RFR [9] 8139706: JarFile.getBytes could use InputStream.readNBytes

Xueming Shen xueming.shen at oracle.com
Fri Oct 16 02:09:58 UTC 2015

On 10/15/15 3:08 PM, Claes Redestad wrote:
> On 2015-10-15 23:21, Chris Hegarty wrote:
>>> On 15 Oct 2015, at 21:59, ecki at zusammenkunft.net wrote:
>>> Hello,
>>> This does change a bit the semantic of the length check. If the 
>>> stream would return more bytes than the zipentry says the new 
>>> version would ignore them, the  old version was consuming then and 
>>> then fail the check. However I am not sure if this is relevant.
>> Right, there are certainly some subtle differences resulting from
>> the proposed change. When working on JDK-8138978 I thought
>> about using readNBytes, but played it safe as IOUtils was growing
>> the bye[] lazily too, so no real perf difference.  In fact, I think I 
>> seen
>> a test failure with using readNBytes here. I’ll have to check.
> Seeing no jtreg test failures in java/util/zip nor java/util/jar 
> (apart from 2 ignored tests), but I can see a reason for the current 
> implementation being conservative: Corrupt/malicious jar files might 
> lie about the entry length and report very large values, which could 
> bring a down with OOME.
> I believe we could be both safe and faster than baseline by adding a 
> reasonable limit for when to use readNBytes, e.g., 32k would deal with 
> the majority of .class files.
getBytes should be used to read the meta-inf files only, not the .class 


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