The test failed with
> Test "test5 user should not be able to run commands under root" failed with
> error: "invalid literal for int() with base 10: ''"
since 2492da88ea.
The reason for this is that `sudo(8)` writes the lecture to the
tty[1] and only as a fallback to stdout[2]. This means that the
`base64 --wrap 0` executed by `machine.execute()` doesn't affect the
text written to the terminal, however the lecture is part of the string
that's read from the VM via `shell.recv()`.
I confirmed the problem in an interactive test session[3]:
>>> command = "sudo -u test5 sudo -n -u root true"
>>> out_command = f"( set -euo pipefail; {command} ) | (base64 --wrap 0; echo)\n"
>>> machine.shell.send(out_command.encode())
84
>>> machine # [ 99.015512] sudo[877]: root : TTY=hvc0 ; PWD=/tmp ; USER=test5 ; COMMAND=/run/wrappers/bin/sudo -n -u root true
machine # [ 99.019373] sudo[877]: pam_unix(sudo:session): session opened for user test5(uid=1005) by (uid=0)
machine # [ 99.038692] sudo[879]: pam_unix(sudo:auth): conversation failed
machine # sudo: a password is required
machine # [ 99.041860] sudo[879]: pam_unix(sudo:auth): auth could not identify password for [test5]
machine # [ 99.046901] sudo[877]: pam_unix(sudo:session): session closed for user test5
>>>
>>> x=machine._next_newline_closed_block_from_shell()
>>> print(x)
<newline>
We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:
<newline>
#1) Respect the privacy of others.
#2) Think before you type.
#3) With great power comes great responsibility.
<newline>
<newline>
<newline>
>>>
Since the lecture isn't strictly necessary to confirm that
`security.sudo` works as expected, I decided to disable lecturing
inside the test, however we may want to fix the underlying problem in
the test-driver at some point.
[1] https://github.com/sudo-project/sudo/blob/SUDO_1_9_9/plugins/sudoers/check.c#L275-L283
[2] https://github.com/sudo-project/sudo/blob/SUDO_1_9_9/src/conversation.c#L95-L120
[3] I replaced each empty line with `<newline>` to make sure these
aren't swallowed by git.
One of the subtests in the sudo NixOS test suite was broken: instead of
running the sudo invocation as user 'test2', it was running it as root.
Since root doesn't require a password to use sudo, this was causing
random "broken pipe" errors when trying to pass it a password via stdin.
