auth_milenage: Fix non-AUTS case with OP

We only implemented OPC generation from OP in the AUTS case, but not
in the case of normal authentication vector generation.  This never
really was visible so far due to the fact that we use OPC at sysmocom,
and never the shared OP value.

Change-Id: Id3fa038dfc2ff1ba63616fa5e8eab0520481ff26

1 files changed, 24 insertions, 12 deletions

diff --git a/src/gsm/auth_milenage.c b/src/gsm/auth_milenage.c
index 8d50990b..6dd4f45a 100644
--- a/src/gsm/auth_milenage.c
+++ b/src/gsm/auth_milenage.c
@@ -30,17 +30,37 @@
  *  @{
  */
 
+static const uint8_t *gen_opc_if_needed(const struct osmo_sub_auth_data *aud, uint8_t *gen_opc)
+{
+	int rc;
+
+	/* Check if we only know OP and compute OPC if required */
+	if (aud->type == OSMO_AUTH_TYPE_UMTS && aud->u.umts.opc_is_op) {
+		rc = milenage_opc_gen(gen_opc, aud->u.umts.k, aud->u.umts.opc);
+		if (rc < 0)
+			return NULL;
+		return gen_opc;
+	} else
+		return aud->u.umts.opc;
+}
+
 static int milenage_gen_vec(struct osmo_auth_vector *vec,
 			    struct osmo_sub_auth_data *aud,
 			    const uint8_t *_rand)
 {
 	size_t res_len = sizeof(vec->res);
 	uint64_t next_sqn;
+	uint8_t gen_opc[16];
+	const uint8_t *opc;
 	uint8_t sqn[6];
 	uint64_t ind_mask;
 	uint64_t seq_1;
 	int rc;
 
+	opc = gen_opc_if_needed(aud, gen_opc);
+	if (!opc)
+		return -1;
+
 	/* Determine next SQN, according to 3GPP TS 33.102:
 	 * SQN consists of SEQ and a lower significant part of IND bits:
 	 *
@@ -106,11 +126,11 @@ static int milenage_gen_vec(struct osmo_auth_vector *vec,
 	next_sqn = ((aud->u.umts.sqn + seq_1) & ind_mask) + aud->u.umts.ind;
 
 	osmo_store64be_ext(next_sqn, sqn, 6);
-	milenage_generate(aud->u.umts.opc, aud->u.umts.amf, aud->u.umts.k,
+	milenage_generate(opc, aud->u.umts.amf, aud->u.umts.k,
 			  sqn, _rand,
 			  vec->autn, vec->ik, vec->ck, vec->res, &res_len);
 	vec->res_len = res_len;
-	rc = gsm_milenage(aud->u.umts.opc, aud->u.umts.k, _rand, vec->sres, vec->kc);
+	rc = gsm_milenage(opc, aud->u.umts.k, _rand, vec->sres, vec->kc);
 	if (rc < 0)
 		return rc;
 
@@ -129,18 +149,10 @@ static int milenage_gen_vec_auts(struct osmo_auth_vector *vec,
 {
 	uint8_t sqn_out[6];
 	uint8_t gen_opc[16];
-	uint8_t *opc;
+	const uint8_t *opc;
 	int rc;
 
-	/* Check if we only know OP and compute OPC if required */
-	if (aud->type == OSMO_AUTH_TYPE_UMTS && aud->u.umts.opc_is_op) {
-		rc = milenage_opc_gen(gen_opc, aud->u.umts.k,
-				      aud->u.umts.opc);
-		if (rc < 0)
-			return rc;
-		opc = gen_opc;
-	} else
-		opc = aud->u.umts.opc;
+	opc = gen_opc_if_needed(aud, gen_opc);
 
 	rc = milenage_auts(opc, aud->u.umts.k, rand_auts, auts, sqn_out);
 	if (rc < 0)