[jira] [Commented] (COMPRESS-542) Corrupt 7z allocates huge amount of SevenZEntries

["Stefan Bodewig (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COMPRESS-542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17370314#comment-17370314 ] 

Stefan Bodewig commented on COMPRESS-542:
-----------------------------------------

OK, my benchmarks https://github.com/bodewig/commons-compress-benchmarks/wiki/COMPRESS-542 show there is a certain performance hit if there are very many entries - then again I believe this is acceptable as we need to do the checks anyway and it is better to perform them before we allocate too much memory.

> Corrupt 7z allocates huge amount of SevenZEntries
> -------------------------------------------------
>
>                 Key: COMPRESS-542
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-542
>             Project: Commons Compress
>          Issue Type: Bug
>    Affects Versions: 1.20
>            Reporter: Robin Schimpf
>            Priority: Major
>         Attachments: Reduced_memory_allocation_for_corrupted_7z_archives.patch, endheadercorrupted.7z, endheadercorrupted2.7z
>
>          Time Spent: 3h 10m
>  Remaining Estimate: 0h
>
> We ran into a problem where a 1.43GB corrupt 7z file tried to allocate about 138 million SevenZArchiveEntries which will use about 12GB of memory. Sadly I'm unable to share the file. If you have enough Memory available the following exception is thrown.
> {code:java}
> java.io.IOException: Start header corrupt and unable to guess end Header
> 	at org.apache.commons.compress.archivers.sevenz.SevenZFile.tryToLocateEndHeader(SevenZFile.java:511)
> 	at org.apache.commons.compress.archivers.sevenz.SevenZFile.readHeaders(SevenZFile.java:470)
> 	at org.apache.commons.compress.archivers.sevenz.SevenZFile.<init>(SevenZFile.java:336)
> 	at org.apache.commons.compress.archivers.sevenz.SevenZFile.<init>(SevenZFile.java:128)
> 	at org.apache.commons.compress.archivers.sevenz.SevenZFile.<init>(SevenZFile.java:369)
> {code}
> 7z itself aborts really quick when I'm trying to list the content of the file.
> {code:java}
> 7z l "corrupt.7z"
> 7-Zip 18.01 (x64) : Copyright (c) 1999-2018 Igor Pavlov : 2018-01-28
> Scanning the drive for archives:
> 1 file, 1537752212 bytes (1467 MiB)
> Listing archive: corrupt.7z
> ERROR: corrupt.7z : corrupt.7z
> Open ERROR: Can not open the file as [7z] archive
> ERRORS:
> Is not archive
> Errors: 1
> {code}
> I hacked together the attached patch which will reduce the memory allocation to about 1GB. So lazy instantiation of the entries could be a good solution to the problem. Optimal would be to only create the entries if the headers could be parsed correctly.



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