NEGCACHE: initialize UPN negative cache as well

UPNs are handled separately in the negative cache. To properly filter
user names even in the case of the fallback to a UPN lookup the negative
cahe for UPNs has to be initialized with the names from the filter_user
option as well.

If the name from the option is a short name it will be added to the
negative UPN cache for each domain with the respective domain name. If
the name from the option is fully-qualified it will be added as is to
the negative UPN cache for each domain.

Related to https://pagure.io/SSSD/sssd/issue/3978

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

src/man/sssd.conf.5.xml

@@ -849,7 +849,8 @@
                             from the sss NSS database. This is particularly
                             useful for system accounts. This option can also
                             be set per-domain or include fully-qualified names
-                            to filter only users from the particular domain.
+                            to filter only users from the particular domain or
+                            by a user principal name (UPN).
                         </para>
                         <para>
                             NOTE: The filter_groups option doesn't affect

src/responder/common/negcache.c

@@ -974,10 +974,16 @@ errno_t sss_ncache_prepopulate(struct sss_nc_ctx *ncache,
             }
 
             if (domainname && strcmp(domainname, dom->name)) {
-                DEBUG(SSSDBG_CRIT_FAILURE,
+                DEBUG(SSSDBG_TRACE_FUNC,
                       "Mismatch between domain name (%s) and name "
-                          "set in FQN  (%s), skipping user %s\n",
-                          dom->name, domainname, name);
+                          "set in FQN  (%s), assuming %s is UPN\n",
+                          dom->name, domainname, filter_list[i]);
+                ret = sss_ncache_set_upn(ncache, true, dom, filter_list[i]);
+                if (ret != EOK) {
+                    DEBUG(SSSDBG_OP_FAILURE,
+                          "sss_ncache_set_upn failed (%d [%s]), ignored\n",
+                          ret, sss_strerror(ret));
+                }
                 continue;
             }
 
@@ -986,13 +992,19 @@ errno_t sss_ncache_prepopulate(struct sss_nc_ctx *ncache,
                 continue;
             }
 
+            ret = sss_ncache_set_upn(ncache, true, dom, fqname);
+            if (ret != EOK) {
+                DEBUG(SSSDBG_OP_FAILURE,
+                      "sss_ncache_set_upn failed (%d [%s]), ignored\n",
+                      ret, sss_strerror(ret));
+            }
             ret = sss_ncache_set_user(ncache, true, dom, fqname);
             talloc_zfree(fqname);
             if (ret != EOK) {
                 DEBUG(SSSDBG_CRIT_FAILURE,
                       "Failed to store permanent user filter for [%s]"
                           " (%d [%s])\n", filter_list[i],
-                          ret, strerror(ret));
+                          ret, sss_strerror(ret));
                 continue;
             }
         }
@@ -1023,7 +1035,18 @@ errno_t sss_ncache_prepopulate(struct sss_nc_ctx *ncache,
             dom = responder_get_domain(rctx, domainname);
             if (!dom) {
                 DEBUG(SSSDBG_CRIT_FAILURE,
-                      "Invalid domain name [%s]\n", domainname);
+                      "Unknown domain name [%s], assuming [%s] is UPN\n",
+                      domainname, filter_list[i]);
+                for (dom = domain_list;
+                     dom != NULL;
+                     dom = get_next_domain(dom, SSS_GND_ALL_DOMAINS)) {
+                    ret = sss_ncache_set_upn(ncache, true, dom, filter_list[i]);
+                    if (ret != EOK) {
+                        DEBUG(SSSDBG_OP_FAILURE,
+                              "sss_ncache_set_upn failed (%d [%s]), ignored\n",
+                              ret, sss_strerror(ret));
+                    }
+                }
                 continue;
             }
 
@@ -1050,6 +1073,15 @@ errno_t sss_ncache_prepopulate(struct sss_nc_ctx *ncache,
                     continue;
                 }
 
+                ret = sss_ncache_set_upn(ncache, true, dom, fqname);
+                if (ret != EOK) {
+                   DEBUG(SSSDBG_CRIT_FAILURE,
+                         "Failed to store permanent upn filter for"
+                             " [%s:%s] (%d [%s])\n",
+                             dom->name, filter_list[i],
+                             ret, strerror(ret));
+                }
+
                 ret = sss_ncache_set_user(ncache, true, dom, fqname);
                 talloc_zfree(fqname);
                 if (ret != EOK) {