Initial commit: hardened DeerFlow factory

Vendored deer-flow upstream (bytedance/deer-flow) plus prompt-injection
hardening:

- New deerflow.security package: content_delimiter, html_cleaner,
  sanitizer (8 layers — invisible chars, control chars, symbols, NFC,
  PUA, tag chars, horizontal whitespace collapse with newline/tab
  preservation, length cap)
- New deerflow.community.searx package: web_search, web_fetch,
  image_search backed by a private SearX instance, every external
  string sanitized and wrapped in <<<EXTERNAL_UNTRUSTED_CONTENT>>>
  delimiters
- All native community web providers (ddg_search, tavily, exa,
  firecrawl, jina_ai, infoquest, image_search) replaced with hard-fail
  stubs that raise NativeWebToolDisabledError at import time, so a
  misconfigured tool.use path fails loud rather than silently falling
  back to unsanitized output
- Native client back-doors (jina_client.py, infoquest_client.py)
  stubbed too
- Native-tool tests quarantined under tests/_disabled_native/
  (collect_ignore_glob via local conftest.py)
- Sanitizer Layer 7 fix: only collapse horizontal whitespace, preserve
  newlines and tabs so list/table structure survives
- Hardened runtime config.yaml references only the searx-backed tools
- Factory overlay (backend/) kept in sync with deer-flow tree as a
  reference / source

See HARDENING.md for the full audit trail and verification steps.

deer-flow/backend/tests/test_skills_validation.py

@@ -0,0 +1,180 @@
+"""Tests for skill frontmatter validation.
+
+Consolidates all _validate_skill_frontmatter tests (previously split across
+test_skills_router.py and this module) into a single dedicated module.
+"""
+
+from pathlib import Path
+
+from deerflow.skills.validation import ALLOWED_FRONTMATTER_PROPERTIES, _validate_skill_frontmatter
+
+
+def _write_skill(tmp_path: Path, content: str) -> Path:
+    """Write a SKILL.md file and return its parent directory."""
+    skill_file = tmp_path / "SKILL.md"
+    skill_file.write_text(content, encoding="utf-8")
+    return tmp_path
+
+
+class TestValidateSkillFrontmatter:
+    def test_valid_minimal_skill(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill\ndescription: A valid skill\n---\n\nBody\n",
+        )
+        valid, msg, name = _validate_skill_frontmatter(skill_dir)
+        assert valid is True
+        assert msg == "Skill is valid!"
+        assert name == "my-skill"
+
+    def test_valid_with_all_allowed_fields(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill\ndescription: A skill\nlicense: MIT\nversion: '1.0'\nauthor: test\n---\n\nBody\n",
+        )
+        valid, msg, name = _validate_skill_frontmatter(skill_dir)
+        assert valid is True
+        assert msg == "Skill is valid!"
+        assert name == "my-skill"
+
+    def test_missing_skill_md(self, tmp_path):
+        valid, msg, name = _validate_skill_frontmatter(tmp_path)
+        assert valid is False
+        assert "not found" in msg
+        assert name is None
+
+    def test_no_frontmatter(self, tmp_path):
+        skill_dir = _write_skill(tmp_path, "# Just markdown\n\nNo front matter.\n")
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "frontmatter" in msg.lower()
+
+    def test_invalid_yaml(self, tmp_path):
+        skill_dir = _write_skill(tmp_path, "---\n[invalid yaml: {{\n---\n\nBody\n")
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "YAML" in msg
+
+    def test_missing_name(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\ndescription: A skill without a name\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "name" in msg.lower()
+
+    def test_missing_description(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "description" in msg.lower()
+
+    def test_unexpected_keys_rejected(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill\ndescription: test\ncustom-field: bad\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "custom-field" in msg
+
+    def test_name_must_be_hyphen_case(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: MySkill\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "hyphen-case" in msg
+
+    def test_name_no_leading_hyphen(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: -my-skill\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "hyphen" in msg
+
+    def test_name_no_trailing_hyphen(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill-\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "hyphen" in msg
+
+    def test_name_no_consecutive_hyphens(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my--skill\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "hyphen" in msg
+
+    def test_name_too_long(self, tmp_path):
+        long_name = "a" * 65
+        skill_dir = _write_skill(
+            tmp_path,
+            f"---\nname: {long_name}\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "too long" in msg.lower()
+
+    def test_description_no_angle_brackets(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: my-skill\ndescription: Has <html> tags\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "angle brackets" in msg.lower()
+
+    def test_description_too_long(self, tmp_path):
+        long_desc = "a" * 1025
+        skill_dir = _write_skill(
+            tmp_path,
+            f"---\nname: my-skill\ndescription: {long_desc}\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "too long" in msg.lower()
+
+    def test_empty_name_rejected(self, tmp_path):
+        skill_dir = _write_skill(
+            tmp_path,
+            "---\nname: ''\ndescription: test\n---\n\nBody\n",
+        )
+        valid, msg, _ = _validate_skill_frontmatter(skill_dir)
+        assert valid is False
+        assert "empty" in msg.lower()
+
+    def test_allowed_properties_constant(self):
+        assert "name" in ALLOWED_FRONTMATTER_PROPERTIES
+        assert "description" in ALLOWED_FRONTMATTER_PROPERTIES
+        assert "license" in ALLOWED_FRONTMATTER_PROPERTIES
+
+    def test_reads_utf8_on_windows_locale(self, tmp_path, monkeypatch):
+        skill_dir = _write_skill(
+            tmp_path,
+            '---\nname: demo-skill\ndescription: "Curly quotes: \u201cutf8\u201d"\n---\n\n# Demo Skill\n',
+        )
+        original_read_text = Path.read_text
+
+        def read_text_with_gbk_default(self, *args, **kwargs):
+            kwargs.setdefault("encoding", "gbk")
+            return original_read_text(self, *args, **kwargs)
+
+        monkeypatch.setattr(Path, "read_text", read_text_with_gbk_default)
+
+        valid, msg, name = _validate_skill_frontmatter(skill_dir)
+        assert valid is True
+        assert msg == "Skill is valid!"
+        assert name == "demo-skill"