やるきなし

sid で ~/.ssh/id_dsa を用いた passphrase での login ができなくなった．ssh -v で調べてみると

debug1: Skipping ssh-dss key /home/myn/.ssh/id_dsa for not in PubkeyAcceptedKeyTypes

とのこと．とのことで，~/.ssh/config に

Host *
    PubkeyAcceptedKeyTypes +ssh-dss

とかを書いておけば id_dsa による共通鍵認証が利用できるようになる．/usr/share/doc/openssh-client/changelog.Debian.gz によれば

openssh (1:7.1p1-1) unstable; urgency=medium

  * New upstream release (http://www.openssh.com/txt/release-7.0, closes:
    #785190):
    - Support for the legacy SSH version 1 protocol is disabled by default
      at compile time.
    - Support for the 1024-bit diffie-hellman-group1-sha1 key exchange is
      disabled by default at run-time.  It may be re-enabled using the
      instructions at http://www.openssh.com/legacy.html
    - Support for ssh-dss, ssh-dss-cert-* host and user keys is disabled by
      default at run-time.  These may be re-enabled using the instructions
      at http://www.openssh.com/legacy.html
(snip)
<pre>

<p><a href="http://www.openssh.com/legacy.html">http://www.openssh.com/legacy.html</a>によると

<pre>
OpenSSH 7.0 and greater similarly disables the ssh-dss (DSA) public key algorithm. It too is weak and we recommend against its use. It can be re-enabled using the HostkeyAlgorithms configuration option:

とのこと．どうやら鍵ペアを作りなおす時期になったらしい．確かに10年以上同じ鍵を使っている．