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In TLSv1.3 the supported groups can be negotiated each time a handshake occurs, regardless of whether we are resuming or not. We should not store the supported groups information in the session because session objects can be shared between multiple threads and we can end up with race conditions. For most users this won't be seen because, by default, we use stateless tickets in TLSv1.3 which don't get shared. However if you use SSL_OP_NO_TICKET (to get stateful tickets in TLSv1.3) then this can happen. The answer is to move the supported the supported group information into the SSL object instead. Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org> (Merged from https://github.com/openssl/openssl/pull/9162) |
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| .. | ||
| extensions_clnt.c | ||
| extensions_cust.c | ||
| extensions_srvr.c | ||
| extensions.c | ||
| README | ||
| statem_clnt.c | ||
| statem_dtls.c | ||
| statem_lib.c | ||
| statem_locl.h | ||
| statem_srvr.c | ||
| statem.c | ||
| statem.h | ||
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 |
|_____________________________| |_______________________________|