Define and use variable in OpenResty config file

Question

I want to define a variable and use it in the location block in OpenResty config file. Variable is defined same follow:

location /projects {
   set $my_var '';
   content_by_lua_block {
      ngx.var.my_var = "h@3265";
   }

   header_filter_by_lua '
      local val = ngx.header["x-ausername"]
      if val then
         if (val ~= "sample3")
         and (val ~= ngx.var.my_var) -- this variable does not work
         and (val ~= "sample2")
         and (val ~= "sample1")
         and (val ~= "anonymous") then
            return ngx.exit(400)
         end
      end
   ';

   proxy_pass        http://MYSERVER.LOCAL:6565;
   proxy_set_header Host $host:$server_port;
   access_log off;
}

But doesn't pars ngx.var.my_var. How can I define a variable and use it in any part of nginx.conf file?

I'm confused; you're using proxy_pass and content_by_lua at the same time, what do you want to achieve? — DarkWiiPlayer
– DarkWiiPlayer, Commented Jan 29, 2020 at 10:57
I wanna at first checked x-ausername in request header if that equal with my variable then that username permitted to login to my website. — Hamid
– Hamid, Commented Jan 30, 2020 at 6:13

Mercury · Accepted Answer · 2021-01-11 22:57:30Z

1

If you just need to set a const value to your variable - just use set $my_var 'h@3265'; directive and avoid content_by_lua_block.

It is not possible to use proxy_pass and content_by_lua_block in the same place because both are content phase directives. content_by_lua_block just ignored in your config.

If you need to use more complex Lua logic to set the variable - use set_by_lua_block

edited Jan 11, 2021 at 22:57

Mercury

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answered Jan 29, 2020 at 15:48

Alexander Altshuler

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Comments

Hamid · Accepted Answer · 2020-01-30 06:48:29Z

0

Thank you all, I changed config file into follow and that works fine.

location /projects {

   header_filter_by_lua '
      local my_var = "h%403265"             #**Note**
      local val = ngx.header["x-ausername"]
      if val then
         if (val ~= "sample3")
         and (val ~= my_var) 
         and (val ~= "sample2")
         and (val ~= "sample1")
         and (val ~= "anonymous") then
            return ngx.exit(400)
         end
      end
   ';

   proxy_pass        http://MYSERVER.LOCAL:6565;
   proxy_set_header Host $host:$server_port;
   access_log off;
}

Note: in config file for accept @ in a variable should used to percent encoding. So,@ equal to %40 (h@3265 --> h%403265).

answered Jan 30, 2020 at 6:48

Hamid

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5 Comments

DarkWiiPlayer Over a year ago

The right place for acces controll is the aptly named access_by_lua_block, not header_filter_by_lua which only runs much later.

Hamid Over a year ago

I checked access_by_lua_block but it can control through request's IP. but I need only checked x-ausername in request header and then if that equal with my variable then that username permitted to login to my website.

DarkWiiPlayer Over a year ago

The problem is that header_filter_by_lua runs at the end of the content phase, so you're wasting resources connecting to the proxy only to then throw the entire response away.

DarkWiiPlayer Over a year ago

To clarify: header_filter is for filtering response headers before they get sent to the client, not to filter the request headers before handling the request.

Hamid Over a year ago

You're right and thank you for your attention. But I wanna control on users based on username and while a user fill username and password fields I couldn't check it until authentication process completed. So as you said I should filter it on response header.

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