I captured with wireshark a TLSv1.3 handshake established between a client and server that both support TLSv1.3. I know that the certificate is being sent in an encrypted form but i can't find any field that indicate that here we find the encrypted certificate. Any help please?
In TLS 1.3 servers send their certificates encrypted.
In TLS 1.3 client and server exchange keys at the very beginning: client sends its choice in ClientHello, and the server sends its key_share in ServerHello. Everything after ServerHello is encrypted.
It differs drastically from SSL/TLS prior to TLS 1.3, where key exchange happened AFTER authentication. In SSL and TLS 1-1.2 certificates were sent as plain text.
If you open RFC 8446 on Page 11, you will see the message exchange diagram. Please find the server-side {Certificate*} message. The notation {*} means:
asterisk (*) indicates this is an optional message,
braces {} indicate that
messages protected using keys derived from a [sender]_handshake_traffic_secret
More formally RFC 8446 section 4.4 specifies:
As discussed in Section 2, TLS generally uses a common set of
messages for authentication, key confirmation, and handshake
integrity: Certificate, CertificateVerify, and Finished. ...
These messages are encrypted under keys derived from the
[sender]_handshake_traffic_secret.
Related
Is there any way that I can create a proof of a file downloaded using https? With proof I mean a cryptographic record of some sort that links the contents of a file to a site at a certain time. If I understand TLS correctly, the server certificate is only used as a basis to establish a session key that is known to both parties, so each request is not signed but just encrypted for transfer. Any ideas if this can be done and if so how?
In HTTPS the certificate is only used for authentication and with the obsolete RSA key exchange also for key exchange. Application data are only protected against modification by some man in the middle but they are not signed by the sender. While a HTTP server could be explicitly implemented to sign and timestamp the content, one can not enforce such operation against an arbitrary existing server.
For more see
Where in a TLS connection can I get the signature of the content sent by the server?
Why does HTTPS not support non-repudiation?
How to prove some server sent some file over HTTPS
Proving authenticity of data accessed over TLS by an untrusted third party
CocoaMQTT client is running on iOS15 with the SSL enabled as shown in this example. The cert_key.p12 file was merged from the client.crt and client.key files signed by the same (self-created) CA that was used for the MQTT server/broker certificate generation. The MQTT broker is configured to require client's certificate and use its CN as the username. The handshake does not go well - the log complains about the unknown certificate:
New connection from 192.168.1.87 on port 8883.
OpenSSL Error[0]: error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown
Based on the above error research, the broker does not like the client's certificate, right? In fact, looking at the wireshark's log, it seems like the client does not send the certificate to the server. Is that something I need to enable in the App configuration? Does the Swift CocoaMQTT package even support this feature (provide the cert to the broker)?
EDIT:
I tried running a client with the same cert/key with paho mqtt implemented in python, which also allows to provide the client with the CA certificate, and everything runs ok:
Trying using the same client's cert/key in CocoaMQTT implemented in iOS15 shows the MQTT broker log error message as above and the fatal alert shows up the the wireshark log:
Initially, I thought that the sever did not like (or did not receive) the client's certificate, but that fatal alert package destination is port 8883. So now I tend to believe that it's the client, who does not like the server's certificate. This is expected if the client uses the pool of official CAs to verify the certificate instead of recognizing that its own certificate was issued by the same CA as the server's one. This is further confirmed by setting the allowUntrustCACertificate = true and seems like the handshake is suspended and no more communication occurs:
There's also a debug message on the client's side:
Call the SSL/TLS manually validating function
So it looks like the client will not continue the communication until this validation process occurs. As #Brits mentioned in his comment, there's a callback to validate the cert manually but it is implemented as a part of the delegate. I do see that there's a method mqtt.didReceiveTrust which I assume should be used for cert validation, and I wish to use the closures approach as stated on the README page as giving an example for the didReceiveMessage methond:
Now you can use closures instead of CocoaMQTTDelegate:
mqtt.didReceiveMessage = { mqtt, message, id in
print("Message received in topic \(message.topic) with payload \(message.string!)")
}
With a weak understanding of Swift Closures, I am not able to figure out how to make that function all, so the question now becomes: how to convert that function from the delegate definition into the closure?
Is it possible in SSL/TLS handshake where client only send its certificate. Server need not to send any certificate ?As of now in one way handshake only server send its certificate to client.
As i am aware of that in this scenario server needs to maintain all clients root certificate(if diffrent).This is not practical.If possible what are the security concerns.
Here is context under Use of SSL with socket programming in C# or C++
Thanks for help!
Yes, it is possible to use SSL/TLS without a server certificate. See https://security.stackexchange.com/questions/38589/can-https-server-configured-without-a-server-certificate
You need software that supports at least one of the anonymous cipher suites SSL/TLS supports, such as TLS_DH_anon_WITH_AES_128_CBC_SHA256. Per the OpenSSL Diffie Hellman wiki entry:
Anonymous Diffie-Hellman uses Diffie-Hellman, but without authentication. Because the keys used in the exchange are not
authenticated, the protocol is susceptible to Man-in-the-Middle
attacks. Note: if you use this scheme, a call to
SSL_get_peer_certificate will return NULL because you have selected an
anonymous protocol. This is the only time SSL_get_peer_certificate
is allowed to return NULL under normal circumstances.
You should not use Anonymous Diffie-Hellman. You can prohibit its use
in your code by using "!ADH" in your call to SSL_set_cipher_list.
Note that support for such cipher suites and configurations in most available SSL/TLS software is either non-existent or very limited, as such configurations are vulnerable to man-in-the-middle attacks - one of the very things SSL/TLS is used to prevent. You'd have to compile your own OpenSSL code, for example.
Unless you control the software at both ends of your communication channel(s), effectively there's no way to implement such a system.
And there's no real reason to implement such a system as it's not secure at all.
But you can do it with a lot of effort.
Server Certificate which contains the public key part of its key pair is must. The client may decide to overlook the authenticity of the certificate( Its bad!) but the TLS handshake requires the public key for the generation of pre-master-secret. So no way you can prevent server from sending the certificate.
Server if it wishes can request client for its certificate. This is for authenticating the client.
We are using the SendGrid API to send sensitive email to an Office365 hosted email address. Both services use opportunistic TLS by default, which would in turn make you believe that the email is always going to be encrypted with TLS.
What I'm trying to establish is this enough to assure a client that the TLS email encryption is guaranteed? or do we need to setup enforced TLS in SendGrid? (the con of the later is we then need a mechanism in place to check for emails that have been blocked in the very unlikely event TLS encryption could not be negotiated, which in turn is additional work for us).
Here is some of the information we have been looking at:
https://sendgrid.com/docs/Classroom/Basics/Email_Infrastructure/does_sendgrid_support_end_to_end_tls.html
https://support.office.com/en-us/article/How-Exchange-Online-uses-TLS-to-secure-email-connections-in-Office-365-4cde0cda-3430-4dc0-b489-f2c0736c929f
Thanks
As long as the Office365 server uses opportunistic TLS, and has a valid SSL certificate at all times (preferably issued by a certificate authority, not self signed), then the emails should always get delivered using a safe TLS connection.
If the Office365 server would have an issue at some point accepting TLS encrypted emails, then you should see a deferred event in your SendGrid account, and then the email will be delivered to the server with no encryption.
Cheers!
Currently I am using Net::LDAP::Server to setup my server but it is not secure enough.
Is there any module or method so that I can setup a LDAP server over TLS or other secure connection?
I just found many information about how to connect to a secure ldap server, but cant found how to setup a secure ldap server.
Can anyone give some advices?
How does an LDAPS connection work
LDAPS is an unofficial protocol. It is to LDAP what HTTPS is to HTTP, namely the exact same protocol (but in this case LDAPv2 or LDAPv3) running over a secured SSL ("Secure Socket Layer") connection to port 636 (by default).
Not all servers will be configured to listen for LDAPS connections, but if they do, it will commonly be on a different port from the normal plain text LDAP port.
Using LDAPS can potentially solve the vulnerabilities described above, but you should be aware that simply "using" SSL is not a magic bullet that automatically makes your system "secure".
First of all, LDAPS can solve the problem of verifying that you are connected to the correct server. When the client and server connect, they perform a special SSL 'handshake', part of which involves the server and client exchanging cryptographic keys, which are described using X.509 certificates. If the client wishes to confirm that it is connected to the correct server, all it needs to do is verify the server's certificate which is sent in the handshake. This is done in two ways:
check that the certificate is signed (trusted) by someone that you trust, and that the certificate hasn't been revoked. For instance, the server's certificate may have been signed by Verisign (www.verisign.com), and you decide that you want to trust Verisign to sign legitimate certificates.
check that the least-significant cn RDN in the server's certificate's DN is the fully-qualified hostname of the hostname that you connected to when creating the LDAPS object. For example if the server is , then the RDN to check is cn=ldap.example.com.
You can do this by using the cafile and capath options when creating a Net::LDAPS object, and by setting the verify option to 'require'.
To prevent hackers 'sniffing' passwords and other information on your connection, you also have to make sure the encryption algorithm used by the SSL connection is good enough. This is also something that gets decided by the SSL handshake - if the client and server cannot agree on an acceptable algorithm the connection is not made.
Net::LDAPS will by default use all the algorithms built into your copy of OpenSSL, except for ones considered to use "low" strength encryption, and those using export strength encryption. You can override this when you create the Net::LDAPS object using the 'ciphers' option.
Once you've made the secure connection, you should also check that the encryption algorithm that is actually being used is one that you find acceptable. Broken servers have been observed in the field which 'fail over' and give you an unencrypted connection, so you ought to check for that.
How does LDAP and TLS work
SSL is a good solution to many network security problems, but it is not a standard. The IETF corrected some defects in the SSL mechanism and published a standard called RFC 2246 which describes TLS ("Transport Layer Security"), which is simply a cleaned up and standardized version of SSL.
You can only use TLS with an LDAPv3 server. That is because the standard (RFC 2830) for LDAP and TLS requires that the normal LDAP connection (ie., on port 389) can be switched on demand from plain text into a TLS connection. The switching mechanism uses a special extended LDAP operation, and since these are not legal in LDAPv2, you can only switch to TLS on an LDAPv3 connection.
So the way you use TLS with LDAPv3 is that you create your normal LDAPv3 connection using Net::LDAP::new(), and then you perform the switch using Net::LDAP::start_tls(). The start_tls() method takes pretty much the same arguments as Net::LDAPS::new(), so check above for details.
Well, perhaps LDAPS is not an RFC but to say it is not a standard or secure is certainly a stretch.
LDAPS is supported by ALL LDAP Server Vendors.
LDAPS is at least as secure as HTTPS.
As with ALL SSL (or TLS) the security weak points are how the certificates are handled.
Certainly LDAPS is more supported by LDAP server vendors and clients than is TLS. Active Directory as one example, does not support TLS. Querying the rootDSE for the supportedExtention 1.3.6.1.4.1.1466.20037 will (should) show if TLS is supported on any particular LDAP server.
We have some examples at:
http://ldapwiki.willeke.com/wiki/Perl%20LDAP%20Samples.