[SECURITY] apc import copies skill directories without name sanitization

[FZ2000]

Severity: P2

Summary

The apc import command copies skill directories from an export archive using raw filesystem names (src.name) without calling sanitize_skill_name(). This creates an asymmetry with apc install, which enforces the regex ^[A-Za-z0-9][A-Za-z0-9_\-]{0,63}$.

A crafted export archive can install skills with names that would be rejected by apc install.

Affected Code

src/export_import.py:

for src in sorted(import_skills_dir.iterdir()):
    if src.is_dir() and (src / "SKILL.md").exists():
        dst = skills_dir / src.name    # <-- no sanitize_skill_name() call
        if dst.exists():
            shutil.rmtree(dst)
        shutil.copytree(src, dst)

Compare to apc install (src/install.py), which calls sanitize_skill_name(skill["name"]) before writing.

Problematic Names Importable via Crafted Archive

• .hidden-skill (dotfile in ~/.apc/skills/)
• Skills with spaces or special characters in directory names
• Names longer than 64 characters
• Names starting with digits or underscores

Impact

• Inconsistent state in the skills directory with names that violate the expected invariant
• Dotfile skill directories could interfere with tool detection or glob patterns
• May bypass future enforcement that relies on the regex invariant being maintained
• While full path traversal via ../ is prevented by the OS (can't have / in filename), the weaker invariants allow edge cases

Recommended Fix

from skills import sanitize_skill_name

for src in sorted(import_skills_dir.iterdir()):
    if src.is_dir() and (src / "SKILL.md").exists():
        try:
            safe_name = sanitize_skill_name(src.name)
        except ValueError as e:
            warning(f"Skipping skill with invalid name {src.name!r}: {e}")
            continue
        dst = skills_dir / safe_name
        if dst.exists():
            shutil.rmtree(dst)
        shutil.copytree(src, dst)
        count += 1

References

• CWE-20: Improper Input Validation