luci-base: introduce luci.util.shellquote()

Introduce a new function luci.util.shellquote() which encloses the given
string argument in single quotes and escapes any embedded single quote
characters.

This function is intended to be used when interpolating untrusted input
into shell commands.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

diff --git a/modules/luci-base/luasrc/util.lua b/modules/luci-base/luasrc/util.lua
index 28c1266..06a889c 100644 (file)
--- a/modules/luci-base/luasrc/util.lua
+++ b/modules/luci-base/luasrc/util.lua
@@ -164,6 +164,10 @@ function striptags(value)
        return value and tparser.striptags(tostring(value))
 end
 
+function shellquote(value)
+       return string.format("'%s'", string.gsub(value or "", "'", "'\\''"))
+end
+
 -- for bash, ash and similar shells single-quoted strings are taken
 -- literally except for single quotes (which terminate the string)
 -- (and the exception noted below for dash (-) at the start of a
@@ -656,7 +660,7 @@ function checklib(fullpathexe, wantedlib)
        if not haveldd or not haveexe then
                return false
        end
-       local libs = exec("/usr/bin/ldd " .. fullpathexe)
+       local libs = exec(string.format("/usr/bin/ldd %s", shellquote(fullpathexe)))
        if not libs then
                return false
        end

diff --git a/modules/luci-base/luasrc/util.luadoc b/modules/luci-base/luasrc/util.luadoc
index 949aeb2..79a17a2 100644 (file)
--- a/modules/luci-base/luasrc/util.luadoc
+++ b/modules/luci-base/luasrc/util.luadoc
@@ -83,6 +83,15 @@ Strip HTML tags from given string.
 ]]
 
 ---[[
+Safely quote value for use in shell commands.
+
+@class function
+@name shellquote
+@param value  String containing the value to quote
+@return Single-quote enclosed string with embedded quotes escaped
+]]
+
+---[[
 Splits given string on a defined separator sequence and return a table
 
 containing the resulting substrings. The optional max parameter specifies