Method writeFile

pkg/tools/builtin/filesystem/filesystem.go:705–714

writeFile is a TOCTOU-safe equivalent of [os.WriteFile]. See [readFile] for the contract. The call is rejected by the kernel when any component of rel is an out-of-root symlink, so an attacker cannot win the swap race between the [resolveAndCheckPath] check and the write.

(resolved string, data []byte, perm os.FileMode)

// of rel is an out-of-root symlink, so an attacker cannot win the swap
// race between the [resolveAndCheckPath] check and the write.
func (t *ToolSet) writeFile(resolved string, data []byte, perm os.FileMode) error {
	root, rel, err := t.rootedAccess(resolved)
	if err != nil {
		return err
	}
	if root != nil {
		return root.WriteFile(rel, data, perm)
	}
	return os.WriteFile(resolved, data, perm)
}

// stat is a TOCTOU-safe equivalent of [os.Stat]. See [readFile] for the
// contract.