From 8a9bf6f21518925c2c1a62ffa7935fe80401cbfe Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Thu, 10 May 2018 22:00:49 +0200
Subject: bsc: Verify correct encryption n RSL CHAN_ACT during assignment

Change-Id: Iff77586ea39da32df570048b1d83f5a0edb5a533
---
 bsc/BSC_Tests.ttcn             |  1 -
 bsc/MSC_ConnectionHandler.ttcn | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index b3c7c614..14f3724a 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -1443,7 +1443,6 @@ private function f_tc_assignment_fr_a5(charstring id) runs on MSC_ConnHdlr {
 	ass_cmd.pdu.bssmap.assignmentRequest.codecList := valueof(ts_BSSMAP_IE_CodecList({ts_CodecFR}));
 
 	f_establish_fully(ass_cmd, exp_compl);
-	f_cipher_mode(g_pars.encr.enc_alg, g_pars.encr.enc_key);
 }
 testcase TC_assignment_fr_a5_0() runs on test_CT {
 	var MSC_ConnHdlr vc_conn;
diff --git a/bsc/MSC_ConnectionHandler.ttcn b/bsc/MSC_ConnectionHandler.ttcn
index c1ff9636..fe524dcf 100644
--- a/bsc/MSC_ConnectionHandler.ttcn
+++ b/bsc/MSC_ConnectionHandler.ttcn
@@ -544,6 +544,37 @@ template (value) AssignmentState ts_AssignmentStateInit := {
 	modify_done := false
 }
 
+private template RSL_IE_Body tr_EncrInfo(template RSL_AlgId alg, template octetstring key) := {
+	encr_info := {
+		len := ?,
+		alg_id := alg,
+		key := key
+	}
+}
+
+/* ensure the RSL CHAN ACT (during assignment) contains values we expect depending on test case */
+private function f_check_chan_act(AssignmentState st, RSL_Message chan_act) runs on MSC_ConnHdlr {
+	var RSL_IE_Body encr_info;
+	if (ispresent(g_pars.encr) and g_pars.encr.enc_alg != '01'O) {
+		if (not f_rsl_find_ie(chan_act, RSL_IE_ENCR_INFO, encr_info)) {
+			setverdict(fail, "Missing Encryption IE in CHAN ACT");
+		} else {
+			var RSL_AlgId alg := f_chipher_mode_bssmap_to_rsl(g_pars.encr.enc_alg);
+			if (not match(encr_info, tr_EncrInfo(alg, g_pars.encr.enc_key))) {
+				setverdict(fail, "Wrong Encryption IE in CHAN ACT");
+			}
+		}
+	} else {
+		if (f_rsl_find_ie(chan_act, RSL_IE_ENCR_INFO, encr_info)) {
+			if (encr_info.encr_info.alg_id != RSL_ALG_ID_A5_0) {
+				setverdict(fail, "Unexpected Encryption in CHAN ACT");
+			}
+		}
+	}
+	/* FIXME: validate RSL_IE_ACT_TYPE, RSL_IE_CHAN_MODE, RSL_IE_CHAN_IDENT, RSL_IE_BS_POWER,
+	 * RSL_IE_MS_POWER, RSL_IE_TIMING_ADVANCE */
+}
+
 altstep as_assignment(inout AssignmentState st) runs on MSC_ConnHdlr {
 	var RSL_Message rsl;
 	[not st.rr_ass_cmpl_seen] RSL.receive(tr_RSL_DATA_REQ(g_chan_nr)) -> value rsl {
@@ -566,6 +597,10 @@ altstep as_assignment(inout AssignmentState st) runs on MSC_ConnHdlr {
 			st.old_chan_nr := g_chan_nr;
 			g_chan_nr := new_chan_nr;
 			st.rr_ass_cmpl_seen := true;
+			/* obtain channel activation from RSL_Emulation for new channel */
+			var RSL_Message chan_act := f_rslem_get_last_act(RSL_PROC, 0, g_chan_nr);
+			/* check it (e.g. for correct ciphering parameters) */
+			f_check_chan_act(st, chan_act);
 			repeat;
 		} else {
 			setverdict(fail, "Unexpected L3 received", l3);
@@ -666,6 +701,12 @@ runs on MSC_ConnHdlr return PDU_BSSAP {
 	f_create_chan_and_exp();
 	/* we should now have a COMPL_L3 at the MSC */
 	BSSAP.receive(tr_BSSMAP_ComplL3);
+
+	/* start ciphering, if requested */
+	if (ispresent(g_pars.encr)) {
+		f_cipher_mode(g_pars.encr.enc_alg, g_pars.encr.enc_key);
+	}
+
 	f_create_mgcp_expect(mgcpcrit);
 	BSSAP.send(ass_cmd);
 
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