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Date:   Mon,  2 Mar 2020 12:07:31 +0800
Message-Id: <20200302120658.Bluez.v3.1.I3c505b4307094eb7a6f2c5949125a17c89b2e099@changeid>
Mime-Version: 1.0
Subject: [Bluez PATCH v3] src/profile: Ensure class UUID matches before
 connecting profile
From:   Archie Pusaka <apusaka@google.com>
To:     linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     Archie Pusaka <apusaka@chromium.org>
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Sender: linux-bluetooth-owner@vger.kernel.org
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From: Archie Pusaka <apusaka@chromium.org>

According to bluetooth spec Ver 5.1, Vol 3, Part B, 4.7.2, there
might be multiple service records returned in a SDP Service Search
Attribute Response. Also, according to 2.5.2, the service pattern
can match any UUID contained within the service record, it doesn't
have to match only some specific attributes of the record.

Therefore, before using the service record to connect to any
profile, first we must check that the service class ID of the
service record matches with whatever UUID specified in the service
pattern we are looking for.

This patch checks the service class ID of the records against the
requested UUID whenever bt_search_service() is called and filter
out the ones that don't match. For the alternative where filtering
is not applied, use the method bt_search().

---

Changes in v3:
- Simplify sdp_client.c
- Add comment for the behavior when SDP record is missing the
  service class ID

Changes in v2:
- Move service class matching from profile.c to sdp_client.c
- Create function bt_search for searching without matching uuid
- Update device.c to use bt_search for L2CAP

 src/device.c     | 26 +++++++--------------
 src/sdp-client.c | 61 ++++++++++++++++++++++++++++++++++++++++++++----
 src/sdp-client.h |  3 +++
 3 files changed, 67 insertions(+), 23 deletions(-)

diff --git a/src/device.c b/src/device.c
index a8f4c22f3..c351a1562 100644
--- a/src/device.c
+++ b/src/device.c
@@ -4584,27 +4584,18 @@ static void update_bredr_services(struct browse_req *req, sdp_list_t *recs)
 
 	for (seq = recs; seq; seq = seq->next) {
 		sdp_record_t *rec = (sdp_record_t *) seq->data;
-		sdp_list_t *svcclass = NULL;
 		char *profile_uuid;
 
 		if (!rec)
 			break;
 
-		if (sdp_get_service_classes(rec, &svcclass) < 0)
-			continue;
-
-		/* Check for empty service classes list */
-		if (svcclass == NULL) {
-			DBG("Skipping record with no service classes");
-			continue;
-		}
+		/* If service class attribute is missing, svclass will be all
+		 * zero and the resulting uuid string will be NULL.
+		 */
+		profile_uuid = bt_uuid2string(&rec->svclass);
 
-		/* Extract the first element and skip the remainning */
-		profile_uuid = bt_uuid2string(svcclass->data);
-		if (!profile_uuid) {
-			sdp_list_free(svcclass, free);
+		if (!profile_uuid)
 			continue;
-		}
 
 		if (bt_uuid_strcmp(profile_uuid, PNP_UUID) == 0) {
 			uint16_t source, vendor, product, version;
@@ -4638,7 +4629,6 @@ static void update_bredr_services(struct browse_req *req, sdp_list_t *recs)
 
 next:
 		free(profile_uuid);
-		sdp_list_free(svcclass, free);
 	}
 
 	if (sdp_key_file) {
@@ -5352,9 +5342,9 @@ static int device_browse_sdp(struct btd_device *device, DBusMessage *msg)
 
 	req->sdp_flags = get_sdp_flags(device);
 
-	err = bt_search_service(btd_adapter_get_address(adapter),
-				&device->bdaddr, &uuid, browse_cb, req, NULL,
-				req->sdp_flags);
+	err = bt_search(btd_adapter_get_address(adapter),
+			&device->bdaddr, &uuid, browse_cb, req, NULL,
+			req->sdp_flags);
 	if (err < 0) {
 		browse_request_free(req);
 		return err;
diff --git a/src/sdp-client.c b/src/sdp-client.c
index 413cf30ec..b92a083af 100644
--- a/src/sdp-client.c
+++ b/src/sdp-client.c
@@ -143,6 +143,7 @@ struct search_context {
 	gpointer		user_data;
 	uuid_t			uuid;
 	guint			io_id;
+	gboolean		filter_svc_class;
 };
 
 static GSList *context_list = NULL;
@@ -195,6 +196,16 @@ static void search_completed_cb(uint8_t type, uint16_t status,
 		rsp += recsize;
 		bytesleft -= recsize;
 
+		/* Check whether service class ID matches some specified uuid.
+		 * If the record is missing service class ID, svclass will be
+		 * all zero, and thus will be unequal to the requested uuid.
+		 */
+		if (ctxt->filter_svc_class &&
+				sdp_uuid_cmp(&ctxt->uuid, &rec->svclass) != 0) {
+			sdp_record_free(rec);
+			continue;
+		}
+
 		recs = sdp_list_append(recs, rec);
 	} while (scanned < (ssize_t) size && bytesleft > 0);
 
@@ -338,7 +349,28 @@ static int create_search_context(struct search_context **ctxt,
 	return 0;
 }
 
-int bt_search_service(const bdaddr_t *src, const bdaddr_t *dst,
+static int create_search_context_full(struct search_context **ctxt,
+					const bdaddr_t *src,
+					const bdaddr_t *dst,
+					uuid_t *uuid, uint16_t flags,
+					void *user_data, bt_callback_t cb,
+					bt_destroy_t destroy,
+					gboolean filter_svc_class)
+{
+	int err = create_search_context(ctxt, src, dst, uuid, flags);
+
+	if (err < 0)
+		return err;
+
+	(*ctxt)->cb = cb;
+	(*ctxt)->destroy = destroy;
+	(*ctxt)->user_data = user_data;
+	(*ctxt)->filter_svc_class = filter_svc_class;
+
+	return 0;
+}
+
+int bt_search(const bdaddr_t *src, const bdaddr_t *dst,
 			uuid_t *uuid, bt_callback_t cb, void *user_data,
 			bt_destroy_t destroy, uint16_t flags)
 {
@@ -348,13 +380,32 @@ int bt_search_service(const bdaddr_t *src, const bdaddr_t *dst,
 	if (!cb)
 		return -EINVAL;
 
-	err = create_search_context(&ctxt, src, dst, uuid, flags);
+	/* The resulting service class ID doesn't have to match uuid */
+	err = create_search_context_full(&ctxt, src, dst, uuid, flags,
+					user_data, cb, destroy, FALSE);
 	if (err < 0)
 		return err;
 
-	ctxt->cb	= cb;
-	ctxt->destroy	= destroy;
-	ctxt->user_data	= user_data;
+	context_list = g_slist_append(context_list, ctxt);
+
+	return 0;
+}
+
+int bt_search_service(const bdaddr_t *src, const bdaddr_t *dst,
+			uuid_t *uuid, bt_callback_t cb, void *user_data,
+			bt_destroy_t destroy, uint16_t flags)
+{
+	struct search_context *ctxt = NULL;
+	int err;
+
+	if (!cb)
+		return -EINVAL;
+
+	/* The resulting service class ID need to match uuid */
+	err = create_search_context_full(&ctxt, src, dst, uuid, flags,
+					user_data, cb, destroy, TRUE);
+	if (err < 0)
+		return err;
 
 	context_list = g_slist_append(context_list, ctxt);
 
diff --git a/src/sdp-client.h b/src/sdp-client.h
index 9aa5a4d98..3a7212fd2 100644
--- a/src/sdp-client.h
+++ b/src/sdp-client.h
@@ -24,6 +24,9 @@
 typedef void (*bt_callback_t) (sdp_list_t *recs, int err, gpointer user_data);
 typedef void (*bt_destroy_t) (gpointer user_data);
 
+int bt_search(const bdaddr_t *src, const bdaddr_t *dst,
+			uuid_t *uuid, bt_callback_t cb, void *user_data,
+			bt_destroy_t destroy, uint16_t flags);
 int bt_search_service(const bdaddr_t *src, const bdaddr_t *dst,
 			uuid_t *uuid, bt_callback_t cb, void *user_data,
 			bt_destroy_t destroy, uint16_t flags);
-- 
2.25.0.265.gbab2e86ba0-goog