[RFC 07/15] Bluetooth: Fix SM pairing parameters negotiation

[Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxxxxxx>]

Before implementing SM key distribution, the pairing features
exchange must be better negotiated, taking into account some
features of the host and connection requirements.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxxxxxx>
---
 net/bluetooth/smp.c |   42 ++++++++++++++++++++++++++++++++----------
 1 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 1f1b318..3d2fb13 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -201,14 +201,36 @@ static __u8 seclevel_to_authreq(__u8 level)
 }
 
 static void build_pairing_cmd(struct l2cap_conn *conn,
-				struct smp_cmd_pairing *cmd, __u8 authreq)
+				struct smp_cmd_pairing *req,
+				struct smp_cmd_pairing *rsp,
+				__u8 authreq)
 {
-	cmd->io_capability = conn->hcon->io_capability;
-	cmd->oob_flag = SMP_OOB_NOT_PRESENT;
-	cmd->max_key_size = SMP_MAX_ENC_KEY_SIZE;
-	cmd->init_key_dist = SMP_DIST_ENC_KEY | SMP_DIST_ID_KEY | SMP_DIST_SIGN;
-	cmd->resp_key_dist = SMP_DIST_ENC_KEY | SMP_DIST_ID_KEY | SMP_DIST_SIGN;
-	cmd->auth_req = authreq;
+	u8 all_keys = SMP_DIST_ENC_KEY | SMP_DIST_ID_KEY |
+						SMP_DIST_SIGN;
+	u8 dist_keys;
+
+	dist_keys = 0;
+	if (test_bit(HCI_PAIRABLE, &conn->hcon->hdev->flags)) {
+		dist_keys = SMP_DIST_ENC_KEY;
+		authreq |= SMP_AUTH_BONDING;
+	}
+
+	if (rsp == NULL) {
+		req->io_capability = conn->hcon->io_capability;
+		req->oob_flag = SMP_OOB_NOT_PRESENT;
+		req->max_key_size = SMP_MAX_ENC_KEY_SIZE;
+		req->init_key_dist = dist_keys;
+		req->resp_key_dist = all_keys;
+		req->auth_req = authreq;
+		return;
+	}
+
+	rsp->io_capability = conn->hcon->io_capability;
+	rsp->oob_flag = SMP_OOB_NOT_PRESENT;
+	rsp->max_key_size = SMP_MAX_ENC_KEY_SIZE;
+	rsp->init_key_dist = req->init_key_dist & all_keys;
+	rsp->resp_key_dist = req->resp_key_dist & dist_keys;
+	rsp->auth_req = authreq;
 }
 
 static u8 check_enc_key_size(struct l2cap_conn *conn, __u8 max_key_size)
@@ -237,7 +259,7 @@ static u8 smp_cmd_pairing_req(struct l2cap_conn *conn, struct sk_buff *skb)
 		return SMP_OOB_NOT_AVAIL;
 
 	/* We didn't start the pairing, so no requirements */
-	build_pairing_cmd(conn, &rsp, SMP_AUTH_NONE);
+	build_pairing_cmd(conn, req, &rsp, SMP_AUTH_NONE);
 
 	key_size = min(req->max_key_size, rsp.max_key_size);
 	if (check_enc_key_size(conn, key_size))
@@ -422,7 +444,7 @@ static u8 smp_cmd_security_req(struct l2cap_conn *conn, struct sk_buff *skb)
 	skb_pull(skb, sizeof(*rp));
 
 	memset(&cp, 0, sizeof(cp));
-	build_pairing_cmd(conn, &cp, rp->auth_req);
+	build_pairing_cmd(conn, &cp, NULL, rp->auth_req);
 
 	conn->preq[0] = SMP_CMD_PAIRING_REQ;
 	memcpy(&conn->preq[1], &cp, sizeof(cp));
@@ -461,7 +483,7 @@ int smp_conn_security(struct l2cap_conn *conn, __u8 sec_level)
 	if (hcon->link_mode & HCI_LM_MASTER) {
 		struct smp_cmd_pairing cp;
 
-		build_pairing_cmd(conn, &cp, authreq);
+		build_pairing_cmd(conn, &cp, NULL, authreq);
 		conn->preq[0] = SMP_CMD_PAIRING_REQ;
 		memcpy(&conn->preq[1], &cp, sizeof(cp));
 
-- 
1.7.4.1

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