<AWT Dev> Bug in AWT's image-loading Security checking?
linuxhippy at gmail.com
Wed Nov 7 11:13:12 PST 2007
I played a bit with JDK's source and researched a bit and I think I
was able to nail down the problem.
1.) The URL which refers to my image is redirected, the
redirection-logic is in URLImageSource.getDecoder
The original URL is: http://juibrowser.sf.net/imgs/1.png
The redirected URL is: http://juibrowser.sourceforge.net/imgs/1.png
2.) The ImageConsumerQueue associated with my
Image/ImageRepresentation does not have a securityContext set.
3.) When calling InputStreamImageSource.setDecoder, it loops over all
consumers in that queue calling checkSecurity.
If the image-url is not redirected this call does nothing, because
there's a check in URLImageSource.checkSecurity wether the URL was
redirected. (It only needs to be checked twice when the original URL
was redirected to another one). Thats why it works for not-redirected
For redirected images this calls SecurityManager.checkConnect with
context=null, which accordingly to Securitymanager's source immediatly
leads to a SecurityException.
So there are two possible solutions/problems:
1.) Modify the call to checkConnect in checkSecurity, to not specify a
Security-Context if context=null. I don't know wether this could lead
to security problems. I guess it would use the default context instead
a specified one - could this be problematic?
SecurityManager security = System.getSecurityManager();
if (security != null)
if(context != null)
security.checkConnect(actualHost, actualPort, context);
2.) Check why the context of the ImageConsumerQueue is null - is that
a valid configuration?
It would be great if somebody could loose some words about how this is
expected to work and wether solution 1.) could cause problems.
PS: Another potential "problem" I found is:
When the URL is redirected, the new port and the new hostname is
queried. However if somebody does not specify a port in the URL the
call to URL.getPort() returns -1, although the user ment port 80.
However later in checkSecurity the port-value is passed to the
SecurityManager - and its still -1 instead of 80. Worse the
SecurityManager handle's ports with -1 with a special case accordin to
> This method calls checkPermission with the
> SocketPermission(host+":"+port,"connect") permission if the port is not equal to -1.
> If the port is equal to -1, then it calls checkPermission with the
> SocketPermission(host,"resolve") permission.
At least as far as I can see the code does not anymore do for whats
intended. Could that be a problem?
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