220 lines
7.7 KiB
HTML
220 lines
7.7 KiB
HTML
<!DOCTYPE html>
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<html lang="en"><head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<style>
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body {
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max-width: 30em;
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margin-left: 2em;
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}
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p.center {text-align:center;}
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</style>
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<link rel="shortcut icon" href="../rho.ico">
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<title>How Browser Security Should be Done</title>
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</head><body>
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<p><a href="./index.html"> To Home page</a> </p>
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<h1>How Browser Security Should be Done</h1>
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<p>
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Cryptography should be written around user concepts, not
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cryptographer concepts. </p>
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<p>
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The cryptography should be written underneath session
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management and logon management, instead of session
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management being written on top of the cryptography.
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The cryptography should be written to give effect to
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user expectations, rather than trying to get the users
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to behave like Ann and Bob in the text book
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illustrations of how to use cryptography correctly.
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</p>
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<p>
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The process whereby things go wrong is that one produces
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a completely sound solution to one part of the problem,
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waves away the all the rest of the problem as mere
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details, and then a gigantic mud brick ziggurat
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gradually accretes around that perfectly sound solution,
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as for example ssl-https-pki. </p>
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<p>
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When the disastrous abortion know as https was first
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designed it should have been obvious that everything
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really important relates to logins and sessions and that
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the rest can be treated as a login by "anon 37283" with
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the null password, and that therefore the cryptography
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<em>and the browser user interface</em> needs to
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implement logins and sessions, rather than providing a
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pile of matchsticks and glue with which the website can
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implement something that sort of mostly behaves rather
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like logins and sessions. </p>
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<p>
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It <em>should</em> have been obvious that logging in on
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a user interface provided by a web page, provided by
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html code, was entirely insecure – the problem of
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spoofed logins was well known at the time. So what we
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needed, from day one, was a secure login that was in the
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browser chrome, not the web page – and no other form of
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secure login supported. </p>
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<p>
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When the user creates a username and password, this
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should by default automatically create a bookmark in his
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contacts folder, much as an email client usually does
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when you post a reply. To reduce the risk that
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the user may be fooled into using a hostile
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client, the user interface for entering password
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and username should never pop up except by the
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user clicking on a login button in the browser
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chrome, or clicking on a login bookmark. Not only
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should the user never enter his password and user
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name on a web page, but also there should never be login
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buttons on a web page. </p>
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<p>
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To make this chrome based login cryptographically secure
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against active and passive attacks on the wire,
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phishing, and social engineering. </p>
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<ul>
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<li><p>
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If the user enters the user name and password incorrectly,
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then he has to pass a reverse Turing test before entering
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the password again, to prevent scripts from trying
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millions of passwords. So if an attacker has tried to
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guess passwords, the website will inform the user that n
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unsuccessful login attempts have taken place against his
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user name and ask him to pass the reverse Turing
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test. </p></li><li><p>
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The user interface to create a connection never pops up
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spontaneously, but only as a direct result of the user
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choosing to cause it to pop up, typically by clicking
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on a bookmark in his account list, or by clicking on
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the login widget in the browser chrome.
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</p></li><li><p>
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We use password-authenticated key agreement to construct a strong frequently changing
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secret from the short infrequently changing secret
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password. Thus if the user logs in to the wrong host –
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or to an adversary pretending to be the correct host in a
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man in the middle attack, the false server does not get
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the password or the session secret. We also hash
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the password with server global key. </p></li><li><p>
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Password-authenticated key agreement also ensures that a passive eavesdropper will not
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discover the password or the strong session secret. </p>
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</li>
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</ul>
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<p>
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This tells us how the login will avoid being phished,
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but how shall we set up a login in the first place.
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The user needs a secure connection to the correct
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website. We know how to do secure connections, trouble is
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identifying the correct website. </p>
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<p>
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To ensure that the website is that which is
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intended, we use yurls, a form of Zooko identity.
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</p>
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<p>
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The person using the client needs to login and has to
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know and manage their logged in status. The user
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login status should be displayed in the chrome on every
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logged in web page, and the server has to know that the
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user knows his login status, has to know the login
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status not only of the user, but of the web page that
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the user has clicked on that generated this request to
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this server. </p>
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<p>
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The state of being logged in should guarantee privacy
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and authenticity – that only the client and the server
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can know what they are communicating, and that no one
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else should be able to pass himself off as client or
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server, or modify their communications. </p>
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<p>
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Everything should have been written around the user
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concepts of "logging in" "a logged in page", and
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"logging out", and should have made those user concepts
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real, made them into pages with appropriate built in
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cryptographic behaviors. </p>
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<p>
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The user concept of "logged in" has to be real rather
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than superficially simulated by server side code, and
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thus has to really have the cryptographic
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characteristics that the user expects – which at present
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it generally does not, leading to such attacks as the
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session fixation attack. </p>
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<p>
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The user should have a list of contact web sites as he
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does in Skype and AIM, and when he clicks on that
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bookmark, the logon page, provided by his browser rather
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than the website, should provide the true name of the
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web site, if it has a certified true name, and/or the
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title of the bookmark, the petname, if it has one. And
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when logged on, any logged on page should show in the
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chrome the petname, or truename of the website, and the
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logon name – who the website thinks is logged on.
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</p>
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<p>
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Single signon should work like Skype, and should be
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built into the protocol at the base level, in the
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cryptography, and in the chrome, and in the
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bookmark/petname management. You click on a petname in
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the Skype contact list – the Skype folder of the login
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folder of your bookmark folder, and lo, because you are
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securely logged in to Skype, and the web site also
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securely logged into Skype, you come to be securely
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connected to each other under your Skype names without
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any further mucking around with passwords. The web
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page then displays in the chrome the web site’s Skype
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name, and your Skype name. Single sign on should also
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allow web site push, if the end user is logged in to the
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single sign on server and the website is in his contact
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list and the end user has not prohibited such push.
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Thus the browser should be, or be tightly integrated
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with, a messaging service provided by the single sign on
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service. </p>
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<p>
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The web application framework should ensure that code
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providing a response to a user’s click on a web page
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that is not logged in does not have write access to
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database records corresponding to that user – that only
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a click on a logged in web page in the user’s browser
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can result in changes to user records on the server.
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</p>
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<p style="background-color : #ccffcc; font-size:80%">These documents are
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licensed under the <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative
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Commons Attribution-Share Alike 3.0 License</a></p>
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</body></html> |