So here is my 'problem', I set up an FTP server thanks to vsftpd so that both login & data transfers should be encrypted.
Here is the interesting part of my vsftpd.conf file.
ssl_enable=YES
allow_anon_ssl=NO
require_ssl_reuse=NO
force_local_data_ssl=YES
force_local_logins_ssl=YES
ssl_tlsv1=YES
ssl_sslv2=YES
ssl_sslv3=YES
rsa_cert_file=/etc/vsftpd/vsftpd.pem
rsa_private_key_file=/etc/vsftpd/vsftpd.pem
ssl_ciphers=HIGH
I am using Filezilla as an FTP client, the connection is configured like this :
Protocol : FTP - File Transfer Protocol
Encryption : Require explicit FTP over TLS
Logon type: Normal
Some things to note :
Encryption : Plain FTP : does not work and I am happy with that.
(Response: 530 Non-anonymous sessions must use encryption.)
Encryption : Require implicit FTP over TLS : does not work either, the connection is refused by the server. I guess it is because I forced the SSL connection.
Now, once the (explicit) connection is established, Filezilla is showing a small lock icon at the bottom of the window saying The connection is encrypted. Click icon for details.
I wanted to make sure that the data transfers were indeed encrypted and not plain so I captured everything on my eth. card with Wireshark while downloading a file from my server to my computer.
Except that I can not find a single packet of SSL protocol, everything is TCP.
I am out of ideas on how to make sure the data transferred is encrypted, even if filezilla says so, and each time I google "vsftpd how to make sure data transfers are encrypted", the only answers I get is "ssl_enable=YES" or "Check the box Use SSL" ...
Thank you in advance for helping me !
After a little more research and especially after following the Complete walk through on http://wiki.wireshark.org/SSL, I have a better understanding of the whole thing.
I am answering to my own question hoping this will help someone someday, as long as what follows is correct...
Also writing this down is a good way for me, I think, to see if have clearly understood my problem. Any difficulties in writing this answer will prove me wrong.
First :
Typically, SSL uses TCP as its transport protocol.
SSL is wrapped in TCP, that is why I couldn't observe explicitly the SSL protocol while capturing packets.
When analyzing a TCP packet, I could only "Follow TCP stream" but not "Follow SSL stream" which mislead me into thinking the packet was not holding encrypted data. That is funny because the observable data was not human readable ... so encrypted.
To be able to decrypt it I had to provide wireshark the encryption key :
RSA keys list
This option specifies the bindings between an IP address, a port, a protocol and a decryption key.
Then, I could observe both encrypted / unencrypted data.
Also, after reading this on http://wiki.filezilla-project.org/ :
When you apply encryption to your FTP server the CPU will have to do many calculations to encrypt the data being sent and decrypt the data being received.
I simply decided to run the UNIX top command while downloading a file. I was able to observe a high CPU usage of the filezilla client process, contrary to a unencrypted data transfer. This was a second argument that confirmed the data transfered were indeed encrypted, and thus needed to be decrypted.
Related
Problem:
I'm pretty new to this TLS thing and networking in general. But i'm trying to passively listen and decode TLS packets. I find it kind of frustrating that i cant decode packets on my network on my computer. The conclusion i got to is that is impossible because how TLS works. But in mathematics if you have enough of information you can often get the value of the unknown. In this instance i guess it might be the servers key that is the missing link.
Even if it would be cool to totally decrypt packets its not my main goal. What i specifically trying to do is to know if a specific twitch stream is watched on my computer/network. So if i type in the streamers name in to the program it checks if that stream is sent to my computer and responds with a boolean.
So i want your input guys and girls. Is there any way of achieve this without doing Man in the middle?
Thoughts:
I have been thinking about this problem and i got a couple of ideas (don't laugh at the possible stupidity, I'm not always very smart but its just some things that came to my mind):
(Comparing) Using my cert to send request to the twitch api and somehow compare the response and see if they have the same encrypted payload. Then i know this specific stream is watched.
(Decoding) feed cert (public and private key), decrypted message and encrypted message to some algorithm to get server key. My theory here is that i have enough information to get the server key. But my knowledge about ssl is limited and i have not considered handshakes and such.
(Decoding) Generate training data to an ai to teach it to decode ssl packets. Generating a lot of ssl packets with different keys and feed the cert and encrypted data to the ai.
I hope you understand what I'm trying to do. English is not my native language (sorry).
(Comparing) Using my cert to send request to the twitch api and somehow compare the response and see if they have the same encrypted payload. Then i know this specific stream is watched.
Data are encrypted with a symmetric key specific for this SSL/TLS session. Also a random initialization vector is used. Thus, even transfer of exactly the same data results in different encrypted data which means no comparison of the encrypted data will help.
(Decoding) feed cert (public and private key), decrypted message and encrypted message to some algorithm to get server key. My theory here is that i have enough information to get the server key. But my knowledge about ssl is limited and i have not considered handshakes and such.
If (the obsolete) RSA key exchange is used you would need to have the servers private key to decrypt which you don't have. With Diffie-Hellman key exchange even this private key would not be sufficient, but you need to have the master secret or pre-master secret of this specific SSL/TLS session (see the TLS standards for details what this is). This secret can only be found in the TLS client and TLS server for the time the TLS session is active - which means that you will not be able to use this either for decryption unless you have access to the internals of the client, in which case you might just look directly which stream they are viewing.
(Decoding) Generate training data to an ai to teach it to decode ssl packets. Generating a lot of ssl packets with different keys and feed the cert and encrypted data to the ai.
Properly encrypted data are more or less random and have no inherent structure which can be mapped to the original data or even parts of the data. AI will not magically find such a structure too. The only possible difference it might use to distinguish streams are the size and timing of the data - but only if these are specific for a stream which I doubt. So, most likely it is impossible this way too.
I find it kind of frustrating that i cant decode packets on my network on my computer. The conclusion i got to is that is impossible because how TLS works.
Indeed this is primary purpose of TLS. If correctly implemented you should have no way of decrypting transfered data.
There are even buggy and obsolete implementation on some servers where one can exploit some vulnerabilities, but - not for Twitch and not with your knowledge level only for buggy implementation
Generally you could consider TLS secure enough to ensure traffic integrity and confidentiality.
What i specifically trying to do is to know if a specific twitch stream is watched on my computer/network.
I'd provide some options to achieve the goal, however that would introduce dangerous vulnerabilities into your computer or network. (you have been warned)
Still you can sniff out the unencrypted traffic. So you can see e. g. DNS requests (you could see what hostnames are resolved, but not specific URL).
For your computer you could install a keylogger or get the requested URL from browser before it is encrypted.
Integrity of TLS rely on certification authorities. In theory could can create your own CA certificate and make it trusted on your computer or network. That could allow you mounting a man-in-the-middle attack (posing yourself as the target server with your own keys).
Would like to write SSL Socket client server application on the same machine (both server and clients are running same machine). Should I use SSL certificate file (.pem file ) or not required.
Just I want encrypt the data before sending via socket.
Can we encrypt the data without .pem file?
Please advice me.
-Bala
SSL has two major steps:
check the identity of the peer, e.g. make sure you talk to the right one and not an imposter (e.g. man in the middle). This is done with certificates.
encrypt the connection, so that anybody listening on the wire cannot understand what's going on. Obviously encryption helps nothing if somebody is actively listening on the wire, because you failed in step#1. In this case you have no end-to-end encryption but an end-to-imposter and imposter-to-end encryption :)
Considering these arguments: do you still want to skip checking the certificate?
If you want it is doable, just look for anonymous authentication, e.g. ADH or aNULL with openssl.
I developed (in CPP) a unique protocol over HTTP and I use it to communicate with my server.
Now, I want to establish SSL connection over my proprietary protocol to transfer the data itself.
Can I do it using OpenSSL? I searched the web and all I found is something related with BIO, but I didn't understood how to use it for my needs..
Anyway, the best solution for me will be a way I can pass OpenSSL my proprietary send & receive functions so all the communication itself will go only through my functions.
TNX ahead :)
Use BIO pairs. You can find an example in the ssltest.c program, search the source for bio_pair. The basic idea is that you treat the OpenSSL engine as a black box.
There are four things your code has to do:
When you receive encrypted data over the connection to the other side, you have to write it to the SSL engine's encrypted BIO.
When the SSL engine wants to send encrypted data to the other side, you have to read it from the SSL engine's encrypted BIO and transport it to the other side.
When you have plaintext you want to encrypt and send, you have to write it to the SSL engine's plaintext BIO.
When the SSL engine has plaintext it has decrypted for you, you have to read it from the SSL engine's plaintext BIO.
OpenSSL acts purely as an engine following the SSL protocol and moving data between the two BIOs. It does all the protocol negotiation and operations for you, so long as you keep all four of these data streams moving.
One caution I can give you is this -- do not assume any special relationship between these things. For example, you might have some plaintext you want to encrypt and send, and when you write it to the SSL engine's plaintext BIO, the SSL engine might not be able to make forward progress until it receives some encrypted data from the other side. Treat the SSL engine as a black box and do all these four things whenever possible . Do not try to "look through" the SSL engine and, for example, expect that because you handed the SSL engine some encrypted data it will have necessarily plaintext for you. It might, but it might also need to send encrypted data to the other side.
One other caution: the SSL engine has only one state. It does not have a read state and a write state. (Search this thread for "the nightmare scenario" if you want the ugly details.) This is most likely to bite you if you use an SSL connection with multiple threads and expect it to behave just like a TCP connection (where the read and write sides are independent except in the case of a fatal error or connection close).
Second option - a protocol that has its own messages and uses HTTP to
pass them between the client and the server.
If you're using HTTP to pass your own messages, using OpenSSL for SSL/TLS would imply that you'd need to write your own HTTP library library too.
Instead, use an HTTP library that supports HTTPS (most do), via OpenSSL or not. Exchanging your custom messages on top of HTTPS should be fairly transparent and similar to using plain HTTP. You'd just need to configure HTTPS normally.
I have a couple questions about SSL.
What happens if someone tampers or changes the encrypted data? There are many ways in which the data being transferred can be tampered, so though the encrypted data will not make any sense to the tamperer, what would happen if he just tampers it? How would I handle such scenarios?
What will happen if a webpage is requested by a browser which does not support SSL? Or the client accessing the website is actually some kind of malware?
I am pretty new to SSL so maybe my questions are very trivial but I don't have answers to them.
The packets including the URL itself is encrypted. Modify the bytes will make the packet invalid. As far as I know it is not accepted by the server then.
If a client browser don't support your SSL protocol it can't access the website. The client get a "Insecured Request Denied Error".
SSL is to establish a secured connection. Any software, including malware, that support the protocol can start a connection. The SSL protocol "just" encrypt the communication so the packets can't be inspected outside. So your software itself need to be protected against any attacks anyway.
The tampering will be detected on arrival and the connection automatically dropped, probably resulting in a dialog box to the browser user.
I'm not aware of any browser that doesn't support SSL. Such a thing would be singularly useless.
i am trying to block ssl handshakes before the secure connection is established. So can anyone advice me how to do this. I allready have access to all data transfered to network using Winsock SPI(LSP). But how can i identify that now there is a request for SSL connecion? the data needed for establisment cant be crypted but are encoded in some way. I cant find the format anywhere.
If you have any idea about this, please let me know. I am doing this in c++.
While I think what you are doing is totally dubious, well, the best place to start is this document: The SSL Protocol - it describes the actual packet format used by SSL to envelope the encrypted data.