base-files: functions.sh: fix config_get() on invalid identifiers
When passing a section or option value to config_get() which contains
characters that happen to be valid variable interpolation expressions,
the function returns a nonsensical expression result instead of the
expected empty string.
When the passed section or option name contains other characters which
are not valid within a shell variable name, a substitution error is
occuring instead.
The issue can be easily reproduced by one of the following examples:
root@OpenWrt:~# . /lib/functions.sh
root@OpenWrt:~# config load system
root@OpenWrt:~# config_get variable invalid-section option
root@OpenWrt:~# echo "$variable"
section_option:-
root@OpenWrt:~# . /lib/functions.sh
root@OpenWrt:~# config load system
root@OpenWrt:~# config_get variable section invalid-option
root@OpenWrt:~# echo "$variable"
option:-
root@OpenWrt:~# . /lib/functions.sh
root@OpenWrt:~# config load system
root@OpenWrt:~# config_get variable section invalid@option
-ash: eval: syntax error: bad substitution
Fix this issue by only performing interpolations when the given section
and option arguments are free of illegal characters.
Signed-off-by: Jo-Philipp Wich <[email protected]>
Jo-Philipp Wich