[help-cgicc] worrying potential DoS issue

[Russell Kliese]

I've been having a bit of a look over the code and one issue struck me. 
I was wondering if this has been considered:

In CgiEnvironment.cpp, the memory for the posted data is allocated as 
follows:

std::vector<char> data(getContentLength());

Would it be possible to make several requests with a false content 
length? Say:

Content-Length: 2000000000

I think this would soon lead to denial of service for legitimate users 
of the cgi script as memory would be exhausted (and swapping would 
probably slow the system down). I'm not sure if I've thought this 
through properly, so please correct me if I haven't.

A possible solution might be to accept the data into a file rather that 
allocating the entire amount indicated by the content length header. 
This would not add significant performance penalty as there won't be any 
disk IO if there is enough memory for the file to be buffered and if the 
file is deleted soon after it is created. In fact, the ability to swap 
the file buffers out of physical memory might improve performance. I'm 
not sure, however, if this could be done easily in a platform 
independent manner. Perhaps it could be a compile time option?

I've also run into another problem with session validation using 
cookies. Unfortunately, during a file upload, this session validation 
cannot be performed as the CgiEnvironment object can't be instantiated 
before the upload is complete. This is a problem because I'm wanting to 
check the cookie before continuing to accept the file upload.

To me it would make more sense to retrieve the data from the client in 
the Cgicc object so that the CgiEnvironment object can be used (for 
example, to retrieve cookies) before all of the data has been retrieved.

Apart from these issues, I've been very happy with the library. It's one 
of the few C++ libraries that actually makes use of the language features.

Regards,

Russell Kliese

P.S. What is the likelihood of a patch being accepted to solve these 
issues if it was done properly?