When high-defense IP addresses are deployed to defend against DDoS attacks, the HTTPS certificate error is a common problem. The error may be caused by conflicts between the high-defense IP traffic mechanism and the original certificate configuration, or technical errors during configuration. The specific reasons are analyzed as follows!

The problem may be that the domain name configuration does not match the certificate. Highly protected IP addresses are used to direct user traffic to protected nodes through CNAME resolution. If the domain name of the certificate does not match the resolved domain name correctly, the browser will display an error. For example, if the domain name bound to the source certificate is' www.example.com 'and the CNAME assigned by the high defense IP address is' exampleprotected.yun.com', the domain name does not match.

It is also possible that the certificate does not contain a universal domain name and cannot cover the subdomain name generated by the high-defense IP address. This can be resolved by updating the certificate domain name or adjusting the resolution configuration.

If the certificate chain (including server certificate, intermediate certificate, and root certificate) is incomplete or there is a format error, the browser cannot form a trust chain and cause an access error. For example, the correct order of certificate concatenation is server certificate → intermediate certificate → root certificate. Format incompatibility: Some high-defense IP platforms only support PEM format (starting with 'BEGIN CERTIFICATE'). If you upload PFX or DER format, you need to convert it in advance.

In this case, first check the integrity of the certificate chain: Use an online tool (such as [SSL Labs SSL Test]) to verify the integrity of the certificate chain; Also standardize the certificate format, such as converting the format through the OpenSSL command:

openssl pkcs12 in cert.pfx out cert.pem nodes

Time synchronization conflicts with the certificate validity period, which affects browser access. The validity verification of the HTTPS certificate depends on the system time. If the server or client time is not synchronized with the standard time, the ERR_CERT_DATE_INVALID error may be raised. If the time on the high-defense IP node is not synchronized to the NTP server, the certificate may be misjudged as Invalid or expired.

Synchronize server time:

Linux: 

ntpdate pool.ntp.org

Windows: Calibrate the time service through the Control panel.

Check the certificate validity period. Ensure that the certificate has not expired and the system time of the high-defense IP node is within the certificate validity period.

The encryption protocol is incompatible with the TLS version. High-security IP addresses may enable certain TLS versions by default (for example, only TLS 1.2 is supported). If the source site is configured with an earlier version (for example, TLS 1.0) or outdated encryption suite, handshakes may fail and errors may be reported. In addition, some high-security IP addresses forcibly disable weak encryption algorithms (such as RC4), causing compatibility problems if not adapted.

Unified TLS version: Configure the same TLS version on the high-defense IP console and the source server (TLS 1.2/1.3 is recommended). Updating encrypted suite: using high security suite (such as ` ECDHEECDSAAES256GCMSHA384 `), and through the tool (such as Mozilla SSL configuration generator) to generate the best configuration.

If the SSL uninstallation function of the high-security IP address is incorrectly configured (for example, the certificate private key is incorrectly associated), traffic decryption may fail. Typical errors include a mismatch between the private key and the certificate: the private key is omitted when the certificate is uploaded, or the private key file is corrupted. SSL uninstallation policy conflict: SSL uninstallation is enabled for some high-defense IP addresses by default. If HTTPS is enabled at the source site, double encryption conflicts may occur.

Check the private key: Use OpenSSL to verify that the certificate is consistent with the private key.

openssl x509 noout modulus in cert.pem | openssl md5  
openssl rsa noout modulus in private.key | openssl md5

  If the two MD5 values are the same, the matching succeeds.

Adjust the SSL uninstallation policy: Select Transparent transmission mode (the traffic is not decrypted by the high-defense IP address) or Uninstall mode (the traffic is forwarded to the source site through HTTP after the high-defense IP address decrypts) based on service requirements.

The client browser may cache old certificate information or the middleware (such as CDN or WAF) is incorrectly configured. For example, HSTS policy residue: The browser forcibly memorizes the old certificate and manually deletes HSTS records. CDN node certificate not synchronized: When the high-defense IP address and CDN are deployed in series, the CDN does not update the certificate copy in time. Users need to be guided to clear the browser cache or use private mode access; Ensure that the middleware, such as IP, CDN, and WAF, is updated to the latest certificate.

Ensure that the configuration of IP addresses and HTTPS certificates is correct, from domain name matching to certificate chain websites to protocol compatibility. Before deployment, you are advised to use a tool to check the SSL certificate status, simulate traffic tests on IP platforms, detect configuration conflicts in advance, and set up a notification rule before certificate expiration to prevent service interruption.