Bluetooth: Add LE SMP Cryptoolbox functions

This patch implements SMP crypto functions called ah, c1, s1 and e.
It also implements auxiliary functions. All These functions are needed
for SMP keys generation.
Signed-off-by: Anderson Briglia <anderson.briglia@openbossa.org>
Signed-off-by: Anderson Lizardo <anderson.lizardo@openbossa.org>
Signed-off-by: Bruna Moreira <bruna.moreira@openbossa.org>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

net/bluetooth/smp.c

@@ -24,6 +24,123 @@
 #include <net/bluetooth/hci_core.h>
 #include <net/bluetooth/l2cap.h>
 #include <net/bluetooth/smp.h>
+#include <linux/crypto.h>
+#include <crypto/b128ops.h>
+
+static inline void swap128(u8 src[16], u8 dst[16])
+{
+	int i;
+	for (i = 0; i < 16; i++)
+		dst[15 - i] = src[i];
+}
+
+static inline void swap56(u8 src[7], u8 dst[7])
+{
+	int i;
+	for (i = 0; i < 7; i++)
+		dst[6 - i] = src[i];
+}
+
+static int smp_e(struct crypto_blkcipher *tfm, const u8 *k, u8 *r)
+{
+	struct blkcipher_desc desc;
+	struct scatterlist sg;
+	int err, iv_len;
+	unsigned char iv[128];
+
+	if (tfm == NULL) {
+		BT_ERR("tfm %p", tfm);
+		return -EINVAL;
+	}
+
+	desc.tfm = tfm;
+	desc.flags = 0;
+
+	err = crypto_blkcipher_setkey(tfm, k, 16);
+	if (err) {
+		BT_ERR("cipher setkey failed: %d", err);
+		return err;
+	}
+
+	sg_init_one(&sg, r, 16);
+
+	iv_len = crypto_blkcipher_ivsize(tfm);
+	if (iv_len) {
+		memset(&iv, 0xff, iv_len);
+		crypto_blkcipher_set_iv(tfm, iv, iv_len);
+	}
+
+	err = crypto_blkcipher_encrypt(&desc, &sg, &sg, 16);
+	if (err)
+		BT_ERR("Encrypt data error %d", err);
+
+	return err;
+}
+
+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])
+{
+	u8 p1[16], p2[16];
+	int err;
+
+	memset(p1, 0, 16);
+
+	/* p1 = pres || preq || _rat || _iat */
+	swap56(pres, p1);
+	swap56(preq, p1 + 7);
+	p1[14] = _rat;
+	p1[15] = _iat;
+
+	memset(p2, 0, 16);
+
+	/* p2 = padding || ia || ra */
+	baswap((bdaddr_t *) (p2 + 4), ia);
+	baswap((bdaddr_t *) (p2 + 10), ra);
+
+	/* res = r XOR p1 */
+	u128_xor((u128 *) res, (u128 *) r, (u128 *) p1);
+
+	/* res = e(k, res) */
+	err = smp_e(tfm, k, res);
+	if (err) {
+		BT_ERR("Encrypt data error");
+		return err;
+	}
+
+	/* res = res XOR p2 */
+	u128_xor((u128 *) res, (u128 *) res, (u128 *) p2);
+
+	/* res = e(k, res) */
+	err = smp_e(tfm, k, res);
+	if (err)
+		BT_ERR("Encrypt data error");
+
+	return err;
+}
+
+static int smp_s1(struct crypto_blkcipher *tfm, u8 k[16],
+			u8 r1[16], u8 r2[16], u8 _r[16])
+{
+	int err;
+
+	/* Just least significant octets from r1 and r2 are considered */
+	memcpy(_r, r1 + 8, 8);
+	memcpy(_r + 8, r2 + 8, 8);
+
+	err = smp_e(tfm, k, _r);
+	if (err)
+		BT_ERR("Encrypt data error");
+
+	return err;
+}
+
+static int smp_rand(u8 *buf)
+{
+	get_random_bytes(buf, 16);
+
+	return 0;
+}
 
 static struct sk_buff *smp_build_cmd(struct l2cap_conn *conn, u8 code,
 						u16 dlen, void *data)