Unlock the Mystery: Why OpenSSL s_client Hides Certs with -showcert – A Deep Dive!

Open-Source AI Gateway & Developer Portal
Introduction
OpenSSL is a robust, commercial-grade toolset for the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. It provides full-strength cryptography for data encryption and secure communication over networks such as the Internet. One of the most frequently used commands in OpenSSL is s_client
, which is used to connect to a remote server using SSL/TLS and can be used to test the SSL certificate of a server. However, it's common for users to encounter a situation where the certificates are not displayed when using the -showcerts
option. This article delves into why this happens and how to troubleshoot it.
Understanding OpenSSL s_client
Before we dive into the mystery of hidden certificates, let's understand the basics of the s_client
command. The s_client
command is used to connect to a remote server and perform SSL/TLS handshake. It can be used to test the SSL certificate of a server, verify the server's identity, and perform other SSL/TLS-related tasks.
The basic syntax of the s_client
command is as follows:
openssl s_client -connect host:port
Here, host
is the hostname of the server you want to connect to, and port
is the port number on which the server is listening for SSL connections.
The -showcerts Option
The -showcerts
option is used to display the server's certificate chain. When you use this option, the s_client
command will attempt to verify the server's certificate and display it along with any intermediate certificates.
openssl s_client -connect host:port -showcerts
However, it's not uncommon for users to find that the certificates are not displayed even when they use the -showcerts
option. This can be quite confusing, especially for those who are new to OpenSSL.
APIPark is a high-performance AI gateway that allows you to securely access the most comprehensive LLM APIs globally on the APIPark platform, including OpenAI, Anthropic, Mistral, Llama2, Google Gemini, and more.Try APIPark now! 👇👇👇
Why Certificates are Hidden
There are several reasons why certificates might be hidden when using the -showcerts
option:
1. Incomplete Certificate Chain
One of the most common reasons for hidden certificates is an incomplete certificate chain. The server's certificate chain consists of the server's certificate, intermediate certificates, and the root certificate. If any of these certificates are missing, the s_client
command will not be able to display the server's certificate.
2. Missing CA Certificate
The s_client
command relies on the CA (Certificate Authority) certificate to verify the server's certificate. If the CA certificate is not installed on the system, the s_client
command will not be able to verify the server's certificate and will therefore not display it.
3. Disabling of Certificates
In some cases, the certificates might be disabled due to system configuration or user settings. This can happen if the user has disabled the SSL/TLS module or if the certificates are not marked as trusted.
4. Version Mismatch
The version of OpenSSL being used might not be compatible with the server's certificate. This can happen if the server is using a newer version of SSL/TLS and the client is using an older version.
Troubleshooting Hidden Certificates
To troubleshoot hidden certificates, you can follow these steps:
- Check the Certificate Chain: Ensure that the certificate chain is complete. You can do this by checking the server's certificate chain using a tool like OpenSSL's
s_client
command with the-showchain
option. - Verify the CA Certificate: Ensure that the CA certificate is installed on the system. You can do this by checking the CA certificate store on the system.
- Enable Certificates: Check the system configuration to ensure that the certificates are not disabled.
- Update OpenSSL: If the version of OpenSSL is outdated, consider updating it to a newer version that is compatible with the server's certificate.
- Check for Version Mismatch: Ensure that the version of OpenSSL being used is compatible with the server's certificate.
Conclusion
Understanding why OpenSSL s_client
hides certificates can be quite challenging, but it's essential for anyone working with SSL/TLS. By following the steps outlined in this article, you can troubleshoot and resolve issues related to hidden certificates. Remember to always keep your OpenSSL version up to date and ensure that the certificate chain is complete to avoid such issues in the future.
Table: Common Causes of Hidden Certificates
Cause | Description |
---|---|
Incomplete Certificate Chain | Missing intermediate or root certificate |
Missing CA Certificate | CA certificate not installed on the system |
Disabling of Certificates | Certificates disabled due to system configuration |
Version Mismatch | Incompatible OpenSSL version with server's certificate |
FAQs
FAQ 1: Why do I see a "No peer certificate available" error when using the -showcerts
option? This error occurs when the s_client
command cannot find the server's certificate. Ensure that the certificate chain is complete and the CA certificate is installed on the system.
FAQ 2: How can I verify the server's certificate chain? You can use the s_client
command with the -showchain
option to verify the server's certificate chain. This command will display the server's certificate along with any intermediate certificates.
FAQ 3: Why is my CA certificate not recognized? Ensure that the CA certificate is installed in the correct location on your system. You can check the CA certificate store to verify its presence.
FAQ 4: Can the version of OpenSSL affect the display of certificates? Yes, the version of OpenSSL can affect the display of certificates. Ensure that the version of OpenSSL being used is compatible with the server's certificate.
FAQ 5: How can I enable the display of certificates in OpenSSL? Ensure that the -showcerts
option is used correctly when running the s_client
command. Also, check the system configuration to ensure that the certificates are not disabled.
🚀You can securely and efficiently call the OpenAI API on APIPark in just two steps:
Step 1: Deploy the APIPark AI gateway in 5 minutes.
APIPark is developed based on Golang, offering strong product performance and low development and maintenance costs. You can deploy APIPark with a single command line.
curl -sSO https://download.apipark.com/install/quick-start.sh; bash quick-start.sh

In my experience, you can see the successful deployment interface within 5 to 10 minutes. Then, you can log in to APIPark using your account.

Step 2: Call the OpenAI API.
