[Pkg-openssl-devel] [Netscape/OpenSSL Cipher Forcing Bug]

[Jürgen Heil]

Hi everybody,

we do security scans on a regular basis. The mentioned OpenSSL bug has
always been listed as a Level 2 Vulnerability (Qualys) since yesterday. Now
it is listed as a level 3 Vulnerability which is not compliant to the PCI
DSS requirements.

## Following the detailed problem description from Qualys report:

# Diagnosis
Netscape's SSLv3 implementation had a bug where if a SSLv3 connection is
initially established, the first available cipher is used. If a session is
resumed, a different cipher may be chosen if it appears in the passed cipher
list before the session's current cipher. This bug can be used to change
ciphers on the server. OpenSSL contains this bug if the
SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG option is enabled during runtime.
This option was introduced for compatibility reasons. The problem arises
when different applications using OpenSSL's libssl library enable all
compatibility options including SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG,
thus enabling the bug.

# Consequence
A malicious legitimate client can enforce a ciphersuite not supported by the
server to be used for a session between the client and the server. This can
result in disclosure of sensitive information.

# Solution
This problem can be fixed by disabling the SSL OP NETSCAPE REUSE
CIPHER_CHANGE_BUG option from the options list of OpenSSL's libssl library.
This can be done by replacing the SSL OP ALL definition in the openssl/ssl.h
file with the following line:

#define SSL OP ALL (0x00000FFFL^SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG)

The library and all programs using this library need to be recompiled to
ensure that the correct OpenSSL library is used during linking.



Can anyone please tell me if this problem has been addressed in past
releases of the openssl package? Or if it is gonna be addressed in future
releases? Would the recommended solution in the Qualys report be sufficient?

I would be grateful for every tip on solving this problem!

Thank you very much!

Kind regards,

Juergen