Let us learn more on the HAProxy backend SSL handshake failure with the support of our Server management support services at Bobcares.

What is a backend SSL handshake failure in HAProxy?

Backend SSL handshake failure happens in HAProxy when the SSL/TLS handshake between HAProxy and a backend server fails.

The handshake is the procedure by which HAProxy and the backend server negotiate the SSL/TLS connection parameters and create a secure connection.

Reasons for HAProxy backend SSL handshake failure

There are many reason for an SSL handshake failure to occur in HAProxy:

1. Invalid SSL certificate:

   The SSL handshake will fail if the SSL certificate supplied by the backend server is invalid, expired, or not issued by a trustworthy Certificate Authority (CA).

   This can occur if the SSL certificate has been revoked, is self-signed, or has been tampered with.
2. Incompatible SSL/TLS versions:

   The SSL handshake will fail if the SSL/TLS version used by HAProxy is incompatible with the version used by the backend server.

   The SSL handshake will fail if HAProxy is set to utilize TLS 1.2 but the backend server only supports TLS 1.0.
3. Cipher suite mismatch:

   The SSL handshake will fail if the cipher suites provided by HAProxy and the backend server are incompatible. Cipher suites are groups of encryption algorithms and key exchange protocols that work together to protect an SSL/TLS connection.

   The SSL handshake will fail if the cipher suites provided by HAProxy and the backend server do not match.
4. Network connectivity issues:

   SSL handshake failures can also arise as a result of network connectivity issues, such as firewall restrictions that prevent the connection from being established or network congestion that causes packet loss.

Resolve the Issue

To debug a backend SSL handshake failure with HAProxy, examine the error message in the HAProxy logs. The error message will include the reason for the SSL handshake failure.

We can additionally verify that the SSL certificate supplied by the backend server is legitimate and issued by a trustworthy CA.

Furthermore, we can confirm that the SSL/TLS version and cipher suites used by HAProxy and the backend server are compatible.

If the SSL handshake fails due to an invalid SSL certificate or cipher suite mismatch, we have to update the SSL certificate on the backend server or alter the cipher suite settings in HAProxy.

To repair an SSL handshake failure caused by a network connectivity issue, we may need to check the network setup.

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Conclusion

To sum up, our tech team has now shown us how to deal with the HAProxy backend SSL handshake failure.