Validate the choosen UTRAN encryption algorithm
RANAP Security Command can include an encryption IE. If it includes
it the RNC can still ignore it (e.g. unsupported encryption) and
return the Security Command Complete with an choosen encryption IE:
"no encryption".
Validate the encryption element and ensure the encryption is included in
the encryption mask.
Closes: OS#4144
Change-Id: Icfc135c8b8ae862defe7114db492af600c26407f
diff --git a/src/libmsc/msc_a.c b/src/libmsc/msc_a.c
index a79cf6a..583f9e7 100644
--- a/src/libmsc/msc_a.c
+++ b/src/libmsc/msc_a.c
@@ -1404,6 +1404,7 @@
int msc_a_ran_dec_from_msc_i(struct msc_a *msc_a, struct msc_a_ran_dec_data *d)
{
struct vlr_subscr *vsub = msc_a_vsub(msc_a);
+ struct gsm_network *net = msc_a_net(msc_a);
const struct ran_msg *msg = d->ran_dec;
int rc = -99;
@@ -1459,7 +1460,25 @@
msc_a->geran_encr.alg_id = msg->cipher_mode_complete.alg_id;
LOG_MSC_A(msc_a, LOGL_DEBUG, "Cipher Mode Complete: chosen encryption algorithm: A5/%u\n",
msc_a->geran_encr.alg_id - 1);
- };
+ }
+
+ if (msc_a->c.ran->type == OSMO_RAT_UTRAN_IU) {
+ int16_t utran_encryption;
+
+ /* utran: ensure chosen ciphering mode is allowed
+ * If the IE is missing (utran_encryption == -1), parse it as no encryption */
+ utran_encryption = msg->cipher_mode_complete.utran_encryption;
+ if (utran_encryption == -1)
+ utran_encryption = 0;
+ if ((net->uea_encryption_mask & (1 << utran_encryption)) == 0) {
+ /* cipher disallowed */
+ LOG_MSC_A(msc_a, LOGL_ERROR, "Cipher Mode Complete: RNC chosen forbidden ciphering UEA%d\n",
+ msg->cipher_mode_complete.utran_encryption);
+ vlr_subscr_rx_ciph_res(vsub, VLR_CIPH_REJECT);
+ rc = 0;
+ break;
+ }
+ }
vlr_subscr_rx_ciph_res(vsub, VLR_CIPH_COMPL);
rc = 0;