[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: 6.5 5.15
Change-Id: I8dcfe031f70ad61fa3d87dc9d771c3fabc6d0edc
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>
(cherry picked from commit aecbd657c841a2a8c74631ceac96b8ff1f03ab5c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 53e991671f725c136e9aa824c59ec13934c63fb4)

Gbp-Pq: Name CVE-2025-23050.diff

diff --git a/src/bluetooth/qlowenergycontroller_bluez.cpp b/src/bluetooth/qlowenergycontroller_bluez.cpp
index 6f0c98581307ef346c393af7a82d04b13bd295b0..2bd0cb68b5cc54594f98c1cd7897e5b31f820fc6 100644 (file)
--- a/src/bluetooth/qlowenergycontroller_bluez.cpp
+++ b/src/bluetooth/qlowenergycontroller_bluez.cpp
@@ -64,14 +64,15 @@ using namespace QBluetooth;
 
 const int maxPrepareQueueSize = 1024;
 
-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<QBluezConst::AttCommand>(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<QBluezConst::AttCommand>(data[1]);
@@ -126,6 +127,8 @@ static void dumpErrorInformation(const QByteArray &response)
 
     qCDebug(QT_BT_BLUEZ) << "Error:" << errorCode << "Error description:" << errorString
                          << "last command:" << lastCommand << "handle:" << handle;
+
+    return true;
 }
 
 static int getUuidSize(const QBluetoothUuid &uuid)
@@ -903,6 +906,7 @@ QLowEnergyHandle parseReadByTypeCharDiscovery(
 {
     Q_ASSERT(charData);
     Q_ASSERT(data);
+    Q_ASSERT(elementLength >= 5);
 
     QLowEnergyHandle attributeHandle = bt_get_le16(&data[0]);
     charData->properties =
@@ -912,7 +916,7 @@ QLowEnergyHandle parseReadByTypeCharDiscovery(
     // Bluetooth LE data comes as little endian
     if (elementLength == 7) // 16 bit uuid
         charData->uuid = QBluetoothUuid(bt_get_le16(&data[5]));
-    else
+    else if (elementLength == 21) // 128 bit uuid
         charData->uuid = QUuid::fromBytes(&data[5], QSysInfo::LittleEndian);
 
     qCDebug(QT_BT_BLUEZ) << "Found handle:" << Qt::hex << attributeHandle
@@ -929,6 +933,7 @@ QLowEnergyHandle parseReadByTypeIncludeDiscovery(
 {
     Q_ASSERT(foundServices);
     Q_ASSERT(data);
+    Q_ASSERT(elementLength >= 6);
 
     QLowEnergyHandle attributeHandle = bt_get_le16(&data[0]);
 
@@ -938,9 +943,14 @@ QLowEnergyHandle parseReadByTypeIncludeDiscovery(
     // 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(QUuid::fromBytes(&data[6], QSysInfo::LittleEndian));
 
     qCDebug(QT_BT_BLUEZ) << "Found included service: " << Qt::hex
@@ -949,17 +959,29 @@ QLowEnergyHandle parseReadByTypeIncludeDiscovery(
     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<QBluezConst::AttCommand>(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<QBluezConst::AttCommand>(response.constData()[1]);
         isErrorResponse = true;
     }
@@ -972,6 +994,10 @@ void QLowEnergyControllerPrivateBluez::processReply(
         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;
@@ -1000,8 +1026,15 @@ void QLowEnergyControllerPrivateBluez::processReply(
             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();
@@ -1077,16 +1110,25 @@ void QLowEnergyControllerPrivateBluez::processReply(
         }
 
         /* packet format:
-         * if GATT_CHARACTERISTIC discovery
+         * if GATT_CHARACTERISTIC discovery (Spec 5.3, Vol. 3, Part G, 4.6)
          *      <opcode><elementLength>
          *          [<handle><property><charHandle><uuid>]+
+         * 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)
          *      <opcode><elementLength>
          *          [<handle><startHandle_included><endHandle_included><uuid>]+
+         *  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;
@@ -1283,6 +1325,12 @@ void QLowEnergyControllerPrivateBluez::processReply(
             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) {
@@ -1720,9 +1768,18 @@ void QLowEnergyControllerPrivateBluez::discoverServiceDescriptors(
 
 void QLowEnergyControllerPrivateBluez::processUnsolicitedReply(const QByteArray &payload)
 {
+    Q_ASSERT(!payload.isEmpty());
+
     const char *data = payload.constData();
-    bool isNotification = (static_cast<QBluezConst::AttCommand>(data[0])
+    const auto command = static_cast<QBluezConst::AttCommand>(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()) {