Group based HTTP basic authentication using Nginx and MySQL with help of Lua
Recently I moved from Apache to Nginx on one of my servers due to increase in traffic. But I was using HTTP Basic authentication with group based authorization on Apache in this manner:
<Location /foo>
AuthType Basic
AuthName Restricted
AuthBasicProvider file
AuthUserFile /etc/apache2/htpasswd
AuthGroupFile /etc/apache2/groups
Require group somegroup
</Location>
However, there’s no AuthGroupFile in nginx. But LUA, a programming language is supported in nginx. So here’s how I used LUA and MySQL for achieving this:
location ~ ^/restricted {
set $user_group 'somegroup';
access_by_lua_file '/etc/nginx/authenticate.lua';
}
Now the real magic comes in the authenticate.lua script, I’m posting the code below which is available in Github as well:
-- basic configuration of the script
local cookie_domain = ".yourdomain.com"
local db_username = "dbuser"
local db_password = "dbpasswrod"
local db_socket = "/tmp/mysql.sock"
local db_name = "dbname"
-- end configuration
local session = require "resty.session".open{ cookie = { domain = cookie_domain } }
local remote_password
if ngx.var.http_authorization then
local tmp = ngx.var.http_authorization
tmp = tmp:sub(tmp:find(' ')+1)
tmp = ngx.decode_base64(tmp)
remote_password = tmp:sub(tmp:find(':')+1)
end
function authentication_prompt()
session.data.valid_user = false
session.data.user_group = nil
session:save()
ngx.header.www_authenticate = 'Basic realm="Restricted"'
ngx.exit(401)
end
function authenticate(user, password, group)
local mysql = require "resty.mysql"
local db, err, errno, sqlstate, res, ok
db = mysql:new()
if not db then
ngx.log(ngx.ERR, "Failed to create mysql object")
ngx.exit(500)
end
db:set_timeout(2000)
ok, err, errno, sqlstate = db:connect{
path = db_socket,
database = db_name,
user = db_username,
password = db_password
}
if not ok then
ngx.log(ngx.ERR, "Unable to connect to database: ", err, ": ", errno, " ", sqlstate)
ngx.exit(500)
end
user = ngx.quote_sql_str(user)
password = ngx.quote_sql_str(password)
local query = "select 1 from http_users where username = %s and password = SHA2(%s, 224) and (find_in_set('superadmin', groups) > 0 or find_in_set('%s', groups) > 0)"
query = string.format(query, user, password, group);
res, err, errno, sqlstate = db:query(query)
if res and res[1] then
session.data.valid_user = true
session.data.user_group = group
session:save()
else
authentication_prompt()
end
end
if session.present and (session.data.valid_user and session.data.user_group == ngx.var.user_group) then
return
elseif ngx.var.remote_user and remote_password then
authenticate(ngx.var.remote_user, remote_password, ngx.var.user_group)
else
authentication_prompt()
end
The group authentication script looks for users and groups in a table called http_users. Since this is a script you can modify the way users are searched for in the database or change the database altogether!
The lua modules required to run this script are: resty.mysql, resty.session, resty.string and cjson. Though the passwords are stored in the database as a SHA224 hash, the comparison of the password is done by the database itself. I did not convert the password to hash before sending it to database, so you may want to review this in case you are using remote database. I’m using local database over Unix socket so it doesn’t matter much.
The table and triggers I have for the same:
CREATE TABLE `http_users` (
`username` varchar(15) NOT NULL DEFAULT '',
`password` varchar(56) NOT NULL DEFAULT '',
`groups` set('superadmin','group1','group2','group3','group3') NOT NULL DEFAULT '',
PRIMARY KEY (`username`),
UNIQUE KEY `password` (`password`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
DELIMITER $
CREATE trigger http_user_ins before insert on http_users for each row
begin
SET NEW.password = SHA2(NEW.password, 224);
end;
DELIMITER $
DELIMITER $
CREATE trigger http_user_upd before update on http_users for each row
begin
if LENGTH(NEW.password) != 56 then
SET NEW.password = SHA2(NEW.password, 224);
end if;
end;
DELIMITER $
The triggers are required to convert the INSERT or UPDATE statements into SHA224. I’m using MySQL’s SET data type to ensure that the group value is fixed. The same values can be used by Nginx in $user_group variable before specifying the access_by_lua_file directive.
NileshGR 
Hey mate, you never started the session but rather opened. According to the author open never starts the session.
https://stackoverflow.com/questions/42720543/nginx-lua-session-does-not-start-using-module-lua-resty-session
I tried this code but the session value is not retained.
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This is interesting. I need to check why it’s been working good for me.
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