From e16c6d3b62d0d7d5885255cf9cef686a2415330d Mon Sep 17 00:00:00 2001
From: Alain Michaud <alainm@chromium.org>
Date: Tue, 10 Mar 2020 02:35:18 +0000
Subject: [PATCH 2/4] HID accepts bonded device connections only.

This change adds a configuration for platforms to choose a more secure
posture for the HID profile.  While some older mice are known to not
support pairing or encryption, some platform may choose a more secure
posture by requiring the device to be bonded  and require the
connection to be encrypted when bonding is required.

Reference:
https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00352.html
---
 profiles/input/device.c   | 23 ++++++++++++++++++++++-
 profiles/input/device.h   |  1 +
 profiles/input/input.conf |  8 ++++++++
 profiles/input/manager.c  | 13 ++++++++++++-
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/profiles/input/device.c b/profiles/input/device.c
index 8461478..3abd2f5 100644
--- a/profiles/input/device.c
+++ b/profiles/input/device.c
@@ -91,6 +91,7 @@ struct input_device {
 
 static int idle_timeout = 0;
 static bool uhid_enabled = false;
+static bool classic_bonded_only = false;
 
 void input_set_idle_timeout(int timeout)
 {
@@ -102,6 +103,11 @@ void input_enable_userspace_hid(bool state)
 	uhid_enabled = state;
 }
 
+void input_set_classic_bonded_only(bool state)
+{
+	classic_bonded_only = state;
+}
+
 static void input_device_enter_reconnect_mode(struct input_device *idev);
 static int connection_disconnect(struct input_device *idev, uint32_t flags);
 
@@ -969,8 +975,18 @@ static int hidp_add_connection(struct input_device *idev)
 	if (device_name_known(idev->device))
 		device_get_name(idev->device, req->name, sizeof(req->name));
 
+	/* Make sure the device is bonded if required */
+	if (classic_bonded_only && !device_is_bonded(idev->device,
+				btd_device_get_bdaddr_type(idev->device))) {
+		error("Rejected connection from !bonded device %s", dst_addr);
+		goto cleanup;
+	}
+
 	/* Encryption is mandatory for keyboards */
-	if (req->subclass & 0x40) {
+	/* Some platforms may choose to require encryption for all devices */
+	/* Note that this only matters for pre 2.1 devices as otherwise the */
+	/* device is encrypted by default by the lower layers */
+	if (classic_bonded_only || req->subclass & 0x40) {
 		if (!bt_io_set(idev->intr_io, &gerr,
 					BT_IO_OPT_SEC_LEVEL, BT_IO_SEC_MEDIUM,
 					BT_IO_OPT_INVALID)) {
@@ -1202,6 +1218,11 @@ static void input_device_enter_reconnect_mode(struct input_device *idev)
 	DBG("path=%s reconnect_mode=%s", idev->path,
 				reconnect_mode_to_string(idev->reconnect_mode));
 
+	/* Make sure the device is bonded if required */
+	if (classic_bonded_only && !device_is_bonded(idev->device,
+				btd_device_get_bdaddr_type(idev->device)))
+		return;
+
 	/* Only attempt an auto-reconnect when the device is required to
 	 * accept reconnections from the host.
 	 */
diff --git a/profiles/input/device.h b/profiles/input/device.h
index 51a9aee..3044db6 100644
--- a/profiles/input/device.h
+++ b/profiles/input/device.h
@@ -29,6 +29,7 @@ struct input_conn;
 
 void input_set_idle_timeout(int timeout);
 void input_enable_userspace_hid(bool state);
+void input_set_classic_bonded_only(bool state);
 
 int input_device_register(struct btd_service *service);
 void input_device_unregister(struct btd_service *service);
diff --git a/profiles/input/input.conf b/profiles/input/input.conf
index 3e1d65a..166aff4 100644
--- a/profiles/input/input.conf
+++ b/profiles/input/input.conf
@@ -11,3 +11,11 @@
 # Enable HID protocol handling in userspace input profile
 # Defaults to false (HIDP handled in HIDP kernel module)
 #UserspaceHID=true
+
+# Limit HID connections to bonded devices
+# The HID Profile does not specify that devices must be bonded, however some
+# platforms may want to make sure that input connections only come from bonded
+# device connections. Several older mice have been known for not supporting
+# pairing/encryption.
+# Defaults to false to maximize device compatibility.
+#ClassicBondedOnly=true
diff --git a/profiles/input/manager.c b/profiles/input/manager.c
index 1d31b06..5cd27b8 100644
--- a/profiles/input/manager.c
+++ b/profiles/input/manager.c
@@ -96,7 +96,7 @@ static int input_init(void)
 	config = load_config_file(CONFIGDIR "/input.conf");
 	if (config) {
 		int idle_timeout;
-		gboolean uhid_enabled;
+		gboolean uhid_enabled, classic_bonded_only;
 
 		idle_timeout = g_key_file_get_integer(config, "General",
 							"IdleTimeout", &err);
@@ -114,6 +114,17 @@ static int input_init(void)
 			input_enable_userspace_hid(uhid_enabled);
 		} else
 			g_clear_error(&err);
+
+		classic_bonded_only = g_key_file_get_boolean(config, "General",
+						"ClassicBondedOnly", &err);
+
+		if (!err) {
+			DBG("input.conf: ClassicBondedOnly=%s",
+					classic_bonded_only ? "true" : "false");
+			input_set_classic_bonded_only(classic_bonded_only);
+		} else
+			g_clear_error(&err);
+
 	}
 
 	btd_profile_register(&input_profile);
-- 
1.8.3.1

