RFR: 8341625: Improve ZipFile validation of the END header

[Lance Andersen]

On Mon, 7 Oct 2024 09:13:57 GMT, Eirik Bjørsnøs <eirbjo at openjdk.org> wrote:

> Please review this PR which adds validation of the 'total entries' value when fetched from the 'ZIP64 End of Central Directory' header.
> 
> We should reject this value under the following conditions:
> 
> 1. It is too large to fit within the specified CEN size (considering each CEN header encodes as at least 46 bytes each)
> 2. It is too large to create the `int[] entries` array safely (max value is `ArraysSupport.SOFT_MAX_ARRAY_LENGTH / 3`)
> 
> I claim that condition 2 here is already implicitly validated by the current maximum CEN size validation. (A CEN encoding such a large number of entries would exceed the maximum CEN size a lot and would already be rejected)
> 
> This change aims to protect the integrity of the implementation against specially crafted ZIP files. No sane ZIP tool will produce such files. 
> 
> Testing:
> 
> This PR adds a test `EndOfCenValidation.shouldRejectBadTotalEntries` which exercises the first condition above.
> 
> ZIP tests run locally. GHA results pending.

Marked as reviewed by lancea (Reviewer).

test/jdk/java/util/zip/ZipFile/EndOfCenValidation.java line 264:

> 262:          */
> 263: 
> 264:         byte[] zipBytes = HexFormat.of().parseHex("""

It might be beneficial to future readers to provide the steps used to create the  hex string in the format you have provided.

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PR Review: https://git.openjdk.org/jdk/pull/21384#pullrequestreview-2352700634
PR Review Comment: https://git.openjdk.org/jdk/pull/21384#discussion_r1790720612