SSL Authentication with Certificates: Should the Certificates have a hostname?
- by sixtyfootersdude
Summary
JBoss allows clients and servers to authenticate using certificates and ssl. One thing that seems strange is that you are not required to give your hostname on the certificate.
I think that this means if Server B is in your truststore, Sever B can pretend to be any server that they want.
(And likewise: if Client B is in your truststore...)
Am I missing something here?
Authentication Steps
(Summary of Wikipeida Page)
Client Server
=================================================================================================
1) Client sends Client Hello
ENCRIPTION: None
- highest TLS protocol supported
- random number
- list of cipher suites
- compression methods
2) Sever Hello
ENCRIPTION: None
- highest TLS protocol supported
- random number
- choosen cipher suite
- choosen compression method
3) Certificate Message
ENCRIPTION: None
-
4) ServerHelloDone
ENCRIPTION: None
5) Certificate Message
ENCRIPTION: None
6) ClientKeyExchange Message
ENCRIPTION: server's public key => only server can read
=> if sever can read this he must own the certificate
- may contain a PreMasterSecerate, public key or nothing (depends on cipher)
7) CertificateVerify Message
ENCRIPTION: clients private key
- purpose is to prove to the server that client owns the cert
8) BOTH CLIENT AND SERVER:
- use random numbers and PreMasterSecret to compute a common secerate
9) Finished message
- contains a has and MAC over previous handshakes
(to ensure that those unincripted messages did not get broken)
10) Finished message
- samething
Sever Knows
The client has the public key for the sent certificate (step 7)
The client's certificate is valid because either:
it has been signed by a CA (verisign)
it has been self-signed BUT it is in the server's truststore
It is not a replay attack because presumably the random number (step 1 or 2) is sent with each message
Client Knows
The server has the public key for the sent certificate (step 6 with step 8)
The server's certificate is valid
because either:
it has been signed by a CA (verisign)
it has been self-signed BUT it is in the client's truststore
It is not a replay attack because presumably the random number (step 1 or 2)
is sent with each message
Potential Problem
Suppose the client's truststore has certs in it:
Server A
Server B (malicous)
Server A has hostname www.A.com
Server B has hostname www.B.com
Suppose: The client tries to connect to Server A but Server B launches a man in the middle attack.
Since server B:
has a public key for the certificate that will be sent to the client
has a "valid certificate" (a cert in the truststore)
And since:
certificates do not have a hostname feild in them
It seems like Server B can pretend to be Server A easily.
Is there something that I am missing?
