RFR - 8132734: java.util.jar.* changes to support multi-release jar files

Xueming Shen xueming.shen at oracle.com
Wed Oct 21 07:17:01 UTC 2015

Hi Steve,

The reifiedEntry() approach probably can help the default JarVerifier 
work as expected, but if I read the
code correctly  I doubt you can get the expected CodSigner[] and 
Certificatte[] result from a "versioned"
JarFileEntry, after having read all bytes from the input stream 
(obtained via jzf.getInputStream(JarFileEntry)),
as the JarEntry spec suggests,. As we are passing the "reified" entry 
into the VerifierStream alone, without
any reference to the original jar file entry.  It seems impossible for 
the original jar file entry can trace back to
the corresponding certificates and code signers. This might be fixed by 
passing in the original entry together
into the JarVerifier, but I doubt we might have a bigger issue here. I 
suspect with this approach an external
verifier will have no easy way to verify the digit signature of the jar 
entry via java.security APIs. I would assume
this is doable right now with current JarFile APIs, via a JarFile 
object, a Manifest and a target JarEntry. The external
can get the signature via name -> manifest->attributes->signature 
(basically just consider to move the
JarVerifier and couple sun.security.util classes out and use it as user 
code)... but with this implementation
the name now  is the root entry, but the bytes you can read from the 
stream is from the versioned one.
We might want to bring in Max to take a look if what I said is really a 
supported use scenario. I might be
wrong, not a security expert :-)

Btw, for a "normal" JarEntry/ZipEntry (not a JarFileEntry), shouldn't 
the getInputStream(ze) simply return
the stream for the root entry? The current implementation of 
getJarEntry(ze) does not seem right, as it
returns a "versioned" JarFileEntry. I don't think you want to pass this 
one into VerifierStream directly,
right? Again, I think it might be desired (at least the spec is not 
updated to say anything about "version")
to simply return the input stream for the root entry.

One more "nitpick". searchForVersionedEntry() now lookups the versioned 
candidate via super.getEntry()
from version to BASE_VERSION, if the version is the latest version 9, 
the base is 0, we are basically doing
this search for each non-versioned-entry inside this multi-release-jar 
file 9 times everytime when the entry
is asked. In worse case scenario, a multi-release-jar, with huge number 
of entries with a small portion are
versioned to 9, and you are iterating it via "entries". Each lookup 
might be cheap, but it might be worth
considering adding some optimization.


On 10/20/2015 5:16 PM, Steve Drach wrote:
> Hi,
> Let’s try again.  I considered the issues brought up in the last 
> review and was able to not only remove the versionedEntry altogether, 
> I was able to greatly simplify the entire changeset.  I removed all 
> changes to JarEntry and JarVerifier, and added a name field and some 
> simple methods to JarFileEntry.  This solved a whole bunch of 
> potential issues. I’m also creating the jar files used in the tests so 
> there are no binaries in the changeset.  One test, 
> MultiReleaseJarURLConnection, has an error on windows because it can’t 
> delete one of the created jar files.  I don’t think I can do anything 
> about it — JDK-4823678 is a 12 year old bug that describes the 
> problem.  If anyone has an idea on what I can do to make this a clean 
> test, please let me know.
> Issue: https://bugs.openjdk.java.net/browse/JDK-8132734
> JEP 238: https://bugs.openjdk.java.net/browse/JDK-8047305
> Webrev: 
> http://cr.openjdk.java.net/~psandoz/multiversion-jar/jar-webrev/ 
> <http://cr.openjdk.java.net/%7Epsandoz/multiversion-jar/jar-webrev/>
> Thanks,
> Steve
>> On Oct 15, 2015, at 8:47 PM, Xueming Shen <xueming.shen at oracle.com 
>> <mailto:xueming.shen at oracle.com>> wrote:
>> On 10/15/15 1:53 AM, Paul Sandoz wrote:
>>>> On 15 Oct 2015, at 05:00, Xueming Shen <xueming.shen at oracle.com 
>>>> <mailto:xueming.shen at oracle.com>> wrote:
>>>> I'm not sure if it is a good idea, from performance perspective, to 
>>>> add a "versionEntry" field into the JarEntry
>>>> to support this feature, given most of the jar files might not be 
>>>> multi-release-jar aware, and the Jar input&
>>>> output streams dont work with a multi-release jar directly. Why 
>>>> should they all pay a runtime price for it. If
>>>> we really have to add an extra field, the JarFileEntry might be a 
>>>> better place, and it might be desired to
>>>> define a new subclass JarFileEntryMR to use when the MR is enabled, 
>>>> instead of adding directly into the existing
>>>> JarFileEntry.
>>> According to jol there is currently space available due to 
>>> alignment. If there was not it would add about 4% in direct instance 
>>> size. But the actual footprint is likely to be chunkier because of 
>>> the string character storage for the name so the % increase in size 
>>> would be smaller e.g. perhaps on average < 2% which might be ok 
>>> given that i presume such entries are unlikely to be cached.
>>> So i am not concerned about the size. If there was a way to design 
>>> it to avoid modification of existing classes all the better, but i 
>>> dunno if it is possible. Steve will surely know more.
>>> Paul.
>> Let's try it from another angle:-) Based on the webrev, no one need 
>> to and actually does create a
>> JarEntry with a versionedEntry, except JarFile, and JarFile only 
>> creates its own version of JarEntry,
>> the JarFileEntry.
>> The only non-JarFile consumer of "versioned" JarEntry is the package 
>> private JarVerifier.getCoderSigners,
>> and obviously it takes a JarFile together with the source JarEntry 
>> (again, if this jarEntry is not from A
>> JarFile, it should never have a "versionedEntry")
>> So why do you want to put this field into the super class JarEntry, 
>> not the JarFileEntry, don't see any
>> benefit of doing that.
>> While I'm writing this email, it appears to me that we might have a 
>> more "severe" issue with the
>> general/base JarEntry class to hold the link to the "versionedEntry". 
>> The "general" JarEntry object is
>> not associated with a specific JarFile (the JarFileEntry does). So 
>> there is no way for
>> JarFile.getInputStream(ZipFile ze) to verify that the JarEntry passed 
>> in and its "versionedEntry" is
>> actually belong to "this" JarFile in the following implementation, if 
>> the "ze" is just a JarEntry but
>> NOT instanceof of a JarFileEntry
>> 759     public synchronized InputStream getInputStream(ZipEntry ze)
>> 760         throws IOException
>> 761     {
>> 762         maybeInstantiateVerifier();
>> 763
>> 764 if (ze instanceof JarEntry) {
>> 765 ZipEntry vze = ((JarEntry)ze).versionedEntry;
>> 766 if (vze != null) {
>> 767 return getInputStream(vze);
>> 768 }
>> 769 }
>> 770
>> I think it's a bug of the implementation if we don't check, as the 
>> "versioned entry" is really
>> associated to the jar file that creates it. Sure, as I said above, 
>> there is actually no way you can
>> create a general JarEntry or a JarFileEntry with a "versionedEntry" 
>> from "outside", but it appears
>> to be possible (have not tried, just in theory) to mess up the 
>> current mechanism by passing a
>> "jar entry" from one JarFile instance to another one, if two JarFile 
>> instances are open on the same
>> multi-release-jar, but with different "version setting" policy...
>> But again, I still believe it might be a wrong approach to add such a 
>> "versionedEntry" into any of the
>> JarEntry, including the JarFileEntry. As specified by the 
>> specification, the returned entry should be the
>> jar entry pointing to the versioned entity in the Jar File, not the 
>> root one. The question I would like to
>> ask is why do you even need the "root entry" at all, if there is a 
>> matched versioned one. It might be
>> desired to have a mechanism to return the "base/root name" for such 
>> an entry, but it probably does
>> not deserve a "dedicate" entry object.
>> -Sherman

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