Add regexp authorization policy for IMSI

* extend "auth policy" vty command with new option "regexp"
* add vty command "authorized-regexp" for setting arbitrary POSIX
  regular expression
* add basic vty test
* add optional "regexp" argument to subscriber-create-on-demand vty
  command

With those in place we can now set the regexp against which MS's IMSI
will be matched.

If IMSI match the regexp than MS is allowed to access the network. If
subscriber is already marked as authorized in HLR than it'll be allowed
regardless of IMSI matching.

The same way we can decide whether to create subscribers on-demand
basesd on IMSI regexp match. Similar to authorization this restriction
can be overridden by manually creating subscriber via vty, ctrl
interface or directly in HLR.

Change-Id: I525f4b80676de47d1d422686da2ca012301b0129
Fixes: OS#1647

2 files changed, 39 insertions, 7 deletions

diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index 74da34b19..92c4cfe0e 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -25,9 +25,12 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdbool.h>
 #include <errno.h>
 #include <time.h>
 #include <netinet/in.h>
+#include <regex.h>
+#include <sys/types.h>
 
 #include "bscconfig.h"
 
@@ -244,6 +247,17 @@ int gsm48_secure_channel(struct gsm_subscriber_connection *conn, int key_seq,
 	return -EINVAL; /* not reached */
 }
 
+static bool subscr_regexp_check(const struct gsm_network *net, const char *imsi)
+{
+	if (!net->authorized_reg_str)
+		return false;
+
+	if (regexec(&net->authorized_regexp, imsi, 0, NULL, 0) != REG_NOMATCH)
+		return true;
+
+	return false;
+}
+
 static int authorize_subscriber(struct gsm_loc_updating_operation *loc,
 				struct gsm_subscriber *subscriber)
 {
@@ -261,6 +275,13 @@ static int authorize_subscriber(struct gsm_loc_updating_operation *loc,
 	switch (subscriber->group->net->auth_policy) {
 	case GSM_AUTH_POLICY_CLOSED:
 		return subscriber->authorized;
+	case GSM_AUTH_POLICY_REGEXP:
+		if (subscriber->authorized)
+			return 1;
+		if (subscr_regexp_check(subscriber->group->net,
+					subscriber->imsi))
+			subscriber->authorized = 1;
+		return subscriber->authorized;
 	case GSM_AUTH_POLICY_TOKEN:
 		if (subscriber->authorized)
 			return subscriber->authorized;
@@ -509,10 +530,14 @@ static int mm_tx_identity_req(struct gsm_subscriber_connection *conn, uint8_t id
 static struct gsm_subscriber *subscr_create(const struct gsm_network *net,
 					    const char *imsi)
 {
-	if (net->subscr_creation_mode != GSM_SUBSCR_DONT_CREATE)
-		return subscr_create_subscriber(net->subscr_group, imsi);
+	if (net->subscr_creation_mode == GSM_SUBSCR_DONT_CREATE)
+		return NULL;
+
+	if (net->subscr_creation_mode & GSM_SUBSCR_CREAT_W_REGEXP)
+		if (!subscr_regexp_check(net, imsi))
+			return NULL;
 
-	return NULL;
+	return subscr_create_subscriber(net->subscr_group, imsi);
 }
 
 /* Parse Chapter 9.2.11 Identity Response */
diff --git a/openbsc/src/libmsc/vty_interface_layer3.c b/openbsc/src/libmsc/vty_interface_layer3.c
index 5d74e04fa..3f67b9aa8 100644
--- a/openbsc/src/libmsc/vty_interface_layer3.c
+++ b/openbsc/src/libmsc/vty_interface_layer3.c
@@ -1032,11 +1032,15 @@ DEFUN(cfg_nitb, cfg_nitb_cmd,
 }
 
 DEFUN(cfg_nitb_subscr_create, cfg_nitb_subscr_create_cmd,
-      "subscriber-create-on-demand",
-      "Make a new record when a subscriber is first seen.\n")
+      "subscriber-create-on-demand [regexp]",
+      "Make a new record when a subscriber is first seen.\n"
+      "Create subscribers only if IMSI matches the regexp specified in "
+      "authorized-regexp command\n")
 {
 	struct gsm_network *gsmnet = gsmnet_from_vty(vty);
 	gsmnet->subscr_creation_mode = GSM_SUBSCR_CREAT_W_RAND_EXT;
+	if (argc)
+		gsmnet->subscr_creation_mode |= GSM_SUBSCR_CREAT_W_REGEXP;
 	return CMD_SUCCESS;
 }
 
@@ -1070,9 +1074,12 @@ DEFUN(cfg_nitb_no_assign_tmsi, cfg_nitb_no_assign_tmsi_cmd,
 static int config_write_nitb(struct vty *vty)
 {
 	struct gsm_network *gsmnet = gsmnet_from_vty(vty);
+	enum gsm_subscr_creation_mode scm = gsmnet->subscr_creation_mode;
+	const char *reg = (scm & GSM_SUBSCR_CREAT_W_REGEXP) ? " regexp" : "",
+		*pref = scm ? "" : "no ";
 	vty_out(vty, "nitb%s", VTY_NEWLINE);
-	vty_out(vty, " %ssubscriber-create-on-demand%s",
-		gsmnet->subscr_creation_mode ? "" : "no ", VTY_NEWLINE);
+	vty_out(vty, " %ssubscriber-create-on-demand%s%s",
+		pref, reg, VTY_NEWLINE);
 	vty_out(vty, " %sassign-tmsi%s",
 		gsmnet->avoid_tmsi ? "no " : "", VTY_NEWLINE);
 	return CMD_SUCCESS;