Howto read a file off disk?

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Omen.Wildat_private

I'm writing a LSM to implement part of Tripwire's functionality at
runtime, specifically, SHA1 checking.  What I want to do is verify the
SHA1 hash of the file that being opened is the same as a previously
computed hash.  I want to ensure (when they are opened) that files have
not been modified from their previous contents.

I've successfully tapped the kernel at the inode_permission security
check.  This gives me what I want, and I have everything set up, except
for actually reading the contents of the file off disk and feeding them
to the hash function.  Can anyone give me some pointers for how to read
a file's contents when what I have is an inode?

Thanks,
   Omen

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