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#1 2018-06-06 22:42:45

RickDeckard
Member
Registered: 2016-02-19
Posts: 29

[solved] Checksums of exact same files different on two Arch boxes

I'm running two laptops with the 4.16.11-1-hardened kernel, one which I'm using as a SSH server, and I have SELinux enabled on both.  In no condition to use the client for compilation purposes, I had to copy over the SELinux packages which I thought were trusted as part of a recent upgrade.  Strangely enough, some of my client's important packages are reporting - via automated scanning - checksums vastly changed between both computers, even as the package files are themselves the same version.  For the past few days, I've been trying to figure out what could have caused this. 

All of the binaries in the util-linux-selinux package (which the scanner readouts first directed me to) are exactly 8 bytes less than they are on the source machine.  That made me think of some kind of corruption/compression loss on package transfer - which I then ruled out as this is happening to files belonging to packages not copied via scp.  I've also ruled out update schedules not matching up, and even underlying filesystem issues.  Strangest part then being, I reinstalled util-linux-selinux from a cached copy, and the md5/sha256sums taken from command line became completely different than even that which was messed up to begin with. 

I'm at a loss as to explain what's going on.  If there's a good reason for file integrity to just change out of the blue like this would someone please let me know?

Last edited by RickDeckard (2018-06-13 16:44:41)

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#2 2018-06-07 02:28:00

Eschwartz
Trusted User/Bug Wrangler
Registered: 2014-08-08
Posts: 1,964

Re: [solved] Checksums of exact same files different on two Arch boxes

There's no good reason for that to happen, but I can think of one bad reason. Do you have "prelink" installed? If you do, I suggest you remove it as it's not supported and additionally believed to cause great harm.

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#3 2018-06-07 03:33:09

RickDeckard
Member
Registered: 2016-02-19
Posts: 29

Re: [solved] Checksums of exact same files different on two Arch boxes

No, I don't on either device.

Last edited by RickDeckard (2018-06-07 03:33:25)

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#4 2018-06-12 23:38:52

RickDeckard
Member
Registered: 2016-02-19
Posts: 29

Re: [solved] Checksums of exact same files different on two Arch boxes

Okay, after running a file comparison between my two systems (one is an Intel i3, one an AMD V120) and upgrading AUR packages without copying, I've come to believe the automatic compiler options - such as link-time optimization - and the processors at hand have a lot to do with what I'm seeing.  Still doesn't explain why some files in the packages awaiting compilation appear as identical when others don't, but at least it's half of an answer and that's good enough for me.

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#5 2018-06-13 01:14:36

Trilby
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Registered: 2011-11-29
Posts: 19,344
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Re: [solved] Checksums of exact same files different on two Arch boxes

RickDeckard wrote:

I've come to believe the automatic compiler options - such as link-time optimization - and the processors at hand have a lot to do with what I'm seeing.

That certainly would result in differences if you are using different compile options on each machine (or anything like -march=native which expands to something different on each machine).  Are you using different build options?

RickDeckard wrote:

Still doesn't explain why some files in the packages awaiting compilation appear as identical when others don't, but at least it's half of an answer and that's good enough for me.

If it is good enough, you could mark this as SOLVED, but if you want to figure it out, you should specify some examples of files are or are not identical.


"UNIX is simple and coherent..." - Dennis Ritchie, "GNU's Not UNIX" -  Richard Stallman

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#6 2018-06-13 03:29:24

Eschwartz
Trusted User/Bug Wrangler
Registered: 2014-08-08
Posts: 1,964

Re: [solved] Checksums of exact same files different on two Arch boxes

I'm confused now, since I originally thought the files were created on one computer, then somehow got modified after copying them to another computer. If they're being separately compiled on each computer it's hardly surprising they're different. See https://reproducible-builds.org/

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#7 2018-06-13 16:43:04

RickDeckard
Member
Registered: 2016-02-19
Posts: 29

Re: [solved] Checksums of exact same files different on two Arch boxes

Trilby wrote:

Are you using different build options?

No, they weren't any different.  All I did was disable link-time optimization on both devices to see if that might have had an effect.  Mostly went with the original pkgbuild.

Eschwartz wrote:

I'm confused now, since I originally thought the files were created on one computer, then somehow got modified after copying them to another computer.

Originally, they were, then I bit the bullet and tried to compile the packages natively to see if that would resolve the situation.

Oh well.  Guess it's just one of those things.

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#8 2018-06-13 16:48:04

Trilby
Inspector Parrot
Registered: 2011-11-29
Posts: 19,344
Website

Re: [solved] Checksums of exact same files different on two Arch boxes

RickDeckard wrote:

Mostly went with the original pkgbuild.

A man went to the doctor complaining of horrible abdominal pain.  The doctor, after some examination and tests, asked if the man had been swallowing any non-food items.  The man replied 'Oh gosh no, I mostly just eat food.'  The doctor diagnosed him as mostly healthy and sent him on his way.

Last edited by Trilby (2018-06-13 18:03:20)


"UNIX is simple and coherent..." - Dennis Ritchie, "GNU's Not UNIX" -  Richard Stallman

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#9 2018-06-13 17:37:04

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 15,806

Re: [solved] Checksums of exact same files different on two Arch boxes

Reminds me of this:

https://en.wikipedia.org/wiki/Mars_Clim … of_failure

Heads buried in sand. No one seemed to care after the discrepancy was noticed.

Last edited by ewaller (2018-06-13 17:38:15)


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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