Transcript Sockets

Secure Sockets SSL/TLS
ICW: Lecture 6
Tom Chothia
Last Lecture
• How to make socket connections
between computers.
• Socket =
(IP_from,port_from,IP_to,port_to)
• java.io.Socket
• java.io.ServerSocket
Introduction

Why sockets aren't secure.
How to make secure socket connections.
The TLS/SSL protocol.
TLS/SSL in Java

javax.net.ssl.SSLSocket

javax.net.ssl.SSLServerSocket
Authenticating the Server.




The SSL/TLS Protocol
The Secure Sockets Layer (SSL) protocol has
been renamed the Transport Layer Security
(TLS).
It provides encrypted socket communication
and optionally authentication.
It may use a range of ciphers (RSA,DES,DH,..)
These are negotiation at the start of the run.
The Internet Protocol Stack,
(Most of the Time):
Stuff that you write
Application
TCP or UDP
Transport
IP
Network
Link/Hardware
Ethernet or 802.11
The Internet Protocol Stack
with TLS
Application
The TLS layer runs between
the Application layer and the
Transport layer.
Once the socket is open the
encryption is transparent to
the Application layer.
The normal TCP and IP
protocols etc. can be used at
the low layers
TLS
Transport
Network
Link/Hardware
TLS in Java
TLS with no Authentication
•
Create a SSLServerSocketFactory using
sockFact =
SSLServerSocketFactory.getDefault();
•
Create a SSLServerSocket:
secSock=sockFact.createServerSocket(portNo)
•
Set the Ciphers:
secSocket.setEnabledCipherSuites(ciphers);
•
Listen on the socket for an encrypted connection:
socket = (Socket) secSocket.accept();
Verifying Identity
•
A private key can be used “sign” a
message.
•
The public key can be used to verify
this signature.
•
If I have someone's public key, I can
use it to make sure I'm talking to them.
Cipher Suites
Cipher Suites with encryptions
and authentication:
Cipher Suites with just
authentication:
SSL_RSA_WITH_NULL_MD5
SSL_RSA_WITH_3DES_EDE_CBC_SHA
SSL_RSA_WITH_NULL_SHA
SSL_RSA_WITH_DES_CBC_SHA
SSL_RSA_WITH_RC4_128_MD5
SSL_RSA_WITH_RC4_128_SHA
TLS_DHE_DSS_WITH_AES_128_CBC_SHA
TLS_DHE_DSS_WITH_AES_256_CBC_SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA
TLS_DHE_RSA_WITH_AES_256_CBC_SHA
TLS_KRB5_EXPORT_WITH_DES_CBC_40_MD5
TLS_KRB5_EXPORT_WITH_DES_CBC_40_SHA
...
Cipher Suites with just
encryptions:
SSL_DH_anon_EXPORT_WITH_DES40_CBC_SHA
SSL_DH_anon_EXPORT_WITH_RC4_40_MD5
SSL_DH_anon_WITH_3DES_EDE_CBC_SHA
SSL_DH_anon_WITH_DES_CBC_SHA
SSL_DH_anon_WITH_RC4_128_MD5
TLS_DH_anon_WITH_AES_128_CBC_SHA
TLS_DH_anon_WITH_AES_256_CBC_SHA
TLS in Java
SSL/TLS contexts and Trust


SSL/TLS can set up a secure
connection with someone if we have
their public key.
The SSL context can be loaded with


the keys used to identify yourself.
the public keys of people we trust.
Keystores: a Reminder
•
We saw keystores in the Crypto
Lecture.
•
The Keystore stores password
protected keys and certifications.
•
Use “java.security.KeyStore” or the
“keytool” from the command line.
keytool
Generate and show a key for the server:
keytool -genkey -alias serverKey -keystore server.jks
keytool -list -keystore server.jks -storepass password
Export a certification for the key:
keytool -export -alias serverKey -file server.crt
-keystore server.jks
Import and show the certificate, at the client end:
keytool -import -keystore client.jks -alias serverCert
-file server.crt
keytool -list -keystore client.jks -storepass password
Certificate Chains
•
The public keys are stored as
certificates.
•
If we have someone's public key we
can use it to check their identity.
•
But we can't have the public key of
everyone on the Internet. :-(
Certificate Chains
•
If someone we trust signs someone
else's public key, we can trust them.
•
There are a number of companies that
check peoples identity and will sign
their public key. e.g. Versign.
•
These companies certificates are
embedded in most browsers.
Summary
• SSL/TLS is the most common way to secure
connections
–
–
javax.net.ssl.SSLSocket
javax.net.ssl.SSLServerSocket
• To Authenticate someone, you must have a
certificate/certificate chains for the server.
• Browsers come with certificates of Versign, etc.
they will check your IS and sign your key for a fee.
Next Time:
•
XML and Java XML tools.
•
XML is the default file format of Internet
systems.
•
The next lecture will tell you what XML
is and how to manipulate XML in Java.