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fix(core)!: stop trusting pre-existing symlinks in extraction destination - #816
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…tion Replace the directory cache with a per-component lstat walker so that every parent component below the destination is verified on each entry write. Pre-existing symlinks are refused by default; with symlinks allowed they are accepted only when they resolve inside the destination. Skip parent canonicalization when the parent is the destination root and refuse symlinked final components on non-Unix targets. BREAKING CHANGE: EntryValidator::validate_entry no longer takes a dir_cache argument, and ValidationContext no longer carries a lifetime parameter.
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Summary
Extraction previously cached directories it had "created" and trusted them for the rest of the run. A symlink already present in the destination was treated as such a directory, so entries could be written outside the destination.
DirCachewithDirWalker, which runslstaton every component below the destination for each entry write.SafePathno longer trusts the parent; the parent is canonicalized on every entry except when it is the destination root.Behavior change
By default extraction now fails if any component below the destination is a symlink, even one pointing inside the destination.
--allow-symlinksrestores that for contained links. A symlink as the destination root itself is still accepted.Breaking changes
EntryValidator::validate_entryno longer takes adir_cacheargument.ValidationContextno longer has a lifetime parameter.Known limitations
lstatand the write. Closing this fully requiresopenatfrom a pinned directory fd (follow-up).lstatand parent canonicalization; benchmarks were noisy and need a re-run on an idle machine.Test plan
tests/preexisting_dest_symlink.rsfor TAR, ZIP and 7z: directory entry through a link, intermediate component, no directory entries,--forceoverwrite, re-extraction, swap during extraction,--allow-symlinkswith an escaping link.cargo deny.