Linus' reply on Git and SHA-1 collision

Post by sqeaky » Fri, Feb 24, 2017, 9:17 PM UTC

dozzie wrote: post #256

Xylakant wrote: post #255

Earlier quoted context omitted.

Gentoos emerge and FreeBSD port are package managers that preferably build from source. At least emerge also accepts git sources, with tags and commit specifiers. I haven't used bsd in a while on a prod system, but I'd not be surprised if port gained the same functionality - after all whether you're pulling a tarball and use a checksum for integrity checking or hand the task off to git makes exactly no difference at…

First, portage and ports are OS-supplied mechanism for installing software. They are nothing like pip or gems or npm, which only can install things written in their respective languages of choice and fail miserably for modules touching any library external to them (unless you manually ensure the library's and compiler toolchain's presence, that is). Second, ports and portage have support for and networks of mirror se…

Post by Florin_Andrei » Fri, Feb 24, 2017, 11:58 PM UTC

maligree wrote: post #221

Perseids wrote: post #182

Earlier quoted context omitted.

I don't like the living-on-the-edge-attitude that Linus and others here promote regarding Sha1 in git. First, attacks only get faster over time. What costs millions today is likely to be achievable on commodity hardware in the coming years. Second, attacks only get more flexible over time. A contrived collision on MD5 in 2004 got perfected to a single block collision in 2010 [1]. Third, devising an update strategy an…

"On the edge" "A contrived collision on MD5 in 2004 got perfected to a single block collision in 2010 [1]" so they'd have at least years to fix it were they using md5? He says they'll migrate, but it's no reason to go crazy. If anything, calmness of this sort is what we need more of (this industry, anyway... we go crazy about stuff way too much).

Post by theseoafs » Sat, Feb 25, 2017, 2:29 AM UTC

chmike wrote: post #113

There is not mutch risk now, but git should be able to switch to another and longer hash. Truncating another hash to 40 chars does not "fix" the problem. It just move it into another place. Another possibility, but this is a hack to keep key length to 40 chars, would be to change key encoding from hex encoding to base64. In 40 chars you could encode 240 bits instead of 160. It is preferable to get rid of the hard cod…

Post by mamon » Sat, Feb 25, 2017, 8:40 AM UTC

tanderson92 wrote: post #34

jessaustin wrote: post #32

Earlier quoted context omitted.

Haha you reminded me of the old riddle about how British engineers decided where to place armor on their bombers, because, "if they put it everywhere the plane wouldn't get off the ground!"

Specifically, during the war the engineers took a Bayesian approach and put armor on the bombers in locations where bombers which came back did not have damage. Reason being that hits in those sections of the planes were more likely than not resulting in fatalities. Smart thinking.

Post by grumbelbart » Sat, Feb 25, 2017, 10:31 AM UTC

snakeanus wrote: post #246

notfed wrote: post #56

Pertinent facts for the worried: 1) Git doesn't rely on SHA-1 for security. It relies on HTTPS, and a web of trust. 2) Even if git did rely on SHA-1, there's no imminent threat. What happened today was a SHA-1 collision, not a preimage attack. If a collision costs 2^n, a preimage attack costs 2^(2n). 3) Even if someone managed to pull off a preimage attack, creating a "poisonous" version of one your git repository's…

>1) Git doesn't rely on SHA-1 for security. It relies on HTTPS, and a web of trust. This is a big lie. When the -S flag is used, git signs the SHA-1 of the commit. Moreover HTTPS does not provide any form of authentication due to the extremely broken CA model. NSA could simply ask any CA to give them a cert for github for example. Not to mention that https would only authenticate that you are talking to the github se…