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mirror of https://github.com/openssl/openssl.git synced 2024-12-27 06:21:43 +08:00
openssl/ssl/statem
Richard Levitte e92519b5a6 SSL: refactor ossl_statem_fatal() and SSLfatal()
ossl_statem_fatal() is refactored to be an extended ERR_set_error(),
and SSLfatal() is refactored to work like ERR_raise().  We also add
SSLfatal_data() to work like ERR_raise_data().

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/13316)
2020-11-11 12:12:23 +01:00
..
extensions_clnt.c Rename EVP_PKEY_set1_tls_encodedpoint to EVP_PKEY_set1_encoded_public_key 2020-10-20 16:39:41 +01:00
extensions_cust.c
extensions_srvr.c Rename EVP_PKEY_set1_tls_encodedpoint to EVP_PKEY_set1_encoded_public_key 2020-10-20 16:39:41 +01:00
extensions.c Run the withlibctx.pl script 2020-10-01 09:25:20 +01:00
README.md
statem_clnt.c Convert all {NAME}err() in ssl/ to their corresponding ERR_raise() call 2020-11-11 12:12:11 +01:00
statem_dtls.c Convert all {NAME}err() in ssl/ to their corresponding ERR_raise() call 2020-11-11 12:12:11 +01:00
statem_lib.c Convert all {NAME}err() in ssl/ to their corresponding ERR_raise() call 2020-11-11 12:12:11 +01:00
statem_local.h
statem_srvr.c Ensure we raise SSLfatal on error 2020-10-26 09:07:20 -07:00
statem.c SSL: refactor ossl_statem_fatal() and SSLfatal() 2020-11-11 12:12:23 +01:00
statem.h SSL: refactor ossl_statem_fatal() and SSLfatal() 2020-11-11 12:12:23 +01:00

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_local.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 |
|_____________________________| |_______________________________|