testssl.sh/etc/client-simulation.wiresharked.md

The file client-simulation.wiresharked.txt contains client handshake data manually harvested from a network capture and displayed best with Wireshark. The content needs to be added to client-simulation.txt which other part comes from the SSLlabs client API via update_client_sim_data.pl The whole process is manual but not too difficult.

Instructions how to add a client simulation:

• Start wireshark / tcpdump at a client or router. If it's too noisy better filter for the target of your choice.
• Make sure you create a bit of encrypted traffic to your target. Attention, privacy: if you want to contribute, be aware that the ClientHello contains the target hostname (SNI).
• Make sure the client traffic is specific: For just "Android" do not use an Android browser! Be also careful with factory installed Google Apps, especially on older devices as they might come with a different TLS stack.
• Stop recording.
• If needed sort for ClientHello.
• Look for the ClientHello which matches the source IP + destination you had in mind. Check the destination hostname in the SNI extension so that you can be sure, it's the right traffic.
• Edit client-simulation.wiresharked.txt and insert a new section, preferably by copying a previous version of the client from it.
• Edit the names accordingly and short. The latter must not contain blanks.
• Retrieve handshakebytes by marking the "TLS 1.x Record Layer" --> Copy --> As a hex stream.
• For ch_ciphers mark "Cipher Suites" --> Copy --> As a hex stream, remove any leading GREASE ciphers (?a?a) and supply it to ~/utils/hexstream2cipher.sh. For consistency reasons it is preferred you remove the TLS 1.3 ciphers before which start with TLS*.
• ciphersuites are TLS 1.3 ciphersuites. You can identify them as they currently are like 0x130?. Retrieve them from above see ~/utils/hexstream2cipher.sh. They start with TLS*.
• Figure out protos and tlsvers by looking at the supported_versions TLS extension (43=0x002b). May work only with recent clients. Be careful as some do not list all TLS versions here (OpenSSL 1.1.1 listed only TLS 1.2/1.3).
• Adjust lowest_protocol and highest_protocol accordingly.
• For curves mark the "supported groups" TLS extension --> Copy --> As a hex stream, remove any leading GREASE ciphers (?a?a) and supply it to ~/utils/hexstream2curves.sh.
• Retrieve alpn by looking at the "alpn" TLS extension 16 (=0x0010).
• Review TLS extension 13 (=0x000d) "signature_algorithm" whether any SHA1 signature algorithm is listed. If not requiresSha2 is true.
• Leave maxDhBits/minDhBits and minRsaBits/maxRsaBit at -1, unless you know for sure what the client can handle.
• Figure out the services by applying a good piece of human logic. A (modern) browser is probably "HTTP", OpenSSL or Java "ANY" whereas Thunderbird supports a variety of protocols.
• When you're done copy your inserted section from client-simulation.wiresharked.txt into client-simulation.txt.
• Before submitting a PR: test it yourself! You can also watch it again via wireshark.