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openssl/ssl/statem
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Matt Caswell cfba06758e Treat all failures from EVP_DigestVerify() as a bad signature 
Prior to 72ceb6a we treated all failures from the call to
EVP_DigestVerifyFinal() as if it were a bad signature, and failures in
EVP_DigestUpdate() as an internal error. After that commit we replaced
this with the one-shot function EVP_DigestVerify() and treated a 0 return
as a bad signature and a negative return as an internal error. However,
some signature errors can be negative (e.g. according to the docs if the
form of the signature is wrong). Therefore we should treat all <=0
returns as a bad signature.

This fixes a boringssl test failure.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3756)
2017-06-23 17:23:25 +01:00
..
extensions_clnt.c Avoid compiler complaining 2017-06-21 14:36:02 -04:00
extensions_cust.c Convert existing usage of assert() to ossl_assert() in libssl 2017-05-22 14:00:43 +01:00
extensions_srvr.c Fix some bugs in the TLSv1.3 PSK code 2017-06-21 14:45:36 +01:00
extensions.c Add TLSv1.3 client side external PSK support 2017-06-21 14:45:35 +01:00
README
statem_clnt.c Treat all failures from EVP_DigestVerify() as a bad signature 2017-06-23 17:23:25 +01:00
statem_dtls.c Replace instances of OPENSSL_assert() with soft asserts in libssl 2017-05-22 14:00:19 +01:00
statem_lib.c Use EVP_PKEY_X25519, EVP_PKEY_ED25519 instead of NIDs where appropriate. 2017-06-21 14:11:01 +01:00
statem_locl.h Add TLSv1.3 server side external PSK support 2017-06-21 14:45:35 +01:00
statem_srvr.c Allow Ed25519 in TLS 1.2 2017-06-21 14:11:01 +01:00
statem.c Fix DTLS failure when used in a build which has SCTP enabled 2017-06-21 14:56:24 +01:00
statem.h Remove special case code for SCTP reneg handling 2017-04-25 11:13:39 +01:00

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 |
  |_____________________________| |_______________________________|