Hi All, On Wed, May 20, 2015 at 6:59 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > [added cc's from the other thread] > > On 05/19/2015 01:02 PM, Luis R. Rodriguez wrote: >> >> David Howells has posted v4 of his series of supporting PKCS#7 for module >> signing. I'm in my v3 series now on RFCs for firmware PKCS#7 support, and >> after >> some review and patch shuffling I think this is ready for patch form. My >> own >> series however depend on quite a bit of other pending changes, one series >> which >> will go through Rusty's tree, another series of fixes on firmware_class >> which >> should go through Greg's tree. I'll wait until all this and David's own >> patches >> get merged before posting firmware PKCS#7 support. Before all this though >> in >> preparation for fw signing one thing we should start to talk about more >> broadly >> however is how linux-firmware binary file signing would work in practice >> and >> what we need, and make sure folks are OK with all this. >> >> First, firmware signing will be completely optional as with module >> signing. >> > > ... > >> Other than this last nitpick, any other concerns or recommendations ? > > > A couple. Some of these are general concerns with the existing > infrastructure, but #1 is a specific problem that gets much worse if we add > firmware signing. Feel free to ignore 2-4. > > 1. We should get the signature semantics right. I think that, for modules, > we currently sign literally the module payload. For modules, in my > semi-amateurish crypto universe [1], this is fine *as long as the key in > question is used for no other purpose*. For firmware, it's dangerous, since > it would be vulnerable to substitution attacks in which the adversary > convinces us to interpret one firmware file as firmware for another device > or purpose entirely. > > We should be signing something that's semantically equivalent to "This is a > valid module: xyz", "This is a valid 'regulatory.bin': xyz", or "This is a > valid kexec image: xyz". Something that occurred to me (as a complete bystander) was: would it make sense to have keys able to be restricted to particular "types" of signable data? I.e. the key that can sign a valid regulatory.bin file cannot be used to sign a module or a kexec image. - This could remove the need to have multiple keyrings. (Also, UEFI keys unless otherwise tagged could be restricted to only signing bootloaders or kernels) Also, are multiple signatures a sensible thing? E.g. regulatory.bin gets signed by Seth, then Kyle, then $DISTRO and any one key is enough to validate it. Thanks, -- Julian Calaby Email: julian.calaby@xxxxxxxxx Profile: http://www.google.com/profiles/julian.calaby/ -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
