SSH from bash can freeze the console when non regular characters are outputed.

[MarcMagnin]

Hi!

• Your Windows build number:
  Microsoft Windows [Version 10.0.16299.192]

• What you're doing and what's happening:
  Run an Ubuntu VM (mine is v16) with Golang 1.9.3 installed on it (with Virtualbox for instance).
  SSH from Windows bash onto that VM and run the following golang program:

package main

import (
	"math"
	"fmt"
)

func main() {

	var tt float32 = 1
	for j := 0; j < 5000; j++ {
		bits := uint64(math.Float32bits(tt))
		tt++
		byteCount := 4
		var bb []byte
		bb = make([]byte, 0, byteCount)
		for i := 0; i < byteCount; i++ {
			bb = append(bb, byte(bits&255))
			bits = bits >> 8
		}
		fmt.Print(string(bb))
	}
}

go run <filename>.go

• What's wrong / what should be happening instead:
  It starts outputing some characters and then freeze.
  Characters outputed:

  ?   @  @@  @  @  @  @   A  �A   A  0A  @A  PA  `A  pA  A  A  A  A  A  A  A  A  A  A  A  A  A  A  A  A   B  �B B  B  �B  �B  �B  �B   B  $B  (B  ,
B  0B  4B  8B  <B  @B  DB  HB  LB  PB  TB  XB  \B  `B  dB  hB  lB  pB  tB  xB  |B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B
B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B  B   C  �C  �C  �C  �C  ��
C  C C          C
C  �C  �C  �C  �C  �C  �C  �C  �C  �C  �C  �C  �C  �C     �C  �C  �C  �C   C  !C  "C  #C  $C  %C  &C  'C  (C  )C  *C  +C  ,C  -C  .C  /C  0C  1C  2
3C  4C  5C  6C  7C  8C  9C  :C  ;C  <C  =C  >C  ?C  @C  AC  BC  CC  DC  EC  FC  GC  HC  IC  JC  KC  LC  MC  NC  OC  PC  QC  RC  SC  TC  UC  VC  WC
XC  YC  ZC  [C  \C  ]C  ^C  _C  `C  aC  bC  cC  dC  eC  fC  gC  hC  iC  jC  kC  lC  mC  nC  oC  pC  qC  rC  sC  tC  uC  vC  wC  xC  yC  zC  {C  |C
}C  ~C  �C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C
C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C
C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C
C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C
C C  C C  C C  C C  C C  C C  C C  C C  C C  C C  C C   D @ D  D  D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D ��
D  D @D D D D DDD       D @     D       D       D
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D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�
D �D �D  �D @�D �D �D  �D @�D �D �D    �D @�D �D �D  �D @�D �D �D  �D @�D �D �D  �D @�D �D �D   D @ D  D  D  !D @!D !D !D  "D @"D "D "D  #D @#D #D #
D  $D @$D $D $D  %D @%D %D %D  &D @&D &D &D  'D @'D 'D 'D  (D @(D (D (D  )D @)D )D )D  *D @*D *D *D  +D @+D +D +D  ,D @,D ,D ,D  -D @-D -D -D  .D @.
D .D .D  /D @/D /D /D  0D @0D 0D 0D  1D @1D 1D 1D  2D @2D 2D 2D  3D @3D 3D 3D  4D @4D 4D 4D  5D @5D 5D 5D  6D @6D 6D 6D  7D @7D 7D 7D  8D @8D 8D 8D
9D @9D 9D 9D  :D @:D :D :D  ;D @;D ;D ;D  <D @<D <D <D  =D @=D =D =D  >D @>D >D >D  ?D @?D ?D ?D  @D @@D @D @D  AD @AD AD AD  BD @BD BD BD  CD @CD C
D CD  DD @DD DD DD  ED @ED ED ED  FD @FD FD FD  GD @GD GD GD  HD @HD HD HD  ID @ID ID ID  JD @JD JD JD  KD @KD KD KD  LD @LD LD LD  MD @MD MD MD  N
@ND ND ND  OD @OD OD OD  PD @PD PD PD  QD @QD QD QD  RD @RD RD RD  SD @SD SD SD  TD @TD TD TD  UD @UD UD UD  VD @VD VD VD  WD @WD WD WD  XD @XD XD X
D  YD @YD YD YD  ZD @ZD ZD ZD  [D @[D [D [D  \D @\D \D \D  ]D @]D ]D ]D  ^D @^D ^D ^D  _D @_D _D _D  `D @`D `D `D  aD @aD aD aD  bD @bD bD bD  cD @c
D cD cD  dD @dD dD dD  eD @eD eD eD  fD @fD fD fD  gD @gD gD gD  hD @hD hD hD  iD @iD iD iD  jD @jD jD jD  kD @kD kD kD  lD @lD lD lD  mD @mD mD mD
nD @nD nD nD  oD @oD oD oD  pD @pD pD pD  qD @qD qD qD  rD @rD rD rD  sD @sD sD sD  tD @tD tD tD  uD @uD uD uD  vD @vD vD vD  wD @wD wD wD  xD @xD x
D xD  yD @yD yD yD  zD @zD zD zD  {D @{D {D {D  |D @|D |D |D  }D @}D }D }D  ~D @~D ~D ~D  �D @�D �D

This works perfectly fine on powershell (running the program from Windows) or within the Ubuntu native terminal (from Virtualbox interface).

Regards

[zadjii-msft]

Does this work if you take SSH out of the equation?

What happens when you run the above go script directly in WSL?

If this works in powershell (running Go on Windows), but not in bash (running Go on WSL), then I'd be inclined to believe this is a WSL bug, not a console issue.

[MarcMagnin]

Yes this works fine everywhere without SSH.

[miniksa]

This has been a long time, so we should probably try to re-repro this.

[SvenBrunk]

I might be facing the same issue. For me the Windows Terminal freezes when I type "ls -l" on a RHEL server that outputs links as "->".
At least that is my working theory. I first thought it might be an SSH bug related to certain ACLs, but with kitty (putty clone) I can view the directories just fine.
Might of course also be the colors:

or one of these permission issues:
lsattr: Permission denied While reading flags on ./config.inc.php
lsattr: Operation not supported While reading flags on ./export

[zadjii-msft]

I'm honestly kind of shocked that this 3 year old issue is still open without any traction. If this was more widespread, I'm sure we would have seen more hits...

@SvenBrunk What Terminal version are you using, what ssh are you using? Could you get a debug tap trace of the terminal when it freezes? That could help ID the string of text that triggers this.

[miniksa]

You could also attempt to tee the output to a file and attach it so we can reproduce it hopefully at-will with a cat.

I also wonder if #10653 will help this. Perhaps its the display that's freezing up and @lhecker's ticket lock will help.

[SvenBrunk]

I am using
Windows Terminal
Version: 1.8.1521.0

SSH: OpenSSH_8.2p1 Ubuntu-4ubuntu0.2, OpenSSL 1.1.1f 31 Mar 2020

Unfortunately when I tried today from the office it didn't happen. I will try again when I am in Homeoffice today. Maybe there is an issue in conjunction to the VPN connection. 🤔
Which would also explain that not many people face that issue.
(Well... or someone messed up the server configuration and now cleaned it up silently)

[zadjii-msft]

tbh, given the way OP responded

Yes this works fine everywhere without SSH.

then this should have probably been moved to https://github.com/PowerShell/Win32-OpenSSH/ a long time ago 😕

[SvenBrunk]

It IS connected to the VPN-connection. In Homeoffice the connection stalls.
Unfortunately the output in the debug tap is completely none:
$␛[1Cllss␣␣--llaa␍␍␊␍
(I pressed return again... )

[DHowett]

As a test... when the connection stalls, can you press Enter ~ .? What happens?

[ghost]

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 4 days. It will be closed if no further activity occurs within 3 days of this comment.