ssl_get_next_record() may pend fatal alerts in response to receiving
invalid records. Previously, however, those were never actually sent
because there was no code-path checking for pending alerts.
This commit adds a call to ssl_send_pending_fatal_alert() after
the invocation of ssl_get_next_record() to fix this.
This function is often called when there's already an error code to handle,
and one of the reasons to introduce the pending of alerts was to _not_ have
another potential error code to take care of. Reflect this by making `void`
the return type of `mbedtls_ssl_pend_fatal_alert()`.
Modelled after the config-checking header from session s11n.
The list of relevant config flags was established by manually checking the
fields serialized in the format, and which config.h flags they depend on.
This probably deserves double-checking by reviewers.
Since the type of cid_len is unsigned but shorter than int, it gets
"promoted" to int (which is also the type of the result), unless we make the
other operand an unsigned int which then forces the expression to unsigned int
as well.
The code wants timer callbacks to be set (checked in fetch_input()), and can't
easily check whether we're using nbio, so it seems easier to require the
callbacks to be always set rather than only with nbio as was previously done.
context_buf was never free()d. Moreover, since we want to free it on error
paths as well, and even properly zeroize it in order to demonstrate good
memory hygiene, we need to make it and its length main()-scoped.
Previously it was missing reset in case 1, and in case 2 the code was never
executed as the option value was reset to 0.
Tighten checking of return values of save(NULL, 0) now that it works.
Also, improve the printed output as well as the comments.
I checked manually that everything now works and fail in the expected way:
save, reset-or-reinit and load all succeed, but the subsequent read or write
fails.
The number of meaning of the flags will be determined later, when handling the
relevant struct members. For now three bytes are reserved as an example, but
this number may change later.
This mainly follows the design document (saving all fields marked "saved" in
the main structure and the transform sub-structure) with two exceptions:
- things related to renegotiation are excluded here (there weren't quite in
the design document as the possibility of allowing renegotiation was still
on the table, which is no longer is) - also, ssl.secure_renegotiation (which
is not guarded by MBEDTLS_SSL_RENEGOTIATION because it's used in initial
handshakes even with renegotiation disabled) is still excluded, as we don't
need it after the handshake.
- things related to Connection ID are added, as they weren't present at the
time the design document was written.
The exact format of the header (value of the bitflag indicating compile-time
options, whether and how to merge it with the serialized session header) will
be determined later.
Enforce restrictions indicated in the documentation.
This allows to make some simplifying assumptions (no need to worry about
saving IVs for CBC in TLS < 1.1, nor about saving handshake data) and
guarantees that all values marked as "forced" in the design document have the
intended values and can be skipped when serialising.
Some of the "forced" values are not checked because their value is a
consequence of other checks (for example, session_negotiated == NULL outside
handshakes). We do however check that session and transform are not NULL (even
if that's also a consequence of the initial handshake being over) as we're
going to dereference them and static analyzers may appreciate the info.
At that point, the timer might not yet be configured.
The timer is reset at the following occasions:
- when it is initially configured through
mbedtls_ssl_set_timer_cb() or
mbedtls_ssl_set_timer_cb_cx()
- when a session is reset in mbedtls_ssl_session_reset()
- when a handshake finishes via mbedtls_ssl_handshake_wrap()
