SGSN: add preliminary support for GPRS encryption
It is already functional enough to allow testing with real
phones. However, note - there are several limitations in the current
implementation:
* only default value for IOV-UI is supported at the moment
* AUTN-based key material is not supported
Related: OS#1582
Change-Id: I8900b906693496e4e6b35be5a86937c58039ed9e
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 492c766..61edc65 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -418,9 +418,9 @@
return gsm48_gmm_sendmsg(msg, 1, mm);
}
-/* Section 9.4.9: Authentication and Ciphering Request */
+/* 3GPP TS 24.008 Section 9.4.9: Authentication and Ciphering Request */
static int gsm48_tx_gmm_auth_ciph_req(struct sgsn_mm_ctx *mm, uint8_t *rnd,
- uint8_t key_seq, uint8_t algo)
+ uint8_t key_seq, bool force_standby)
{
struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 AUTH CIPH REQ");
struct gsm48_hdr *gh;
@@ -437,9 +437,11 @@
gh->msg_type = GSM48_MT_GMM_AUTH_CIPH_REQ;
acreq = (struct gsm48_auth_ciph_req *) msgb_put(msg, sizeof(*acreq));
- acreq->ciph_alg = algo & 0xf;
+ acreq->ciph_alg = mm->ciph_algo & 0xf;
+ /* § 10.5.5.10: */
acreq->imeisv_req = 0x1;
- acreq->force_stby = 0x0;
+ /* § 10.5.5.7: */
+ acreq->force_stby = force_standby;
/* 3GPP TS 24.008 § 10.5.5.19: */
if (RAND_bytes(&rbyte, 1) != 1) {
LOGP(DMM, LOGL_NOTICE, "RAND_bytes failed for A&C ref, falling "
@@ -454,11 +456,11 @@
m_rand = msgb_put(msg, 16+1);
m_rand[0] = GSM48_IE_GMM_AUTH_RAND;
memcpy(m_rand + 1, rnd, 16);
-
+ /* § 10.5.1.2: */
m_cksn = msgb_put(msg, 1);
m_cksn[0] = (GSM48_IE_GMM_CIPH_CKSN << 4) | (key_seq & 0x07);
}
-
+ /* FIXME: add AUTN for 3g auth according to 3GPP TS 24.008 § 10.5.3.1.1 */
/* FIXME: make sure we don't send any other messages to the MS */
return gsm48_gmm_sendmsg(msg, 1, mm);
@@ -652,8 +654,7 @@
mmctx_timer_start(ctx, 3360, sgsn->cfg.timers.T3360);
return gsm48_tx_gmm_auth_ciph_req(ctx, at->vec.rand,
- at->key_seq,
- GPRS_ALGO_GEA0);
+ at->key_seq, false);
}
if (ctx->auth_state == SGSN_AUTH_AUTHENTICATE && ctx->is_authenticated &&
@@ -959,7 +960,15 @@
ctx->ms_radio_access_capa.len);
ctx->ms_network_capa.len = msnc_len;
memcpy(ctx->ms_network_capa.buf, msnc, msnc_len);
-
+ if (!gprs_ms_net_cap_gea_supported(ctx->ms_network_capa.buf, msnc_len,
+ ctx->ciph_algo)) {
+ reject_cause = GMM_CAUSE_PROTO_ERR_UNSPEC;
+ LOGMMCTXP(LOGL_NOTICE, ctx, "Rejecting ATTACH REQUEST with MI "
+ "type %s because MS do not support required %s "
+ "encryption\n", gsm48_mi_type_name(mi_type),
+ get_value_string(gprs_cipher_names,ctx->ciph_algo));
+ goto rejected;
+ }
#ifdef PTMSI_ALLOC
/* Allocate a new P-TMSI (+ P-TMSI signature) and update TLLI */
/* Don't change the P-TMSI if a P-TMSI re-assignment is under way */
@@ -1355,7 +1364,7 @@
}
/* Force the MS to re-attach */
- rc = sgsn_force_reattach_oldmsg(msg);
+ rc = gsm0408_gprs_force_reattach_oldmsg(msg, llme);
/* TLLI unassignment */
gprs_llgmm_unassign(llme);
@@ -1534,8 +1543,7 @@
}
at = &mm->auth_triplet;
- gsm48_tx_gmm_auth_ciph_req(mm, at->vec.rand, at->key_seq,
- GPRS_ALGO_GEA0);
+ gsm48_tx_gmm_auth_ciph_req(mm, at->vec.rand, at->key_seq, false);
osmo_timer_schedule(&mm->timer, sgsn->cfg.timers.T3360, 0);
break;
case 3370: /* waiting for IDENTITY RESPONSE */
@@ -2094,7 +2102,7 @@
if (gh->msg_type == GSM48_MT_GSM_STATUS)
return 0;
- return sgsn_force_reattach_oldmsg(msg);
+ return gsm0408_gprs_force_reattach_oldmsg(msg, llme);
}
switch (gh->msg_type) {
@@ -2128,10 +2136,11 @@
return rc;
}
-int gsm0408_gprs_force_reattach_oldmsg(struct msgb *msg)
+int gsm0408_gprs_force_reattach_oldmsg(struct msgb *msg,
+ struct gprs_llc_llme *llme)
{
int rc;
- gprs_llgmm_reset_oldmsg(msg, GPRS_SAPI_GMM);
+ gprs_llgmm_reset_oldmsg(msg, GPRS_SAPI_GMM, llme);
rc = gsm48_tx_gmm_detach_req_oldmsg(
msg, GPRS_DET_T_MT_REATT_REQ, GMM_CAUSE_IMPL_DETACHED);