Secureboot: Image signing verification enhancements #3989
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@ycoheNvidia since you contributed the signing validation for sonic images, can you review this PR modification? |
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Adding @davidpil2002 @DavidZagury @Yarden-Z as well |
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The DB Key is not guaranteed to be a CARoot. It is possible to have the DB Key be an intermediate as it is trusted via the EFI signing methods which do not use the normal PKI methodology. This adds a secondary signing verification, the original plus the above described method. Signed-off-by: Brad House <[email protected]>
Signed-off-by: Travis Brown <[email protected]>
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@qiluo-msft - could you please help with the review? |
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What I did
The current signature verification of sonic images assumes the DB Keys are all Root CAs. The secureboot standard says nothing about this, the DBKeys are explicitly trusted by signing them with the KEK, and that signing method does not follow the standard X.509 PKI architecture. Therefore the DB Key is not guaranteed to be a CA Root (aka not self-signed). It is possible the DB Key was created as an intermediate, but since it is explicitly trusted that is ok.
Fixes sonic-net/sonic-buildimage#23406
How I did it
This adds this explicit trust of the DB Key as a secondary signing verification if the original verification fails. It disables looking inside the pkcs7 container for any keys at all and assumes the key specified is the exact key for the signature.
How to verify it
Build secureboot image signed with a DB Key that is not self-signed, then run through the sonic-installer install with that image and see the verification succeeds.
Previous command output (if the output of a command-line utility has changed)
New command output (if the output of a command-line utility has changed)