59 lines
2.8 KiB
Markdown
59 lines
2.8 KiB
Markdown
NTLS State Machine Design
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This file provides some guidance on the thinking behind the design of the
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state machine code to aid future maintenance.
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The message flow state machine is divided into a reading sub-state machine and a
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writing sub-state machine. See the source comments in ntls_statem.c for a more
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detailed description of the various states and transitions possible.
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Conceptually the state machine component is designed as follows:
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libssl
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-------------------------|-----ntls_statem.h------------------------------------
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_______V____________________
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| ntls_statem.c |
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| Core state machine code |
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|____________________________|
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ntls_statem_local.h ^ ^
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_________| |_______
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_____________|____________ _____________|____________
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| ntls_statem_clnt.c | | ntls_statem_srvr.c |
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| NTLS client specific | | NTLS server specific |
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| state machine code | | state machine code |
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|__________________________| |__________________________|
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_____V___________________V___
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| ntls_statem_lib.c |
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| Non core functions common |
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| to both servers and clients |
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|_____________________________|
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Note:
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- Receive a message first and then work out whether that is a valid
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transition - not the other way around (the other way causes lots of issues
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where we are expecting one type of message next but actually get something
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else)
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- Separate message flow state from handshake state (in order to better
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understand each)
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* message flow state = when to flush buffers; handling restarts in the
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event of NBIO events; handling the common flow of steps for reading a
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message and the common flow of steps for writing a message etc
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* handshake state = what handshake message are we working on now
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- Control complexity: only the state machine can change state: keep all
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the state changes local to the state machine component
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- GB/T 38636-2020 TLCP(Transport layer cryptography protocol) and GM/T
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0024-2014 SSL VPN specification are supported.
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