Use a whitelist for allowed values in the unique field.

hc/api/schemas.py

@@ -1,9 +1,14 @@
 check = {
+    "type": "object",
     "properties": {
         "name": {"type": "string"},
         "tags": {"type": "string"},
         "timeout": {"type": "number", "minimum": 60, "maximum": 604800},
         "grace": {"type": "number", "minimum": 60, "maximum": 604800},
-        "channels": {"type": "string"}
+        "channels": {"type": "string"},
+        "unique": {
+            "type": "array",
+            "items": {"enum": ["name", "tags", "timeout", "grace"]}
+        }
     }
 }

hc/api/tests/test_create_check.py

@@ -7,10 +7,7 @@ from hc.test import BaseTestCase
 class CreateCheckTestCase(BaseTestCase):
     URL = "/api/v1/checks/"
 
-    def setUp(self):
+    def post(self, data, expected_error=None, expected_fragment=None):
-        super(CreateCheckTestCase, self).setUp()
-
-    def post(self, data, expected_error=None):
         r = self.client.post(self.URL, json.dumps(data),
                              content_type="application/json")
 
@@ -18,6 +15,10 @@ class CreateCheckTestCase(BaseTestCase):
             self.assertEqual(r.status_code, 400)
             self.assertEqual(r.json()["error"], expected_error)
 
+        if expected_fragment:
+            self.assertEqual(r.status_code, 400)
+            self.assertIn(expected_fragment, r.json()["error"])
+
         return r
 
     def test_it_works(self):
@@ -63,6 +64,22 @@ class CreateCheckTestCase(BaseTestCase):
         check = Check.objects.get()
         self.assertEqual(check.channel_set.get(), channel)
 
+    def test_it_supports_unique(self):
+        existing = Check(user=self.alice, name="Foo")
+        existing.save()
+
+        r = self.post({
+            "api_key": "abc",
+            "name": "Foo",
+            "unique": ["name"]
+        })
+
+        # Expect 200 instead of 201
+        self.assertEqual(r.status_code, 200)
+
+        # And there should be only one check in the database:
+        self.assertEqual(Check.objects.count(), 1)
+
     def test_it_handles_missing_request_body(self):
         r = self.client.post(self.URL, content_type="application/json")
         self.assertEqual(r.status_code, 400)
@@ -80,16 +97,33 @@ class CreateCheckTestCase(BaseTestCase):
 
     def test_it_rejects_small_timeout(self):
         self.post({"api_key": "abc", "timeout": 0},
-                  expected_error="timeout is too small")
+                  expected_fragment="timeout is too small")
 
     def test_it_rejects_large_timeout(self):
         self.post({"api_key": "abc", "timeout": 604801},
-                  expected_error="timeout is too large")
+                  expected_fragment="timeout is too large")
 
     def test_it_rejects_non_number_timeout(self):
         self.post({"api_key": "abc", "timeout": "oops"},
-                  expected_error="timeout is not a number")
+                  expected_fragment="timeout is not a number")
 
     def test_it_rejects_non_string_name(self):
         self.post({"api_key": "abc", "name": False},
-                  expected_error="name is not a string")
+                  expected_fragment="name is not a string")
+
+    def test_unique_accepts_only_whitelisted_values(self):
+        existing = Check(user=self.alice, name="Foo")
+        existing.save()
+
+        self.post({
+            "api_key": "abc",
+            "name": "Foo",
+            "unique": ["status"]
+        }, expected_fragment="unexpected value")
+
+    def test_it_rejects_bad_unique_values(self):
+        self.post({
+            "api_key": "abc",
+            "name": "Foo",
+            "unique": "not a list"
+        }, expected_fragment="not an array")

hc/api/views.py

@@ -9,7 +9,7 @@ from django.views.decorators.csrf import csrf_exempt
 
 from hc.api import schemas
 from hc.api.decorators import check_api_key, uuid_or_400, validate_json
-from hc.api.models import Check, Ping
+from hc.api.models import Check, Ping, DEFAULT_TIMEOUT, DEFAULT_GRACE
 from hc.lib.badges import check_signature, get_badge_svg
 
 
@@ -56,37 +56,36 @@ def checks(request):
         return JsonResponse(doc)
 
     elif request.method == "POST":
+        name = str(request.json.get("name", ""))
+        tags = str(request.json.get("tags", ""))
+
+        timeout = DEFAULT_TIMEOUT
+        if "timeout" in request.json:
+            timeout = td(seconds=request.json["timeout"])
+
+        grace = DEFAULT_GRACE
+        if "grace" in request.json:
+            grace = td(seconds=request.json["grace"])
 
         unique_fields = request.json.get("unique", [])
-        name = str(request.json.get("name", ""))
+        if unique_fields:
-
-        if len(unique_fields) > 0:
             existing_checks = Check.objects.filter(user=request.user)
-
+            if "name" in unique_fields:
-            for unique_field in unique_fields:
+                existing_checks = existing_checks.filter(name=name)
-
+            if "tags" in unique_fields:
-                field_value = request.json.get(unique_field)
+                existing_checks = existing_checks.filter(tags=tags)
-
+            if "timeout" in unique_fields:
-                if unique_field == "timeout" or unique_field == "grace":
+                existing_checks = existing_checks.filter(timeout=timeout)
-                    field_value = td(seconds=field_value)
+            if "grace" in unique_fields:
-
+                existing_checks = existing_checks.filter(grace=grace)
-                try:
-                    existing_checks = existing_checks.filter(**{unique_field: field_value})
-                except FieldError:
-                    return HttpResponse(status=400)
 
             if existing_checks.count() > 0:
-                # There might be more than one check with the same name since name
+                # There might be more than one matching check, return first
-                # uniqueness isn't enforced in the model
+                first_match = existing_checks.first()
-                return JsonResponse(existing_checks.first().to_dict(), status=200)
+                return JsonResponse(first_match.to_dict(), status=200)
 
-        check = Check(user=request.user)
+        check = Check(user=request.user, name=name, tags=tags,
-        check.name = name
+                      timeout=timeout, grace=grace)
-        check.tags = str(request.json.get("tags", ""))
-        if "timeout" in request.json:
-            check.timeout = td(seconds=request.json["timeout"])
-        if "grace" in request.json:
-            check.grace = td(seconds=request.json["grace"])
 
         check.save()