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| -rw-r--r-- | doc/uImage.FIT/signature.txt | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/doc/uImage.FIT/signature.txt b/doc/uImage.FIT/signature.txt index 61a72db3c74..c71280b63bb 100644 --- a/doc/uImage.FIT/signature.txt +++ b/doc/uImage.FIT/signature.txt @@ -382,6 +382,32 @@ verified later even if the FIT has been signed with other keys in the meantime. +Details +------- +The signature node contains a property ('hashed-nodes') which lists all the +nodes that the signature was made over. The image is walked in order and each +tag processed as follows: +- DTB_BEGIN_NODE: The tag and the following name are included in the signature + if the node or its parent are present in 'hashed-nodes' +- DTB_END_NODE: The tag is included in the signature if the node or its parent + are present in 'hashed-nodes' +- DTB_PROPERTY: The tag, the length word, the offset in the string table, and + the data are all included if the current node is present in 'hashed-nodes' + and the property name is not 'data'. +- DTB_END: The tag is always included in the signature. +- DTB_NOP: The tag is included in the signature if the current node is present + in 'hashed-nodes' + +In addition, the signature contains a property 'hashed-strings' which contains +the offset and length in the string table of the strings that are to be +included in the signature (this is done last). + +IMPORTANT: To verify the signature outside u-boot, it is vital to not only +calculate the hash of the image and verify the signature with that, but also to +calculate the hashes of the kernel, fdt, and ramdisk images and check those +match the hash values in the corresponding 'hash*' subnodes. + + Verification ------------ FITs are verified when loaded. After the configuration is selected a list |