Podcasts Other Chaos Computer Club - recent events feed Making a magic deduplicating tar using the FICLONE ioctl (asg2023)

Making a magic deduplicating tar using the FICLONE ioctl (asg2023)

Published: Sept. 13, 2023, 3 p.m.

A walkthrough of an interesting use case for the `FICLONE` ioctl: cloning file data into a tar archive, and cloning files out of it again. "Free" archiving and unarchiving at zero-copy speeds!\nTopics:\n\n- Copy-on-write and the `FICLONE` ioctl\n- The ancient `tar` format\n- A trick for adding arbitrary padding to the `tar` format in order to force file system page alignment\n- How to avoid symlink attacks and other TOCTOU issues, using the fairly recently introduced (linux 5.6) `openat2` system call.\n- An interesting bug in GNU tar\n\nAt the end you'll receive a free autographed copy of [deduptar](https://git.sr.ht/~nullenenenen/deduptar/tree/master/item/README.md) to use for party tricks. \U0001f973\nabout this event: https://cfp.all-systems-go.io/all-systems-go-2023/talk/99PZDY/