[Bug 1668093] Re: ssh-keygen -H corrupts already hashed entries

[ChristianEhrhardt]

On 
git://anongit.mindrot.org/openssh.git

With bisect helper:
$cat ../test-ssh.sh 
#!/bin/bash
set -ux

make clean
autoreconf && ./configure && make -j4
if [[ $? -ne 0 ]]; then
        # skip build issue
        exit 125
fi

rm ~/.ssh/known_hosts /root/.ssh/known_hosts.old /root/.ssh/known_hosts
./ssh-keyscan 10.245.71.133 > ~/.ssh/known_hosts
./ssh-keygen -H
./ssh-keygen -H
# here .old and current should have no diff
# no diff = still ok, diff = broken - diff RC matches that
diff -q /root/.ssh/known_hosts.old /root/.ssh/known_hosts


$ git bisect start V_7_2_P2 V_6_6_P1

Gives me:

$ git bisect log
# bad: [5c35450a0c901d9375fb23343a8dc82397da5f75] update versions for release
# good: [19158b2447e35838d69b2b735fb640d1e86061ea]  - (djm) Release OpenSSH 6.6
git bisect start 'V_7_2_P2' 'V_6_6_P1'
# bad: [39e2f1229562e1195169905607bc12290d21f021] upstream commit
git bisect bad 39e2f1229562e1195169905607bc12290d21f021
# skip: [08c0eebf55d70a9ae1964399e609288ae3186a0c] upstream commit
git bisect skip 08c0eebf55d70a9ae1964399e609288ae3186a0c
# good: [f067cca2bc20c86b110174c3fef04086a7f57b13] upstream commit
git bisect good f067cca2bc20c86b110174c3fef04086a7f57b13
# bad: [fe8a3a51699afbc6407a8fae59b73349d01e49f8] upstream commit
git bisect bad fe8a3a51699afbc6407a8fae59b73349d01e49f8
# good: [9010902954a40b59d0bf3df3ccbc3140a653e2bc] upstream commit
git bisect good 9010902954a40b59d0bf3df3ccbc3140a653e2bc
# bad: [3fdc88a0def4f86aa88a5846ac079dc964c0546a] upstream commit
git bisect bad 3fdc88a0def4f86aa88a5846ac079dc964c0546a
# bad: [9e06a0fb23ec55d9223b26a45bb63c7649e2f2f2] upstream commit
git bisect bad 9e06a0fb23ec55d9223b26a45bb63c7649e2f2f2
# good: [f101d8291da01bbbfd6fb8c569cfd0cc61c0d346] upstream commit
git bisect good f101d8291da01bbbfd6fb8c569cfd0cc61c0d346
# bad: [cecb30bc2ba6d594366e657d664d5c494b6c8a7f] upstream commit
git bisect bad cecb30bc2ba6d594366e657d664d5c494b6c8a7f
# good: [c29811cc480a260e42fd88849fc86a80c1e91038] upstream commit
git bisect good c29811cc480a260e42fd88849fc86a80c1e91038
# good: [ec3d065df3a9557ea96b02d061fd821a18c1a0b9] upstream commit
git bisect good ec3d065df3a9557ea96b02d061fd821a18c1a0b9
# first bad commit: [cecb30bc2ba6d594366e657d664d5c494b6c8a7f] upstream commit


The offending commit you want to report in your upstream bug is:
cecb30bc2ba6d594366e657d664d5c494b6c8a7f is the first bad commit
commit cecb30bc2ba6d594366e657d664d5c494b6c8a7f
Author: djm at openbsd.org <djm at openbsd.org>
Date:   Sun Jan 18 21:49:42 2015 +0000

    upstream commit
    
    make ssh-keygen use hostkeys_foreach(). Removes some
     horrendous code; ok markus@


Upstream accidentally dropped the "non-overwrite" feature of ssh-keygen -H, but it is part of a much bigger rework, therefore this is nothing we just can/want to revert.

** Tags added: needs-upstream-report

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to openssh in Ubuntu.
https://bugs.launchpad.net/bugs/1668093

Title:
  ssh-keygen -H corrupts already hashed entries

Status in openssh package in Ubuntu:
  Confirmed

Bug description:
  xenial @ 1:7.2p2-4ubuntu2.1 on amd64 has this bug. trusty @
  1:6.6p1-2ubuntu2.8 on amd64 does not have this bug. I have not tested
  any other ssh versions.

  The following should reproduce the issue:

  #ssh-keyscan XXXX > ~/.ssh/known_hosts
  # ssh root at XXXXX
  Permission denied (publickey).
  # ssh-keygen -H
  /root/.ssh/known_hosts updated.
  Original contents retained as /root/.ssh/known_hosts.old
  WARNING: /root/.ssh/known_hosts.old contains unhashed entries
  Delete this file to ensure privacy of hostnames
  # ssh root at XXXXXX
  Permission denied (publickey).
  # ssh-keygen -H
  /root/.ssh/known_hosts updated.
  Original contents retained as /root/.ssh/known_hosts.old
  WARNING: /root/.ssh/known_hosts.old contains unhashed entries
  Delete this file to ensure privacy of hostnames
  # ssh root at XXXXX
  The authenticity of host 'XXXXXX' can't be established.
  RSA key fingerprint is XXXXXX.
  Are you sure you want to continue connecting (yes/no)?

  # diff known_hosts.old known_hosts
  1c1
  < |1|BoAbRpUE3F5AzyprJcbjdepeDh8=|x/1AcaLxh45FlShmVQnlgx2qjxY= XXXXX
  ---
  > |1|nTPsoLxCugQyZi3pqOa2pc/cX64=|bUH5qwZlZPp8msMGHdLtslf3Huk= XXXXX

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1668093/+subscriptions