Use HMAC.hexdigest to avoid non-ascii characters for package data

hmac.compare_digest() method in python 3 doesn't suppport non-ASCII
characters, so that we need to use HMAC.hexdigest() to avoid non-ASCII
bytes.

For backward compability, we still need to support HMAC created by
using HMAC.digest() in the old amphorae.

Change-Id: I1061e855d0ce06d91a26d217291008197e4a708b
Depends-On: https://review.openstack.org/#/c/567688/
Story: 2002125
Task: 19807

octavia/amphorae/backends/health_daemon/status_message.py

@@ -27,6 +27,7 @@ LOG = logging.getLogger(__name__)
 
 hash_algo = hashlib.sha256
 hash_len = 32
+hex_hash_len = 64
 
 
 def to_hex(byte_array):
@@ -45,21 +46,40 @@ def decode_obj(binary_array):
     return obj
 
 
-def wrap_envelope(obj, key):
+def wrap_envelope(obj, key, hex=True):
     payload = encode_obj(obj)
-    hmc = get_hmac(payload, key)
+    hmc = get_hmac(payload, key, hex=hex)
     envelope = payload + hmc
     return envelope
 
 
 def unwrap_envelope(envelope, key):
-    payload = envelope[:-hash_len]
-    expected_hmc = envelope[-hash_len:]
-    calculated_hmc = get_hmac(payload, key)
+    """A backward-compatible way to get data.
+
+    We may still receive package from amphorae that are using digest() instead
+    of hexdigest()
+    """
+    try:
+        return get_payload(envelope, key, hex=True)
+    except Exception:
+        return get_payload(envelope, key, hex=False)
+
+
+def get_payload(envelope, key, hex=True):
+    len = hex_hash_len if hex else hash_len
+    payload = envelope[:-len]
+    expected_hmc = envelope[-len:]
+    calculated_hmc = get_hmac(payload, key, hex=hex)
     if not secretutils.constant_time_compare(expected_hmc, calculated_hmc):
-        LOG.warning('calculated hmac: %(s1)s not equal to msg hmac: '
-                    '%(s2)s dropping packet', {'s1': to_hex(calculated_hmc),
-                                               's2': to_hex(expected_hmc)})
+        LOG.warning(
+            'calculated hmac(hex=%(hex)s): %(s1)s not equal to msg hmac: '
+            '%(s2)s dropping packet',
+            {
+                'hex': hex,
+                's1': to_hex(calculated_hmc),
+                's2': to_hex(expected_hmc)
+            }
+        )
         fmt = 'calculated hmac: {0} not equal to msg hmac: {1} dropping packet'
         raise exceptions.InvalidHMACException(fmt.format(
             to_hex(calculated_hmc), to_hex(expected_hmc)))
@@ -67,6 +87,11 @@ def unwrap_envelope(envelope, key):
     return obj
 
 
-def get_hmac(payload, key):
+def get_hmac(payload, key, hex=True):
+    """Get digest for the payload.
+
+    The hex param is for backward compatibility, so the package data sent from
+    the existing amphorae can still be checked in the previous approach.
+    """
     hmc = hmac.new(key.encode("utf-8"), payload, hashlib.sha256)
-    return hmc.digest()
+    return hmc.hexdigest().encode("utf-8") if hex else hmc.digest()

octavia/tests/unit/amphorae/backends/health_daemon/test_envelope.py

@@ -37,3 +37,20 @@ class TestEnvelope(base.TestCase):
             args = (envelope, 'samplekey?')
             self.assertRaises(exceptions.InvalidHMACException,
                               status_message.unwrap_envelope, *args)
+
+    def test_message_hmac_compatibility(self):
+        seq = 42
+        statusMsg = {'seq': seq,
+                     'status': 'OK',
+                     'id': str(uuid.uuid4())}
+
+        envelope = status_message.wrap_envelope(statusMsg, 'samplekey1',
+                                                hex=False)
+        obj = status_message.unwrap_envelope(envelope, 'samplekey1')
+
+        self.assertEqual('OK', obj['status'])
+        self.assertEqual(seq, obj['seq'])
+
+        args = (envelope, 'samplekey?')
+        self.assertRaises(exceptions.InvalidHMACException,
+                          status_message.unwrap_envelope, *args)

octavia/tests/unit/amphorae/backends/health_daemon/test_health_sender.py

@@ -28,9 +28,11 @@ IP_PORT = ['192.0.2.10:5555', '192.0.2.10:5555']
 KEY = 'TEST'
 PORT = random.randrange(1, 9000)
 SAMPLE_MSG = {'testkey': 'TEST'}
-SAMPLE_MSG_BIN = binascii.unhexlify('78daab562a492d2ec94ead54b252500a710d0e5'
-                                    '1aa050041b506245806e5c1971e79951818394e'
-                                    'a6e71ad989ff950945f9573f4ab6f83e25db8ed7')
+SAMPLE_MSG_BIN = binascii.unhexlify('78daab562a492d2ec94ead54b252500a710d0e51a'
+                                    'a050041b506243538303665356331393731653739'
+                                    '39353138313833393465613665373161643938396'
+                                    '66639353039343566393537336634616236663833'
+                                    '653235646238656437')
 
 
 class TestHealthSender(base.TestCase):