Matt Caswell 447cc0ad73 In a reneg use the same client_version we used last time 6 年之前
..
README f0de395950 Add a state machine README 9 年之前
extensions.c f929439f61 Rename EVP_PKEY_new_private_key()/EVP_PKEY_new_public_key() 6 年之前
extensions_clnt.c 9d5db9c9ab Assert that alpn_selected is NULL before we assign it 6 年之前
extensions_cust.c 6738bf1417 Update copyright year 6 年之前
extensions_srvr.c ded4a83d31 Ignore the status_request extension in a resumption handshake 6 年之前
statem.c d4ef4fbf46 Fix a crash in SSLfatal due to invalid enc_write_ctx 6 年之前
statem.h d4ef4fbf46 Fix a crash in SSLfatal due to invalid enc_write_ctx 6 年之前
statem_clnt.c c6d38183d6 Rewrite the X509->alert mapping code 6 年之前
statem_dtls.c cdb10bae3f Set error code on alloc failures 6 年之前
statem_lib.c 447cc0ad73 In a reneg use the same client_version we used last time 6 年之前
statem_locl.h 5d67110173 Don't calculate the Finished MAC twice 6 年之前
statem_srvr.c a682365728 Check the return from EVP_PKEY_get0_DH() 6 年之前

README

State Machine Design
====================

This file provides some guidance on the thinking behind the design of the
state machine code to aid future maintenance.

The state machine code replaces an older state machine present in OpenSSL
versions 1.0.2 and below. The new state machine has the following objectives:
- Remove duplication of state code between client and server
- Remove duplication of state code between TLS and DTLS
- Simplify transitions and bring the logic together in a single location
so that it is easier to validate
- Remove duplication of code between each of the message handling functions
- Receive a message first and then work out whether that is a valid
transition - not the other way around (the other way causes lots of issues
where we are expecting one type of message next but actually get something
else)
- Separate message flow state from handshake state (in order to better
understand each)
- message flow state = when to flush buffers; handling restarts in the
event of NBIO events; handling the common flow of steps for reading a
message and the common flow of steps for writing a message etc
- handshake state = what handshake message are we working on now
- Control complexity: only the state machine can change state: keep all
the state changes local to the state machine component

The message flow state machine is divided into a reading sub-state machine and a
writing sub-state machine. See the source comments in statem.c for a more
detailed description of the various states and transitions possible.

Conceptually the state machine component is designed as follows:

libssl
|
---------------------------|-----statem.h--------------------------------------
|
_______V____________________
| |
| statem.c |
| |
| Core state machine code |
|____________________________|
statem_locl.h ^ ^
_________| |_______
| |
_____________|____________ _____________|____________
| | | |
| statem_clnt.c | | statem_srvr.c |
| | | |
| TLS/DTLS client specific | | TLS/DTLS server specific |
| state machine code | | state machine code |
|__________________________| |__________________________|
| |_______________|__ |
| ________________| | |
| | | |
____________V_______V________ ________V______V_______________
| | | |
| statem_both.c | | statem_dtls.c |
| | | |
| Non core functions common | | Non core functions common to |
| to both servers and clients | | both DTLS servers and clients |
|_____________________________| |_______________________________|