Remove bytes after first zero length field in legacy advertisements (a57e748b) · Commits · e / os / android_packages_modules_Bluetooth

system/stack/btm/btm_ble_gap.cc

+2 −1

Original line number	Diff line number	Diff line
		@@ -2013,7 +2013,8 @@ static void btm_ble_process_adv_pkt_cont(
		bool is_start =
		ble_evt_type_is_legacy(evt_type) && is_scannable && !is_scan_resp;

		if (is_start) AdvertiseDataParser::RemoveTrailingZeros(tmp);
		if (ble_evt_type_is_legacy(evt_type))
		AdvertiseDataParser::RemoveTrailingZeros(tmp);

		// We might have send scan request to this device before, but didn't get the
		// response. In such case make sure data is put at start, not appended to

system/stack/include/advertise_data_parser.h

+1 −6

Original line number	Diff line number	Diff line
		@@ -57,12 +57,7 @@ class AdvertiseDataParser {
		// end of the packet. Otherwise i.e. gluing scan response to advertise
		// data will result in data with zero padding in the middle.
		if (len == 0) {
		size_t zeros_start = position;
		for (size_t i = position + 1; i < ad_len; i++) {
		if (ad[i] != 0) return;
		}

		ad.erase(ad.begin() + zeros_start, ad.end());
		ad.erase(ad.begin() + position, ad.end());
		return;
		}

system/stack/test/ad_parser_unittest.cc

+28 −2

Original line number	Diff line number	Diff line
		@@ -137,15 +137,41 @@ TEST(AdvertiseDataParserTest, RemoveTrailingZeros) {
		0x02, 0x01, 0x02, 0x11, 0x06, 0x66, 0x9a, 0x0c, 0x20, 0x00, 0x08,
		0x37, 0xa8, 0xe5, 0x11, 0x81, 0x8b, 0xd0, 0xf0, 0xf0, 0xf0, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
		const std::vector<uint8_t> podo_scan_resp{
		std::vector<uint8_t> podo_scan_resp{
		0x03, 0x19, 0x00, 0x80, 0x09, 0x09, 0x50, 0x6f, 0x64, 0x6f, 0x51,
		0x35, 0x56, 0x47, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

		AdvertiseDataParser::RemoveTrailingZeros(podo_ad_data);
		AdvertiseDataParser::RemoveTrailingZeros(podo_scan_resp);

		std::vector<uint8_t> glued(podo_ad_data);
		glued.insert(glued.end(), podo_ad_data.begin(), podo_ad_data.end());
		glued.insert(glued.end(), podo_scan_resp.begin(), podo_scan_resp.end());

		EXPECT_TRUE(AdvertiseDataParser::IsValid(glued));
		}

		// This test makes sure that RemoveTrailingZeros is removing all bytes after
		// first zero length field. It does run the RemoveTrailingZeros for data with
		// non-zero bytes after zero length field, then glue scan response at end of it,
		// and checks that the resulting data is good. Note: specification requires all
		// bytes after zero length field to be zero padding, but many legacy devices got
		// this wrong, causing us to have this workaround.
		TEST(AdvertiseDataParserTest, RemoveTrailingZerosMalformed) {
		std::vector<uint8_t> ad_data{0x02, 0x01, 0x02, 0x11, 0x06, 0x66, 0x9a, 0x0c,
		0x20, 0x00, 0x08, 0x37, 0xa8, 0xe5, 0x11, 0x81,
		0x8b, 0xd0, 0xf0, 0xf0, 0xf0, 0x00, 0xFF, 0xFF,
		0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
		std::vector<uint8_t> scan_resp{0x03, 0x19, 0x00, 0x80, 0x09, 0x09, 0x50, 0x6f,
		0x64, 0x6f, 0x51, 0x35, 0x56, 0x47, 0x00, 0xFF,
		0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
		0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

		AdvertiseDataParser::RemoveTrailingZeros(ad_data);
		AdvertiseDataParser::RemoveTrailingZeros(scan_resp);

		std::vector<uint8_t> glued(ad_data);
		glued.insert(glued.end(), scan_resp.begin(), scan_resp.end());

		EXPECT_TRUE(AdvertiseDataParser::IsValid(glued));
		}
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