Bluetooth: debugfs option to unset MITM flag

The BT qualification test SM/MAS/PKE/BV-01-C needs us to turn off
the MITM flag when pairing, and at the same time also set the io
capability to something other than no input no output.

Currently the MITM flag is only unset when the io capability is set
to no input no output, therefore the test cannot be executed.

This patch introduces a debugfs option to force MITM flag to be
turned off.
Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/hci.h

@@ -298,6 +298,7 @@ enum {
 	HCI_FORCE_STATIC_ADDR,
 	HCI_LL_RPA_RESOLUTION,
 	HCI_CMD_PENDING,
+	HCI_FORCE_NO_MITM,
 
 	__HCI_NUM_FLAGS,
 };

net/bluetooth/hci_debugfs.c

@@ -1075,6 +1075,50 @@ DEFINE_SIMPLE_ATTRIBUTE(auth_payload_timeout_fops,
 			auth_payload_timeout_get,
 			auth_payload_timeout_set, "%llu\n");
 
+static ssize_t force_no_mitm_read(struct file *file,
+				  char __user *user_buf,
+				  size_t count, loff_t *ppos)
+{
+	struct hci_dev *hdev = file->private_data;
+	char buf[3];
+
+	buf[0] = hci_dev_test_flag(hdev, HCI_FORCE_NO_MITM) ? 'Y' : 'N';
+	buf[1] = '\n';
+	buf[2] = '\0';
+	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
+}
+
+static ssize_t force_no_mitm_write(struct file *file,
+				   const char __user *user_buf,
+				   size_t count, loff_t *ppos)
+{
+	struct hci_dev *hdev = file->private_data;
+	char buf[32];
+	size_t buf_size = min(count, (sizeof(buf) - 1));
+	bool enable;
+
+	if (copy_from_user(buf, user_buf, buf_size))
+		return -EFAULT;
+
+	buf[buf_size] = '\0';
+	if (strtobool(buf, &enable))
+		return -EINVAL;
+
+	if (enable == hci_dev_test_flag(hdev, HCI_FORCE_NO_MITM))
+		return -EALREADY;
+
+	hci_dev_change_flag(hdev, HCI_FORCE_NO_MITM);
+
+	return count;
+}
+
+static const struct file_operations force_no_mitm_fops = {
+	.open		= simple_open,
+	.read		= force_no_mitm_read,
+	.write		= force_no_mitm_write,
+	.llseek		= default_llseek,
+};
+
 DEFINE_QUIRK_ATTRIBUTE(quirk_strict_duplicate_filter,
 		       HCI_QUIRK_STRICT_DUPLICATE_FILTER);
 DEFINE_QUIRK_ATTRIBUTE(quirk_simultaneous_discovery,
@@ -1134,6 +1178,8 @@ void hci_debugfs_create_le(struct hci_dev *hdev)
 			    &max_key_size_fops);
 	debugfs_create_file("auth_payload_timeout", 0644, hdev->debugfs, hdev,
 			    &auth_payload_timeout_fops);
+	debugfs_create_file("force_no_mitm", 0644, hdev->debugfs, hdev,
+			    &force_no_mitm_fops);
 
 	debugfs_create_file("quirk_strict_duplicate_filter", 0644,
 			    hdev->debugfs, hdev,

net/bluetooth/smp.c

@@ -2393,12 +2393,17 @@ int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
 			authreq |= SMP_AUTH_CT2;
 	}
 
-	/* Require MITM if IO Capability allows or the security level
-	 * requires it.
+	/* Don't attempt to set MITM if setting is overridden by debugfs
+	 * Needed to pass certification test SM/MAS/PKE/BV-01-C
 	 */
-	if (hcon->io_capability != HCI_IO_NO_INPUT_OUTPUT ||
-	    hcon->pending_sec_level > BT_SECURITY_MEDIUM)
-		authreq |= SMP_AUTH_MITM;
+	if (!hci_dev_test_flag(hcon->hdev, HCI_FORCE_NO_MITM)) {
+		/* Require MITM if IO Capability allows or the security level
+		 * requires it.
+		 */
+		if (hcon->io_capability != HCI_IO_NO_INPUT_OUTPUT ||
+		    hcon->pending_sec_level > BT_SECURITY_MEDIUM)
+			authreq |= SMP_AUTH_MITM;
+	}
 
 	if (hcon->role == HCI_ROLE_MASTER) {
 		struct smp_cmd_pairing cp;