Resources: reject compressed content we can't decompress

This solution is composed of two features:

1) C++ code generated by RCC uses two symbols exported from QtCore that
are only present if the feature was compiled in. If the feature was not
compiled in, this will cause a linker error either at build time or at
load time (if they were functions, the error could be at runtime).

2) Binary files generated by RCC have a new header field containing
flags. We're currently using two flags, one for Zlib and one for
Zstandard.

This means we now have binary RCC format version 3.

Change-Id: I42a48bd64ccc41aebf84fffd156545fb6a4f72d9
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

4 files changed, 115 insertions, 15 deletions

diff --git a/src/corelib/io/qresource.cpp b/src/corelib/io/qresource.cpp
index 52a20191a9..804029725a 100644
--- a/src/corelib/io/qresource.cpp
+++ b/src/corelib/io/qresource.cpp
@@ -77,6 +77,26 @@
 
 QT_BEGIN_NAMESPACE
 
+// Symbols used by code generated by RCC.
+// They cause compilation errors if the RCC content couldn't
+// be interpreted by this QtCore version.
+#if defined(__ELF__) || defined(__APPLE__)  // same as RCC generates
+#  define RCC_FEATURE_SYMBOL(feature)   \
+    extern Q_CORE_EXPORT const quint8 qt_resourceFeature ## feature; \
+    const quint8 qt_resourceFeature ## feature = 0;
+#else
+#  define RCC_FEATURE_SYMBOL(feature)   \
+    Q_CORE_EXPORT quint8 qResourceFeature ## feature() { return 0; }
+#endif
+
+#ifndef QT_NO_COMPRESS
+RCC_FEATURE_SYMBOL(Zlib)
+#endif
+#if QT_CONFIG(zstd)
+RCC_FEATURE_SYMBOL(Zstd)
+#endif
+
+#undef RCC_FEATURE_SYMBOL
 
 class QStringSplitter
 {
@@ -109,6 +129,7 @@ public:
 //resource glue
 class QResourceRoot
 {
+public:
     enum Flags
     {
         // must match rcc.h
@@ -116,6 +137,7 @@ class QResourceRoot
         Directory = 0x02,
         CompressedZstd = 0x04
     };
+private:
     const uchar *tree, *names, *payloads;
     int version;
     inline int findOffset(int node) const { return node * (14 + (version >= 0x02 ? 8 : 0)); } //sizeof each tree element
@@ -917,7 +939,7 @@ Q_CORE_EXPORT bool qRegisterResourceData(int version, const unsigned char *tree,
                                          const unsigned char *name, const unsigned char *data)
 {
     QMutexLocker lock(resourceMutex());
-    if ((version == 0x01 || version == 0x2) && resourceList()) {
+    if (version >= 0x01 && version <= 0x3 && resourceList()) {
         bool found = false;
         QResourceRoot res(version, tree, name, data);
         for(int i = 0; i < resourceList()->size(); ++i) {
@@ -943,7 +965,7 @@ Q_CORE_EXPORT bool qUnregisterResourceData(int version, const unsigned char *tre
         return false;
 
     QMutexLocker lock(resourceMutex());
-    if ((version == 0x01 || version == 0x02) && resourceList()) {
+    if (version >= 0x01 && version <= 0x3 && resourceList()) {
         QResourceRoot res(version, tree, name, data);
         for(int i = 0; i < resourceList()->size(); ) {
             if(*resourceList()->at(i) == res) {
@@ -1002,11 +1024,27 @@ public:
         const int name_offset = qFromBigEndian<qint32>(b + offset);
         offset += 4;
 
+        quint32 file_flags = 0;
+        if (version >= 3) {
+            file_flags = qFromBigEndian<qint32>(b + offset);
+            offset += 4;
+        }
+
         // Some sanity checking for sizes. This is _not_ a security measure.
         if (size >= 0 && (tree_offset >= size || data_offset >= size || name_offset >= size))
             return false;
 
-        if (version == 0x01 || version == 0x02) {
+        // And some sanity checking for features
+        quint32 acceptableFlags = 0;
+#ifndef QT_NO_COMPRESS
+        acceptableFlags |= Compressed;
+#endif
+        if (QT_CONFIG(zstd))
+            acceptableFlags |= CompressedZstd;
+        if (file_flags & ~acceptableFlags)
+            return false;
+
+        if (version >= 0x01 && version <= 0x03) {
             buffer = b;
             setSource(version, b+tree_offset, b+name_offset, b+data_offset);
             return true;
diff --git a/src/tools/rcc/main.cpp b/src/tools/rcc/main.cpp
index 71836b81bd..6e8c13be15 100644
--- a/src/tools/rcc/main.cpp
+++ b/src/tools/rcc/main.cpp
@@ -185,13 +185,13 @@ int runRcc(int argc, char *argv[])
 
     QString errorMsg;
 
-    quint8 formatVersion = 2;
+    quint8 formatVersion = 3;
     if (parser.isSet(formatVersionOption)) {
         bool ok = false;
         formatVersion = parser.value(formatVersionOption).toUInt(&ok);
         if (!ok) {
             errorMsg = QLatin1String("Invalid format version specified");
-        } else if (formatVersion != 1 && formatVersion != 2) {
+        } else if (formatVersion < 1 || formatVersion > 3) {
             errorMsg = QLatin1String("Unsupported format version specified");
         }
     }
@@ -208,6 +208,8 @@ int runRcc(int argc, char *argv[])
 
     if (parser.isSet(compressionAlgoOption))
         library.setCompressionAlgorithm(RCCResourceLibrary::parseCompressionAlgorithm(parser.value(compressionAlgoOption), &errorMsg));
+    if (formatVersion < 3 && library.compressionAlgorithm() == RCCResourceLibrary::CompressionAlgorithm::Zstd)
+        errorMsg = QLatin1String("Zstandard compression requires format version 3 or higher");
     if (parser.isSet(nocompressOption))
         library.setCompressionAlgorithm(RCCResourceLibrary::CompressionAlgorithm::None);
     if (parser.isSet(compressOption) && errorMsg.isEmpty()) {
diff --git a/src/tools/rcc/rcc.cpp b/src/tools/rcc/rcc.cpp
index 5cbc771994..f284749781 100644
--- a/src/tools/rcc/rcc.cpp
+++ b/src/tools/rcc/rcc.cpp
@@ -295,6 +295,7 @@ qint64 RCCFileInfo::writeDataBlob(RCCResourceLibrary &lib, qint64 offset,
                     lib.m_errorDevice->write(msg.toUtf8());
                 }
 
+                lib.m_overallFlags |= CompressedZstd;
                 m_flags |= CompressedZstd;
                 data = std::move(compressed);
                 data.truncate(n);
@@ -321,6 +322,7 @@ qint64 RCCFileInfo::writeDataBlob(RCCResourceLibrary &lib, qint64 offset,
                     lib.m_errorDevice->write(msg.toUtf8());
                 }
                 data = compressed;
+                lib.m_overallFlags |= Compressed;
                 m_flags |= Compressed;
             } else if (lib.verbose()) {
                 QString msg = QString::fromLatin1("%1: note: not compressed\n").arg(m_name);
@@ -438,6 +440,7 @@ RCCResourceLibrary::RCCResourceLibrary(quint8 formatVersion)
     m_treeOffset(0),
     m_namesOffset(0),
     m_dataOffset(0),
+    m_overallFlags(0),
     m_useNameSpace(CONSTANT_USENAMESPACE),
     m_errorDevice(0),
     m_outDevice(0),
@@ -945,6 +948,14 @@ bool RCCResourceLibrary::output(QIODevice &outDevice, QIODevice &tempDevice, QIO
     return true;
 }
 
+void RCCResourceLibrary::writeDecimal(int value)
+{
+    Q_ASSERT(m_format != RCCResourceLibrary::Binary);
+    char buf[std::numeric_limits<int>::digits10 + 2];
+    int n = snprintf(buf, sizeof(buf), "%d", value);
+    write(buf, n + 1);  // write() takes a size including terminating NUL
+}
+
 void RCCResourceLibrary::writeHex(quint8 tmp)
 {
     const char digits[] = "0123456789abcdef";
@@ -1039,6 +1050,8 @@ bool RCCResourceLibrary::writeHeader()
         writeNumber4(0);
         writeNumber4(0);
         writeNumber4(0);
+        if (m_formatVersion >= 3)
+            writeNumber4(m_overallFlags);
     }
     return true;
 }
@@ -1241,10 +1254,35 @@ bool RCCResourceLibrary::writeInitializer()
         if (m_root) {
             writeString("bool qRegisterResourceData"
                 "(int, const unsigned char *, "
-                "const unsigned char *, const unsigned char *);\n\n");
+                "const unsigned char *, const unsigned char *);\n");
             writeString("bool qUnregisterResourceData"
                 "(int, const unsigned char *, "
                 "const unsigned char *, const unsigned char *);\n\n");
+
+            if (m_overallFlags & (RCCFileInfo::Compressed | RCCFileInfo::CompressedZstd)) {
+                // use variable relocations with ELF and Mach-O
+                writeString("#if defined(__ELF__) || defined(__APPLE__)\n");
+                if (m_overallFlags & RCCFileInfo::Compressed) {
+                    writeString("static inline unsigned char qResourceFeatureZlib()\n"
+                                "{\n"
+                                "    extern const unsigned char qt_resourceFeatureZlib;\n"
+                                "    return qt_resourceFeatureZlib;\n"
+                                "}\n");
+                }
+                if (m_overallFlags & RCCFileInfo::CompressedZstd) {
+                    writeString("static inline unsigned char qResourceFeatureZstd()\n"
+                                "{\n"
+                                "    extern const unsigned char qt_resourceFeatureZstd;\n"
+                                "    return qt_resourceFeatureZstd;\n"
+                                "}\n");
+                }
+                writeString("#else\n");
+                if (m_overallFlags & RCCFileInfo::Compressed)
+                    writeString("unsigned char qResourceFeatureZlib();\n");
+                if (m_overallFlags & RCCFileInfo::CompressedZstd)
+                    writeString("unsigned char qResourceFeatureZstd();\n");
+                writeString("#endif\n\n");
+            }
         }
 
         if (m_useNameSpace)
@@ -1263,12 +1301,12 @@ bool RCCResourceLibrary::writeInitializer()
         writeString("()\n{\n");
 
         if (m_root) {
-            writeString("    ");
+            writeString("    int version = ");
+            writeDecimal(m_formatVersion);
+            writeString(";\n    ");
             writeAddNamespaceFunction("qRegisterResourceData");
-            writeString("\n        (");
-            writeHex(m_formatVersion);
-            writeString(" qt_resource_struct, "
-                       "qt_resource_name, qt_resource_data);\n");
+            writeString("\n        (version, qt_resource_struct, "
+                        "qt_resource_name, qt_resource_data);\n");
         }
         writeString("    return 1;\n");
         writeString("}\n\n");
@@ -1286,11 +1324,24 @@ bool RCCResourceLibrary::writeInitializer()
         writeMangleNamespaceFunction(cleanResources);
         writeString("()\n{\n");
         if (m_root) {
-            writeString("    ");
+            writeString("    int version = ");
+            writeDecimal(m_formatVersion);
+            writeString(";\n    ");
+
+            // ODR-use certain symbols from QtCore if we require optional features
+            if (m_overallFlags & RCCFileInfo::Compressed) {
+                writeString("version += ");
+                writeAddNamespaceFunction("qResourceFeatureZlib()");
+                writeString(";\n    ");
+            }
+            if (m_overallFlags & RCCFileInfo::CompressedZstd) {
+                writeString("version += ");
+                writeAddNamespaceFunction("qResourceFeatureZstd()");
+                writeString(";\n    ");
+            }
+
             writeAddNamespaceFunction("qUnregisterResourceData");
-            writeString("\n       (");
-            writeHex(m_formatVersion);
-            writeString(" qt_resource_struct, "
+            writeString("\n       (version, qt_resource_struct, "
                       "qt_resource_name, qt_resource_data);\n");
         }
         writeString("    return 1;\n");
@@ -1326,6 +1377,13 @@ bool RCCResourceLibrary::writeInitializer()
         p[i++] = (m_namesOffset >> 16) & 0xff;
         p[i++] = (m_namesOffset >>  8) & 0xff;
         p[i++] = (m_namesOffset >>  0) & 0xff;
+
+        if (m_formatVersion >= 3) {
+            p[i++] = (m_overallFlags >> 24) & 0xff;
+            p[i++] = (m_overallFlags >> 16) & 0xff;
+            p[i++] = (m_overallFlags >>  8) & 0xff;
+            p[i++] = (m_overallFlags >>  0) & 0xff;
+        }
     }
     return true;
 }
diff --git a/src/tools/rcc/rcc.h b/src/tools/rcc/rcc.h
index 7603a41cde..ad1c5cd166 100644
--- a/src/tools/rcc/rcc.h
+++ b/src/tools/rcc/rcc.h
@@ -134,6 +134,7 @@ private:
     bool writeInitializer();
     void writeMangleNamespaceFunction(const QByteArray &name);
     void writeAddNamespaceFunction(const QByteArray &name);
+    void writeDecimal(int value);
     void writeHex(quint8 number);
     void writeNumber2(quint16 number);
     void writeNumber4(quint32 number);
@@ -160,6 +161,7 @@ private:
     int m_treeOffset;
     int m_namesOffset;
     int m_dataOffset;
+    quint32 m_overallFlags;
     bool m_useNameSpace;
     QStringList m_failedResources;
     QIODevice *m_errorDevice;