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authorSascha Hauer <s.hauer@pengutronix.de>2015-11-12 10:31:28 +0100
committerRichard Weinberger <richard@nod.at>2015-11-12 10:50:04 +0100
commit803b8ddbaea4f049cbf360682e80bc2f1aea12e2 (patch)
treef9a3402d1260a84fd51cb46822fd89b0ea63db18 /tests/jittertest/README
parent50044efbd6e713e86f705a60eddab0c034dffeba (diff)
mkfs.ubifs: Optionally create extended attribute with inode number
This is done to allow creating images suitable for IMA directory appraisal. IMA creates a hash for directories and attaches this hash to the directory itself as an extended attribute. Among other things the inode numbers of the files are hashed. So, to create a valid hash in the UBIFS image the evmctl tool needs to know the inode numbers which the files in the UBIFS image will have. evmctl will read the inode numbers from the user.image-inode-number extended attribute. Since extended attributes are inodes themselves the inode numbers for the generated image will change when the extended attributes change, so to generate a correctly hashed UBIFS image, both evmctl and mkfs.ubifs must be run twice: 1) execute evmctl to iterate over the directory tree. This will create the security.ima and security.evm extended attributes. The existence of the attributes makes sure that subsequent calls to mkfs.ubifs will use the same inode numbers. evmctl will use the inode numbers from the host filesystem in this step which makes the resulting image unusable 2) execute mkfs.ubifs -a. This will create the user.image-inode-number extended attributes on files/directories added to the image. 3) execture evmctl again. This time evmctl will pick the inode numbers from the user.image-inode-number extended attribute instead of the ones from the host filesystem 4) execute mkfs.ubifs again. This will create the correct image. The now existing user.image-inode-number extended attributes are ignored and not added to the image. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> Signed-off-by: Richard Weinberger <richard@nod.at>
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