Add a way to limit deserialized string lengths

and use it for most strings being serialized.

src/serialize.h

@@ -334,8 +334,9 @@ I ReadVarInt(Stream& is)
     }
 }
 
-#define FLATDATA(obj)  REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))
-#define VARINT(obj)    REF(WrapVarInt(REF(obj)))
+#define FLATDATA(obj) REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))
+#define VARINT(obj) REF(WrapVarInt(REF(obj)))
+#define LIMITED_STRING(obj,n) REF(LimitedString< n >(REF(obj)))
 
 /** Wrapper for serializing arrays and POD.
  */
@@ -398,6 +399,40 @@ public:
     }
 };
 
+template<size_t Limit>
+class LimitedString
+{
+protected:
+    std::string& string;
+public:
+    LimitedString(std::string& string) : string(string) {}
+
+    template<typename Stream>
+    void Unserialize(Stream& s, int, int=0)
+    {
+        size_t size = ReadCompactSize(s);
+        if (size > Limit) {
+            throw std::ios_base::failure("String length limit exceeded");
+        }
+        string.resize(size);
+        if (size != 0)
+            s.read((char*)&string[0], size);
+    }
+
+    template<typename Stream>
+    void Serialize(Stream& s, int, int=0) const
+    {
+        WriteCompactSize(s, string.size());
+        if (!string.empty())
+            s.write((char*)&string[0], string.size());
+    }
+
+    unsigned int GetSerializeSize(int, int=0) const
+    {
+        return GetSizeOfCompactSize(string.size()) + string.size();
+    }
+};
+
 template<typename I>
 CVarInt<I> WrapVarInt(I& n) { return CVarInt<I>(n); }