msc_a,vlr: add is_ciphering_required (accurately named)

For establishing Layer 3, pass a flag from msc_a to VLR that indicates
to fail if encryption is not possible.

An earlier patch [1] renamed a previously existing flag
require_ciphering to is_ciphering_to_be_attempted, because the naming
was not accurate. This new flag now indicates what its name suggests.

This new flag is needed for upcoming patch [2] to distinguish between
optional and mandatory encryption.

[1] Ia55085e3b36feb275bcf92fc91a4be7d1c24a6b9
[2] I5feda196fa481dd8a46b0e4721c64b7c6600f0d1

Related: OS#4830
Change-Id: I52090c5f5db997030da7c2ed9beca9c51f55f4cf

include/osmocom/msc/msc_a.h

@@ -181,6 +181,7 @@ void msc_a_pending_cm_service_req_add(struct msc_a *msc_a, enum osmo_cm_service_
 unsigned int msc_a_pending_cm_service_req_count(struct msc_a *msc_a, enum osmo_cm_service_type type);
 void msc_a_pending_cm_service_req_del(struct msc_a *msc_a, enum osmo_cm_service_type type);
 bool msc_a_is_ciphering_to_be_attempted(const struct msc_a *msc_a);
+bool msc_a_is_ciphering_required(const struct msc_a *msc_a);
 
 #define msc_a_ran_down(A,B,C) \
 	_msc_a_ran_down(A,B,C, __FILE__, __LINE__)

include/osmocom/msc/vlr.h

@@ -300,6 +300,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
 	       const struct osmo_location_area_id *new_lai,
 	       bool authentication_required,
 	       bool is_ciphering_to_be_attempted,
+	       bool is_ciphering_required,
 	       uint8_t key_seq,
 	       bool is_r99, bool is_utran,
 	       bool assign_tmsi);
@@ -464,6 +465,7 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
 		 const struct osmo_location_area_id *lai,
 		 bool authentication_required,
 		 bool is_ciphering_to_be_attempted,
+		 bool is_ciphering_required,
 		 uint8_t key_seq,
 		 bool is_r99, bool is_utran);
 

src/libmsc/gsm_04_08.c

@@ -418,6 +418,7 @@ static int mm_rx_loc_upd_req(struct msc_a *msc_a, struct msgb *msg)
 				&old_lai, &msc_a->via_cell.lai,
 				is_utran || net->authentication_required,
 				msc_a_is_ciphering_to_be_attempted(msc_a),
+				msc_a_is_ciphering_required(msc_a),
 				lu->key_seq,
 				osmo_gsm48_classmark1_is_r99(&lu->classmark1),
 				is_utran,
@@ -819,6 +820,7 @@ int gsm48_rx_mm_serv_req(struct msc_a *msc_a, struct msgb *msg)
 			 &mi, &msc_a->via_cell.lai,
 			 is_utran || net->authentication_required,
 			 msc_a_is_ciphering_to_be_attempted(msc_a),
+			 msc_a_is_ciphering_required(msc_a),
 			 req->cipher_key_seq,
 			 osmo_gsm48_classmark2_is_r99(cm2, cm2_len),
 			 is_utran);
@@ -945,6 +947,7 @@ static int gsm48_rx_cm_reest_req(struct msc_a *msc_a, struct msgb *msg)
 			 &mi, &msc_a->via_cell.lai,
 			 is_utran || net->authentication_required,
 			 msc_a_is_ciphering_to_be_attempted(msc_a),
+			 msc_a_is_ciphering_required(msc_a),
 			 req->cipher_key_seq,
 			 osmo_gsm48_classmark2_is_r99(cm2, cm2_len),
 			 is_utran);
@@ -1307,6 +1310,7 @@ static int gsm48_rx_rr_pag_resp(struct msc_a *msc_a, struct msgb *msg)
 			 VLR_PR_ARQ_T_PAGING_RESP, 0, &mi, &msc_a->via_cell.lai,
 			 is_utran || net->authentication_required,
 			 msc_a_is_ciphering_to_be_attempted(msc_a),
+			 msc_a_is_ciphering_required(msc_a),
 			 pr->key_seq,
 			 osmo_gsm48_classmark2_is_r99(cm2, classmark2_len),
 			 is_utran);

src/libmsc/msc_a.c

@@ -116,6 +116,18 @@ bool msc_a_is_ciphering_to_be_attempted(const struct msc_a *msc_a)
 		return net->a5_encryption_mask > 0x1;
 }
 
+bool msc_a_is_ciphering_required(const struct msc_a *msc_a)
+{
+	struct gsm_network *net = msc_a_net(msc_a);
+	bool is_utran = (msc_a->c.ran->type == OSMO_RAT_UTRAN_IU);
+	if (is_utran)
+		return net->uea_encryption_mask
+			&& ((net->uea_encryption_mask & (1 << OSMO_UTRAN_UEA0)) == 0);
+	else
+		return net->a5_encryption_mask
+			&& ((net->a5_encryption_mask & 0x1) == 0);
+}
+
 static void update_counters(struct osmo_fsm_inst *fi, bool conn_accepted)
 {
 	struct msc_a *msc_a = fi->priv;

src/libvlr/vlr_access_req_fsm.c

@@ -67,7 +67,12 @@ struct proc_arq_priv {
 	uint32_t tmsi;
 	struct osmo_location_area_id lai;
 	bool authentication_required;
+	/* is_ciphering_to_be_attempted: true when any A5/n > 0 are enabled. Ciphering is allowed, always attempt to get Auth Info from
+	 * the HLR. */
 	bool is_ciphering_to_be_attempted;
+	/* is_ciphering_required: true when A5/0 is disabled. If we cannot get Auth Info from the HLR, reject the
+	 * subscriber. */
+	bool is_ciphering_required;
 	uint8_t key_seq;
 	bool is_r99;
 	bool is_utran;
@@ -635,12 +640,16 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
 		 const struct osmo_location_area_id *lai,
 		 bool authentication_required,
 		 bool is_ciphering_to_be_attempted,
+		 bool is_ciphering_required,
 		 uint8_t key_seq,
 		 bool is_r99, bool is_utran)
 {
 	struct osmo_fsm_inst *fi;
 	struct proc_arq_priv *par;
 
+	if (is_ciphering_required)
+		OSMO_ASSERT(is_ciphering_to_be_attempted);
+
 	fi = osmo_fsm_inst_alloc_child(&proc_arq_vlr_fsm, parent,
 				       parent_event_failure);
 	if (!fi)
@@ -658,6 +667,7 @@ vlr_proc_acc_req(struct osmo_fsm_inst *parent,
 	par->parent_event_data = parent_event_data;
 	par->authentication_required = authentication_required;
 	par->is_ciphering_to_be_attempted = is_ciphering_to_be_attempted;
+	par->is_ciphering_required = is_ciphering_required;
 	par->key_seq = key_seq;
 	par->is_r99 = is_r99;
 	par->is_utran = is_utran;

src/libvlr/vlr_lu_fsm.c

@@ -676,7 +676,12 @@ struct lu_fsm_priv {
 	struct osmo_location_area_id old_lai;
 	struct osmo_location_area_id new_lai;
 	bool authentication_required;
+	/* is_ciphering_to_be_attempted: true when any A5/n > 0 are enabled. Ciphering is allowed, always attempt to get Auth Info from
+	 * the HLR. */
 	bool is_ciphering_to_be_attempted;
+	/* is_ciphering_required: true when A5/0 is disabled. If we cannot get Auth Info from the HLR, reject the
+	 * subscriber. */
+	bool is_ciphering_required;
 	uint8_t key_seq;
 	bool is_r99;
 	bool is_utran;
@@ -1476,6 +1481,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
 	       const struct osmo_location_area_id *new_lai,
 	       bool authentication_required,
 	       bool is_ciphering_to_be_attempted,
+	       bool is_ciphering_required,
 	       uint8_t key_seq,
 	       bool is_r99, bool is_utran,
 	       bool assign_tmsi)
@@ -1483,6 +1489,9 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
 	struct osmo_fsm_inst *fi;
 	struct lu_fsm_priv *lfp;
 
+	if (is_ciphering_required)
+		OSMO_ASSERT(is_ciphering_to_be_attempted);
+
 	fi = osmo_fsm_inst_alloc_child(&vlr_lu_fsm, parent, parent_event_failure);
 	if (!fi)
 		return NULL;
@@ -1500,6 +1509,7 @@ vlr_loc_update(struct osmo_fsm_inst *parent,
 	lfp->parent_event_data = parent_event_data;
 	lfp->authentication_required = authentication_required;
 	lfp->is_ciphering_to_be_attempted = is_ciphering_to_be_attempted;
+	lfp->is_ciphering_required = is_ciphering_required;
 	lfp->key_seq = key_seq;
 	lfp->is_r99 = is_r99;
 	lfp->is_utran = is_utran;