Messages in this thread | | | Date | Thu, 28 Feb 2013 23:48:06 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [GIT PULL] Load keys from signed PE binaries |
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On Thu, 21 Feb 2013, David Howells wrote:
> The way we have come up with to get around this is to embed an X.509 > certificate containing the key in a section called ".keylist" in an EFI PE > binary and then get the binary signed by Microsoft. The key can then be passed > to the kernel by passing the signed binary: > > keyctl padd asymmetric "" {ID of .system_keyring} <pekey.efi.signed
Please let me take this back to square one for a very short moment.
I completely fail to understand how your security model is dealing with this scenario:
- Mr. Evil Blackhat creates EFI PE binary from "int main() { return 42; }" (psuedo)code - Mr. Evil Blackhat puts his own key into .keylist section of this binary - Mr. Evil Blackhat goes through the $99 process of having this binary signed by Microsoft. They don't have a slightest reason not to sign it, as the binary obviously can't be used to run backdoored Windows - Mr. Evil Blackhat then uses keyctl to process this signed binary - Mr. Evil Blackhat modprobes i_own_your_ring0.ko which is signed by his key, and he instantly has his code running in your SecureBoot environment
Let me formulate my point more clearly -- Microsoft very likely going to sign hello world EFI PE binary, no matter the contents of .keylist section, as they don't give a damn about this section, as it has zero semantic value to them, right?
They sign the binary. By signing the binary, they are *NOT* establishing cryptographic chain of trust to the key stored in .keylist, but your patchset seems to imply so.
What am I missing?
Thanks,
-- Jiri Kosina SUSE Labs
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