was built with Transport Layer Security support, congrats, you get even more options. These kick in when an ldaps:// URI gets selected (by default or otherwise) or when the app negotiates TLS by sending the LDAP StartTLS operation 🔐

Random but important lore: when using OpenSSL, if neither TLS_CACERT nor TLS_CACERTDIR is set, the system-wide default set of CA certificates is used. No cap.
  • TLS_CACERT <filename> — points at the file holding the certificates for all the Certificate Authorities your client will recognize. The whole trusted squad in one file 💖
  • TLS_CACERTDIR <path> — points at the path(s) of directories that contain Certificate Authority certificates as separate individual files. Multiple directories may be specified, separated by a semi-colon. TLS_CACERT is always used before TLS_CACERTDIR. That directory has to be managed with the OpenSSL c_rehash utility — non-negotiable bestie 🎀
  • TLS_CERT <filename> — the file that contains the client certificate. Heads up: this is a user-only option.
  • TLS_ECNAME <name> — specifies the name of the curve(s) to use for Elliptic curve Diffie-Hellman ephemeral key exchange. Only used for OpenSSL. It is not used with GnuTLS — for GnuTLS you pick curves in the GnuTLS ciphersuite specification instead. Different vibes, different rules 🦋
  • TLS_KEY <filename> — the file with the private key that matches the certificate sitting in the TLS_CERT file. Currently the private key must not be protected with a password, so it is of critical importance that you protect that key file carefully 😭 Like fr fr, guard it with your life. Also a user-only option.
  • TLS_CIPHER_SUITE <cipher-suite-spec> — sets the acceptable cipher suite and the preference order. <cipher-suite-spec> should be a cipher specification for the TLS library in use (OpenSSL or GnuTLS). Examples, bestie:
OpenSSL:
       TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv2

GnuTLS:
       TLS_CIPHER_SUITE SECURE256:!AES-128-CBC

Wanna check what ciphers a given spec actually selects in OpenSSL? Run this:

openssl ciphers -v <cipher-suite-spec>

With GnuTLS the available specs live in the manual page of gnutls-cli(1) — look at the description of the --priority option 👑

In older versions of GnuTLS where gnutls-cli does not support the --priority option, you can get the — more limited — list of ciphers by calling:

gnutls-cli -l
  • TLS_PROTOCOL_MIN <major>[.<minor>] — sets the minimum SSL/TLS protocol version that will be negotiated. If the server doesn't support at least that version, the SSL handshake fails 💀 To require TLS 1.x or higher, set this option to 3.(x+1), like:
TLS_PROTOCOL_MIN 3.2

which would require TLS 1.1. If you specify a minimum higher than what the OpenLDAP implementation supports, it'll just require the highest level it does support (it's doing its best okay 🙈). This parameter is ignored with GnuTLS.

  • TLS_RANDFILE <filename> — the file to grab random bits from when /dev/[u]random isn't available. Generally set to the name of the EGD/PRNGD socket. The environment variable RANDFILE can also be used to specify the filename. This parameter is ignored with GnuTLS. Chaos goblin randomness, but make it configurable ✨
  • TLS_REQCERT <level> — what checks to perform on server certificates in a TLS session. <level> can be one of these keywords:
    • never — the client will not request or check any server certificate.
    • allow — the server certificate is requested. If a bad certificate is provided, it will be ignored and the session proceeds normally.
    • try — the server certificate is requested. If a bad certificate is provided, the session is immediately terminated.
    • demand | hard — these keywords are equivalent and the same as try. This is the default setting.
  • TLS_REQSAN <level> — what checks to perform on the subjectAlternativeName (SAN) extensions in a server certificate when validating the certificate name against the specified hostname of the server. <level> can be one of these keywords:
    • never — the client will not check any SAN in the certificate.
    • allow — the SAN is checked against the specified hostname. If a SAN is present but none match the specified hostname, the SANs are ignored and the usual check against the certificate DN is used. This is the default setting.
    • try — the SAN is checked against the specified hostname. If no SAN is present in the server certificate, the usual check against the certificate DN is used. If a SAN is present but doesn't match the specified hostname, the session is immediately terminated. This setting may be preferred when a mix of certs with and without SANs are in use.
    • demand | hard — these keywords are equivalent. The SAN is checked against the specified hostname. If no SAN is present in the server certificate, or no SANs match, the session is immediately terminated. This setting should be used when only certificates with SANs are in use. All-or-nothing energy 👑
  • TLS_CRLCHECK <level> — says whether the Certificate Revocation List (CRL) of the CA should be used to verify that server certificates haven't been revoked. This requires the TLS_CACERTDIR parameter to be set. This parameter is ignored with GnuTLS. <level> can be one of these keywords:
    • none — no CRL checks are performed.
    • peer — check the CRL of the peer certificate.
    • all — check the CRL for a whole certificate chain. Comprehension check, bestie 💅
  • TLS_CRLFILE <filename> — the file containing a Certificate Revocation List used to verify that server certificates haven't been revoked. This parameter is only supported with GnuTLS 🧚

🫶 ENVIRONMENT VARIABLES 🫶

  • LDAPNOINIT — disable all defaulting. Yes, all of it.
  • LDAPCONF — path of a configuration file.
  • LDAPRC — basename of ldaprc file in $HOME or $CWD.
  • LDAP<option-name> — set <option-name> as from ldap.conf. Sneaky little override, love that for you ✨

🎀 FILES 🎀

  • /etc/openldap/ldap.conf — system-wide ldap configuration file. The main character 🎀
  • $HOME/ldaprc, $HOME/.ldaprc — user ldap configuration file 🌸
  • $CWD/ldaprc — local ldap configuration file 🦋

💜 SEE ALSO 💜

ldap(3), ldap_set_option(3), ldap_result(3), openssl(1), sasl(3) — go read those too, bestie, they're iconic 👑

⭐ AUTHOR ⭐

Kurt Zeilenga, The OpenLDAP Project 💖

🌟 ACKNOWLEDGEMENTS 🌟

OpenLDAP Software is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>. OpenLDAP Software is derived from the University of Michigan LDAP 3.3 Release. Respect the lineage, periodt 🫶

And that's the whole page, bestie 💅 This was OpenLDAP 2.6.16, dated 2026/10/21 — LDAP.CONF(5), signing off 🌈✨

📦 where this page comes from