Messages in this thread | | | Subject | Re: [RFC 2/2] initramfs with digital signature protection | From | Mimi Zohar <> | Date | Fri, 12 Apr 2013 07:54:29 -0400 |
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On Thu, 2013-04-11 at 10:52 -0400, Vivek Goyal wrote: > On Wed, Apr 10, 2013 at 05:05:22PM -0400, Mimi Zohar wrote: > > On Wed, 2013-04-10 at 15:42 -0400, Vivek Goyal wrote: > > > On Tue, Apr 09, 2013 at 11:07:10PM -0400, Mimi Zohar wrote: > > > > > > [..] > > > > The module keyring is a special case. Loading these keys from the > > > > kernel and, presumably, locking the keyring is probably fine. In the > > > > case of IMA, however, files will be signed by any number of package > > > > owners. If the _ima keyring is locked by the kernel, how would you add > > > > these other keys? > > > > > > Who are package owners here. IOW, in typical IMA setup, where are the keys > > > and when are these keys loaded in ima keyring? > > > > Suppose I install third party packages not signed by the distro, but by > > the package owner (eg. google, rpmfusion, ...). Not only does the > > package signature need to be verified on installation, but the files > > need to be installed with signatures. For IMA to enforce file > > integrity, the package owner's public key needs to be added to the _ima > > keyring. > > Ok, got it. > > > > > > If we trust root and keys can be loaded any time later, then signed > > > initramfs will not solve the problem either. > > > > Locking the keyring in the kernel will limit the set of permitted keys > > to only those specified in UEFI db or builtin. Locking the keyring in > > the "early" initramfs, will allow the system owner, whose key is in the > > UEFI db, to specify additional keys, such as those for third party > > packages. Not all public keys belong in the UEFI db. > > Ok, so third party public key you don't want to add in UEFI db. Instead > platform owner (whose key is in UEFI db) will regenerate initrafs and > sign it. > > So above use case is primarily for user space files and verifying its > integrity and IMA keyring is used for that. secureboot does not require > IMA keyring to be locked as none of that code runs at ring0. > > This locking requirement of IMA keyring is coming in only because we are > trying to also verify the integrity of a process who will load code which > runs at ring0. > > So how do you like the idea of using another keyring (say system keyring) > for this purpose and what keyring to use integrity of a file can be > encoded in file signature. > > This is something similar to INTEGRITY_KEYRING_MODULE keyring for modules. > (Though I don't see this code fully hooked up yet). > > Or, given the fact that module signature and here /sbin/kexec verification > will make use of similar keys, we can create a system keyring, make module > code make use of that keyring. And IMA code can make use of that keyring > too if a file's digital signature indicates so.
Sounds good to me!
thanks,
Mimi
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