[Bug 2056485] Re: Behaviour of socat in Ubuntu 20.04 unexpected

[Robie Basak]

SRU review

Please could you explain why "minor-corrections-in-makefile-and-test-
sh.patch" is required - in particular the change to Makefile.in, but
also the test change? If only parts are required, can the patch be made
more minimal?

> [ Where problems could occur ]

I accept that this is a bug and the fix is correct. However, I'm
concerned about how the proposed change in behaviour might affect users
of 20.04 relying on the current behaviour, even if it is incorrect. If a
user already has scripting relying on this behaviour, it'll break.
Notably, this is being proposed for 20.04 rather than the current LTS.
We're four years from release now; I'd expect few new deployments on
20.04 at this point. Given its age and the existence of a newer LTS,
users also expect behaviour to be more stable with fewer exceptions at
this point in the 20.04 release lifecycle.

Perhaps this is what you meant by "If the changed condition of IF was
done wrong" but it's not clear to me if this risk has been considered in
depth.

For example, can you work around this problem in mkvterm instead, just
for 20.04, so that the impact to users can be fixed without risking
breaking existing users of socat who might be relying on the problem
behaviour? If not, can we arrange for some interaction between mkvterm
and socat to switch behaviour only if specifically requested?

** Changed in: socat (Ubuntu Focal)
       Status: In Progress => Incomplete

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Title:
  Behaviour of socat in Ubuntu 20.04 unexpected

Status in The Ubuntu-power-systems project:
  In Progress
Status in socat package in Ubuntu:
  Fix Released
Status in socat source package in Focal:
  Incomplete

Bug description:
  SRU Justification:

  [ Impact ]

   * IBM Novalink provides a tool called mkvterm.
     Mkvterm takes an lpar id argument and creates a vty-server device on
     device nodes /dev/hvcs*.
     HVCS is a device driver for the IBM Hypervisor Virtual Console Server
     (hvcs). Mkvterm then uses socat to connect.

   * But socat is not behaving as expected.
     When escape=0x1d is passed, you have to hit enter for socat to close
     (expected behavior is Ctrl-] closing the connection).

   * In addition, Ctrl-C closes the connection.
     When using the up and down arrows, junk is printed.
     Password is also visible!

   * This is caused by the fact that under certain circumstances,
     options of the first address are applied to the second address.

  [ Fix ]

   * 5ebf36038f39 5ebf36038f3960798e769bff5646e755a91a1119
     "Under certain circumstances, options of the first address were applied to the second address"

   * 9de26f1d0528 9de26f1d05284257cd9bbb6eb6662089ab7a0680
     "minor corrections, not affecting binaries"

  [ Test Plan ]

   * There was a special test case introduced for this change
     it's test #385.
     If this succeeds, the reported issue is solved.

   * Initially this test case failed, because it required another commit
     on top: 9de26f1d0528
   
   * To verify the overall end-2-end case, the fixes from LP#056373 are required
     as well, but can be taken from the PPA test build that was done there.

   * Then configure a vty-server and try to connect with socat:
     /usr/bin/socat STDIO,raw,echo=0,escape=0x1d /dev/hvcs[minor num]

   * With an unpatched version one will see that the password is
  visible.

   * In addition, the up and down arrows do not work and junk is outputted.
     In addition, Ctrl-] does not close the vterm.

   * Ctrl-C closes the vterm, and it should not.

   * With a patched version the password will not be visible,
     Ctrl+] and Ctrl+C behave as expected.

  [ Where problems could occur ]

   * The code modification is limited to a single line in if
     and is pretty traceable, and it's on top limited to terminos.

   * If the changed condition of IF was done wrong, the expected
     behavior can change (again) and unforeseen things may happen.

   * The rest of the code changes are text in CHANGES and
     a new test case, introduced especially for this bug.

   * Nevertheless, issues can also occur in the (additional)
     test code (which happened and got fixed by adding 9de26f1d0528).

  [ Other Info ]
   
   * Even the code states that this bug is limited to v1.7.3.3.

   * Nevertheless, the code of the socat versions of jammy, mantic
     and noble were checked, and they all have the fix included.
     (However the code in noble's version changed a bit).

   * So only focal is affected.
  __________

  ---Problem Description---
  Novalink provides a tool called mkvterm. Mkvterm takes an lpar id argument and creates a vty-server device on device nodes /dev/hvcs*. HVCS is a device driver for the IBM Hypervisor Virtual Console Server (hvcs). Mkvterm then uses socat to connect.

  Socat is not behaving as expected. When escape=0x1d is passed, you
  have to hit enter for socat to close (expected behavior is Ctrl-]
  closing the connection). In addition, Ctrl-C closes the connection.
  When using the up and down arrows, junk is printed. Password is also
  visible.

  The follow commit fixes the above issues, please add:
  https://repo.or.cz/socat.git/commit/5ebf36038f39

  ---uname output---
  Linux neop91.pok.stglabs.ibm.com 5.4.0-173-generic #191-Ubuntu SMP Fri Feb 2 13:54:35 UTC 2024 ppc64le ppc64le ppc64le GNU/Linux

  ---Steps to Reproduce---
   Fixes to other issues required to reproduce. Mentioned in other bugs.

  Configure a vty-server and try to connect with socat:

  /usr/bin/socat STDIO,raw,echo=0,escape=0x1d /dev/hvcs[minor num]

  Add You will see that the password is visible. In addition, the up and
  down arrows do not work, junk is outputted. In addition, Ctrl-] does
  not close the vterm. Ctrl-C closes the vterm, and it should not.

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