Сайтец, действительно, странный:
curl --verbose --cert-status -I https://pay.ruszd.ru
* Rebuilt URL to: https://pay.ruszd.ru/
* Trying 95.213.237.29...
* TCP_NODELAY set
* Connected to pay.ruszd.ru (95.213.237.29) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
* CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: /etc/ssl/certs
* TLSv1.2 (OUT), TLS header, Certificate Status (22):
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384
* ALPN, server accepted to use http/1.1
* Server certificate:
* subject: OU=Domain Control Validated; OU=PositiveSSL; CN=pay.ruszd.ru
* start date: Oct 19 00:00:00 2017 GMT
* expire date: Oct 19 23:59:59 2018 GMT
* subjectAltName: host "pay.ruszd.ru" matched cert's "pay.ruszd.ru"
* issuer: C=GB; ST=Greater Manchester; L=Salford; O=COMODO CA Limited; CN=COMODO RSA Domain Validation Secure Server CA
* SSL certificate verify ok.
* No OCSP response received
* stopped the pause stream!
* Closing connection 0
* TLSv1.2 (OUT), TLS alert, Client hello (1):
curl: (91) No OCSP response received
По OCSP почему-то проверку не проходит сертификат.