fix(metadata): allow readme paths outside the project directory

backend/src/hatchling/builders/sdist.py

@@ -341,8 +341,13 @@ def get_default_build_data(self) -> dict[str, Any]:
 
         readme_path = self.metadata.core.readme_path
         if readme_path:
-            readme_path = normalize_relative_path(readme_path)
-            force_include[os.path.join(self.root, readme_path)] = readme_path
+            normalized_readme = normalize_relative_path(readme_path)
+            # The readme content is always embedded in PKG-INFO, so files
+            # outside the project root are not added to the archive to
+            # avoid path traversal entries in the file list.
+            resolved_readme = os.path.abspath(os.path.join(self.root, normalized_readme))
+            if not os.path.relpath(resolved_readme, os.path.abspath(self.root)).startswith(os.pardir):
+                force_include[resolved_readme] = normalized_readme
 
         license_files = self.metadata.core.license_files
         if license_files:

backend/src/hatchling/metadata/core.py

@@ -529,8 +529,8 @@ def readme(self) -> str:
                     raise TypeError(message)
 
                 readme_path = os.path.normpath(os.path.join(self.root, readme))
-                if os.path.isabs(readme) or os.path.relpath(readme_path, self.root).startswith(".."):
-                    message = f"Readme path must be within the project directory: {readme}"
+                if os.path.isabs(readme):
+                    message = f"Readme path must be relative to the project directory: {readme}"
                     raise ValueError(message)
                 if not os.path.isfile(readme_path):
                     message = f"Readme file does not exist: {readme}"
@@ -569,8 +569,8 @@ def readme(self) -> str:
                         raise TypeError(message)
 
                     path = os.path.normpath(os.path.join(self.root, relative_path))
-                    if os.path.isabs(relative_path) or os.path.relpath(path, self.root).startswith(".."):
-                        message = f"Readme path must be within the project directory: {relative_path}"
+                    if os.path.isabs(relative_path):
+                        message = f"Readme path must be relative to the project directory: {relative_path}"
                         raise ValueError(message)
                     if not os.path.isfile(path):
                         message = f"Readme file does not exist: {relative_path}"

tests/backend/builders/test_sdist.py

@@ -1216,6 +1216,37 @@ def test_readme_always_included(self, hatch, helpers, temp_dir, config_file):
         stat = os.stat(str(extraction_directory / builder.project_id / "PKG-INFO"))
         assert stat.st_mtime == get_reproducible_timestamp()
 
+    def test_readme_outside_project_not_in_archive(self, temp_dir):
+        project_path = temp_dir / "my-app"
+        project_path.mkdir()
+
+        # Shared README in the parent (monorepo) directory
+        readme_path = temp_dir / "README.md"
+        readme_path.write_text("test content\n")
+
+        config = {
+            "project": {"name": "my-app", "version": "0.1.0", "readme": "../README.md"},
+            "tool": {"hatch": {"build": {"targets": {"sdist": {"versions": ["standard"]}}}}},
+        }
+        builder = SdistBuilder(str(project_path), config=config)
+
+        build_path = project_path / "dist"
+        build_path.mkdir()
+
+        with project_path.as_cwd():
+            artifacts = list(builder.build(directory=str(build_path)))
+
+        assert len(artifacts) == 1
+        with tarfile.open(artifacts[0], "r:gz") as tar_archive:
+            # The readme content is embedded in PKG-INFO and the file itself
+            # must not be added with a backward-relative archive path.
+            assert "../README.md" not in tar_archive.getnames()
+            pkg_info = tar_archive.extractfile(
+                next(name for name in tar_archive.getnames() if name.endswith("PKG-INFO"))
+            )
+            assert pkg_info is not None
+            assert "test content" in pkg_info.read().decode()
+
     def test_include_license_files(self, hatch, helpers, temp_dir, config_file):
         config_file.model.template.plugins["default"]["src-layout"] = False
         config_file.save()

tests/backend/metadata/test_core.py

@@ -386,6 +386,29 @@ def test_string_path_nonexistent(self, isolation):
         with pytest.raises(OSError, match="Readme file does not exist: foo/bar\\.md"):
             _ = metadata.core.readme
 
+    def test_string_path_outside_project(self, temp_dir):
+        # Monorepos often share a README from the repository root via a
+        # backward-relative path; the content is embedded in the metadata.
+        readme_path = temp_dir.parent / "README.md"
+        readme_path.write_text("test content")
+
+        metadata = ProjectMetadata(str(temp_dir), None, {"project": {"readme": "../README.md"}})
+
+        assert metadata.core.readme == metadata.core.readme == "test content"
+        assert metadata.core.readme_content_type == metadata.core.readme_content_type == "text/markdown"
+        assert metadata.core.readme_path == metadata.core.readme_path == "../README.md"
+
+    def test_table_file_path_outside_project(self, temp_dir):
+        readme_path = temp_dir.parent / "README.md"
+        readme_path.write_text("test content")
+
+        metadata = ProjectMetadata(
+            str(temp_dir), None, {"project": {"readme": {"file": "../README.md", "content-type": "text/markdown"}}}
+        )
+
+        assert metadata.core.readme == metadata.core.readme == "test content"
+        assert metadata.core.readme_path == metadata.core.readme_path == "../README.md"
+
     @pytest.mark.parametrize(
         ("extension", "content_type"), [(".md", "text/markdown"), (".rst", "text/x-rst"), (".txt", "text/plain")]
     )