lib-nixio / luci-base: Fix for reading csrf token prevents file upload

The call to http.formvalue in order to read the csrf token causes
_parse_input to be triggered *before* controllers and cbi maps have
been built.  This results in the failure of file uploads because
the file handler is not yet in place when _parse_input gets called,
and it is in _parse_input that POST data is parsed (including files).

To fix this we add the ability to write file fields to temporary
files (using mkstemp and unlink in nixio.file) and use this to
store file data until the filehandler is registered, with a
fallback to reading the file data into memory.

Once the filehandler callback gets registered we iterate
though all previously parsed (saved) files and copy the
data to the file handler, and then close the temporary
file (which finally removes because we unlinked after
creating the file, but didn't close the file so unlink
was deferred).

Signed-off-by: Daniel Dickinson <openwrt@daniel.thecshore.com>

libs/luci-lib-nixio/src/file.c

@@ -79,6 +79,38 @@ static int nixio_open(lua_State *L) {
 	return 1;
 }
 
+static int nixio_mkstemp(lua_State *L) {
+	const char *intemplate = luaL_checklstring(L, 1, NULL);
+	size_t len = lua_strlen(L, 1);
+	char *template = (char *)lua_newuserdata(L, 13 + len);
+	if (!template) {
+		return luaL_error(L, "out of memory");
+	}
+	snprintf(template, 13 + len, "/tmp/%s.XXXXXX", intemplate);
+
+	int fd;
+
+	do {
+		fd = mkstemp(template);
+	} while (fd == -1 && errno == EINTR);
+	if (fd == -1) {
+		return nixio__perror(L);
+	}
+	unlink(template);
+
+	int *udata = lua_newuserdata(L, sizeof(int));
+	if (!udata) {
+		return luaL_error(L, "out of memory");
+	}
+
+	*udata = fd;
+
+	luaL_getmetatable(L, NIXIO_FILE_META);
+	lua_setmetatable(L, -2);
+
+	return 1;
+}
+
 static int nixio_open_flags(lua_State *L) {
 	int mode = 0;
 	const int j = lua_gettop(L);
@@ -366,6 +398,7 @@ static const luaL_reg R[] = {
 	{"dup",			nixio_dup},
 	{"open",		nixio_open},
 	{"open_flags",	nixio_open_flags},
+	{"mkstemp", 		nixio_mkstemp},
 	{"pipe",		nixio_pipe},
 	{NULL,			NULL}
 };

modules/luci-base/luasrc/http.lua

@@ -89,6 +89,37 @@ end
 
 function Request.setfilehandler(self, callback)
 	self.filehandler = callback
+
+	-- If input has already been parsed then any files are either in temporary files
+	-- or are in self.message.params[key]
+	if self.parsed_input then
+		for param, value in pairs(self.message.params) do
+		repeat
+			-- We're only interested in files
+			if (not value["file"]) then break end
+			-- If we were able to write to temporary file
+			if (value["fd"]) then 
+				fd = value["fd"]
+				local eof = false
+				repeat	
+					filedata = fd:read(1024)
+					if (filedata:len() < 1024) then
+						eof = true
+					end
+					callback({ name=value["name"], file=value["file"] }, filedata, eof)
+				until (eof)
+				fd:close()
+				value["fd"] = nil
+			-- We had to read into memory
+			else
+				-- There should only be one numbered value in table - the data
+				for k, v in ipairs(value) do
+					callback({ name=value["name"], file=value["file"] }, v, true)
+				end
+			end
+		until true
+		end
+	end
 end
 
 function Request._parse_input(self)

modules/luci-base/luasrc/http/protocol.lua

@@ -113,6 +113,16 @@ local function __initval( tbl, key )
 	end
 end
 
+-- (Internal function)
+-- Initialize given file parameter.
+local function __initfileval( tbl, key, filename, fd )
+	if tbl[key] == nil then
+		tbl[key] = { file=filename, fd=fd, name=key, "" }
+	else
+		table.insert( tbl[key], "" )
+	end
+end
+
 -- (Internal function)
 -- Append given data to given parameter, either by extending the string value
 -- or by appending it to the last string in the parameter's value table.
@@ -313,6 +323,22 @@ function mimedecode_message_body( src, msg, filecb )
 				__appendval( msg.params, field.name, field.file )
 
 				store = filecb
+			elseif field.name and field.file then
+				local nxf = require "nixio"
+				local fd = nxf.mkstemp(field.name)
+				__initfileval ( msg.params, field.name, field.file, fd )
+				if fd then
+					store = function(hdr, buf, eof)
+						fd:write(buf)
+						if (eof) then
+							fd:seek(0, "set")
+						end
+					end
+				else
+					store = function( hdr, buf, eof )
+						__appendval( msg.params, field.name, buf )
+					end
+				end
 			elseif field.name then
 				__initval( msg.params, field.name )