On Wed, Aug 28, 2013 at 06:40:19PM +0200, Stephan Beal wrote: > On Wed, Aug 28, 2013 at 6:26 PM, John Long <codeb...@inbox.lv> 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.
Understood. > > 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 ;). It's a workflow issue. No coding is required: 1. Create a new repo 2. Add a public key used for code signing 3. Optionally add a cross-signature of your code signing public key 4. Add all the source code you want to check in 5. Add detached signatures for all source code you checked in 6. fossil commit After that you simply detach-sign all source code before committing. >From then on, anybody who can access the repo can use the public key you saved in the repo to verify any individual source file based on the associated detached-signature. The key owner (or anyone else who has the pubkey the key owner cross-signed with) can user the cross signature to verify the public key in the repo hasn't been tampered with. In the absence of the cross-signing pubkey, or if you don't want to take the initial step of cross-signing the code signing key, anyone can verify the pubkey type, length, and fingerprint with the pubkey that was initially checked in and compare that to the verification output of any piece of source. /jl _______________________________________________ fossil-users mailing list fossil-users@lists.fossil-scm.org http://lists.fossil-scm.org:8080/cgi-bin/mailman/listinfo/fossil-users
