W3C home > Mailing lists > Public > public-webappsec@w3.org > December 2013

Re: Hashes/Nonce Source and unsafe-inline

From: Dionysis Zindros <dionyziz@gmail.com>
Date: Thu, 12 Dec 2013 16:00:46 -0800
Message-ID: <CAE-c3mdupFBmX83zK1YX-NkOD6=XdbURHxJQ3JxhA=sAMKLw=Q@mail.gmail.com>
To: Devdatta Akhawe <dev.akhawe@gmail.com>
Cc: Mike West <mkwst@google.com>, "public-webappsec@w3.org" <public-webappsec@w3.org>, Dan Veditz <dveditz@mozilla.com>
On Thu, Dec 12, 2013 at 3:34 PM, Devdatta Akhawe <dev.akhawe@gmail.com> wrote:
> Hi
>
> [creating a separate thread since there were other discussions ongoing
> in the other]
>
>> 2. 'unsafe-inline' is disabled if either a hash or nonce is present.
>>      [3] https://dvcs.w3.org/hg/content-security-policy/rev/8db37e53da82
>
> Imagine a website that wants to control what external scripts are
> loaded. The website uses inline  event handlers too. The hosts for
> external scripts can be dynamic (e.g., it is on a CDN) and thus it
> uses nonces to load them at runtime. In the new design, all the event
> handlers would stop working. I am not sure this is what we want.
>

Inline event handlers are insecure and prone to XSS, so we want to
block them. There's no point in enabling both unsafe-inline and (hash
or nonce) at the same time. The point of a hash or a nonce is to block
all inline scripts except the ones whitelisted. Allowing inline
scripts completely defeats the purpose of having hashes or nonces.

>
> Thanks
> Dev
>
Received on Friday, 13 December 2013 00:01:33 UTC

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