Edward Tomasz Napierała
2017-Apr-08 11:11 UTC
Proposal for a design for signed kernel/modules/etc
On 0327T1354, Eric McCorkle wrote:> Hello everyone, > > The following is a design proposal for signed kernel and kernel module > loading, both at boot- and runtime (with the possibility open for signed > executables and libraries if someone wanted to go that route). I'm > interested in feedback on the idea before I start actually writing code > for it.I see two potential problems with this. First, our current loader(8) depends heavily on Forth code. By making it load modified 4th files, you can do absolutely anything you want; AFAIK they have unrestricted access to hardware. So you should preferably be able to sign them as well. You _might_ (not sure on this one) also want to be able to restrict access to some of the loader configuration variables. Second - given OpenSSL track record, moving signature verification and the x.509 stuff into the kernel (to verify userland) and loader (to verify the kernel and modules)... well, it just doesn't seem to be a good idea. Also: do you know about veriexec? https://reviews.freebsd.org/D8575
On 04/08/2017 07:11, Edward Tomasz Napiera?a wrote:> On 0327T1354, Eric McCorkle wrote: >> Hello everyone, >> >> The following is a design proposal for signed kernel and kernel module >> loading, both at boot- and runtime (with the possibility open for signed >> executables and libraries if someone wanted to go that route). I'm >> interested in feedback on the idea before I start actually writing code >> for it. > > I see two potential problems with this. > > First, our current loader(8) depends heavily on Forth code. By making > it load modified 4th files, you can do absolutely anything you want; > AFAIK they have unrestricted access to hardware. So you should preferably > be able to sign them as well. You _might_ (not sure on this one) also > want to be able to restrict access to some of the loader configuration > variables.Loader is handled by the UEFI secure boot framework, though the concerns about the 4th code are still valid. In a secure system, you'd want to do something about that, but the concerns are different enough (and it's isolated enough) that it could be done separately.> Second - given OpenSSL track record, moving signature verification > and the x.509 stuff into the kernel (to verify userland) and loader > (to verify the kernel and modules)... well, it just doesn't seem > to be a good idea.Integrating all of OpenSSL would be massively overkill. All you need is RSA/Ed25519 signature verification and parsing a subset of PKCS#7. My thoughts here are to grab the RSA/Ed25519 implementations from libsodium and just write a minimal PKCS#7 parser.> Also: do you know about veriexec? > > https://reviews.freebsd.org/D8575Is there some documentation of this other than a code review? -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: OpenPGP digital signature URL: <http://lists.freebsd.org/pipermail/freebsd-security/attachments/20170408/78a26da6/attachment.sig>