From 4247cead2b77b2ad8ae2a6c1b48a450309185bb3 Mon Sep 17 00:00:00 2001 From: Holger Hans Peter Freyther Date: Sat, 4 Apr 2015 18:42:46 +0200 Subject: 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. --- openbsc/src/libfilter/Makefile.am | 9 + openbsc/src/libfilter/bsc_msg_filter.c | 443 +++++++++++++++++++++++++++++++++ 2 files changed, 452 insertions(+) create mode 100644 openbsc/src/libfilter/Makefile.am create mode 100644 openbsc/src/libfilter/bsc_msg_filter.c (limited to 'openbsc/src/libfilter') diff --git a/openbsc/src/libfilter/Makefile.am b/openbsc/src/libfilter/Makefile.am new file mode 100644 index 000000000..e24ec5f73 --- /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 000000000..64f6d7347 --- /dev/null +++ b/openbsc/src/libfilter/bsc_msg_filter.c @@ -0,0 +1,443 @@ +/* + * Access filtering + */ +/* + * (C) 2010-2012 by Holger Hans Peter Freyther + * (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 . + * + */ + +#include +#include +#include +#include +#include +#include + +#include +#include +#include + +#include +#include + +#include + +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); +} -- cgit v1.2.3