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Handshake defragmentation: reassemble incrementally

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Reassemble handshake fragments incrementally instead of all at the end. That
is, every time we receive a non-initial handshake fragment, append it to the
initial fragment. Since we only have to deal with at most two handshake
fragments at the same time, this simplifies the code (no re-parsing of a
record) and is a little more memory-efficient (no need to store one record
header per record).

This commit also fixes a bug. The previous code did not calculate offsets
correctly when records use an explicit IV, which is the case in TLS 1.2 with
CBC (encrypt-then-MAC or not), GCM and CCM encryption (i.e. all but null and
ChachaPoly). This led to the wrong data when an encrypted handshake message
was fragmented (Finished or renegotiation). The new code handles this
correctly.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2025-02-28 22:24:56 +01:00
parent 22c51b9a0b
commit cc856a2c0e
2 changed files with 105 additions and 64 deletions
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7
tests/scripts/analyze_outcomes.py
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@ -34,13 +34,6 @@ class CoverageTask(outcome_analysis.CoverageTask):
re.DOTALL)
IGNORED_TESTS = {
'handshake-generated': [
# Temporary disable Handshake defragmentation tests until mbedtls
# pr #10011 has been merged.
'Handshake defragmentation on client: len=4, TLS 1.2',
'Handshake defragmentation on client: len=5, TLS 1.2',
'Handshake defragmentation on client: len=13, TLS 1.2'
],
'ssl-opt': [
# We don't run ssl-opt.sh with Valgrind on the CI because
# it's extremely slow. We don't intend to change this.