[whatwg] Spec comments, sections 1-2

Ian Hickson ian at hixie.ch
Wed Jul 29 01:39:05 PDT 2009

On Wed, 15 Jul 2009, Aryeh Gregor wrote:
> In
> "If position is not past the end of input, return to the top of the
> step labeled loop in the overall algorithm (that's the step within
> which these substeps find themselves)."
> Why not just "go to step 9"?

Which part specifically are you saying should be changed? I'm not sure I 

> In any event this is inconsistent with
>, which says
> "If position is not past the end of input, return to the top of step 9
> in the overall algorithm (that's the step within which these substeps
> find themselves)."

I guess I didn't screw that one up yet. :-) I originally wrote algorithms 
using numeric step jumps, then when editing them I broke a bunch of jumps 
(adding steps but not updating numbers), and so whenever I edit an 
algorithm now, I make it symbolic rather than numeric.

> Either both should say "the top of step 9" or both should say "the top
> of the step labeled loop".

There is value in not changing them unless they are actually broken -- 
when I edit the spec, there's always a risk I'll break something.

> I don't see the value in the whole "in the overall algorithm . . ." 
> part, since in context there's no ambiguity with just giving the number.

For now -- what if I later add a dozen more substeps?

> "If sign is "positive", return value, otherwise return 0-value."
> I initially read "0-value" as a single word, like "p-value" or
> whatever.  Perhaps it should have spaces to make it more immediately
> obvious that it's subtraction ("0 - value").

I've rephrased this.

> In 2.6.2:
> The specification says that user agents may serve HTTPS content as 
> though it were unencrypted.  For instance, an example states: "If a user 
> connects to a server with a self-signed certificate, the user agent 
> could allow the connection but just act as if there had been no 
> encryption."  If this is done, however, man-in-the-middle attacks become 
> trivial, unless the user is expected to notice the lack of encryption 
> (unlikely).
> For instance, suppose a user navigates to PayPal and bookmarks it. 
> PayPal is configured so if you try using HTTP (e.g., typing "paypal.com" 
> in the URL bar), it will redirect to HTTPS.  Therefore the user will 
> bookmark a URL such as https://www.paypal.com/.  Now suppose the user 
> later attempts to access this site from the bookmark with a MITM present 
> (e.g., a free wireless router placed in a public place by a malicious 
> person).
> The router can intercept the HTTPS request, make its own identical HTTPS 
> request, and return the results to the original HTTPS request, but 
> signed with its own key instead of the original.  If the user agent 
> behaves as described in the example, the only way for the user to notice 
> this is to notice that the URL bar looks different, or whatever visual 
> cue the browser uses.  If the user agent raises a prominent scary 
> warning or even makes it difficult for the user to continue, on the 
> other hand, there's no way for the attacker to prevent this, AFAIK.
> The section should prohibit user agents from displaying self-signed 
> pages without at least giving a warning.  Or, at a minimum, it should 
> strongly discourage it.  Currently it seems to indicate that this 
> behavior is acceptable.  As far as I know, existing browsers all present 
> scary warnings for self-signed pages (probably so scary as to be 
> misleading, in fact, but that's a separate issue).

I've required UAs to catch this case and added this example.

> In 2.7:
> "User agents must at a minimum support the UTF-8 and Windows-1252
> encodings, but may support more.
> "It is not unusual for Web browsers to support dozens if not upwards
> of a hundred distinct character encodings."
> Why aren't the most important ones listed as requirements?

They are. UTF-8 and 1252 are the most important ones.

> This seems to be contrary to the usual HTML 5 philosophy of mandating 
> (or at least precisely specifying) existing behavior that's required for 
> compatibility.

Which others are needed for compatibility?

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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