RFR 8164705: Remove pathname canonicalization from FilePermission

[Alan Bateman]

On 25/08/2016 04:55, Weijun Wang wrote:

> Hi All
>
> Please take a look at
>
>    http://cr.openjdk.java.net/~weijun/8164705/webrev.00
>
> From the beginning of JDK, FilePermission canonicalizes the input path 
> and use the result in implies() and equals(). This has been a big 
> performance hurt and leads to confusing results when symlinks are 
> involved.
>
> The code change above removes the canonicalization.
>
> This means FilePermission on "/the/current/working/directory/x" no 
> longer implies that on "x". Since this might bring quite some 
> compatibility risk, the code change includes some tweaks in permission 
> checking to make sure an app is still able to read "x" when the 
> FilePermission granted is on "/the/current/working/directory/x". 
> However, we still hope the policy to be updated to be consistent of 
> how a file is actually accessed.
>
> No tweak is devoted to make granting "/this/is/a/symlink" to imply 
> reading of "/the/actual/target/file", because we think it should not.
>
> This is quite a big behavior change. If it breaks your app/lib, or 
> does not work with your customized security manager or policy 
> implementation, please let us know.
>
> Feel free to provide any feedback.
>
> Finally, a new system property "jdk.filepermission.canonicalize" is 
> introduced and it can be "true", "false", or "compat". The out-of-box 
> default is "compat", which means no canonicalization with check tweaks.
I've taken a first pass over this. A general comment then it's great to 
see FilePermission changed to not do canonicalization. The "new 
behavior" approach to match paths and support absolute => relative and 
relative => absolute all makes sense.

I agree that having a property to revert to legacy behavior make sense. 
Is there any way to reduce this down to just current and legacy 
behavior, it's otherwise too complicated to describe the subtle 
differences between "false" and "compat". If it can be reduced to two 
settings then a name such as 
jdk.io.permissionsUseCanonicalPath=<boolean> could be better than the 
prototype name.

For the implementation then I think it will cleanup before this is ready 
to push. FilePermCompat is a ugly, particularly FilePermission changing 
its public fields. Also method names like impliesWithAltFP, 
newPermPlusAltPath, ... could be re-visited to make them much clearer.

For the test then it would be good if samepath.sh could be replaced with 
a non-shell test.

-Alan