When a client connects to a server using SSL/TLS, the server presents its digital certificate to the client. The client checks the certificate for validity, authenticity, and trustworthiness. If any issue is found in the certificate, it generates a certificate error. The certificate error could occur due to one or more reasons such as:
1. The certificate is expired.
2. The certificate is not issued by a recognized certification authority.
3. The hostname on the certificate does not match the hostname in the URL.
4. The certificate is self-signed and not trusted by the client.
When the certificate error occurs, SSL/TLS handles it based on the error type. The following are how SSL/TLS handles certificate errors:
1. Expired or invalid certificate: If the client finds that the certificate has expired or is not valid, it terminates the SSL/TLS connection.
1. Untrusted certification authority: If the client finds that the certificate is not issued by a recognized certification authority, it terminates the SSL/TLS connection.
1. Mismatched hostnames: If the client finds that the hostname on the certificate does not match the hostname in the URL, it terminates the SSL/TLS connection.
1. Self-signed certificate: If the certificate is self-signed and not trusted by the client, the client may present an error message to the user asking if they want to continue connecting to the website. If the user chooses to continue, the SSL/TLS connection will proceed, but the user’s data may be vulnerable to interception or attack.
In summary, SSL/TLS handles certificate errors based on the severity of the issue. If the certificate is invalid, expired or the hostnames do not match, SSL/TLS terminates the connection. If the certificate is self-signed and not trusted, the user is warned, and they can decide whether to proceed or not.
