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

[Robie Basak]

> would like this avenue to be investigated

To be clear, I mean the general avenue of workarounds in mkvterm, not
necessarily my specific idea.

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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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