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gbproxy: Use different TLLI/P-TMSI for BSS and SGSN 

This patch modifies gbprox_make_bss_ptmsi() to generate a new P-TMSI
when patch_ptmsi is set in the configuration instead of using the
P-TMSI assigned by the SGSN. It modifies gbprox_make_sgsn_tlli() to
either use a foreign TLLI based on the SGSN side P-TMSI or (if there
is none) generate a random TLLI if patch_ptmsi is set. Otherwise, the
TLLI used by the BSS is used.

The seeds for the pseudo-random sequences sre set based on time
initially. Note that these are neither cryptographically safe nor
protected against collisions.

Ticket: OW#1259
Sponsored-by: On-Waves ehf
This commit is contained in:
Jacob Erlbeck 2014-08-11 19:12:24 +02:00 committed by Holger Hans Peter Freyther
parent 643d5228ed
commit 0d37671824
2 changed files with 53 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
openbsc/include/openbsc/gb_proxy.h
View File

@ -49,6 +49,10 @@ struct gbproxy_config {
/* IMSI checking/matching */
int check_imsi;
regex_t imsi_re_comp;
/* Used to generate identifiers */
unsigned bss_ptmsi_state;
unsigned sgsn_tlli_state;
};
struct gbproxy_patch_state {

51
openbsc/src/gprs/gb_proxy.c
View File

@ -446,6 +446,20 @@ struct gbproxy_tlli_info *gbprox_find_tlli(struct gbproxy_peer *peer,
return NULL;
}
static struct gbproxy_tlli_info *gbprox_find_tlli_by_ptmsi(
struct gbproxy_peer *peer,
uint32_t ptmsi)
{
struct gbproxy_tlli_info *tlli_info;
struct gbproxy_patch_state *state = &peer->patch_state;
llist_for_each_entry(tlli_info, &state->enabled_tllis, list)
if (tlli_info->tlli.ptmsi == ptmsi)
return tlli_info;
return NULL;
}
struct gbproxy_tlli_info *gbprox_find_tlli_by_sgsn_tlli(
struct gbproxy_peer *peer,
uint32_t tlli)
@ -1605,14 +1619,43 @@ static void gbprox_log_parse_context(struct gbproxy_parse_context *parse_ctx,
static uint32_t gbprox_make_bss_ptmsi(struct gbproxy_peer *peer,
uint32_t sgsn_ptmsi)
{
return sgsn_ptmsi;
uint32_t bss_ptmsi;
if (!peer->cfg->patch_ptmsi) {
bss_ptmsi = sgsn_ptmsi;
} else {
do {
bss_ptmsi = rand_r(&peer->cfg->bss_ptmsi_state);
bss_ptmsi = bss_ptmsi | 0xC0000000;
if (gbprox_find_tlli_by_ptmsi(peer, bss_ptmsi))
bss_ptmsi = GSM_RESERVED_TMSI;
} while (bss_ptmsi == GSM_RESERVED_TMSI);
}
return bss_ptmsi;
}
static uint32_t gbprox_make_sgsn_tlli(struct gbproxy_peer *peer,
struct gbproxy_tlli_info *tlli_info,
uint32_t bss_tlli)
{
return bss_tlli;
uint32_t sgsn_tlli;
if (!peer->cfg->patch_ptmsi) {
sgsn_tlli = bss_tlli;
} else if (tlli_info->sgsn_tlli.ptmsi != GSM_RESERVED_TMSI) {
sgsn_tlli = gprs_tmsi2tlli(tlli_info->sgsn_tlli.ptmsi,
TLLI_FOREIGN);
} else {
do {
/* create random TLLI, 0b01111xxx... */
sgsn_tlli = rand_r(&peer->cfg->sgsn_tlli_state);
sgsn_tlli = (sgsn_tlli & 0x7fffffff) | 0x78000000;
if (gbprox_find_tlli_by_sgsn_tlli(peer, sgsn_tlli))
sgsn_tlli = 0;
} while (!sgsn_tlli);
}
return sgsn_tlli;
}
static struct gbproxy_tlli_info *gbprox_update_state_ul(
@ -2698,7 +2741,11 @@ int gbprox_cleanup_peers(struct gbproxy_config *cfg, uint16_t nsei, uint16_t bvc
int gbproxy_init_config(struct gbproxy_config *cfg)
{
struct timespec tp;
INIT_LLIST_HEAD(&cfg->bts_peers);
cfg->ctrg = rate_ctr_group_alloc(tall_bsc_ctx, &global_ctrg_desc, 0);
clock_gettime(CLOCK_REALTIME, &tp);
cfg->bss_ptmsi_state = tp.tv_sec + tp.tv_nsec;
cfg->sgsn_tlli_state = tp.tv_sec - tp.tv_nsec;
return 0;
}