From 88c30a23dcff5e7c16a54f93accf743847e22617 Mon Sep 17 00:00:00 2001 From: Ivan Solovev Date: Thu, 02 Jan 2025 16:48:49 +0100 Subject: [PATCH] QLowEnergyControllerPrivateBluez: guard against malformed replies The QLowEnergyControllerPrivateBluez::l2cpReadyRead() slot reads the data from a Bluetooth L2CAP socket and then tries to process it according to ATT protocol specs. However, the code was missing length and sanity checks at some codepaths in processUnsolicitedReply() and processReply() helper methods, simply relying on the data to be in the proper format. This patch adds some minimal checks to make sure that we do not read past the end of the received array and do not divide by zero. This problem was originally pointed out by Marc Mutz in an unrelated patch. Pick-to: 5.15 Change-Id: I8dcfe031f70ad61fa3d87dc9d771c3fabc6d0edc Reviewed-by: Alex Blasche Reviewed-by: Juha Vuolle (cherry picked from commit aecbd657c841a2a8c74631ceac96b8ff1f03ab5c) Reviewed-by: Qt Cherry-pick Bot (cherry picked from commit 53e991671f725c136e9aa824c59ec13934c63fb4) (cherry picked from commit 465e3f3112a9c158aa6dd2f8b9439ae6c2de336f) --- diff --git a/src/bluetooth/qlowenergycontroller_bluez.cpp b/src/bluetooth/qlowenergycontroller_bluez.cpp index 4a2248c..b4bad61 100644 --- a/src/bluetooth/qlowenergycontroller_bluez.cpp +++ b/src/bluetooth/qlowenergycontroller_bluez.cpp @@ -80,14 +80,15 @@ return QBluetoothUuid(qtdst); } -static void dumpErrorInformation(const QByteArray &response) +/* returns false if the format is incorrect */ +static bool dumpErrorInformation(const QByteArray &response) { const char *data = response.constData(); if (response.size() != 5 || (static_cast(data[0]) != QBluezConst::AttCommand::ATT_OP_ERROR_RESPONSE)) { qCWarning(QT_BT_BLUEZ) << QLatin1String("Not a valid error response"); - return; + return false; } QBluezConst::AttCommand lastCommand = static_cast(data[1]); @@ -142,6 +143,8 @@ qCDebug(QT_BT_BLUEZ) << "Error:" << errorCode << "Error description:" << errorString << "last command:" << lastCommand << "handle:" << handle; + + return true; } static int getUuidSize(const QBluetoothUuid &uuid) @@ -919,6 +922,7 @@ { Q_ASSERT(charData); Q_ASSERT(data); + Q_ASSERT(elementLength >= 5); QLowEnergyHandle attributeHandle = bt_get_le16(&data[0]); charData->properties = @@ -927,7 +931,7 @@ if (elementLength == 7) // 16 bit uuid charData->uuid = QBluetoothUuid(bt_get_le16(&data[5])); - else + else if (elementLength == 21) // 128 bit uuid charData->uuid = convert_uuid128((quint128 *)&data[5]); qCDebug(QT_BT_BLUEZ) << "Found handle:" << Qt::hex << attributeHandle @@ -944,6 +948,7 @@ { Q_ASSERT(foundServices); Q_ASSERT(data); + Q_ASSERT(elementLength >= 6); QLowEnergyHandle attributeHandle = bt_get_le16(&data[0]); @@ -953,9 +958,14 @@ // data[2] -> included service start handle // data[4] -> included service end handle + // TODO: Spec v. 5.3, Vol. 3, Part G, 4.5.1 mentions that only + // 16-bit UUID can be returned here. If the UUID is 128-bit, + // then it is omitted from the response, and should be requested + // separately with the ATT_READ_REQ command. + if (elementLength == 8) //16 bit uuid foundServices->append(QBluetoothUuid(bt_get_le16(&data[6]))); - else + else if (elementLength == 22) // 128 bit uuid foundServices->append(convert_uuid128((quint128 *) &data[6])); qCDebug(QT_BT_BLUEZ) << "Found included service: " << Qt::hex @@ -964,17 +974,29 @@ return attributeHandle; } +Q_DECL_COLD_FUNCTION +static void reportMalformedData(QBluezConst::AttCommand cmd, const QByteArray &response) +{ + qCDebug(QT_BT_BLUEZ, "%s malformed data: %s", qt_getEnumName(cmd), + response.toHex().constData()); +} + void QLowEnergyControllerPrivateBluez::processReply( const Request &request, const QByteArray &response) { Q_Q(QLowEnergyController); + // We already have an isEmpty() check at the only calling site that reads + // incoming data, so Q_ASSERT is enough. + Q_ASSERT(!response.isEmpty()); + QBluezConst::AttCommand command = static_cast(response.constData()[0]); bool isErrorResponse = false; // if error occurred 2. byte is previous request type if (command == QBluezConst::AttCommand::ATT_OP_ERROR_RESPONSE) { - dumpErrorInformation(response); + if (!dumpErrorInformation(response)) + return; command = static_cast(response.constData()[1]); isErrorResponse = true; } @@ -987,6 +1009,10 @@ if (isErrorResponse) { mtuSize = ATT_DEFAULT_LE_MTU; } else { + if (response.size() < 3) { + reportMalformedData(command, response); + break; + } const char *data = response.constData(); quint16 mtu = bt_get_le16(&data[1]); mtuSize = mtu; @@ -1015,8 +1041,15 @@ break; } + // response[1] == elementLength. According to the spec it should be + // at least 4 bytes. See Spec v5.3, Vol 3, Part F, 3.4.4.10 + if (response.size() < 2 || response[1] < 4) { + reportMalformedData(command, response); + break; + } + QLowEnergyHandle start = 0, end = 0; - const quint16 elementLength = response.constData()[1]; + const quint16 elementLength = response.constData()[1]; // value checked above const quint16 numElements = (response.size() - 2) / elementLength; quint16 offset = 2; const char *data = response.constData(); @@ -1092,16 +1125,25 @@ } /* packet format: - * if GATT_CHARACTERISTIC discovery + * if GATT_CHARACTERISTIC discovery (Spec 5.3, Vol. 3, Part G, 4.6) * * []+ + * The minimum elementLength is 7 bytes (uuid is always included) * - * if GATT_INCLUDE discovery + * if GATT_INCLUDE discovery (Spec 5.3, Vol. 3, Part G, 4.5.1) * * []+ + * The minimum elementLength is 6 bytes (uuid can be omitted). * * The uuid can be 16 or 128 bit. */ + + const quint8 minimumElementLength = attributeType == GATT_CHARACTERISTIC ? 7 : 6; + if (response.size() < 2 || response[1] < minimumElementLength) { + reportMalformedData(command, response); + break; + } + QLowEnergyHandle lastHandle; const quint16 elementLength = response.constData()[1]; const quint16 numElements = (response.size() - 2) / elementLength; @@ -1298,6 +1340,12 @@ break; } + // Spec 5.3, Vol. 3, Part F, 3.4.3.2 + if (response.size() < 6) { + reportMalformedData(command, response); + break; + } + const quint8 format = response[1]; quint16 elementLength; switch (format) { @@ -1735,9 +1783,18 @@ void QLowEnergyControllerPrivateBluez::processUnsolicitedReply(const QByteArray &payload) { + Q_ASSERT(!payload.isEmpty()); + const char *data = payload.constData(); - bool isNotification = (static_cast(data[0]) + const auto command = static_cast(data[0]); + bool isNotification = (command == QBluezConst::AttCommand::ATT_OP_HANDLE_VAL_NOTIFICATION); + + if (payload.size() < 3) { + reportMalformedData(command, payload); + return; + } + const QLowEnergyHandle changedHandle = bt_get_le16(&data[1]); if (QT_BT_BLUEZ().isDebugEnabled()) {