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base-files: functions.sh: fix config_get() on invalid identifiers

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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 <jo@mein.io>
This commit is contained in:
Jo-Philipp Wich
2020-08-05 09:07:00 +02:00
parent 0c109df7f0
commit 4a6795409d
2 changed files with 9 additions and 4 deletions
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2
package/base-files/Makefile
View File

@@ -12,7 +12,7 @@ include $(INCLUDE_DIR)/version.mk
include $(INCLUDE_DIR)/feeds.mk
PKG_NAME:=base-files
PKG_RELEASE:=225
PKG_RELEASE:=226
PKG_FLAGS:=nonshared
PKG_FILE_DEPENDS:=$(PLATFORM_DIR)/ $(GENERIC_PLATFORM_DIR)/base-files/

5
package/base-files/files/lib/functions.sh
View File

@@ -107,10 +107,15 @@ config_unset() {
# config_get <variable> <section> <option> [<default>]
# config_get <section> <option>
config_get() {
case "$2${3:-$1}" in
*[^A-Za-z0-9_]*) : ;;
*)
case "$3" in
"") eval echo "\"\${CONFIG_${1}_${2}:-\${4}}\"";;
*) eval export ${NO_EXPORT:+-n} -- "${1}=\${CONFIG_${2}_${3}:-\${4}}";;
esac
;;
esac
}
# config_get_bool <variable> <section> <option> [<default>]