Require observed flag checks for auto-validated crackmes

app/controllers/crackme.py

@@ -252,6 +252,7 @@ def _submitted_form_values():
         'labels': normalize_labels(request.form.getlist('labels')),
         'auto_validation': bool(request.form.get('auto_validation')),
         'flag': request.form.get('flag', ''),
+        'observed_flag': request.form.get('observed_flag', ''),
         'points': request.form.get('points', ''),
     }
 
@@ -327,6 +328,11 @@ def upload_crackme_post():
         flag = normalize_flag(request.form.get('flag', ''))
         if not is_valid_flag_format(flag):
             return _upload_rejected(f'Invalid flag format. {FLAG_FORMAT_HINT}')
+        observed_flag = normalize_flag(request.form.get('observed_flag', ''))
+        if not is_valid_flag_format(observed_flag) or observed_flag != flag:
+            return _upload_rejected(
+                'The flag observed from the uploaded file must match the submitted CMO flag.'
+            )
 
         points_value = request.form.get('points') or str(diff_int * 100)
         try:

review/routes.py

@@ -1825,6 +1825,12 @@ def approvecrackme(current_user):
                 'reviewer.viewcrackme', crackme_uuid=crackme_uuid,
                 message=f"Invalid flag format. {FLAG_FORMAT_HINT}"
             ))
+        observed_flag = normalize_flag(request.form.get('observed_flag', ''))
+        if not is_valid_flag_format(observed_flag) or observed_flag != flag:
+            return redirect(url_for(
+                'reviewer.viewcrackme', crackme_uuid=crackme_uuid,
+                message='The flag observed from the uploaded file must match the stored CMO flag.'
+            ))
         updates['flag'] = flag
 
     # Reviewers may adjust the author's proposed reward before approval. The
@@ -2355,6 +2361,11 @@ def _apply_crackme_edit(current_user, crackme_obj, request):
         if flag and not is_valid_flag_format(flag):
             return f"Invalid flag format. {FLAG_FORMAT_HINT}", None
         updates['flag'] = flag or None
+        replacing_file = bool(request.files.get('file') and request.files['file'].filename)
+        if flag and (flag != crackme_obj.get('flag') or replacing_file):
+            observed_flag = normalize_flag(request.form.get('observed_flag', ''))
+            if not is_valid_flag_format(observed_flag) or observed_flag != flag:
+                return "The flag observed from the crackme file must match the stored CMO flag.", None
 
     # Replacement source archive (reviewer-only, never published)
     source_data = None

review/templates/reviewer/editcrackme.html

@@ -109,6 +109,9 @@ <h3>Edit crackme: "{{ crackme.name }}" by {{ crackme.author }}</h3>
                         <label class="form-label" for="flag">Flag</label>
                         <input class="form-input" type="text" id="flag" name="flag" value="{{ crackme.flag }}"
                                placeholder="{{ flag_format_hint }}">
+                        <label class="form-label" for="observed_flag">Flag observed from the crackme file</label>
+                        <input class="form-input" type="text" id="observed_flag" name="observed_flag" autocomplete="off" placeholder="CMO{...}">
+                        <p class="form-input-hint">Required when setting or changing a flag, or replacing a flagged file.</p>
                         <p class="form-input-hint">
                             The flag solvers submit for points. Leave empty (or tick below) and this crackme accepts no
                             flag submissions at all. Setting one on a crackme that had none turns auto-validation on.

review/templates/reviewer/viewcrackme.html

@@ -81,6 +81,10 @@ <h3>Auto-validation</h3>
                         <label class="form-label" for="flag">Flag</label>
                         <input class="form-input" type="text" id="flag" name="flag" value="{{ crackme.flag }}" required>
                     </div>
+                    <div class="form-group">
+                        <label class="form-label" for="observed_flag">Flag independently observed from the downloaded crackme</label>
+                        <input class="form-input" type="text" id="observed_flag" name="observed_flag" required autocomplete="off" placeholder="CMO{...}">
+                    </div>
                     {% else %}
                     <p>The author did not enable auto-validation.</p>
                     {% endif %}

templates/crackme/create.html

@@ -117,6 +117,8 @@ <h3>Quick Rules</h3>
                         Players submit the flag to earn points. Only reviewers can see it.
                     </p>
                     <input class="form-input" type="text" id="flag" name="flag" placeholder="CMO{your_crackmes_flag}" value="{{ form.flag|default('') }}">
+                    <label class="form-label" for="observed_flag" style="margin-top: 8px;">Flag observed from the uploaded file</label>
+                    <input class="form-input" type="text" id="observed_flag" name="observed_flag" placeholder="Run or inspect your file and enter its exact output" value="{{ form.observed_flag|default('') }}">
                     <label class="form-label" for="points" style="margin-top: 8px;">Points</label>
                     <input class="form-input" type="number" id="points" name="points" min="100" max="600" step="1" value="{{ form.points|default('') }}">
                     <p class="form-input-hint">Defaults to difficulty &times; 100. You may choose any whole number from 100 to 600.</p>

templates/rules/crackmerules.html

@@ -71,7 +71,7 @@ <h3>Auto-validation (optional)</h3>
         <p>Auto-validation and providing source code are separate, optional choices. Tick <b>Auto-validation</b> if you want solvers to submit a flag for points. It requires:</p>
         <ul>
             <li><b>The flag</b> your crackme prints when it is solved, in the format <code>CMO{...}</code> &mdash; no
-                spaces or braces inside. Reviewers can read it, because they need it to confirm your crackme is
+                spaces or braces inside. Enter the flag you observed from the uploaded file separately so it can be checked against the submitted flag. Reviewers can read it, because they need it to confirm your crackme is
                 solvable; it is never shown anywhere on the site.</li>
         </ul>
         <p>You may separately upload a private source ZIP for reviewers, with or without auto-validation. For a keygenme,

tests/test_solves.py

@@ -118,6 +118,8 @@ def _upload(client, monkeypatch, tmp_path, **extra):
         'file': (BytesIO(b'challenge-binary'), 'challenge.bin'),
     }
     data.update(extra)
+    if data.get('auto_validation') and 'observed_flag' not in data:
+        data['observed_flag'] = data.get('flag', '')
     return client.post('/upload/crackme', data=data,
                        content_type='multipart/form-data',
                        follow_redirects=True)
@@ -162,6 +164,16 @@ def test_auto_validation_requires_a_well_formed_flag_but_no_source_archive(
     assert stored['source_original_filename'] is None
 
 
+def test_upload_rejects_a_file_flag_that_disagrees_with_the_submitted_flag(
+        alice_client, db, alice, tmp_path, monkeypatch):
+    response = _upload(alice_client, monkeypatch, tmp_path,
+                       auto_validation='on', flag=FLAG,
+                       observed_flag='CTF{wrong_format}')
+
+    assert b'flag observed from the uploaded file must match' in response.data
+    assert db.crackme.count_documents({'name': 'Flagged Challenge'}) == 0
+
+
 def test_source_archive_without_auto_validation(
         alice_client, db, alice, tmp_path, monkeypatch):
     response = _upload(alice_client, monkeypatch, tmp_path,
@@ -519,12 +531,15 @@ def _approval_data(crackme, **overrides):
         'arch': crackme['arch'],
         'platform': crackme['platform'],
         'flag': crackme.get('flag') or '',
+        'observed_flag': crackme.get('flag') or '',
         'official_points': str(round(
             (crackme.get('official_difficulty') or 3) * 100
         )),
         'labels': crackme.get('labels', []),
     }
     data.update(overrides)
+    if 'flag' in overrides and 'observed_flag' not in overrides:
+        data['observed_flag'] = overrides['flag']
     return data
 
 
@@ -574,6 +589,24 @@ def test_approval_records_the_official_difficulty(
     assert stored['flag'] == 'CMO{reviewer_corrected}'
 
 
+def test_approval_rejects_a_mismatched_observed_file_flag(
+        reviewer_client, db, flagged_crackme, monkeypatch, tmp_path):
+    from review import routes
+
+    pending, _, _ = _review_dirs(monkeypatch, tmp_path)
+    db.crackme.update_one({'_id': flagged_crackme['_id']},
+                          {'$set': {'visible': False}})
+    (pending / 'crackme' / flagged_crackme['hexid']).write_bytes(b'binary')
+    response = reviewer_client.post(
+        '/review/approvecrackme',
+        data=_approval_data(flagged_crackme, observed_flag='CTF{different}'),
+        follow_redirects=True,
+    )
+
+    assert b'flag observed from the uploaded file must match' in response.data
+    assert db.crackme.find_one({'_id': flagged_crackme['_id']})['visible'] is False
+
+
 @pytest.mark.parametrize('points', ['99', '601', '250.5', 'many'])
 def test_review_approval_rejects_invalid_points(
         reviewer_client, db, flagged_crackme, monkeypatch, tmp_path, points):
@@ -795,9 +828,12 @@ def _edit(client, crackme, **overrides):
         'arch': crackme.get('arch', ''),
         'platform': crackme.get('platform', ''),
         'flag': crackme.get('flag') or '',
+        'observed_flag': crackme.get('flag') or '',
         'official_points': str(round((crackme.get('official_difficulty') or 0) * 100) or ''),
     }
     data.update(overrides)
+    if 'flag' in overrides and 'observed_flag' not in overrides:
+        data['observed_flag'] = overrides['flag']
     return client.post('/review/editcrackme', data=data,
                        content_type='multipart/form-data')
 
@@ -879,6 +915,15 @@ def test_admin_edit_rejects_a_malformed_flag_or_difficulty(
     assert stored['official_difficulty'] == 3
 
 
+def test_admin_cannot_change_flag_without_matching_file_observation(
+        admin_client, db, flagged_crackme):
+    response = _edit(admin_client, flagged_crackme,
+                     flag='CMO{corrected}', observed_flag='CTF{different}')
+
+    assert b'flag observed from the crackme file must match' in response.data
+    assert db.crackme.find_one({'_id': flagged_crackme['_id']})['flag'] == FLAG
+
+
 def test_admin_replaces_the_private_source_archive(
         admin_client, db, flagged_crackme, monkeypatch, tmp_path):
     from review import routes