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libvlr: Allow 2G auth tuples to be re-used without going through AUTH 

If the key_seq we get in the first messages matches the last_tuple, then
both we and the MS already know the key to use and we don't need the
AUTH REQUEST/RESPONSE cycle.

Security wise ... not so good, and so IMHO the 'auth required' option
in the MSC should always be set. But this allows to turn on ciphering on
a channel without doing any MM transaction, and so the MS doesn't turn
on the T3240 timer which allows to have a ciphered silent-call channel
that won't timeout.

Change-Id: Ief840a2ae7a0ffd2bf0bf726f209a79e3f787646
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut 2019-03-14 11:02:36 +01:00 committed by Harald Welte
parent 31f4c1f927
commit da9f37ed20
6 changed files with 40 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/osmocom/msc/vlr.h
View File

@ -303,6 +303,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
const struct osmo_location_area_id *new_lai,
bool authentication_required,
bool ciphering_required,
uint8_t key_seq,
bool is_r99, bool is_utran,
bool assign_tmsi);
@ -446,6 +447,7 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
const struct osmo_location_area_id *lai,
bool authentication_required,
bool ciphering_required,
uint8_t key_seq,
bool is_r99, bool is_utran);
void vlr_parq_cancel(struct osmo_fsm_inst *fi,

5
src/libmsc/gsm_04_08.c
View File

@ -433,6 +433,7 @@ int mm_rx_loc_upd_req(struct ran_conn *conn, struct msgb *msg)
&old_lai, &new_lai,
is_utran || conn->network->authentication_required,
is_utran || conn->network->a5_encryption_mask > 0x01,
lu->key_seq,
classmark1_is_r99(&lu->classmark1),
is_utran,
net->vlr->cfg.assign_tmsi);
@ -820,6 +821,7 @@ int gsm48_rx_mm_serv_req(struct ran_conn *conn, struct msgb *msg)
VLR_PR_ARQ_T_CM_SERV_REQ, mi-1, &lai,
is_utran || conn->network->authentication_required,
is_utran || conn->network->a5_encryption_mask > 0x01,
req->cipher_key_seq,
classmark2_is_r99(classmark2, classmark2_len),
is_utran);
@ -1178,6 +1180,8 @@ static int gsm48_rx_rr_pag_resp(struct ran_conn *conn, struct msgb *msg)
{
struct gsm_network *net = conn->network;
struct gsm48_hdr *gh = msgb_l3(msg);
struct gsm48_pag_resp *pr =
(struct gsm48_pag_resp *)gh->data;
uint8_t classmark2_len = gh->data[1];
uint8_t *classmark2 = gh->data+2;
uint8_t *mi_lv = classmark2 + classmark2_len;
@ -1209,6 +1213,7 @@ static int gsm48_rx_rr_pag_resp(struct ran_conn *conn, struct msgb *msg)
VLR_PR_ARQ_T_PAGING_RESP, mi_lv, &lai,
is_utran || conn->network->authentication_required,
is_utran || conn->network->a5_encryption_mask > 0x01,
pr->key_seq,
classmark2_is_r99(classmark2, classmark2_len),
is_utran);

8
src/libvlr/vlr_access_req_fsm.c
View File

@ -67,6 +67,7 @@ struct proc_arq_priv {
struct osmo_location_area_id lai;
bool authentication_required;
bool ciphering_required;
uint8_t key_seq;
bool is_r99;
bool is_utran;
bool implicitly_accepted_parq_by_ciphering_cmd;
@ -316,7 +317,8 @@ static bool is_auth_required(struct proc_arq_priv *par)
/* The cases where the authentication procedure should be used
* are defined in 3GPP TS 33.102 */
/* For now we use a default value passed in to vlr_lu_fsm(). */
return par->authentication_required || par->ciphering_required;
return par->authentication_required ||
(par->ciphering_required && !auth_try_reuse_tuple(par->vsub, par->key_seq));
}
/* after the IMSI is known */
@ -528,6 +530,7 @@ static const struct osmo_fsm_state proc_arq_vlr_states[] = {
.out_state_mask = S(PR_ARQ_S_DONE) |
S(PR_ARQ_S_WAIT_OBTAIN_IMSI) |
S(PR_ARQ_S_WAIT_AUTH) |
S(PR_ARQ_S_WAIT_CIPH) |
S(PR_ARQ_S_WAIT_UPD_LOC_CHILD) |
S(PR_ARQ_S_WAIT_SUB_PRES) |
S(PR_ARQ_S_WAIT_TRACE_SUB) |
@ -540,6 +543,7 @@ static const struct osmo_fsm_state proc_arq_vlr_states[] = {
.in_event_mask = S(PR_ARQ_E_ID_IMSI),
.out_state_mask = S(PR_ARQ_S_DONE) |
S(PR_ARQ_S_WAIT_AUTH) |
S(PR_ARQ_S_WAIT_CIPH) |
S(PR_ARQ_S_WAIT_UPD_LOC_CHILD) |
S(PR_ARQ_S_WAIT_SUB_PRES) |
S(PR_ARQ_S_WAIT_TRACE_SUB) |
@ -637,6 +641,7 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
const struct osmo_location_area_id *lai,
bool authentication_required,
bool ciphering_required,
uint8_t key_seq,
bool is_r99, bool is_utran)
{
struct osmo_fsm_inst *fi;
@ -660,6 +665,7 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
par->parent_event_data = parent_event_data;
par->authentication_required = authentication_required;
par->ciphering_required = ciphering_required;
par->key_seq = key_seq;
par->is_r99 = is_r99;
par->is_utran = is_utran;

15
src/libvlr/vlr_auth_fsm.c
View File

@ -629,3 +629,18 @@ struct osmo_fsm_inst *auth_fsm_start(struct vlr_subscr *vsub,
return fi;
}
bool auth_try_reuse_tuple(struct vlr_subscr *vsub, uint8_t key_seq)
{
int max_reuse_count = vsub->vlr->cfg.auth_tuple_max_reuse_count;
struct vlr_auth_tuple *at = vsub->last_tuple;
if (!at)
return false;
if ((max_reuse_count >= 0) && (at->use_count > max_reuse_count))
return false;
if (at->key_seq != key_seq)
return false;
at->use_count++;
return true;
}

2
src/libvlr/vlr_auth_fsm.h
View File

@ -35,3 +35,5 @@ struct osmo_fsm_inst *auth_fsm_start(struct vlr_subscr *vsub,
uint32_t parent_term_event,
bool is_r99,
bool is_utran);
bool auth_try_reuse_tuple(struct vlr_subscr *vsub, uint8_t key_seq);

10
src/libvlr/vlr_lu_fsm.c
View File

@ -685,6 +685,7 @@ struct lu_fsm_priv {
struct osmo_location_area_id new_lai;
bool authentication_required;
bool ciphering_required;
uint8_t key_seq;
bool is_r99;
bool is_utran;
bool assign_tmsi;
@ -705,7 +706,8 @@ static bool is_auth_required(struct lu_fsm_priv *lfp)
/* The cases where the authentication procedure should be used
* are defined in 3GPP TS 33.102 */
/* For now we use a default value passed in to vlr_lu_fsm(). */
return lfp->authentication_required || lfp->ciphering_required;
return lfp->authentication_required ||
(lfp->ciphering_required && !auth_try_reuse_tuple(lfp->vsub, lfp->key_seq));
}
/* Determine if ciphering is required */
@ -1316,6 +1318,7 @@ static const struct osmo_fsm_state vlr_lu_fsm_states[] = {
S(VLR_ULA_S_WAIT_PVLR) |
S(VLR_ULA_S_WAIT_IMSI) |
S(VLR_ULA_S_WAIT_AUTH) |
S(VLR_ULA_S_WAIT_CIPH) |
S(VLR_ULA_S_WAIT_HLR_UPD) |
S(VLR_ULA_S_DONE),
.name = OSMO_STRINGIFY(VLR_ULA_S_IDLE),
@ -1326,6 +1329,7 @@ static const struct osmo_fsm_state vlr_lu_fsm_states[] = {
.out_state_mask = S(VLR_ULA_S_WAIT_PVLR) |
S(VLR_ULA_S_WAIT_IMSI) |
S(VLR_ULA_S_WAIT_AUTH) |
S(VLR_ULA_S_WAIT_CIPH) |
S(VLR_ULA_S_WAIT_HLR_UPD) |
S(VLR_ULA_S_DONE),
.name = OSMO_STRINGIFY(VLR_ULA_S_WAIT_IMEISV),
@ -1336,6 +1340,7 @@ static const struct osmo_fsm_state vlr_lu_fsm_states[] = {
S(VLR_ULA_E_SEND_ID_NACK),
.out_state_mask = S(VLR_ULA_S_WAIT_IMSI) |
S(VLR_ULA_S_WAIT_AUTH) |
S(VLR_ULA_S_WAIT_CIPH) |
S(VLR_ULA_S_DONE),
.name = OSMO_STRINGIFY(VLR_ULA_S_WAIT_PVLR),
.action = lu_fsm_wait_pvlr,
@ -1360,6 +1365,7 @@ static const struct osmo_fsm_state vlr_lu_fsm_states[] = {
[VLR_ULA_S_WAIT_IMSI] = {
.in_event_mask = S(VLR_ULA_E_ID_IMSI),
.out_state_mask = S(VLR_ULA_S_WAIT_AUTH) |
S(VLR_ULA_S_WAIT_CIPH) |
S(VLR_ULA_S_WAIT_HLR_UPD) |
S(VLR_ULA_S_DONE),
.name = OSMO_STRINGIFY(VLR_ULA_S_WAIT_IMSI),
@ -1439,6 +1445,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
const struct osmo_location_area_id *new_lai,
bool authentication_required,
bool ciphering_required,
uint8_t key_seq,
bool is_r99, bool is_utran,
bool assign_tmsi)
{
@ -1462,6 +1469,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
lfp->parent_event_data = parent_event_data;
lfp->authentication_required = authentication_required;
lfp->ciphering_required = ciphering_required;
lfp->key_seq = key_seq;
lfp->is_r99 = is_r99;
lfp->is_utran = is_utran;
lfp->assign_tmsi = assign_tmsi;