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From Myria <myriac...@gmail.com>
Subject Re: SHA-1 collision in repository?
Date Thu, 22 Feb 2018 22:29:29 GMT
That was one document we ran into when searching, yes.

We can do an svnsync, but this will take about a week to run--the
repository is 43 GB with 600,000 commits.  I guess we'll start it now.

On Thu, Feb 22, 2018 at 2:04 PM, Matt Simmons <bandman@gmail.com> wrote:
> Hi Melissa,
>
> That definitely is interesting.
>
> I assume you have read
> http://blogs.collab.net/subversion/subversion-sha1-collision-problem-statement-prevention-remediation-options
>
> If you do an svnsync to another location and attempt the commit there, does
> the problem replicate itself?
>
> --Matt
>
>
> On Thu, Feb 22, 2018 at 12:30 PM, Myria <myriachan@gmail.com> wrote:
>>
>> When we try to commit a very specific version of a very specific
>> binary file, we get a SHA-1 collision error from the Subversion
>> repository:
>>
>> D:\confidential>svn commit secret.bin -m "Testing broken commit"
>> Sending        secret.bin
>> Transmitting file data .svn: E160000: Commit failed (details follow):
>> svn: E160000: SHA1 of reps '604440 34 134255 136680
>> c9f4fabc4d093612fece03c339401058
>> db11617ef1454332336e00abc311d44bc698f3b3 605556-czmh/_8' and '-1 0
>> 134255 136680 c9f4fabc4d093612fece03c339401058
>> db11617ef1454332336e00abc311d44bc698f3b3 605556-czmh/_8' matches
>> (db11617ef1454332336e00abc311d44bc698f3b3) but contents differ
>>
>>
>> What can cause this?  This file is a binary pixel shader compiled from
>> a build process.  It's most certainly not Google's SHA-1 collision PDF
>> files.  We also scanned the repository to confirm that nobody has
>> committed Google's collision files.
>>
>> Occam's Razor suggests that something is wrong with our repository or
>> Subversion itself, rather than this being a true SHA-1 collision.  In
>> that case, what is wrong with our repository?
>>
>> If this really is a SHA-1 collision, it would be major cryptography
>> news that someone randomly ran into a second collision without even
>> trying.  In that case, is there a method by which we could recover the
>> two files that supposedly have the same SHA-1?  The collision doesn't
>> appear to be in the file itself, but in some sort of diff or revision
>> output?
>>
>> Thanks,
>>
>> Melissa
>
>
>
>
> --
> "Today, vegetables... Tomorrow, the world!"

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