bash does not fulfill --rcfile option properly

[Hugo Heden]

I am starting a bash shell using

$ bash --noprofile --rcfile my-custom-bash-rc-file

Due to the --rcflag, the newly started bash should *not* execute commands from /etc/bash.bashrc. That is at least how I interpret `man bash`:

      --rcfile file
              Execute commands from file instead of the system wide initialization file /etc/bash.bashrc and the standard personal initial‐
              ization file ~/.bashrc if the shell is interactive (see INVOCATION below).

However, it seems that the commands in /etc/bash.bashrc are in fact executed.

To see/reproduce/diagnose this, on Ubuntu I believe one can just invoke bash like this (as the regular user):

$ touch testrc
$ env -i bash --noprofile --rcfile testrc

The expected result would be that nothing special is printed on the terminal. However, there is an error message, which is printed from /etc/bash.bashrc. The "env -i" causes $HOME to not be set in the invoked shell, which in turn triggers the error. The error message is:

> To run a command as administrator (user "root"), use "sudo <command>".
> See "man sudo_root" for details.

Another way to see this -- without the "env -i" -- is to add a command to /etc/bash.bashrc, such as

echo HELLO THERE

To trigger the bug(?), one can then just do

$ touch testrc
$ bash --noprofile --rcfile testrc

The expected result would be that nothing special is shown in the terminal. However, it turns out that the string

HELLO THERE

is printed.

[Hugo Heden (hugoheden)]

$ lsb_release --all
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal

$ bash --version
GNU bash, version 4.2.37(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dave Jones (waveform)]

This has apparently been an issue for some considerable time. I've just now run into it while delving into a failure in pexpect's test-suite (during work on LP: #1987420), which apparently assumes that using --rcfile will suppress both the user *and* the system's bashrc (as the man-page documents).

However, I'm not entirely convinced this is a bug in bash, so much as its man-page. Reading the original code (shell.c in bash) its intent is fairly clear: execute the system-wide bashrc in all interactive shells, but permit the user's bashrc to be overridden by --rcfile.

It's worth noting that the original (upstream, not Debian) man-page makes no mention of the system-wide bashrc because it's an option that's not activated by default. The Debian packaging enables the system-wide bashrc (SYS_BASHRC in d/p/deb-bash-config.diff) and then patches the man-page to mention it (d/p/man-bashrc.diff). In other words, I suspect this is a documentation bug rather than a behavioural bug (i.e. the man-page is wrong, not the behaviour).

[Dave Jones (waveform)]

Hmm, on the other hand --norc does indeed suppress both user and system-wide bashrc files. So, the man-page is correct in that instance, and apparently the intent of bash is to allow the system-wide bashrc file to be suppressed in certain circumstances. Which sways me back toward the notion that the bug is in bash's --rcfile behaviour ...

[Dave Jones (waveform)]

I'm unsure what the "correct" solution is here; could be that bash's behaviour is wrong, or it could be that the documentation is wrong. Rather than decide, I'm taking the cowards way out and attaching patches for both solutions, leaving it to the maintainer to decide which is appropriate :)

[Julian Andres Klode (juliank)]

This discussion needs to be taken upstream, it's not our place to decide what is right.

[Dave Jones (waveform)]

It appears this has come up before, and was discussed upstream. [1] and [2] cover discussion of whether --rcfile should ignore the system-wide bashrc, with the conclusion from upstream that it should not. [3] is an attempt by someone to fix this upstream by modifying bash's behaviour, which is rejected by the upstream developers. [4] and [5] are the upstream Debian bugs (which I'll link this bug to).

At any rate, upstream bash devs have made their position quite clear: the Debian-patched documentation is wrong, and the behaviour of bash is as expected. So, the solution to this bug is to fix the documentation. I'll propose an updated patch here and see if we can't put this decade-old bug to bed!

I'll also try and rebase the noble patch upstream for Debian (there's already a patch there, but it's predictably ancient).

[1]: https://lists.gnu.org/archive/html/bug-bash/2018-01/msg00003.html

[2]: https://lists.gnu.org/archive/html/bug-bash/2009-05/msg00031.html

[3]: https://savannah.gnu.org/support/index.php?107950

[4]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=516152

[5]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=343673

[Paride Legovini (paride)]

Thanks for digging into this issue and updating the relevant Debian bug, refreshing the debdiff. This LGTM, tested locally, the manpage renders fine. I am going to sponsor this.

[Paride Legovini (paride)]

Actually, it would be nice if the new patch had some dep-3 headers (see [1], `quilt --dep3` and maybe dep3changelog). In particular I think we miss bug references an a description of the patch. Do you think you could add the relevant ones? Thanks!

[1] https://dep-team.pages.debian.net/deps/dep3/

[Dave Jones (waveform)]

Doh, I always forget something...

[Dan Bungert (dbungert)]

Uploaded

[Dave Jones (waveform)]

Bah, looks like this upload got accidentally dropped by the subsequent merge for noble. I'll rebase and re-proposed it when I've got some time...

[Dave Jones (waveform)]

Attaching new debdiff based on the current noble version.