Re: certificate problem for *.github.com

From: Jeff King <peff@peff.net>
Date: Nov 4, 2010, 15:46 UTC
Message-ID: <20101104154600.GA30026@sigill.intra.peff.net>
In-Reply-To: <20101104162135.47chayboagwwkcc8@webmail.uu.se>

On Thu, Nov 04, 2010 at 04:21:35PM +0100, Mattia Tomasoni wrote:

Show 5 quoted lines

> I get:
> certificate common name `*.github.com' doesn't match requested host
> name `github.com'
> 
> wget --no-check-certificate works...

The problem is that wildcard names in certificates are not well-specified. RFC 2818 leaves this particular case (matching "*.domain" to "domain") ambiguous:

  Names may contain the wildcard character * which is considered to
  match any single domain name component or component fragment. E.g.,
  *.a.com matches foo.a.com but not bar.foo.a.com. f*.com matches
  foo.com but not bar.com.

RFC 2595 specifically outlaws it, but is talking about other non-HTTP protocols (it is for TLS with IMAP, POP, and ACAP):

  A "*" wildcard character MAY be used as the left-most name component
  in the certificate.  For example, *.example.com would match
  a.example.com, foo.example.com, etc. but would not match example.com.

So you can either send a bug report to wget to handle this case better, or you can complain to github not to use wildcard certificates in this way.

-Peff