On Wed, Feb 26, 2020 at 04:18:05PM -0500, Konstantin Ryabitsev wrote: > On Wed, Feb 26, 2020 at 05:04:42PM -0400, Jason Gunthorpe wrote: > > > - developer does all their work on a remote VM that doesn't have > > > access to their PGP keys and submits actual attestation when they > > > get back to their workstation > > > > Unfortunately this is a challenging work flow for a lot of reasons. :( > > Can you describe why? I would expect that this is done fairly routinely > due to having more compute power on a remote VM to run various tests. I've seen enough situations where people have a Linux server and a Windows laptop. They don't have a Linux desktop, so mixing a local 'secure' PGP key in a windows environment with the remote Linux server environment is challenging. If you have a secure 'Linux desktop environment' then I'd imagine always sending signed emails from there, and just using the server for test/etc. Certainly, exposing my email password (aka my cloud account password) is of even greater risk to me (and my company!) than exposing my PGP key. I want to keep it on my secure server, encrypted, etc. Actually I'm trying hard to move all my email access to OAUTH to minimize risks to my cloud accounts :\ > > > - developer submits a v1 of the patch that they don't expect to pass on > > > the first try and doesn't bother submitting attestation; shockingly, > > > the maintainer accepts it as-is and the developer can attest their > > > patches post-fact *without* needing to collect all the acked-by's > > > reviewed-by's etc from all others who have already responded to the v1 > > > submission > > > > But there won't be tags in this case, so how do we learn the original > > attestation-id to find the detatched signature? > > The attestation would be performed before all the follow-up tags are > applied, so the attestation-id would be the same. After the patch is > applied to a git repository, we can still use the "i" hash to look it up > (see more below). I'm not sure, if the '[PATCH xx v5]' is stripped then 'i' is not unique any more? > > > For example, a maintainer will almost certainly edit the message > > > content to add their own Signed-off-by, and may edit the patch for > > > minor nitpicking. > > > > The i/p/m will always change once in git: > > - The commit message is always changed, at least to add sign off > > - The email Subject is always changed to strip [PATCH xxx] > > This is already done by "git mailinfo" so I would expect that the i: > hash almost never changes, actually, unless the maintainer actually > edits the subject. Subject + Author + Email are sufficiently unique to > be able to locate the attestation data of the exact patch. Ah, using git mailinfos is not how you described 'i': $ egrep '^(Author|Email|Subject)' i | sha256sum 2a02abe02216f626105622aee2f26ab10c155b6442e23441d90fc5fe4071b86e - (also I do edit subjects a fair amount, again it would be interesting to see stats on how well this works) > So, the goal is not really to perform attestation once the patches made > it into the git tree. I am specifically trying to address the following > cases: > > - Someone poses as a trusted developer and submits a malicious patch > - Someone bribes me to edit a patch on lore.kernel.org to introduce a > backdoor Okay, but then post-apply-attestation doesn't help this threat model. post-apply-attestation is surely only useful if you can check the signature from the git data? Like I said it would be very interesting to see data on how well these signatures could survive, if we could get, what, 80% coverage of git commits this way then that seems like a powerful argument for this approach, right? Jason
