Santiago Torres venit, vidit, dixit 25.01.2016 22:22: > Hello everyone. > > I've done some further research on the security properties of git > metadata and I think I've identified something that might be worth > discussing. In this case, The issue is related to the refs that point to > git tag objects. Specifically, the "loose" nature of tag refs might > possibly trick people into installing the wrong revision (version?) of a > file. > > To elaborate, the ref of a tag object can be moved around in the same > way a branch can be moved around (either manually or by using git > commands). If someone with write access can modify where this ref points > to, and points it to another valid tag (e.g., an older, vulnerable > version), then many tools that work under the assumption of static tags > might mistakenly install/pull the wrong reivision of source code. I've > verified that this is possible to pull off in package managers such as > PIP, rubygems, gradle(maven), as well as git submodules tracking tags. > > In order to stay loyal to the way files in the .git directory are > ordered, I don't think that making the ref file (or packed refs) files > differently is an option. However, I think that it could be possible to > store the "origin ref" in the git tag object, so tools can verify that > they are looking at the appropriate tag. There might also be a simpler > solution to this, and I would appreciate any feedback. > > What do you guys think? > > Thanks! > Santiago. If you cannot trust those with write access to a repo that you are pulling and installing from you might want to re-check where you are pulling or installing from ;) In fact, just like you shouldn't blindly download and install a tarball (but check its signature) you shouldn't blindly pull and install from a repo. Your best bet is checking the signature of signed tags. Now, if you're worried about someone maliciously pointing you to the wrong, correctly signed tag then you should verify that the tag object contains the tag "name" that you expect (for example by using "git verify-tag -v" or "git cat-file -p"), since that is part of the signed content. Michael -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html