harden: secure extension and preset archive downloads (#3141)

* harden: secure extension and preset archive downloads

Adopt the shared download-security primitives from #3140 across extension and
preset catalog, package, direct-URL, and ZIP-install flows:

- bound catalog, package, and inline manifest reads;
- verify catalog SHA-256 values when present;
- replace path-only extraction with bounded traversal/symlink-safe extraction;
- validate malformed hosts and ports before opening download URLs;
- handle normalized trailing-backslash directory entries consistently.

Redirect enforcement and checksum verification remain owned by the shared
helpers already on main; this commit wires them into extension and preset
behavior.

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

* harden: close archive and catalog download edge cases

Preflight ZIP central directories before ZipFile allocates them, bound both
declared and actual payload sizes, and reject ambiguous or non-portable archive
paths before extraction.

Keep extension update manifest selection consistent with extraction, reject
unsafe catalog-derived output filenames and malformed URL types, and escape
untrusted values in download errors.

Add regression coverage for parser differentials, collisions, platform-specific
filenames, bounded call sites, and failure ordering.

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

* harden: address download security review feedback

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

* harden: close ZIP preflight review gaps

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

* fix: harden extension update preflight and rollback

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

* fix: harden extension update rollback

Assisted-by: OpenAI Codex (model: GPT-5, autonomous)

src/specify_cli/_utils.py

@@ -12,6 +12,7 @@ import yaml
 from pathlib import Path, PurePosixPath, PureWindowsPath
 from typing import Any
 from ._console import console
+from ._download_security import normalize_zip_member_name
 
 CLAUDE_LOCAL_PATH = Path.home() / ".claude" / "local" / "claude"
 CLAUDE_NPM_LOCAL_PATH = Path.home() / ".claude" / "local" / "node_modules" / ".bin" / "claude"
@@ -27,19 +28,22 @@ def relative_extension_path_violation(value: Any) -> str | None:
     ``None`` when it is an acceptable relative path within the extension
     directory.
 
-    Policy: the value must be a non-empty string with no leading/trailing
-    whitespace, no absolute/anchored form, and no ``..`` traversal. The value is
+    Policy: the value must be a non-empty, portable file path with no
+    leading/trailing whitespace, absolute/anchored form, ``..`` traversal,
+    platform-reserved component, or directory-only suffix. The value is
     evaluated under both POSIX and Windows path semantics because a native
     ``Path`` is OS-dependent (a ``PurePosixPath`` on POSIX does not interpret
-    Windows drive/UNC forms, and ``C:foo`` is anchored but not ``is_absolute()``
-    yet resolves against the CWD on its drive). Rejecting any non-empty anchor
-    covers POSIX-absolute (``/abs``), Windows drive-relative (``C:foo``), Windows
-    absolute (``C:\\foo``), and UNC/rooted forms.
+    Windows drive/UNC forms, and ``C:foo`` is anchored but not
+    ``is_absolute()`` yet resolves against the CWD on its drive). Rejecting any
+    non-empty anchor covers POSIX-absolute (``/abs``), Windows drive-relative
+    (``C:foo``), Windows absolute (``C:\\foo``), and UNC/rooted forms.
     """
     if not isinstance(value, str) or not value:
         return "must be a non-empty string"
     if value.strip() != value:
         return "must not have leading or trailing whitespace"
+    if "\\" in value:
+        return "must use forward slashes as path separators"
     posix_path = PurePosixPath(value)
     win_path = PureWindowsPath(value)
     if (
@@ -52,6 +56,15 @@ def relative_extension_path_violation(value: Any) -> str | None:
             "must be a relative path within the extension directory "
             "(no absolute paths, drive letters, or '..' segments)"
         )
+    if value.endswith(("/", "\\")):
+        return "must name a file or command, not a directory"
+    try:
+        normalize_zip_member_name(value)
+    except ValueError:
+        return (
+            "must use portable path components "
+            "(no reserved names or platform-invalid characters)"
+        )
     return None