In contrast to other aspects of the Connection ID extension,
the CID-based additional data for MAC computations differs from
the non-CID case even if the CID length is 0, because it
includes the CID length.
Quoting the CID draft 04:
- Block Ciphers:
MAC(MAC_write_key, seq_num +
tls12_cid + // New input
DTLSPlaintext.version +
cid + // New input
cid_length + // New input
length_of_DTLSInnerPlaintext + // New input
DTLSInnerPlaintext.content + // New input
DTLSInnerPlaintext.real_type + // New input
DTLSInnerPlaintext.zeros // New input
)
And similar for AEAD and Encrypt-then-MAC.
While 'session hash' is currently unique, so suitable to prove that the
intended code path has been taken, it's a generic enough phrase that in the
future we might add other debug messages containing it in completely unrelated
code paths. In order to future-proof the accuracy of the test, let's use a
more specific string.
The previous comment used "TLS" as a shortcut for "TLS 1.0/1.1" which was
confusing. This partially reflected the names of the calc_verify/finished that
go ssl, tls (for 1.0/1.1) tls_shaxxx (for 1.2), but still it's clearer to be
explicit in the comment - and perhaps in the long term the function names
could be clarified instead.
This commit temporarily comments the copying of the negotiated CIDs
into the established ::mbedtls_ssl_transform in mbedtls_ssl_derive_keys()
until the CID feature has been fully implemented.
While mbedtls_ssl_decrypt_buf() and mbedtls_ssl_encrypt_buf() do
support CID-based record protection by now and can be unit tested,
the following two changes in the rest of the stack are still missing
before CID-based record protection can be integrated:
- Parsing of CIDs in incoming records.
- Allowing the new CID record content type for incoming records.
- Dealing with a change of record content type during record
decryption.
Further, since mbedtls_ssl_get_peer_cid() judges the use of CIDs by
the CID fields in the currently transforms, this change also requires
temporarily disabling some grepping for ssl_client2 / ssl_server2
debug output in ssl-opt.sh.
This commit modifies ssl_decrypt_buf() and ssl_encrypt_buf()
to include the CID into authentication data during record
protection.
It does not yet implement the new DTLSInnerPlaintext format
from https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-04
When using this function to deserialize, it's not a problem to have a session
structure as input as we'll have one around anyway (most probably freshly
deserialised).
However for tests it's convenient to be able to build a transform without
having a session structure around.
Also, removing this structure from parameters makes the function signature
more uniform, the only exception left being the ssl param at the end that's
hard to avoid for now.
Configs with no DEBUG_C are use for example in test-ref-configs.pl, which also
runs parts of compat.sh or ssl-opt.sh on them, so the added 'ssl = NULL'
statements will be exercised in those tests at least.
Make it more explicit what's used. Unfortunately, we still need ssl as a
parameter for debugging, and because calc_verify wants it as a parameter (for
all TLS versions except SSL3 it would actually only need handshake, but SSL3
also accesses session_negotiate).
It's also because of calc_verify that we can't make it const yet, but see next
commit.
This commit adds tests exercising mutually inverse pairs of
record encryption and decryption transformations for the various
transformation types allowed in TLS: Stream, CBC, and AEAD.
The hash contexts `ssl_transform->md_ctx_{enc/dec}` are not used if
only AEAD ciphersuites are enabled. This commit removes them from the
`ssl_transform` struct in this case, saving a few bytes.
This commit guards code specific to AEAD, CBC and stream cipher modes
in `ssl_derive_keys` by the respective configuration flags, analogous
to the guards that are already in place in the record decryption and
encryption functions `ssl_decrypt_buf` resp. `ssl_decrypt_buf`.
