[Bug 1981697] Re: KDC: weak crypto in default settings

[Sam Hartman]

>>>>> "Marc" == Marc Deslauriers <1981697 at bugs.launchpad.net> writes:

    Marc> Oh, so it only copies the file over on new installs, that
    Marc> makes sense, and could be easily changed in stable releases.

It's actually even less likely to cause problems than it might appear.
That config value should only be used by kdb5_util create.
Once /etc/krb5kdc/stash is created, I'd expect the encryption type in
that file will be used, and even if somehow kdc.conf were updated, it
would still continue to work.

We probably should start thinking about how to upgrade existing
databases, because we're going to want to do that before 3DES is removed
from the code.
That's going to be tricky because of the various replication and
database storage strategies.  For example a Freeipa database is handled
differently than a raw Kerberos database than an LDAP database.
But we don't need to solve any of that today, and whatever we can do to
make new realms work better will help that eventual upgrade process
along.

--Sam

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https://bugs.launchpad.net/bugs/1981697

Title:
  KDC: weak crypto in default settings

Status in krb5 package in Ubuntu:
  Confirmed
Status in krb5 package in Debian:
  Unknown

Bug description:
  Default setting in /etc/krb5kdc/kdc.conf, as installed from krb5-kdc in Ubuntu 22.04 Server:
  master_key_type = des3-hmac-sha1

  3DES was deprecated by NIST in 2017, i.e. give years ago! Reference:
  https://csrc.nist.gov/News/2017/Update-to-Current-Use-and-Deprecation-
  of-TDEA . This should not be a default since a very long time, and
  particularly not for new installations. If a compatibility with out-
  of-date installations is necessary, this should be explicitly made be
  the administrator.

  SHA-1 was deprecated as well, in 2011, i.e. eleven years ago!
  Reference:
  https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-131a.pdf
  .

  A reasonable default would probably be:
  master_key_type = aes256-cts-hmac-sha384-192

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: krb5-kdc 1.19.2-2
  ProcVersionSignature: Ubuntu 5.15.0-40.43-generic 5.15.35
  Uname: Linux 5.15.0-40-generic x86_64
  ApportVersion: 2.20.11-0ubuntu82.1
  Architecture: amd64
  CasperMD5CheckResult: pass
  Date: Thu Jul 14 12:34:22 2022
  InstallationDate: Installed on 2022-05-30 (45 days ago)
  InstallationMedia: Ubuntu-Server 22.04 LTS "Jammy Jellyfish" - Release amd64 (20220421)
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_IE.UTF-8
   SHELL=/bin/bash
  SourcePackage: krb5
  UpgradeStatus: No upgrade log present (probably fresh install)

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