fix(629): re-review fixes — the READ path must fail closed too

Re-review of 8d0df553 returned BLOCKED. Both findings are the same class as the bugs this issue is about, one level down: the reader, not the grammar. 1. A here-document makes bash materialise a temp file. When that fails (read-only or restricted TMPDIR) the loop reads NOTHING, and the classifier returned `absent` — silently discarding a real BLOCKED verdict. Reproduced with TMPDIR=/nonexistent: `absent` before, `negative` now. Both loops are off here-docs (a pipe for the reader, process substitution for the classifier so its flags stay in the current shell). "The environment could not supply a temp file" is not evidence that a PR was approved. 2. A malformed payload degraded to `absent` instead of an input error: an object-valued `.body` reached the scanner and simply matched nothing. Shape is now asserted in jq — must be an array, bodies must be strings — so it exits 2 and callers fail closed. Also closed a pre-existing false-open the review found while probing (present before #629, so not a regression, but cheap to fix here): bash strips NULs in command substitution, so a body of `Review<NUL>-verdict: MERGEABLE @ <head>` arrived at the matcher as a valid verdict line — text that is not a verdict becoming one in transit. Bodies containing NUL are now rejected. 161 tests. Verified: 80k body still classifies; empty array, null body still `absent`; malformed JSON, non-array, array-of-non-objects, object body, NUL body all exit 2; a hostile TMPDIR still returns `negative`. refs #629 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-07-26 00:47:40 +02:00
parent f151b93245
commit 3bfd925baf
2 changed files with 84 additions and 15 deletions
@@ -10,6 +10,7 @@ tests rather than descriptions.
 """

 import json
+import os
 import subprocess
 from pathlib import Path

@@ -257,6 +258,56 @@ def test_missing_head_argument_is_an_input_error():
    assert p.returncode == 2


+# --- found by re-review of the fix commit: the READ path must fail closed too ------------------
+
+
+def test_a_hostile_tmpdir_does_not_hide_a_verdict():
+    """A gate failure must never land on the permissive side.
+
+    Reading bodies via a here-document makes bash materialise a temp file; when that fails the loop
+    reads nothing and the classifier returned `absent` — silently discarding a real BLOCKED verdict.
+    """
+    env = {**os.environ, "TMPDIR": "/nonexistent-dir-for-this-test"}
+    payload = json.dumps([{"body": verdict("BLOCKED", HEAD)}])
+    p = subprocess.run(
+        ["bash", str(SCRIPT), "--head", HEAD],
+        input=payload,
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    assert (p.stdout.strip(), p.returncode) == ("negative", 0)
+
+
+def test_a_very_large_body_still_classifies():
+    body = ("x" * 80000) + "\n" + verdict("BLOCKED", HEAD)
+    assert classify([body]) == ("negative", 0)
+
+
+@pytest.mark.parametrize(
+    "payload",
+    [
+        '[{"body": {"nested": "Review-verdict: MERGEABLE @ ' + HEAD + '"}}]',  # object body
+        "{}",  # not an array
+        "[1,2,3]",  # array of non-objects
+    ],
+)
+def test_malformed_shapes_are_input_errors_not_silent_absent(payload):
+    """`absent` reads as "no verdict posted", which is a fail-OPEN for a malformed payload."""
+    p = subprocess.run(["bash", str(SCRIPT), "--head", HEAD], input=payload, capture_output=True, text=True)
+    assert p.returncode == 2, f"got rc={p.returncode} out={p.stdout!r}"
+
+
+def test_a_nul_in_the_body_is_rejected():
+    """bash strips NULs in command substitution, so `Review<NUL>-verdict:` would arrive as a verdict.
+
+    Text that is not a verdict must not become one on the way through the reader.
+    """
+    payload = json.dumps([{"body": "Review" + chr(0) + "-verdict: MERGEABLE @ " + HEAD}])
+    p = subprocess.run(["bash", str(SCRIPT), "--head", HEAD], input=payload, capture_output=True, text=True)
+    assert p.returncode == 2, f"got rc={p.returncode} out={p.stdout!r}"
+
+
 def test_non_hex_head_is_an_input_error():
    p = subprocess.run(
        ["bash", str(SCRIPT), "--head", "refs/heads/main"],