This reverts commit b45c068dd8.
I think the idea was generally sound, but didn't take into account the
limitations of show-environment and how it is used. People expect to be able to
eval systemctl show-environment output in bash, and no escaping syntax is
defined for environment *names* (we only do escaping for *values*). We could
skip such problematic variables in 'systemctl show-environment', and only allow
them to be inherited directly. But this would be confusing and ugly.
The original motivation for this change was that various import operations
would fail. a4ccce22d9 changed systemctl to filter
invalid variables in import-environment.
https://gitlab.gnome.org/GNOME/gnome-session/-/issues/71 does a similar change
in GNOME. So those problematic variables should not cause failures, but just
be silently ignored.
Finally, the environment block is becoming a dumping ground. In my gnome
session 'systemctl show-environment --user' includes stuff like PWD, FPATH
(from zsh), SHLVL=0 (no idea what that is). This is not directly related to
variable names (since all those are allowed under the stricter rules too), but
I think we should start pushing people away from running import-environment and
towards importing only select variables.
https://github.com/systemd/systemd/pull/17188#issuecomment-708676511
There was some confusion about what POSIX says about variable names:
names shall not contain the character '='. For values to be portable
across systems conforming to POSIX.1-2008, the value shall be composed
of characters from the portable character set (except NUL and as
indicated below).
i.e. it allows almost all ASCII in variable names (without NUL and DEL and
'='). OTOH, it says that *utilities* use a smaller set of characters:
Environment variable names used by the utilities in the Shell and
Utilities volume of POSIX.1-2008 consist solely of uppercase letters,
digits, and the <underscore> ( '_' ) from the characters defined in
Portable Character Set and do not begin with a digit.
When enforcing variable names in environment blocks, we need to use this
first definition, so that we can propagate all valid variables.
I think having non-printable characters in variable names is too much, so
I took out the whitespace stuff from the first definition.
OTOH, when we use *shell syntax*, for example doing variable expansion,
it seems enough to support expansion of variables that the shell would allow.
Fixes#14878,
https://bugzilla.redhat.com/show_bug.cgi?id=1754395,
https://bugzilla.redhat.com/show_bug.cgi?id=1879216.
We had a special test case that the second semicolon would be interpreted
as an executable name. We would then try to find the executable and rely
on ";" not being found to cause ENOEXEC to be returned. I think that's just
crazy. Let's treat the second semicolon as a separator and ignore the
whole thing as we would whitespace.
The conf-parser machinery already removed whitespace before and after "=", no
need to repeat this step.
The test is adjusted to pass. It was testing an code path that doesn't happen
normally, no point in doing that.
This file was testing a mix of functions from src/core/load-fragment.c and some
from src/shared/install.c. Let's name it more appropriately. I want to add
tests for the new unit-file.c too.
