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Re: Yum deltarpm




On Jan 13, 2007, at 5:11 PM, Ahmed Kamal wrote:

We should be able to sign the drpms (not sure yet!) Reconstructing the new rpm from ondisk files, doesn't look bad security wise, because the new data is signed. If the on disk files are not trusted, this means the system is already compromised!

Installed files get modified for reasons other than a hacked system. Think about config files that the sysadmin edits after a package is installed. Think about documentation files, whose may not be installed at all. Think about dealing with file conflicts between installed packages. Run 'rpm -Va' on a sample of Fedora systems and tell me that all those changes just don't matter... And make sure to talk to a sysadmin who has had to recover from a rootkit-ed system, and tell them that the rootkit'd files will get rolled into their newly installed packages if drpm is enabled during recovery.

Relying on the integrity of installed files when generating and applying rpm diffs is just a bad idea, period. It's a hack that relies on hope instead of best practices, and it gives up the guarantees that are a substantial part of rpm's value. Any rpm delta solution must produce results that are identical to the original desired file, down to the last byte.

Maybe there is a clever way to use a network server and local installed files, along with the rsync algorithm, to generate a .rpm file that is guaranteed to be byte-for-byte identical to the desired file. Mix BitTorrent technology in there, and there is plenty of room for innovation without resorting to a really bad hack. :)

Best,
-- Elliot



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