Allow usage of enterprise principals

Enterprise principals are currently most useful for the AD provider and
hence enabled here by default while for the other Kerberos based
authentication providers they are disabled by default.

If additional UPN suffixes are configured for the AD domain the user
principal stored in the AD LDAP server might not contain the real
Kerberos realm of the AD domain but one of the additional suffixes which
might be completely randomly chooses, e.g. are not related to any
existing DNS domain. This make it hard for a client to figure out the
right KDC to send requests to.

To get around this enterprise principals (see
http://tools.ietf.org/html/rfc6806 for details) were introduced.
Basically a default realm is added to the principal so that the Kerberos
client libraries at least know where to send the request to. It is not
in the responsibility of the KDC to either handle the request itself,
return a client referral if he thinks a different KDC can handle the
request or return and error. This feature is also use to allow
authentication in AD environments with cross forest trusts.

Fixes https://fedorahosted.org/sssd/ticket/1842

16 files changed, 93 insertions, 7 deletions

diff --git a/src/config/SSSDConfig/__init__.py.in b/src/config/SSSDConfig/__init__.py.in
index 1f997f23..f603a218 100644
--- a/src/config/SSSDConfig/__init__.py.in
+++ b/src/config/SSSDConfig/__init__.py.in
@@ -169,6 +169,7 @@ option_strings = {
     'krb5_use_fast' : _("Enables FAST"),
     'krb5_fast_principal' : _("Selects the principal to use for FAST"),
     'krb5_canonicalize' : _("Enables principal canonicalization"),
+    'krb5_use_enterprise_principal' : _("Enables enterprise principals"),
 
     # [provider/krb5/chpass]
     'krb5_kpasswd' : _('Server where the change password service is running if not on the KDC'),
diff --git a/src/config/SSSDConfigTest.py b/src/config/SSSDConfigTest.py
index 8f003f55..6ae458b1 100755
--- a/src/config/SSSDConfigTest.py
+++ b/src/config/SSSDConfigTest.py
@@ -603,7 +603,8 @@ class SSSDConfigTestSSSDDomain(unittest.TestCase):
              'krb5_renew_interval',
              'krb5_use_fast',
              'krb5_fast_principal',
-             'krb5_canonicalize'])
+             'krb5_canonicalize',
+             'krb5_use_enterprise_principal'])
 
         options = domain.list_options()
 
@@ -761,7 +762,8 @@ class SSSDConfigTestSSSDDomain(unittest.TestCase):
             'krb5_renew_interval',
             'krb5_use_fast',
             'krb5_fast_principal',
-            'krb5_canonicalize']
+            'krb5_canonicalize',
+            'krb5_use_enterprise_principal']
 
         self.assertTrue(type(options) == dict,
                         "Options should be a dictionary")
@@ -945,7 +947,8 @@ class SSSDConfigTestSSSDDomain(unittest.TestCase):
              'krb5_renew_interval',
              'krb5_use_fast',
              'krb5_fast_principal',
-             'krb5_canonicalize'])
+             'krb5_canonicalize',
+             'krb5_use_enterprise_principal'])
 
         options = domain.list_options()
 
diff --git a/src/config/etc/sssd.api.d/sssd-ad.conf b/src/config/etc/sssd.api.d/sssd-ad.conf
index dbee270e..4c257173 100644
--- a/src/config/etc/sssd.api.d/sssd-ad.conf
+++ b/src/config/etc/sssd.api.d/sssd-ad.conf
@@ -118,6 +118,7 @@ krb5_lifetime = str, None, false
 krb5_renew_interval = str, None, false
 krb5_use_fast = str, None, false
 krb5_fast_principal = str, None, false
+krb5_use_enterprise_principal = bool, None, false
 
 [provider/ad/access]
 
diff --git a/src/config/etc/sssd.api.d/sssd-ipa.conf b/src/config/etc/sssd.api.d/sssd-ipa.conf
index 04855d6c..e88e32b1 100644
--- a/src/config/etc/sssd.api.d/sssd-ipa.conf
+++ b/src/config/etc/sssd.api.d/sssd-ipa.conf
@@ -140,6 +140,7 @@ krb5_lifetime = str, None, false
 krb5_renew_interval = str, None, false
 krb5_use_fast = str, None, false
 krb5_fast_principal = str, None, false
+krb5_use_enterprise_principal = bool, None, false
 
 [provider/ipa/access]
 ipa_hbac_refresh = int, None, false
diff --git a/src/config/etc/sssd.api.d/sssd-krb5.conf b/src/config/etc/sssd.api.d/sssd-krb5.conf
index 6534282f..89d16d77 100644
--- a/src/config/etc/sssd.api.d/sssd-krb5.conf
+++ b/src/config/etc/sssd.api.d/sssd-krb5.conf
@@ -19,6 +19,7 @@ krb5_renew_interval = str, None, false
 krb5_use_fast = str, None, false
 krb5_fast_principal = str, None, false
 krb5_canonicalize = bool, None, false
+krb5_use_enterprise_principal = bool, None, false
 
 [provider/krb5/access]
 
diff --git a/src/external/krb5.m4 b/src/external/krb5.m4
index 56c64842..bdbd71ba 100644
--- a/src/external/krb5.m4
+++ b/src/external/krb5.m4
@@ -51,6 +51,7 @@ AC_CHECK_FUNCS([krb5_get_init_creds_opt_alloc krb5_get_error_message \
                 krb5_get_init_creds_opt_set_fast_flags \
                 krb5_get_init_creds_opt_set_canonicalize \
                 krb5_get_init_creds_opt_set_responder \
+                krb5_parse_name_flags \
                 krb5_unparse_name_flags \
                 krb5_get_init_creds_opt_set_change_password_prompt \
                 krb5_free_keytab_entry_contents \
diff --git a/src/man/sssd-ad.5.xml b/src/man/sssd-ad.5.xml
index 6ab133d5..3b2b0bc0 100644
--- a/src/man/sssd-ad.5.xml
+++ b/src/man/sssd-ad.5.xml
@@ -129,6 +129,25 @@ ldap_id_mapping = False
                 </varlistentry>
 
                 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/override_homedir.xml" />
+
+                <varlistentry>
+                    <term>krb5_use_enterprise_principal (boolean)</term>
+                    <listitem>
+                        <para>
+                            Specifies if the user principal should be treated
+                            as enterprise principal. See section 5 of RFC 6806
+                            for more details about enterprise principals.
+                        </para>
+
+                        <para>
+                            Default: true
+                        </para>
+                        <para>
+                             Note that this default differs from the
+                             traditional Kerberos provider back end.
+                        </para>
+                    </listitem>
+                </varlistentry>
             </variablelist>
         </para>
     </refsect1>
diff --git a/src/man/sssd-krb5.5.xml b/src/man/sssd-krb5.5.xml
index 00881b8b..731d7725 100644
--- a/src/man/sssd-krb5.5.xml
+++ b/src/man/sssd-krb5.5.xml
@@ -451,6 +451,21 @@
                     </listitem>
                 </varlistentry>
 
+                <varlistentry>
+                    <term>krb5_use_enterprise_principal (boolean)</term>
+                    <listitem>
+                        <para>
+                            Specifies if the user principal should be treated
+                            as enterprise principal. See section 5 of RFC 6806
+                            for more details about enterprise principals.
+                        </para>
+
+                        <para>
+                            Default: false (AD provide: true)
+                        </para>
+                    </listitem>
+                </varlistentry>
+
             </variablelist>
         </para>
     </refsect1>
diff --git a/src/providers/ad/ad_opts.h b/src/providers/ad/ad_opts.h
index 09aee7e2..4b87e0c0 100644
--- a/src/providers/ad/ad_opts.h
+++ b/src/providers/ad/ad_opts.h
@@ -142,6 +142,7 @@ struct dp_option ad_def_krb5_opts[] = {
     { "krb5_use_fast", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_fast_principal", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_canonicalize", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
+    { "krb5_use_enterprise_principal", DP_OPT_BOOL, BOOL_TRUE, BOOL_TRUE },
     DP_OPTION_TERMINATOR
 };
 
diff --git a/src/providers/ipa/ipa_opts.h b/src/providers/ipa/ipa_opts.h
index a3d0210a..6adbdd96 100644
--- a/src/providers/ipa/ipa_opts.h
+++ b/src/providers/ipa/ipa_opts.h
@@ -264,6 +264,7 @@ struct dp_option ipa_def_krb5_opts[] = {
     { "krb5_use_fast", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_fast_principal", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_canonicalize", DP_OPT_BOOL, BOOL_TRUE, BOOL_TRUE },
+    { "krb5_use_enterprise_principal", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     DP_OPTION_TERMINATOR
 };
 
diff --git a/src/providers/krb5/krb5_child.c b/src/providers/krb5/krb5_child.c
index dd01e70b..831905af 100644
--- a/src/providers/krb5/krb5_child.c
+++ b/src/providers/krb5/krb5_child.c
@@ -54,6 +54,7 @@ struct krb5_req {
     char *keytab;
     bool validate;
     bool upn_from_different_realm;
+    bool use_enterprise_princ;
     char *fast_ccname;
 
     const char *upn;
@@ -1549,6 +1550,7 @@ static errno_t unpack_buffer(uint8_t *buf, size_t size,
     uint32_t len;
     uint32_t validate;
     uint32_t different_realm;
+    uint32_t use_enterprise_princ;
     struct pam_data *pd;
     errno_t ret;
 
@@ -1571,6 +1573,8 @@ static errno_t unpack_buffer(uint8_t *buf, size_t size,
     SAFEALIGN_COPY_UINT32_CHECK(offline, buf + p, size, &p);
     SAFEALIGN_COPY_UINT32_CHECK(&different_realm, buf + p, size, &p);
     kr->upn_from_different_realm = (different_realm == 0) ? false : true;
+    SAFEALIGN_COPY_UINT32_CHECK(&use_enterprise_princ, buf + p, size, &p);
+    kr->use_enterprise_princ = (use_enterprise_princ == 0) ? false : true;
     SAFEALIGN_COPY_UINT32_CHECK(&len, buf + p, size, &p);
     if ((p + len ) > size) return EINVAL;
     kr->upn = talloc_strndup(pd, (char *)(buf + p), len);
@@ -1578,9 +1582,11 @@ static errno_t unpack_buffer(uint8_t *buf, size_t size,
     p += len;
 
     DEBUG(SSSDBG_CONF_SETTINGS,
-          ("cmd [%d] uid [%llu] gid [%llu] validate [%s] offline [%s] "
-           "UPN [%s]\n", pd->cmd, (unsigned long long) kr->uid,
+          ("cmd [%d] uid [%llu] gid [%llu] validate [%s] "
+           "enterprise principal [%s] offline [%s] UPN [%s]\n",
+           pd->cmd, (unsigned long long) kr->uid,
            (unsigned long long) kr->gid, kr->validate ? "true" : "false",
+           kr->use_enterprise_princ ? "true" : "false",
            *offline ? "true" : "false", kr->upn ? kr->upn : "none"));
 
     if (pd->cmd == SSS_PAM_AUTHENTICATE ||
@@ -1912,6 +1918,7 @@ static int k5c_setup(struct krb5_req *kr, uint32_t offline)
     char *lifetime_str;
     char *use_fast_str;
     krb5_deltat lifetime;
+    int parse_flags;
 
     kr->realm = getenv(SSSD_KRB5_REALM);
     if (kr->realm == NULL) {
@@ -1936,7 +1943,8 @@ static int k5c_setup(struct krb5_req *kr, uint32_t offline)
         }
     }
 
-    kerr = krb5_parse_name(kr->ctx, kr->upn, &kr->princ);
+    parse_flags = kr->use_enterprise_princ ? KRB5_PRINCIPAL_PARSE_ENTERPRISE : 0;
+    kerr = sss_krb5_parse_name_flags(kr->ctx, kr->upn, parse_flags, &kr->princ);
     if (kerr != 0) {
         KRB5_CHILD_DEBUG(SSSDBG_CRIT_FAILURE, kerr);
         return kerr;
diff --git a/src/providers/krb5/krb5_child_handler.c b/src/providers/krb5/krb5_child_handler.c
index 8ff65130..0b8cd6b2 100644
--- a/src/providers/krb5/krb5_child_handler.c
+++ b/src/providers/krb5/krb5_child_handler.c
@@ -130,6 +130,7 @@ static errno_t create_send_buffer(struct krb5child_req *kr,
     const char *keytab;
     uint32_t validate;
     uint32_t different_realm;
+    uint32_t use_enterprise_principal;
     size_t username_len = 0;
     errno_t ret;
 
@@ -141,6 +142,8 @@ static errno_t create_send_buffer(struct krb5child_req *kr,
 
     validate = dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) ? 1 : 0;
     different_realm = kr->upn_from_different_realm ? 1 : 0;
+    use_enterprise_principal = dp_opt_get_bool(kr->krb5_ctx->opts,
+                                         KRB5_USE_ENTERPRISE_PRINCIPAL) ? 1 : 0;
 
     buf = talloc(kr, struct io_buffer);
     if (buf == NULL) {
@@ -148,7 +151,7 @@ static errno_t create_send_buffer(struct krb5child_req *kr,
         return ENOMEM;
     }
 
-    buf->size = 7*sizeof(uint32_t) + strlen(kr->upn);
+    buf->size = 8*sizeof(uint32_t) + strlen(kr->upn);
 
     if (kr->pd->cmd == SSS_PAM_AUTHENTICATE ||
         kr->pd->cmd == SSS_CMD_RENEW ||
@@ -182,6 +185,7 @@ static errno_t create_send_buffer(struct krb5child_req *kr,
     SAFEALIGN_COPY_UINT32(&buf->data[rp], &validate, &rp);
     SAFEALIGN_COPY_UINT32(&buf->data[rp], &kr->is_offline, &rp);
     SAFEALIGN_COPY_UINT32(&buf->data[rp], &different_realm, &rp);
+    SAFEALIGN_COPY_UINT32(&buf->data[rp], &use_enterprise_principal, &rp);
 
     SAFEALIGN_SET_UINT32(&buf->data[rp], strlen(kr->upn), &rp);
     safealign_memcpy(&buf->data[rp], kr->upn, strlen(kr->upn), &rp);
diff --git a/src/providers/krb5/krb5_common.h b/src/providers/krb5/krb5_common.h
index 13035291..85049360 100644
--- a/src/providers/krb5/krb5_common.h
+++ b/src/providers/krb5/krb5_common.h
@@ -65,6 +65,7 @@ enum krb5_opts {
     KRB5_USE_FAST,
     KRB5_FAST_PRINCIPAL,
     KRB5_CANONICALIZE,
+    KRB5_USE_ENTERPRISE_PRINCIPAL,
 
     KRB5_OPTS
 };
diff --git a/src/providers/krb5/krb5_opts.h b/src/providers/krb5/krb5_opts.h
index 8ac29532..c8e64782 100644
--- a/src/providers/krb5/krb5_opts.h
+++ b/src/providers/krb5/krb5_opts.h
@@ -43,6 +43,7 @@ struct dp_option default_krb5_opts[] = {
     { "krb5_use_fast", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_fast_principal", DP_OPT_STRING, NULL_STRING, NULL_STRING },
     { "krb5_canonicalize", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
+    { "krb5_use_enterprise_principal", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     DP_OPTION_TERMINATOR
 };
 
diff --git a/src/util/sss_krb5.c b/src/util/sss_krb5.c
index ab0344c8..674e9fcd 100644
--- a/src/util/sss_krb5.c
+++ b/src/util/sss_krb5.c
@@ -766,6 +766,25 @@ sss_krb5_component_length_quoted(const krb5_data *src, int flags)
 
 
 krb5_error_code
+sss_krb5_parse_name_flags(krb5_context context, const char *name, int flags,
+                          krb5_principal *principal)
+{
+#ifdef HAVE_KRB5_PARSE_NAME_FLAGS
+    return krb5_parse_name_flags(context, name, flags, principal);
+#else
+    if (flags != 0) {
+        DEBUG(SSSDBG_MINOR_FAILURE, ("krb5_parse_name_flags not available on " \
+                                     "this plattform, names are parsed " \
+                                     "without flags. Some features like " \
+                                     "enterprise principals might not work " \
+                                     "as expected.\n"));
+    }
+
+    return krb5_parse_name(context, name, principal);
+#endif
+}
+
+krb5_error_code
 sss_krb5_unparse_name_flags(krb5_context context, krb5_const_principal principal,
                         int flags, char **name)
 {
diff --git a/src/util/sss_krb5.h b/src/util/sss_krb5.h
index deb0cbff..5fe7178c 100644
--- a/src/util/sss_krb5.h
+++ b/src/util/sss_krb5.h
@@ -122,6 +122,15 @@ krb5_error_code KRB5_CALLCONV sss_krb5_get_init_creds_opt_set_fast_flags(
 #endif
 
 
+#ifndef HAVE_KRB5_PARSE_NAME_FLAGS
+#define KRB5_PRINCIPAL_PARSE_NO_REALM           0x1
+#define KRB5_PRINCIPAL_PARSE_REQUIRE_REALM      0x2
+#define KRB5_PRINCIPAL_PARSE_ENTERPRISE         0x4
+#endif
+krb5_error_code
+sss_krb5_parse_name_flags(krb5_context context, const char *name, int flags,
+                          krb5_principal *principal);
+
 #ifndef HAVE_KRB5_UNPARSE_NAME_FLAGS
 #define KRB5_PRINCIPAL_UNPARSE_SHORT 0x1
 #define KRB5_PRINCIPAL_UNPARSE_NO_REALM 0x2