NGINX + OpenSSL + Docker. Cannot load certificate key Permission denied. SSL:error:0200100D:system

I want to deploy a SSL certified angular app using nginx reverse proxy on docker (using docker compose). I've generated self-signed certification with openssl and made the configurations to the nginx config file. But I get error message in docker container:

[emerg] 1#1: cannot load certificate key "/etc/ssl/private/aims.key": BIO_new_file() failed (SSL: error:0200100D:system library:fopen:Permission denied:fopen('/etc/ssl/private/aims.key','r') error:2006D002:BIO routines:BIO_new_file:system lib)
nginx: [emerg] cannot load certificate key "/etc/ssl/private/aims.key": BIO_new_file() failed (SSL: error:0200100D:system library:fopen:Permission denied:fopen('/etc/ssl/private/aims.key','r') error:2006D002:BIO routines:BIO_new_file:system lib)

I've generated the key with this command from this gist:

sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout aims.key -out aims.crt -config aims.conf -passin pass:[...]

This is the docker compose:

version: "3.8"
name: aims

services:
  ...

  web-app-proxy:
    image: nginx:alpine
    container_name: web_app_proxy
    ports:
      - 443:443
      - 80:80
    volumes:
      - ./web_app_proxy.nginx:/etc/nginx/nginx.conf:ro
      - ./aims.crt:/etc/ssl/certs/aims.crt
      - ./aims.key:/etc/ssl/private/aims.key

This is the nginx config file (web-app service comes from another docker compose):

worker_processes 1;

events { worker_connections 1024; }
http {
    sendfile on;
    large_client_header_buffers 4 32k;

    upstream web-app {
        server web-app:4200;
    }

    server {
        listen 80;
        server_name web-app;

        location / {
            return 301 https://$host$request_uri;
        }
    }

    server {
        listen 443 ssl;
        server_name web-app;

        ssl_certificate /etc/ssl/certs/aims.crt;
        ssl_certificate_key /etc/ssl/private/aims.key;

        location / {
            proxy_pass         http://web-app;
            proxy_redirect     off;
            proxy_http_version 1.1;
            proxy_cache_bypass $http_upgrade;
            proxy_set_header   Upgrade $http_upgrade;
            proxy_set_header   Connection keep-alive;
            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_set_header   X-Forwarded-Host $server_name;
            proxy_buffer_size           128k;
            proxy_buffers               4 256k;
            proxy_busy_buffers_size     256k;
        }
    }
}

I've seen the problem relates with running the docker container as root, but I don't know how to do it. (Using only docker compose or compose + dockerfile, not docker run / docker exec).

If I create a dockerfile and separate from compose, when I deploy I get:

PEM_read_bio_PrivateKey() failed (SSL: error:0909006C:PEM routines:get_name:no start line:Expecting: ANY PRIVATE KEY) 

When I see aims.key encoding is ASCII, and I couldn't make a conversion as suggested in this post (even using sudo).

Regardless of your docker configuration, an nginx process will be launched as the user specified in the nginx configuration file. I believe you are getting a 'permission denied' error because you generated your certificates with sudo.

1. Check what user nginx is running as. In shell, type sudo ps aux | grep nginx
   You should see something like this: My user is nginx, yours might be www, www-data or something else.

root      776967  0.0  0.0  22332  7884 ?        Ss   Oct23   0:00 nginx: master process /usr/sbin/nginx
nginx    1262783  0.5  1.8 447744 427960 ?       S    16:18   0:00 nginx: worker process
nginx    1262784  0.5  1.8 447744 427960 ?       S    16:18   0:00 nginx: worker process
nginx    1262785  0.5  1.8 447744 427960 ?       S    16:18   0:00 nginx: worker process
nginx    1262786  0.5  1.8 447744 427960 ?       S    16:18   0:00 nginx: worker process
nginx    1262787  0.0  0.0  25864  6392 ?        S    16:18   0:00 nginx: cache manager process

Now you need to give access to cert files to your user.

sudo chown nginx:nginx /etc/ssl/certs/aims.crt
sudo chown nginx:nginx /etc/ssl/private/aims.key

Replace 'nginx' with the user from the above output

2. While this is not recommended you can tell nginx to run as root. Add user root; to the top of your nginx configuration.