TLS-SNI (Server Name Indication) is an extension of the TLS protocol that allows clients to indicate the server hostname they are attempting to connect to during the TLS handshake. This extension TLS-SNI is crucial for servers hosting multiple SSL/TLS-enabled websites web services on the same IP address.
To determine if your IoT device supports TLS-SNI, you can mock a TLS server locally and analyze the TLS handshake between the server and the client.
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Ngrok will provide a public URL ( like tcp://0666.tcp.ngrok.io:XXXXX) that forwards to your local machine's port 8883.
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Each time ngrok starts it will provide a different URL and port. In this article, we use |
Use your Ngrok URL (0666.tcp.ngrok.io:XXXXX) in place of the hostname and port when configuring your IoT device or client.
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Generate a self-signed server certificate (replace 0666.tcp.ngrok.io with your domain)
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openssl req -new -newkey rsa:2048 -days 365 -nodes -x509 -keyout server.key -out server.crt -subj "/CN=0666.tcp.ngrok.io" |
Generates a self-signed server certificate (
server.crt) and private key (server.key) valid for 365 days.The
-subj "/CN=0666.tcp.ngrok.io"option sets the Common Name (CN) in the certificate to0666.tcp.ngrok.io. Replace0666.tcp.ngrok.iowith your domain name or IP address.
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Test device connection to hostname 0666.tcp.ngrok.io port XXXXX
Testing with MQTT-CLI
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mqtt publish --topic Test --message Hello --host 0666.tcp.ngrok.io --port XXXXX --cafile server.crt --debug |
Analyzing
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TLS handshake
Connect your IoT device or client to the local TLS server. Observe the output from the OpenSSL server. Look for the ClientHello packet in the debug output, which indicates if TLS-SNI is being used and the hostname (0666.tcp.ngrok.io in this case) the client is requesting.
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