Download CA Certificate & Server SSL via OpenSSL: A Practical Guide

When managing SSL/TLS certificates, sometimes you need to get your hands on the actual certificate files directly from a server or source. This might be necessary for troubleshooting chain issues, verifying installation, inspecting details, or installing missing intermediate certificates. While Certificate Authorities (CAs) and resellers like sslrepo.com provide certificate files upon issuance, the powerful OpenSSL command-line tool offers a way to retrieve certificates directly from a live server.

This guide will show you how to use OpenSSL commands to Download CA Certificate files (specifically intermediate and root certificates presented by a server) and how to download ssl certificate openssl commands can retrieve the primary server certificate itself. Understanding these techniques is valuable for administrators and developers working with HTTPS configurations.

Key Takeaways

• OpenSSL: A versatile command-line toolkit for SSL/TLS tasks, including retrieving certificates from remote servers.
• Server Certificate Download: Use openssl s_client piped to openssl x509 to download the specific end-entity (server) SSL certificate.
• CA Certificate Download (Chain): Use openssl s_client -showcerts to download the entire certificate chain presented by the server (server cert + intermediates, sometimes root).
• Purpose: Useful for troubleshooting installation issues (missing intermediates), verifying certificate details, or obtaining public certificates for specific needs.
• Public Data Only: These methods only download public certificate information; they cannot retrieve private keys.
• Verification: Downloading is often the first step; further verification using OpenSSL flags or online tools is recommended.

Understanding Why You Might Download Certificates

Normally, you receive certificate files from your CA or reseller (like sslrepo.com) after purchase and validation. However, you might need to download them directly using OpenSSL in scenarios like:

1. Troubleshooting Chain Issues: If browsers report trust errors, the server might not be sending the necessary intermediate CA certificates. Downloading the chain helps identify missing links.
2. Installing Missing Intermediates: If you identify a missing intermediate, downloading it allows you to install it correctly on your server.
3. Verification & Auditing: Checking the exact certificate and chain a server is presenting for security audits or configuration verification.
4. Extracting Public Keys: Obtaining the public key from a certificate for specific application needs.
5. Learning & Analysis: Understanding the certificate structure and chain presented by different servers.

How to Download CA Certificate (Chain) using OpenSSL

This command connects to the server and displays the entire certificate chain it sends during the TLS handshake.

bash
openssl s_client -connect yourdomain.com:443 -servername yourdomain.com -showcerts </dev/null

Explanation:

• openssl s_client: Initiates a client connection.
• -connect yourdomain.com:443: Specifies the target server hostname and port (replace yourdomain.com).
• -servername yourdomain.com: Crucial for SNI. Ensures you get the certificate for the correct hostname if the server hosts multiple sites on one IP.
• -showcerts: This flag tells s_client to print all certificates presented by the server (server cert + intermediates).
• </dev/null: (or echo | before the command, or use Ctrl+D if interactive) Prevents s_client from waiting for standard input, making it exit after getting the certificates.

Output:

The output will contain several blocks of text, each starting with -----BEGIN CERTIFICATE----- and ending with -----END CERTIFICATE-----. These are the certificates in PEM format.

• Certificate 0 (s:/… i:/…): Usually the server’s end-entity certificate.
• Certificate 1 (s:/… i:/…): Usually the first intermediate CA certificate.
• Certificate 2, 3… (s:/… i:/…): Subsequent intermediate CA certificates, potentially up to the root (though the root itself isn’t always sent or needed for installation). The s: indicates the Subject (who the cert is for) and i: indicates the Issuer (who signed it).

Saving the CA Certificates:

To save a specific intermediate certificate:

1. Identify the correct block(s) in the output (usually certificate 1, 2, etc. – not certificate 0). Look at the Issuer and Subject fields to understand the chain.
2. Copy the entire block, including the -----BEGIN... and -----END... lines.
3. Paste the copied text into a new file using a plain text editor.
4. Save the file with a descriptive name and a .crt or .pem extension (e.g., intermediate_ca.crt).

Note: While this downloads the intermediates presented by the server, the most reliable source for the correct intermediate certificates required for your specific server certificate is always the issuing Certificate Authority’s official website/repository or the files provided by your reseller (like sslrepo.com).

How to Download SSL Certificate (Server Cert) using OpenSSL

If you only need the server’s main SSL certificate (not the entire chain):

openssl s_client -connect yourdomain.com:443 -servername yourdomain.com </dev/null | openssl x509 -outform pem

Explanation:

• The first part (openssl s_client... </dev/null) connects and retrieves the certificates as before.
• |: Pipes the output to the next command.
• openssl x509: The utility for processing X.509 certificates. By default, when receiving input from s_client, it processes only the first (end-entity/server) certificate.
• -outform pem: Specifies the output format should be PEM (this is often the default but explicit is good).

Saving the Server Certificate:

You can redirect the output directly to a file:

openssl s_client -connect yourdomain.com:443 -servername yourdomain.com </dev/null | openssl x509 -outform pem > server_certificate.crt

This will save the server’s SSL certificate into the file server_certificate.crt.

Important Considerations

• Public Information Only: These OpenSSL commands only retrieve publicly available certificate information. You cannot download the server’s private key using these methods. Private keys should never leave the server.
• Verification: Downloading the certificate is just the first step. Use other OpenSSL commands (openssl verify, openssl x509 -noout -text, etc.) or online SSL checker tools to verify the certificate’s details, validity, and chain integrity after installation or for troubleshooting.
• Purpose: Know why you are downloading the certificate. If it’s to fix a chain issue, ensure you download the correct intermediate certificate(s) and install them properly on your server (e.g., in the “Intermediate Certification Authorities” store on Windows/IIS, or via configuration directives in Apache/Nginx).

Conclusion

OpenSSL provides powerful command-line capabilities to directly download ssl certificate openssl commands can retrieve, both the end-entity server certificate and the intermediate/root certificates presented in the chain. Whether you need to Download CA Certificate files to troubleshoot trust issues or grab a server certificate for inspection, openssl s_client combined with openssl x509 offers a flexible solution. Always remember that these methods retrieve public data only and that the official source for CA intermediate certificates is the issuing CA itself or your trusted provider like sslrepo.com.

Need a new SSL certificate or looking to renew? Find trusted certificates from leading CAs at sslrepo.com.

Frequently Asked Questions (FAQ)

Q1: What is the difference between openssl s_client -showcerts and piping s_client to openssl x509?
A: -showcerts displays all certificates sent by the server (server cert + intermediates). Piping to openssl x509 typically processes and displays only the first certificate received (the server/end-entity certificate).

Q2: How do I save the certificates downloaded using OpenSSL?
A: For -showcerts, copy the relevant -----BEGIN...END----- blocks into text files (.crt or .pem). When piping to openssl x509, you can redirect the command’s output directly to a file (e.g., > mycert.crt).

Q3: Is it safe to download certificates using OpenSSL?
A: Yes, downloading public certificates is safe. You are retrieving publicly available information that servers present during the TLS handshake. You are not accessing any private or sensitive server data like private keys.

Q4: Why would I need to download intermediate CA certificates?
A: The most common reason is that your web server isn’t configured to send them along with your server certificate. Browsers need these intermediates to complete the chain of trust. Downloading them allows you to install them correctly on your server.

Q5: Can I download the website’s private key using OpenSSL s_client?
A: Absolutely not. The private key is never transmitted during the TLS handshake and cannot be retrieved using these methods. It must remain securely stored on the server.

Q6: Where should I get the official intermediate certificates for my SSL certificate?
A: The best source is the official website or certificate repository of the Certificate Authority (CA) that issued your certificate, or from the resources provided by your SSL vendor (like sslrepo.com).