[Bug 1643708] Re: Add SPNEGO special case for NTLMSSP+MechListMIC

[Robie Basak]

Hi Sam,

Thank you for weighing in on this. I appreciate your opinion.

On Fri, Jan 20, 2017 at 02:03:11PM -0000, Sam Hartman wrote:
> So, while I think your concern is reasonable, I'd urge you to consider
> that you're setting a really high bar here for backporting a patch that
> an interoperability-conscious upstream has vetted.

I'm more bothered that we've considered and weighed up the non-Windows
use case. I hadn't yet set a bar - I was just asking for regressions in
all use cases to be considered and that consideration documented, as is
SRU policy. This helps us reach a decision, and should ideally have
happened first, before the SRU was accepted into the proposed pocket.

I'm convinced by your arguments, so I'm happy with the testing already
performed. Thank you to Bruce and Joshua for your work on this.

We don't usually release SRUs on Fridays in case of regression, but I'd
be happy to release this on Monday, subject to the usual checks.

Robie

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https://bugs.launchpad.net/bugs/1643708

Title:
  Add SPNEGO special case for NTLMSSP+MechListMIC

Status in krb5 package in Ubuntu:
  Fix Released
Status in krb5 source package in Trusty:
  Fix Committed
Status in krb5 source package in Xenial:
  Fix Committed
Status in krb5 source package in Yakkety:
  Fix Committed

Bug description:
  [Impact]
  MS-SPNG section 3.3.5.1 documents an odd behavior the SPNEGO layer
  needs to implement specifically for the NTLMSSP mechanism.  This is
  required for compatibility with Windows services.

  Upstream commit:
  https://github.com/krb5/krb5/commit/cb96ca52a3354e5a0ea52e12495ff375de54f9b7

  We've run into this issue with Linux to Windows negotiation with
  encrypted http using GSSAPI.

  [Test Case]

  create a file with some credentials:

  $ echo F23:guest:guest > ~/ntlmcreds.txt
  $ export NTLM_USER_FILE=~/ntlmcreds.txt
  $ python
  import gssapi

  spnego = gssapi.raw.oids.OID.from_int_seq('1.3.6.1.5.5.2')
  c = gssapi.creds.Credentials(mechs=[spnego], usage='initiate')
  tname = gssapi.raw.names.import_name("F23/server", name_type=gssapi.raw.types.NameType.hostbased_service)
  ac = gssapi.creds.Credentials(mechs=[spnego], usage='accept')

  seci = gssapi.SecurityContext(creds=c, name=tname, mech=spnego, usage='initiate')
  seca = gssapi.SecurityContext(creds=ac, usage='accept')
  it = seci.step(token=None)
  ot = seca.step(token=it)
  it = seci.step(token=ot)
  ot = seca.step(token=it)
  it = seci.step(token=ot)

  e = seci.wrap("Secrets", True)
  o = seca.unwrap(e.message)

  o.message
  'Secrets'

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