Strange Nginx behavior with trailing slashes - nginx

Question

I've got a quite interesting behavior. I want to avoid trailing slashes in URL's on my site. I've put rewrite ^/(.*)/$ /$1 permanent; rule into my server block, so
https://example.com/something/,
https://example.com/something////
redirect to
https://example.com/something;
and
https://example.com/
redirects to
https://example.com
But https://example.com//// is redirected to ... https://enjoygifts.ru//// (actually don't redirected, it's 200 code). Why?
Here is my server block:
server {
listen 443 ssl;
...
... ssl directives
...
root /var/www/mysite.com;
index index.php;
server_name mysite.com;
rewrite ^/(.*)/$ /$1 permanent;
location / {
rewrite ^/.*$ /index.php last;
}
location ~ ^/index.php {
try_files $uri =404;
include /etc/nginx/fastcgi.conf;
fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
}
location ~ ^/storage/app/uploads/public { try_files $uri 404; }
...
... lot of similar location blocks
...
}

Answer 1

https://example.com doesn't really exist, the root URI is / - how it's displayed in the browser's address bar is browser dependent - some will automatically show the solitary / whereas others will remove a solitary /.
So you cannot redirect from https://example.com/ to https://example.com - it will be silently interpreted as a redirect from https://example.com/ to https://example.com/.
Nginx uses a normalized URI when evaluating location and rewrite statements, and generating the $uri variable. Multiple consecutive occurrences of / are folded into a single /.
Although the regular expression ^/(.*)/$ matches the URI //, the statement will never see it. Because Nginx has already normalised that URI to /, which does not match the regular expression.
If a root URI with multiple /s is a problem, apply a regular expression to the $request_uri variable, which contains the original URI before normalization and also includes the query string (if any).
For example:
if ($request_uri ~ "^/{2,}(\?|$)") {
return 301 /$is_args$args;
}
This can be placed inside your location / {...} block. See this caution on the use of if.