[openssl-dev] [openssl.org #4080] Malformed Client Hello messages are accepted (session_id length)

[Hubert Kario via RT]

The server does not abort connection upon receiving a Client Hello 
message with malformed session_id field.

Affects 1.0.1, 1.0.2 and master.

In SSLv3 and all versions of TLS (e.g. RFC 5246), the SessionID is 
defined as

      opaque SessionID<0..32>;

that means, that any SessionID longer than 32 bytes creates an 
incorrectly formatted Client Hello message, and as such, should be 
rejected.

Reproducer:
openssl req -x509 -newkey rsa -keyout localhost.key -out localhost.crt -
nodes -batch
openssl s_server -key localhost.key -cert localhost.crt

In different console:
pip install --pre tlslite-ng
git clone https://github.com/tomato42/tlsfuzzer.git
cd tlsfuzzer
PYTHONPATH=. python scripts/test-invalid-session-id.py
-- 
Regards,
Hubert Kario
Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic
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