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| -rw-r--r-- | doc/uefi/uefi.rst | 110 |
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diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst index a35fbd3..4fda00d 100644 --- a/doc/uefi/uefi.rst +++ b/doc/uefi/uefi.rst @@ -100,79 +100,93 @@ 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 +The 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). +In UEFI secure boot the chain trust is defined by the following UEFI variables -There are many online documents that describe what UEFI secure boot is -and how it works. Please consult some of them for details. +* PK - Platform Key +* KEK - Key Exchange Keys +* db - white list database +* dbx - black list database -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.): +An in depth description of UEFI secure boot is beyond the scope of this +document. Please, refer to the UEFI specification and available online +documentation. Here is a simple example that you can follow for your initial +attempt (Please note that the actual steps will depend on your system and +environment.): -1. Install utility commands on your host - * openssl - * efitools - * sbsigntool +Install the required tools on your host -2. Create signing keys and key database files on your host - for PK:: +* openssl +* efitools +* sbsigntool - $ 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 +Create signing keys and the key database on your host: - for KEK:: +The platform key - $ 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 +.. code-block:: bash - for db:: + 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 - $ 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 +The key exchange keys - Copy \*.auth to media, say mmc, that is accessible from U-Boot. +.. code-block:: bash -3. Sign an image with one key in "db" on your host:: + 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 - $ sbsign --key db.key --cert db.crt helloworld.efi +The whitelist database -4. Install keys on your board:: +.. code-block:: bash - ==> 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 + $ 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 -5. Set up boot parameters on your board:: +Copy the \*.auth files to media, say mmc, that is accessible from U-Boot. - ==> efidebug boot add 1 HELLO mmc 0:1 /helloworld.efi.signed "" +Sign an image with one of the keys in "db" on your host -Then your board runs that image from Boot manager (See below). +.. code-block:: bash + + sbsign --key db.key --cert db.crt helloworld.efi + +Now in U-Boot install the 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 + +Set up boot parameters on your board:: + + efidebug boot add 1 HELLO mmc 0:1 /helloworld.efi.signed "" + +Now your board can run the signed image via the boot manager (see below). You can also try this sequence by running Pytest, test_efi_secboot, -on sandbox:: +on the sandbox + +.. code-block:: bash - $ cd <U-Boot source directory> - $ pytest.py test/py/tests/test_efi_secboot/test_signed.py --bd sandbox + cd <U-Boot source directory> + pytest.py test/py/tests/test_efi_secboot/test_signed.py --bd sandbox Executing the boot manager ~~~~~~~~~~~~~~~~~~~~~~~~~~ |