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Date: Wed, 6 Apr 2011 20:26:32 -0300
From: "Gustavo F. Padovan" <padovan@profusion.mobi>
To: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Cc: linux-bluetooth@vger.kernel.org,
	Anderson Briglia <anderson.briglia@openbossa.org>,
	Anderson Lizardo <anderson.lizardo@openbossa.org>,
	Bruna Moreira <bruna.moreira@openbossa.org>
Subject: Re: [bluetooth-next 05/15] Bluetooth: LE SMP Cryptoolbox functions
Message-ID: <20110406232632.GC2228@joana>
References: <1302054716-24534-1-git-send-email-vinicius.gomes@openbossa.org>
 <1302054716-24534-6-git-send-email-vinicius.gomes@openbossa.org>
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Hi Vinicius,

* Vinicius Costa Gomes <vinicius.gomes@openbossa.org> [2011-04-05 22:51:46 -0300]:

> From: Anderson Briglia <anderson.briglia@openbossa.org>
> 
> 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>
> ---
>  net/bluetooth/smp.c |  122 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 122 insertions(+), 0 deletions(-)
> 
> diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
> index 42aed82..58047e8 100644
> --- a/net/bluetooth/smp.c
> +++ b/net/bluetooth/smp.c
> @@ -24,6 +24,128 @@
>  #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], pair[7];
> +	bdaddr_t addr;
> +	int err;
> +
> +	/* p1 = pres || preq || _rat || _iat */
> +	memset(p1, 0, 16);
> +	swap56(pres, pair);
> +
> +	memcpy(p1, pair, 7);
> +	swap56(preq, pair);
> +
> +	memcpy(p1 + 7, pair, 7);

	swap56(pres, p1)
	swap56(preq, pi + 7)

> +	*(p1 + 14) = _rat;
> +	*(p1 + 15) = _iat;

Isn't p1[14] = _rat better?

btw, if fill all 16 bytes here, there is no need for a memset(p1)

> +
> +	/* p2 = padding || ia || ra */
> +	memset(p2, 0, 16);
> +	baswap(&addr, ia);
> +	memcpy(p2 + 4, &addr, 6);
> +	baswap(&addr, ra);
> +	memcpy(p2 + 10, &addr, 6);

baswap(p2 + 4, ia) should have the same effect.

> +	/* 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)

This can be void.

> +{
> +	get_random_bytes(buf, 16);
> +
> +	return 0;
> +}
>  

-- 
Gustavo F. Padovan
http://profusion.mobi