On 8/15/2012 3:26 AM, Xuelei Fan wrote:
More comments about whether we are able to override the default value.
On 8/15/2012 10:45 AM, Xuelei Fan wrote:
Thought more about the design, I would have to say that we cannot return
the default value in sslParameters.getServerNames(). Otherwise, the
following two block of codes look very weird to me:
// case one:
1 SSLparameters sslParameters = sslSocket.getSSLParameters();
2 sslParameters.clearServerName("host_name");
3 Map<String, String> names = sslParameters.getServerNames();
4 sslSocket.setSSLParameters(sslParameters);
5 sslParameters = sslSocket.getSSLParameters();
6 names = sslParameters.getServerNames();
In line 3, the returned map does not contain "host_name" entry. But in
line 6, it may be expected that no "host_name" in the returned map. But
if we want to return default values, line 6 do need to return a map
containing "host_name". The behavior is pretty confusing. We may want
to try avoid the confusion.
I'm not following your confusion, it seemed pretty straightforward to
me, it works much like CipherSuites. We have a set of ciphersuites
which are enabled by default. We can turn some off by using
SSLParameters.
Compatibility is my concerns here.
When the SSLParameters class was was introduced in JDK 6,
set/getCipherSuites() and set/getProtocols were new, so there was no
compatibility issue for these two pairs methods at that time, as they
were not used in old applications.
In JDK 7, we introduced two new methods, set/getAlgorithmConstraints().
We were luck that we cannot allow the override of default constraints
because of security consideration,
I didn't quite follow this sentence. We do allow the override, right?
Looking at SSLSocketImpl.setSSLParameters():
algorithmConstraints = params.getAlgorithmConstraints();
and the concept of algorithm
constraints was new in JDK 7. So we needed not to consider the
compatibility issue too much between JDK 6 and 7 for this pair of methods.
However, things get changed for the Server Name Inidication (SNI),
because in JDK 7 we have already support default SNI extension implicit.
We have to consider the compatibility issues more between JDK 7 and JDK
8, we need to make sure the behaviors are consistent whenever we call
the set/getServerName(). If we allow override of default value, the
application may run into corner trap as the description in my previous mail.
Not sure this is a problem, possibly I didn't explain my thought fully.
That's the background of my thoughts. Hope it helps you understand the
current design.
Here's what I was trying to propose:
SSLParameters:
// Local storage like the other variables
private Map<String, String> sniNames = null;
...deleted...
/**
* Set the SNI Names.
*
* A null parameter means don't set anything. Nothing is set.
*
* disallow invalid String->null entries.
*
* valid String->String entries will be added to SNI extension
* if there is a recognized Key type.
*/
public void setServerNames(Map<String, String> map)
/**
* Returns a copy of the array of servernames or null if
* none have been set.
*/
public Map<String, String> getServerNames()
SSLSocketImpl:
synchronized public void setSSLParameters(SSLParameters params) {
super.setSSLParameters();
...deleted...
Map<String,String> sniNames = params.getServerNames();
if (sniNames != null) {
sniNameStorage = sniNames.clone();
}
synchronized public SSLParameters getSSLParameters() {
SSLParameters params = super.getSSLParameters();
...deleted...
// sniNameStorage currently has one entry:
// "host_name", "www.example.com"
params.setServerNames = sniNameStorage.clone();
So looking at the two use cases you pointed out:
1. SSLParameters sslp = new SSLParameters()
getServernames() would return null. When SSLSocketImpl.setSSLParameters
is called, the null indicates there is nothing to set, and the default
value remains. If app wants to set something here, it can, which would
override the existing default.
2. SSLParameters sslp = SSLSocket.getSSLParameters()
The SSLParameters will be populated with the SNI map value stored in
SSLSocketImpl/SSLEngineImpl, and apps can do whatever they choose with
the Map. When setSSLParameters is called, the potentially new values
are just pushed back to the SNI. In this case, the application has full
access to the default Map and can see what will be sent by default.
In both cases, the default remains unless the application takes steps to
change it. For applications, this is the same call model as
setCipherSuites()/setProtocols(), but the magic happens at different levels.
Am I missing something?
> because in JDK 7 we have already support default SNI extension
> implicit.
We are just providing API access to that functionality.
Brad
Thanks,
Xuelei
Expanding a bit on your example here, I'll describe what
I think would happen internally/externally:
1 SSLSocket sslSocket = mySSLSocketFactory.createSocket(
"www.example.com", 443);
mySSLSocketFactory sets any initial parameters as usual. SSLSocketImpl
knows it's connecting to www.example.com and automatically stores
"host_name" -> "www.example.com" in its local host data (map or separate
variables).
2 SSLparameters sslParameters = sslSocket.getSSLParameters();
SSLSocketImpl.getSSLParameters() creates a SSLParameters, and sets the
hostmap to the one value "host_name" -> "www.example.com"
If the application want to get the "default values", they just pull them
out of the SSLParameters here
3 sslParameters.clearServerName("host_name");
Or sslParameters.setServerName("host_name", null)?
User just decided to clear it. Ok, that's what we do. It becomes an
empty map in SSLParameters.
4 Map<String, String> names = sslParameters.getServerNames();
Returns empty Map.
As far as good.
5 sslSocket.setSSLParameters(sslParameters);
SSLSocketImpl.setSSLParameters is empty, so SSLSocketImpl takes this
SSLParameters and as a result, clears it's internal "host_name" map to
null, and thus won't send anything out since it's empty.
We have problems here. We need to support that if an application does
not specified host_name value, we should use default values.
I. SSLParameters sslParameters = new SSLParameters();
II. sslParameters.setCipherSuites(...);
III. SSLSocket sslSocket =
sslSocketFactory.createSocket("www.example.com", 443)
IV. sslSocket.setSSLParameters(sslParameters);
Before line IV and after line II, the sslParameters.getServerNames() are
empty. In line IV, we need to make sure the internal "host_name",
"www.example.com" is used as default value, and send it to server in
SNI. That's the default behaviors in JDK 7. We cannot break it without
strong desires.
I think it means that we cannot clear the internal "host_name" when the
sslParameters.getServerNames() return empty.
Does it make sense to you?
Thanks,
Xuelei
6 sslParameters = sslSocket.getSSLParameters();
SSLSocketImpl.getSSLParameters() creates a SSLParameters, which sees
that there's no name indication, so it creates an empty name map and
stores in SSLParameters.
7 names = sslParameters.getServerNames();
returns empty.
It's no longer the default value, because they have specifically set the
value.
HTH,
Brad
