Re: css3-fonts: should not dictate usage policy with respect to origin

if EvilCompany does not include an Origin header in its request, then
BigCompany could not distinguish that request as coming from  a pre-HTML5 UA
(i.e., current conditions), in which this case devolves to the current read
scenario;

if BigCompany does not respond to fetches not containing an Origin, then
again EvilCompany can guess an origin that permits access, resulting in a
fetch;

EvilCompany does not need to use a UA, but can construct their own HTTP
client to accomplish this;

the scenario you offer only prevents access if *every* HTTP client, whether
UA or not, respects SOR;

On Thu, Jun 30, 2011 at 3:59 PM, John Daggett <[email protected]> wrote:

>
> Glenn Adams wrote:
>
> > Regarding the last, please show me an attack based on font access that
> > SOR prevents.
>
> One possible attack scenario:
>
> BigCompany decides to design a new logo.  They commission a font
> containing a special glyph with that logo in it.  An access-restricted
> site is created using that custom font.  EvilCompany, a competitor,
> would like to know about that logo before it is released publicly.  They
> insert script in web ads on popular sites that systematically attempt
> to guess possible access-restricted URLs for the custom font.  An
> employee of BigCompany hits one of the pages on an external site
> containing one of EvilCompany's webads.
>
> If no origin restriction exists, the web ad code can access the font as
> long as they guess the right access-restricted URL and an
> employee of BigCompany happens to have access.  The script inserted in a
> webad by EvilCompany accesses the custom logo glyph and sends it back to
> an EvilCompany-controlled site.
>
> If font loads are restricted to same origin and the BigCompany hasn't
> explicitly enabled cross-origin loading via CORS, the web ad code will
> *never* be able to load the font even if their code guesses the right
> access-restricted URL, since it's origin is different.
>
> The scenario is the same one as in the WebGL example I noted earlier,
> without same origin restrictions content can be accessed via means
> that are not immediately obvious to the naive author.
>
> Regards,
>
> John Daggett
>