integrity and confidentiality protections and to support
LDAP authentication using the {{TERM:SASL}} EXTERNAL mechanism.
+H2: TLS Certificates
+
TLS uses {{TERM:X.509}} certificates to carry client and server
identities. All servers are required to have valid certificates,
whereas client certificates are optional. Clients must have a
For more information on creating and managing certificates,
see the {{PRD:OpenSSL}} documentation.
-H2: Server Certificates
+H3: Server Certificates
The DN of a server certificate must use the CN attribute
to name the server, and the {{EX:CN}} must carry the server's
may be present in the {{EX:subjectAltName}} certificate extension.
More details on server certificate names are in {{REF:RFC2830}}.
-H2: Client Certificates
+H3: Client Certificates
The DN of a client certificate can be used directly as an
authentication DN.
facility described in
{{SECT:Mapping Authentication identities to LDAP entries}}
can be applied to these DNs as well.
+
+H2: TLS Configuration
+
+After obtaining the required certificates, a
+number of options must be configured on both the client
+and the server to enable TLS and make use of the certificates.
+At a minimum, the clients must be configured with the filename
+containing all of the {{TERM[expand]CA}} (CA) certificates it
+will trust. The server must be configured with the {{TERM:CA}}
+certificates and also its own server certificate and private key.
+
+Typically a single CA will have issued the server certificate
+and all of the trusted client certificates, so the server only
+needs to trust that one signing CA. However, a client may wish
+to connect to a variety of secure servers managed by different
+organizations, with server certificates generated by many
+different CAs. As such, a client is likely to need a list of
+many different trusted CAs in its configuration.
+
+H3: Server Configuration
+
+The configuration directives for slapd belong in the global directives
+section of {{slapd.conf}}(5).
+
+H4: TLSCACertificateFile <filename>
+
+This directive specifies the {{TERM:PEM}}-format file containing
+certificates for the CA's that slapd will trust. The certificate for
+the CA that signed the server certificate must be included among
+these certificates. If the signing CA was not a top-level (root) CA,
+certificates for the entire sequence of CA's from the signing CA to
+the top-level CA should be present. Multiple certificates are simply
+appended to the file; the order is not significant.
+
+H4: TLSCACertificatePath <path>
+
+This directive specifies the path of a directory that contains
+individual {{TERM:CA}} certificates in separate files. In addition,
+this directory must be specially managed using the OpenSSL {{c_rehash}}
+utility. When using this feature, the OpenSSL library will attempt to
+locate certificate files based on a hash of their name and serial number.
+The {{c_rehash}} utility is used to generate symbolic links with the
+hashed names that point to the actual certificate files. As such,
+this option can only be used with a filesystem that actually supports
+symbolic links. In general, it is simpler to use the
+{{EX:TLSCACertificateFile}} directive instead.
+
+H4: TLSCertificateFile <filename>
+
+This directive specifies the file that contains the slapd server
+certificate. Certificates are generally public information and
+require no special protection.
+
+H4: TLSCertificateKeyFile <filename>
+
+This directive specifies the file that contains the private key
+that matches the certificate stored in the {{EX:TLSCertificateFile}}
+file. Private keys themselves are sensitive data and are usually
+password encrypted for protection. However, the current implementation
+doesn't support encrypted keys so the key must not be encrypted
+and the file itself must be protected carefully.
+
+H4: TLSCipherSuite <cipher-suite-spec>
+
+This directive configures what ciphers will be accepted and the
+preference order. {{EX:<cipher-suite-spec>}} should be a cipher
+specification for OpenSSL. You can use the command
+
+> openssl ciphers -v ALL
+
+to obtain a verbose list of available cipher specifications.
+Besides the individual cipher names, the specifiers {{EX:HIGH}},
+{{EX:MEDIUM}}, {{EX:LOW}}, {{EX:EXPORT}}, and {{EX:EXPORT40}}
+may be helpful, along with {{EX:TLSv1}}, {{EX:SSLv3}},
+and {{EX:SSLv2}}.
+
+H4: TLSRandFile <filename>
+
+This directive specifies the file to obtain random bits from when
+{{EX:/dev/urandom}} is not available. If the
+system provides {{EX:/dev/urandom}} then this option is not needed,
+otherwise a source of random data must be configured.
+Some systems (e.g. Linux)
+provide {{EX:/dev/urandom}} by default, while others (e.g. Solaris)
+require the installation of a patch to provide it, and others may
+not support it at all. In the latter case, EGD or PRNGD should be
+installed, and this directive should specify the name of the EGD/PRNGD
+socket. The environment variable {{EX:RANDFILE}} can also be used to specify
+the filename. Also, in the absence of these options, the {{EX:.rnd}}
+file in the slapd user's home directory may be used if it exists. To
+use the {{EX:.rnd}} file, just create the file and copy a few hundred
+bytes of arbitrary data into the file. The file is only used to
+provide a seed for the pseudo-random number generator, and it doesn't
+need very much data to work.
+
+H4: TLSVerifyClient { never | allow | try | demand }
+
+This directive specifies what checks to perform on client certificates
+in an incoming TLS session, if any. This option is set to {{EX:never}}
+by default, in which case the server never asks the client for a
+certificate. With a setting of {{EX:allow}} the server will ask
+for a client certificate; if none is provided the session proceeds
+normally. If a certificate is provided but the server is unable to
+verify it, the certificate is ignored and the session proceeds
+normally, as if no certificate had been provided. With a setting of
+{{EX:try}} the certificate is requested, and if none is provided,
+the session proceeds normally. If a certificate is provided and it
+cannot be verified, the session is immediately terminated. With a
+setting of {{EX:demand}} the certificate is requested and a valid
+certificate must be provided, otherwise the session is immediately
+terminated.
+
+Note: The server must request a client certificate in order to
+use the SASL EXTERNAL authentication mechanism with a TLS session.
+As such, a non-default {{EX:TLSVerifyClient}} setting must be configured
+before SASL EXTERNAL authentication may be attempted, and the
+SASL EXTERNAL mechanism will only be offered to the client if a valid
+client certificate was received.
+
+H3: Client Configuration
+
+Most of the client configuration directives parallel the server
+directives. The names of the directives are different, and they go
+into {{ldap.conf}}(5) instead of {{slapd.conf}}(5), but their
+functionality is mostly the same. Also, while most of these options may
+be configured on a system-wide basis, they may all be overridden by
+individual users in their {{.ldaprc}} files.
+
+H4: TLS_CACERT <filename>
+
+This is equivalent to the server's {{EX:TLSCACertificateFile}} option. As
+noted in the {{SECT:TLS Configuration}} section, a client typically
+may need to know about more CAs than a server, but otherwise the
+same considerations apply.
+
+H4: TLS_CACERTDIR <path>
+
+This is equivalent to the server's {{EX:TLSCACertificatePath}} option. The
+specified directory must be managed with the OpenSSL {{c_rehash}}
+utility as well.
+
+H4: TLS_CERT <filename>
+
+This directive specifies the file that contains the client certificate.
+This is a user-only directive and can only be specified in a user's
+{{.ldaprc}} file.
+
+H4: TLS_KEY <filename>
+
+This directive specifies the file that contains the private key
+that matches the certificate stored in the {{EX:TLS_CERT}}
+file. The same constraints mentioned for {{EX:TLSCertificateKeyFile}}
+apply here. This is also user-only directive.
+
+H4: TLS_RANDFILE <filename>
+
+This directive is the same as the server's {{EX:TLSRandFile}}
+option.
+
+H4: TLS_REQCERT { never | allow | try | demand }
+
+This directive is equivalent to the server's {{EX:TLSVerifyClient}}
+option. However, for clients the default value is {{EX:demand}}
+and there generally is no good reason to change this setting.
+
+H4: TLS { never | hard }
+
+This directive specifies whether client connections should use TLS
+by default. The default setting is {{EX:never}} which specifies that
+connections will be opened in the clear unless TLS is explicitly
+specified using an "ldaps://" URL. When set to {{EX:hard}} all
+connections will be established with TLS, as if an "ldaps://" URL
+was specified. Note that the use of ldaps is a holdover from LDAPv2
+and this setting is incompatible with the LDAPv3 StartTLS request.
+As such, it's best not to use this option.
projects / openldap / commitdiff