certmap: add new library libsss_certmap

With this library it would be possible to map certificates and users not
only by adding the full certificate to the user's LDAP object but by
adding e.g. only parts like the issuer and subject name. Additionally
the library is also able to flexible select/match certificates based on
values in the certificate.

Details about mapping and matching rules can be found in the included
man page.

Related to https://pagure.io/SSSD/sssd/issue/3050

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>

1 files changed, 600 insertions, 0 deletions

diff --git a/src/man/sss-certmap.5.xml b/src/man/sss-certmap.5.xml
new file mode 100644
index 000000000..bbe68509f
--- /dev/null
+++ b/src/man/sss-certmap.5.xml
@@ -0,0 +1,600 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE reference PUBLIC "-//OASIS//DTD DocBook V4.4//EN"
+"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
+<reference>
+<title>SSSD Manual pages</title>
+<refentry>
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/upstream.xml" />
+
+    <refmeta>
+        <refentrytitle>sss-certmap</refentrytitle>
+        <manvolnum>5</manvolnum>
+        <refmiscinfo class="manual">File Formats and Conventions</refmiscinfo>
+    </refmeta>
+
+    <refnamediv id='name'>
+        <refname>sss-certmap</refname>
+        <refpurpose>SSSD Certificate Matching and Mapping Rules</refpurpose>
+    </refnamediv>
+
+    <refsect1 id='description'>
+        <title>DESCRIPTION</title>
+        <para>
+            The manual page describes the rules which can be used by SSSD and
+            other components to match X.509 certificates and map them to
+            accounts.
+        </para>
+        <para>
+            Each rule has four components, a <quote>priority</quote>, a
+            <quote>matching rule</quote>, a <quote>mapping rule</quote> and a
+            <quote>domain list</quote>. All components are optional. A missing
+            <quote>priority</quote> will add the rule with the lowest priority.
+            The default <quote>matching rule</quote> will match certificates with
+            the digitalSignature key usage and clientAuth extended key usage. If
+            the <quote>mapping rule</quote> is empty the certificates will be
+            searched in the userCertificate attribute as DER encoded binary. If
+            no domains are given only the local domain will be searched.
+        </para>
+    </refsect1>
+
+    <refsect1 id='components'>
+        <title>RULE COMPONENTS</title>
+    <refsect2 id='priority'>
+        <title>PRIORITY</title>
+        <para>
+            The rules are process by priority while the number '0' (zero)
+            indicates the highest priority. The higher the number the lower is
+            the priority. A missing value indicates the lowest priority.
+        </para>
+        <para>
+            Internally the priority is treated as unsigned 32bit integer, using
+            a priority value larger than 4294967295 will cause an error.
+        </para>
+    </refsect2>
+    <refsect2 id='match'>
+        <title>MATCHING RULE</title>
+        <para>
+            The matching rule is used to select a certificate to which the
+            mapping rule should be applied. It uses a system similar to the one
+            used by <quote>pkinit_cert_match</quote> option of MIT Kerberos. It
+            consists of a keyword enclosed by '&lt;' and '&gt;' which identified
+            a certain part of the certificate and a pattern which should be
+            found for the rule to match. Multiple keyword pattern pairs can be
+            either joined with '&amp;&amp;' (and) or '&#124;&#124;' (or).
+        </para>
+        <para>
+            The available options are:
+            <variablelist>
+                <varlistentry>
+                    <term>&lt;SUBJECT&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        With this a part or the whole subject name of the
+                        certificate can be matched. For the matching POSIX
+                        Extended Regular Expression syntax is used, see regex(7)
+                        for details.
+                    </para>
+                    <para>
+                        For the matching the subject name stored in the
+                        certificate in DER encoded ASN.1 is converted into a
+                        string according to RFC 4514. This means the most
+                        specific name component comes first. Please note that
+                        not all possible attribute names are covered by RFC
+                        4514. The names included are 'CN', 'L', 'ST', 'O',
+                        'OU', 'C', 'STREET', 'DC' and 'UID'. Other attribute
+                        names might be shown differently on different platform
+                        and by different tools. To avoid confusion those
+                        attribute names are best not used or covered by a
+                        suitable regular-expression.
+                    </para>
+                    <para>
+                        Example: &lt;SUBJECT&gt;.*,DC=MY,DC=DOMAIN
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;ISSUER&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        With this a part or the whole issuer name of the
+                        certificate can be matched. All comments for
+                        &lt;SUBJECT&gt; apply her as well.
+                    </para>
+                    <para>
+                        Example: &lt;ISSUER&gt;^CN=My-CA,DC=MY,DC=DOMAIN$
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;KU&gt;key-usage</term>
+                    <listitem>
+                    <para>
+                        This option can be used to specify which key usage
+                        values the certificate should have. The following value
+                        can be used in a comma separate list:
+                        <itemizedlist>
+                            <listitem><para>digitalSignature</para></listitem>
+                            <listitem><para>nonRepudiation</para></listitem>
+                            <listitem><para>keyEncipherment</para></listitem>
+                            <listitem><para>dataEncipherment</para></listitem>
+                            <listitem><para>keyAgreement</para></listitem>
+                            <listitem><para>keyCertSign</para></listitem>
+                            <listitem><para>cRLSign</para></listitem>
+                            <listitem><para>encipherOnly</para></listitem>
+                            <listitem><para>decipherOnly</para></listitem>
+                        </itemizedlist>
+                    </para>
+                    <para>
+                        A numerical value in the range of a 32bit unsigned
+                        integer can be used as well to cover special use cases.
+                    </para>
+                    <para>
+                        Example: &lt;KU&gt;digitalSignature,keyEncipherment
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;EKU&gt;extended-key-usage</term>
+                    <listitem>
+                    <para>
+                        This option can be used to specify which extended key
+                        usage the certificate should have. The following value
+                        can be used in a comma separated list:
+                        <itemizedlist>
+                            <listitem><para>serverAuth</para></listitem>
+                            <listitem><para>clientAuth</para></listitem>
+                            <listitem><para>codeSigning</para></listitem>
+                            <listitem><para>emailProtection</para></listitem>
+                            <listitem><para>timeStamping</para></listitem>
+                            <listitem><para>OCSPSigning</para></listitem>
+                            <listitem><para>KPClientAuth</para></listitem>
+                            <listitem><para>pkinit</para></listitem>
+                            <listitem><para>msScLogin</para></listitem>
+                        </itemizedlist>
+                    </para>
+                    <para>
+                        Extended key usages which are not listed above can be
+                        specified with their OID in dotted-decimal notation.
+                    </para>
+                    <para>
+                        Example: &lt;EKU&gt;clientAuth,1.3.6.1.5.2.3.4
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        To be compatible with the usage of MIT Kerberos this
+                        option will match the Kerberos principals in the PKINIT
+                        or AD NT Principal SAN as &lt;SAN:Principal&gt; does.
+                    </para>
+                    <para>
+                        Example: &lt;SAN&gt;.*@MY\.REALM
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:Principal&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the Kerberos principals in the PKINIT or AD NT
+                        Principal SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:Principal&gt;.*@MY\.REALM
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:ntPrincipalName&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the Kerberos principals from the AD NT Principal
+                        SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:ntPrincipalName&gt;.*@MY.AD.REALM
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:pkinit&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the Kerberos principals from the PKINIT SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:ntPrincipalName&gt;.*@MY\.PKINIT\.REALM
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:dotted-decimal-oid&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Take the value of the otherName SAN component given by
+                        the OID in dotted-decimal notation, interpret it as
+                        string and try to match it against the regular
+                        expression.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:1.2.3.4&gt;test
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:otherName&gt;base64-string</term>
+                    <listitem>
+                    <para>
+                        Do a binary match with the base64 encoded blob against
+                        all otherName SAN components. With this option it is
+                        possible to match against custom otherName components
+                        with special encodings which could not be treated as
+                        strings.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:otherName&gt;MTIz
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:rfc822Name&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the rfc822Name SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:rfc822Name&gt;.*@email\.domain
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:dNSName&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the dNSName SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:dNSName&gt;.*\.my\.dns\.domain
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:x400Address&gt;base64-string</term>
+                    <listitem>
+                    <para>
+                        Binary match the value of the x400Address SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:x400Address&gt;MTIz
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:directoryName&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the directoryName SAN. The same
+                        comments as given for &lt;ISSUER&gt; and &lt;SUBJECT&gt;
+                        apply here as well.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:directoryName&gt;.*,DC=com
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:ediPartyName&gt;base64-string</term>
+                    <listitem>
+                    <para>
+                        Binary match the value of the ediPartyName SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:ediPartyName&gt;MTIz
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:uniformResourceIdentifier&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the uniformResourceIdentifier SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:uniformResourceIdentifier&gt;URN:.*
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:iPAddress&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the iPAddress SAN.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:iPAddress&gt;192\.168\..*
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>&lt;SAN:registeredID&gt;regular-expression</term>
+                    <listitem>
+                    <para>
+                        Match the value of the registeredID SAN as
+                        dotted-decimal string.
+                    </para>
+                    <para>
+                        Example: &lt;SAN:registeredID&gt;1\.2\.3\..*
+                    </para>
+                    </listitem>
+                </varlistentry>
+            </variablelist>
+        </para>
+    </refsect2>
+    <refsect2 id='map'>
+        <title>MAPPING RULE</title>
+        <para>
+            The mapping rule is used to associate a certificate with one or more
+            accounts. A Smartcard with the certificate and the matching private
+            key can then be used to authenticate as one of those accounts.
+        </para>
+        <para>
+            Currently SSSD basically only supports LDAP to lookup user
+            information (the exception is the proxy provider which is not of
+            relevance here). Because of this the mapping rule is based on LDAP
+            search filter syntax with templates to add certificate content to
+            the filter. It is expected that the filter will only contain the
+            specific data needed for the mapping an that the caller will embed
+            it in another filter to do the actual search. Because of this the
+            filter string should start and stop with '(' and ')' respectively.
+        </para>
+        <para>
+            In general it is recommended to use attributes from the certificate
+            and add them to special attributes to the LDAP user object. E.g. the
+            'altSecurityIdentities' attribute in AD or the 'ipaCertMapData'
+            attribute for IPA can be used.
+        </para>
+        <para>
+            This should be preferred to read user specific data from the
+            certificate like e.g. an email address and search for it in the LDAP
+            server. The reason is that the user specific data in LDAP might
+            change for various reasons would would break the mapping. On the
+            other hand it would be hard to break the mapping on purpose for a
+            specific user.
+        </para>
+        <para>
+            The templates to add certificate data to the search filter are based
+            on Python-style formatting strings. They consists of a keyword in
+            curly braces with an optional sub-component specifier separated by a
+            '.' or an optional conversion/formatting option separated by a '!'.
+            Allowed values are:
+            <variablelist>
+                <varlistentry>
+                    <term>{issuer_dn[!((ad|ad_x500)|ad_ldap|nss_x500|(nss|nss_ldap))]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the full issuer DN converted to a
+                        string according to RFC 4514. If X.500 ordering (most
+                        specific RDN comes last) an option with the '_x500'
+                        prefix should be used.
+                    </para>
+                    <para>
+                        The conversion options starting with 'ad_' will use
+                        attribute names as used by AD, e.g. 'S' instead of 'ST'.
+                    </para>
+                    <para>
+                        The conversion options starting with 'nss_' will use
+                        attribute names as used by NSS.
+                    </para>
+                    <para>
+                        The default conversion option is 'nss', i.e. attribute
+                        names according to NSS and LDAP/RFC 4514 ordering.
+                    </para>
+                    <para>
+                        Example: (ipacertmapdata=X509:&lt;I&gt;{issuer_dn!ad}&lt;S&gt;{subject_dn!ad})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_dn[!((ad|ad_x500)|ad_ldap|nss_x500|(nss|nss_ldap))]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the full subject DN converted to
+                        string according to RFC 4514. If X.500 ordering (most
+                        specific RDN comes last) an option with the '_x500'
+                        prefix should be used.
+                    </para>
+                    <para>
+                        The conversion options starting with 'ad_' will use
+                        attribute names as used by AD, e.g. 'S' instead of 'ST'.
+                    </para>
+                    <para>
+                        The conversion options starting with 'nss_' will use
+                        attribute names as used by NSS.
+                    </para>
+                    <para>
+                        The default conversion option is 'nss', i.e. attribute
+                        names according to NSS and LDAP/RFC 4514 ordering.
+                    </para>
+                    <para>
+                        Example: (ipacertmapdata=X509:&lt;I&gt;{issuer_dn!nss_x500}&lt;S&gt;{subject_dn!nss_x500})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{cert[!(bin|base64)]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the whole DER encoded certificate
+                        as a string to the search filter. Depending on the
+                        conversion option the binary certificate is either
+                        converted to an escaped hex sequence '\xx' or base64.
+                        The escaped hex sequence is the default and can e.g. be
+                        used with the LDAP attribute 'userCertificate;binary'.
+                    </para>
+                    <para>
+                        Example: (userCertificate;binary={cert!bin})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_principal[.short_name]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the Kerberos principal which is
+                        taken either from the SAN used by pkinit or the one used
+                        by AD. The 'short_name' component represent the first
+                        part of the principal before the '@' sign.
+                    </para>
+                    <para>
+                        Example: (|(userPrincipal={subject_principal})(samAccountName={subject_principal.short_name}))
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_pkinit_principal[.short_name]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the Kerberos principal which is
+                        given by then SAN used by pkinit. The 'short_name'
+                        component represent the first part of the principal
+                        before the '@' sign.
+                    </para>
+                    <para>
+                        Example: (|(userPrincipal={subject_pkinit_principal})(uid={subject_pkinit_principal.short_name}))
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_nt_principal[.short_name]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the Kerberos principal which is
+                        given by then SAN used by AD. The 'short_name' component
+                        represent the first part of the principal before the '@'
+                        sign.
+                    </para>
+                    <para>
+                        Example: (|(userPrincipal={subject_principal})(samAccountName={subject_principal.short_name}))
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_rfc822_name[.short_name]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the string which is stored in the
+                        rfc822Name component of the SAN, typically an email
+                        address. The 'short_name' component represent the first
+                        part of the address before the '@' sign.
+                    </para>
+                    <para>
+                        Example: (|(mail={subject_rfc822_name})(uid={subject_rfc822_name.short_name}))
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_dns_name[.short_name]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the string which is stored in the
+                        dNSName component of the SAN, typically a fully-qualified host name.
+                        The 'short_name' component represent the first
+                        part of the name before the first '.' sign.
+                    </para>
+                    <para>
+                        Example: (|(fqdn={subject_dns_name})(host={subject_dns_name.short_name}))
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_uri}</term>
+                    <listitem>
+                    <para>
+                        This template will add the string which is stored in the
+                        uniformResourceIdentifier component of the SAN.
+                    </para>
+                    <para>
+                        Example: (uri={subject_uri})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_ip_address}</term>
+                    <listitem>
+                    <para>
+                        This template will add the string which is stored in the
+                        iPAddress component of the SAN.
+                    </para>
+                    <para>
+                        Example: (ip={subject_ip_address})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_x400_address}</term>
+                    <listitem>
+                    <para>
+                        This template will add the value which is stored in the
+                        x400Address component of the SAN as escaped hex
+                        sequence.
+                    </para>
+                    <para>
+                        Example: (attr:binary={subject_x400_address})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_directory_name[!((ad|ad_x500)|ad_ldap|nss_x500|(nss|nss_ldap))]}</term>
+                    <listitem>
+                    <para>
+                        This template will add the DN string of the value which
+                        is stored in the directoryName component of the SAN.
+                    </para>
+                    <para>
+                        Example: (orig_dn={subject_directory_name})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_ediparty_name}</term>
+                    <listitem>
+                    <para>
+                        This template will add the value which is stored in the
+                        ediPartyName component of the SAN as escaped hex
+                        sequence.
+                    </para>
+                    <para>
+                        Example: (attr:binary={subject_ediparty_name})
+                    </para>
+                    </listitem>
+                </varlistentry>
+                <varlistentry>
+                    <term>{subject_registered_id}</term>
+                    <listitem>
+                    <para>
+                        This template will add the OID which is stored in the
+                        registeredID component of the SAN as as dotted-decimal
+                        string.
+                    </para>
+                    <para>
+                        Example: (oid={subject_registered_id})
+                    </para>
+                    </listitem>
+                </varlistentry>
+            </variablelist>
+        </para>
+    </refsect2>
+    <refsect2 id='domains'>
+        <title>DOMAIN LIST</title>
+        <para>
+            If the domain list is not empty users mapped to a given certificate
+            are not only searched in the local domain but in the listed domains
+            as well as long as they are know by SSSD. Domains not know to SSSD
+            will be ignored.
+        </para>
+    </refsect2>
+    </refsect1>
+</refentry>
+</reference>