-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Hermes,
On 11/26/12 3:36 PM, Hermes Flying wrote:
> Hi, I am running Tomcat 5.35 and I got a report that it is
> vulnerable to SSL client renegotiation DoS.
>
> You notein your docs that this is not a Tomcat issue per se, but
> JSSE issue. Please note that allowUnsafeLegacyRenegotiation is set
> to false. Looking into the source code I see the following:
>
> public void handshake(Socket sock) throws IOException {
>
> ((SSLSocket)sock).startHandshake();
>
> if(!allowUnsafeLegacyRenegotiation) { // disable all ciphers,
> avoiding any subsequent handshake
> ((SSLSocket)sock).setEnabledCipherSuites(new String[0]); } }
>
> Also looking into Tomcat6/7 source code I see that the only
> difference is to check for existence of
> TLS_EMPTY_RENEGOTIATION_INFO_SCSV in JSSE.
>
> But other than that the logic is the same. So I can only assume
> that upgrading to Tomcat 6 would not solve my problem. Since I have
> verified via debugging also that allowUnsafeLegacyRenegotiation is
> indeed false, why do I get reports on SSL client renegotiation
> vulnerability?
Many vulnerability scanners blindly check version numbers and then
just regurgitate information found in CVE reports. It's much easier
than actually probing for the actual vulnerability, and it generates
huge numbers of false positives.
It's very possible that your server is actually not vulnerable but
that you version number has been flagged as /potentially/ vulnerable.
What tool/service are you using to scan for vulnerabilities?
> I see in your notes (http://tomcat.apache.org/security-5.html)
> that: Requires JRE that supports RFC 5746. For Oracle JRE that is
> known to be 6u22 or later.
Allowing "safe" renegotiation requires this. Disabling unsafe
renegotiation does not require 6u22 or later -- because of the trick
of disabling all ciphers once the initial SSL handshake has been
completed.
> But as I understand the code, even if JRE does not support the RFC
> you still disable the handshake with your "hack" to set no enable
> ciphers
+1
> Is this a Java/JSSE problem? What can I do? Can you please help
> me?
I think you might want to put this into the "prove the vulnerability
exists" pile and go back to the tool/service for verification.
- -chris
-----BEGIN PGP SIGNATURE-----
Version: GnuPG/MacGPG2 v2.0.17 (Darwin)
Comment: GPGTools - http://gpgtools.org
Comment: Using GnuPG with undefined - http://www.enigmail.net/
iEYEARECAAYFAlC1TLAACgkQ9CaO5/Lv0PB+vgCggfXX4KmAy+1NE+D2KFYMqDpo
g6cAoKuv7u1RMVcyAIOIWTyLiNO19l/A
=dUeN
-----END PGP SIGNATURE-----
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org
