+local forbidden_chars_pattern = "[/%z]";
+if prosody.platform == "windows" then
+ forbidden_chars_pattern = "[/%z\001-\031\127\"*:<>?|]"
+end
+
+local urldecode = require "util.http".urldecode;
+function sanitize_path(path)
+ local out = {};
+
+ local c = 0;
+ for component in path:gmatch("([^/]+)") do
+ component = urldecode(component);
+ if component:find(forbidden_chars_pattern) then
+ return nil;
+ elseif component == ".." then
+ if c <= 0 then
+ return nil;
+ end
+ out[c] = nil;
+ c = c - 1;
+ elseif component ~= "." then
+ c = c + 1;
+ out[c] = component;
+ end
+ end
+ return "/"..table.concat(out, "/");
+end
+