AbsoLUAtion » History » Revision 48
Revision 47 (gstrauss, 2021-12-07 06:38) → Revision 48/55 (gstrauss, 2021-12-19 03:58)
h1. AbsoLUAtion - The powerful combo of lighttpd + Lua
{{>toc}}
We want to build a central resource for lighttpd + Lua as this is one of the biggest advantages lighttpd has over other webservers. It's useful, handy, simple and sometimes a quite powerful combo which gives you some additional flexibility and offers you solutions to small and big problems other httpds can't solve!
Again, we hope that you, the users of lighttpd, support this page by contributing links, code-snippets or simply offer your lua scripts with small descriptions of what they do and how it helps lighttpd to do stuff you want it to do.
h1. Requirements
* lighttpd [[lighttpd:Docs_ModMagnet|mod_magnet]]
* Lua (v5.1; lighttpd 1.4.40+ should also support v5.2, v5.3, v5.4) http://www.lua.org
h1. Links
* [[ModMagnetExamples#lua-examples-of-lighttpd-modules|lua examples of lighttpd modules]]
* http://www.sitepoint.com/blogs/2007/04/10/faster-page-loads-bundle-your-css-and-javascript/
* WP-MultiUser http://www.bisente.com/blog/2007/04/08/lighttpd-wordpressmu-english/
* Dynamically generate thumbnails and cache them http://www.xarg.org/2010/04/dynamic-thumbnail-generation-on-the-static-server/
* Drupal/OpenAtrium simple cleanurl solution "drupal-clean-url-lighttpd":https://web.archive.org/web/20100820100050/http://sudhaker.com:80/web-development/drupal/drupal-clean-url-lighttpd.html
* Authentication through openid and the likes https://github.com/chmduquesne/lighttpd-external-auth ("blog post":http://blog.chmd.fr/using-openid-and-the-likes-to-protect-static-content-lighttpd.html)
Dead links? You don´t like to be listed here? Please remove it. Thanks!
h1. Code-Snippets
*Apache .htaccess alternatives*
A common idiom in Apache .htaccess:
@RewriteCond %{REQUEST_FILENAME} !-f@
@RewriteCond %{REQUEST_FILENAME} !-d@
@RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]@
lighttpd alternatives:
* [[lighttpd:Docs_ModRewrite#urlrewrite-repeat-if-not-file|url.rewrite-if-not-file]] (recommended if !-f is sufficient; does not check !-d)
* [[lighttpd:ModMagnetExamples#lua-mod_rewrite|lua mod_rewrite]] (*recommended*; simpler than option below)
* mod_magnet rewrite paths without restarting request (below)
As lighttpd doesn't provide this is_file/is_dir check out of the box, again mod_magnet comes into play. I took the example for drupal from darix site.
Lets assume drupal is already installed under http://example.com/drupal/ you now add the magnet part to it.
<pre>
$HTTP["url"] =~ "^/drupal" {
# we only need index.php here.
index-file.names = ( "index.php" )
# for clean urls
magnet.attract-physical-path-to = ( "/etc/lighttpd/drupal.lua" )
}
</pre>
The drupal.lua:
<pre>
-- little helper function
function file_exists(path)
return lighty.stat(path) and true or false
end
function removePrefix(str, prefix)
return str:sub(1,#prefix+1) == prefix.."/" and str:sub(#prefix+2)
end
-- prefix without the trailing slash
local prefix = '/drupal'
-- the magic ;)
if (not file_exists(lighty.env["physical.path"])) then
-- file still missing. pass it to the fastcgi backend
request_uri = removePrefix(lighty.env["uri.path"], prefix)
if request_uri then
lighty.env["uri.path"] = prefix .. "/index.php"
local uriquery = lighty.env["uri.query"] or ""
lighty.env["uri.query"] = uriquery .. (uriquery ~= "" and "&" or "") .. "q=" .. request_uri
lighty.env["physical.rel-path"] = lighty.env["uri.path"]
lighty.env["request.orig-uri"] = lighty.env["request.uri"]
lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"]
end
end
-- fallthrough will put it back into the lighttpd request loop
-- that means we get the 304 handling for free. ;)
</pre>
*Overwrite default mime-type/content-type*
Add "magnet.attract-physical-path-to = ( "/path-to/change-ctype.lua" )" to lighttpd.conf and save the following as "change-ctype.lua"
<pre>
if (string.match(lighty.env["physical.rel-path"], ".swf")) then
lighty.header["Content-Type"] = "text/html"
end
</pre>
*Sending text-files as HTML*
This is a bit simplistic, but it illustrates the idea: Take a text-file and cover it in a "< pre >" tag.
Config-file
<pre>
magnet.attract-physical-path-to = (server.docroot + "/readme.lua")
</pre>
readme.lua
<pre>
lighty.content = { "<pre>", { filename = "/README" }, "</pre>" }
lighty.header["Content-Type"] = "text/html"
return 200
</pre>
*Redirect map*
"redirect-map.lua":https://redmine.lighttpd.net/attachments/2065 redirect-map based on url-path
*Simple maintenance script*
You need three files, maint.up, maint.down and maint.html.
maint.html holds a simple html-page of what you want to display to your users while in maintenance-mode.
Add "magnet.attract-physical-path-to = ( "/path-to-your/maint.lua" )" to your lighttpd.conf, best is global section or within a host-section of your config, e.g. a board/forum/wiki you know a maintenance-mode is needed from time to time. If you want to switch to maintenance-mode, just copy maint.down to maint.lua in your "/path-to-your/" location, and lighttpd will display your maint.html to all users - without restarting anything - this can be done on-the-fly. Work is done and all is up again? Copy maint.up to maint.lua in your "/path-to-your/" location. Whats maint.up doing? Nothing, just going on with normal file serving :-)
maint.up - all is up, user will see normal pages
<pre>
-- This is empty, nothing to do.
</pre>
maint.down - lighttpd will show the maintenance page -> maint.html
<pre>
-- lighty.header["X-Maintenance-Mode"] = "1"
-- uncomment the above if you want to add the header
lighty.content = { { filename = "/path-to-your/maint.html" } }
lighty.header["Content-Type"] = "text/html"
return 503
-- or return 200 if you want
</pre>
*custom error pages*
mod_magnet can be used to implement any or all of the lighttpd directives: @server.error-handler@, @server.error-handler-404@, @server.errorfile-prefix@, @server.error-intercept@
@magnet.attract-response-start-to = ( "/absolute/path/to/script.lua" )@
<pre>
-- intercept all HTTP status errors (e.g. server.error-intercept = "enable")
local r = lighty.r
local http_status = r.req_attr["response.http-status"];
if (http_status < 400) -- not an HTTP status error; do not modify
return 0
end
-- send back custom error page (similar to server.errorfile-prefix)
-- replace existing response body, if any
local errfile = "/path/to/errfiles/" .. http_status .. ".html"
local st = lighty.c.stat(errfile)
if (not st) then
errfile = "/path/to/errfiles/generic.html"
fi
r.resp_body:set({ { filename = errfile } })
-- (alternative: construct custom error page (similar to server.error-handler))
return http_status
</pre>
*selecting a random file from a directory*
Say, you want to send a random file (ad-content) from a directory.
To simplify the code and to improve the performance we define:
* all images have the same format (e.g. image/png)
* all images use increasing numbers starting from 1
* a special index-file names the highest number
Config
<pre>
server.modules += ( "mod_magnet" )
magnet.attract-physical-path-to = ("random.lua")
</pre>
random.lua
<pre>
dir = lighty.env["physical.path"]
f = assert(io.open(dir .. "/index", "r"))
maxndx = f:read("*all")
f:close()
ndx = math.random(maxndx)
lighty.content = { { filename = dir .. "/" .. ndx }}
lighty.header["Content-Type"] = "image/png"
return 200
</pre>
*denying illegal character sequences in the URL*
Instead of implementing mod_security, you might just want to apply filters on the content and deny special sequences that look like SQL injection.
A common injection is using UNION to extend a query with another SELECT query.
<pre>
if (string.find(lighty.env["request.uri"], "UNION%s")) then
return 400
end
</pre>
*Traffic Quotas*
If you only allow your virtual hosts a certain amount for traffic each month and want to disable them if the traffic is reached, perhaps this helps:
<pre>
host_blacklist = { ["www.example.org"] = 0 }
if (host_blacklist[lighty.request["Host"]]) then
return 404
end
</pre>
Just add the hosts you want to blacklist into the blacklist table in the shown way.
*Complex rewrites*
If you want to implement caching on your document-root and only want to regenerate content if the requested file doesn't exist, you can attract the physical.path:
<pre>
magnet.attract-physical-path-to = ( server.document-root + "/rewrite.lua" )
</pre>
rewrite.lua
<pre>
attr = lighty.stat(lighty.env["physical.path"])
if (not attr) then
-- we couldn't stat() the file for some reason
-- let the backend generate it
lighty.env["uri.path"] = "/dispatch.fcgi"
lighty.env["physical.rel-path"] = lighty.env["uri.path"]
lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"]
end
</pre>
*Extension rewrites*
If you want to hide your file extensions (like .php) you can attract the physical.path:
<pre>
magnet.attract-physical-path-to = ( server.document-root + "/rewrite.lua" )
</pre>
rewrite.lua
<pre>
attr = lighty.stat(lighty.env["physical.path"] .. ".php")
if (attr) then
lighty.env["uri.path"] = lighty.env["uri.path"] .. ".php"
lighty.env["physical.rel-path"] = lighty.env["uri.path"]
lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"]
end
</pre>
*User tracking*
... or how to store data globally in the script-context:
Each script has its own script-context. When the script is started it only contains the lua-functions and the special lighty.* name-space. If you want to save data between script runs, you can use the global-script context:
<pre>
if (nil == _G["usertrack"]) then
_G["usertrack"] = {}
end
if (nil == _G["usertrack"][lighty.request["Cookie"]]) then
_G["usertrack"][lighty.request["Cookie"]]
else
_G["usertrack"][lighty.request["Cookie"]] = _G["usertrack"][lighty.request["Cookie"]] + 1
end
print _G["usertrack"][lighty.request["Cookie"]]
</pre>
The global-context is per script. If you update the script without restarting the server, the context will still be maintained.
*WordpressMU*
wpmu.lua
<pre>
if (not lighty.stat(lighty.env["physical.path"])) then
if (string.match(lighty.env["uri.path"], "^(/?[^/]*/)files/$")) then
lighty.env["physical.rel-path"] = "index.php"
else
n, a = string.match(lighty.env["uri.path"], "^(/?[^/]*/)files/(.+)")
if a then
lighty.env["physical.rel-path"] = "wp-content/blogs.php"
lighty.env["uri.query"] = "file=" .. a
else
n, a = string.match(lighty.env["uri.path"], "^(/[^/]*)/(wp-.*)")
if a then
lighty.env["physical.rel-path"] = a;
else
n, a = string.match(lighty.env["uri.path"], "^(/[^/]*)/(.*\.php)$")
if a then
lighty.env["physical.rel-path"] = a
else
lighty.env["physical.rel-path"] = "index.php"
end
end
end
end
lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. "/".. lighty.env["physical.rel-path"]
end
</pre>
h1. Content Negotiation
content-negotiation.lua to parse Accept-Language and Accept-Encoding (#2678, #2736) to determine best target file
"content-negotiation.lua":https://redmine.lighttpd.net/attachments/2012
Related, see #1259 for lua code to try multiple extensions (a la Apache mod_autoext) to find target file
h1. Fight DDoS
If your Server is under high load because of someone is flooding you with requests, a little bit lua might help you. ;) In our case we've got a lot of requests without a User-Agent in the request header.
<pre>if ( lighty.request["User-Agent"]== nil ) then
file = io.open ("ips.txt","a")
file:write(lighty.env["request.remote-ip"])
file:write("\n")
file:close()
return 200
end</pre>
The field request.remote-ip is available since lighttpd 1.4.23. The file ips.txt must be writeable by the lighttpd user (www-data). The bad guys in the ips.txt file can be dropped into the firewall with a little shell script.
lua can also be used to access a database and reject requests based on data in the database.
See sample "reject-bad-actors.lua":https://redmine.lighttpd.net/attachments/2064 attached in Files section at the bottom of this page. It uses an mcdb constant database for fast lookups.
h1. Mod_Security
Apache has mod_security available as a WAF (web application firewall) however this isn't available for other webservers. I've written a quick and dirty script to perform a similar task to mod_security using mod_magnet
"lighttpd-mod_security-via-mod_magnet":https://web.archive.org/web/20160311005141/http://whmcr.com/2009/06/19/lighttpd-mod_security-via-mod_magnet
I've been recently working on libmodsecurity binding for openresty which is a nginx+luajit combo. Using patched "libmodsecurity":https://github.com/pr4u4t/ModSecurity and "cffi-lua":https://github.com/q66/cffi-lua along with "modsec.lua":https://luarocks.org/modules/pr4u4t/modsec and mod_magnet lighttpd can perform incoming request inspection. Currently there is no way to perform request body (POST) and response inspection. Two last would involve additional lua entry points in lighty. Security rules could be obtained at "coreruleset":https://github.com/coreruleset/coreruleset.
waf.lua for lighttpd:
<pre>
local modsec = require "modsec"
local ok, err = modsec.init("/etc/owasp/modsec.conf")
if not ok then
print(err)
return
end
local transaction = modsec.transaction()
if not transaction then
print("Failed to initialize transaction")
end
-- evaluate connection info and request headers
local req_attr = lighty.r.req_attr
local url = req_attr["uri.scheme"]
.. "://"
.. req_attr["uri.authority"]
.. req_attr["uri.path-raw"]
.. (req_attr["uri.query"] and ("?" .. req_attr["uri.query"]) or "")
local res, err = transaction:eval_connection(req_attr["request.remote-addr"],req_attr["request.remote-port"],
req_attr["uri.authority"],req_attr["request.server-port"],url,
req_attr["request.method"],req_attr["request.protocol"])
if err then
print("Failed to evaluate connection: ",err)
end
local res, err = transaction:eval_request_headers(lighty.r.req_header)
if err then
print("Failed to evaluate request headers: ",err)
end
--[[ evaluate request body
Currently no way to evaluate request body
but this function must be run even with nil as arguments
]]
local res, err = transaction:eval_request_body(nil,nil)
if err then
print("Failed to evaluate request body: ",err)
end
-- Here decision could be made upon modsecurity variables whether handle this request or not
local score = tonumber(transaction.var.tx.anomaly_score)
if score >= 8 then
print("This request looks nasty overall score is: "..score)
return 403
end
</pre>
Example of owasp/modsec.conf
<pre>
#This is libmodsecurity base configuration
Include modsecurity.conf
Include /opt/openresty/owasp/crs-setup.conf
Include /opt/openresty/owasp/rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf
Include /opt/openresty/owasp/rules/REQUEST-901-INITIALIZATION.conf
Include /opt/openresty/owasp/rules/REQUEST-905-COMMON-EXCEPTIONS.conf
Include /opt/openresty/owasp/rules/REQUEST-910-IP-REPUTATION.conf
Include /opt/openresty/owasp/rules/REQUEST-911-METHOD-ENFORCEMENT.conf
Include /opt/openresty/owasp/rules/REQUEST-912-DOS-PROTECTION.conf
Include /opt/openresty/owasp/rules/REQUEST-913-SCANNER-DETECTION.conf
Include /opt/openresty/owasp/rules/REQUEST-920-PROTOCOL-ENFORCEMENT.conf
Include /opt/openresty/owasp/rules/REQUEST-921-PROTOCOL-ATTACK.conf
Include /opt/openresty/owasp/rules/REQUEST-930-APPLICATION-ATTACK-LFI.conf
Include /opt/openresty/owasp/rules/REQUEST-931-APPLICATION-ATTACK-RFI.conf
Include /opt/openresty/owasp/rules/REQUEST-932-APPLICATION-ATTACK-RCE.conf
Include /opt/openresty/owasp/rules/REQUEST-933-APPLICATION-ATTACK-PHP.conf
Include /opt/openresty/owasp/rules/REQUEST-941-APPLICATION-ATTACK-XSS.conf
Include /opt/openresty/owasp/rules/REQUEST-942-APPLICATION-ATTACK-SQLI.conf
Include /opt/openresty/owasp/rules/REQUEST-943-APPLICATION-ATTACK-SESSION-FIXATION.conf
Include /opt/openresty/owasp/rules/REQUEST-949-BLOCKING-EVALUATION.conf
Include /opt/openresty/owasp/rules/RESPONSE-950-DATA-LEAKAGES.conf
Include /opt/openresty/owasp/rules/RESPONSE-951-DATA-LEAKAGES-SQL.conf
Include /opt/openresty/owasp/rules/RESPONSE-952-DATA-LEAKAGES-JAVA.conf
Include /opt/openresty/owasp/rules/RESPONSE-953-DATA-LEAKAGES-PHP.conf
Include /opt/openresty/owasp/rules/RESPONSE-954-DATA-LEAKAGES-IIS.conf
Include /opt/openresty/owasp/rules/RESPONSE-959-BLOCKING-EVALUATION.conf
Include /opt/openresty/owasp/rules/RESPONSE-980-CORRELATION.conf
Include /opt/openresty/owasp/rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf
</pre>
h1. security responses
lua scripts can be deployed quickly as a security response in order to mitigate exploits against CGI and other backends.
<pre>
-- reject request if request-line URL or request headers contain literal '{'
--
-- If not expecting literal '{' in HTTP requests, then this heuristic to
-- reject '{' thwarts certain classes of attacks on servers behind lighttpd.
-- - Log4Shell CVE-2021-44228 (and related) (Apache log4j RCE)
-- - Shellshock CVE-2014-6271 (and related) (Bash env RCE)
--
local r = lighty.r
-- check url-path (url-decoded) for literal '{'
if (string.find(r.req_attr["uri.path"], "{")) then
return 403
end
-- check query-string (url-encoded) for literal '{'
if (string.find(r.req_attr["uri.query"], "{")) then
return 403
end
-- check request headers for literal '{'
local req_header = r.req_header
local v
for _, v in ipairs(req_header) do
if (string.find(v, "{")) then
return 403
end
done
return 0
</pre>
h1. other solutions
*external-static*
I´ve seen this nice solution somewhere where they host some files locally on their machines. If popularity gets to high, files are too big or for whatever reasons the files are moved to i think it was amazon´s S3 or akamai for faster serving or to cope with high traffic. You still can use your hostname, urls, collect stats from your logs - your users are just redirected with a 302 to the files they ask for.
2008-11-17: Found the source: "presto-move-content-to-s3-with-no-code-changes":https://web.archive.org/web/20120817090808/http://www.innerfence.com/blog/2008/05/31/presto-move-content-to-s3-with-no-code-changes/
Request -> check for local copy -> 302 (if not stored locally) -> let users download from a big pipe
Add the following to your lighttpd.conf:
<pre>
$HTTP["url"] =~ "^/static/[^/]+[.]gif([?].*)?$" { #match the files you want this to work for
magnet.attract-physical-path-to = ( "/path-to-your/external-static.lua" )
}
</pre>
Save the following to external-static.lua:
<pre>
local filename = lighty.env["physical.path"]
local stat = lighty.stat( filename )
if not stat then
local static_name = string.match( filename, "static/([^/]+)$" )
lighty.header["Location"] = "http://<new-location-with-big-pipes>/" .. static_name
return 302
end
</pre>
h1. Sample Files