arcfour: hmac-md5 vs. md5

[Elrond]

Okay,

this is still about TGS. I just noticed, that we have too
many buttons (parameters) to press and try stuff. So I
decided to start from scratch and look only at one
parameter:

arcfour-hmacs default checksum.
Either hmac-md5 or plain-md5 (MD_RSA_MD5).
(I modified crypto-rc4.c for this "parameter change").


Other parameters:
        cipher: "arcfour-hmac" only.
        preauth: enabled
        subkey in TGS: enabled


w2k3-kdc:

        Sending a TGS with hmac-md5 gets me a "Message
        stream modified" from the w2k3-kdc.

        Doing the same with plain-md5 gets me a response,
        that shishi can't decrypt.

heimdal-kdc:
        Version: 0.7.2 from Debian/testing

        Both variants work and I can't really discover any
        difference.

        Both give this warning from shishi at TGS-time:

        "libshishi: warning: KDC bug: Reply encrypted using wrong key."


>From my limited point of view, this looks like shishi and
heimdal are consistent to each other with the hmac-md5, but
shishi and w2k3 do not seem to share this.

This is particular confusing to me, as arcfour-hmac was
invented by the guys at ms. So either their spec isn't
correct or heimdal and you seem to have misread it (no
reproach intended!).

So what next?


    Elrond