OS: CentOS 7

SW: NginX

Existing stuff

  • dhparam.pem
  • mydomain.com.crt
  • mydomain.com.csr
  • mydomain.com.key


I'm trying to create a client verification by creating client certificates and then authenticate one servers requests with NginX to my destination server. However I constantly get the 400 Bad Request - No required SSL certificate was sent error message. What am I doing wrong? Here is what I did:

  • openssl genrsa -out client.key 4096

  • openssl req -new -key client.key -out client.csr

  • openssl x509 -req -days 365 -sha256 -in client.csr -CA mydomain.com.crt -CAkey client.key -set_serial 2 -out client.crt

Every command runs successfully, however, the error stays. Also in my NginX, on the destination server, I have:

ssl_certificate         /etc/nginx/ssl/mydomain.com.crt;
ssl_certificate_key     /etc/nginx/ssl/mydomain.com.key;
ssl_client_certificate  /etc/nginx/ssl/mydomain.com.crt;

NGINX Configuration:

server {
    listen 80;
    listen 443 ssl;

    ssl_dhparam /etc/nginx/ssl/dhparam.pem;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers on;

    add_header Strict-Transport-Security "max-age=63072000; includeSubdomains; preload";

    ssl_certificate         /etc/nginx/ssl/mydomain.com.crt;
    ssl_certificate_key     /etc/nginx/ssl/mydomain.com.key;
    ssl_client_certificate  /etc/nginx/ssl/client.crt;

    ssl_verify_client optional;

    server_name uploads.mydomain.com;
    root /var/www/html/com.mydomain.uploads/public;

    error_log /var/log/nginx/mydomain.com/error.log;
    access_log /var/log/nginx/mydomain.com/access.log main;

    index index.php;

    rewrite ^/index\.php?(.*)$ /$1 permanent;

    location / {
        try_files $uri @rewrite;

    location @rewrite {
        rewrite ^(.*)$ /index.php/$1 last;

    location ~ ^/index.php(/|$) {
        fastcgi_pass unix:/var/run/php-fpm/uploads.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param SSL_CLIENT_VERIFY    $ssl_client_verify;
        fastcgi_param SSL_CLIENT_S_DN       $ssl_client_s_dn;
  • Can you show us the rest of configuration file? Especially the server block.
    – dave
    Jun 27 '18 at 8:07
  • 2
    The error message says that the client does not sent a client certificate. Since you don't show how you've added such a client certificate to the client I assume that you did not do it at all. In this case it is no wonder that the server complains about a missing certificate from the client. Jun 27 '18 at 8:09

It was a very stupid mistake and now I'm ashamed of myself.

I though that the website certificates are the same as the CA ones. So now I've created new ca.key and ca.crt files and signed the clients certificate with them and voila. :(

ssl_certificate /etc/nginx/ssl/mydomain.com.crt; ssl_certificate_key /etc/nginx/ssl/mydomain.com.key; ssl_client_certificate /etc/nginx/ssl/ca.crt;

So all the commands in order:

Create CA key and cert:

  • openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout nginx-selfsigned.key -out nginx-selfsigned.crt

Create client key and CSR

  • openssl genrsa -out client.key 2048
  • openssl req -new -key client.key -out client.csr

Sign client CSR with CA files

  • openssl x509 -req -days 3652 -sha256 -in client.csr -CA nginx-selfsigned.crt -CAkey nginx-selfsigned.key -set_serial 2 -out client.crt

OPTIONAL: Convert client.crt to a base64 encoded pem including the private key

  • openssl pkcs12 -export -clcerts -in client.crt -inkey client.key -out client.p12
  • openssl pkcs12 -in client.p12 -out client.pem -nodes

HUGE NOTE! The Organization name of the CA files and Client files CANNOT BE EQUAL! Otherwise it will break and fail to authenticate.

I hope I've helped others who also as dumb as I was.

  • 2
    Hey, +1 from me on both question and answer, because you had the inquisitiveness to keep searching and find an answer, the courtesy to write it up, and the honesty to hold your hands up to your blunder.
    – MadHatter
    Jun 28 '18 at 12:38
  • Cheers Buddy ! :)
    – Bert
    Jun 28 '18 at 12:50

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