On Thu, Jul 31, 2025 at 8:28 AM Cy Schubert <cy.schub...@cschubert.com> wrote:
>
> In message <CAM5tNy4XupPGXHMS0p0TK0Wf_zAg5bsOzx4C1K1e-_2b=3eyUw@mail.gmail.c
> om>
> , Rick Macklem writes:
> > On Thu, Jul 31, 2025 at 6:51=E2=80=AFAM Rick Macklem <rick.mack...@gmail.co=
> > m> wrote:
> > >
> > > On Thu, Jul 31, 2025 at 6:07=E2=80=AFAM Rick Macklem <rick.macklem@gmail.=
> > com> wrote:
> > > >
> > > > On Wed, Jul 30, 2025 at 9:24=E2=80=AFPM Benjamin Kaduk <bjkfbsd@gmail.c=
> > om> wrote:
> > > > >
> > > > > On Wed, Jul 30, 2025 at 10:36=E2=80=AFAM Rick Macklem <rick.macklem@g=
> > mail.com> wrote:
> > > > >>
> > > > >> On Mon, Jul 28, 2025 at 3:32=E2=80=AFPM Benjamin Kaduk <bjkfbsd@gmai=
> > l.com> wrote:
> > > > >> >
> > > > >> > On Mon, Jul 28, 2025 at 3:04=E2=80=AFPM Benjamin Kaduk <bjkfbsd@gm=
> > ail.com> wrote:
> > > > >> >>
> > > > >> >>
> > > > >> >> Note that MIT krb5 provides the gss_krb5_export_lucid_sec_context=
> > () API that does a lot of the work of getting useful bits out of an establi=
> > shed GSS security context.
> > > > >> >>
> > > > >> >
> > > > >> >
> > > > >> >
> > > > >> >
> > > > >> > And a bit more context on what is going on here and why kgssapi ha=
> > s to care:
> > > > >> > The GSS-API (RFC 2743) is all about a way to "establish a security=
> > context" (i.e., do crypto negotiation, authentication, sometimes authoriza=
> > tion, etc.) between two entities, the initiator and the acceprot, and then =
> > exchanging protected messages between the two (which can be either encrypte=
> > d or just integrity protection tags for otherweise cleartext data); later e=
> > xtensions included the ability to produce identical PRF output on both part=
> > ies, etc.. The details are "mechanism-specific", and for this purpose we'r=
> > e exclusively talking about the krb5 mechanism. The steps to establish the=
> > security context are complicated and sometimes fiddly, and in the general =
> > case can require a large number of round-trips between the initiator and ac=
> > ceptor before the security context is established. The individual message-=
> > protection parts are comparatively simple and amendable to implementation i=
> > n the kernel for processing efficiency.
> > > > >> > RFC 2743 also defines functions for GSS_Export_sec_context() and G=
> > SS_Import_sec_context(), that are designed essentially to pass information =
> > about an established security context from one process to another on the sa=
> > me machine (which are presumably using the same implementation and version =
> > of the implementation), so the contents of the exported blob are opaque and=
> > implementation-specific. We are abusing that mechanism to export informat=
> > ion about the security context that gssd has established and feed that info=
> > rmation into the kernel implementation of the per-message processing routin=
> > es. At present, this necessarily entails knowing the details of the implem=
> > entation-specific opaque blob that is the "export sec context token", which=
> > is what the sys/kgssapi/krb5/krb5_mech.c code is doing. But if we can get=
> > the information we want without breaking the abstraction barrier, such as =
> > via the gss_krb5_export_lucid_sec_context() API, we are in a more robust po=
> > sture overall and somewhat future-proofed against future evolution by MIT k=
> > rb5.
> > > > >> > (I note that recent Heimdal versions seem to also expose a gss_krb=
> > 5_export_lucid_sec_context() API, so part of the problem is just that the H=
> > eimdal in base is so old.)
> > > > >>
> > > > >> Well, here's some "not so good" news...
> > > > >> I've been trying to use gss_inquire_sec_context_by_oid(..) with the =
> > oid
> > > > >> for the GSS_KRB5_EXPORT_LUCID_SEC_CONTEXT_OID with version 1.
> > > > >> It kept failing.
> > > > >> The problem seems to be that "gctx->proto =3D=3D 4" in make_external=
> > _lucid_ctx_v1()
> > > > >> function. This function only knows about the 0 and 1 setting for gct=
> > x->proto.
> > > > >>
> > > > >> Any ideas, rick
> > > > >>
> > > > >
> > > > >
> > > > > I'm not seeing anything to suggest that a "gctx->proto" value of 4 is=
> > ever expected; it looks like it's supposed to just be 0 (for the legacy RF=
> > C 1964 format) or 1 (for the "CFX" format of RFC 4121, with wider sequence =
> > numbers for message-protection formats, etc.). So maybe it's worth posting=
> > your current WIP somewhere to take a closer look at what's going on.
> > > >
> > > > Yea, the debugging I did was flawed (I probably got the wrong offset
> > > > in the structure).
> > > > It is weird, though. If I do gss_inquire_sec_context_by_oid(&minor, ctx=
> > ,
> > > > OID_FOR_GSS_INQUIRE_SSPI_SESSION_KEY, &key), it
> > > > works and gives me the key and encryption type.
> > > >
> > > > If I do the same, but with the 12 byte OID for LUCID v1 (the 11 bytes f=
> > rom the
> > > > string + a 1 byte), it returns major =3D=3D GSS_S_COMPLETE, but no data=
> > and
> > > > a weird 39756046(decimal) or 0x25ea10e(hex) minor.
> > > > (Oh, and I tried gss_krb5_export_lucid_sec_context() and got the same
> > > > weird error.)
> > > --> Now (after doing a "make buildworld"), gss_krb5_export_lucid_sec_cont=
> > ext()
> > > returns GSS_S_BAD_MECH. Looking at the src, that error has to be fro=
> > m
> > > gss_inquire_sec_context_by_oid(). So, same function fails, but a dif=
> > ferent
> > > error return?
> > >
> > > It looks like "gssint_get_mechanism (ctx->mech_type)" is failing.
> > > I'm currently just passing GSS_C_NULL_OID into gss_init_sec_context(),
> > > but I've also tried the Kerberos 9 byte OID (both work, in the sense that
> > > gss_init_sec_context() seems to work, except that the actual_mech_type
> > > returned by it has a bogus pointer in the reply).
> > > --> It looks like the "mech_type" field of "ctx" is busted, for some reas=
> > on?
> > >
> > > I'm going to try building krb5 from ports and linking to that, to see if =
> > it
> > > does the same thing.
> > Finally some good news...
> > All I did was "pkg install krb5" and then linked the gssd to the libraries =
> > in
> > /usr/local/lib and it worked!!
>
> gssapi/gssapi.h from krb5/lib/gssapi/generic is overwritten by our
> lib/libgssapi. As we have two the MIT gssapi.h is put in
> /usr/include/gssapi_krb5/gssapi.h.
>
> This patch should fix the problem. I haven't tested this yet.
>
> diff --git a/usr.sbin/gssd/Makefile b/usr.sbin/gssd/Makefile
> index 569e2c7e18f5..4c9d342c48c3 100644
> --- a/usr.sbin/gssd/Makefile
> +++ b/usr.sbin/gssd/Makefile
> @@ -14,7 +14,7 @@ LIBADD= gssapi
> .if ${MK_MITKRB5} != "no"
> # MIT KRB5
> LIBADD+= krb5 k5crypto krb5profile krb5support
> -CFLAGS+= -DMK_MITKRB5=yes
> +CFLAGS+= -DMK_MITKRB5=yes -Iinclude/gssapi_krb5
> .else
> # Heimdal
> LIBADD+= krb5 roken
Just to be clear to everyone, this might allow it to be built after
being patched for MIT, but it does not fix it so that it works.
I will be debugging the patches that makes it works later to-day.
You state that Heimdal didn't have a gssapi.h, but it does and it
has always been included in gssd.c. (It was the other ones like
gssapi_krb5.h, which needs the MIT gssapi.h.)
rick
>
>
> >
> > Now I can test/debug the changes.
> >
> > Btw, the stuff in /usr/local/include/gssapi are correct and not messed up
> > like the stuff in /usr/include/gssapi. (The ones in /usr/local/include defi=
> > ne
> > GSS_DLLIMP for example.)
> >
> > I'm going to leave figuring out why the libraries in /usr/lib are messed up
> > to someone else.
> >
> > rick
> >
>
>
> --
> Cheers,
> Cy Schubert <cy.schub...@cschubert.com>
> FreeBSD UNIX: <c...@freebsd.org> Web: https://FreeBSD.org
> NTP: <c...@nwtime.org> Web: https://nwtime.org
>
> e**(i*pi)+1=0
>
>
