Messages in this thread | | | From | (Eric Brunet) | Date | Mon, 18 Oct 1999 14:21:30 +0200 (MET DST) | Subject | Re: crypto and fsck guys. |
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In ens.rezo.mailing-lists.linux-kernel, you wrote: >> I have just lost _ABSOLUELY_ everything >> of importance to myself. The reason? put > >Actually to be brutal the reason is because you didnt make a backup. > A friend of mine tried once to make backups of an encrypted filesystem. That looked easy: just put on a tape/zip/whatever the file containing the encrypted filesystem. He found out however that that was not doable: each block of data is encrypted using a seed which is the __absolute__ block number of the underlying filesystem, where it should be the block number __relative__ to the beginning of the file containing the encrypted filesystem. The consequence is that if you try to restore a backup (or simply if you try to copy the encrypted filesystem), you obtain something which cannot be decrypted as the block numbers have changed since the encryption.
My friend submitted a bug report to the maintainer, and was replied that ``the feature was known, but would not be corrected because it wwas imported to support backward compatibility with already existing filesystems.'' Sigh.
>fsck actually doesn't even know about encrypted data. The encrypt/decrypt >happens below the level either it or the file system code sees. If you >tried to fsck the crypted data not the uncrypted loopback I imagine >e2fsck would think your fs was quite odd however. > It is indeed weird that e2fsck doesn't give up at once before writing anything.
Éric Brunet
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