Adopt #555: constrain tar driver paths to image root#3
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…ontainerTools#555) Adopt upstream security fix that confines tar driver path resolution to the extracted image root, preventing tar-slip and symlink-escape attacks where archive entries reference paths outside the image filesystem. Upstream-PR: GoogleContainerTools#555 Co-authored-by: Francesco Sabiu <fsabiu@users.noreply.github.com>
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Adopts upstream googlecontainertools/container-structure-test#555 ("Constrain tar driver paths to image root", by Francesco Sabiu) as a single commit.
The tar driver previously let archive entries resolve to paths outside the extracted image root. A file, symlink, or hardlink entry could point past the root and the driver would follow it, so a crafted image could read or write host paths during a structure test. That is the tar-slip / symlink-escape class of bug.
The fix adds
internal/pkgutil/root_path.go, a resolver that pins every entry path to the image root and rejects anything that escapes, including escapes that only show up after following a symlink or hardlink chain.internal/pkgutil/tar_utils.go(the unpack path) andpkg/drivers/tar_driver.gonow route their path handling through it.The tests in
internal/pkgutil/tar_utils_test.gocover both halves: entries that escape the root are rejected, entries that stay inside resolve normally. Cases include plain files, symlinks, hardlinks, a hardlink pointing at a symlink (which must not be followed), and a hardlink whose source symlink escapes.pkg/drivers/tar_driver_test.gois added alongside.Verified against the go1.26.4 Nix toolchain:
go build ./...clean, all six new pkgutil tests pass, andgo test ./internal/pkgutil/... ./pkg/drivers/...reportsokfor both.go vet ./...surfaces only two findings, both inpkg/drivers/host_driver.go:90andpkg/types/v1/file_existence.go:59, both pre-existing and untouched by this change.