sign-efi-sig-list - Online in the Cloud

PROGRAM:

NAME

sign-efi-sig-list - signing tool for secure variables as EFI Signature Lists

SYNOPSIS

sign-efi-sig-list [-r] [-m] [-a] [-g <guid>] [-o] [-t <timestamp>] [-i <infile>] [-c <crt
file>] [-k <key file>] <var> <efi sig list file> <output file>

DESCRIPTION

Produce an output file with an authentication header for direct update to a secure
variable. This output may be signed by the usual keys directly or may be split for
external signing using the -o and -i options.

OPTIONS

-r the certificate is rsa2048 rather than x509 [UNIMPLEMENTED]

-m Use a monotonic count instead of a timestamp [UNIMPLEMENTED]

-a Prepare the variable for APPEND_WRITE rather than replacement

-o Do not sign, but output a file of the exact bundle to be signed

-t <timestamp>
Use <timestamp> as the timestamp of the timed variable update If not present, then
the timestamp will be taken from system time. Note you must use this option when
doing detached signing otherwise the signature will be incorrect because of
timestamp mismatches.

-i <infile>
take a detached signature (in PEM format) of the bundle produced by -o and complete
the creation of the update

-g <guid>
Use <guid> as the signature owner GUID

-c <crt>
<crt> is the file containing the signing certificate in PEM format

-k <key>
<key> is the file containing the key for <crt> in PEM format

EXAMPLES

To sign a simple append update to db which has been prepared as an EFI Signature List in
DB.esl and output the result with the authentication header in DB.auth

sign-efi-sig-list -a -c KEK.crt -k KEK.key db DB.esl DB.auth

To do a detached signature in the same way

sign-efi-sig-list -a -t 'Jul 21 09:39:37 BST 2012' -o db DB.esl DB.forsig

Now sign the DB.forsig file in the standard openssl way. Note that the standards require
sha256 as the signature algorithm

openssl smime -sign -binary -in DB.forsig -out DB.signed -signer KEK.crt -inkey KEK.key
-outform DER -md sha256

Which produces a detached PKCS7 signature in DB.signed. Now feed this back into the
program remembering to keep the same timestamp (and the -a flag):

sign-efi-sig-list -a -i DB.signed -t 'Jul 21 09:39:37 BST 2012' db DB.auth

To delete a key, simply sign an empty EFI signature list file, so to produce an variable
update that will delete the PK:

> null.esl

And then sign it in the standard way (must not be an append write update):

sign-efi-sig-list -c PK.crt -k PK.key PK null.esl PK.auth

Once you have the .auth file conveyed to the UEFI platform, you can use the UpdateVars.efi
program to apply it

UpdateVars [-a] db DB.auth

Where the -a flag must be present if the DB.auth file was created as an append write
update and absent if its replacing the variable.

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