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Juliusz Sosinowicz
b0fdaa2a6d
RFC 8446 section 8 requires any server instance to accept 0-RTT for a
given ClientHello at most once. Prior to this change wolfSSL's behaviour
diverged from that requirement in several ways:
* ctx->maxEarlyDataSz defaulted to MAX_EARLY_DATA_SZ whenever the
library was built with WOLFSSL_EARLY_DATA, so servers auto-
advertised 0-RTT in NewSessionTicket without the application
asking. RFC 8446 E.5 says 0-RTT MUST NOT be enabled unless
specifically requested.
* The post-accept eviction is compiled out under NO_SESSION_CACHE,
so builds without the cache accepted 0-RTT with no replay defence.
* Stateless self-encrypted tickets do not carry a session ID on the
stateless DoClientTicket decrypt path, so wolfSSL_SSL_CTX_remove_
session could not locate them to evict.
* wolfSSL_SSL_CTX_remove_session always returned 0 on success
regardless of whether the session was actually in the cache,
diverging from OpenSSL's SSL_CTX_remove_session (1 on success,
0 on not-found).
Changes:
* src/internal.c: ctx->maxEarlyDataSz defaults to 0; applications
must opt in with wolfSSL_CTX_set_max_early_data.
* src/tls13.c: #error when WOLFSSL_EARLY_DATA is built with
HAVE_SESSION_TICKET and NO_SESSION_CACHE. Escape hatch
WOLFSSL_EARLY_DATA_NO_ANTI_REPLAY for deployments that take
application-layer responsibility.
* wolfssl/internal.h: imply WOLFSSL_TICKET_HAVE_ID from
WOLFSSL_EARLY_DATA so stateless-ticket issuance populates the
cache under an ID that eviction can find.
* src/ssl_sess.c: wolfSSL_SSL_CTX_remove_session returns 1 when the
session was found (internal-cache hit, or ctx->rem_sess_cb fired
for an external cache), 0 otherwise. Matches OpenSSL semantics.
* src/tls13.c: the 0-RTT acceptance condition in CheckPreSharedKeys
now calls wolfSSL_SSL_CTX_remove_session and checks its return:
the eviction is the check. If the session was in the cache, 0-RTT
is accepted and the single-use requirement is satisfied. If not,
the early_data extension is rejected through the normal path so
the record layer correctly skips in-flight 0-RTT records.
WOLFSSL_MSG at each rejection site.
* doc/dox_comments/header_files/ssl.h: document runtime opt-in.
* tests: four new tests —
test_tls13_0rtt_default_off (fails without default-to-0 fix),
test_tls13_0rtt_stateless_replay (fails without TICKET_HAVE_ID
implication and remove_session gate),
test_tls13_remove_session_return (fails without return-value fix),
test_tls13_0rtt_ext_cache_eviction (fails without ext-cache
counts-as-found fix).
test_tls13_early_data explicitly opts in via
wolfSSL_CTX_set_max_early_data.
tests/api.c: two SSL_CTX_remove_session == 0 assertions updated
to == 1.