Validate resolved snippet source safety

scripts/snippets/model.py

@@ -142,3 +142,15 @@ class SnippetSourceAttributeValidation:
         | None
     )
     issues: tuple[SnippetSourceAttributeIssue, ...]
+
+
+class SnippetSourceSafetyRule(str, Enum):
+    UNREGISTERED_REPOSITORY = "unregistered_repository"
+    UNSAFE_PATH = "unsafe_path"
+
+
+@dataclass(frozen=True)
+class SnippetSourceSafetyIssue:
+    rule: SnippetSourceSafetyRule
+    span: Span
+    message: str

scripts/snippets/validation.py

@@ -13,7 +13,13 @@
     IfVersionAttributeValidation,
     IfVersionCondition,
     IfVersionTag,
+    ImmutableSourceReference,
+    LocalSourceReference,
+    PullRequestSnippetSource,
+    SnippetSourceSafetyIssue,
+    SnippetSourceSafetyRule,
     SnippetTag,
+    Span,
 )
 from .references import parse_github_repository_url
 from .registry import RepositoryRegistry
@@ -255,3 +261,33 @@ def unknown_snippet_attributes(tag: SnippetTag) -> tuple[str, ...]:
             if attribute.name not in SNIPPET_ATTRIBUTES
         )
     )
+
+
+def validate_snippet_source_safety(
+    source: (
+        ImmutableSourceReference | PullRequestSnippetSource | LocalSourceReference
+    ),
+    *,
+    span: Span,
+    registry: RepositoryRegistry,
+) -> tuple[SnippetSourceSafetyIssue, ...]:
+    """Apply repository allowlist and path-safety policy to a resolved source."""
+
+    issues: list[SnippetSourceSafetyIssue] = []
+    if not is_registered_repository(source.repository, registry):
+        issues.append(
+            SnippetSourceSafetyIssue(
+                rule=SnippetSourceSafetyRule.UNREGISTERED_REPOSITORY,
+                span=span,
+                message=f"Repository {source.repository!r} is not allowlisted",
+            )
+        )
+    if not is_safe_source_path(source.path):
+        issues.append(
+            SnippetSourceSafetyIssue(
+                rule=SnippetSourceSafetyRule.UNSAFE_PATH,
+                span=span,
+                message=f"Unsafe source path {source.path!r}",
+            )
+        )
+    return tuple(issues)

tests/test_snippet_source_safety_validation.py

@@ -0,0 +1,66 @@
+from __future__ import annotations
+
+import pytest
+
+from scripts.snippets.model import (
+    ImmutableSourceReference,
+    SnippetSourceSafetyIssue,
+    SnippetSourceSafetyRule,
+    Span,
+)
+from scripts.snippets.registry import (
+    RepositoryConfig,
+    RepositoryRegistry,
+    RepositoryVisibility,
+)
+from scripts.snippets.validation import validate_snippet_source_safety
+
+REGISTRY = RepositoryRegistry(
+    (
+        RepositoryConfig(
+            name="canton-network/splice",
+            url="https://github.com/canton-network/splice",
+            default_branch="main",
+            visibility=RepositoryVisibility.PUBLIC,
+        ),
+    )
+)
+SPAN = Span(start=0, end=1, line=1, column=1)
+COMMIT = "2c941ea9e834d7602d388f3271c0f864025ea756"
+
+
+def validate(
+    repository: str, path: str
+) -> tuple[SnippetSourceSafetyIssue, ...]:
+    return validate_snippet_source_safety(
+        ImmutableSourceReference(
+            repository=repository, commit=COMMIT, path=path
+        ),
+        span=SPAN,
+        registry=REGISTRY,
+    )
+
+
+def test_accepts_allowlisted_repository_and_safe_path() -> None:
+    assert validate("canton-network/splice", "apps/file.yaml") == ()
+
+
+@pytest.mark.parametrize(
+    ("repository", "path", "rule"),
+    [
+        (
+            "unknown/repository",
+            "apps/file.yaml",
+            SnippetSourceSafetyRule.UNREGISTERED_REPOSITORY,
+        ),
+        (
+            "canton-network/splice",
+            "../secret",
+            SnippetSourceSafetyRule.UNSAFE_PATH,
+        ),
+    ],
+)
+def test_rejects_unregistered_repository_or_unsafe_path(
+    repository: str, path: str, rule: SnippetSourceSafetyRule
+) -> None:
+    assert rule in {issue.rule for issue in validate(repository, path)}