Re: [Qemu-devel] [PATCH] io: ignore case when matching websockets HTTP headers

[Daniel P. Berrange]

On Mon, Feb 27, 2017 at 03:20:37PM -0600, Eric Blake wrote:
> On 02/27/2017 02:14 PM, Daniel P. Berrange wrote:
> > According to RFC7230 Section 3.2, header field name is case-insensitive.
> > Convert the header data into all lowercase before doing string matching
> > on the headers.
> > 
> > Signed-off-by: Daniel P. Berrange <address@hidden>
> > ---
> >  io/channel-websock.c | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> > 
> 
> > @@ -223,7 +223,7 @@ static int 
> > qio_channel_websock_handshake_process(QIOChannelWebsock *ioc,
> >  static int qio_channel_websock_handshake_read(QIOChannelWebsock *ioc,
> >                                                Error **errp)
> >  {
> > -    char *handshake_end;
> > +    char *handshake_end, *tmp;
> >      ssize_t ret;
> >      /* Typical HTTP headers from novnc are 512 bytes, so limiting
> >       * total header size to 4096 is easily enough. */
> 
> Drive-by grammar nit: s/easily/easy/
> 
> > @@ -249,9 +249,13 @@ static int 
> > qio_channel_websock_handshake_read(QIOChannelWebsock *ioc,
> >          }
> >      }
> >  
> > +    for (tmp = (char *)ioc->encinput.buffer; tmp < handshake_end; tmp++) {
> > +        *tmp = g_ascii_tolower(*tmp);
> > +    }
> > +
> >      if (qio_channel_websock_handshake_process(ioc,
> >                                                (char *)ioc->encinput.buffer,
> > -                                              ioc->encinput.offset,
> > +                                              handshake_end - (char 
> > *)ioc->encinput.buffer,
> 
> I'm not sure why this change is here; nothing else in the patch changed
> ioc->encinput.offset.

It is a related bug. The ioc->encinput buffer contains upto 4096
bytes, but that data may cover both the header & payload. The
handshake_end pointer refers to the end of the header region.
So if we just pass encinput.offset, then handshake_process()
will be searching part of the payload as well as the header.
This might cause it do match the wrong data. I guess I should
have made that clear in the commit, or even tput it in a
separate commit

Regards,
Daniel
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