SGSN: split GEA key management from TLLI

Move GEA key from TLLI assignment into separate function.

Change-Id: I8a0bc907072dc19cd9535a28b5252dc0f05357cc
Related: OS#1582

4 files changed, 38 insertions, 21 deletions

diff --git a/openbsc/include/openbsc/gprs_llc.h b/openbsc/include/openbsc/gprs_llc.h
index 8cd0c2621..f9a6dec70 100644
--- a/openbsc/include/openbsc/gprs_llc.h
+++ b/openbsc/include/openbsc/gprs_llc.h
@@ -155,7 +155,10 @@ struct gprs_llc_llme {
 
 	/* Crypto parameters */
 	enum gprs_ciph_algo algo;
-	uint8_t kc[8];
+	uint8_t kc[16];
+	uint8_t cksn;
+	/* 3GPP TS 44.064 § 8.9.2: */
+	uint32_t iov_ui;
 
 	/* over which BSSGP BTS ctx do we need to transmit */
 	uint16_t bvci;
@@ -216,8 +219,7 @@ int gprs_llgmm_reset_oldmsg(struct msgb* oldmsg, uint8_t sapi);
 
 /* 04.64 Chapter 7.2.1.1 LLGMM-ASSIGN */
 int gprs_llgmm_assign(struct gprs_llc_llme *llme,
-		      uint32_t old_tlli, uint32_t new_tlli,
-		      enum gprs_ciph_algo alg, const uint8_t *kc);
+		      uint32_t old_tlli, uint32_t new_tlli);
 int gprs_llgmm_unassign(struct gprs_llc_llme *llme);
 
 int gprs_llc_init(const char *cipher_plugin_path);
@@ -240,6 +242,7 @@ static inline int gprs_llc_is_retransmit(uint16_t nu, uint16_t vur)
 }
 
 /* LLC low level functions */
+void gprs_llme_copy_key(struct sgsn_mm_ctx *mm, struct gprs_llc_llme *llme);
 
 /* parse a GPRS LLC header, also check for invalid frames */
 int gprs_llc_hdr_parse(struct gprs_llc_hdr_parsed *ghp,
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 7f10b0712..492c766c2 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -976,8 +976,10 @@ static int gsm48_rx_gmm_att_req(struct sgsn_mm_ctx *ctx, struct msgb *msg,
 		ctx->gb.tlli_new = gprs_tmsi2tlli(ctx->p_tmsi, TLLI_LOCAL);
 
 		/* Inform LLC layer about new TLLI but keep old active */
-		gprs_llgmm_assign(ctx->gb.llme, ctx->gb.tlli, ctx->gb.tlli_new,
-				  GPRS_ALGO_GEA0, NULL);
+		if (ctx->is_authenticated)
+			gprs_llme_copy_key(ctx, ctx->gb.llme);
+
+		gprs_llgmm_assign(ctx->gb.llme, ctx->gb.tlli, ctx->gb.tlli_new);
 	}
 
 	ctx->pending_req = GSM48_MT_GMM_ATTACH_REQ;
@@ -1276,8 +1278,7 @@ static int gsm48_rx_gmm_ra_upd_req(struct sgsn_mm_ctx *mmctx, struct msgb *msg,
 
 		/* Inform LLC layer about new TLLI but keep old active */
 		gprs_llgmm_assign(mmctx->gb.llme, mmctx->gb.tlli,
-				  mmctx->gb.tlli_new, GPRS_ALGO_GEA0,
-				  NULL);
+				  mmctx->gb.tlli_new);
 	}
 
 	/* Look at PDP Context Status IE and see if MS's view of
@@ -1412,9 +1413,9 @@ static int gsm0408_rcv_gmm(struct sgsn_mm_ctx *mmctx, struct msgb *msg,
 		if (mmctx->ran_type == MM_CTX_T_GERAN_Gb) {
 			/* Unassign the old TLLI */
 			mmctx->gb.tlli = mmctx->gb.tlli_new;
+			gprs_llme_copy_key(mmctx, mmctx->gb.llme);
 			gprs_llgmm_assign(mmctx->gb.llme, 0xffffffff,
-					  mmctx->gb.tlli_new,
-					  GPRS_ALGO_GEA0, NULL);
+					  mmctx->gb.tlli_new);
 		}
 		mmctx->mm_state = GMM_REGISTERED_NORMAL;
 		rc = 0;
@@ -1435,8 +1436,8 @@ static int gsm0408_rcv_gmm(struct sgsn_mm_ctx *mmctx, struct msgb *msg,
 		if (mmctx->ran_type == MM_CTX_T_GERAN_Gb) {
 			/* Unassign the old TLLI */
 			mmctx->gb.tlli = mmctx->gb.tlli_new;
-			gprs_llgmm_assign(mmctx->gb.llme, 0xffffffff, mmctx->gb.tlli_new,
-					  GPRS_ALGO_GEA0, NULL);
+			gprs_llgmm_assign(mmctx->gb.llme, 0xffffffff,
+					  mmctx->gb.tlli_new);
 		}
 		mmctx->mm_state = GMM_REGISTERED_NORMAL;
 		rc = 0;
diff --git a/openbsc/src/gprs/gprs_llc.c b/openbsc/src/gprs/gprs_llc.c
index 64d22b374..b271e21ca 100644
--- a/openbsc/src/gprs/gprs_llc.c
+++ b/openbsc/src/gprs/gprs_llc.c
@@ -236,6 +236,7 @@ static struct gprs_llc_llme *llme_alloc(uint32_t tlli)
 	llme->old_tlli = 0xffffffff;
 	llme->state = GPRS_LLMS_UNASSIGNED;
 	llme->age_timestamp = GPRS_LLME_RESET_AGE;
+	llme->cksn = GSM_KEY_SEQ_INVAL;
 
 	for (i = 0; i < ARRAY_SIZE(llme->lle); i++)
 		lle_init(llme, i);
@@ -366,6 +367,8 @@ int gprs_llc_tx_ui(struct msgb *msg, uint8_t sapi, int command,
 		return -EFBIG;
 	}
 
+	gprs_llme_copy_key(mmctx, lle->llme);
+
 	/* Update LLE's (BVCI, NSEI) tuple */
 	lle->llme->bvci = msgb_bvci(msg);
 	lle->llme->nsei = msgb_nsei(msg);
@@ -687,18 +690,29 @@ int gprs_llc_rcvmsg(struct msgb *msg, struct tlv_parsed *tv)
 	return rc;
 }
 
+/* Propagate crypto parameters MM -> LLME */
+void gprs_llme_copy_key(struct sgsn_mm_ctx *mm, struct gprs_llc_llme *llme)
+{
+	if (!mm)
+		return;
+	if (mm->ciph_algo != GPRS_ALGO_GEA0) {
+		llme->algo = mm->ciph_algo;
+		if (llme->cksn != mm->auth_triplet.key_seq &&
+		    mm->auth_triplet.key_seq != GSM_KEY_SEQ_INVAL) {
+			memcpy(llme->kc, mm->auth_triplet.vec.kc,
+			       gprs_cipher_key_length(mm->ciph_algo));
+			llme->cksn = mm->auth_triplet.key_seq;
+		}
+	} else
+		llme->cksn = GSM_KEY_SEQ_INVAL;
+}
+
 /* 04.64 Chapter 7.2.1.1 LLGMM-ASSIGN */
 int gprs_llgmm_assign(struct gprs_llc_llme *llme,
-		      uint32_t old_tlli, uint32_t new_tlli,
-		      enum gprs_ciph_algo alg, const uint8_t *kc)
+		      uint32_t old_tlli, uint32_t new_tlli)
 {
 	unsigned int i;
 
-	/* Update the crypto parameters */
-	llme->algo = alg;
-	if (alg != GPRS_ALGO_GEA0)
-		memcpy(llme->kc, kc, sizeof(llme->kc));
-
 	if (old_tlli == 0xffffffff && new_tlli != 0xffffffff) {
 		/* TLLI Assignment 8.3.1 */
 		/* New TLLI shall be assigned and used when (re)transmitting LLC frames */
@@ -748,8 +762,7 @@ int gprs_llgmm_assign(struct gprs_llc_llme *llme,
 /* TLLI unassignment */
 int gprs_llgmm_unassign(struct gprs_llc_llme *llme)
 {
-	return gprs_llgmm_assign(llme, llme->tlli, 0xffffffff, GPRS_ALGO_GEA0,
-				 NULL);
+	return gprs_llgmm_assign(llme, llme->tlli, 0xffffffff);
 }
 
 /* Chapter 7.2.1.2 LLGMM-RESET.req */
diff --git a/openbsc/src/gprs/gprs_sgsn.c b/openbsc/src/gprs/gprs_sgsn.c
index 98439de21..711887e08 100644
--- a/openbsc/src/gprs/gprs_sgsn.c
+++ b/openbsc/src/gprs/gprs_sgsn.c
@@ -244,7 +244,7 @@ void sgsn_mm_ctx_cleanup_free(struct sgsn_mm_ctx *mm)
 
 	if (llme) {
 		/* TLLI unassignment, must be called after sgsn_mm_ctx_free */
-		gprs_llgmm_assign(llme, tlli, 0xffffffff, GPRS_ALGO_GEA0, NULL);
+		gprs_llgmm_assign(llme, tlli, 0xffffffff);
 	}
 }