RFR (Enhancement): 6194856: Zip Files lose ALL ownership and permissions of the files

Langer, Christoph christoph.langer at sap.com
Fri Oct 12 21:33:16 UTC 2018

Hi Sherman,

thanks for your input.

Next week I’ll work on updating my webrev to incorporate your points and I’ll also draft a CSR.

Best regards

From: Xueming Shen <xueming.shen at oracle.com>
Sent: Mittwoch, 10. Oktober 2018 09:17
To: Langer, Christoph <christoph.langer at sap.com>
Cc: core-libs-dev at openjdk.java.net
Subject: Re: RFR (Enhancement): 6194856: Zip Files lose ALL ownership and permissions of the files

Hi Langer,

Here are some of my comments.

    Optional<Set<...>> getPosixPermissions()
    (1) Is "Optional" really necessary here. it's a little inconsistent compared to the rest of
    methods in the class. a "null" return might be just fine?
    (2) Needs a <p> to separate the first line of the spec from the rest
    (3) The wording probably needs more consideration. For example, it might be more
         straightforward to use some similar wording from other methods, for example

... When read from a ZIP file, this is the posix permission stored in the {@code external

file attributes} field of the zip file entry's central directory record, if there is


      Also, a @ImplNote might be the better place for "it's not available when read from ZIS"?

    void setPosixPermissions( Set<PosixFilePermission> permissions)

    I can see the possible use case of using "null" as a special value to reset the
    permission field (and my proposal of simply returning a null from getPosixPermissions()
    when there is no one, brings some symmetry here?)

    (1) those POSIX_... constants don't need to be public?
    (2) I like the "stream" style implementation of permsTo/FromFlags pair, but have some
         concerns regarding their cost. "stream" is relative expensive (when you take a look at
         those supporting class underneath), as these two are supposed to be invoked for every
         entry inside a zip file, they can be hundreds and thousands ... just wonder, given most
         of the entries likely to have the "same" permission set inside a "normal" zip/jar file, is it
         worth to put in some cache mechanism here, especially for the "get" method, is it designed
         to return a read-only set of permission?  (in which we can use some mechanism here).
         That said PosixFileAttributes.getPermissions() actually purposely returns a modifiable set
         of permissions. It might be worth some discussion here, as the ZipEntry.getPosixPermission()
         needs to specify it, if it's going to return a immutable set.

Test: These days it is discouraged to check in a binary zip file as a test target. It is preferred
         to create the testing zip file on the fly.


On 9/25/18, 7:57 AM, Langer, Christoph wrote:
Hi all,

I had asked for opinions regarding adding posix permission support to JDK’s zip handling libraries and tools [1]. Since I didn’t get clear “no, you can’t do this” answers, I’m now concretely proposing some enhancements in the area of java.util.zip, jdk.zipfs and jdk.jartool.
I have reopened the long standing bug report (6194856) which had been set to “Won’t fix” quite recently for this purpose.

Here are the technical details:
The ZIP format specifications by infozip and pkware ([2] and [3]) do not explicitly specify the handling of posix file permissions. But it seems to be common sense that if file attribute compatibility is set to “Unix” in the upper byte of CEN field “version made by”, the file permissions bits are stored in CEN field “external file attributes”, byte 3 and 4. My changes try to honor this in the least obtrusive way. ��

The following changes are proposed:

it will have an additional field “posixPerms”. A value of -1 means “no permission information”, positive values will contain the flag values.
There will be 2 new public methods to read/set the permission information:
                public Optional<Set<PosixFilePermission>> getPosixPermissions()
                public void setPosixPermissions(Set<PosixFilePermission> permissions)
The usage of type “Optional” reflects that posix permissions are not necessarily present in a zip file
                it will have the capability to read the CEN fields and set posixPerms if available
                it will store entries with associated posix permissions as unix type in the CEN, together with the bit mask for the permissions

I propose to add and option "--preserve-posix" or short "-o" to honor the posix bits that may be stored inside zip/jar files. By default the option is not set and hence posix permissions are ignored. If the flag is set and the file system that the jar tool is running on supports posix, posix file permissions that exist in the file system will be stored in newly created/update archives or restored to the file system if such information is present in the archive.

                I added the capability for posix file permissions in the implementation. I decided to support PosixFileAttributes by subclassing ZipFileAttributes from this superclass as well as subclassing ZipFileAttributeView from PosixFileAttributeView. However, as PosixFileAttributes also include groups and owners, I would throw UnsupportedOperationExceptions in case of invoking methods to handle these attributes. But this approach seems to be most consistent with e.g. Files.setPosixFilePermissions and Files.getPosixFilePermissions.

                As this class presents a collection of static helpers, I added definitions for the posix file bit masks together with methods to convert between Sets of PosixFilePermission to bit masks containing the according switches and vice versa. These definitions could theoretically also be moved inside the java.util.zip or jdk.zipfs implementations where they wouldn’t be exposed as public APIs. However, in that case the code would probably need to be duplicated.

I’ve also created two jtreg testcases for both, java.util.zip and jdk.nio.zipfs.

The changes also contain a few further code cleanups.

Here are the links:
Bug: https://bugs.openjdk.java.net/browse/JDK-6194856
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/6194856.0/<http://cr.openjdk.java.net/%7Eclanger/webrevs/6194856.0/>

I’ll write a CSR once there’s some substantial feedback to my endeavor.

Thanks in advance for reviewing/commenting.

Best regards

[1] http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-September/055375.html
[2] http://www.info-zip.org/doc/appnote-19970311-iz.zip
[3] https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

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