BUG: Buffer not null terminated

Coverity reports:
buffer_size_warning: Calling strncpy with a maximum size argument of
32 bytes on destination array "header.filename" of size 32 bytes might
leave the destination string unterminated.

If the buffer is treated as a null terminated string in later
operations, a buffer overflow or over-read may occur.  In
itk::​BioRadImageIO::​Write(void const*): The string buffer may not
have a null terminator if the source string's length is equal to the
buffer size.

Change-Id: I3b2a5fa83b0354580a99a48907a0518e785f2a6e

Modules/IO/BioRad/src/itkBioRadImageIO.cxx

@@ -500,8 +500,10 @@ void BioRadImageIO::Write(const void *buffer)
   // or simply
   // 4. FileName
   std::string filename = itksys::SystemTools::GetFilenameName(m_FileName);
-  // The buffer is at most 32 bytes:
-  strncpy( header.filename, filename.c_str(), sizeof( header.filename ) );
+  // The buffer is at most 32 bytes, but must be null-terminated.
+  // Here we copy at most 31 bytes and terminate it explicitly
+  strncpy( header.filename, filename.c_str(), sizeof( header.filename ) - 1);
+  header.filename[sizeof( header.filename ) - 1] = '\0';
   file.write( (char *)p, BIORAD_HEADER_LENGTH );
 
   //preparation for writing buffer: