[Bug 1863930] Re: SSH 1.99 clients fail to connect to openssh-server 1:7.6p1-4ubuntu0.3

[Christian Ehrhardt ]

Thanks Kyle for the great report and prepping a fix already.
offending: 97f4d3083 is in >=1%7.6p1-1
fix: 9e9c4a7e5 is in >=1%7.7p1-1
fix: c9c1bba06 is in >=1%7.7p1-1

Matching that with versions in Ubuntu means only Bionic should be
affected.

 openssh | 1:5.9p1-5ubuntu1    | precise          | source
 openssh | 1:5.9p1-5ubuntu1.10 | precise-security | source
 openssh | 1:5.9p1-5ubuntu1.10 | precise-updates  | source
 openssh | 1:6.6p1-2ubuntu1    | trusty           | source
 openssh | 1:6.6p1-2ubuntu2.13 | trusty-security  | source
 openssh | 1:6.6p1-2ubuntu2.13 | trusty-updates   | source
 openssh | 1:7.2p2-4           | xenial           | source
 openssh | 1:7.2p2-4ubuntu2.8  | xenial-security  | source
 openssh | 1:7.2p2-4ubuntu2.8  | xenial-updates   | source
 openssh | 1:7.2p2-4ubuntu2.9  | xenial-proposed  | source
 openssh | 1:7.6p1-4           | bionic           | source
 openssh | 1:7.6p1-4ubuntu0.3  | bionic-security  | source
 openssh | 1:7.6p1-4ubuntu0.3  | bionic-updates   | source
 openssh | 1:7.6p1-4ubuntu0.4  | bionic-proposed  | source
 openssh | 1:7.9p1-10          | disco            | source
 openssh | 1:8.0p1-6build1     | eoan             | source
 openssh | 1:8.0p1-6ubuntu0.1  | eoan-proposed    | source
 openssh | 1:8.1p1-5           | focal            | source
 openssh | 1:8.2p1-4           | focal-proposed   | source

@CJWatson - are you also doing the openssh SRUs or would you expect us
to handle that?

** Tags added: server-next

** Also affects: openssh (Ubuntu Bionic)
   Importance: Undecided
       Status: New

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

** Changed in: openssh (Ubuntu Bionic)
     Assignee: (unassigned) => Colin Watson (cjwatson)

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https://bugs.launchpad.net/bugs/1863930

Title:
  SSH 1.99 clients fail to connect to openssh-server 1:7.6p1-4ubuntu0.3

Status in openssh package in Ubuntu:
  Fix Released
Status in openssh source package in Bionic:
  New

Bug description:
  SSHD closes the connection and logs the error message below when a
  client presents a protoversion of "1.99":

      Protocol major versions differ for X.X.X.X port X:
  SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 vs. SSH-1.99-XXX

  RFC 4253 only states that clients should treat a server's protoversion
  of "1.99" as equivalent to "2.0"; however, some backward-compatible
  clients send a protoversion of "1.99" and expect the server to treat
  it as "2.0".

  This regression was introduced in openssh-portable 7.6p1 from commit
  97f4d3083; fixes were implemented in commits 9e9c4a7e5 and c9c1bba06.
  I've attached a patch with both of those fixes.

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