lib/tar: Pre-filter tar archive in Rust#112
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cgwalters
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| // Completely discard stuff outside of /usr | ||
| if !(matches!(path.as_str(), "/" | "/usr") || path.starts_with("usr/")) { | ||
| continue; |
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I'd throw a warn!() in here. I'm pretty sure we'll discover a good bunch of nasty things.
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Good point, though since this is a library we should probably allow the caller to collect this data and log/print it however it wants.
Will look at that.
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In the bigger picture I am currently thinking of this as a shortcut - longer term we'll strongly encourage the model in #12 (comment) where we have a required RUN ostree container-finalize-bootable incantation that will clean this stuff up at build time.
Rather than trying to extend the ostree C code to support arbitrary transformations, let's do pre-parsing here in safe Rust. We keep the `/etc` → `/usr/etc` bits, but we also just completely drop everything not in `/usr` now. As noted in the comment, this pre-validation will hopefully also catch any corrupt tarballs that might be exploitable in the C libarchive codebase.
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OK, that was a fun deep dive into path libraries in Rust, specifically the components method. We now parse, normalize and filter the input path in a much more robust way, and this updated code now also returns a btreemap from "prefix -> number of filtered paths" which should be sufficient to start. |
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| /// A [`std::io::Write`] implementation backed by an asynchronous source. |
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Hmm, what we should really do here actually is store the metadata about filtered paths in the commit object. However, doing that would require splitting up the write/commit phases, which in turn really wants us to be doing all of this natively in Rust instead of forking off |
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Any other comments on this, or good to go? |
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All good from my side 👍. As (very subjective) feedback on your last comment, I don't personally feel the need to record that information persistently. It can be interesting to log and inspect it at runtime, but in the steady state I guess it's unlikely that we'd want to parse/analyze that from the commit object itself. |
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Rather than trying to extend the ostree C code to support
arbitrary transformations, let's do pre-parsing here in safe Rust.
We keep the
/etc→/usr/etcbits, but we also just completelydrop everything not in
/usrnow.As noted in the comment, this pre-validation will hopefully also
catch any corrupt tarballs that might be exploitable in the C libarchive
codebase.