Learn how to fix the “OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to <route-address>” HAproxy error. Our HAproxy Support team is here to help you with your questions and concerns.

HAproxy Error | OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to route-address

If you have trouble with the following error message, you are in luck!

OpenSSL SSL_connect: SSL_ERROR_SYSCALL

According to our Experts, this error message signals an issue during the SSL/TLS handshake process between the client (like `curl`) and the server. This problem can arise from misconfigurations, network issues, or incompatibilities in SSL/TLS protocols.

Today, we will dive into the potential causes, common scenarios, and actionable troubleshooting steps.

An Overview:

• Common Causes of `SSL_ERROR_SYSCALL`
• 1. Network Issues or Broken Connection
• 2. SSL/TLS Handshake Failure
• 3. Misconfiguration in OpenSSL or Client Tools
• 4. Server-Side SSL Issues
• 5. File Permissions and Access Problems
• Step-by-Step Troubleshooting Guide
• Step 1: Inspect Logs for Detailed Errors
• Step 2: Validate SSL Certificate and Key
• Step 3: Check SSL/TLS Protocols and Cipher Suites
• Step 4: Test Backend Configuration (for Reverse Proxies like HAProxy)
• Step 5: Verify Network and Firewall Settings
• Step 6: Increase System Resources
• Step 7: Verify Software Versions
• Best Practices for Preventing `SSL_ERROR_SYSCALL`

Common Causes of `SSL_ERROR_SYSCALL`

1. Network Issues or Broken Connection

A dropped connection or network timeout can disrupt the SSL handshake.

It may be due to an unexpected disconnection by the server. Sometimes, network devices (firewalls, proxies) drop packets mid-handshake.

2. SSL/TLS Handshake Failure

Mismatches in supported protocols or cipher suites can cause the handshake to fail.

This may be due to unsupported SSL/TLS versions or cipher suites, expired, invalid, or missing SSL certificates, or other causes.

3. Misconfiguration in OpenSSL or Client Tools

Incorrect settings in `curl,` OpenSSL, or associated configurations can block secure communication.

This may be due to improper certificate paths or deprecated SSL protocols in the request.

4. Server-Side SSL Issues

Handshake errors will occur if the server’s SSL/TLS setup is incomplete or misconfigured.

In this scenario, it may be due to missing intermediate certificates. Sometimes, the server accepts only specific SSL protocols not supported by the client.

5. File Permissions and Access Problems

Improper permissions on certificate/key files can lead to handshake failures.

For instance, insufficient read permissions for certificate files and incorrect file ownership can cause the error.

Step-by-Step Troubleshooting Guide

Step 1: Inspect Logs for Detailed Errors

The first step is to review the HAProxy logs for more information. For more details, we can check ‘/var/log/haproxy.log.`

Run this command to find related entries:

tail -f /var/log/haproxy.log

We need to check the output for errors during the SSL handshake.

Step 2: Validate SSL Certificate and Key

Next, ensure the certificate and private key used by the server are valid:

ls -l /etc/ssl/certs/mydomain.pem

Remember to make sure the file is accessible to the user running the service.

We can test the server’s certificate chain using:

openssl s_client -connect <route-address>:443

Step 3: Check SSL/TLS Protocols and Cipher Suites

Then, verify the supported protocols and cipher suites on the client and server.

openssl s_client -connect <route-address>:443

We must ensure the client and server support a common SSL/TLS version (e.g., TLS 1.2 or 1.3).

Step 4: Test Backend Configuration (for Reverse Proxies like HAProxy)

If HAProxy forwards SSL connections to a backend, ensure the backend listens on the correct port.

Additionally, check backend SSL certificates for validity.

We can test connectivity directly to the backend with this command:

openssl s_client -connect backendserver:443

Step 5: Verify Network and Firewall Settings

At this point, we have to make sure ports like `443` are open and not blocked by firewalls:

telnet <route-address> 443

Also, investigate intermediate devices (proxies, firewalls) that may disrupt SSL.

Step 6: Increase System Resources

Then, check file descriptor limits, which may affect SSL handshakes:

ulimit -n

We can increase limits if necessary:

haproxy soft nofile 100000
haproxy hard nofile 100000


Step 7: Verify Software Versions

Now, ensure `curl,` OpenSSL, and HAProxy (if applicable) are updated:

curl --version
openssl version
haproxy -v


Older versions may lack support for modern SSL/TLS features.

Best Practices for Preventing `SSL_ERROR_SYSCALL`

 

• Regularly update OpenSSL and related libraries to ensure compatibility with modern protocols.
• Validate SSL certificates for expiry, proper chaining, and supported encryption.
• Monitor server logs for recurring issues and act on configuration mismatches.
• Use tools like `ssllabs.com` to test our server’s SSL/TLS setup.

[Need assistance with a different issue? Our team is available 24/7.]

Conclusion

By systematically identifying the root cause and applying these fixes, we can effectively resolve the `SSL_ERROR_SYSCALL` issue and ensure smooth SSL/TLS communication.

In brief, our Support Experts demonstrated how to fix the “OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to <route-address>” HAproxy error.