[PATCH] openbsc[master]: SGSN: use unique AUTH REQ reference

[Max]

Review at  https://gerrit.osmocom.org/464

SGSN: use unique AUTH REQ reference

The A&C reference number specified in 3GPP TS 24.008 § 10.5.5.19
identifies particular request sent by network with the related response
sent by MS. The value transparently copied from request to response by
MS: the spec do not specify what exactly should be in there - use rand()
to decrease chance for collisions.

Change-Id: I3638821a9b4a0532b28dbbb50faa30c4082579f6
Related: OS#1582
---
M openbsc/include/openbsc/gprs_sgsn.h
M openbsc/src/gprs/gprs_gmm.c
2 files changed, 11 insertions(+), 3 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/openbsc refs/changes/64/464/1

diff --git a/openbsc/include/openbsc/gprs_sgsn.h b/openbsc/include/openbsc/gprs_sgsn.h
index 0e574d8..3f91fb6 100644
--- a/openbsc/include/openbsc/gprs_sgsn.h
+++ b/openbsc/include/openbsc/gprs_sgsn.h
@@ -158,6 +158,7 @@
 	/* Iu: CK, IK, KSI */
 	/* CKSN */
 	enum gprs_ciph_algo	ciph_algo;
+	uint8_t auth_ref;
 
 	struct {
 		uint8_t	len;
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 5db69dd..4899a42 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -438,7 +438,9 @@
 	acreq->ciph_alg = algo & 0xf;
 	acreq->imeisv_req = 0x1;
 	acreq->force_stby = 0x0;
-	acreq->ac_ref_nr = 0x0;	/* FIXME: increment this? */
+	/* 3GPP TS 24.008 § 10.5.5.19: */
+	acreq->ac_ref_nr = rand();
+	mm->auth_ref = acreq->ac_ref_nr;
 
 	/* Only if authentication is requested we need to set RAND + CKSN */
 	if (rand) {
@@ -490,13 +492,18 @@
 		return 0;
 	}
 
+	if (acr->ac_ref_nr != ctx->auth_ref) {
+		LOGMMCTXP(LOGL_NOTICE, ctx, "Reference mismatch for Auth & Ciph"
+			  " Response: %u received, %u expected\n",
+			  acr->ac_ref_nr, ctx->auth_ref);
+		return 0;
+	}
+
 	/* Stop T3360 */
 	mmctx_timer_stop(ctx, 3360);
 
 	tlv_parse(&tp, &gsm48_gmm_att_tlvdef, acr->data,
 			(msg->data + msg->len) - acr->data, 0, 0);
-
-	/* FIXME: compare ac_ref? */
 
 	if (!TLVP_PRESENT(&tp, GSM48_IE_GMM_AUTH_SRES) ||
 	    !TLVP_PRESENT(&tp, GSM48_IE_GMM_IMEISV)) {

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I3638821a9b4a0532b28dbbb50faa30c4082579f6
Gerrit-PatchSet: 1
Gerrit-Project: openbsc
Gerrit-Branch: master
Gerrit-Owner: Max <msuraev at sysmocom.de>