This document contains information on what options are used by the Cyrus SASL library and bundled mechanisms. The most commonly used options (and those that are therefore most commonly misunderstood are pwcheck_method and auxprop_plugin. Please ensure that you have configured these correctly if things don’t seem to be working right. Additionally, mech_list can be an easy way to limit what mechanisms a given application will use.

SASL Library

authdaemon_path [<path>]

Path to Courier-IMAP authdaemond’s unix socket.

Default: /dev/null

auto_transition [yes|noplain|no]

When set to ‘yes’ or ‘noplain’, and when using an auxprop plugin, automatically transition users to other mechs when they do a successful plaintext authentication. When set to ‘noplain’, only non-plaintext secrets will be written. Note that the only mechanisms (as currently implemented) which don’t use plaintext secrets are OTP, SCRAM and SRP.

Default: no

canon_user_plugin [<name>]

Name of canon_user plugin to use


log_level [<numeric log level>]

Numeric Logging Level (see SASL_LOG_* in sasl.h for values and descriptions)

Default: 1 (SASL_LOG_ERR)

mech_list [<mechanism list>]

Whitespace separated list of mechanisms to allow (e.g. ‘plain otp’). Used to restrict the mechanisms to a subset of the installed plugins.

Default: empty (use all available plugins)

plugin_list [<path>]

Location of Plugin list (Unsupported)

Default: none

pwcheck_method [<list of mechanisms>]

Whitespace separated list of mechanisms used to verify passwords, used by sasl_checkpass. Possible values: ‘auxprop’, ‘saslauthd’, ‘pwcheck’, ‘authdaemond’ [if compiled with –with-authdaemond]) and ‘alwaystrue’ [if compiled with –enable-alwaystrue])

Default: auxprop

saslauthd_path [<path>]

Path to saslauthd run directory (including the “/mux” named pipe)

Auxiliary Property Plugin

auxprop_plugin [<list of plugin names>]

Name of auxiliary plugin to use, you may specify a space-separated list of plugin names, and the plugins will be queried in order.

Default: empty - queries all plugins.


keytab [<path>]

Location of keytab file

Default: /etc/krb5.keytab (system dependant)

ccache_store [<path>]

Location where cached credentials are stored, For example this could be FILE:/path/to/credstore/krb5cc_%U. Formatting options are:

%u UID of the logged in user (only valid for existing UNIX users) %U username of the logged in user %e EUID of the executing process user %E username of the executing process user %p PID process ID of the executing process

Note that not all formatting options may not be available for all target environments. See the log files for indications in run-time. If this option can not be parsed correctly credentials cache will fall-back to the contents of the KRB5CCNAME environment variable.

If this option is omitted, credentials delegation will not be enabled.

See MIT Kerberos documentation on more information about credentials cache storage.

Default: None, if omitted, no credentials cache/delegation and if left empty or invalid KRB5CCNAME will be used.

ad_compat [yes | no]

When set to ‘yes’, ‘on’, ‘1’ or ‘true’, a client will request both confidentiality and integrity when required by Active Directory.

Default: no

service_principal [<GSS_C_NT_HOSTBASED_SERVICE> | *]

Service principal to use when accepting a connection as a server. The principal name must be in GSS_C_NT_HOSTBASED_SERVICE form, e.g. “someservice@someinstance” or “someservice”, or the string “*”, which causes the server to accept any valid principal present in its keytab.

Default: <SASL Service Name>@<Server FQDN>


ldapdb_uri [<list of URIs>]

URI to the LDAP server. You can specify a space-separated list of URIs - ldapi:// or ldaps://ldap1/ ldaps://ldap2/

Default: none

ldapdb_id [<auth id>]

ldap SASL authentication id

Default: none

ldapdb_mech [<mechanism>]

LDAP SASL mechanism for authentication.

Default: none

ldapdb_pw [<password>]

LDAP password for SASL authentication id

Default: none

ldapdb_rc [<filename>]

The filename specified here will be put into the server’s LDAPRC environment variable, and libldap-specific config options may be set in that ldaprc file.

The main purpose behind this option is to allow a client TLS certificate to be configured, so that SASL/EXTERNAL may be used between the SASL server and the LDAP server. This is the most optimal way to use this plugin when the servers are on separate machines.

Default: none

ldapdb_starttls [try|demand]

Use StartTLS. This option may be set to ‘try’ or ‘demand’. When set to “try” any failure in StartTLS is ignored. When set to “demand” then any failure aborts the connection.

Default: none

ldapdb_canon_attr [<user's canonical name>]

Use the value of the specified attribute as the user’s canonical name. The attribute will be looked up in the user’s LDAP entry. This setting must be configured in order to use LDAPDB as a canonuser plugin.

Default: none

Notes on LDAPDB

Unlike other LDAP-enabled plugins for other services that are common on the web, this plugin does not require you to configure DN search patterns to map usernames to LDAP DNs. This plugin requires SASL name mapping to be configured on the target slapd. This approach keeps the LDAP-specific configuration details in one place, the slapd.conf, and makes the configuration of remote services much simpler.

This plugin is not for use with slapd itself. When OpenLDAP is built with SASL support, slapd uses its own internal auxprop and canonuser module.

By default, without configuring anything else, slapd will fail to load the ldapdb module when it’s present. This is as it should be. If you don’t like the “auxpropfunc: error -7” message that is sent to syslog by slapd, you can stop it by creating /usr/lib/sasl2/slapd.conf with:

auxprop_plugin: slapd

which will force the SASL library to ignore all other auxprop modules.


ldapdb_uri: ldap://ldap.example.com
ldapdb_id: root
ldapdb_pw: secret
ldapdb_mech: SCRAM-SHA-512
ldapdb_canon_attr: uid

The LDAP server must be configured to map the SASL authcId “root” into a DN that has proxy authorization privileges to every account that is allowed to login to this server. (See the OpenLDAP Admin Guide section 10 for details.)

ldapdb_uri: ldapi://
ldapdb_mech: EXTERNAL

This configuration assumes an LDAP server is on the same server that is using SASL and the underlying OS is *NIX based (ldapi:// requires UNIX domain sockets). This is fast and secure, and needs no username or password to be stored. The slapd.conf will need to map these usernames to LDAP DNs:

sasl-regexp uidNumber=(.*)\\+gidNumber=(.*),cn=peercred,cn=external,cn=auth

sasl-regexp uid=(.*),cn=external,cn=auth


opiekeys [<path>]

Location of the opiekeys file

Default: /etc/opiekeys

otp_mda [md4 | md5 | sha1]

(Without opie) Message digest algorithm for one-time passwords, used by sasl_setpass

Default: md5


sasldb_path [<path to sasldb file>]

Path to sasldb file

Default: /etc/sasldb2 (system dependant)

sasldb_mapsize [<size in bytes>]

For sasldb with LMDB. Size of the memory map used by the DB. This is also the maximum possible size of the database, so it must be set to a value large enough to contain all the desired user records.

Default: 1048576 bytes

sasldb_maxreaders [<max threads>]

For sasldb with LMDB. Maximum number of threads (or processes) that may concurrently read the database.

Default: 126

Notes on sasldb with LMDB

The OpenLDAP LMDB library is an extremely compact, extremely high performance B+tree database. The code for it is available in the regular OpenLDAP source distributions and it is distributed under the terms of the OpenLDAP Public License.

Full documentation, plus papers and presentations are available on the LMDB page.

SQL Plugin

sql_engine [<name>]

Name of SQL engine to use (possible values: ‘mysql’, ‘pgsql’, ‘sqlite’, ‘sqlite3’).

Default: mysql

sql_hostnames [<list of SQL servers>]

Comma separated list of SQL servers (in host[:port] format).

sql_user <username>

Username to use for authentication to the SQL server.

sql_passwd <password>

Password to use for authentication to the SQL server.

sql_database <database name>

Name of the database which contains the auxiliary properties.

sql_select <statement>

SELECT statement to use for fetching properties. This option is required in order to use the SQL plugin.

sql_insert <statement>

INSERT statement to use for creating properties for new users.

sql_update <statement>

UPDATE statement to use for modifying properties.

Notes on SQL

The sql_insert and sql_update options are optional and are only needed if you wish to allow the SASL library (e.g., saslpasswd2) and plugins (e.g., OTP) to write properties to the SQL server. If used, both statements MUST be provided so that properties can be added, changed and deleted.

NOTE: The columns for writable properties MUST accept NULL values.

The SQL statements provided in the sql_select, sql_insert and sql_update options can contain arguments which will be substituted with the appropriate values. The valid arguments are:


Username whose properties are being fetched/stored.


Name of the property being fetched/stored. This could technically be anything, but SASL authentication will try userPassword and cmusaslsecretMECHNAME (where MECHNAME is the name of a SASL mechanism).


Realm to which the user belongs. This could be the kerberos realm, the FQDN of the computer the SASL application is running on or whatever is after the @ on a username. (read the realm documentation).


Value of the property being stored (INSERT or UPDATE only!). This could technically be anything depending on the property itself, but is generally a userPassword.

Note: DO NOT put quotes around the entire SQL statement, but each individual %u, %r and %v argument MUST be quoted.


sql_select: SELECT %p FROM user_table WHERE username = '%u' and realm = '%r'

would send the following statement to SQL for user “bovik” and the default realm for the machine “madoka.surf.org.uk”:

SELECT userPassword FROM user_table WHERE username = 'bovik' and
realm = 'madoka.surf.org.uk'
sql_insert: INSERT INTO user_table (username, realm, %p) VALUES ('%u', '%r', '%v')

would generate the following statement to SQL for user “bovik” in realm “madoka.surf.org.uk” with userPassword “wert”:

INSERT INTO user_table (username, realm, userPassword) VALUES
('bovik', 'madoka.surf.org.uk', 'wert');

Note that all substitutions do not have to be used. For instance,

SELECT password FROM auth WHERE username = '%u'

is a valid value for sql_select.


srp_mda [md5 | sha1 | rmd160]

Message digest algorithm for SRP calculations

Default: sha1

Kerberos V4

srvtab [<path>]

Location of the srvtab file

Default: /etc/srvtab