[Bug 1528251] Re: WARNING: no suitable primes in /etc/ssh/primes

[Launchpad Bug Tracker]

This bug was fixed in the package openssh - 1:7.3p1-1

---------------
openssh (1:7.3p1-1) unstable; urgency=medium

  * New upstream release (http://www.openssh.com/txt/release-7.3):
    - SECURITY: sshd(8): Mitigate a potential denial-of-service attack
      against the system's crypt(3) function via sshd(8).  An attacker could
      send very long passwords that would cause excessive CPU use in
      crypt(3).  sshd(8) now refuses to accept password authentication
      requests of length greater than 1024 characters.
    - SECURITY: ssh(1), sshd(8): Fix observable timing weakness in the CBC
      padding oracle countermeasures.  Note that CBC ciphers are disabled by
      default and only included for legacy compatibility.
    - SECURITY: ssh(1), sshd(8): Improve operation ordering of MAC
      verification for Encrypt-then-MAC (EtM) mode transport MAC algorithms
      to verify the MAC before decrypting any ciphertext.  This removes the
      possibility of timing differences leaking facts about the plaintext,
      though no such leakage has been observed.
    - ssh(1): Add a ProxyJump option and corresponding -J command-line flag
      to allow simplified indirection through a one or more SSH bastions or
      "jump hosts".
    - ssh(1): Add an IdentityAgent option to allow specifying specific agent
      sockets instead of accepting one from the environment.
    - ssh(1): Allow ExitOnForwardFailure and ClearAllForwardings to be
      optionally overridden when using ssh -W.
    - ssh(1), sshd(8): Implement support for the IUTF8 terminal mode as per
      draft-sgtatham-secsh-iutf8-00 (closes: #337041, LP: #394570).
    - ssh(1), sshd(8): Add support for additional fixed Diffie-Hellman 2K,
      4K and 8K groups from draft-ietf-curdle-ssh-kex-sha2-03.
    - ssh-keygen(1), ssh(1), sshd(8): Support SHA256 and SHA512 RSA
      signatures in certificates.
    - ssh(1): Add an Include directive for ssh_config(5) files (closes:
      #536031).
    - ssh(1): Permit UTF-8 characters in pre-authentication banners sent
      from the server.
    - ssh(1), sshd(8): Reduce the syslog level of some relatively common
      protocol events from LOG_CRIT.
    - sshd(8): Refuse AuthenticationMethods="" in configurations and accept
      AuthenticationMethods=any for the default behaviour of not requiring
      multiple authentication.
    - sshd(8): Remove obsolete and misleading "POSSIBLE BREAK-IN ATTEMPT!"
      message when forward and reverse DNS don't match.
    - ssh(1): Deduplicate LocalForward and RemoteForward entries to fix
      failures when both ExitOnForwardFailure and hostname canonicalisation
      are enabled.
    - sshd(8): Remove fallback from moduli to obsolete "primes" file that
      was deprecated in 2001 (LP: #1528251).
    - sshd_config(5): Correct description of UseDNS: it affects ssh hostname
      processing for authorized_keys, not known_hosts.
    - sshd(8): Send ClientAliveInterval pings when a time-based RekeyLimit
      is set; previously keepalive packets were not being sent.
    - sshd(8): Whitelist more architectures to enable the seccomp-bpf
      sandbox.
    - scp(1): Respect the local user's LC_CTYPE locale (closes: #396295).
    - Take character display widths into account for the progressmeter
      (closes: #407088).

 -- Colin Watson <cjwatson at debian.org>  Sun, 07 Aug 2016 22:45:26 +0100

** Changed in: openssh (Ubuntu)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1528251

Title:
  WARNING: no suitable primes in /etc/ssh/primes

Status in portable OpenSSH:
  Unknown
Status in openssh package in Ubuntu:
  Fix Released

Bug description:
  
  For instance when the KexAlgorithms option in sshd_config is set to include Diffie Hellman group exchange (e.g. diffie-hellman-group-exchange-sha256), and the /etc/ssh/moduli file is regenerated to include only 4096 bit primes, the ssh server may log the above warning message to /var/log/auth.log, probably because the ssh client trying to log in does not allow for the use of 4096 bit primes during the key exchange. The alleged problem is the reference to /etc/ssh/primes instead of /etc/ssh/moduli. It would appear that the file /etc/ssh/primes is neither used by ssh server, nor documented.

  I note that this error appears to have been reported in several places
  on the web in the past years, but to no avail (e.g.
  http://misc.openbsd.narkive.com/tZPNEoZk/no-suitable-primes)

  
  Release: Ubuntu 14.04.3 LTS
  Package: openssh-server, Version: 1:6.6p1-2ubuntu2.3

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