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-rw-r--r-- | documentation/ref-manual/variables.rst | 36 |
1 files changed, 29 insertions, 7 deletions
diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst index 861b04eaab..5b5eaccc2a 100644 --- a/documentation/ref-manual/variables.rst +++ b/documentation/ref-manual/variables.rst | |||
@@ -3170,13 +3170,35 @@ system and gives an overview of their function and contents. | |||
3170 | :ref:`ref-classes-kernel-fitimage` class. | 3170 | :ref:`ref-classes-kernel-fitimage` class. |
3171 | 3171 | ||
3172 | :term:`FIT_SIGN_INDIVIDUAL` | 3172 | :term:`FIT_SIGN_INDIVIDUAL` |
3173 | If set to "1", then the :ref:`ref-classes-kernel-fitimage` | 3173 | If set to "1", the :ref:`ref-classes-kernel-fitimage` class signs each |
3174 | class will sign the kernel, dtb and ramdisk images individually in addition | 3174 | image node individually, including the kernel, DTB, RAM disk, and any |
3175 | to signing the FIT image itself. This could be useful if you are | 3175 | other image types present in the FIT image, in addition to signing the |
3176 | intending to verify signatures in another context than booting via | 3176 | configuration nodes. |
3177 | U-Boot. | 3177 | This can be useful if you need to verify signatures outside of the |
3178 | 3178 | U-Boot boot process. By default, this variable is set to "0". | |
3179 | This variable is set to "0" by default. | 3179 | |
3180 | If :term:`UBOOT_SIGN_ENABLE` is set to "1" and | ||
3181 | :term:`FIT_SIGN_INDIVIDUAL` remains at its default value of "0", only the | ||
3182 | configuration nodes are signed. Since configuration nodes include hashes | ||
3183 | of their referenced image nodes, the integrity of the entire FIT image is | ||
3184 | ensured as long as the image nodes are loaded via the configuration nodes | ||
3185 | and the hashes of the image nodes are checked. That's usually the case. | ||
3186 | |||
3187 | Enabling :term:`FIT_SIGN_INDIVIDUAL` typically increases complexity for | ||
3188 | little benefit. There might be exceptions such as image nodes that are | ||
3189 | not referenced by any configuration node or loaded directly for whatever | ||
3190 | reason. | ||
3191 | For most use cases, setting this variable to "0" provides sufficient | ||
3192 | security. | ||
3193 | |||
3194 | For further details, refer to the official U-Boot documentation: | ||
3195 | `U-Boot fit signature <https://docs.u-boot.org/en/latest/usage/fit/signature.html>`__ | ||
3196 | and more specifically at: | ||
3197 | `U-Boot signed configurations <https://docs.u-boot.org/en/latest/usage/fit/signature.html#signed-configurations>`__. | ||
3198 | |||
3199 | Signing only the image nodes is intentionally not implemented by | ||
3200 | :term:`OpenEmbedded-Core (OE-Core)`, as it is vulnerable to mix-and-match | ||
3201 | attacks. | ||
3180 | 3202 | ||
3181 | :term:`FIT_SIGN_NUMBITS` | 3203 | :term:`FIT_SIGN_NUMBITS` |
3182 | Size of the private key used in the FIT image, in number of bits. | 3204 | Size of the private key used in the FIT image, in number of bits. |