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un-def/nginx.conf

Created May 17, 2024 17:50
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Nginx fix Location header on redirects behind reverse proxy
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nginx.conf
http {
map $http_x_forwarded_proto=$http_x_forwarded_port $redirect_port {
http=80 '';
https=443 '';
default :$http_x_forwarded_port;
}
server {
listen 8080;
location / {
proxy_pass http://unix:/tmp/nginx.sock;
proxy_set_header Host $host;
proxy_buffering off;
proxy_request_buffering off;
proxy_redirect http://$host/ $http_x_forwarded_proto://$http_x_forwarded_host$redirect_port/;
}
}
server {
listen unix:/tmp/nginx.sock;
location / {
root /data;
autoindex on;
}
}
}
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un-def commented May 17, 2024

The problem:

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un-def commented May 17, 2024

Nginx Lua Module:

header_filter_by_lua_block {
    local location = ngx.header.location
    if location and string.sub(location, 1, 1) == '/' then
        local proto = ngx.var.http_x_forwarded_proto
        local host = ngx.var.http_x_forwarded_host
        local port = ngx.var.http_x_forwarded_port
        if proto == 'http' and port == '80' or proto == 'https' and port == '443' then
            location = string.format('%s://%s%s', proto, host, location)
        else
            location = string.format('%s://%s:%s%s', proto, host, port, location)
        end
        ngx.header.location = location
    end
}

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un-def commented May 18, 2024 •
edited
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Apparently this is no longer necessary.

RFC 2616 Hypertext Transfer Protocol -- HTTP/1.1, June 1999 requires an absolute URI: 14.30 Location.

RFC 7231 Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, June 2014, which obsoletes RFC 2616, allows a relative URI: 7.1.2. Location.

RFC 9110 HTTP Semantics, June 2022, which obsoletes RFC 7231, allows a relative URI: 10.2.2. Location.

TL;DR use absolute_redirect off.

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