Security review of 4788ca4 (inline python link classifier):
1. Names like cpmove-x/./homedir/mail/..., homedir//mail, homedir/../homedir
or /cpmove-x/... were matched differently by the classifier than by tar,
so a mail-tree symlink could escape the strip (measured: the dot, dslash
and abs fixtures extracted with exit 0 on 4788ca4).
2. A newline in a member name split one --exclude-from pattern in two.
Moved the policy to scripts/lib/mail-tree-links.py:
- scan (pre-extract, an optimisation): REFUSES the archive (exit 3) on any
control character in a member name or link target, or any non-canonical
member name / hard-link target (absolute, '..', or normpath() differing
after one leading './'). Symlink targets are not canonical-checked:
ordinary cPanel links (../public_html) are legitimate outside the mail
tree, and every symlink inside it is stripped anyway.
- verify (post-extract, the authority): lstat-walks each mail tree; exit 4
on any symlink, or any regular file whose st_nlink exceeds its names
inside that same mail tree (a link leaving it). In-tree Dovecot hard-link
copies (maildir_copy_with_hardlinks) are kept; a blanket nlink>1 refusal
would drop real mail.
- Fixtures: cpmove-bad-{dot,dslash,dotdot,abs,newline}; verify tests for
symlinks and hard links into/out of/between mail trees surviving the
pre-filter. 14 of the new checks fail on 4788ca4.
Only in IMPORT_INCLUDE_MAIL=true mode; the default path is unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
shadowdaoandClaude Opus 5.5
52b1e656c3