Bluetooth: Add support for LE SC key generation
As the last step of the LE SC pairing process it's time to generate and
distribute keys. The generation part is unique to LE SC and so this
patch adds a dedicated function for it. We also clear the distribution
bits for keys which are not distributed with LE SC, so that the code
shared with legacy SMP will not go ahead and try to distribute them.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index f59f051..20fa07a 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -77,6 +77,7 @@
struct smp_ltk *ltk;
struct smp_ltk *slave_ltk;
struct smp_irk *remote_irk;
+ u8 *link_key;
unsigned long flags;
/* Secure Connections variables */
@@ -321,6 +322,22 @@
return err;
}
+static int smp_h6(struct crypto_hash *tfm_cmac, const u8 w[16],
+ const u8 key_id[4], u8 res[16])
+{
+ int err;
+
+ BT_DBG("w %16phN key_id %4phN", w, key_id);
+
+ err = aes_cmac(tfm_cmac, w, key_id, 4, res);
+ if (err)
+ return err;
+
+ BT_DBG("res %16phN", res);
+
+ return err;
+}
+
static int smp_ah(struct crypto_blkcipher *tfm, u8 irk[16], u8 r[3], u8 res[3])
{
u8 _res[16];
@@ -594,6 +611,7 @@
kfree(smp->csrk);
kfree(smp->slave_csrk);
+ kfree(smp->link_key);
crypto_free_blkcipher(smp->tfm_aes);
crypto_free_hash(smp->tfm_cmac);
@@ -907,6 +925,37 @@
bacpy(&smp->slave_ltk->bdaddr, &hcon->dst);
mgmt_new_ltk(hdev, smp->slave_ltk, persistent);
}
+
+ if (smp->link_key) {
+ hci_add_link_key(hdev, smp->conn->hcon, &hcon->dst,
+ smp->link_key, HCI_LK_AUTH_COMBINATION_P256,
+ 0, NULL);
+ }
+}
+
+static void sc_generate_link_key(struct smp_chan *smp)
+{
+ /* These constants are as specified in the core specification.
+ * In ASCII they spell out to 'tmp1' and 'lebr'.
+ */
+ const u8 tmp1[4] = { 0x31, 0x70, 0x6d, 0x74 };
+ const u8 lebr[4] = { 0x72, 0x62, 0x65, 0x6c };
+
+ smp->link_key = kzalloc(16, GFP_KERNEL);
+ if (!smp->link_key)
+ return;
+
+ if (smp_h6(smp->tfm_cmac, smp->tk, tmp1, smp->link_key)) {
+ kfree(smp->link_key);
+ smp->link_key = NULL;
+ return;
+ }
+
+ if (smp_h6(smp->tfm_cmac, smp->link_key, lebr, smp->link_key)) {
+ kfree(smp->link_key);
+ smp->link_key = NULL;
+ return;
+ }
}
static void smp_allow_key_dist(struct smp_chan *smp)
@@ -951,6 +1000,14 @@
*keydist &= req->resp_key_dist;
}
+ if (test_bit(SMP_FLAG_SC, &smp->flags)) {
+ if (*keydist & SMP_DIST_LINK_KEY)
+ sc_generate_link_key(smp);
+
+ /* Clear the keys which are generated but not distributed */
+ *keydist &= ~SMP_SC_NO_DIST;
+ }
+
BT_DBG("keydist 0x%x", *keydist);
if (*keydist & SMP_DIST_ENC_KEY) {