From: Rob Muhlestein <rmuhlestein@...>
Date: 2006-12-29T04:05:11+09:00
Subject: unsafe readline(), anything better?

Looking for a combination of readpartial() and readline() in order to
safely read a line of maxlen. IO.readline() appears to suffer from lacking
this maximum allowing DOS against servers reading HTTP headers, for
example, just by using sock.readline() alone, which is what
Net::HTTPResponse and others do:

   1974     class << HTTPResponse
   1975       def read_new(sock)   #:nodoc: internal use only 1976 httpv,
   code, msg = read_status_line(sock) 1977         res =
   response_class(code).new(httpv, code, msg) 1978
   each_response_header(sock) do |k,v| 1979           res.add_field k, v
   1980         end
   1981         res
   1982       end
   1983
   1984       private
   1985
   1986       def read_status_line(sock) 1987         str = sock.readline
   1988         m =
   /\AHTTP(?:\/(\d+\.\d+))?\s+(\d\d\d)\s*(.*)\z/in.match(str) o        r
   1989           raise HTTPBadResponse, "wrong status line: #{str.dump}"
   1990         m.captures
   1991       end

I know this is fundamentally a problem with the popular readline C libs
out there. Wish they had an nreadline like the sprintf and snprintf
additional function. Sure I could readchar() or readbytes() watching each
read for a newline, but that is just unfun. Have I overlooked something
obvious in my search? Hoping to not have to write my own safe/buffered IO
layer like I've had to do with other langs.

If there is enough interest, maybe I'll hack a readmaxline() method into
an IO patch to submit. Actually, on second thought, how about adding a
second parameter:

    ios.readline(sep_string=$/,maxlen=nil)

The tough question would then be whether to raise an LineTooLong exception
or just return what could be read of the line up to that point.

Thanks,

Rob