Bluetooth: Add support for handling signature resolving keys

The connection signature resolving key (CSRK) is used for attribute
protocol signed write procedures. This change generates a new local
key during pairing and requests the peer key as well.

Newly generated key and received key will be provided to userspace
using the New Signature Resolving Key management event.

The Master CSRK can be used for verification of remote signed write
PDUs and the Slave CSRK can be used for sending signed write PDUs
to the remote device.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

1 files changed, 62 insertions, 5 deletions

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index f886bcae1b7e..fc652592daf6 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -273,8 +273,8 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 	u8 local_dist = 0, remote_dist = 0;
 
 	if (test_bit(HCI_PAIRABLE, &conn->hcon->hdev->dev_flags)) {
-		local_dist = SMP_DIST_ENC_KEY;
-		remote_dist = SMP_DIST_ENC_KEY;
+		local_dist = SMP_DIST_ENC_KEY | SMP_DIST_SIGN;
+		remote_dist = SMP_DIST_ENC_KEY | SMP_DIST_SIGN;
 		authreq |= SMP_AUTH_BONDING;
 	} else {
 		authreq &= ~SMP_AUTH_BONDING;
@@ -596,6 +596,9 @@ void smp_chan_destroy(struct l2cap_conn *conn)
 	complete = test_bit(SMP_FLAG_COMPLETE, &smp->smp_flags);
 	mgmt_smp_complete(conn->hcon, complete);
 
+	kfree(smp->csrk);
+	kfree(smp->slave_csrk);
+
 	/* If pairing failed clean up any keys we might have */
 	if (!complete) {
 		if (smp->ltk) {
@@ -1065,6 +1068,41 @@ static int smp_cmd_ident_addr_info(struct l2cap_conn *conn,
 	return 0;
 }
 
+static int smp_cmd_sign_info(struct l2cap_conn *conn, struct sk_buff *skb)
+{
+	struct smp_cmd_sign_info *rp = (void *) skb->data;
+	struct smp_chan *smp = conn->smp_chan;
+	struct hci_dev *hdev = conn->hcon->hdev;
+	struct smp_csrk *csrk;
+
+	BT_DBG("conn %p", conn);
+
+	if (skb->len < sizeof(*rp))
+		return SMP_UNSPECIFIED;
+
+	/* Ignore this PDU if it wasn't requested */
+	if (!(smp->remote_key_dist & SMP_DIST_SIGN))
+		return 0;
+
+	/* Mark the information as received */
+	smp->remote_key_dist &= ~SMP_DIST_SIGN;
+
+	skb_pull(skb, sizeof(*rp));
+
+	hci_dev_lock(hdev);
+	csrk = kzalloc(sizeof(*csrk), GFP_KERNEL);
+	if (csrk) {
+		csrk->master = 0x01;
+		memcpy(csrk->val, rp->csrk, sizeof(csrk->val));
+	}
+	smp->csrk = csrk;
+	if (!(smp->remote_key_dist & SMP_DIST_SIGN))
+		smp_distribute_keys(conn);
+	hci_dev_unlock(hdev);
+
+	return 0;
+}
+
 int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb)
 {
 	struct hci_conn *hcon = conn->hcon;
@@ -1147,8 +1185,7 @@ int smp_sig_channel(struct l2cap_conn *conn, struct sk_buff *skb)
 		break;
 
 	case SMP_CMD_SIGN_INFO:
-		/* Just ignored */
-		reason = 0;
+		reason = smp_cmd_sign_info(conn, skb);
 		break;
 
 	default:
@@ -1176,6 +1213,18 @@ static void smp_notify_keys(struct l2cap_conn *conn)
 	if (smp->remote_irk)
 		mgmt_new_irk(hdev, smp->remote_irk);
 
+	if (smp->csrk) {
+		smp->csrk->bdaddr_type = hcon->dst_type;
+		bacpy(&smp->csrk->bdaddr, &hcon->dst);
+		mgmt_new_csrk(hdev, smp->csrk);
+	}
+
+	if (smp->slave_csrk) {
+		smp->slave_csrk->bdaddr_type = hcon->dst_type;
+		bacpy(&smp->slave_csrk->bdaddr, &hcon->dst);
+		mgmt_new_csrk(hdev, smp->slave_csrk);
+	}
+
 	if (smp->ltk) {
 		smp->ltk->bdaddr_type = hcon->dst_type;
 		bacpy(&smp->ltk->bdaddr, &hcon->dst);
@@ -1274,10 +1323,18 @@ int smp_distribute_keys(struct l2cap_conn *conn)
 
 	if (*keydist & SMP_DIST_SIGN) {
 		struct smp_cmd_sign_info sign;
+		struct smp_csrk *csrk;
 
-		/* Send a dummy key */
+		/* Generate a new random key */
 		get_random_bytes(sign.csrk, sizeof(sign.csrk));
 
+		csrk = kzalloc(sizeof(*csrk), GFP_KERNEL);
+		if (csrk) {
+			csrk->master = 0x00;
+			memcpy(csrk->val, sign.csrk, sizeof(csrk->val));
+		}
+		smp->slave_csrk = csrk;
+
 		smp_send_cmd(conn, SMP_CMD_SIGN_INFO, sizeof(sign), &sign);
 
 		*keydist &= ~SMP_DIST_SIGN;