Security::_checkDir() validated file access using Smarty::_realpath(),
which only normalizes paths as strings and never follows symlinks. A
symlink placed inside a trusted secure_dir/template directory therefore
passed the trust check while file_get_contents() followed it to an
arbitrary file (e.g. /etc/passwd), affecting {include} and {fetch} of
local files.
Resolve the requested file with native realpath() and re-validate the
canonical, symlink-free path against the trusted directories. The trusted
directories are canonicalized the same way so legitimate symlinked
deployment paths (e.g. a Capistrano "current" release symlink, or macOS'
/var -> /private/var) keep working. Falls back to string normalization
only when the file does not yet exist on disk.
Adds regression tests covering both the rejected escape and an allowed
in-sandbox symlink, and documents the changelog convention in AGENTS.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Simon Wisselink