A small text in docs/uefi/uefi.rst was added to explain how we can configure and utilise UEFI secure boot feature on U-Boot.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- doc/uefi/uefi.rst | 77 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+)
diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst index a8fd886d6b5e..98cd770aefe5 100644 --- a/doc/uefi/uefi.rst +++ b/doc/uefi/uefi.rst @@ -97,6 +97,83 @@ Below you find the output of an example session starting GRUB::
See doc/uImage.FIT/howto.txt for an introduction to FIT images.
+Configuring UEFI secure boot +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +UEFI specification[1] defines a secure way of executing UEFI images +by verifying a signature (or message digest) of image with certificates. +This feature on U-Boot is enabled with:: + + CONFIG_UEFI_SECURE_BOOT=y + +To make the boot sequence safe, you need to establish a chain of trust; +In UEFI secure boot, you can make it with the UEFI variables, "PK" +(Platform Key), "KEK" (Key Exchange Keys), "db" (white list database) +and "dbx" (black list database). + +There are many online documents that describe what UEFI secure boot is +and how it works. Please consult some of them for details. + +Here is a simple example that you can follow for your initial attempt +(Please note that the actual steps would absolutely depend on your system +and environment.): + +1. Install utility commands on your host + * openssl + * efitools + * sbsigntool + +2. Create signing keys and key database files on your host + for PK:: + + $ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=TEST_PK/ \ + -keyout PK.key -out PK.crt -nodes -days 365 + $ cert-to-efi-sig-list -g 11111111-2222-3333-4444-123456789abc \ + PK.crt PK.esl; + $ sign-efi-sig-list -c PK.crt -k PK.key PK PK.esl PK.auth + + for KEK:: + + $ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=TEST_KEK/ \ + -keyout KEK.key -out KEK.crt -nodes -days 365 + $ cert-to-efi-sig-list -g 11111111-2222-3333-4444-123456789abc \ + KEK.crt KEK.esl + $ sign-efi-sig-list -c PK.crt -k PK.key KEK KEK.esl KEK.auth + + for db:: + + $ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=TEST_db/ \ + -keyout db.key -out db.crt -nodes -days 365 + $ cert-to-efi-sig-list -g 11111111-2222-3333-4444-123456789abc \ + db.crt db.esl + $ sign-efi-sig-list -c KEK.crt -k KEK.key db db.esl db.auth + + Copy *.auth to media, say mmc, that is accessible from U-Boot. + +3. Sign an image with one key in "db" on your host:: + + $ sbsign --key db.key --cert db.crt helloworld.efi + +4. Install keys on your board:: + + ==> fatload mmc 0:1 <tmpaddr> PK.auth + ==> setenv -e -nv -bs -rt -at -i <tmpaddr>,$filesize PK + ==> fatload mmc 0:1 <tmpaddr> KEK.auth + ==> setenv -e -nv -bs -rt -at -i <tmpaddr>,$filesize KEK + ==> fatload mmc 0:1 <tmpaddr> db.auth + ==> setenv -e -nv -bs -rt -at -i <tmpaddr>,$filesize db + +5. Set up boot parameters on your board:: + + ==> efidebug boot add 1 HELLO mmc 0:1 /helloworld.efi.signed "" + +Then your board runs that image from Boot manager (See below). +You can also try this sequence by running Pytest, test_efi_secboot, +on sandbox:: + + $ cd <U-Boot source directory> + $ pytest.py test/py/tests/test_efi_secboot/test_signed.py --bd sandbox + Executing the boot manager ~~~~~~~~~~~~~~~~~~~~~~~~~~