Add support for requiring min key size for access GATT characteristics

This allows to configure bluetoothd to require minimum encryption key size when accessing GATT server characteristics. It is a global configuration option affecting whole GATT database.
---
V5: No changes, just rebase on top of master.

 peripheral/gatt.c        |  2 +-
 src/adapter.c            | 45 ++++++++++++++++++++++++++++++++-------------
src/device.c             | 15 +++++++++++++--
 src/device.h             |  1 +
 src/hcid.h               |  2 ++
 src/main.c               | 17 ++++++++++++++---
 src/main.conf            |  5 +++++
 src/shared/att.c         | 22 +++++++++++++++++++---
 src/shared/att.h         |  3 ++-
 src/shared/gatt-client.c |  4 ++--
 src/shared/gatt-server.c | 47
+++++++++++++++++++++++++++++++++++++++-------- src/shared/gatt-server.h | 
3 ++-
 tools/btgatt-server.c    |  2 +-
 unit/test-gatt.c         |  2 +-
 14 files changed, 134 insertions(+), 36 deletions(-)

peripheral/gatt.c +1 -1

index 5ae19a8e5..08541c424 100644
@@ -128,7 +128,7 @@ static struct gatt_conn *gatt_conn_new(int fd)
 
 	bt_att_set_security(conn->att, BT_SECURITY_MEDIUM);
 
-	conn->gatt = bt_gatt_server_new(gatt_db, conn->att, mtu);
+	conn->gatt = bt_gatt_server_new(gatt_db, conn->att, mtu, 0);
 	if (!conn->gatt) {
 		fprintf(stderr, "Failed to create GATT server\n");
 		bt_att_unref(conn->att);

src/adapter.c +31 -13

index 6d7d61504..6b9222bcf 100644
@@ -3441,25 +3441,27 @@ failed:
 	return ltk;
 }
 
-static GSList *get_ltk_info(GKeyFile *key_file, const char *peer,
+static struct smp_ltk_info *get_ltk_info(GKeyFile *key_file, const char
 *peer, +							uint8_t bdaddr_type)
+{
+	DBG("%s", peer);
+
+	return get_ltk(key_file, peer, bdaddr_type, "LongTermKey");
+}
+
+static struct smp_ltk_info *get_slave_ltk_info(GKeyFile *key_file,
+							const char *peer,
 							uint8_t bdaddr_type)
 {
 	struct smp_ltk_info *ltk;
-	GSList *l = NULL;
 
 	DBG("%s", peer);
 
-	ltk = get_ltk(key_file, peer, bdaddr_type, "LongTermKey");
-	if (ltk)
-		l = g_slist_append(l, ltk);
-
 	ltk = get_ltk(key_file, peer, bdaddr_type, "SlaveLongTermKey");
-	if (ltk) {
+	if (ltk)
 		ltk->master = false;
-		l = g_slist_append(l, ltk);
-	}
 
-	return l;
+	return ltk;
 }
 
 static struct irk_info *get_irk_info(GKeyFile *key_file, const char *peer,

@@ -4019,7 +4021,9 @@ static void load_devices(struct btd_adapter *adapter)
 		char filename[PATH_MAX];
 		GKeyFile *key_file;
 		struct link_key_info *key_info;
-		GSList *list, *ltk_info;
+		struct smp_ltk_info *ltk_info;
+		struct smp_ltk_info *slave_ltk_info;
+		GSList *list;
 		struct irk_info *irk_info;
 		struct conn_param *param;
 		uint8_t bdaddr_type;

@@ -4044,7 +4048,13 @@ static void load_devices(struct btd_adapter *adapter)
 bdaddr_type = get_le_addr_type(key_file);
 
 		ltk_info = get_ltk_info(key_file, entry->d_name, bdaddr_type);
-		ltks = g_slist_concat(ltks, ltk_info);
+		if (ltk_info)
+			ltks = g_slist_append(ltks, ltk_info);
+
+		slave_ltk_info = get_slave_ltk_info(key_file, entry->d_name,
+								bdaddr_type);
+		if (slave_ltk_info)
+			ltks = g_slist_append(ltks, slave_ltk_info);
 
 		irk_info = get_irk_info(key_file, entry->d_name, bdaddr_type);
 		if (irk_info)

@@ -4079,9 +4089,16 @@ device_exist:
 			device_set_bonded(device, BDADDR_BREDR);
 		}
 
-		if (ltk_info) {
+		if (ltk_info || slave_ltk_info) {
 			device_set_paired(device, bdaddr_type);
 			device_set_bonded(device, bdaddr_type);
+
+			if (ltk_info)
+				device_set_ltk_enc_size(device,
+							ltk_info->enc_size);
+			else if (slave_ltk_info)
+				device_set_ltk_enc_size(device,
+						slave_ltk_info->enc_size);
 		}
 
 free:

@@ -7464,6 +7481,8 @@ static void new_long_term_key_callback(uint16_t index,
 uint16_t length, device_set_bonded(device, addr->type);
 	}
 
+	device_set_ltk_enc_size(device, ev->key.enc_size);
+
 	bonding_complete(adapter, &addr->bdaddr, addr->type, 0);
 }
 

src/device.c +13 -2

index bf5441543..780458fd7 100644
@@ -243,6 +243,7 @@ struct btd_device {
 
 	struct csrk_info *local_csrk;
 	struct csrk_info *remote_csrk;
+	uint8_t ltk_enc_size;
 
 	sdp_list_t	*tmp_records;
 

@@ -1460,6 +1461,12 @@ bool device_is_disconnecting(struct btd_device
 *device) return device->disconn_timer > 0;
 }
 
+void device_set_ltk_enc_size(struct btd_device *device, uint8_t enc_size)
+{
+	device->ltk_enc_size = enc_size;
+	bt_att_set_enc_key_size(device->att, device->ltk_enc_size);
+}
+
 static void device_set_auto_connect(struct btd_device *device, gboolean
 enable) {
 	char addr[18];

@@ -4837,10 +4844,14 @@ static void gatt_server_init(struct btd_device
 *device,
 
 	gatt_server_cleanup(device);
 
-	device->server = bt_gatt_server_new(db, device->att, device->att_mtu);
-	if (!device->server)
+	device->server = bt_gatt_server_new(db, device->att, device->att_mtu,
+						main_opts.min_enc_key_size);
+	if (!device->server) {
 		error("Failed to initialize bt_gatt_server");
+		return;
+	}
 
+	bt_att_set_enc_key_size(device->att, device->ltk_enc_size);
 	bt_gatt_server_set_debug(device->server, gatt_debug, NULL, NULL);
 

src/device.c +0 -0

 	btd_gatt_database_att_connected(database, device->att);

src/device.h +0 -0

index bc046f780..306c813fc 100644
@@ -130,6 +130,7 @@ void device_add_connection(struct btd_device *dev,

uint8_t bdaddr_type); void device_remove_connection(struct btd_device *device, uint8_t bdaddr_type); void device_request_disconnect(struct btd_device *device, DBusMessage *msg); bool device_is_disconnecting(struct btd_device *device);
+void device_set_ltk_enc_size(struct btd_device *device, uint8_t enc_size);

typedef void (*disconnect_watch) (struct btd_device *device, gboolean
removal, void *user_data);

src/hcid.h +2 -0

index 62e2bd606..2c2b89d9c 100644
@@ -54,6 +54,8 @@ struct main_opts {
 
 	bt_mode_t	mode;
 	bt_gatt_cache_t gatt_cache;
+
+	uint8_t		min_enc_key_size;
 };
 
 extern struct main_opts main_opts;

src/main.c +14 -3

index 21f0b14a4..7e6af42cd 100644
@@ -103,6 +103,7 @@ static const char *policy_options[] = {
 
 static const char *gatt_options[] = {
 	"Cache",
+	"MinEncKeySize",
 	NULL
 };
 

@@ -402,12 +403,22 @@ static void parse_config(GKeyFile *config)
 	if (err) {
 		g_clear_error(&err);
 		main_opts.gatt_cache = BT_GATT_CACHE_ALWAYS;
-		return;
+	} else {
+		main_opts.gatt_cache = parse_gatt_cache(str);
+		g_free(str);
 	}
 
-	main_opts.gatt_cache = parse_gatt_cache(str);
+	val = g_key_file_get_integer(config, "GATT",
+						"MinEncKeySize", &err);
+	if (err) {
+		DBG("%s", err->message);
+		g_clear_error(&err);
+	} else {
+		DBG("MinEncKeySize=%d", val);
 
-	g_free(str);
+		if (val >=7 && val <= 16)
+			main_opts.min_enc_key_size = val;
+	}
 }
 
 static void init_defaults(void)

src/main.conf +1 -0

index 21986b386..cbae32ec5 100644
@@ -77,6 +77,11 @@
 # Default: always
 #Cache = always
 
+# Minimum required Encryption Key Size for accessing secured

characteristics. +# Possible values: 0 and 7-16. 0 means don't care.

src/main.conf +3 -0

+# Defaults to 0
+# MinEncKeySize = 0
+
 [Policy]
 #
 # The ReconnectUUIDs defines the set of remote services that should try

src/shared/att.c +19 -3

index 0aab246d6..8bf3f4611 100644
@@ -55,6 +55,7 @@ struct bt_att {
 	struct io *io;
 	bool io_on_l2cap;
 	int io_sec_level;		/* Only used for non-L2CAP */
+	uint8_t enc_size;
 
 	struct queue *req_queue;	/* Queued ATT protocol requests */
 	struct att_send_op *pending_req;

@@ -602,7 +603,7 @@ static bool change_security(struct bt_att *att, uint8_t
 ecode) if (att->io_sec_level != BT_ATT_SECURITY_AUTO)
 		return false;
 
-	security = bt_att_get_security(att);
+	security = bt_att_get_security(att, NULL);
 
 	if (ecode == BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION &&
 					security < BT_ATT_SECURITY_MEDIUM) {

@@ -1454,7 +1455,7 @@ bool bt_att_unregister_all(struct bt_att *att)
 	return true;
 }
 
-int bt_att_get_security(struct bt_att *att)
+int bt_att_get_security(struct bt_att *att, uint8_t *enc_size)
 {
 	struct bt_security sec;
 	socklen_t len;

@@ -1462,14 +1463,21 @@ int bt_att_get_security(struct bt_att *att)
 	if (!att)
 		return -EINVAL;
 
-	if (!att->io_on_l2cap)
+	if (!att->io_on_l2cap) {
+		if (enc_size)
+			*enc_size = att->enc_size;
+
 		return att->io_sec_level;
+	}
 
 	memset(&sec, 0, sizeof(sec));
 	len = sizeof(sec);
 	if (getsockopt(att->fd, SOL_BLUETOOTH, BT_SECURITY, &sec, &len) < 0)
 		return -EIO;
 
+	if (enc_size)
+		*enc_size = att->enc_size;
+
 	return sec.level;
 }
 

@@ -1496,6 +1504,14 @@ bool bt_att_set_security(struct bt_att *att, int
 level) return true;
 }
 
+void bt_att_set_enc_key_size(struct bt_att *att, uint8_t enc_size)
+{
+	if (!att)
+		return;
+
+	att->enc_size = enc_size;
+}
+
 static bool sign_set_key(struct sign_info **sign, uint8_t key[16],
 				bt_att_counter_func_t func, void *user_data)
 {

src/shared/att.h +2 -1

index 7bffee7d6..49d93269b 100644
@@ -84,8 +84,9 @@ bool bt_att_unregister_disconnect(struct bt_att *att,
 unsigned int id);
 
 bool bt_att_unregister_all(struct bt_att *att);
 
-int bt_att_get_security(struct bt_att *att);
+int bt_att_get_security(struct bt_att *att, uint8_t *enc_size);
 bool bt_att_set_security(struct bt_att *att, int level);
+void bt_att_set_enc_key_size(struct bt_att *att, uint8_t enc_size);
 
 bool bt_att_set_local_key(struct bt_att *att, uint8_t sign_key[16],

src/shared/att.h +0 -0

 			bt_att_counter_func_t func, void *user_data);

src/shared/gatt-client.c +2 -2

index 5721f3e5c..6b97ee70e 100644
@@ -2565,7 +2565,7 @@ unsigned int bt_gatt_client_write_without_response(
 
 	/* Only use signed write if unencrypted */
 	if (signed_write) {
-		security = bt_att_get_security(client->att);
+		security = bt_att_get_security(client->att, NULL);
 		op = security > BT_SECURITY_LOW ?  BT_ATT_OP_WRITE_CMD :
 						BT_ATT_OP_SIGNED_WRITE_CMD;
 	} else

@@ -3281,5 +3281,5 @@ int bt_gatt_client_get_security(struct bt_gatt_client
 *client) if (!client)
 		return -1;
 
-	return bt_att_get_security(client->att);
+	return bt_att_get_security(client->att, NULL);
 }

src/shared/gatt-server.c +39 -8

index faa56abeb..4b554f665 100644
@@ -103,6 +103,8 @@ struct bt_gatt_server {
 	unsigned int prep_write_id;
 	unsigned int exec_write_id;
 
+	uint8_t min_enc_size;
+
 	struct queue *prep_queue;
 	unsigned int max_prep_queue_len;
 

@@ -379,9 +381,18 @@ done:
 	process_read_by_type(op);
 }
 
+static bool check_min_key_size(uint8_t min_size, uint8_t size)
+{
+	if (!min_size || !size)
+		return true;
+
+	return min_size <= size;
+}
+
 static uint8_t check_permissions(struct bt_gatt_server *server,
 				struct gatt_db_attribute *attr, uint32_t mask)
 {
+	uint8_t enc_size;
 	uint32_t perm;
 	int security;
 

@@ -397,15 +408,33 @@ static uint8_t check_permissions(struct bt_gatt_server
 *server, if (!perm)
 		return 0;
 
-	security = bt_att_get_security(server->att);
-	if (perm & BT_ATT_PERM_SECURE && security < BT_ATT_SECURITY_FIPS)
-		return BT_ATT_ERROR_AUTHENTICATION;
+	security = bt_att_get_security(server->att, &enc_size);
+	if (security < 0)
+		return BT_ATT_ERROR_UNLIKELY;
 
-	if (perm & BT_ATT_PERM_AUTHEN && security < BT_ATT_SECURITY_HIGH)
-		return BT_ATT_ERROR_AUTHENTICATION;
+	if (perm & BT_ATT_PERM_SECURE) {
+		if (security < BT_ATT_SECURITY_FIPS)
+			return BT_ATT_ERROR_AUTHENTICATION;
 
-	if (perm & BT_ATT_PERM_ENCRYPT && security < BT_ATT_SECURITY_MEDIUM)
-		return BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION;
+		if (!check_min_key_size(server->min_enc_size, enc_size))
+			return BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE;
+	}
+
+	if (perm & BT_ATT_PERM_AUTHEN) {
+		if (security < BT_ATT_SECURITY_HIGH)
+			return BT_ATT_ERROR_AUTHENTICATION;
+
+		if (!check_min_key_size(server->min_enc_size, enc_size))
+			return BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE;
+	}
+
+	if (perm & BT_ATT_PERM_ENCRYPT) {
+		if (security < BT_ATT_SECURITY_MEDIUM)
+			return BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION;
+
+		if (!check_min_key_size(server->min_enc_size, enc_size))
+			return BT_ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE;
+	}
 
 	return 0;
 }

@@ -1481,7 +1510,8 @@ static bool gatt_server_register_att_handlers(struct
 bt_gatt_server *server) }
 
 struct bt_gatt_server *bt_gatt_server_new(struct gatt_db *db,
-					struct bt_att *att, uint16_t mtu)
+					struct bt_att *att, uint16_t mtu,
+					uint8_t min_enc_size)
 {
 	struct bt_gatt_server *server;
 

@@ -1494,6 +1524,7 @@ struct bt_gatt_server *bt_gatt_server_new(struct
 gatt_db *db, server->mtu = MAX(mtu, BT_ATT_DEFAULT_LE_MTU);
 	server->max_prep_queue_len = DEFAULT_MAX_PREP_QUEUE_LEN;
 	server->prep_queue = queue_new();
+	server->min_enc_size = min_enc_size;
 
 	if (!gatt_server_register_att_handlers(server)) {
 		bt_gatt_server_free(server);

src/shared/gatt-server.h +2 -1

index 74a6c721e..d5d209350 100644
@@ -26,7 +26,8 @@
 struct bt_gatt_server;
 
 struct bt_gatt_server *bt_gatt_server_new(struct gatt_db *db,
-					struct bt_att *att, uint16_t mtu);
+					struct bt_att *att, uint16_t mtu,
+					uint8_t min_enc_size);
 uint16_t bt_gatt_server_get_mtu(struct bt_gatt_server *server);
 
 struct bt_gatt_server *bt_gatt_server_ref(struct bt_gatt_server *server);

tools/btgatt-server.c +1 -1

index fadaff2ad..89812bd75 100644
@@ -583,7 +583,7 @@ static struct server *server_create(int fd, uint16_t
 mtu, bool hr_visible) goto fail;
 	}
 
-	server->gatt = bt_gatt_server_new(server->db, server->att, mtu);
+	server->gatt = bt_gatt_server_new(server->db, server->att, mtu, 0);
 	if (!server->gatt) {
 		fprintf(stderr, "Failed to create GATT server\n");
 		goto fail;

unit/test-gatt.c +0 -0

index 5d79e94c0..c7e28f865 100644