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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 24.0.3): 24.0.3
Operating system and version (eg, Ubuntu 20.04): Ubuntu Server 20.04
Apache or nginx version (eg, Apache 2.4.25): nginx 1.19
PHP version (eg, 7.4): 7.4
The issue you are facing:
I have the following scenario:
Nextcloud installation on one server in a dedicated subdomain cloud.mydomain.tld
Docker container Nginx Reverse Proxy “proxy” in a dedicated docker network “frontend” IP = IP_PROXY
Handover to Nginx docker container “cloud_web” in a dedicated docker network “backend”, IP_CLOUD-WEB
Docker container “cloud_app” in the same docker network "backend, IP_CLOUD_APP
This setup is working fine.
Now I would like to setup fail2ban.
I believe when I enter a wrong password in Nextcloud login then the REMOTE_IP will be shown in “nextcloud.log”, but I get always only the IP_PROXY and not the REMOTE_IP in the log statements.
From my understanding this is the prerequisite to go ahead with fail2bain installation.
In proxy Nginx access.log I can identifiy the correct REMOTE_IP:
REMOTE_IP - - [05/Aug/2022:15:33:07 +0000] "GET /js/dist/doclinks.js?v=5.2.0 HTTP/1.1" 200 3739 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:103.0) Gecko/20100101 Firefox/103.0" "-"
In cloud_web Nginx access.log I can identifiy also the correct REMOTE_IP:
IP_PROXY - - [05/Aug/2022:16:23:48 +0000] "GET /svg/core/logo/logo?color=ffffff&v=1 HTTP/1.0" 200 818 "https://cloud.mydomain.tld/apps/theming/styles?v=0" "Mozilla/5.0 (X
11; Linux x86_64; rv:103.0) Gecko/20100101 Firefox/103.0" "REMOTE_IP"
In Firefox Dev Debugger (SHIFT-CTRL-I) I can identify also on Nextcloud login page the header entry “X-Forwarded_For” with the correct REMOTE_IP:
...
GET https://cloud.mydomain.tld/login?clear=1
[HTTP/1.1 200 OK 138ms]
...
X-Forwarded_For: REMOTE_IP
…
I already tried all constellation of IPs for trusted_domains etc. But REMOTE_IP is not shown in Nextcloud.log!
What’s is wrong here? Thanks for a helping hand.
kkarsten62
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Login
- Review Nextcloud.log
The output of your Nextcloud log in Admin > Logging:
...
{"reqId":"9yS58epEKNhFLpFD67Se","level":2,"time":"2022-08-06T23:03:23+02:00","remoteAddr":"IP_PROXY","user":"--","app":"no app in context","method":"POST","url":"/index.php",
"message":"Login failed: username (Remote IP: IP_PROXY)","userAgent":"Mozilla/5.0 (X11; Linux x86_64; rv:103.0) Gecko/20100101 Firefox/103.0","version":"24.0.3.2","data":[]}
...
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
'trusted_domains' =>
array (
0 => 'IP_CLOUD-WEB',
1 => 'IP_PROXY',
),
'overwritehost' => 'cloud.mydomain.tld',
'overwritewebroot' => '/',
'overwriteprotocol' => 'https',
'logtimezone' => 'Europe/Berlin',
'forwarded_for_headers' => array(0 => 'HTTP_X_FORWARDED_FOR',),
The output of your Apache/nginx/system log in /var/log/____:
Nginx proxy conf
...
client_max_body_size 200M;
location / {
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_pass http://cloud_web.frontend:port;
proxy_read_timeout 90;
proxy_buffering off;
proxy_request_buffering off;
...
Nginx cloud_web conf
...
add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";
add_header X-Robots-Tag none;
add_header X-Download-Options noopen;
add_header X-Permitted-Cross-Domain-Policies none;
add_header X-Forwarded-For $http_x_forwarded_for;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Host $http_host;
...
