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osmo-bsc/src/osmo-bsc_nat/bsc_nat_rewrite.c

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/*
* Message rewriting functionality
*/
/*
* (C) 2010-2013 by Holger Hans Peter Freyther <zecke@selfish.org>
* (C) 2010-2013 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 <openbsc/nat_rewrite_trie.h>
#include <osmocom/core/linuxlist.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/utils.h>
#include <osmocom/gsm/gsm0808.h>
#include <osmocom/gsm/ipa.h>
#include <osmocom/gsm/protocol/gsm_08_08.h>
#include <osmocom/gsm/protocol/gsm_04_11.h>
#include <osmocom/sccp/sccp.h>
static char *trie_lookup(struct nat_rewrite *trie, const char *number,
regoff_t off, void *ctx)
{
struct nat_rewrite_rule *rule;
if (!trie) {
LOGP(DCC, LOGL_ERROR,
"Asked to do a table lookup but no table.\n");
return NULL;
}
rule = nat_rewrite_lookup(trie, number);
if (!rule) {
LOGP(DCC, LOGL_DEBUG,
"Couldn't find a prefix rule for %s\n", number);
return NULL;
}
return talloc_asprintf(ctx, "%s%s", rule->rewrite, &number[off]);
}
static char *match_and_rewrite_number(void *ctx, const char *number,
const char *imsi, struct llist_head *list,
struct nat_rewrite *trie)
{
struct bsc_nat_num_rewr_entry *entry;
char *new_number = NULL;
/* need to find a replacement and then fix it */
llist_for_each_entry(entry, list, list) {
regmatch_t matches[2];
/* check the IMSI match */
if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
continue;
/* this regexp matches... */
if (regexec(&entry->num_reg, number, 2, matches, 0) == 0
&& matches[1].rm_eo != -1) {
if (entry->is_prefix_lookup)
new_number = trie_lookup(trie, number,
matches[1].rm_so, ctx);
else
new_number = talloc_asprintf(ctx, "%s%s",
entry->replace,
&number[matches[1].rm_so]);
}
if (new_number)
break;
}
return new_number;
}
static char *rewrite_isdn_number(struct bsc_nat *nat, struct llist_head *rewr_list,
void *ctx, const char *imsi,
struct gsm_mncc_number *called)
{
char int_number[sizeof(called->number) + 2];
char *number = called->number;
if (llist_empty(&nat->num_rewr)) {
LOGP(DCC, LOGL_DEBUG, "Rewrite rules empty.\n");
return NULL;
}
/* only ISDN plan */
if (called->plan != 1) {
LOGP(DCC, LOGL_DEBUG, "Called plan is not 1 it was %d\n",
called->plan);
return NULL;
}
/* international, prepend */
if (called->type == 1) {
int_number[0] = '+';
memcpy(&int_number[1], number, strlen(number) + 1);
number = int_number;
}
return match_and_rewrite_number(ctx, number,
imsi, rewr_list, nat->num_rewr_trie);
}
static void update_called_number(struct gsm_mncc_number *called,
const char *chosen_number)
{
if (strncmp(chosen_number, "00", 2) == 0) {
called->type = 1;
osmo_strlcpy(called->number, chosen_number + 2,
sizeof(called->number));
} else {
/* rewrite international to unknown */
if (called->type == 1)
called->type = 0;
osmo_strlcpy(called->number, chosen_number,
sizeof(called->number));
}
}
/**
* Rewrite non global numbers... according to rules based on the IMSI
*/
static struct msgb *rewrite_setup(struct bsc_nat *nat, struct msgb *msg,
struct bsc_nat_parsed *parsed, const char *imsi,
struct gsm48_hdr *hdr48, const uint32_t len)
{
struct tlv_parsed tp;
unsigned int payload_len;
struct gsm_mncc_number called;
struct msgb *out;
char *new_number_pre = NULL, *new_number_post = NULL, *chosen_number;
uint8_t *outptr;
const uint8_t *msgptr;
int sec_len;
/* decode and rewrite the message */
payload_len = len - sizeof(*hdr48);
tlv_parse(&tp, &gsm48_att_tlvdef, hdr48->data, payload_len, 0, 0);
/* no number, well let us ignore it */
if (!TLVP_PRESENT(&tp, GSM48_IE_CALLED_BCD))
return NULL;
memset(&called, 0, sizeof(called));
gsm48_decode_called(&called,
TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) - 1);
/* check if it looks international and stop */
LOGP(DCC, LOGL_DEBUG,
"Pre-Rewrite for IMSI(%s) Plan(%d) Type(%d) Number(%s)\n",
imsi, called.plan, called.type, called.number);
new_number_pre = rewrite_isdn_number(nat, &nat->num_rewr, msg, imsi, &called);
if (!new_number_pre) {
LOGP(DCC, LOGL_DEBUG, "No IMSI(%s) match found, returning message.\n",
imsi);
return NULL;
}
if (strlen(new_number_pre) > sizeof(called.number)) {
LOGP(DCC, LOGL_ERROR, "Number %s is too long for structure.\n",
new_number_pre);
talloc_free(new_number_pre);
return NULL;
}
update_called_number(&called, new_number_pre);
/* another run through the re-write engine with other rules */
LOGP(DCC, LOGL_DEBUG,
"Post-Rewrite for IMSI(%s) Plan(%d) Type(%d) Number(%s)\n",
imsi, called.plan, called.type, called.number);
new_number_post = rewrite_isdn_number(nat, &nat->num_rewr_post, msg,
imsi, &called);
chosen_number = new_number_post ? new_number_post : new_number_pre;
if (strlen(chosen_number) > sizeof(called.number)) {
LOGP(DCC, LOGL_ERROR, "Number %s is too long for structure.\n",
chosen_number);
talloc_free(new_number_pre);
talloc_free(new_number_post);
return NULL;
}
/*
* Need to create a new message now based on the old onew
* with a new number. We can sadly not patch this in place
* so we will need to regenerate it.
*/
out = msgb_alloc_headroom(4096, 128, "changed-setup");
if (!out) {
LOGP(DCC, LOGL_ERROR, "Failed to allocate.\n");
talloc_free(new_number_pre);
talloc_free(new_number_post);
return NULL;
}
/* copy the header */
outptr = msgb_put(out, sizeof(*hdr48));
memcpy(outptr, hdr48, sizeof(*hdr48));
/* copy everything up to the number */
sec_len = TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) - 2 - &hdr48->data[0];
outptr = msgb_put(out, sec_len);
memcpy(outptr, &hdr48->data[0], sec_len);
/* create the new number */
update_called_number(&called, chosen_number);
LOGP(DCC, LOGL_DEBUG,
"Chosen number for IMSI(%s) is Plan(%d) Type(%d) Number(%s)\n",
imsi, called.plan, called.type, called.number);
gsm48_encode_called(out, &called);
/* copy thre rest */
msgptr = TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) +
TLVP_LEN(&tp, GSM48_IE_CALLED_BCD);
sec_len = payload_len - (msgptr - &hdr48->data[0]);
outptr = msgb_put(out, sec_len);
memcpy(outptr, msgptr, sec_len);
talloc_free(new_number_pre);
talloc_free(new_number_post);
return out;
}
/**
* Find a new SMSC address, returns an allocated string that needs to be
* freed or is NULL.
*/
static char *find_new_smsc(struct bsc_nat *nat, void *ctx, const char *imsi,
const char *smsc_addr, const char *dest_nr)
{
struct bsc_nat_num_rewr_entry *entry;
char *new_number = NULL;
uint8_t dest_match = llist_empty(&nat->tpdest_match);
/* We will find a new number now */
llist_for_each_entry(entry, &nat->smsc_rewr, list) {
regmatch_t matches[2];
/* check the IMSI match */
if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
continue;
/* this regexp matches... */
if (regexec(&entry->num_reg, smsc_addr, 2, matches, 0) == 0 &&
matches[1].rm_eo != -1)
new_number = talloc_asprintf(ctx, "%s%s",
entry->replace,
&smsc_addr[matches[1].rm_so]);
if (new_number)
break;
}
if (!new_number)
return NULL;
/*
* now match the number against another list
*/
llist_for_each_entry(entry, &nat->tpdest_match, list) {
/* check the IMSI match */
if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
continue;
if (regexec(&entry->num_reg, dest_nr, 0, NULL, 0) == 0) {
dest_match = 1;
break;
}
}
if (!dest_match) {
talloc_free(new_number);
return NULL;
}
return new_number;
}
/**
* Clear the TP-SRR from the TPDU header
*/
static uint8_t sms_new_tpdu_hdr(struct bsc_nat *nat, const char *imsi,
const char *dest_nr, uint8_t hdr)
{
struct bsc_nat_num_rewr_entry *entry;
/* We will find a new number now */
llist_for_each_entry(entry, &nat->sms_clear_tp_srr, list) {
/* check the IMSI match */
if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
continue;
if (regexec(&entry->num_reg, dest_nr, 0, NULL, 0) != 0)
continue;
/* matched phone number and imsi */
return hdr & ~0x20;
}
return hdr;
}
/**
* Check if we need to rewrite the number. For this SMS.
*/
static char *sms_new_dest_nr(struct bsc_nat *nat, void *ctx,
const char *imsi, const char *dest_nr)
{
return match_and_rewrite_number(ctx, dest_nr, imsi,
&nat->sms_num_rewr, NULL);
}
/**
* This is a helper for GSM 04.11 8.2.5.2 Destination address element
*/
void sms_encode_addr_element(struct msgb *out, const char *new_number,
int format, int tp_data)
{
uint8_t new_addr_len;
uint8_t new_addr[26];
/*
* Copy the new number. We let libosmocore encode it, then set
* the extension followed after the length. Depending on if
* we want to write RP we will let the TLV code add the
* length for us or we need to use strlen... This is not very clear
* as of 03.40 and 04.11.
*/
new_addr_len = gsm48_encode_bcd_number(new_addr, ARRAY_SIZE(new_addr),
1, new_number);
new_addr[1] = format;
if (tp_data) {
uint8_t *data = msgb_put(out, new_addr_len);
memcpy(data, new_addr, new_addr_len);
data[0] = strlen(new_number);
} else {
msgb_lv_put(out, new_addr_len - 1, new_addr + 1);
}
}
static struct msgb *sms_create_new(uint8_t type, uint8_t ref,
struct gsm48_hdr *old_hdr48,
const uint8_t *orig_addr_ptr,
int orig_addr_len, const char *new_number,
const uint8_t *data_ptr, int data_len,
uint8_t tpdu_first_byte,
const int old_dest_len, const char *new_dest_nr)
{
struct gsm48_hdr *new_hdr48;
struct msgb *out;
/*
* We need to re-create the patched structure. This is why we have
* saved the above pointers.
*/
out = msgb_alloc_headroom(4096, 128, "changed-smsc");
if (!out) {
LOGP(DNAT, LOGL_ERROR, "Failed to allocate.\n");
return NULL;
}
out->l2h = out->data;
msgb_v_put(out, GSM411_MT_RP_DATA_MO);
msgb_v_put(out, ref);
msgb_lv_put(out, orig_addr_len, orig_addr_ptr);
sms_encode_addr_element(out, new_number, 0x91, 0);
/* Patch the TPDU from here on */
/**
* Do we need to put a new TP-Destination-Address (TP-DA) here or
* can we copy the old thing? For the TP-DA we need to find out the
* new size.
*/
if (new_dest_nr) {
uint8_t *data, *new_size;
/* reserve the size and write the header */
new_size = msgb_put(out, 1);
out->l3h = new_size + 1;
msgb_v_put(out, tpdu_first_byte);
msgb_v_put(out, data_ptr[1]);
/* encode the new number and put it */
if (strncmp(new_dest_nr, "00", 2) == 0)
sms_encode_addr_element(out, new_dest_nr + 2, 0x91, 1);
else
sms_encode_addr_element(out, new_dest_nr, 0x81, 1);
/* Copy the rest after the TP-DS */
data = msgb_put(out, data_len - 2 - 1 - old_dest_len);
memcpy(data, &data_ptr[2 + 1 + old_dest_len], data_len - 2 - 1 - old_dest_len);
/* fill in the new size */
new_size[0] = msgb_l3len(out);
} else {
msgb_v_put(out, data_len);
msgb_tv_fixed_put(out, tpdu_first_byte, data_len - 1, &data_ptr[1]);
}
/* prepend GSM 04.08 header */
new_hdr48 = (struct gsm48_hdr *) msgb_push(out, sizeof(*new_hdr48) + 1);
memcpy(new_hdr48, old_hdr48, sizeof(*old_hdr48));
new_hdr48->data[0] = msgb_l2len(out);
return out;
}
/**
* Parse the SMS and check if it needs to be rewritten
*/
static struct msgb *rewrite_sms(struct bsc_nat *nat, struct msgb *msg,
struct bsc_nat_parsed *parsed, const char *imsi,
struct gsm48_hdr *hdr48, const uint32_t len)
{
unsigned int payload_len;
unsigned int cp_len;
uint8_t ref;
uint8_t orig_addr_len, *orig_addr_ptr;
uint8_t dest_addr_len, *dest_addr_ptr;
uint8_t data_len, *data_ptr;
char smsc_addr[30];
uint8_t dest_len, orig_dest_len;
char _dest_nr[30];
char *dest_nr;
char *new_dest_nr;
char *new_number = NULL;
uint8_t tpdu_hdr;
struct msgb *out;
payload_len = len - sizeof(*hdr48);
if (payload_len < 1) {
LOGP(DNAT, LOGL_ERROR, "SMS too short for things. %d\n", payload_len);
return NULL;
}
cp_len = hdr48->data[0];
if (payload_len + 1 < cp_len) {
LOGP(DNAT, LOGL_ERROR, "SMS RPDU can not fit in: %d %d\n", cp_len, payload_len);
return NULL;
}
if (hdr48->data[1] != GSM411_MT_RP_DATA_MO)
return NULL;
if (cp_len < 5) {
LOGP(DNAT, LOGL_ERROR, "RD-DATA can not fit in the CP len: %d\n", cp_len);
return NULL;
}
/* RP */
ref = hdr48->data[2];
orig_addr_len = hdr48->data[3];
orig_addr_ptr = &hdr48->data[4];
/* the +1 is for checking if the following element has some space */
if (cp_len < 3 + orig_addr_len + 1) {
LOGP(DNAT, LOGL_ERROR, "RP-Originator addr does not fit: %d\n", orig_addr_len);
return NULL;
}
dest_addr_len = hdr48->data[3 + orig_addr_len + 1];
dest_addr_ptr = &hdr48->data[3 + orig_addr_len + 2];
if (cp_len < 3 + orig_addr_len + 1 + dest_addr_len + 1) {
LOGP(DNAT, LOGL_ERROR, "RP-Destination addr does not fit: %d\n", dest_addr_len);
return NULL;
}
gsm48_decode_bcd_number(smsc_addr, ARRAY_SIZE(smsc_addr), dest_addr_ptr - 1, 1);
data_len = hdr48->data[3 + orig_addr_len + 1 + dest_addr_len + 1];
data_ptr = &hdr48->data[3 + orig_addr_len + 1 + dest_addr_len + 2];
if (cp_len < 3 + orig_addr_len + 1 + dest_addr_len + 1 + data_len) {
LOGP(DNAT, LOGL_ERROR, "RP-Data does not fit: %d\n", data_len);
return NULL;
}
if (data_len < 3) {
LOGP(DNAT, LOGL_ERROR, "SMS-SUBMIT is too short.\n");
return NULL;
}
/* TP-PDU starts here */
if ((data_ptr[0] & 0x03) != GSM340_SMS_SUBMIT_MS2SC)
return NULL;
/*
* look into the phone number. The length is in semi-octets, we will
* need to add the byte for the number type as well.
*/
orig_dest_len = data_ptr[2];
dest_len = ((orig_dest_len + 1) / 2) + 1;
if (data_len < dest_len + 3 || dest_len < 2) {
LOGP(DNAT, LOGL_ERROR, "SMS-SUBMIT can not have TP-DestAddr.\n");
return NULL;
}
if ((data_ptr[3] & 0x80) == 0) {
LOGP(DNAT, LOGL_ERROR, "TP-DestAddr has extension. Not handled.\n");
return NULL;
}
if ((data_ptr[3] & 0x0F) == 0) {
LOGP(DNAT, LOGL_ERROR, "TP-DestAddr is of unknown type.\n");
return NULL;
}
/**
* Besides of what I think I read in GSM 03.40 and 04.11 the TP-DA
* contains the semi-octets as length (strlen), change it to the
* the number of bytes, but then change it back.
*/
data_ptr[2] = dest_len;
gsm48_decode_bcd_number(_dest_nr + 2, ARRAY_SIZE(_dest_nr) - 2,
&data_ptr[2], 1);
data_ptr[2] = orig_dest_len;
if ((data_ptr[3] & 0x70) == 0x10) {
_dest_nr[0] = _dest_nr[1] = '0';
dest_nr = &_dest_nr[0];
} else {
dest_nr = &_dest_nr[2];
}
/**
* Call functions to rewrite the data
*/
tpdu_hdr = sms_new_tpdu_hdr(nat, imsi, dest_nr, data_ptr[0]);
new_number = find_new_smsc(nat, msg, imsi, smsc_addr, dest_nr);
new_dest_nr = sms_new_dest_nr(nat, msg, imsi, dest_nr);
if (tpdu_hdr == data_ptr[0] && !new_number && !new_dest_nr)
return NULL;
out = sms_create_new(GSM411_MT_RP_DATA_MO, ref, hdr48,
orig_addr_ptr, orig_addr_len,
new_number ? new_number : smsc_addr,
data_ptr, data_len, tpdu_hdr,
dest_len, new_dest_nr);
talloc_free(new_number);
talloc_free(new_dest_nr);
return out;
}
struct msgb *bsc_nat_rewrite_msg(struct bsc_nat *nat, struct msgb *msg, struct bsc_nat_parsed *parsed, const char *imsi)
{
struct gsm48_hdr *hdr48;
uint32_t len;
uint8_t msg_type, proto;
struct msgb *new_msg = NULL, *sccp;
uint8_t link_id;
if (!imsi || strlen(imsi) < 5)
return msg;
/* only care about DTAP messages */
if (parsed->bssap != BSSAP_MSG_DTAP)
return msg;
if (!parsed->dest_local_ref)
return msg;
hdr48 = bsc_unpack_dtap(parsed, msg, &len);
if (!hdr48)
return msg;
link_id = msg->l3h[1];
proto = gsm48_hdr_pdisc(hdr48);
msg_type = gsm48_hdr_msg_type(hdr48);
if (proto == GSM48_PDISC_CC && msg_type == GSM48_MT_CC_SETUP)
new_msg = rewrite_setup(nat, msg, parsed, imsi, hdr48, len);
else if (proto == GSM48_PDISC_SMS && msg_type == GSM411_MT_CP_DATA)
new_msg = rewrite_sms(nat, msg, parsed, imsi, hdr48, len);
if (!new_msg)
return msg;
/* wrap with DTAP, SCCP, then IPA. TODO: Stop copying */
gsm0808_prepend_dtap_header(new_msg, link_id);
sccp = sccp_create_dt1(parsed->dest_local_ref, new_msg->data, new_msg->len);
talloc_free(new_msg);
if (!sccp) {
LOGP(DNAT, LOGL_ERROR, "Failed to allocate.\n");
return msg;
}
ipa_prepend_header(sccp, IPAC_PROTO_SCCP);
/* the parsed hangs off from msg but it needs to survive */
talloc_steal(sccp, parsed);
msgb_free(msg);
return sccp;
}
static void num_rewr_free_data(struct bsc_nat_num_rewr_entry *entry)
{
regfree(&entry->msisdn_reg);
regfree(&entry->num_reg);
talloc_free(entry->replace);
}
void bsc_nat_num_rewr_entry_adapt(void *ctx, struct llist_head *head,
const struct osmo_config_list *list)
{
struct bsc_nat_num_rewr_entry *entry, *tmp;
struct osmo_config_entry *cfg_entry;
/* free the old data */
llist_for_each_entry_safe(entry, tmp, head, list) {
num_rewr_free_data(entry);
llist_del(&entry->list);
talloc_free(entry);
}
if (!list)
return;
llist_for_each_entry(cfg_entry, &list->entry, list) {
char *regexp;
if (cfg_entry->text[0] == '+') {
LOGP(DNAT, LOGL_ERROR,
"Plus is not allowed in the number\n");
continue;
}
entry = talloc_zero(ctx, struct bsc_nat_num_rewr_entry);
if (!entry) {
LOGP(DNAT, LOGL_ERROR,
"Allocation of the num_rewr entry failed.\n");
continue;
}
entry->replace = talloc_strdup(entry, cfg_entry->text);
if (!entry->replace) {
LOGP(DNAT, LOGL_ERROR,
"Failed to copy the replacement text.\n");
talloc_free(entry);
continue;
}
if (strcmp("prefix_lookup", entry->replace) == 0)
entry->is_prefix_lookup = 1;
/* we will now build a regexp string */
if (cfg_entry->mcc[0] == '^') {
regexp = talloc_strdup(entry, cfg_entry->mcc);
} else {
regexp = talloc_asprintf(entry, "^%s%s",
cfg_entry->mcc[0] == '*' ?
"[0-9][0-9][0-9]" : cfg_entry->mcc,
cfg_entry->mnc[0] == '*' ?
"[0-9][0-9]" : cfg_entry->mnc);
}
if (!regexp) {
LOGP(DNAT, LOGL_ERROR, "Failed to create a regexp string.\n");
talloc_free(entry);
continue;
}
if (regcomp(&entry->msisdn_reg, regexp, 0) != 0) {
LOGP(DNAT, LOGL_ERROR,
"Failed to compile regexp '%s'\n", regexp);
talloc_free(regexp);
talloc_free(entry);
continue;
}
talloc_free(regexp);
if (regcomp(&entry->num_reg, cfg_entry->option, REG_EXTENDED) != 0) {
LOGP(DNAT, LOGL_ERROR,
"Failed to compile regexp '%s'\n", cfg_entry->option);
regfree(&entry->msisdn_reg);
talloc_free(entry);
continue;
}
/* we have copied the number */
llist_add_tail(&entry->list, head);
}
}
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