More and more websites are being deployed on overseas cloud servers. However, many users frequently encounter various errors when installing HTTPS certificates: certificates cannot be recognized, browsers warn of insecurity, Nginx or Apache fails to load certificate files correctly, and even redirection failures occur after deployment. HTTPS deployment seems simple, but it involves a long chain of steps; if any link in the chain is out of order, the entire site may become inaccessible.

　　Why are HTTPS deployments on overseas cloud servers more prone to errors?

　　Compared to domestic servers, the reasons for HTTPS configuration failures on overseas cloud servers mostly stem from the following differences:

　　1. Significantly simplified system images: Some overseas VPSs lack a CA root certificate package by default, and their OpenSSL module versions are outdated, causing the certificate chain to fail to verify properly.

　　2. Unstable timezone and time synchronization: HTTPS relies on the system time to verify certificate validity. If overseas servers do not enable NTP, synchronization delays or even deviations of several hours can invalidate the certificate.

　　3. Complex data center network environments: Default security policies in different countries' data centers (such as blocking port 443 and disabling ICMP) can easily prevent external access to the site.

　　4. Free certificate automatic renewal is geographically restricted: In some regions, issues such as ACME test failure and origin server verification failure occur, leading to unsuccessful certificate renewal.

　　All of this makes HTTPS configuration, seemingly simple, prone to frequent problems. Therefore, finding the root cause of the problem is crucial for successful deployment.

　　Common Errors and Causes in HTTPS Deployment on Foreign Cloud Servers

　　The following is a collection of the most common errors encountered in actual deployments, with an analysis of their causes:

　　1. Browser displays "Insecure connection" or "Invalid certificate"

　　The following prompts usually indicate a missing certificate chain or a date error:

　　NET::ERR_CERT_AUTHORITY_INVALID

　　NET::ERR_CERT_DATE_INVALID

　　SSL certificate problem: unable to get local issuer certificate

　　Causes include: intermediate certificate not installed, server time too fast/slow, incorrect certificate format (e.g., using .crt but configured as .pem)

　　2. Errors when Nginx loads the certificate

　　For example:

nginx: [emerg] SSL_CTX_use_PrivateKey_file("xxx.key") failed

　　Common causes: 1. Private key and certificate mismatch; 2. Incorrect private key and certificate format; 3. Overly strict permission settings preventing reading; 4. Certificate chain files not concatenated in order.

　　3. HTTPS access to port 443 is denied.

　　Many overseas servers have port 443 closed by default or the security group is not configured. Some cloud providers require manual opening by default, and some data centers in Japan and Europe block ICMP and certain ports by default. This results in the certificate appearing to be configured successfully, but access from the external network remains impossible.

　　4. Domain name: www and top-level domain certificate are inconsistent.

　　For example: Accessing example.com works normally, but accessing www.example.com shows an insecure error. This is often because wildcards are not configured or certificates were not applied for for both domains.

　　How to quickly diagnose HTTPS deployment failure? Complete troubleshooting process.

　　Below is a complete HTTPS troubleshooting process applicable to any overseas cloud server environment:

　　1. Check if domain name resolution is correct.

nslookup yourdomain.com
dig yourdomain.com +trace

　　Confirm that the DNS resolution is pointing to the correct IP address and that the cache has not expired.

　　2. Check if the server time is synchronized.

timedatectl status
timedatectl set-ntp true

　　If the deviation exceeds 2 minutes, the certificate may be deemed invalid.

　　3. Check if the port is open.

netstat -tlnp | grep 443
curl -Iv https://yourdomain.com

　　External network test:

telnet yourdomain.com 443

　　4. Verify that the certificate and private key match.

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

　　The two outputs must be identical.

　　5. Check if the certificate chain is complete.

　　The correct order should be:

-----BEGIN CERTIFICATE-----
Your domain certificate
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
Intermediate Certificate
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
Root certificate (optional)
-----END CERTIFICATE-----

　　6. Verify using online SSL tools

　　Tools such as SSL Labs and ForeceSSL can quickly check if the certificate chain, TLS protocol, and cipher suite are configured correctly.

　　Special Considerations for HTTPS Deployment on Overseas Cloud Servers

　　The following issues are less common when deploying domestically but are very common on overseas servers.

　　1. Firewall rule conflicts

　　Some European and Japanese data centers enable ufw or firewalld by default, requiring ports to be opened:

ufw allow 443
ufw allow OpenSSH
ufw enable

　　2. Certificate Path Permission Issues

　　Nginx must be able to read your certificate file; otherwise, it will throw a permission error.

chmod 644 /etc/nginx/ssl/*.pem

　　3. Server Image Missing CA Root Certificate

　　Some Debian/Ubuntu streamlined images are missing ca-certificates and need to be installed manually:

apt install ca-certificates
update-ca-certificates

　　4. HTTPS Deployment Still Ineffective After Using CDN

　　Inconsistent CDN TLS termination and origin server TLS can lead to the following situations: CDN HTTPS works normally, origin server HTTPS is inaccessible, and origin server access fails, resulting in a 525 handshake error. This necessitates ensuring that both the origin server certificate and CDN configuration are valid.

　　In summary: HTTPS deployment failure is not terrible; the key is to troubleshoot the problem chain. While HTTPS configuration failures are common on foreign cloud servers, they are not insurmountable. Most problems stem from non-standard basic configurations, such as missing certificate chains, closed ports, incorrect timestamps, and incorrect permissions. By following the troubleshooting process and standard configuration examples provided in this article, you can quickly identify the problem and restore HTTPS access.