80-systemd-osc-context.sh leads to unexpected output

[Ray-1989]

systemd version the issue has been seen with

258-4

Used distribution

ArchLinux

Linux kernel version used

6.16.8-arch3-1

CPU architectures issue was seen on

x86_64

Component

systemd

Expected behaviour you didn't see

This is a VM Guest in PVE(Proxmox Virtual Environment) 8.4. The following is the correct output before upgrade systemd from 257.7-1.

[root@archlinux ~]# echo $PROMPT_COMMAND
printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/\~}"
[root@archlinux ~]# echo $PS0

[root@archlinux ~]# pacman -Qn systemd
systemd 257.7-1
[root@archlinux ~]# 

Unexpected behaviour you saw

The following is the unexpected output after upgrade systemd to 258-4.

03;start=44681544-a0ea-4ea1-85c8-1d9190d5a789;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=shell;cwd=/root[root@archlinux ~]# pwd
03;start=a28f7daa-8fff-4727-be98-71d854464e95;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=command;cwd=/root/root
03;end=a28f7daa-8fff-4727-be98-71d854464e95;exit=success03;start=44681544-a0ea-4ea1-85c8-1d9190d5a789;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=shell;cwd=/root[root@archlinux ~]# echo $PROMPT_COMMAND
03;start=a51a0aca-4eb9-408e-8767-f3900b7b2b03;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=command;cwd=/root__systemd_osc_context_precmdline
03;end=a51a0aca-4eb9-408e-8767-f3900b7b2b03;exit=success03;start=44681544-a0ea-4ea1-85c8-1d9190d5a789;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=shell;cwd=/root[root@archlinux ~]# echo $PS0
03;start=86b3cceb-54b0-4dec-b96b-0ff11b365c4b;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=command;cwd=/root\033]8003;start=$systemd_osc_context_cmd_id$(__systemd_osc_context_common);type=command;cwd=$(__systemd_osc_context_escape "$PWD")\033\\
03;end=86b3cceb-54b0-4dec-b96b-0ff11b365c4b;exit=success03;start=44681544-a0ea-4ea1-85c8-1d9190d5a789;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=shell;cwd=/root[root@archlinux ~]# 

I need to unset PROMPT_COMMAND and PS0 to bring it back to normal.

03;end=86b3cceb-54b0-4dec-b96b-0ff11b365c4b;exit=success03;start=44681544-a0ea-4ea1-85c8-1d9190d5a789;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=shell;cwd=/root[root@archlinux ~]# unset PROMPT_COMMAND
03;start=35429af8-8d4d-43f2-90de-c32ea9389fc0;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=command;cwd=/root[root@archlinux ~]# unset PS0
03;start=35429af8-8d4d-43f2-90de-c32ea9389fc0;user=root;hostname=archlinux;machineid=a283760a983749dbb26173669285ae5c;bootid=6df8736c-7230-4081-8028-2c0ef71001c8;pid=768;type=command;cwd=/root[root@archlinux ~]# 
[root@archlinux ~]# 
[root@archlinux ~]# pwd
/root
[root@archlinux ~]# pacman -Qn systemd
systemd 258-4
[root@archlinux ~]#

Steps to reproduce the problem

Upgrade systemd from 257.7-1 to 258-4.

Additional program output to the terminal or log subsystem illustrating the issue

The PROMPT_COMMAND and PS0 is set by /etc/profile.d/80-systemd-osc-context.sh in /etc/profile.


[root@archlinux ~]# pacman -Qo /etc/profile.d/80-systemd-osc-context.sh
/etc/profile.d/80-systemd-osc-context.sh is owned by systemd 258-4
[root@archlinux ~]#

[poettering]

interestin. which terminal emulator do you use?

[Ray-1989]

Terminal emulator software is SecureCRT 9.6.3.

Env TERM is xterm-256color.

[root@archlinux ~]# echo $TERM
xterm-256color
[root@archlinux ~]# 

Session config snapshot:

[Ray-1989]

I am using another ssh terminal emulator software putty, and it works fine.

login as: root
root@172.16.24.21's password:
[root@archlinux ~]# echo $PROMPT_COMMAND
__systemd_osc_context_precmdline
[root@archlinux ~]# echo $PS0
\033]8003;start=$systemd_osc_context_cmd_id$(__systemd_osc_context_common);type=command;cwd=$(__systemd_osc_context_escape "$PWD")\033\\
[root@archlinux ~]# pwd
/root
[root@archlinux ~]#

[Ray-1989]

I compared the value of PROMPT_COMMAND and PS0 when using SecureCRT and putty, and it is the same.

I didnot change SecureCRT session config of this VM Guest, and it becomes abnormal after upgrade. I want to find out the root cause. Can you help give some advice ?

[Ray-1989]

It works fine via Xshell.
It seems like something error with SecureCRT.

[jackyjkchen]

I remove this file after upgrading...

[filbo]

I'm having the same issue on a Debian 'sid' host, connecting in with (a rather old version of) mate-terminal from another host.

The escape sequences being emitted by the function __systemd_osc_context_precmdline() and related functions are highly terminal-specific, not at all appropriate for generic command prompt generation.

People who aren't seeing an issue have a terminal emulator which silently consumes these sequences. The 'problem' terminal emulators are not at fault, they're being sent inappropriate sequences.

[filbo]

Whoever works on this: the function __systemd_osc_context_escape() uses sed(1) to replace characters \ and ; with hex equivalents.

This code is executed only under bash(1). bash has pattern substitution:

foo="abc;def;ghi\jkl\mno"
foo_backslash="${foo//\\/\\x5c}"
foo_backslash_semi="${foo_backslash//;/\\x3b}"

It can't apply two such substitutions in a single assignment, but that's OK, just do two. This is still vastly more efficient than shelling out to a subprogram.

NOTE: the current code converts \ to \x5x, which isn't the right hex value. It says 'according to OSC 8003 spec' -- perhaps that says to emit \x5x, but I doubt it. I didn't try to find this spec, though.

[Ray-1989]

It works fine via Xshell. It seems like something error with SecureCRT.

I just created a brand new Windows 11 VM (testwin), installed SecureCRT 9.6.4.3695(the latest version) in testwin, and used the default configuration of SecureCRT to connect to the upgraded linux(another linux exposed the network which upgraded systemd too). The issue can be reproduced. Here is the snapshot.

[Ray-1989]

Whoever works on this: the function __systemd_osc_context_escape() uses sed(1) to replace characters \ and ; with hex equivalents.

This code is executed only under bash(1). bash has pattern substitution:

foo="abc;def;ghi\jkl\mno"
foo_backslash="${foo//\\/\\x5c}"
foo_backslash_semi="${foo_backslash//;/\\x3b}"

It can't apply two such substitutions in a single assignment, but that's OK, just do two. This is still vastly more efficient than shelling out to a subprogram.

NOTE: the current code converts \ to \x5x, which isn't the right hex value. It says 'according to OSC 8003 spec' -- perhaps that says to emit \x5x, but I doubt it. I didn't try to find this spec, though.

You've conducted a very thorough investigation. Thank you for sharing.

[Ray-1989]

Maybe using OSC 133 spec to customize PROMPT is better.

[poettering]

This is an issue with SecureCRT. It doesn't know how to handle unknown OSC sequences: ignore them. Pretty much every other terminal emulator gets this right, SecureCRT doesn't. Consider using a different emulator until that is fixed, or simple remove /etc/profile.d/80-systemd-osc-context.sh on your system.

Duplicate of #39114