feat(extensions): verify catalog archive sha256 before install

extensions/EXTENSION-PUBLISHING-GUIDE.md

@@ -320,6 +320,7 @@ A: Extensions should be free and open-source. Commercial support/services are al
   "author": "string (required)",
   "version": "string (required, semver)",
   "download_url": "string (required, valid URL)",
+  "sha256": "string (optional, SHA-256 hex digest of the archive at download_url; verified before install)",
   "repository": "string (required, valid URL)",
   "homepage": "string (optional, valid URL)",
   "documentation": "string (optional, valid URL)",

presets/PUBLISHING.md

@@ -185,6 +185,7 @@ Edit `presets/catalog.community.json` and add your preset.
       "author": "Your Name",
       "version": "1.0.0",
       "download_url": "https://github.com/your-org/spec-kit-preset-your-preset/archive/refs/tags/v1.0.0.zip",
+      "sha256": "OPTIONAL: SHA-256 hex digest of the archive above; verified before install",
       "repository": "https://github.com/your-org/spec-kit-preset-your-preset",
       "license": "MIT",
       "requires": {

src/specify_cli/extensions/__init__.py

@@ -31,6 +31,7 @@
 from .._utils import dump_frontmatter, relative_extension_path_violation
 from ..catalogs import CatalogEntry as BaseCatalogEntry
 from ..catalogs import CatalogStackBase
+from ..shared_infra import verify_archive_sha256
 
 _FALLBACK_CORE_COMMAND_NAMES = frozenset(
     {
@@ -2617,6 +2618,10 @@ def download_extension(
             ) as response:
                 zip_data = response.read()
 
+            verify_archive_sha256(
+                zip_data, ext_info.get("sha256"), extension_id, ExtensionError
+            )
+
             zip_path.write_bytes(zip_data)
             return zip_path
 

src/specify_cli/presets/__init__.py

@@ -31,6 +31,7 @@
 from .._init_options import is_ai_skills_enabled
 from ..integrations.base import IntegrationBase
 from .._utils import dump_frontmatter
+from ..shared_infra import verify_archive_sha256
 
 
 def _substitute_core_template(
@@ -2505,6 +2506,10 @@ def download_pack(
             with self._open_url(download_url, timeout=60, extra_headers=extra_headers) as response:
                 zip_data = response.read()
 
+            verify_archive_sha256(
+                zip_data, pack_info.get("sha256"), pack_id, PresetError
+            )
+
             zip_path.write_bytes(zip_data)
             return zip_path
 

src/specify_cli/shared_infra.py

@@ -2,6 +2,9 @@
 
 from __future__ import annotations
 
+import hashlib
+import hmac
+import logging
 import os
 import re
 import tempfile
@@ -11,6 +14,74 @@
 from .integrations.base import IntegrationBase
 from .integrations.manifest import IntegrationManifest
 
+logger = logging.getLogger(__name__)
+
+# Matches a SHA-256 digest in its normalized form: exactly 64 hexadecimal
+# characters. Callers lowercase the declared value before matching (see
+# ``expected_hex = raw.lower()`` below), so an uppercase digest is accepted and
+# normalized rather than rejected.
+_SHA256_HEX_RE = re.compile(r"^[0-9a-f]{64}$")
+
+
+def verify_archive_sha256(
+    data: bytes,
+    expected: str | None,
+    name: str,
+    error_cls: type[Exception],
+) -> None:
+    """Verify downloaded archive bytes against a catalog-declared SHA-256.
+
+    Catalog entries may pin the expected digest of their release archive in a
+    ``sha256`` field (optionally prefixed with ``"sha256:"``). When present, the
+    downloaded bytes must match before they are written to disk and installed,
+    so a corrupted or tampered archive is rejected even though the transport was
+    HTTPS. Entries without a declared digest are accepted unchanged, keeping the
+    check backwards compatible.
+
+    Args:
+        data: The raw downloaded archive bytes.
+        expected: The catalog-declared SHA-256 hex digest, or ``None``.
+        name: The extension/preset id, used in the error message.
+        error_cls: Exception type to raise on mismatch (e.g. ``ExtensionError``).
+
+    Raises:
+        error_cls: If ``expected`` is provided and is not a well-formed
+            SHA-256 hex digest, or does not match ``data``.
+    """
+    # Skip only when no digest is declared at all (``None``). A declared but
+    # empty/blank value (e.g. ``sha256: ""``) is an authoring error, not an
+    # opt-out: let it fall through to the format check below so it is rejected
+    # rather than silently disabling verification.
+    if expected is None:
+        logger.debug(
+            "No sha256 declared for %r; archive integrity was not verified.",
+            name,
+        )
+        return
+    # Strip *only* a literal ``sha256:`` algorithm prefix (case-insensitive).
+    # Any other prefix is part of the value and must not be silently dropped,
+    # otherwise a malformed or wrong-algorithm digest (e.g. ``md5:...``) would
+    # be quietly accepted as if it were a valid SHA-256.
+    raw = str(expected).strip()
+    if raw[:7].lower() == "sha256:":
+        raw = raw[7:].strip()
+    expected_hex = raw.lower()
+    if not _SHA256_HEX_RE.match(expected_hex):
+        raise error_cls(
+            f"Invalid sha256 declared for {name!r}: expected 64 hexadecimal "
+            f"characters (optionally prefixed with 'sha256:'), got "
+            f"{expected!r}."
+        )
+    actual_hex = hashlib.sha256(data).hexdigest()
+    # Constant-time comparison: both sides are fixed-length hex digests, so use
+    # ``hmac.compare_digest`` to avoid leaking information through timing.
+    if not hmac.compare_digest(actual_hex, expected_hex):
+        raise error_cls(
+            f"Integrity check failed for {name!r}: the catalog declares "
+            f"sha256 {expected_hex}, but the downloaded archive is "
+            f"{actual_hex}. The archive may be corrupted or tampered with."
+        )
+
 
 class SymlinkedSharedPathError(ValueError):
     """Raised when a shared infrastructure path or ancestor is a symlink.

tests/test_extensions.py

@@ -3716,6 +3716,89 @@ def fake_open(req, timeout=None):
         assert captured[1].get_header("Authorization") == "Bearer ghp_testtoken"
         assert captured[1].get_header("Accept") == "application/octet-stream"
 
+    def _make_zip_bytes(self):
+        """Build a minimal valid extension ZIP in memory for download tests."""
+        import zipfile
+        import io
+
+        buf = io.BytesIO()
+        with zipfile.ZipFile(buf, "w") as zf:
+            zf.writestr("extension.yml", "id: test-ext\nname: Test\nversion: 1.0.0\n")
+        return buf.getvalue()
+
+    def _mock_response(self, data):
+        """Build a context-manager mock HTTP response returning ``data``."""
+        from unittest.mock import MagicMock
+
+        resp = MagicMock()
+        resp.read.return_value = data
+        # Configure the context-manager protocol explicitly so `with resp`
+        # yields `resp` itself, independent of how the protocol is invoked.
+        resp.__enter__.return_value = resp
+        resp.__exit__.return_value = False
+        return resp
+
+    def test_download_extension_accepts_matching_sha256(self, temp_dir):
+        """A catalog ``sha256`` that matches the archive is accepted."""
+        import hashlib
+        from unittest.mock import patch
+
+        catalog = self._make_catalog(temp_dir)
+        zip_bytes = self._make_zip_bytes()
+        ext_info = {
+            "id": "test-ext",
+            "name": "Test Extension",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-ext.zip",
+            "sha256": hashlib.sha256(zip_bytes).hexdigest(),
+        }
+
+        with patch.object(catalog, "get_extension_info", return_value=ext_info), \
+             patch.object(catalog, "_open_url", return_value=self._mock_response(zip_bytes)):
+            zip_path = catalog.download_extension("test-ext", target_dir=temp_dir)
+
+        assert zip_path.read_bytes() == zip_bytes
+
+    def test_download_extension_rejects_sha256_mismatch(self, temp_dir):
+        """A catalog ``sha256`` that does not match the downloaded archive
+        aborts the install — a tampered or swapped archive is rejected.
+        """
+        from unittest.mock import patch
+
+        catalog = self._make_catalog(temp_dir)
+        zip_bytes = self._make_zip_bytes()
+        ext_info = {
+            "id": "test-ext",
+            "name": "Test Extension",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-ext.zip",
+            "sha256": "0" * 64,  # deliberately wrong
+        }
+
+        with patch.object(catalog, "get_extension_info", return_value=ext_info), \
+             patch.object(catalog, "_open_url", return_value=self._mock_response(zip_bytes)):
+            with pytest.raises(ExtensionError, match="[Ii]ntegrity"):
+                catalog.download_extension("test-ext", target_dir=temp_dir)
+
+    def test_download_extension_without_sha256_still_succeeds(self, temp_dir):
+        """Entries without ``sha256`` keep working (backwards compatible)."""
+        from unittest.mock import patch
+
+        catalog = self._make_catalog(temp_dir)
+        zip_bytes = self._make_zip_bytes()
+        ext_info = {
+            "id": "test-ext",
+            "name": "Test Extension",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-ext.zip",
+        }
+
+        with patch.object(catalog, "get_extension_info", return_value=ext_info), \
+             patch.object(catalog, "_open_url", return_value=self._mock_response(zip_bytes)):
+            zip_path = catalog.download_extension("test-ext", target_dir=temp_dir)
+
+        assert zip_path.read_bytes() == zip_bytes
+
     def test_download_extension_accepts_direct_github_rest_asset_url(self, temp_dir, monkeypatch):
         """download_extension can use a GitHub REST release asset URL directly."""
         from unittest.mock import patch, MagicMock

tests/test_presets.py

@@ -2019,6 +2019,90 @@ def fake_open(req, timeout=None):
         assert captured[1].get_header("Authorization") == "Bearer ghp_testtoken"
         assert captured[1].get_header("Accept") == "application/octet-stream"
 
+    def _pack_zip_and_response(self):
+        """Build a minimal preset ZIP and a context-manager mock response."""
+        from unittest.mock import MagicMock
+        import io
+
+        zip_buf = io.BytesIO()
+        with zipfile.ZipFile(zip_buf, "w") as zf:
+            zf.writestr("preset.yml", "id: test-pack\nname: Test\nversion: 1.0.0\n")
+        zip_bytes = zip_buf.getvalue()
+
+        resp = MagicMock()
+        resp.read.return_value = zip_bytes
+        # Configure the context-manager protocol explicitly so `with resp`
+        # yields `resp` itself, independent of how the protocol is invoked.
+        resp.__enter__.return_value = resp
+        resp.__exit__.return_value = False
+        return zip_bytes, resp
+
+    def test_download_pack_accepts_matching_sha256(self, project_dir):
+        """A catalog ``sha256`` that matches the preset archive is accepted."""
+        import hashlib
+        from unittest.mock import patch
+
+        catalog = PresetCatalog(project_dir)
+        zip_bytes, resp = self._pack_zip_and_response()
+        pack_info = {
+            "id": "test-pack",
+            "name": "Test Pack",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-pack.zip",
+            "sha256": hashlib.sha256(zip_bytes).hexdigest(),
+            "_install_allowed": True,
+        }
+
+        with patch.object(catalog, "get_pack_info", return_value=pack_info), \
+             patch.object(catalog, "_open_url", return_value=resp):
+            zip_path = catalog.download_pack("test-pack", target_dir=project_dir)
+
+        assert zip_path.read_bytes() == zip_bytes
+
+    def test_download_pack_rejects_sha256_mismatch(self, project_dir):
+        """A catalog ``sha256`` that does not match the archive aborts install."""
+        from unittest.mock import patch
+
+        catalog = PresetCatalog(project_dir)
+        _zip_bytes, resp = self._pack_zip_and_response()
+        pack_info = {
+            "id": "test-pack",
+            "name": "Test Pack",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-pack.zip",
+            "sha256": "0" * 64,  # deliberately wrong
+            "_install_allowed": True,
+        }
+
+        with patch.object(catalog, "get_pack_info", return_value=pack_info), \
+             patch.object(catalog, "_open_url", return_value=resp):
+            with pytest.raises(PresetError, match="[Ii]ntegrity"):
+                catalog.download_pack("test-pack", target_dir=project_dir)
+
+    def test_download_pack_without_sha256_skips_verification(self, project_dir):
+        """A catalog entry with no ``sha256`` keeps working: verification is
+        opt-in, so the backwards-compatible path (``pack_info.get("sha256")``
+        is ``None``) must download without aborting — mirrors the extensions
+        coverage so the helper never silently becomes mandatory for presets.
+        """
+        from unittest.mock import patch
+
+        catalog = PresetCatalog(project_dir)
+        zip_bytes, resp = self._pack_zip_and_response()
+        pack_info = {
+            "id": "test-pack",
+            "name": "Test Pack",
+            "version": "1.0.0",
+            "download_url": "https://example.com/test-pack.zip",
+            "_install_allowed": True,
+        }
+
+        with patch.object(catalog, "get_pack_info", return_value=pack_info), \
+             patch.object(catalog, "_open_url", return_value=resp):
+            zip_path = catalog.download_pack("test-pack", target_dir=project_dir)
+
+        assert zip_path.read_bytes() == zip_bytes
+
     def test_download_pack_accepts_direct_github_rest_asset_url(self, project_dir, monkeypatch):
         """download_pack can use a GitHub REST release asset URL directly."""
         from unittest.mock import patch, MagicMock