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?
Related
My server running on PC uses LibreSSL
My client running on board uses wolfSSL
Will handshake be success?
Different TLS implementations can work together because they all implement a standardized protocol. This does not mean that it will work in all cases, i.e. common problems like no shared ciphers, invalid certificates etc can happen both when connecting with different TLS stacks but also when connecting with same TLS stacks.
In other words, there are no inherent handshake problems caused by using different TLS stacks. But other problems might make the handshake fail.
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.
I am trying to connect a client to a secure (SSL/TLS) IMAP server. The client code cannot handle SSL/TLS correctly, so I am trying to see if a proxy server can be used in the middle. I was thinking something like the following:
IMAP Client <------- Plain Text Requests -------> Proxy <------- SSL/TLS Requests -------> SSL/TLS protected IMAP server.
I think this is possible but I am curious on what products can be used for the proxy? And, is this a normal deployment option?
Thanks much,
Ash
Use stunnel. With it you can do direct TLS (i.e. imaps, port 993) and also TLS upgrade of a plain IMAP connection (port 143) using the STARTTLS command. See the documentation for more details.
This is insane. An obvious fix is to find out why your client software cannot handle TLS. Deploying proxies or standalone tunnels makes little sense.
Seriously, if your "client" cannot even establish a TLS connection, it's either severely misconfigured, has damaged installation, or so bad that it won't reliably work even after you deploy this bandaid.
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.
1 question about Stunnel. I would like to use Stunnel as a FIX (Financial Information eXchange) gateway for internet, to support both SSL and non-SSL connection. Is Stunnel able to do without any encryption? I just had a try with plain socket but it looked Stunnel rejected the connection saying 'invalid protocol' or something.
It's possible to use SSL/TLS without encryption using cipher suites with null encryption (e.g. TLS_RSA_WITH_NULL_SHA), which are normally disabled by default, but could be set via the ciphers option of Stunnel. However, you would still be using SSL/TLS, which isn't what you seem to be looking for.
It looks like you're more generally looking for what's usually called a TCP bouncer. You should be able to find a number of implementations around.