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Moar epic refactoring ... merge 'helpers.lua' inside 'access.lua' to reduce complexity ...

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Alexandre Aubin 2023-07-15 19:51:31 +02:00
parent df094ea0e3
commit 02952d0202
4 changed files with 263 additions and 272 deletions
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275
access.lua
View file

@ -2,64 +2,153 @@
-- access.lua
--
-- This file is executed at every request on a protected domain or server.
-- You just have to read this file normally to understand how and when the
-- request is handled: redirected, forbidden, bypassed or served.
--
-- Import helpers
local hlp = require("helpers")
-- Initialize and get configuration
hlp.refresh_config()
local conf = hlp.get_config()
-- Just a note for the client to know that he passed through the SSO
ngx.header["X-SSO-WAT"] = "You've just been SSOed"
local is_logged_in = hlp.check_authentication()
-- Misc imports
local jwt = require("vendor.luajwtjitsi.luajwtjitsi")
local cipher = require('openssl.cipher')
local rex = require("rex_pcre")
--
-- 3. REDIRECTED URLS
--
-- If the URL matches one of the `redirected_urls` in the configuration file,
-- just redirect to the target URL/URI
--
-- ###########################################################################
-- 0. Misc helpers because Lua has no sugar ...
-- ###########################################################################
function detect_redirection(redirect_url)
if hlp.string.starts(redirect_url, "http://")
or hlp.string.starts(redirect_url, "https://") then
return hlp.redirect(redirect_url)
elseif hlp.string.starts(redirect_url, "/") then
return hlp.redirect(ngx.var.scheme.."://"..ngx.var.host..redirect_url)
-- Get configuration (we do this here, the conf is re-read every time unless
-- the file's timestamp didnt change)
local config = require("config")
local conf = config.get_config()
-- The 'match' function uses PCRE regex as default
-- If '%.' is found in the regex, we assume it's a LUA regex (legacy code)
-- 'match' returns the matched text.
function match(s, regex)
if not string.find(regex, '%%%.') then
return rex.match(s, regex)
else
return hlp.redirect(ngx.var.scheme.."://"..redirect_url)
return string.match(s,regex)
end
end
-- Test whether a string starts with another
function string.starts(String, Start)
if not String then
return false
end
return string.sub(String, 1, string.len(Start)) == Start
end
-- Convert a table of arguments to an URI string
function uri_args_string(args)
if not args then
args = ngx.req.get_uri_args()
end
String = "?"
for k,v in pairs(args) do
String = String..tostring(k).."="..tostring(v).."&"
end
return string.sub(String, 1, string.len(String) - 1)
end
-- ###########################################################################
-- 1. AUTHENTICATION
-- Check wether or not this is a logged-in user
-- ###########################################################################
function check_authentication()
-- cf. src/authenticators/ldap_ynhuser.py in YunoHost to see how the cookie is actually created
local cookie = ngx.var["cookie_" .. conf["cookie_name"]]
decoded, err = jwt.verify(cookie, "HS256", cookie_secret)
-- FIXME : we might want also a way to identify expired/invalidated cookies,
-- e.g. a user that got deleted after being logged in ...
if err ~= nil then
return false, nil, nil
else
return true, decoded["user"], decoded["pwd"]
end
end
local is_logged_in, authUser, authPasswordEnc = check_authentication()
-- ###########################################################################
-- 2. REDIRECTED URLS
-- If the URL matches one of the `redirected_urls` in the configuration file,
-- just redirect to the target URL/URI
-- ###########################################################################
function redirect(url)
logger:debug("Redirecting to "..url)
-- For security reason we don't allow to redirect onto unknown domain
-- And if `uri_args.r` contains line break, someone is probably trying to
-- pass some additional headers
-- This should cover the following cases:
-- https://malicious.domain.tld/foo/bar
-- http://malicious.domain.tld/foo/bar
-- https://malicious.domain.tld:1234/foo
-- malicious.domain.tld/foo/bar
-- (/foo/bar, in which case no need to make sure it's prefixed with https://)
if not string.starts(url, "/") and not string.starts(url, "http://") and not string.starts(url, "https://") then
url = "https://"..url
end
local is_known_domain = string.starts(url, "/")
for _, domain in ipairs(conf["domains"]) do
if is_known_domain then
break
end
-- Replace - character to %- because - is a special char for regex in lua
domain = string.gsub(domain, "%-","%%-")
is_known_domain = is_known_domain or url:match("^https?://"..domain.."/?") ~= nil
end
if string.match(url, "(.*)\n") or not is_known_domain then
logger:debug("Unauthorized redirection to "..url)
url = conf.portal_url
end
return ngx.redirect(url)
end
function convert_to_absolute_url(redirect_url)
if string.starts(redirect_url, "http://")
or string.starts(redirect_url, "https://") then
return redirect_url
elseif string.starts(redirect_url, "/") then
return ngx.var.scheme.."://"..ngx.var.host..redirect_url
else
return ngx.var.scheme.."://"..redirect_url
end
end
if conf["redirected_urls"] then
for url, redirect_url in pairs(conf["redirected_urls"]) do
if url == ngx.var.host..ngx.var.uri..hlp.uri_args_string()
or url == ngx.var.scheme.."://"..ngx.var.host..ngx.var.uri..hlp.uri_args_string()
or url == ngx.var.uri..hlp.uri_args_string() then
hlp.logger:debug("Requested URI is in redirected_urls")
detect_redirection(redirect_url)
if url == ngx.var.host..ngx.var.uri..uri_args_string()
or url == ngx.var.scheme.."://"..ngx.var.host..ngx.var.uri..uri_args_string()
or url == ngx.var.uri..uri_args_string() then
logger:debug("Requested URI is in redirected_urls")
redirect(convert_to_absolute_url(redirect_url))
end
end
end
if conf["redirected_regex"] then
for regex, redirect_url in pairs(conf["redirected_regex"]) do
if hlp.match(ngx.var.host..ngx.var.uri..hlp.uri_args_string(), regex)
or hlp.match(ngx.var.scheme.."://"..ngx.var.host..ngx.var.uri..hlp.uri_args_string(), regex)
or hlp.match(ngx.var.uri..hlp.uri_args_string(), regex) then
hlp.logger:debug("Requested URI is in redirected_regex")
detect_redirection(redirect_url)
if match(ngx.var.host..ngx.var.uri..uri_args_string(), regex)
or match(ngx.var.scheme.."://"..ngx.var.host..ngx.var.uri..uri_args_string(), regex)
or match(ngx.var.uri..uri_args_string(), regex) then
logger:debug("Requested URI is in redirected_regex")
redirect(convert_to_absolute_url(redirect_url))
end
end
end
--
-- 4. IDENTIFY THE RELEVANT PERMISSION
-- ###########################################################################
-- 3. IDENTIFY PERMISSION MATCHING THE REQUESTED URL
--
-- In particular, the conf is filled with permissions such as:
--
@ -78,7 +167,7 @@ end
--
-- And we find the best matching permission by trying to match the request uri
-- against all the uris rules/regexes from the conf and keep the longest matching one.
--
-- ###########################################################################
permission = nil
longest_url_match = ""
@ -96,7 +185,7 @@ for permission_name, permission_infos in pairs(conf["permissions"]) do
url = "^"..url
end
local m = hlp.match(ngx_full_url, url)
local m = match(ngx_full_url, url)
if m ~= nil and string.len(m) > string.len(longest_url_match) then
longest_url_match = m
permission = permission_infos
@ -106,33 +195,129 @@ for permission_name, permission_infos in pairs(conf["permissions"]) do
end
end
-- ###########################################################################
-- 4. CHECK USER HAS ACCESS
-- Either because the permission is set as "public: true",
-- Or because the logged-in user is listed in the "users" list of the perm
-- ###########################################################################
function element_is_in_table(element, table)
if table then
for _, el in pairs(table) do
if el == element then
return true
end
end
end
return false
end
-- Check whether a user is allowed to access a URL using the `permissions` directive
-- of the configuration file
function check_has_access(permission)
if permission == nil then
logger:debug("No permission matching request for "..ngx.var.uri)
return false
-- Public access
if authUser == nil or permission["public"] then
user = authUser or "A visitor"
logger:debug(user.." tries to access "..ngx.var.uri.." (corresponding perm: "..permission["id"]..")")
return permission["public"]
end
logger:debug("User "..authUser.." tries to access "..ngx.var.uri.." (corresponding perm: "..permission["id"]..")")
-- The user has permission to access the content if he is in the list of allowed users
if element_is_in_table(authUser, permission["users"]) then
logger:debug("User "..authUser.." can access "..ngx.var.host..ngx.var.uri..uri_args_string())
return true
else
logger:debug("User "..authUser.." cannot access "..ngx.var.uri)
return false
end
end
has_access = check_has_access(permission)
-- ###########################################################################
-- 5. CLEAR USER-PROVIDED AUTH HEADER
--
-- Which could be spoofing attempts
-- Unfortunately we can't yolo-clear them on every route because some
-- apps use legit basic auth mechanism ...
--
-- 5. APPLY PERMISSION
-- "Remote user" refers to the fact that Basic Auth headers is coupled to
-- the $remote_user var in nginx, typically used by PHP apps
-- ###########################################################################
if permission ~= nil and ngx.req.get_headers()["Authorization"] ~= nil then
perm_user_remote_user_var_in_nginx_conf = permission["use_remote_user_var_in_nginx_conf"]
if perm_user_remote_user_var_in_nginx_conf == nil or perm_user_remote_user_var_in_nginx_conf == true then
-- Ignore if not a Basic auth header
-- otherwise, we interpret this as a Auth header spoofing attempt and clear it
_, _, b64_cred = string.find(auth_header, "^Basic%s+(.+)$")
if b64_cred ~= nil then
ngx.req.clear_header("Authorization")
end
end
end
-- ###########################################################################
-- 6. EFFECTIVELY PASS OR DENY ACCESS
--
-- If the user has access (either because app is public OR logged in + authorized)
-- -> pass + possibly inject the Basic Auth header on the fly such that the app can know which user is logged in
--
-- Otherwise, the user can't access
-- -> either because not logged in at all, in that case, redirect to the portal WITH a callback url to redirect to after logging in
-- -> or because user is logged in, but has no access .. in that case just redirect to the portal
-- ###########################################################################
function set_basic_auth_header()
-- cf. https://en.wikipedia.org/wiki/Basic_access_authentication
-- authPasswordEnc is actually a string formatted as <password_enc_b64>|<iv_b64>
-- For example: ctl8kk5GevYdaA5VZ2S88Q==|yTAzCx0Gd1+MCit4EQl9lA==
-- The password is encoded using AES-256-CBC with the IV being the right-side data
-- cf. src/authenticators/ldap_ynhuser.py in YunoHost to see how the cookie is actually created
local password_enc_b64, iv_b64 = authPasswordEnc:match("([^|]+)|([^|]+)")
local password_enc = ngx.decode_base64(password_enc_b64)
local iv = ngx.decode_base64(iv_b64)
local password = cipher.new('aes-256-cbc'):decrypt(cookie_secret, iv):final(password_enc)
-- Set `Authorization` header to enable HTTP authentification
ngx.req.set_header("Authorization", "Basic "..ngx.encode_base64(
authUser..":"..password
))
end
-- 1st case : client has access
if hlp.has_access(permission) then
if has_access then
if is_logged_in then
-- If Basic Authorization header are enable for this permission,
-- add it to the response
if permission["auth_header"] then
hlp.set_basic_auth_header()
set_basic_auth_header()
end
end
return hlp.pass()
-- Pass
logger:debug("Allowing to pass through "..ngx.var.uri)
return
-- 2nd case : no access ... redirect to portal / login form
else
if is_logged_in then
return hlp.redirect(conf.portal_url)
return redirect(conf.portal_url)
else
local back_url = "https://" .. ngx.var.host .. ngx.var.uri .. hlp.uri_args_string()
return hlp.redirect(conf.portal_url.."?r="..ngx.encode_base64(back_url))
local back_url = "https://" .. ngx.var.host .. ngx.var.uri .. uri_args_string()
return redirect(conf.portal_url.."?r="..ngx.encode_base64(back_url))
end
end

3
config.lua
View file

@ -14,6 +14,9 @@ local config_persistent_attributes = nil
local conf = {}
local conf_path = "/etc/ssowat/conf.json"
function get_cookie_secret()
local conf_file = assert(io.open(conf_path, "r"), "Configuration file is missing")

218
helpers.lua
View file

@ -1,218 +0,0 @@
--
-- helpers.lua
--
-- This is a file called at every request by the `access.lua` file. It contains
-- a set of useful functions related to HTTP and LDAP.
--
module('helpers', package.seeall)
local conf = config.get_config()
local Logging = require("logging")
local jwt = require("vendor.luajwtjitsi.luajwtjitsi")
local cipher = require('openssl.cipher')
local mime = require("mime")
local rex = require("rex_pcre")
local appender = function(self, level, message)
-- Output to log file
local fp = io.open(log_file, "a")
local str = string.format("[%-6s%s] %s\n", level:upper(), os.date(), message)
fp:write(str)
fp:close()
return true
end
local logger = Logging.new(appender)
--logger:setLevel(logger.DEBUG) -- FIXME
local is_logged_in = false
function refresh_config()
conf = config.get_config()
end
function get_config()
return conf
end
function element_is_in_table(element, table)
if table then
for _, el in pairs(table) do
if el == element then
return true
end
end
end
return false
end
-- The 'match' function uses PCRE regex as default
-- If '%.' is found in the regex, we assume it's a LUA regex (legacy code)
-- 'match' returns the matched text.
function match(s, regex)
if not string.find(regex, '%%%.') then
return rex.match(s, regex)
else
return string.match(s,regex)
end
end
-- Test whether a string starts with another
function string.starts(String, Start)
if not String then
return false
end
return string.sub(String, 1, string.len(Start)) == Start
end
-- Test whether a string ends with another
function string.ends(String, End)
return End=='' or string.sub(String, -string.len(End)) == End
end
-- Convert a table of arguments to an URI string
function uri_args_string(args)
if not args then
args = ngx.req.get_uri_args()
end
String = "?"
for k,v in pairs(args) do
String = String..tostring(k).."="..tostring(v).."&"
end
return string.sub(String, 1, string.len(String) - 1)
end
-- Validate authentification
--
-- Check if the session cookies are set, and rehash server + client information
-- to match the session hash.
--
function check_authentication()
local token = ngx.var["cookie_" .. conf["cookie_name"]]
decoded, err = jwt.verify(token, "HS256", cookie_secret)
if err ~= nil then
-- FIXME : log an authentication error to be caught by fail2ban ? or should it happen somewhere else ? (check the old code)
authUser = nil
authPasswordEnc = nil
is_logged_in = false
return is_logged_in
end
-- cf. src/authenticators/ldap_ynhuser.py in YunoHost to see how the cookie is actually created
authUser = decoded["user"]
authPasswordEnc = decoded["pwd"]
is_logged_in = true
-- Gotta update authUser and is_logged_in
return is_logged_in
end
-- Extract the user password from cookie,
-- needed to create the basic auth header
function decrypt_user_password()
-- authPasswordEnc is actually a string formatted as <password_enc_b64>|<iv_b64>
-- For example: ctl8kk5GevYdaA5VZ2S88Q==|yTAzCx0Gd1+MCit4EQl9lA==
-- The password is encoded using AES-256-CBC with the IV being the right-side data
local password_enc_b64, iv_b64 = authPasswordEnc:match("([^|]+)|([^|]+)")
local password_enc = mime.unb64(password_enc_b64)
local iv = mime.unb64(iv_b64)
return cipher.new('aes-256-cbc'):decrypt(cookie_secret, iv):final(password_enc)
end
-- Check whether a user is allowed to access a URL using the `permissions` directive
-- of the configuration file
function has_access(permission, user)
user = user or authUser
if permission == nil then
logger:debug("No permission matching request for "..ngx.var.uri)
return false
end
-- Public access
if user == nil or permission["public"] then
user = user or "A visitor"
logger:debug(user.." tries to access "..ngx.var.uri.." (corresponding perm: "..permission["id"]..")")
return permission["public"]
end
logger:debug("User "..user.." tries to access "..ngx.var.uri.." (corresponding perm: "..permission["id"]..")")
-- The user has permission to access the content if he is in the list of allowed users
if element_is_in_table(user, permission["users"]) then
logger:debug("User "..user.." can access "..ngx.var.host..ngx.var.uri..uri_args_string())
return true
else
logger:debug("User "..user.." cannot access "..ngx.var.uri)
return false
end
end
-- Set the authentication headers in order to pass credentials to the
-- application underneath.
function set_basic_auth_header(user)
local user = user or authUser
-- Set `Authorization` header to enable HTTP authentification
ngx.req.set_header("Authorization", "Basic "..ngx.encode_base64(
user..":"..decrypt_user_password()
))
end
-- Set cookie and redirect (needed to properly set cookie)
function redirect(url)
logger:debug("Redirecting to "..url)
-- For security reason we don't allow to redirect onto unknown domain
-- And if `uri_args.r` contains line break, someone is probably trying to
-- pass some additional headers
-- This should cover the following cases:
-- https://malicious.domain.tld/foo/bar
-- http://malicious.domain.tld/foo/bar
-- https://malicious.domain.tld:1234/foo
-- malicious.domain.tld/foo/bar
-- (/foo/bar, in which case no need to make sure it's prefixed with https://)
if not string.starts(url, "/") and not string.starts(url, "http://") and not string.starts(url, "https://") then
url = "https://"..url
end
local is_known_domain = string.starts(url, "/")
for _, domain in ipairs(conf["domains"]) do
if is_known_domain then
break
end
-- Replace - character to %- because - is a special char for regex in lua
domain = string.gsub(domain, "%-","%%-")
is_known_domain = is_known_domain or url:match("^https?://"..domain.."/?") ~= nil
end
if string.match(url, "(.*)\n") or not is_known_domain then
logger:debug("Unauthorized redirection to "..url)
url = conf.portal_url
end
return ngx.redirect(url)
end
-- Set cookie and go on with the response (needed to properly set cookie)
function pass()
logger:debug("Allowing to pass through "..ngx.var.uri)
-- When we are in the SSOwat portal, we need a default `content-type`
if string.ends(ngx.var.uri, "/")
or string.ends(ngx.var.uri, ".html")
or string.ends(ngx.var.uri, ".htm")
then
ngx.header["Content-Type"] = "text/html"
end
return
end

39
init.lua
View file

@ -3,31 +3,52 @@
--
-- This is the initialization file of SSOwat. It is called once at the Nginx
-- server's start.
-- Consequently, all the variables declared (along with libraries and
-- Consequently, all the variables declared (along with libraries and
-- translations) in this file will be *persistent* from one HTTP request to
-- another.
--
-- Path of the configuration
conf_path = "/etc/ssowat/conf.json"
log_file = "/var/log/nginx/ssowat.log"
-- Remove prepending '@' & trailing 'init.lua'
script_path = string.sub(debug.getinfo(1).source, 2, -9)
-- Include local libs in package.path
package.path = package.path .. ";"..script_path.."?.lua"
-- Load libraries
local config = require("config")
-- Load cookie secret
-- IMPORTANT (though to be confirmed?)
-- in this context, the code is ran as root therefore we don't have to
-- add www-data in the file permissions, which could otherwise lead
-- to comprised apps running with the www-data group to read the secret file?
local config = require("config")
cookie_secret = config.get_cookie_secret()
--
-- Init logger
--
local log_file = "/var/log/nginx/ssowat.log"
-- Make sure the log file exists and we can write in it
io.popen("touch "..log_file)
io.popen("chown www-data "..log_file)
io.popen("chmod u+w "..log_file)
local Logging = require("logging")
local appender = function(self, level, message)
-- Output to log file
local fp = io.open(log_file, "a")
local str = string.format("[%-6s%s] %s\n", level:upper(), os.date(), message)
fp:write(str)
fp:close()
return true
end
logger = Logging.new(appender)
-- FIXME : how to set logging level ?
--logger:setLevel(logger.DEBUG) -- FIXME
-- You should see that in your Nginx error logs by default
ngx.log(ngx.INFO, "SSOwat ready")