Re: Pending OpenSSH release: contains Kerberos/GSSAPI changes

[Nicolas Williams <Nicolas.Williams%sun.com@localhost>]

On Fri, Jan 30, 2004 at 04:43:51PM -0500, Jeffrey Hutzelman wrote:
> Indeed, it does.  The server is not supposed to check the state of the 
> mutual_flag of a context accepted for gssapi-with-mic user auth.  I know 
> the draft is not entirely clear on this point; would it help if there were 
> text indicating the server MUST NOT do this?

For completeness' sake, yes.  The client (SHOULD NOT | MAY) set
GSS_C_MUTUAL for gssapi-with-mic, but the server MUST ignore the state
of the GSS_C_MUTUAL flag for gssapi-with-mic.

> Also, I've not actually read this code, other than what's quoted above, but 
> I hope that's not the only place that flags are checked.  I'm assuming the 
> openssh code actually implements -07 and 'gssapi-with-mic'.  In the new 
> method, the client's final message is either SSM_MSG_USERAUTH_GSSAPI_MIC or 
> SSH_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, depending entirely on whether 
> GSS_C_INTEG_FLAG is set.  The server is REQUIRED to fail the authentication 
> if the client sends the wrong message; this means the value of 
> GSS_C_INTEG_FLAG must be tested.

Right.  Further, the text should say that the server MAY always reject
SSH_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE since there's no generic
interface for determining whether a context doesn't have the GSS_C_INTEG
flag set because the client left it off or because the mechanism doesn't
support GSS_C_INTEG.

Nico
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