This command will be sent by adbd to notify the client that the
connection will be over TLS.
When client connects, it will send the CNXN packet, as usual. If the
server connection has TLS enabled, it will send the A_STLS packet
(regardless of whether auth is required). At this point, the client's
only valid response is to send a A_STLS packet. Once both sides have
exchanged the A_STLS packet, both will start the TLS handshake.
If auth is required, then the client will receive a CertificateRequest
with a list of known public keys (SHA256 hash) that it can use in its
certificate. Otherwise, the list will be empty and the client can assume
that either any key will work, or none will work.
If the handshake was successful, the server will send the CNXN packet
and the usual adb protocol is resumed over TLS. If the handshake failed,
both sides will disconnect, as there's no point to retry because the
server's known keys have already been communicated.
Bug: 111434128
Test: WIP; will add to adb_test.py/adb_device.py.
Enable wireless debugging in the Settings, then 'adb connect
<ip>:<port>'. Connection should succeed if key is in keystore. Used
wireshark to check for packet encryption.
Change-Id: I3d60647491c6c6b92297e4f628707a6457fa9420
5cf7868b7e