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Proposal: Prefer secure origins for powerful new web platform features

From: Chris Palmer <palmer@google.com>
Date: Fri, 27 Jun 2014 15:55:32 -0700
Message-ID: <CAOuvq218d+ZU5ZYhHkHbnd2KcxCxbrPQ_pU1pSU1169iY47PeA@mail.gmail.com>
To: "public-webappsec@w3.org" <public-webappsec@w3.org>, blink-dev <blink-dev@chromium.org>, security-dev <security-dev@chromium.org>, dev-security@lists.mozilla.org
Hi everyone,

Apologies in advance to those of you who will get this more than once,
due to the cross-posting. I wanted to get this to a wide audience, to
gather feedback and have a discussion involving as many interested
parties as possible (browser vendors, web developers, security
engineers, privacy advocates, et al.).

* Proposal

The Chrome Security team and I propose that, for new and particularly
powerful web platform features, browser vendors tend to prefer to make
the the feature available only to secure origins by default.

* Definitions

"Particularly powerful" would mean things like: features that handle
personally-identifiable information, features that handle high-value
information like credentials or payment instruments, features that
provide the origin with control over the UA's trustworthy/native UI,
access to sensors on the user's device, or generally any feature that
we would provide a user-settable permission or privilege to. Please
discuss!

"Particularly powerful" would NOT mean things like: new rendering and
layout features, CSS selectors, innocuous JavaScript APIs like
showModalDialog, or the like. I expect that the majority of new work
in HTML5 fits in this category. Please discuss!

"Secure origins" are origins that match at least one of the following
(scheme, host, port) patterns:

    * (https, *, *)
    * (wss, *, *)
    * (*, localhost, *)
    * (*, 127/8, *)
    * (*, ::1/128, *)
    * (file, *, —)
    * (chrome-extension, *, —)

This list may be incomplete, and may need to be changed. Please discuss!

A bug to define “secure transport” in Blink/Chromium:
https://code.google.com/p/chromium/issues/detail?id=362214

* For Example

For example, Chrome is going to make Service Workers available only to
secure origins, because it provides the origin with a new, higher
degree of control over a user's interactions with the origin over an
extended period of time, and because it gives the origin some control
over the user's device as a background task.

Consider the damage that could occur if a user downloaded a service
worker script that had been tampered with because they got it over a
MITM'd or spoofed cafe wifi connection. What should have been a nice
offline document editor could be turned into a long-lived spambot, or
maybe even a surveillance bot. If the script can only run when
delivered via authenticated, integrity-protected transport like HTTPS,
that particular risk is significantly mitigated.

* Background

Legacy platforms/operating systems have a 1-part principal: the user.
When a user logs in, they run programs that run with the full
privilege of the user: all of a user’s programs can do anything the
user can do on all their data and with all their resources. This has
become a source of trouble since the rise of mobile code from many
different origins. It has become less and less acceptable for a user’s
(e.g.) word processor to (e.g.) read the user’s private SSH keys.

Modern platforms have a 2-part security principal: the user, and the
origin of the code. Examples of such modern platforms include (to
varying degrees) the web, Android, and iOS. In these systems, code
from one origin has (or, should have) access only to the resources it
creates and which are explicitly given to it.

For example, the Gmail app on Android has access only to the user’s
Gmail and the system capabilities necessary to read and write that
email. Without an explicit grant, it does not have access to resources
that other apps (e.g. Twitter) create. It also does not have access to
system capabilities unrelated to email. Nor does it have access to the
email of another user on the same computer.

In systems with 2-part principals, it is crucial to strongly
authenticate both parts of the principal, not just one part.
(Otherwise, the system essentially degrades into a 1-part principal
system.) This is why, for example, both Android and iOS require that
every vendor (i.e. origin) cryptographically sign its code. That way,
when a user chooses to install Twitter and to give Twitter powerful
permissions (such as access to the device’s camera), they can be sure
that they are granting such capability only to the Twitter code, and
not to just any code.

By contrast, the web has historically made origin authentication
optional. On the web, origins are defined as having 3 parts: (scheme,
host, port), e.g. (HTTP, example.com, 80) or (HTTPS, mail.google.com,
443). Many origins use unauthenticated schemes like HTTP, WS, or even
FTP.

Granting permissions to unauthenticated origins is, in the presence of
a network attacker, equivalent to granting the permissions to any
origin. The state of the internet is such that we must indeed assume
that a network attacker is present.

* Thank You For Reading This Far!

We welcome discussion, critique, and cool new features!
Received on Friday, 27 June 2014 22:55:59 UTC

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