ENCRYPT layer. Encrypt and decrypt the group communication in JGroups
The file can be used in two ways:
- Option 1. Configured with a secretKey in a keystore so it can be used at any
layer in JGroups without the need for a coordinator, or if you want protection against passive
monitoring but do not want the key exchange overhead and complexity. In this mode all nodes must be distributed with
the same keystore file.
- Option 2. Configured with algorithms and key sizes. The Encrypt Layer in this mode sould be used between the
FRAG and PBCast layers in the stack. The coordinator then chooses the
secretkey which it distributes amongst all the peers. In this form no keystore exists as the keys are
distributed using a public/private key exchange. View changes that identify a new controller will result in a new session key
being generated and then distributed to all peers. This overhead can be substantial in a an application with
a reasonable peer churn.
Each message is identified as encrypted with a specific encryption header which identifies
the type of encrypt header and an MD5 digest that identifies the version of the key being used
to encrypt/decrypt the messages.
Option 1
This is the simplest option and can be used by simply inserting the Encryption layer
at any point in the JGroup stack - it will encrypt all Events of a type MSG that
have a non-null message buffer. The format of the entry in this form is:
<ENCRYPT key_store_name="defaultStore.keystore" store_password="changeit" alias="myKey"/>
An example bare-bones.xml file showing the keystore version can be found in the conf
ina file called EncryptKeyStore.xml - along with a defaultStore.keystore file.
In order to use the Encrypt layer in this manner it is necessary to have the secretKey already generated
in a keystore file. The directory containing the keystore file must be on the application's classpath.
You cannot create a SecretKey keystore file using the keytool application shipped with the JDK.
A java file called KeyStoreGenerator is included in the demo
package that can be used from the command line (or IDE) to generate a suitable keystore.
Option 2
This option is suited to an application that does not ship with a known key but instead it is generated
and distributed by the controller. The secret key is first generated by the Controller (in JGroup terms). When a view change
occurs a peer will request the secret key by sending a key request with its own public key. The controller
encrypts the secret key with this key and sends it back to the peer who then decrypts it and installs the
key as its own secret key.
All encryption and decryption of Messages is done using this key. When a peer receives
a view change that shows a different keyserver it will repeat this process - the view change event
also trigger the encrypt layer to queue up and down messages until the new key is installed.
The previous keys are retained so that messages sent before the view change that are queued can be decrypted
if the key is different.
An example EncryptNoKeyStore.xml is included in the conf file as a guide.
Note: the current version does not support the concept of perfect forward encryption (PFE)
which means that if a peer leaves the group the keys are re-generated preventing the departed peer from
decrypting future messages if it chooses to listen in on the group. This is not included as it really requires
a suitable authentication scheme as well to make this feature useful as there is nothing to stop the peer rejoining and receiving the new
key. A future release will address this issue.
down
public void down(Event evt)
An event is to be sent down the stack. The layer may want to examine its type and perform
some action on it, depending on the event's type. If the event is a message MSG, then
the layer may need to add a header to it (or do nothing at all) before sending it down
the stack using passDown()
. In case of a GET_ADDRESS event (which tries to
retrieve the stack's address from one of the bottom layers), the layer may need to send
a new response event back up the stack using passUp()
.
- down in interface Protocol
getAsymAlgorithm
protected String getAsymAlgorithm()
- Returns the asymAlgorithm.
getAsymCipher
protected Cipher getAsymCipher()
getAsymInit
protected int getAsymInit()
getAsymProvider
protected String getAsymProvider()
- Returns the asymProvider.
getDesKey
protected SecretKey getDesKey()
getKeyServerAddr
protected Address getKeyServerAddr()
- Returns the keyServerAddr.
getKeyStoreName
protected String getKeyStoreName()
- Returns the keyStoreName.
getKpair
protected KeyPair getKpair()
getLocal_addr
protected Address getLocal_addr()
getServerPubKey
protected PublicKey getServerPubKey()
- Returns the serverPubKey.
getSymAlgorithm
protected String getSymAlgorithm()
- Returns the symAlgorithm.
getSymDecodingCipher
protected Cipher getSymDecodingCipher()
- Returns the symDecodingCipher.
getSymEncodingCipher
protected Cipher getSymEncodingCipher()
- Returns the symEncodingCipher.
getSymInit
protected int getSymInit()
getSymProvider
protected String getSymProvider()
init
public void init()
throws Exception
Called after instance has been created (null constructor) and before protocol is started.
Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
- init in interface Protocol
initKeyPair
public void initKeyPair()
throws Exception
Generates the public/private key pair from the init params
initSymKey
public void initSymKey()
throws Exception
Used to initialise the symmetric key if none is supplied in a keystore.
reset
public void reset()
Just remove if you don't need to reset any state
setKeyServerAddr
protected void setKeyServerAddr(Address keyServerAddr)
keyServerAddr
- The keyServerAddr to set.
setLocal_addr
protected void setLocal_addr(Address local_addr)
local_addr
- The local_addr to set.
setProperties
public boolean setProperties(Properties props)
Configures the protocol initially. A configuration string consists of name=value
items, separated by a ';' (semicolon), e.g.:
"loopback=false;unicast_inport=4444"
- setProperties in interface Protocol
up
public void up(Event evt)
An event was received from the layer below. Usually the current layer will want to examine
the event type and - depending on its type - perform some computation
(e.g. removing headers from a MSG event type, or updating the internal membership list
when receiving a VIEW_CHANGE event).
Finally the event is either a) discarded, or b) an event is sent down
the stack using passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
- up in interface Protocol