We have clients who can be using anything, WindowsXP,Vista,Linux....
Currently our systems support SSLV2 and SSLV3.But, we are planning to disable both SSLV2 and SSLV3 in windows server 2008R2 in favour of TLS 1.2.
Will it have any breaking changes with the end user?I'm worried that If I disable SSLV3 ( and SSLV2) , some of the clients who use windowsXP(for example) might not be able to access my web service.
PS: Tried to find a similar question in stackoverflow, didn't find any. So, posting this as a question. :)
This is one of the scenarios where you will NOT be able to support old clients using insecure protocols and expect to have decent security.
If you have not enabled TLS 1.2 yet, do so.
Some clients do not support TLS 1.2 (e.g., older Android versions). You may need to support TLS 1.0 and 1.1 in addition to 1.2. While not ideal, it is definitely better than supporting SSL 2.0 and 3.0.
Post an announcement indicating that your web service is being upgraded to meet minimum security requirements and set a date for retiring insecure protocols.
Optionally, check your server metrics to see what protocols/ ciphers are used. Since you haven't mentioned your web server, I'm assuming it is IIS, in which case this is not easy[1][2].
Retire SSL 2.0 and SSL 3.0. There will be a few clients who will not be able to connect. Plan to have an answer ready for them. If you have clients running XP and using IE6, they have bigger issues than not being able to access your web service.
While you are at it, run your TLS configuration through an online
scanner like SSL Labs to ensure you fix any other issues.
Related
Recently, we have encountered a problem while installing one of our applications for a customer. During installation the application needs to perform some requests to our cloud service and we realised it could not establish HTTPS connection: the very TLS handshake failed. After researching a bit we found the server was a Windows Server 2008 which does not support TLS v1.2, which is the minimum required to connect to our servers. There are some workarounds (this one, for instance) but none of them worked. In addition, we cannot install any update to that windows due to customer policies.
While looking for a solution, using wireshark, we noticed that our program tried to connect using TLS v1.2 and failed, but Chrome browser was able to connect to the same cloud server using TLS v1.3, which is not even supported in Windows Server 2008. From that we deduced that Chrome is likely using its own TLS stack to establish the connection.
I am wondering that if Chrome is doing that, we should also be able to do the same. The application is developed in .Net Core and I have googled a lot looking for information on how to do this, and I've found lots of information on how to configure TLS certificates in .Net Core, but none on replacing the TLS stack with, say, OpenSSL or others. I do know this is possible in Java, so is it possible to replace the TLS stack in .Net core?
.NET Core itself doesn't let you plug in your own crypto stack.
You pointed to Bouncy Castle as an example of Java letting you use an alternate crypto stack; there's a port of Bouncy Castle to C#/.NET as well.
Their source code has a test case that demonstrates how to write a TLS client using Bouncy Castle:
https://github.com/bcgit/bc-csharp/blob/master/crypto/test/src/crypto/tls/test/TlsClientTest.cs
I have a couple questions.
If I were to use TLS1.0->1.3 Client-Side and never use SSLv2 or v3, would there be any impacts on TCP Client Handshake Compatibility?
As in, would there ever be a server that wouldn't support this change that would require me to use SSLv2/v3?
I guess what i'm asking is if TLS is backwards compatible which servers that use SSLv2/v3 or do I not understand SSL/TLS properly?
Also other way around, if I was running an OS that had no support for TLS, would I at some point end up with Protocol Issues when Handshaking an SSL Stream?
We have a legacy web application that runs in a tomcat under java 6, upgrading to 7 or 8 is infeasible as the application needs significant work to allow this and the fixes required are too large to implement in a legacy application. We now have a requirement to connect outbound (i.e. as a client) over TLS 1.2 however java 6 only supports 1.0. We use Apache as our web-server and OpenSSL for incoming connections and this happily supports TLS 1.2 etc.
Has anyone had to address a similar issue, or can you comment on the following potential work arounds:
Loopback to localhost (or otherwise redirect) and use OpenSSL to create a TLS 1.2 connection,
effectively an internal proxy
can openssl be a client?
do we need s_client?
Use our current the firewall to upgrade the connection
this would need to be selective
Obviously implementing this will depend on the firewall
Use “Bouncy Castle” (https://www.bouncycastle.org/)
Don't use openssl's s_client for this - it's slow, and intended more for debugging/testing.
Try using stunnel. It's designed for use cases like yours, and you can find plenty of example configs to get you started. You'd want to make sure to include the sslVersion = TLSv1.2 directive in your configuration to force use of TLS 1.2.
I want to enable SSL keys renegotiation in Tomcat as described in https://www.rfc-editor.org/rfc/rfc5746. Tomcat will use JSSE implementation for SSL. Which cipher suite should I use to enable the same?
Tomcat Version: 6.0.44
Java version: Java 1.8
Protocol - TLS 1.2
Meta: I'm not sure this is ontopic here, but security is on-hold. Migrate if necessary.
All Java 8 and 7, and 6 from 6u22 up, enable secure renegotiation per 5746. See the documentation. By default, it is used if the peer offers or accepts it; if the peer does not, the connection is still made but renegotiation is not done because it would/could be insecure. This can be varied two ways:
set system property sun.security.ssl.allowLegacyHelloMessages false. JSSE will not make the connection if the peer does not agree to 5746. This is not actually more secure, but it is more visibly secure to simple minded basic scanners, and people who care about simple minded basic scanners like auditors
set system property sun.security.ssl.allowUnsafeRenegotiation true. This is less secure if the application depends on peer credentials checked after a message. Since client always checks server before any data, this means if server requests (not requires) client authentication, and checks auth status after a request, it can wrongly accept a forged-prefix request.
The protocol implementation of 5746 sometimes uses a fake "ciphersuite" (officially SCSV -- Signalling Cipher Suite Value) in ClientHello. JSSE client can be configured using the "ciphersuite" name TLS_EMPTY_RENEGOTIATION_INFO_SCSV whether to use this SCSV or the extension. All servers always use the extension, and thus this configuration has no effect on JSSE server.
I would like to display a message to customers who's browser's highest level of encryption is SSLv3. Is it possible for me to target browser settings of SSLv3 and lower? Client or Server code? We will be allowing lower versions of SSL to use our site during a certain grace period. During this grace period, we would like to display a message only to those users that have browser settings of SSL3 or lower.
Not easily. The browser's supported SSL versions are not detectable until the SSL handshake is in progress, and even then only if the browser uses an SSLv2 handshake to allow dynamic version negotiation. If an unsupported version were detected, you would not be able to send a message back since the handshake failed and the connection would be closed before you could send any message. However, SSL itself has an error packet that gets sent during handshaking, and it can specify a version mismatch error.
The best you can do in your own code is support all SSL versions on the server side, let the client complete a handshake normally, and then detect which version was actually used and send back a message if the SSL version is too low.
Or, you could simply enable TLSv1 or higher only, and simply refuse to let older clients connect at all. They just would not get a nice error message unless the browser decided to detect the SSL version mismatch error and display its own pretty message about it.
Firstly, nowadays, you can generally forget about clients that don't support at least SSLv3. SSLv3 has been widely available for many years.
The TLS Client Hello message, sent when the connection is initiated by the browser, should contain the highest TLS version it supports:
client_version
The version of the TLS protocol by which the client wishes to
communicate during this session. This SHOULD be the latest
(highest valued) version supported by the client. For this
version of the specification, the version will be 3.3 (see
Appendix E for details about backward compatibility).
Appendix E is of course worth looking at.
(The Client Hello message will also contain the list of cipher suites the client supports, which is possibly relevant for the general idea of your question.)
Of course, this specification is just a "SHOULD", so a client supporting TLS 1.2 could still send a Client Hello for TLS 1.1, but what would be the point? By doing so it would have no chance ever to use TLS 1.2 anyway. It could be a preference box that is turned off, but that would effectively make it a client that doesn't support the highest version anyway. (If you want anything more subtle, you'd need to build a database of known user agents, which will be partly unreliable, and for which you'd need to analyse the full user agent string to know everything possible about the platform.)
Now, how to convey the content of the Client Hello message to your application is another matter, and depends very much on which SSL/TLS stack you use. It might not even be directly possible without modifying that SSL/TLS library or the server you're using.
This being said, you can generally get the negotiated TLS version during the current session quite easily. Since that version is the "lower of that suggested by the client in the client hello and the highest supported by the server" (i.e. "min(max(client), max(server))"). If your server supports SSLv3, TLS 1.0, TLS 1.1 and TLS 1.2, and since the latest version is TLS 1.2 anyway, what you'll get during your current connection will also be the max currently supported by the client. As long as your server supports the latest version, you should be able to know what the client supports at best from any live connection.
If you're behind Apache HTTP server's mod_ssl, you should be able to get that from the SSL_PROTOCOL environment variable. You should also be able to get the protocol from the SSLSession in Java.
(If you are willing to write a more bespoke service, you could pass further details like the cipher suites more directly to your application, like this service from Qualys SSL Labs does, although I'm not sure if it's meant to be widely available or just a test service.)
I'd have to agree with Remy about it being a bit challenging.
However, a good starting point may be to retrieve some SSL (certificate) information.
Something similar to this:
X509Certificate certChain[] =
(X509Certificate[]) req.getAttribute("javax.net.ssl.peer_certificates");
Another way of getting more information is to retrieve the cipher_suite attribute (similar to the code snippet above).
javax.net.ssl.cipher_suite
I hope this (at least) gets you closer.
Good luck.