On Wed, Aug 28, 2013 at 6:26 PM, John Long <[email protected]> wrote:

> ...that problem is solved by using SHA1. The other issue, which is
> specific to
> specific situations, is whether the hash alone is sufficient to protect
> against malicious alteration of the repository. In the first case it would
> seem SHA1 is still acceptable although it's increasingly becoming apparent
> SHA1's days as an ideal hash have come and gone.


In principal it would be possible to update fossil at some point to use a
different hashing mechanism, and export a sha1-based repo to a new one.
They wouldn't be compatible after that, but nothing in the overall design
really prohibits it. There is arguably a micro-window of opportunity for
corruption during conversion unless the conversion is tested both ways, but
that would be manageable. There are "cosmetics", such the hard-coded word
"SHA1" everywhere (and related length/syntax constraints), but the
underlying SCM model is independent of the hashing algorithm used (or the
storage used to store the blobs, for that matter). A simple CRC32 would
"work just as well" for most purposes (though of course nobody's suggesting
that). That said, while the change is  simplein the abstract, SHA1 is
pretty well-entrenched into the source code, so it would be an invasive
port/change.

In the second case I think
> it's possible to prevent and/or detect of attacks on the repo with very
> minimal workflow adjustments I outlined earlier, or something similar to
> that, without any changes to fossil at all.
>

i'm still waiting for someone who has a head for security-related coding to
volunteer for that ;).

-- 
----- stephan beal
http://wanderinghorse.net/home/stephan/
http://gplus.to/sgbeal
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