client referral support for trusted domain principals

https://fedorahosted.org/freeipa/ticket/3559

Reviewed-By: Sumit Bose <sbose@redhat.com>

daemons/ipa-kdb/ipa_kdb.h

@@ -274,6 +274,14 @@ krb5_error_code ipadb_check_transited_realms(krb5_context kcontext,
 					     const krb5_data *tr_contents,
 					     const krb5_data *client_realm,
 					     const krb5_data *server_realm);
+/* Checks whether a principal's realm is one of trusted domains' realm or NetBIOS name
+ * and returns the realm of the matched trusted domain in 'trusted_domain'
+ * Returns 0 in case of success and KRB5_KDB_NOENTRY otherwise
+ * If DAL driver is not initialized, returns KRB5_KDB_DBNOTINITED */
+krb5_error_code ipadb_is_princ_from_trusted_realm(krb5_context kcontext,
+                                                  const char *test_realm, size_t size,
+                                                  char **trusted_realm);
+
 /* DELEGATION CHECKS */
 
 krb5_error_code ipadb_check_allowed_to_delegate(krb5_context kcontext,

daemons/ipa-kdb/ipa_kdb_mspac.c

@@ -2790,3 +2790,63 @@ krb5_error_code ipadb_check_transited_realms(krb5_context kcontext,
 	}
 	return ret;
 }
+
+/* Checks whether a principal's realm is one of trusted domains' realm or NetBIOS name
+ * and returns the realm of the matched trusted domain in 'trusted_domain'
+ * Returns 0 in case of success and KRB5_KDB_NOENTRY otherwise
+ * If DAL driver is not initialized, returns KRB5_KDB_DBNOTINITED */
+krb5_error_code ipadb_is_princ_from_trusted_realm(krb5_context kcontext,
+						  const char *test_realm, size_t size,
+						  char **trusted_realm)
+{
+	struct ipadb_context *ipactx;
+	int i, j, length;
+	const char *name;
+
+	if (test_realm == NULL || test_realm[0] == '\0') {
+		return KRB5_KDB_NOENTRY;
+	}
+
+	ipactx = ipadb_get_context(kcontext);
+	if (!ipactx || !ipactx->mspac) {
+		return KRB5_KDB_DBNOTINITED;
+	}
+
+	/* First, compare realm with ours, it would not be from a trusted realm then */
+	if (strncasecmp(test_realm, ipactx->realm, size) == 0) {
+		return KRB5_KDB_NOENTRY;
+	}
+
+	if (!ipactx->mspac || !ipactx->mspac->trusts) {
+		return KRB5_KDB_NOENTRY;
+	}
+
+	/* Iterate through list of trusts and check if input realm belongs to any of the trust */
+	for(i = 0 ; i < ipactx->mspac->num_trusts ; i++) {
+		if ((strncasecmp(test_realm,
+				 ipactx->mspac->trusts[i].domain_name,
+				 size) == 0) ||
+		    (strncasecmp(test_realm,
+				 ipactx->mspac->trusts[i].flat_name,
+				 size) == 0)) {
+			/* return the realm if caller supplied a place for it */
+			if (trusted_realm != NULL) {
+				name = (ipactx->mspac->trusts[i].parent_name != NULL) ?
+					ipactx->mspac->trusts[i].parent_name :
+					ipactx->mspac->trusts[i].domain_name;
+				length = strlen(name) + 1;
+				*trusted_realm = calloc(1, length);
+				if (*trusted_realm != NULL) {
+					for (j = 0; j < length; j++) {
+						(*trusted_realm)[j] = toupper(name[j]);
+					}
+				} else {
+					return KRB5_KDB_NOENTRY;
+				}
+			}
+			return 0;
+		}
+	}
+
+	return KRB5_KDB_NOENTRY;
+}

daemons/ipa-kdb/ipa_kdb_principals.c

@@ -1023,8 +1023,10 @@ krb5_error_code ipadb_get_principal(krb5_context kcontext,
     struct ipadb_context *ipactx;
     krb5_error_code kerr;
     char *principal = NULL;
+    char *trusted_realm = NULL;
     LDAPMessage *res = NULL;
     LDAPMessage *lentry;
+    krb5_db_entry *kentry = NULL;
     uint32_t pol;
 
     ipactx = ipadb_get_context(kcontext);
@@ -1044,6 +1046,55 @@ krb5_error_code ipadb_get_principal(krb5_context kcontext,
 
     kerr = ipadb_find_principal(kcontext, flags, res, &principal, &lentry);
     if (kerr != 0) {
+        if ((kerr == KRB5_KDB_NOENTRY) &&
+            ((flags & (KRB5_KDB_FLAG_CANONICALIZE |
+                       KRB5_KDB_FLAG_CLIENT_REFERRALS_ONLY)) != 0)) {
+
+            /* First check if we got enterprise principal which looks like
+             * username\@enterprise_realm@REALM */
+            char *realm;
+            krb5_data *upn;
+
+            upn = krb5_princ_component(kcontext, search_for,
+                                       krb5_princ_size(kcontext, search_for) - 1);
+
+            if (upn == NULL) {
+                kerr = KRB5_KDB_NOENTRY;
+                goto done;
+            }
+
+            realm = memrchr(upn->data, '@', upn->length);
+            if (realm == NULL) {
+                kerr = KRB5_KDB_NOENTRY;
+                goto done;
+            }
+
+            /* skip '@' and use part after '@' as an enterprise realm for comparison */
+            realm++;
+
+            kerr = ipadb_is_princ_from_trusted_realm(kcontext,
+                                                     realm,
+                                                     upn->length - (realm - upn->data),
+                                                     &trusted_realm);
+            if (kerr == 0) {
+                kentry = calloc(1, sizeof(krb5_db_entry));
+                if (!kentry) {
+                    kerr = ENOMEM;
+                    goto done;
+                }
+                kerr = krb5_parse_name(kcontext, principal,
+                                       &kentry->princ);
+                if (kerr != 0) {
+                    goto done;
+                }
+
+                kerr = krb5_set_principal_realm(kcontext, kentry->princ, trusted_realm);
+                if (kerr != 0) {
+                    goto done;
+                }
+                *entry = kentry;
+            }
+        }
         goto done;
     }
 
@@ -1060,6 +1111,10 @@ krb5_error_code ipadb_get_principal(krb5_context kcontext,
     }
 
 done:
+    free(trusted_realm);
+    if ((kerr != 0) && (kentry != NULL)) {
+        ipadb_free_principal(kcontext, kentry);
+    }
     ldap_msgfree(res);
     krb5_free_unparsed_name(kcontext, principal);
     return kerr;