Why is My Client-Side SSL Handshake Failing?

Debugging a Client-Side SSL Handshake Failure

When a client attempts to establish an SSL connection with a server, the handshake process can fail due to various reasons. To troubleshoot the cause of a handshake failure, it is essential to examine the debugging output of the underlying SSL/TLS library.

Enabling SSL/TLS Debugging

To enable SSL/TLS debugging, set the Java system property "-Djavax.net.debug=all". This will generate detailed logs during the handshake process.

Examining the Debug Output

The debug output provides insights into the handshake process, including the following:

• Keystores: Information about the keystore and truststores used for certificate validation.
• ClientHello: Details about the cipher suites and compression methods proposed by the client.
• ServerHello: Response from the server, indicating the selected cipher suite and certificate chain.
• Certificate Chain: The server's certificate chain for verifying the server's identity.
• Certificate Verification: The result of validating the server's certificate against the client's trust store.

Possible Causes of Handshake Failure:

• Incompatible Cipher Suites: The client and server may not have any supported cipher suites in common.
• Version Mismatch: The client and server may be using incompatible SSL/TLS protocols.
• Untrusted Certificate: The server's certificate may not be trusted by the client's trust store.
• Incorrect Certificate Issuance: The server's certificate may not be issued for the correct domain.

Troubleshooting Steps:

1. Inspect the Keystores: Ensure that the correct keystore and truststore are being used. Import any necessary certificates to the truststore.
2. Check for Cipher Suite Compatibility: Verify that the cipher suites supported by the client and server are compatible. Adjust them as needed in the configuration files.
3. Ensure SSL/TLS Version Compatibility: The client and server must support the same SSL/TLS protocol version. Update the appropriate settings if necessary.
4. Verify Certificate Trust: Import the necessary certificates into the trust store to ensure that the server's certificate is trusted.
5. Check Certificate Issuance: Ensure that the server's certificate is issued for the correct domain or IP address. Contact the server administrator if a discrepancy is found.

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