Pin public Brotli headers for the final-image linkage probe

.github/workflows/publish-current-server.yml

@@ -221,7 +221,31 @@ jobs:
         run: |
           set -Eeuo pipefail
           evidence="$RUNNER_TEMP/server-evidence"
+          # Compile against pinned public declarations, without installing a
+          # decoder or relying on runner-provided development packages.
+          python3 - "$evidence/brotli-headers" <<'PY'
+          import hashlib, io, json, pathlib, re, sys, tarfile, urllib.request
+          lock = json.loads(pathlib.Path('source/server/security/ubuntu-backports/brotli/brotli.lock.json').read_text())
+          item, = (x for x in lock['sourceFiles'] if x['name'] == 'brotli_1.2.0.orig.tar.gz')
+          with urllib.request.urlopen(item['url'], timeout=60) as response:
+              data = response.read(item['size'] + 1)
+          assert len(data) == item['size'] and hashlib.sha256(data).hexdigest() == item['sha256']
+          output = pathlib.Path(sys.argv[1]) / 'brotli'
+          output.mkdir(parents=True)
+          with tarfile.open(fileobj=io.BytesIO(data)) as archive:
+              names = set()
+              for member in archive.getmembers():
+                  match = re.fullmatch(r'google-brotli-028fb5a/c/include/brotli/([a-z_]+\.h)', member.name)
+                  if not match:
+                      continue
+                  assert member.isfile() and match[1] not in names
+                  names.add(match[1])
+                  (output / match[1]).write_bytes(archive.extractfile(member).read())
+          assert {'decode.h', 'encode.h', 'types.h', 'port.h'} <= names
+          assert hashlib.sha256((output / 'decode.h').read_bytes()).hexdigest() == lock['baselineSha256']['c/include/brotli/decode.h']
+          PY
           cc -O2 -Wall -Wextra -Werror \
+            -I"$evidence/brotli-headers" \
             source/server/security/ubuntu-backports/bundle/installer/testdata/consumer-brotli-probe.c \
             -ldl -o "$evidence/brotli-runtime-probe"
           docker run --rm --network none \

scripts/test-server-backport-consumer-contract.py

@@ -65,6 +65,8 @@ def verify(files):
                 and 'test -z "$brotli_integrity"' in source for source in (runtime, build)),
             'Brotli dpkg verification failure must propagate before its empty-output check')
     for marker in ['consumer-brotli-probe.c', '--entrypoint /tmp/brotli-runtime-probe "$CANDIDATE_IMAGE"',
+                   'brotli/brotli.lock.json', '-I"$evidence/brotli-headers"',
+                   "hashlib.sha256(data).hexdigest() == item['sha256']",
                    'PASS: three installed Brotli SONAMEs RTLD_NOW, ordinary compression/decompression']:
         require(marker in publisher, 'Missing actual final-image ordinary Brotli probe: ' + marker)
     require('              brotli-runtime.txt' in publisher and '"$evidence/brotli-runtime.txt"' in publisher,
@@ -135,6 +137,7 @@ def test_missing_brotli_runtime_or_published_proof_is_rejected(self):
                              (BUILD, 'brotli_linkage="$(ldd -r '),
                              (DOCKER, 'test -z "$brotli_integrity"'),
                              (BUILD, 'test -z "$brotli_integrity"'),
+                             (PUBLISH, '-I"$evidence/brotli-headers"'),
                              (PUBLISH, '--entrypoint /tmp/brotli-runtime-probe "$CANDIDATE_IMAGE"'),
                              (PUBLISH, '              brotli-runtime.txt')]:
             with self.subTest(name=name), self.assertRaises(AssertionError):