utils/generate-cyclonedx: generate externalReferences with source-distribution

BSI TR-03183-2 5.4.2 [1] lists source code URIs under "Additional data fields
for each component", and as such "MUST additionally be provided, if it exists".

If a http or https source download URI is available from show-info, extract
it and include it as an externalReference of type "source-distribution" in the
CycloneDX output.

[1] https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/Publications/TechGuidelines/TR03183/BSI-TR-03183-2_v2_1_0.pdf?__blob=publicationFile&v=5

Signed-off-by: Martin Willi <martin@strongswan.org>
Acked-by: Thomas Perale <thomas.perale@mind.be>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>

support/testing/tests/utils/test_generate_cyclonedx.py

@@ -140,3 +140,29 @@ class TestGenerateCycloneDX(unittest.TestCase):
 
         foo_deps = next(d for d in result["dependencies"] if d["ref"] == "package-foo")
         self.assertEqual(foo_deps["dependsOn"], ["package-bar", "skeleton-baz"])
+
+    def test_external_references(self):
+        info = self._make_show_info()
+        info["package-foo"]["downloads"] = [
+            {
+                "source": "foo-1.2.tar.gz",
+                "uris": [
+                    "https+https://sources.buildroot.net/foo",
+                    "http|https+https://mirror.example.org/foo",
+                ],
+            },
+        ]
+
+        result = self._run_script(show_info=info)
+        foo = self._find_component(result, "package-foo")
+
+        self.assertIn("externalReferences", foo)
+        self.assertEqual(
+            foo["externalReferences"],
+            [
+                {
+                    "type": "source-distribution",
+                    "url": "https://mirror.example.org/foo/foo-1.2.tar.gz",
+                },
+            ],
+        )

utils/generate-cyclonedx

@@ -14,6 +14,8 @@ import gzip
 import json
 import os
 from pathlib import Path
+from typing import Iterator
+import urllib.parse
 import urllib.request
 import subprocess
 import sys
@@ -261,6 +263,50 @@ def cyclonedx_patches(patch_list: list[str]):
     }
 
 
+def parse_uris(uris: list[str]) -> Iterator[tuple[list[str], str]]:
+    """Parse download URIs into (schemes, url) tuples.
+
+    Splits the Buildroot URI format "scheme[|scheme]+url" and yields all
+    Buildroot schemes with the stripped URL, excluding
+    sources.buildroot.net mirrors.
+
+    Args:
+        uris (list): Array of URI strings from the show-info output.
+    Yields:
+        tuple[list[str], str]: (schemes, url) for each usable URI.
+    """
+    for uri in uris:
+        scheme, _, stripped_uri = uri.partition("+")
+        if stripped_uri:
+            parsed = urllib.parse.urlparse(stripped_uri)
+            if parsed.hostname != "sources.buildroot.net":
+                yield scheme.split("|"), stripped_uri
+
+
+def cyclonedx_external_refs(comp):
+    """Create CycloneDX external references for a component.
+
+    Args:
+        comp (dict): The component information from the show-info output.
+    Returns:
+        dict: External reference information in CycloneDX format, or empty dict
+    """
+    SOURCE_DIST_SCHEMES = {"http", "https"}
+
+    refs = []
+    for download in comp.get("downloads", []):
+        source = download.get("source")
+        for schemes, uri in parse_uris(download.get("uris", [])):
+            if set(schemes) & SOURCE_DIST_SCHEMES and source:
+                refs.append({
+                    "type": "source-distribution",
+                    "url": f"{uri}/{source}",
+                })
+    if refs:
+        return {"externalReferences": refs}
+    return {}
+
+
 def cyclonedx_component(name, comp):
     """Translate a component from the show-info output, to a component entry in CycloneDX format.
 
@@ -284,6 +330,7 @@ def cyclonedx_component(name, comp):
         **({
             "cpe": comp["cpe-id"],
         } if "cpe-id" in comp else {}),
+        **cyclonedx_external_refs(comp),
         **(cyclonedx_patches(comp["patches"]) if comp.get("patches") else {}),
         "properties": [{
             "name": "BR_TYPE",