[openssl-dev] [openssl.org #4610] Incorrect handling of malformed Client Key Exchange messages for ECDHE_RSA key exchange

[Hubert Kario via RT]

Current 1.0.1, 1.0.2 and master don't handle malformed Client Key Exchange
messages correctly.

when a malformed message, or message with incorrect parameters is received
openssl server just closes the connection instead of sending an Alert
message

reproducer script:
https://github.com/tomato42/tlsfuzzer/blob/master/scripts/test-ecdhe-rsa-key-exchange-with-bad-messages.py

to reproduce:
openssl req -x509 -newkey rsa -keyout localhost.key -out localhost.crt -subj /CN=localhost -nodes -batch
openssl s_server -key localhost.key -cert localhost.crt -www 2>server.err >server.out &
openssl_pid=$!
git clone https://github.com/tomato42/tlsfuzzer
pushd tlsfuzzer
git clone https://github.com/tomato42/tlslite-ng .tlslite-ng
ln -s .tlslite-ng/tlslite tlslite
git clone https://github.com/warner/python-ecdsa .python-ecdsa
ln -s .python-ecdsa/ecdsa ecdsa
PYTHONPATH=. python scripts/test-ecdhe-rsa-key-exchange-with-bad-messages.py
popd
kill $openssl_pid

[Stephen Henson via RT]

This has now been addressed in master and 1.0.2.

Thanks for the report,
Steve.
--
Dr Stephen N. Henson. OpenSSL project core developer.
Commercial tech support now available see: http://www.openssl.org