[Nginx]オレオレCA認証局を利用したクライアント証明書通信をする手順。

openssl genrsa -out client.key 2048

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

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:JP
State or Province Name (full name) [Some-State]:Tokyo
Locality Name (eg, city) []:Minato-ku
Organization Name (eg, company) [Internet Widgits Pty Ltd]:TodoONada
Organizational Unit Name (eg, section) []:IT
Common Name (e.g. server FQDN or YOUR name) []:libproc.com
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

openssl ca -out client.crt -in client.csr

Using configuration from /usr/lib/ssl/openssl.cnf
Enter pass phrase for /etc/ssl/CA/private/cakey.pem:
Check that the request matches the signature
Signature ok
Certificate Details:
        Serial Number: 1 (0x1)
        Validity
            Not Before: Sep  7 10:27:52 2021 GMT
            Not After : Sep  7 10:27:52 2022 GMT
        Subject:
            countryName               = JP
            stateOrProvinceName       = Tokyo
            organizationName          = TodoONada
            organizationalUnitName    = IT
            commonName                = *.libproc
        X509v3 extensions:
            X509v3 Basic Constraints:
                CA:FALSE
            Netscape Comment:
                OpenSSL Generated Certificate
            X509v3 Subject Key Identifier:
                FF:11:11:22:33:44:55:66:AA:BB:7F:2E:18:7D:B7:71:B3:DB:C3:C2
            X509v3 Authority Key Identifier:
                keyid:FF:11:11:22:33:44:55:66:AA:BB:7F:2E:18:7D:B7:71:B3:DB:C3:C2

Certificate is to be certified until Sep  7 10:27:52 2022 GMT (365 days)
Sign the certificate? [y/n]:y

1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

openssl pkcs12 -export -out client.pfx -inkey client.key -in client.crt -certfile /etc/ssl/CA/cacert.pem

server {
        ...
        ssl_client_certificate "/etc/ssl/CA/cacert.pem";
        ssl_verify_client on;
        ...