Bluetooth: Add SMP function for generating RPAs

We need a function in smp.c to generate Resolvable Random Addresses in
order to support privacy. The local RPA will need to be generated before
advertising, scanning or connecting and regenerated at periodic
intervals. This patch adds the necessary function for RPA generation.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/smp.c

@@ -124,6 +124,24 @@ bool smp_irk_matches(struct crypto_blkcipher *tfm, u8 irk[16],
 	return !memcmp(bdaddr->b, hash, 3);
 }
 
+int smp_generate_rpa(struct crypto_blkcipher *tfm, u8 irk[16], bdaddr_t *rpa)
+{
+	int err;
+
+	get_random_bytes(&rpa->b[3], 3);
+
+	rpa->b[5] &= 0x3f;	/* Clear two most significant bits */
+	rpa->b[5] |= 0x40;	/* Set second most significant bit */
+
+	err = smp_ah(tfm, irk, &rpa->b[3], rpa->b);
+	if (err < 0)
+		return err;
+
+	BT_DBG("RPA %pMR", rpa);
+
+	return 0;
+}
+
 static int smp_c1(struct crypto_blkcipher *tfm, u8 k[16], u8 r[16],
 		  u8 preq[7], u8 pres[7], u8 _iat, bdaddr_t *ia,
 		  u8 _rat, bdaddr_t *ra, u8 res[16])

net/bluetooth/smp.h

@@ -152,5 +152,6 @@ void smp_chan_destroy(struct l2cap_conn *conn);
 
 bool smp_irk_matches(struct crypto_blkcipher *tfm, u8 irk[16],
 		     bdaddr_t *bdaddr);
+int smp_generate_rpa(struct crypto_blkcipher *tfm, u8 irk[16], bdaddr_t *rpa);
 
 #endif /* __SMP_H */