Re: [TLS] HTTPS client-certificate-authentication in browsers

Wan-Teh Chang <wtc@google.com> Fri, 29 July 2011 21:17 UTC

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Date: Fri, 29 Jul 2011 14:17:37 -0700
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From: Wan-Teh Chang <wtc@google.com>
To: Anders Rundgren <anders.rundgren@telia.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] HTTPS client-certificate-authentication in browsers
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On Mon, Jul 25, 2011 at 6:38 AM, Anders Rundgren
<anders.rundgren@telia.com>; wrote:
>
> On my wife's firefox the bank have deployed two certs and
> both of the show up when she is going to login.  If she
> takes the one marked "non-repudiation" you get a security
> error that only experts understand.

Anders,

Could you email me those two certs, or tell me their key types (RSA,
DSA, or elliptic curve) and the "key usage" and "extended key usage"
extensions?  I will take a look at the Firefox code that filters
client certificates for SSL client authentication.

I think the filtering algorithm should be:

1. If the key usage extension exists, it must contain the
digitalSignature bit (for the TLS rsa_sign, dsa_sign, and ecdsa_sign
client certificate types).

2. If the extended usage extension exists, it must contain the
id-kp-clientAuth (TLS WWW client authentication) purpose.

Note: this implies if neither the key usage nor the extended key usage
extension exists, the certificate may be used for SSL client
authentication.

Do you agree?

Thanks,
Wan-Teh Chang