While running Paypal IPN simulator test you may receive below error:
IPN was not sent, and the handshake was not verified. Review your information.
Running client certificate verification with openssl client seems to be okay:
openssl s_client -connect api-3t.sandbox.paypal.com:443 -showcerts -CApath /etc/ssl/certs/
Solution: On Cloudflare I set the minimum SSL to TLS 1.2
For Apache 2.4 on CentOS:
cd /etc/yum.repos.d && wget https://repo.codeit.guru/codeit.el`rpm -q --qf "%{VERSION}" $(rpm -q --whatprovides redhat-release)`.repo
yum -y update httpd mod_ssl
# add below to vhost file:
SSLProtocol -all +TLSv1.3 +TLSv1.2
SSLHonorCipherOrder on
SSLOpenSSLConfCmd Curves secp384r1:X25519:prime256v1
SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:ECDHE-RSA-AES128-SHA:DHE-RSA-AES128-GCM-SHA256:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4Result:
