RFR: 8277087: ZipException: zip END header not found at ZipFile#Source.findEND

[Lance Andersen]

On Sat, 13 Nov 2021 23:16:22 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> The ZipOutputStream class may create bogus zip data which cannot be opened by the ZipFile. The root cause is how the comment field is stored by the ZipOutputStream. According to the zip specification, the comment field should not be longer than 0xFFFF bytes, and we try to validate the length of the comment, but unfortunately, we do this after the comment was assigned already. So if the application saves the comment based on the user's input and then gets an exception from the ZipOutputStream.setComment() it may assume that the comment is too long and it will be ignored, but it will be saved as-is to the file.
> 
> Please take a look at [this](https://github.com/openjdk/jdk/commit/c435a0905dfae827687ed46015269f9c1b36c239#diff-736e247f0ec294323891a77e16a9f0dba8bc1872131c857edf18c3f349e750eeL117) refactoring, and note:
>  * The comment field is assigned before the length check
>  * The null comment is ignored
> 
> The current fix will move the length validation before being assigned and will use the null comment as an empty text. Note that the behavior of the null parameter is not specified in the method/class/package so we are free here to implement it in any way, any thoughts/suggestions on which is better?

Thank you for the proposed fix.   I am curious as to how you encountered this as comments are rarely used with Zip files.

test/jdk/java/util/zip/ZipOutputStream/EmptyComment.java line 35:

> 33:  * @summary Verifies various use cases when the zip comment should be empty
> 34:  */
> 35: public final class EmptyComment {

Please consider converting this to use TestNG and a DataProvider as it will simply the code even further

-------------

Changes requested by lancea (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6380