From: Jeff King <peff@peff.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Junio C Hamano <gitster@pobox.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 0/2] Re-integrate sha1dc
Date: Thu, 16 Mar 2017 18:04:56 -0400 [thread overview]
Message-ID: <20170316220456.m4yz2kbvzv6waokn@sigill.intra.peff.net> (raw)
In-Reply-To: <alpine.LFD.2.20.1703161315310.18484@i7.lan>
On Thu, Mar 16, 2017 at 01:24:02PM -0700, Linus Torvalds wrote:
> I suspect the first patch will not make it to the list since it's over
> 100kB in size, but oh well.. Junio and Jeff will see it.
Yep, it didn't make it, but I got it.
> It "WorksForMe(tm)" and the integration patches are now fairly trivial,
> since upstream already did the dieting and some of the semantic changes to
> gits more traditional C code.
There are a few things I think are worth changing. The die() message
should mention the sha1 we computed. That will be a big help if an old
version of git tries to unknowingly push a colliding object to a newer
version. The user will see "collision on sha1 1234.." which gives them a
starting point to figure out where they got the bad object from.
And to make that work, we have to disable the safe_hash feature (which
intentionally corrupts a colliding sha1). We _could_ rip it out
entirely, but since it only kicks in when we see a collision, I doubt
it's impacting anything.
I also updated the timings in my commit message, and added a basic test.
> I did leave the C++ wrapper lines that the sha1dc header files have grown
> in the meantime, I debated removing them but felt that "closer to
> upstream" was worth it.
Yeah, I independently made the same decision.
So here's my version. It's on top of the hash.h tweak, as well.
[1/5]: add collision-detecting sha1 implementation
[2/5]: sha1dc: adjust header includes for git
[3/5]: sha1dc: disable safe_hash feature
[4/5]: Makefile: add USE_SHA1DC knob
[5/5]: t0013: add a basic sha1 collision detection test
Makefile | 11 +
hash.h | 2 +
sha1dc/LICENSE.txt | 30 +
sha1dc/sha1.c | 1808 +++++++++++++++++++++++++++++++++++++++++++++++
sha1dc/sha1.h | 122 ++++
sha1dc/ubc_check.c | 363 ++++++++++
sha1dc/ubc_check.h | 44 ++
t/t0013-sha1dc.sh | 19 +
t/t0013/shattered-1.pdf | Bin 0 -> 422435 bytes
9 files changed, 2399 insertions(+)
create mode 100644 sha1dc/LICENSE.txt
create mode 100644 sha1dc/sha1.c
create mode 100644 sha1dc/sha1.h
create mode 100644 sha1dc/ubc_check.c
create mode 100644 sha1dc/ubc_check.h
create mode 100755 t/t0013-sha1dc.sh
create mode 100644 t/t0013/shattered-1.pdf
-Peff
next prev parent reply other threads:[~2017-03-16 22:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-16 20:24 [PATCH 0/2] Re-integrate sha1dc Linus Torvalds
2017-03-16 22:04 ` Jeff King [this message]
2017-03-16 22:08 ` [PATCH 2/5] sha1dc: adjust header includes for git Jeff King
2017-03-16 22:08 ` [PATCH 3/5] sha1dc: disable safe_hash feature Jeff King
2017-03-16 22:09 ` [PATCH 4/5] Makefile: add USE_SHA1DC knob Jeff King
2017-03-16 22:43 ` Junio C Hamano
2017-03-17 0:11 ` Jeff King
2017-03-17 5:24 ` Junio C Hamano
2017-03-17 11:18 ` Jeff King
2017-03-17 17:09 ` [RFC PATCH 0/3] Git integration update for DC-SHA1 Junio C Hamano
2017-03-17 17:09 ` [PATCH 1/3] Makefile: add DC_SHA1 knob Junio C Hamano
2017-03-17 17:09 ` [PATCH 3/3] Makefile: make DC_SHA1 the default Junio C Hamano
2017-03-17 17:41 ` [RFC PATCH 0/3] Git integration update for DC-SHA1 Junio C Hamano
2017-03-17 17:45 ` Jeff King
2017-03-16 22:10 ` [PATCH 0/2] Re-integrate sha1dc Jeff King
2017-03-16 22:23 ` Junio C Hamano
2017-03-17 0:14 ` Jeff King
2017-03-17 5:22 ` Junio C Hamano
2017-03-17 11:22 ` Jeff King
2017-03-16 22:30 ` Linus Torvalds
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