Merge pull request #1009 from leethomason/leethomason/charref

Fix the potential overflow in char refs

tinyxml2.cpp

@@ -467,102 +467,89 @@ void XMLUtil::ConvertUTF32ToUTF8( unsigned long input, char* output, int* length
 }
 
 
-const char* XMLUtil::GetCharacterRef( const char* p, char* value, int* length )
+const char* XMLUtil::GetCharacterRef(const char* p, char* value, int* length)
 {
-    // Presume an entity, and pull it out.
+    // Assume an entity, and pull it out.
     *length = 0;
 
-    if ( *(p+1) == '#' && *(p+2) ) {
-        unsigned long ucs = 0;
-        TIXMLASSERT( sizeof( ucs ) >= 4 );
+    static const uint32_t MAX_CODE_POINT = 0x10FFFF;
+
+    if (*(p + 1) == '#' && *(p + 2)) {
+        uint32_t ucs = 0;
         ptrdiff_t delta = 0;
-        unsigned mult = 1;
+        uint32_t mult = 1;
         static const char SEMICOLON = ';';
 
-        if ( *(p+2) == 'x' ) {
+        bool hex = false;
+        uint32_t radix = 10;
+        const char* q = 0;
+        char terminator = '#';
+
+        if (*(p + 2) == 'x') {
             // Hexadecimal.
-            const char* q = p+3;
-            if ( !(*q) ) {
-                return 0;
-            }
+            hex = true;
+            radix = 16;
+            terminator = 'x';
 
-            q = strchr( q, SEMICOLON );
+            q = p + 3;
+        }
+        else {
+            // Decimal.
+            q = p + 2;
+        }
+        if (!(*q)) {
+            return 0;
+        }
 
-            if ( !q ) {
-                return 0;
-            }
-            TIXMLASSERT( *q == SEMICOLON );
+        q = strchr(q, SEMICOLON);
+        if (!q) {
+            return 0;
+        }
+        TIXMLASSERT(*q == SEMICOLON);
 
-            delta = q-p;
-            --q;
+        delta = q - p;
+        --q;
 
-            while ( *q != 'x' ) {
-                unsigned int digit = 0;
+        while (*q != terminator) {
+            uint32_t digit = 0;
 
-                if ( *q >= '0' && *q <= '9' ) {
-                    digit = *q - '0';
-                }
-                else if ( *q >= 'a' && *q <= 'f' ) {
-                    digit = *q - 'a' + 10;
-                }
-                else if ( *q >= 'A' && *q <= 'F' ) {
-                    digit = *q - 'A' + 10;
-                }
-                else {
-                    return 0;
-                }
-                TIXMLASSERT( digit < 16 );
-                TIXMLASSERT( digit == 0 || mult <= UINT_MAX / digit );
-                const unsigned int digitScaled = mult * digit;
-                TIXMLASSERT( ucs <= ULONG_MAX - digitScaled );
-                ucs += digitScaled;
-                TIXMLASSERT( mult <= UINT_MAX / 16 );
-                mult *= 16;
-                --q;
+            if (*q >= '0' && *q <= '9') {
+                digit = *q - '0';
             }
-        }
-        else {
-            // Decimal.
-            const char* q = p+2;
-            if ( !(*q) ) {
-                return 0;
+            else if (hex && (*q >= 'a' && *q <= 'f')) {
+                digit = *q - 'a' + 10;
             }
-
-            q = strchr( q, SEMICOLON );
-
-            if ( !q ) {
+            else if (hex && (*q >= 'A' && *q <= 'F')) {
+                digit = *q - 'A' + 10;
+            }
+            else {
                 return 0;
             }
-            TIXMLASSERT( *q == SEMICOLON );
-
-            delta = q-p;
-            --q;
-
-            while ( *q != '#' ) {
-                if ( *q >= '0' && *q <= '9' ) {
-                    const unsigned int digit = *q - '0';
-                    TIXMLASSERT( digit < 10 );
-                    TIXMLASSERT( digit == 0 || mult <= UINT_MAX / digit );
-                    const unsigned int digitScaled = mult * digit;
-                    TIXMLASSERT( ucs <= ULONG_MAX - digitScaled );
-                    ucs += digitScaled;
-                }
-                else {
-                    return 0;
-                }
-                TIXMLASSERT( mult <= UINT_MAX / 10 );
-                mult *= 10;
-                --q;
+            TIXMLASSERT(digit < radix);
+
+            const unsigned int digitScaled = mult * digit;
+            ucs += digitScaled;
+            mult *= radix;       
+            
+            // Security check: could a value exist that is out of range?
+            // Easily; limit to the MAX_CODE_POINT, which also allows for a
+            // bunch of leading zeroes.
+            if (mult > MAX_CODE_POINT) {
+                mult = MAX_CODE_POINT;
             }
+            --q;
+        }
+        // Out of range:
+        if (ucs > MAX_CODE_POINT) {
+            return 0;
         }
         // convert the UCS to UTF-8
-        ConvertUTF32ToUTF8( ucs, value, length );
+        ConvertUTF32ToUTF8(ucs, value, length);
         return p + delta + 1;
     }
-    return p+1;
+    return p + 1;
 }
 
-
 void XMLUtil::ToStr( int v, char* buffer, int bufferSize )
 {
     TIXML_SNPRINTF( buffer, bufferSize, "%d", v );

xmltest.cpp

@@ -1642,7 +1642,7 @@ int main( int argc, const char ** argv )
 
 		static const char* result  = "\xef\xbb\xbf<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
 		XMLTest( "BOM and default declaration", result, printer.CStr(), false );
-		XMLTest( "CStrSize", 42, printer.CStrSize(), false );
+		XMLTest( "CStrSize", true, printer.CStrSize() == 42, false );
 	}
 	{
 		const char* xml = "<ipxml ws='1'><info bla=' /></ipxml>";
@@ -2666,6 +2666,35 @@ int main( int argc, const char ** argv )
     	doc.PrintError();
     }
 
+	// ---------- CVE-2024-50615 -----------
+	{
+		const char* xml = "<Hello value='12&#65;34' value2='56&#x42;78'>Text</Hello>";
+		XMLDocument doc;
+		doc.Parse(xml);
+		const char* value = doc.FirstChildElement()->Attribute("value");
+		const char* value2 = doc.FirstChildElement()->Attribute("value2");
+		XMLTest("Test attribute encode", false, doc.Error());
+		XMLTest("Test decimal value", value, "12A34");
+		XMLTest("Test hex encode", value2, "56B78");
+	}
+
+	{
+		const char* xml = "<Hello value='&#ABC9000000065;' value2='&#xffffffff;' value3='&#5000000000;' value4='&#x00000045;' value5='&#x000000000000000021;'>Text</Hello>";
+		XMLDocument doc;
+		doc.Parse(xml);
+		const char* value = doc.FirstChildElement()->Attribute("value");
+		const char* value2 = doc.FirstChildElement()->Attribute("value2");
+		const char* value3 = doc.FirstChildElement()->Attribute("value3");
+		const char* value4 = doc.FirstChildElement()->Attribute("value4");
+		const char* value5 = doc.FirstChildElement()->Attribute("value5");
+		XMLTest("Test attribute encode", false, doc.Error());
+		XMLTest("Test attribute encode too long value", value, "&#ABC9000000065;"); // test long value
+		XMLTest("Test attribute encode out of unicode range", value2, "&#xffffffff;"); // out of unicode range
+		XMLTest("Test attribute encode out of int max value", value3, "&#5000000000;"); // out of int max value
+		XMLTest("Test attribute encode with a Hex value", value4, "E"); // hex value in unicode value
+		XMLTest("Test attribute encode with a Hex value", value5, "!"); // hex value in unicode value
+	}
+
     // ----------- Performance tracking --------------
 	{
 #if defined( _MSC_VER )