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2e7dc7cd68
This is adapted from BoringSSL commit 2f87112b963. This fixes a number of bugs where the existence of bbio was leaked in the public API and broke things. - SSL_get_wbio returned the bbio during the handshake. It must always return the BIO the consumer configured. In doing so, some internal accesses of SSL_get_wbio should be switched to ssl->wbio since those want to see bbio. - The logic in SSL_set_rfd, etc. (which I doubt is quite right since SSL_set_bio's lifetime is unclear) would get confused once wbio got wrapped. Those want to compare to SSL_get_wbio. - If SSL_set_bio was called mid-handshake, bbio would get disconnected and lose state. It forgets to reattach the bbio afterwards. Unfortunately, Conscrypt does this a lot. It just never ended up calling it at a point where the bbio would cause problems. - Make more explicit the invariant that any bbio's which exist are always attached. Simplify a few things as part of that. RT#4572 Reviewed-by: Richard Levitte <levitte@openssl.org> |
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|---|---|---|
| .. | ||
| 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 |
|_____________________________| |_______________________________|