wsgi: Catch JSON payload decoding errors.

caucase/exceptions.py

@@ -42,3 +42,7 @@ class CertificateVerificationError(CertificateAuthorityException):
 class NotACertificateSigningRequest(CertificateAuthorityException):
   """Provided value is not a certificate signing request"""
   pass
+
+class NotJSON(CertificateAuthorityException):
+  """Provided value does not decode properly as JSON"""
+  pass

caucase/test.py

@@ -1175,6 +1175,7 @@ class CaucaseTest(unittest.TestCase):
       """
       Mock CAU.
       """
+      digest_list = ['sha256']
       def getCACertificateList(self):
         """
         Return cau ca list.
@@ -1319,6 +1320,12 @@ class CaucaseTest(unittest.TestCase):
       'CONTENT_TYPE': 'application/json',
       'wsgi.input': StringIO('{"digest": null}'),
     })[0], UNAUTHORISED_STATUS)
+    self.assertEqual(request({
+      'PATH_INFO': '/cau/crt/revoke',
+      'REQUEST_METHOD': 'PUT',
+      'CONTENT_TYPE': 'application/json',
+      'wsgi.input': StringIO('{"digest":"sha256","payload":""}'),
+    })[0], 400)
     self.assertEqual(request({
       'PATH_INFO': '/cau/crt/revoke',
       'REQUEST_METHOD': 'PUT',

caucase/utils.py

@@ -33,7 +33,10 @@ from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.hazmat.primitives.asymmetric import padding
 import cryptography.exceptions
 import pem
-from .exceptions import CertificateVerificationError
+from .exceptions import (
+  CertificateVerificationError,
+  NotJSON,
+)
 
 DEFAULT_DIGEST_LIST = ('sha256', 'sha384', 'sha512')
 DEFAULT_DIGEST = DEFAULT_DIGEST_LIST[0]
@@ -262,7 +265,10 @@ def unwrap(wrapped, getCertificate, digest_list):
       '%r is not in allowed digest list',
     )
   hash_class = getattr(hashes, digest.upper())
+  try:
     payload = json.loads(wrapped['payload'])
+  except ValueError:
+    raise NotJSON
   x509.load_pem_x509_certificate(
     getCertificate(payload).encode('ascii'),
     _cryptography_backend,
@@ -283,7 +289,10 @@ def nullUnwrap(wrapped):
   an authenticated user (and hence over a secure channel, HTTPS).
   """
   assert wrapped['digest'] is None
+  try:
     return json.loads(wrapped['payload'])
+  except ValueError:
+    raise NotJSON
 
 def load_ca_certificate(data):
   """

caucase/wsgi.py

@@ -169,6 +169,8 @@ class Application(object):
         raise Conflict
       except exceptions.NoStorage:
         raise InsufficientStorage
+      except exceptions.NotJSON:
+        raise BadRequest('Invalid json payload')
       except exceptions.CertificateAuthorityException, e:
         raise BadRequest(str(e))
       except Exception: