nginx conditional proxy pass based on request body content - nginx

Question

I am trying to configure nginx to proxy pass the request to another server, only if the $request_body variable matches on a specific regular expression.But it is not working for me.
server{
listen 80 default;
server_name www.applozic.com;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $http_host;
if ($request_body ~* (.*)appId(.*)) {
proxy_pass http://apps.applozic.com;
}
}
}
request body is::
{
"applicationId": "appId",
"authenticationTypeId": 1,
"enableEncryption": false,
"notificationMode": 0,
"deviceType": 4,
}

Answer 1

I found the solution.
I did following changes in nginx(open resty) config file
upstream algoapp {
server 127.0.0.0.1:543;
}
upstream main {
server 127.0.0.1:443;
}
location /rest/ws/login {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Url-Scheme $scheme;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header Host $http_host;
proxy_redirect off;
if ($request_method = OPTIONS ) {
proxy_pass https://127.0.0.1:543;
}
if ($request_method = POST ) {
set $upstream '';
access_by_lua '
ngx.req.read_body()
local data = ngx.req.get_body_data()
local match = ngx.re.match(ngx.var.request_body, "appId")
if match then
ngx.var.upstream = "algoapp"
else
ngx.var.upstream = "main"
end
';
proxy_pass https://$upstream;
}
}

Answer 2

As best I can tell the issue is that the variable $request_body may not have been read into memory at the time your if statement is executing.
Suggested alternatives would be to use the lua support or compile nginx with the echo modules and run echo_request_body.

Answer 3

That is not so easy when come to using integration , like some circumstances your nginx does not really allow you to do extra proxy stuff to change the whole design, then you can try nginx-if-request-body to achieve the result
http {
....
map "$uri" $forward_status {
default 100; # 100 means nothing return, continue to proxy phase
"~*.+?\.(css|js|bmp|gif|ico|jpeg|jpg|pict|png|svg|swf|tif)$" 418;
}
map "$request_body" $forward_status_by_body {
default 100;
"abc123xxx" 418;
"~*.+?\.(css|js|bmp|gif|ico|jpeg|jpg|pict|png|svg|swf|tif)$" 418;
}
server {
...
error_page 418 =200 #welcome_if_request_body;
location #welcome_if_request_body {
add_header Content-Type text/plain;
return 200 "welcome_if_request_body, you hit it";
}
location = / {
if_request_body on;
return_status_if_body_eq "ASD" 418 on;
return_status_if_body_eq "foo" 418;
return_status_if_body_eq "john" 418;
return_status_if_body_startswith "report" 418;
return_status_if_body_contains "report" 418;
return_status_if_body_regex "^[\d]+?abc" 418;
return_status_if_variable_map_to $forward_status;
return_status_if_variable_map_to $forward_status_by_body;
proxy_pass http://localhost:7777;
}
...
}
}