To get around the problem of an SSL-terminating load balancer (it doesn't forward client certs to the application servers), our ISP has configured our environment such that client certificates are forwarded within the HTTP headers to the real servers (as X-Client-Cert).
I will be authenticating clients with a PIN mapped to the serial number of the certificate they've been issued with. But how do I get at the certificate from the custom header?
I assume you know that you can get the certificate data using
String s = Request.Headers["X-Client-Cert"];
The question is now in which format the certificate is added to the header. I would assume that it is encoded in Base64.
byte[] certdata = Convert.FromBase64String(s);
Then you can create the certificate object from it:
X509Certificate cert = new X509Certificate(certdata);
Depending on if the load balancer checks the client certificate for validity (and if it has been singed by the correct root CA) or not you have to check the validity of the certificate yourself or not.
Afterwards you can just read the serial number via cert.GetSerialNumber();
Related
In the TLS handshake process, the Certificate Verify message will follow the Client Key Exchange message after the server requested a client certificate. The Certificate Verify contains a digital signature computed over all previous handshake messages including the type and length fields of the handshake messages. This process allows the client to prove that it owns the private key of the client certificate it sends to the server.
The idea came from a practical problem. There is an mTLS enabled server that conducts different action policies based on the client certificate received, for example, different welcome pages for different client certificates. If a layer-7 reverse proxy service like the load balancer is placed in front of the proxied server which also requires decrypting the TLS traffic. The proxied server can only get the client certificate information from the HTTP header (for example, set proxy_set_header with $ssl_client_cert variable in NGINX) which requires modifying the logic of the server.
A simple but very troublesome solution is the reverse proxy service stores all the client certificates and their private keys. The reverse proxy service will use the same client certificate it received during the mTLS handshake process to establish the mTLS connection with the proxied server.
Since the reverse proxy service can choose whether to trust the client or not with its own implementation, it is possible to forge the Certificate Verify message by asking the client to send a second Certificate Verify signature when the proxied server needs the reverse proxy service to do so (I know it's like a man-in-the-middle attack)?
I want to read the client certificate passed by the user and extract the user information out of the certificate and pass add it as header to every subsequent request made by NGINX using reverse proxy (using proxy pass).
How can I read the client cert information on NGINX ?
I could find any quick answer on google. Most probably the answer lies somewhere in RFC docs on http or https however I just couldn't (too time consuming ) get those information.
So here is the question:
Is the content of a webpage served through HTTP signed digitally by the server ? Same question for HTTPS.
If yes, how does it work correctly when using a proxy ? In my opinion the proxy could tamper the data, sign the tampered data with it's own private key, and claim that the corresponding proxy's public key is actually the genuine public key of the original server ? I am assuming that the client can't check the original server's public key, because there is a proxy which could lie.
I am sorry if this is a dump question and easy searchable on the internet, but every answer I found posed some doubts to me.
Thanks for your help :)
Content sent via HTTPS is encrypted, clients verify the authenticity of the host certificates with whom they are communicating. The server uses a TLS/SSL key/certificate which is signed by certificate authorities (CA) The CAs make sure that they only sign the certificates of the rightful owners of a domain. The certificates of the CAs them-self are installed in you browser/OS. By using these pre-installed certificates, the browser can check if the key used by the remote server is signed by a trusted CA.
A man-in-the-middle does not have the original key, nor another key signed by a CA for the domain in question. Therefore, a man-in-the-middle cannot modify the content without breaking HTTPS.
On the other hand, if you want to use a proxy to cache requests, the proxy can terminate the HTTPS connections. This means the proxy has its own connection to the server and verifies the certificates. In order to secure the connection to the client, the proxy acts as a CA and uses a HTTPS connection with self-signed certificates. To avoid that your browser complains about an insecure connection, you need to install the proxies own CA certificate.
HTTP content is not signed and can be tampered with.
Edit 2018-06-15:
I wasn't really precise with the term "signed" here. The server does not actually sign the content it sends. This means if you store the responses from the server, you cannot prove that they came from that server, in other words: standard TLS dose not provide non-repudiation. However, the authenticity of the server is established during the handshake. The client encrypts a master-key with the servers public key. Only servers in possession of the private key can decrypt the master-key and derive session keys from them.
CAs, on the other hand, actually sign the certificates. A CA cannot validly deny that it signed for the authenticity of a server certificate.
What i want to do is to parse the method-type of a HTTPS message using wireshark.
I saw that for a HTTP message I see that for a 'GET' message, on the first row I see 'Get ...'.
Now I want to check the same for a HTTPS message, but I dont see any field flagging the method-type.
What am I missing?
HTTPS is HTTP inside a SSL tunnel. So you need to first decrypt the data of the SSL tunnel before you could find out which method is used. Unless you can get access to the keys of the encryption there is no way to decode the content and get at the HTTP traffic.
HTTPS is HTTP over SSL. The entire HTTP request is encrypted as SSL record and that is what the server receives. And server/client reach this stage only on setting up the SSL tunnel successfully. You need to invoke appropriate methods to unwrap the SSL layer and get the application data.
I assume you are trying to decode it from Wireshark. You will need to posses the server's private key to get the data out. Wireshark has the means to load the key. It shall then display the decrypted data in the capture. - http://support.citrix.com/article/CTX116557
when we use https.........for example to send login credentials(https://example.com?username=aaaa&password=aaaa123). HTTPS encrypts the data using SSL certificate. So the url will be encrypted string. I am giving two requests with the same url(https://example.com?username=aaaa&password=aaaa123). On every request the url will be encrypted. Will the encrypted url of the first request be same as the encrypted url of the second request? Is the SSL certificate going to be different everytime btween client and server?
Thanks,
Iqbal
Will the encrypted url of the first request be same as the encrypted url of the second request?
The URL will be the same, because you said so. If you're asking whether the encryption of the URL will be different, the question is meaningless. It's impossible for anyone to tell, because the entire request is encrypted, so it is impossible to pick out the part that consists of the encrypted URL.
Is the SSL certificate going to be different everytime btween client and server?
The SSL certificate is the same for the entire SSL session, which persists beyond the current connection for as long as both client and server remember it.