dracut-lib.sh: quote variables in parameter expansion patterns

[diabonas]

According to POSIX.1-2017, 2.6.2 Parameter Expansion:

${parameter%[word]}
[...] The word shall be expanded to produce a pattern.

This means if word contains variables that itself contain special characters like asterisks or backslashes, these are treated as pattern characters unless the variable is quoted. Try e.g. the following example in bash, dash or (busybox) ash:

i='a\c'; j='\'; echo "${i%$j*}"

This prints a\c because $j* is expanded to \*, escaping the asterisk. In contrast,

i='a\c'; j='\'; echo "${i%"$j"*}"

produces the expected result a because the backslash is not specially treated any more after quoting.

The quotes that this commit adds have been previously removed in commit f9c96cf, citing issues with busybox hush without further specifying the actual error. I tested a recent busybox build (upstream commit 9aa751b08ab03d6396f86c3df77937a19687981b) and couldn't find any problems. Note that the above example always produces a\c in hush regardless of quoting $j, making hush unsuitable
for use with dracut, but using quotes in parameter expansions generally works.

The unquoted variables break the "rd.luks.uuid/name" kernel command line options in dracut 050 because

dracut/modules.d/90crypt/parse-crypt.sh

Line 68 in 25c7a13

luksname="$(str_replace "$luksname" '\' '\\')"

is not able to escape the backslashes any more, see #723, #727: backslashes in the systemd-cryptsetup@.service unit name stay unescaped for use in udev (cf. commit 0f6d93e), leading to failures in starting the unit.

This partially reverts commit f9c96cf.

[centos-ci]

Can one of the admins verify this patch?

[haraldh]

Thank you!