filter: Move the gsm 04.08 filter to a common place
For customer requirements we want to be able to do
filtering on the BSC as well. The same messages need
to be scanned and the same access-lists will be looked
at. In the future we might even split traffic based
on the IMSI. Begin with moving the code to a new top
level directory and then renaming and removing the
nat dependency.
diff --git a/openbsc/src/libfilter/Makefile.am b/openbsc/src/libfilter/Makefile.am
new file mode 100644
index 0000000..e24ec5f
--- /dev/null
+++ b/openbsc/src/libfilter/Makefile.am
@@ -0,0 +1,9 @@
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)
+AM_CFLAGS=-Wall $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) \
+ $(LIBOSMOVTY_CFLAGS) $(LIBOSMOABIS_CFLAGS) $(COVERAGE_CFLAGS)
+
+noinst_LIBRARIES = libfilter.a
+
+libfilter_a_SOURCES = \
+ bsc_msg_filter.c
+
diff --git a/openbsc/src/libfilter/bsc_msg_filter.c b/openbsc/src/libfilter/bsc_msg_filter.c
new file mode 100644
index 0000000..64f6d73
--- /dev/null
+++ b/openbsc/src/libfilter/bsc_msg_filter.c
@@ -0,0 +1,443 @@
+/*
+ * Access filtering
+ */
+/*
+ * (C) 2010-2012 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2012 by On-Waves
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
+#include <openbsc/bsc_msc.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/debug.h>
+#include <openbsc/ipaccess.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/gsm/gsm0808.h>
+
+#include <osmocom/gsm/protocol/gsm_08_08.h>
+#include <osmocom/gsm/protocol/gsm_04_11.h>
+
+#include <osmocom/sccp/sccp.h>
+
+int bsc_nat_barr_find(struct rb_root *root, const char *imsi, int *cm, int *lu)
+{
+ struct bsc_nat_barr_entry *n;
+ n = rb_entry(root->rb_node, struct bsc_nat_barr_entry, node);
+
+ while (n) {
+ int rc = strcmp(imsi, n->imsi);
+ if (rc == 0) {
+ *cm = n->cm_reject_cause;
+ *lu = n->lu_reject_cause;
+ return 1;
+ }
+
+ n = rb_entry(
+ (rc < 0) ? n->node.rb_left : n->node.rb_right,
+ struct bsc_nat_barr_entry, node);
+ };
+
+ return 0;
+}
+
+static int insert_barr_node(struct bsc_nat_barr_entry *entry, struct rb_root *root)
+{
+ struct rb_node **new = &root->rb_node, *parent = NULL;
+
+ while (*new) {
+ int rc;
+ struct bsc_nat_barr_entry *this;
+ this = rb_entry(*new, struct bsc_nat_barr_entry, node);
+ parent = *new;
+
+ rc = strcmp(entry->imsi, this->imsi);
+ if (rc < 0)
+ new = &((*new)->rb_left);
+ else if (rc > 0)
+ new = &((*new)->rb_right);
+ else {
+ LOGP(DNAT, LOGL_ERROR,
+ "Duplicate entry for IMSI(%s)\n", entry->imsi);
+ talloc_free(entry);
+ return -1;
+ }
+ }
+
+ rb_link_node(&entry->node, parent, new);
+ rb_insert_color(&entry->node, root);
+ return 0;
+}
+
+int bsc_nat_barr_adapt(void *ctx, struct rb_root *root,
+ const struct osmo_config_list *list)
+{
+ struct osmo_config_entry *cfg_entry;
+ int err = 0;
+
+ /* free the old data */
+ while (!RB_EMPTY_ROOT(root)) {
+ struct rb_node *node = rb_first(root);
+ rb_erase(node, root);
+ talloc_free(node);
+ }
+
+ if (!list)
+ return 0;
+
+ /* now adapt the new list */
+ llist_for_each_entry(cfg_entry, &list->entry, list) {
+ struct bsc_nat_barr_entry *entry;
+ entry = talloc_zero(ctx, struct bsc_nat_barr_entry);
+ if (!entry) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Allocation of the barr entry failed.\n");
+ continue;
+ }
+
+ entry->imsi = talloc_strdup(entry, cfg_entry->mcc);
+ entry->cm_reject_cause = atoi(cfg_entry->mnc);
+ entry->lu_reject_cause = atoi(cfg_entry->option);
+ err |= insert_barr_node(entry, root);
+ }
+
+ return err;
+}
+
+
+static int lst_check_deny(struct bsc_nat_acc_lst *lst, const char *mi_string,
+ int *cm_cause, int *lu_cause)
+{
+ struct bsc_nat_acc_lst_entry *entry;
+
+ llist_for_each_entry(entry, &lst->fltr_list, list) {
+ if (!entry->imsi_deny)
+ continue;
+ if (regexec(&entry->imsi_deny_re, mi_string, 0, NULL, 0) == 0) {
+ *cm_cause = entry->cm_reject_cause;
+ *lu_cause = entry->lu_reject_cause;
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+/* apply white/black list */
+static int auth_imsi(struct bsc_connection *bsc, const char *imsi,
+ struct bsc_nat_reject_cause *cause)
+{
+ /*
+ * Now apply blacklist/whitelist of the BSC and the NAT.
+ * 1.) Check the global IMSI barr list
+ * 2.) Allow directly if the IMSI is allowed at the BSC
+ * 3.) Reject if the IMSI is not allowed at the BSC
+ * 4.) Reject if the IMSI not allowed at the global level.
+ * 5.) Allow directly if the IMSI is allowed at the global level
+ */
+ int cm, lu;
+ struct bsc_nat_acc_lst *nat_lst = NULL;
+ struct bsc_nat_acc_lst *bsc_lst = NULL;
+
+ /* 1. global check for barred imsis */
+ if (bsc_nat_barr_find(&bsc->nat->imsi_black_list, imsi, &cm, &lu)) {
+ cause->cm_reject_cause = cm;
+ cause->lu_reject_cause = lu;
+ LOGP(DNAT, LOGL_DEBUG,
+ "Blocking subscriber IMSI %s with CM: %d LU: %d\n",
+ imsi, cm, lu);
+ return -4;
+ }
+
+
+ bsc_lst = bsc_nat_acc_lst_find(bsc->nat, bsc->cfg->acc_lst_name);
+ nat_lst = bsc_nat_acc_lst_find(bsc->nat, bsc->nat->acc_lst_name);
+
+
+ if (bsc_lst) {
+ /* 2. BSC allow */
+ if (bsc_nat_lst_check_allow(bsc_lst, imsi) == 0)
+ return 1;
+
+ /* 3. BSC deny */
+ if (lst_check_deny(bsc_lst, imsi, &cm, &lu) == 0) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Filtering %s by imsi_deny on bsc nr: %d.\n", imsi, bsc->cfg->nr);
+ rate_ctr_inc(&bsc_lst->stats->ctr[ACC_LIST_BSC_FILTER]);
+ cause->cm_reject_cause = cm;
+ cause->lu_reject_cause = lu;
+ return -2;
+ }
+
+ }
+
+ /* 4. NAT deny */
+ if (nat_lst) {
+ if (lst_check_deny(nat_lst, imsi, &cm, &lu) == 0) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Filtering %s by nat imsi_deny on bsc nr: %d.\n", imsi, bsc->cfg->nr);
+ rate_ctr_inc(&nat_lst->stats->ctr[ACC_LIST_NAT_FILTER]);
+ cause->cm_reject_cause = cm;
+ cause->lu_reject_cause = lu;
+ return -3;
+ }
+ }
+
+ return 1;
+}
+
+static int _cr_check_loc_upd(struct bsc_connection *bsc,
+ uint8_t *data, unsigned int length,
+ char **imsi)
+{
+ uint8_t mi_type;
+ struct gsm48_loc_upd_req *lu;
+ char mi_string[GSM48_MI_SIZE];
+
+ if (length < sizeof(*lu)) {
+ LOGP(DNAT, LOGL_ERROR,
+ "LU does not fit. Length is %d \n", length);
+ return -1;
+ }
+
+ lu = (struct gsm48_loc_upd_req *) data;
+ mi_type = lu->mi[0] & GSM_MI_TYPE_MASK;
+
+ /*
+ * We can only deal with the IMSI. This will fail for a phone that
+ * will send the TMSI of a previous network to us.
+ */
+ if (mi_type != GSM_MI_TYPE_IMSI)
+ return 0;
+
+ gsm48_mi_to_string(mi_string, sizeof(mi_string), lu->mi, lu->mi_len);
+ *imsi = talloc_strdup(bsc, mi_string);
+ return 1;
+}
+
+static int _cr_check_cm_serv_req(struct bsc_connection *bsc,
+ uint8_t *data, unsigned int length,
+ int *con_type, char **imsi)
+{
+ static const uint32_t classmark_offset =
+ offsetof(struct gsm48_service_request, classmark);
+
+ char mi_string[GSM48_MI_SIZE];
+ uint8_t mi_type;
+ int rc;
+ struct gsm48_service_request *req;
+
+ /* unfortunately in Phase1 the classmark2 length is variable */
+
+ if (length < sizeof(*req)) {
+ LOGP(DNAT, LOGL_ERROR,
+ "CM Serv Req does not fit. Length is %d\n", length);
+ return -1;
+ }
+
+ req = (struct gsm48_service_request *) data;
+ if (req->cm_service_type == 0x8)
+ *con_type = NAT_CON_TYPE_SSA;
+ rc = gsm48_extract_mi((uint8_t *) &req->classmark,
+ length - classmark_offset, mi_string, &mi_type);
+ if (rc < 0) {
+ LOGP(DNAT, LOGL_ERROR, "Failed to parse the classmark2/mi. error: %d\n", rc);
+ return -1;
+ }
+
+ /* we have to let the TMSI or such pass */
+ if (mi_type != GSM_MI_TYPE_IMSI)
+ return 0;
+
+ *imsi = talloc_strdup(bsc, mi_string);
+ return 1;
+}
+
+static int _cr_check_pag_resp(struct bsc_connection *bsc,
+ uint8_t *data, unsigned int length, char **imsi)
+{
+ struct gsm48_pag_resp *resp;
+ char mi_string[GSM48_MI_SIZE];
+ uint8_t mi_type;
+
+ if (length < sizeof(*resp)) {
+ LOGP(DNAT, LOGL_ERROR, "PAG RESP does not fit. Length was %d.\n", length);
+ return -1;
+ }
+
+ resp = (struct gsm48_pag_resp *) data;
+ if (gsm48_paging_extract_mi(resp, length, mi_string, &mi_type) < 0) {
+ LOGP(DNAT, LOGL_ERROR, "Failed to extract the MI.\n");
+ return -1;
+ }
+
+ /* we need to let it pass for now */
+ if (mi_type != GSM_MI_TYPE_IMSI)
+ return 0;
+
+ *imsi = talloc_strdup(bsc, mi_string);
+ return 1;
+}
+
+static int _dt_check_id_resp(struct bsc_connection *bsc,
+ uint8_t *data, unsigned int length,
+ struct nat_sccp_connection *con,
+ struct bsc_nat_reject_cause *cause)
+{
+ char mi_string[GSM48_MI_SIZE];
+ uint8_t mi_type;
+
+ if (length < 2) {
+ LOGP(DNAT, LOGL_ERROR, "mi does not fit.\n");
+ return -1;
+ }
+
+ if (data[0] < length - 1) {
+ LOGP(DNAT, LOGL_ERROR, "mi length too big.\n");
+ return -2;
+ }
+
+ mi_type = data[1] & GSM_MI_TYPE_MASK;
+ gsm48_mi_to_string(mi_string, sizeof(mi_string), &data[1], data[0]);
+
+ if (mi_type != GSM_MI_TYPE_IMSI)
+ return 0;
+
+ con->imsi_checked = 1;
+ con->imsi = talloc_strdup(con, mi_string);
+ return auth_imsi(bsc, mi_string, cause);
+}
+
+
+/* Filter out CR data... */
+int bsc_nat_filter_sccp_cr(struct bsc_connection *bsc, struct msgb *msg,
+ struct bsc_nat_parsed *parsed, int *con_type,
+ char **imsi, struct bsc_nat_reject_cause *cause)
+{
+ struct tlv_parsed tp;
+ struct gsm48_hdr *hdr48;
+ int hdr48_len;
+ int len, ret = 0;
+ uint8_t msg_type, proto;
+
+ *con_type = NAT_CON_TYPE_NONE;
+ cause->cm_reject_cause = GSM48_REJECT_PLMN_NOT_ALLOWED;
+ cause->lu_reject_cause = GSM48_REJECT_PLMN_NOT_ALLOWED;
+ *imsi = NULL;
+
+ if (parsed->gsm_type != BSS_MAP_MSG_COMPLETE_LAYER_3) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Rejecting CR message due wrong GSM Type %d\n", parsed->gsm_type);
+ return -1;
+ }
+
+ /* the parsed has had some basic l3 length check */
+ len = msg->l3h[1];
+ if (msgb_l3len(msg) - 3 < len) {
+ LOGP(DNAT, LOGL_ERROR,
+ "The CR Data has not enough space...\n");
+ return -1;
+ }
+
+ msg->l4h = &msg->l3h[3];
+ len -= 1;
+
+ tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l4h, len, 0, 0);
+
+ if (!TLVP_PRESENT(&tp, GSM0808_IE_LAYER_3_INFORMATION)) {
+ LOGP(DNAT, LOGL_ERROR, "CR Data does not contain layer3 information.\n");
+ return -1;
+ }
+
+ hdr48_len = TLVP_LEN(&tp, GSM0808_IE_LAYER_3_INFORMATION);
+
+ if (hdr48_len < sizeof(*hdr48)) {
+ LOGP(DNAT, LOGL_ERROR, "GSM48 header does not fit.\n");
+ return -1;
+ }
+
+ hdr48 = (struct gsm48_hdr *) TLVP_VAL(&tp, GSM0808_IE_LAYER_3_INFORMATION);
+
+ proto = hdr48->proto_discr & 0x0f;
+ msg_type = hdr48->msg_type & 0xbf;
+ if (proto == GSM48_PDISC_MM &&
+ msg_type == GSM48_MT_MM_LOC_UPD_REQUEST) {
+ *con_type = NAT_CON_TYPE_LU;
+ ret = _cr_check_loc_upd(bsc, &hdr48->data[0],
+ hdr48_len - sizeof(*hdr48), imsi);
+ } else if (proto == GSM48_PDISC_MM &&
+ msg_type == GSM48_MT_MM_CM_SERV_REQ) {
+ *con_type = NAT_CON_TYPE_CM_SERV_REQ;
+ ret = _cr_check_cm_serv_req(bsc, &hdr48->data[0],
+ hdr48_len - sizeof(*hdr48),
+ con_type, imsi);
+ } else if (proto == GSM48_PDISC_RR &&
+ msg_type == GSM48_MT_RR_PAG_RESP) {
+ *con_type = NAT_CON_TYPE_PAG_RESP;
+ ret = _cr_check_pag_resp(bsc, &hdr48->data[0],
+ hdr48_len - sizeof(*hdr48), imsi);
+ } else {
+ /* We only want to filter the above, let other things pass */
+ *con_type = NAT_CON_TYPE_OTHER;
+ return 0;
+ }
+
+ /* check if we are done */
+ if (ret != 1)
+ return ret;
+
+ /* the memory allocation failed */
+ if (!*imsi)
+ return -1;
+
+ /* now check the imsi */
+ return auth_imsi(bsc, *imsi, cause);
+}
+
+int bsc_nat_filter_dt(struct bsc_connection *bsc, struct msgb *msg,
+ struct nat_sccp_connection *con, struct bsc_nat_parsed *parsed,
+ struct bsc_nat_reject_cause *cause)
+{
+ uint32_t len;
+ uint8_t msg_type, proto;
+ struct gsm48_hdr *hdr48;
+
+ cause->cm_reject_cause = GSM48_REJECT_PLMN_NOT_ALLOWED;
+ cause->lu_reject_cause = GSM48_REJECT_PLMN_NOT_ALLOWED;
+
+ if (con->imsi_checked)
+ return 0;
+
+ /* only care about DTAP messages */
+ if (parsed->bssap != BSSAP_MSG_DTAP)
+ return 0;
+
+ hdr48 = bsc_unpack_dtap(parsed, msg, &len);
+ if (!hdr48)
+ return -1;
+
+ proto = hdr48->proto_discr & 0x0f;
+ msg_type = hdr48->msg_type & 0xbf;
+ if (proto != GSM48_PDISC_MM || msg_type != GSM48_MT_MM_ID_RESP)
+ return 0;
+
+ return _dt_check_id_resp(bsc, &hdr48->data[0],
+ len - sizeof(*hdr48), con, cause);
+}