libs: merge libs/http into libs/web

4 files changed, 1057 insertions, 0 deletions

diff --git a/libs/web/luasrc/http/protocol.lua b/libs/web/luasrc/http/protocol.lua
new file mode 100644
index 000000000..d8ef09f7a
--- /dev/null
+++ b/libs/web/luasrc/http/protocol.lua
@@ -0,0 +1,690 @@
+--[[
+
+HTTP protocol implementation for LuCI
+(c) 2008 Freifunk Leipzig / Jo-Philipp Wich <xm@leipzig.freifunk.net>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+$Id$
+
+]]--
+
+--- LuCI http protocol class.
+-- This class contains several functions useful for http message- and content
+-- decoding and to retrive form data from raw http messages.
+module("luci.http.protocol", package.seeall)
+
+local ltn12 = require("luci.ltn12")
+
+HTTP_MAX_CONTENT      = 1024*8		-- 8 kB maximum content size
+
+--- Decode an urlencoded string - optionally without decoding
+-- the "+" sign to " " - and return the decoded string.
+-- @param str		Input string in x-www-urlencoded format
+-- @param no_plus	Don't decode "+" signs to spaces
+-- @return			The decoded string
+-- @see				urlencode
+function urldecode( str, no_plus )
+
+	local function __chrdec( hex )
+		return string.char( tonumber( hex, 16 ) )
+	end
+
+	if type(str) == "string" then
+		if not no_plus then
+			str = str:gsub( "+", " " )
+		end
+
+		str = str:gsub( "%%([a-fA-F0-9][a-fA-F0-9])", __chrdec )
+	end
+
+	return str
+end
+
+--- Extract and split urlencoded data pairs, separated bei either "&" or ";"
+-- from given url or string. Returns a table with urldecoded values.
+-- Simple parameters are stored as string values associated with the parameter
+-- name within the table. Parameters with multiple values are stored as array
+-- containing the corresponding values.
+-- @param url	The url or string which contains x-www-urlencoded form data
+-- @param tbl	Use the given table for storing values (optional)
+-- @return		Table containing the urldecoded parameters
+-- @see			urlencode_params
+function urldecode_params( url, tbl )
+
+	local params = tbl or { }
+
+	if url:find("?") then
+		url = url:gsub( "^.+%?([^?]+)", "%1" )
+	end
+
+	for pair in url:gmatch( "[^&;]+" ) do
+
+		-- find key and value
+		local key = urldecode( pair:match("^([^=]+)")     )
+		local val = urldecode( pair:match("^[^=]+=(.+)$") )
+
+		-- store
+		if type(key) == "string" and key:len() > 0 then
+			if type(val) ~= "string" then val = "" end
+
+			if not params[key] then
+				params[key] = val
+			elseif type(params[key]) ~= "table" then
+				params[key] = { params[key], val }
+			else
+				table.insert( params[key], val )
+			end
+		end
+	end
+
+	return params
+end
+
+--- Encode given string to x-www-urlencoded format.
+-- @param str	String to encode
+-- @return		String containing the encoded data
+-- @see			urldecode
+function urlencode( str )
+
+	local function __chrenc( chr )
+		return string.format(
+			"%%%02x", string.byte( chr )
+		)
+	end
+
+	if type(str) == "string" then
+		str = str:gsub(
+			"([^a-zA-Z0-9$_%-%.%+!*'(),])",
+			__chrenc
+		)
+	end
+
+	return str
+end
+
+--- Encode each key-value-pair in given table to x-www-urlencoded format,
+-- separated by "&". Tables are encoded as parameters with multiple values by
+-- repeating the parameter name with each value.
+-- @param tbl	Table with the values
+-- @return		String containing encoded values
+-- @see			urldecode_params
+function urlencode_params( tbl )
+	local enc = ""
+
+	for k, v in pairs(tbl) do
+		if type(v) == "table" then
+			for i, v2 in ipairs(v) do
+				enc = enc .. ( #enc > 0 and "&" or "" ) ..
+					urlencode(k) .. "=" .. urlencode(v2)
+			end
+		else
+			enc = enc .. ( #enc > 0 and "&" or "" ) ..
+				urlencode(k) .. "=" .. urlencode(v)
+		end
+	end
+
+	return enc
+end
+
+-- (Internal function)
+-- Initialize given parameter and coerce string into table when the parameter
+-- already exists.
+-- @param tbl	Table where parameter should be created
+-- @param key	Parameter name
+-- @return		Always nil
+local function __initval( tbl, key )
+	if tbl[key] == nil then
+		tbl[key] = ""
+	elseif type(tbl[key]) == "string" then
+		tbl[key] = { tbl[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.
+-- @param tbl	Table containing the previously initialized parameter value
+-- @param key	Parameter name
+-- @param chunk	String containing the data to append
+-- @return		Always nil
+-- @see			__initval
+local function __appendval( tbl, key, chunk )
+	if type(tbl[key]) == "table" then
+		tbl[key][#tbl[key]] = tbl[key][#tbl[key]] .. chunk
+	else
+		tbl[key] = tbl[key] .. chunk
+	end
+end
+
+-- (Internal function)
+-- Finish the value of given parameter, either by transforming the string value
+-- or - in the case of multi value parameters - the last element in the
+-- associated values table.
+-- @param tbl		Table containing the previously initialized parameter value
+-- @param key		Parameter name
+-- @param handler	Function which transforms the parameter value
+-- @return			Always nil
+-- @see				__initval
+-- @see				__appendval
+local function __finishval( tbl, key, handler )
+	if handler then
+		if type(tbl[key]) == "table" then
+			tbl[key][#tbl[key]] = handler( tbl[key][#tbl[key]] )
+		else
+			tbl[key] = handler( tbl[key] )
+		end
+	end
+end
+
+
+-- Table of our process states
+local process_states = { }
+
+-- Extract "magic", the first line of a http message.
+-- Extracts the message type ("get", "post" or "response"), the requested uri
+-- or the status code if the line descripes a http response.
+process_states['magic'] = function( msg, chunk, err )
+
+	if chunk ~= nil then
+		-- ignore empty lines before request
+		if #chunk == 0 then
+			return true, nil
+		end
+
+		-- Is it a request?
+		local method, uri, http_ver = chunk:match("^([A-Z]+) ([^ ]+) HTTP/([01]%.[019])$")
+
+		-- Yup, it is
+		if method then
+
+			msg.type           = "request"
+			msg.request_method = method:lower()
+			msg.request_uri    = uri
+			msg.http_version   = tonumber( http_ver )
+			msg.headers        = { }
+
+			-- We're done, next state is header parsing
+			return true, function( chunk )
+				return process_states['headers']( msg, chunk )
+			end
+
+		-- Is it a response?
+		else
+
+			local http_ver, code, message = chunk:match("^HTTP/([01]%.[019]) ([0-9]+) ([^\r\n]+)$")
+
+			-- Is a response
+			if code then
+
+				msg.type           = "response"
+				msg.status_code    = code
+				msg.status_message = message
+				msg.http_version   = tonumber( http_ver )
+				msg.headers        = { }
+
+				-- We're done, next state is header parsing
+				return true, function( chunk )
+					return process_states['headers']( msg, chunk )
+				end
+			end
+		end
+	end
+
+	-- Can't handle it
+	return nil, "Invalid HTTP message magic"
+end
+
+
+-- Extract headers from given string.
+process_states['headers'] = function( msg, chunk )
+
+	if chunk ~= nil then
+
+		-- Look for a valid header format
+		local hdr, val = chunk:match( "^([A-Za-z][A-Za-z0-9%-_]+): +(.+)$" )
+
+		if type(hdr) == "string" and hdr:len() > 0 and
+		   type(val) == "string" and val:len() > 0
+		then
+			msg.headers[hdr] = val
+
+			-- Valid header line, proceed
+			return true, nil
+
+		elseif #chunk == 0 then
+			-- Empty line, we won't accept data anymore
+			return false, nil
+		else
+			-- Junk data
+			return nil, "Invalid HTTP header received"
+		end
+	else
+		return nil, "Unexpected EOF"
+	end
+end
+
+
+--- Creates a ltn12 source from the given socket. The source will return it's
+-- data line by line with the trailing \r\n stripped of.
+-- @param sock	Readable network socket
+-- @return		Ltn12 source function
+function header_source( sock )
+	return ltn12.source.simplify( function()
+
+		local chunk, err, part = sock:receive("*l")
+
+		-- Line too long
+		if chunk == nil then
+			if err ~= "timeout" then
+				return nil, part
+					and "Line exceeds maximum allowed length"
+					or  "Unexpected EOF"
+			else
+				return nil, err
+			end
+
+		-- Line ok
+		elseif chunk ~= nil then
+
+			-- Strip trailing CR
+			chunk = chunk:gsub("\r$","")
+
+			return chunk, nil
+		end
+	end )
+end
+
+--- Decode a mime encoded http message body with multipart/form-data
+-- Content-Type. Stores all extracted data associated with its parameter name
+-- in the params table withing the given message object. Multiple parameter
+-- values are stored as tables, ordinary ones as strings.
+-- If an optional file callback function is given then it is feeded with the
+-- file contents chunk by chunk and only the extracted file name is stored
+-- within the params table. The callback function will be called subsequently
+-- with three arguments:
+--  o Table containing decoded (name, file) and raw (headers) mime header data
+--  o String value containing a chunk of the file data
+--  o Boolean which indicates wheather the current chunk is the last one (eof)
+-- @param src		Ltn12 source function
+-- @param msg		HTTP message object
+-- @param filecb	File callback function (optional)
+-- @return			Value indicating successful operation (not nil means "ok")
+-- @return			String containing the error if unsuccessful
+-- @see				parse_message_header
+function mimedecode_message_body( src, msg, filecb )
+
+	if msg and msg.env.CONTENT_TYPE then
+		msg.mime_boundary = msg.env.CONTENT_TYPE:match("^multipart/form%-data; boundary=(.+)$")
+	end
+
+	if not msg.mime_boundary then
+		return nil, "Invalid Content-Type found"
+	end
+
+
+	local tlen   = 0
+	local inhdr  = false
+	local field  = nil
+	local store  = nil
+	local lchunk = nil
+
+	local function parse_headers( chunk, field )
+
+		local stat
+		repeat
+			chunk, stat = chunk:gsub(
+				"^([A-Z][A-Za-z0-9%-_]+): +([^\r\n]+)\r\n",
+				function(k,v)
+					field.headers[k] = v
+					return ""
+				end
+			)
+		until stat == 0
+
+		chunk, stat = chunk:gsub("^\r\n","")
+
+		-- End of headers
+		if stat > 0 then
+			if field.headers["Content-Disposition"] then
+				if field.headers["Content-Disposition"]:match("^form%-data; ") then
+					field.name = field.headers["Content-Disposition"]:match('name="(.-)"')
+					field.file = field.headers["Content-Disposition"]:match('filename="(.+)"$')
+				end
+			end
+
+			if not field.headers["Content-Type"] then
+				field.headers["Content-Type"] = "text/plain"
+			end
+
+			if field.name and field.file and filecb then
+				__initval( msg.params, field.name )
+				__appendval( msg.params, field.name, field.file )
+
+				store = filecb
+			elseif field.name then
+				__initval( msg.params, field.name )
+
+				store = function( hdr, buf, eof )
+					__appendval( msg.params, field.name, buf )
+				end
+			else
+				store = nil
+			end
+
+			return chunk, true
+		end
+
+		return chunk, false
+	end
+
+	local function snk( chunk )
+
+		tlen = tlen + ( chunk and #chunk or 0 )
+
+		if msg.env.CONTENT_LENGTH and tlen > tonumber(msg.env.CONTENT_LENGTH) + 2 then
+			return nil, "Message body size exceeds Content-Length"
+		end
+
+		if chunk and not lchunk then
+			lchunk = "\r\n" .. chunk
+
+		elseif lchunk then
+			local data = lchunk .. ( chunk or "" )
+			local spos, epos, found
+
+			repeat
+				spos, epos = data:find( "\r\n--" .. msg.mime_boundary .. "\r\n", 1, true )
+
+				if not spos then
+					spos, epos = data:find( "\r\n--" .. msg.mime_boundary .. "--\r\n", 1, true )
+				end
+
+
+				if spos then
+					local predata = data:sub( 1, spos - 1 )
+
+					if inhdr then
+						predata, eof = parse_headers( predata, field )
+
+						if not eof then
+							return nil, "Invalid MIME section header"
+						elseif not field.name then
+							return nil, "Invalid Content-Disposition header"
+						end
+					end
+
+					if store then
+						store( field, predata, true )
+					end
+
+
+					field = { headers = { } }
+					found = found or true
+
+					data, eof = parse_headers( data:sub( epos + 1, #data ), field )
+					inhdr = not eof
+				end
+			until not spos
+
+			if found then
+				if #data > 78 then
+					lchunk = data:sub( #data - 78 + 1, #data )
+					data   = data:sub( 1, #data - 78 )
+
+					if store then
+						store( field, data, false )
+					else
+						return nil, "Invalid MIME section header"
+					end
+				else
+					lchunk, data = data, nil
+				end
+			else
+				if inhdr then
+					lchunk, eof = parse_headers( data, field )
+					inhdr = not eof
+				else
+					store( field, lchunk, false )
+					lchunk, chunk = chunk, nil
+				end
+			end
+		end
+
+		return true
+	end
+
+	return ltn12.pump.all( src, snk )
+end
+
+--- Decode an urlencoded http message body with application/x-www-urlencoded
+-- Content-Type. Stores all extracted data associated with its parameter name
+-- in the params table withing the given message object. Multiple parameter
+-- values are stored as tables, ordinary ones as strings.
+-- @param src	Ltn12 source function
+-- @param msg	HTTP message object
+-- @return		Value indicating successful operation (not nil means "ok")
+-- @return		String containing the error if unsuccessful
+-- @see			parse_message_header
+function urldecode_message_body( src, msg )
+
+	local tlen   = 0
+	local lchunk = nil
+
+	local function snk( chunk )
+
+		tlen = tlen + ( chunk and #chunk or 0 )
+
+		if msg.env.CONTENT_LENGTH and tlen > tonumber(msg.env.CONTENT_LENGTH) + 2 then
+			return nil, "Message body size exceeds Content-Length"
+		elseif tlen > HTTP_MAX_CONTENT then
+			return nil, "Message body size exceeds maximum allowed length"
+		end
+
+		if not lchunk and chunk then
+			lchunk = chunk
+
+		elseif lchunk then
+			local data = lchunk .. ( chunk or "&" )
+			local spos, epos
+
+			repeat
+				spos, epos = data:find("^.-[;&]")
+
+				if spos then
+					local pair = data:sub( spos, epos - 1 )
+					local key  = pair:match("^(.-)=")
+					local val  = pair:match("=([^%s]*)%s*$")
+
+					if key and #key > 0 then
+						__initval( msg.params, key )
+						__appendval( msg.params, key, val )
+						__finishval( msg.params, key, urldecode )
+					end
+
+					data = data:sub( epos + 1, #data )
+				end
+			until not spos
+
+			lchunk = data
+		end
+
+		return true
+	end
+
+	return ltn12.pump.all( src, snk )
+end
+
+--- Try to extract an http message header including information like protocol
+-- version, message headers and resulting CGI environment variables from the
+-- given ltn12 source.
+-- @param src	Ltn12 source function
+-- @return		HTTP message object
+-- @see			parse_message_body
+function parse_message_header( src )
+
+	local ok   = true
+	local msg  = { }
+
+	local sink = ltn12.sink.simplify(
+		function( chunk )
+			return process_states['magic']( msg, chunk )
+		end
+	)
+
+	-- Pump input data...
+	while ok do
+
+		-- get data
+		ok, err = ltn12.pump.step( src, sink )
+
+		-- error
+		if not ok and err then
+			return nil, err
+
+		-- eof
+		elseif not ok then
+
+			-- Process get parameters
+			if ( msg.request_method == "get" or msg.request_method == "post" ) and
+			   msg.request_uri:match("?")
+			then
+				msg.params = urldecode_params( msg.request_uri )
+			else
+				msg.params = { }
+			end
+
+			-- Populate common environment variables
+			msg.env = {
+				CONTENT_LENGTH    = msg.headers['Content-Length'];
+				CONTENT_TYPE      = msg.headers['Content-Type'] or msg.headers['Content-type'];
+				REQUEST_METHOD    = msg.request_method:upper();
+				REQUEST_URI       = msg.request_uri;
+				SCRIPT_NAME       = msg.request_uri:gsub("?.+$","");
+				SCRIPT_FILENAME   = "";		-- XXX implement me
+				SERVER_PROTOCOL   = "HTTP/" .. string.format("%.1f", msg.http_version);
+				QUERY_STRING      = msg.request_uri:match("?")
+					and msg.request_uri:gsub("^.+?","") or ""
+			}
+
+			-- Populate HTTP_* environment variables
+			for i, hdr in ipairs( {
+				'Accept',
+				'Accept-Charset',
+				'Accept-Encoding',
+				'Accept-Language',
+				'Connection',
+				'Cookie',
+				'Host',
+				'Referer',
+				'User-Agent',
+			} ) do
+				local var = 'HTTP_' .. hdr:upper():gsub("%-","_")
+				local val = msg.headers[hdr]
+
+				msg.env[var] = val
+			end
+		end
+	end
+
+	return msg
+end
+
+--- Try to extract and decode a http message body from the given ltn12 source.
+-- This function will examine the Content-Type within the given message object
+-- to select the appropriate content decoder.
+-- Currently the application/x-www-urlencoded and application/form-data
+-- mime types are supported. If the encountered content encoding can't be
+-- handled then the whole message body will be stored unaltered as "content"
+-- property within the given message object.
+-- @param src		Ltn12 source function
+-- @param msg		HTTP message object
+-- @param filecb	File data callback (optional, see mimedecode_message_body())
+-- @return			Value indicating successful operation (not nil means "ok")
+-- @return			String containing the error if unsuccessful
+-- @see				parse_message_header
+function parse_message_body( src, msg, filecb )
+	-- Is it multipart/mime ?
+	if msg.env.REQUEST_METHOD == "POST" and msg.env.CONTENT_TYPE and
+	   msg.env.CONTENT_TYPE:match("^multipart/form%-data")
+	then
+
+		return mimedecode_message_body( src, msg, filecb )
+
+	-- Is it application/x-www-form-urlencoded ?
+	elseif msg.env.REQUEST_METHOD == "POST" and msg.env.CONTENT_TYPE and
+	       msg.env.CONTENT_TYPE:match("^application/x%-www%-form%-urlencoded")
+	then
+		return urldecode_message_body( src, msg, filecb )
+
+
+	-- Unhandled encoding
+	-- If a file callback is given then feed it chunk by chunk, else
+	-- store whole buffer in message.content
+	else
+
+		local sink
+
+		-- If we have a file callback then feed it
+		if type(filecb) == "function" then
+			sink = filecb
+
+		-- ... else append to .content
+		else
+			msg.content = ""
+			msg.content_length = 0
+
+			sink = function( chunk, err )
+				if chunk then
+					if ( msg.content_length + #chunk ) <= HTTP_MAX_CONTENT then
+						msg.content        = msg.content        .. chunk
+						msg.content_length = msg.content_length + #chunk
+						return true
+					else
+						return nil, "POST data exceeds maximum allowed length"
+					end
+				end
+				return true
+			end
+		end
+
+		-- Pump data...
+		while true do
+			local ok, err = ltn12.pump.step( src, sink )
+
+			if not ok and err then
+				return nil, err
+			elseif not err then
+				return true
+			end
+		end
+
+		return true
+	end
+end
+
+--- Table containing human readable messages for several http status codes.
+-- @class table
+statusmsg = {
+	[200] = "OK",
+	[206] = "Partial Content",
+	[301] = "Moved Permanently",
+	[302] = "Found",
+	[304] = "Not Modified",
+	[400] = "Bad Request",
+	[403] = "Forbidden",
+	[404] = "Not Found",
+	[405] = "Method Not Allowed",
+	[408] = "Request Time-out",
+	[411] = "Length Required",
+	[412] = "Precondition Failed",
+	[416] = "Requested range not satisfiable",
+	[500] = "Internal Server Error",
+	[503] = "Server Unavailable",
+}
diff --git a/libs/web/luasrc/http/protocol/conditionals.lua b/libs/web/luasrc/http/protocol/conditionals.lua
new file mode 100644
index 000000000..75e1f7b37
--- /dev/null
+++ b/libs/web/luasrc/http/protocol/conditionals.lua
@@ -0,0 +1,153 @@
+--[[
+
+HTTP protocol implementation for LuCI - RFC2616 / 14.19, 14.24 - 14.28
+(c) 2008 Freifunk Leipzig / Jo-Philipp Wich <xm@leipzig.freifunk.net>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+$Id$
+
+]]--
+
+--- LuCI http protocol implementation - HTTP/1.1 bits.
+-- This class provides basic ETag handling and implements most of the
+-- conditional HTTP/1.1 headers specified in RFC2616 Sct. 14.24 - 14.28 .
+module("luci.http.protocol.conditionals", package.seeall)
+
+local date = require("luci.http.protocol.date")
+
+
+--- Implement 14.19 / ETag.
+-- @param stat	A file.stat structure
+-- @return		String containing the generated tag suitable for ETag headers
+function mk_etag( stat )
+	if stat ~= nil then
+		return string.format( '"%x-%x-%x"', stat.ino, stat.size, stat.mtime )
+	end
+end
+
+--- 14.24 / If-Match
+-- Test whether the given message object contains an "If-Match" header and
+-- compare it against the given stat object.
+-- @param req	HTTP request message object
+-- @param stat	A file.stat object
+-- @return		Boolean indicating whether the precondition is ok
+-- @return		Alternative status code if the precondition failed
+function if_match( req, stat )
+	local h    = req.headers
+	local etag = mk_etag( stat )
+
+	-- Check for matching resource
+	if type(h['If-Match']) == "string" then
+		for ent in h['If-Match']:gmatch("([^, ]+)") do
+			if ( ent == '*' or ent == etag ) and stat ~= nil then
+				return true
+			end
+		end
+
+		return false, 412
+	end
+
+	return true
+end
+
+--- 14.25 / If-Modified-Since
+-- Test whether the given message object contains an "If-Modified-Since" header
+-- and compare it against the given stat object.
+-- @param req	HTTP request message object
+-- @param stat	A file.stat object
+-- @return		Boolean indicating whether the precondition is ok
+-- @return		Alternative status code if the precondition failed
+-- @return		Table containing extra HTTP headers if the precondition failed
+function if_modified_since( req, stat )
+	local h = req.headers
+
+	-- Compare mtimes
+	if type(h['If-Modified-Since']) == "string" then
+		local since = date.to_unix( h['If-Modified-Since'] )
+
+		if stat == nil or since < stat.mtime then
+			return true
+		end
+
+		return false, 304, {
+			["ETag"]          = mk_etag( stat );
+			["Date"]          = date.to_http( os.time() );
+			["Last-Modified"] = date.to_http( stat.mtime )
+		}
+	end
+
+	return true
+end
+
+--- 14.26 / If-None-Match
+-- Test whether the given message object contains an "If-None-Match" header and
+-- compare it against the given stat object.
+-- @param req	HTTP request message object
+-- @param stat	A file.stat object
+-- @return		Boolean indicating whether the precondition is ok
+-- @return		Alternative status code if the precondition failed
+-- @return		Table containing extra HTTP headers if the precondition failed
+function if_none_match( req, stat )
+	local h      = req.headers
+	local etag   = mk_etag( stat )
+	local method = req.env and req.env.REQUEST_METHOD or "GET"
+
+	-- Check for matching resource
+	if type(h['If-None-Match']) == "string" then
+		for ent in h['If-None-Match']:gmatch("([^, ]+)") do
+			if ( ent == '*' or ent == etag ) and stat ~= nil then
+				if method == "GET" or method == "HEAD" then
+					return false, 304, {
+						["ETag"]          = etag;
+						["Date"]          = date.to_http( os.time() );
+						["Last-Modified"] = date.to_http( stat.mtime )
+					}
+				else
+					return false, 412
+				end
+			end
+		end
+	end
+
+	return true
+end
+
+--- 14.27 / If-Range
+-- The If-Range header is currently not implemented due to the lack of general
+-- byte range stuff in luci.http.protocol . This function will always return
+-- false, 412 to indicate a failed precondition.
+-- @param req	HTTP request message object
+-- @param stat	A file.stat object
+-- @return		Boolean indicating whether the precondition is ok
+-- @return		Alternative status code if the precondition failed
+function if_range( req, stat )
+	-- Sorry, no subranges (yet)
+	return false, 412
+end
+
+--- 14.28 / If-Unmodified-Since
+-- Test whether the given message object contains an "If-Unmodified-Since"
+-- header and compare it against the given stat object.
+-- @param req	HTTP request message object
+-- @param stat	A file.stat object
+-- @return		Boolean indicating whether the precondition is ok
+-- @return		Alternative status code if the precondition failed
+function if_unmodified_since( req, stat )
+	local h = req.headers
+
+	-- Compare mtimes
+	if type(h['If-Unmodified-Since']) == "string" then
+		local since = date.to_unix( h['If-Unmodified-Since'] )
+
+		if stat ~= nil and since <= stat.mtime then
+			return false, 412
+		end
+	end
+
+	return true
+end
diff --git a/libs/web/luasrc/http/protocol/date.lua b/libs/web/luasrc/http/protocol/date.lua
new file mode 100644
index 000000000..83d11e2c2
--- /dev/null
+++ b/libs/web/luasrc/http/protocol/date.lua
@@ -0,0 +1,115 @@
+--[[
+
+HTTP protocol implementation for LuCI - date handling
+(c) 2008 Freifunk Leipzig / Jo-Philipp Wich <xm@leipzig.freifunk.net>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+$Id$
+
+]]--
+
+--- LuCI http protocol implementation - date helper class.
+-- This class contains functions to parse, compare and format http dates.
+module("luci.http.protocol.date", package.seeall)
+
+require("luci.sys.zoneinfo")
+
+
+MONTHS = {
+	"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
+	"Sep", "Oct", "Nov", "Dec"
+}
+
+--- Return the time offset in seconds between the UTC and given time zone.
+-- @param tz	Symbolic or numeric timezone specifier
+-- @return		Time offset to UTC in seconds
+function tz_offset(tz)
+
+	if type(tz) == "string" then
+
+		-- check for a numeric identifier
+		local s, v = tz:match("([%+%-])([0-9]+)")
+		if s == '+' then s = 1 else s = -1 end
+		if v then v = tonumber(v) end
+
+		if s and v then
+			return s * 60 * ( math.floor( v / 100 ) * 60 + ( v % 100 ) )
+
+		-- lookup symbolic tz
+		elseif luci.sys.zoneinfo.OFFSET[tz:lower()] then
+			return luci.sys.zoneinfo.OFFSET[tz:lower()]
+		end
+
+	end
+
+	-- bad luck
+	return 0
+end
+
+--- Parse given HTTP date string and convert it to unix epoch time.
+-- @param data	String containing the date
+-- @return		Unix epoch time
+function to_unix(date)
+
+	local wd, day, mon, yr, hr, min, sec, tz = date:match(
+		"([A-Z][a-z][a-z]), ([0-9]+) " ..
+		"([A-Z][a-z][a-z]) ([0-9]+) " ..
+		"([0-9]+):([0-9]+):([0-9]+) " ..
+		"([A-Z0-9%+%-]+)"
+	)
+
+	if day and mon and yr and hr and min and sec then
+		-- find month
+		local month = 1
+		for i = 1, 12 do
+			if MONTHS[i] == mon then
+				month = i
+				break
+			end
+		end
+
+		-- convert to epoch time
+		return tz_offset(tz) + os.time( {
+			year  = yr,
+			month = month,
+			day   = day,
+			hour  = hr,
+			min   = min,
+			sec   = sec
+		} )
+	end
+
+	return 0
+end
+
+--- Convert the given unix epoch time to valid HTTP date string.
+-- @param time	Unix epoch time
+-- @return		String containing the formatted date
+function to_http(time)
+	return os.date( "%a, %d %b %Y %H:%M:%S GMT", time )
+end
+
+--- Compare two dates which can either be unix epoch times or HTTP date strings.
+-- @param d1	The first date or epoch time to compare
+-- @param d2	The first date or epoch time to compare
+-- @return		-1  -  if d1 is lower then d2
+-- @return		0   -  if both dates are equal
+-- @return		1   -  if d1 is higher then d2
+function compare(d1, d2)
+
+	if d1:match("[^0-9]") then d1 = to_unix(d1) end
+	if d2:match("[^0-9]") then d2 = to_unix(d2) end
+
+	if d1 == d2 then
+		return 0
+	elseif d1 < d2 then
+		return -1
+	else
+		return 1
+	end
+end
diff --git a/libs/web/luasrc/http/protocol/mime.lua b/libs/web/luasrc/http/protocol/mime.lua
new file mode 100644
index 000000000..c87816066
--- /dev/null
+++ b/libs/web/luasrc/http/protocol/mime.lua
@@ -0,0 +1,99 @@
+--[[
+
+HTTP protocol implementation for LuCI - mime handling
+(c) 2008 Freifunk Leipzig / Jo-Philipp Wich <xm@leipzig.freifunk.net>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+$Id$
+
+]]--
+
+--- LuCI http protocol implementation - mime helper class.
+-- This class provides functions to guess mime types from file extensions and
+-- vice versa.
+module("luci.http.protocol.mime", package.seeall)
+
+require("luci.util")
+
+--- MIME mapping table containg extension - mimetype relations.
+-- @class table
+MIME_TYPES = {
+    ["txt"]   = "text/plain";
+    ["js"]    = "text/javascript";
+    ["css"]   = "text/css";
+    ["htm"]   = "text/html";
+    ["html"]  = "text/html";
+    ["patch"] = "text/x-patch";
+    ["c"]     = "text/x-csrc";
+    ["h"]     = "text/x-chdr";
+    ["o"]     = "text/x-object";
+    ["ko"]    = "text/x-object";
+
+    ["bmp"]   = "image/bmp";
+    ["gif"]   = "image/gif";
+    ["png"]   = "image/png";
+    ["jpg"]   = "image/jpeg";
+    ["jpeg"]  = "image/jpeg";
+    ["svg"]   = "image/svg+xml";
+
+    ["zip"]   = "application/zip";
+    ["pdf"]   = "application/pdf";
+    ["xml"]   = "application/xml";
+    ["xsl"]   = "application/xml";
+    ["doc"]   = "application/msword";
+    ["ppt"]   = "application/vnd.ms-powerpoint";
+    ["xls"]   = "application/vnd.ms-excel";
+    ["odt"]   = "application/vnd.oasis.opendocument.text";
+    ["odp"]   = "application/vnd.oasis.opendocument.presentation";
+    ["pl"]    = "application/x-perl";
+    ["sh"]    = "application/x-shellscript";
+    ["php"]   = "application/x-php";
+    ["deb"]   = "application/x-deb";
+    ["iso"]   = "application/x-cd-image";
+    ["tgz"]   = "application/x-compressed-tar";
+
+    ["mp3"]   = "audio/mpeg";
+    ["ogg"]   = "audio/x-vorbis+ogg";
+    ["wav"]   = "audio/x-wav";
+
+    ["mpg"]   = "video/mpeg";
+    ["mpeg"]  = "video/mpeg";
+    ["avi"]   = "video/x-msvideo";
+}
+
+--- Extract extension from a filename and return corresponding mime-type or
+-- "application/octet-stream" if the extension is unknown.
+-- @param filename	The filename for which the mime type is guessed
+-- @return			String containign the determined mime type
+function to_mime(filename)
+	if type(filename) == "string" then
+		local ext = filename:match("[^%.]+$")
+
+		if ext and MIME_TYPES[ext:lower()] then
+			return MIME_TYPES[ext:lower()]
+		end
+	end
+
+	return "application/octet-stream"
+end
+
+--- Return corresponding extension for a given mime type or nil if the
+-- given mime-type is unknown.
+-- @param mimetype	The mimetype to retrieve the extension from
+-- @return			String with the extension or nil for unknown type
+function to_ext(mimetype)
+	if type(mimetype) == "string" then
+		for ext, type in luci.util.kspairs( MIME_TYPES ) do
+			if type == mimetype then
+				return ext
+			end
+		end
+	end
+
+	return nil
+end