Limit maximum length of ByteArrayWriter.

aria2 downloads meta files such as .torrent and .metalink file in
memory using ByteArrayWriter. To prevent accidentally download big
file, we set the maximum length that ByteArrayWriter can hold.  The
default is 5MiB and it is reasonable because most .torrent and
.metalink file are much smaller than that.

src/ByteArrayDiskWriter.cc

@@ -34,10 +34,14 @@
 /* copyright --> */
 #include "ByteArrayDiskWriter.h"
 #include "A2STR.h"
+#include "DlAbortEx.h"
+#include "fmt.h"
 
 namespace aria2 {
 
-ByteArrayDiskWriter::ByteArrayDiskWriter() {}
+ByteArrayDiskWriter::ByteArrayDiskWriter(size_t maxLength)
+  : maxLength_(maxLength)
+{}
 
 ByteArrayDiskWriter::~ByteArrayDiskWriter() {}
 
@@ -62,6 +66,10 @@ void ByteArrayDiskWriter::openExistingFile(uint64_t totalLength)
 
 void ByteArrayDiskWriter::writeData(const unsigned char* data, size_t dataLength, off_t position)
 {
+  if(position+dataLength > maxLength_) {
+    throw DL_ABORT_EX(fmt("Maximum length(%lu) exceeded.",
+                          static_cast<unsigned long>(maxLength_)));
+  }
   uint64_t length = size();
   if(length < (uint64_t)position) {
     buf_.seekp(length, std::ios::beg);

src/ByteArrayDiskWriter.h

@@ -43,10 +43,10 @@ namespace aria2 {
 class ByteArrayDiskWriter : public DiskWriter {
 private:
   std::stringstream buf_;
-
+  size_t maxLength_;
   void clear();
 public:
-  ByteArrayDiskWriter();
+  ByteArrayDiskWriter(size_t maxLength = 5*1024*1024);
   virtual ~ByteArrayDiskWriter();
 
   virtual void initAndOpenFile(uint64_t totalLength = 0);