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> You have mentioned this before, but is there anything
> which stops you from using TLS/SSL on all the hops
> *after* the firewall?
No, but you lose the ability to authenticate the original client with
SSL client certs. It also requires the server to have complete trust in
the operation and bug-free-ness of any intermediate SSL hops. In
essence, you have to trust the SSL intermediary as much as you trust the
server itself. But if you do that, then why is it in the DMZ? :)
> That first GET is for the hypertext that contains the POE link, correct.
So the first part of using POE to make HTTP reliable is to double the
number of HTTP interactions. And then, of course, you have the issue of
the unreliability of the initial GET. I'm not saying that to be cute,
but if the GET-POE-link fails, the server could possible have "stranded"
URL's waiting for the client to GET the POST response. (Er, that
wording's a bit muddled, but I hope you see what I mean.)
> What I don't understand is the underlying assumption that
> Basic and Digest are the end of the line for HTTP authentication.
Probably because there's been effectively no work done in the past
decade. The two mechanisms you mention -- WS-Security UserName profile,
and Atom authentication -- are the same thing as Digest or BasicAuth in
that they require a shared secret between the client and server. (And
is it really true that the second mechanism only exists because of a
mis-feature in Apache CGI?)
User-chosen passwords are notoriously easy to guess. The WS-Security
UserName profile puts the password at the end of the digest, meaning an
attacker can pre-compute the first part of the SHA based solely on the
plaintext. It's done that way on purpose, but understand the
trade-offs. It's also unfortunate that Atom WSSE didn't include any of
the countermeasures described in the standard. (See lines 132-154 of
Like Digest and BasicAuth, the two you mentioned require both parties to
use that shared secret on every interaction. It's just like having to
type your password into the shell after every command.
Rich Salz, Chief Security Architect
DataPower Technology http://www.datapower.com
XS40 XML Security Gateway http://www.datapower.com/products/xs40.html