Verify MD5 is available

botocore/compat.py

@@ -16,10 +16,15 @@
 import sys
 import inspect
 import warnings
+import hashlib
+import logging
 
 from botocore.vendored import six
+from botocore.exceptions import MD5UnavailableError
 from botocore.vendored.requests.packages.urllib3 import exceptions
 
+logger = logging.getLogger(__name__)
+
 
 if six.PY3:
  from six.moves import http_client
@@ -237,3 +242,30 @@ def total_seconds(delta):
  day_in_seconds = delta.days * 24 * 3600.0
  micro_in_seconds = delta.microseconds / 10.0**6
  return day_in_seconds + delta.seconds + micro_in_seconds
+
+
+# Checks to see if md5 is available on this system. A given system might not
+# have access to it for various reasons, such as FIPS mode being enabled.
+try:
+ hashlib.md5()
+ MD5_AVAILABLE = True
+except ValueError:
+ MD5_AVAILABLE = False
+
+
+def get_md5(*args, **kwargs):
+ """
+ Attempts to get an md5 hashing object.
+
+ :param raise_error_if_unavailable: raise an error if md5 is unavailable on
+ this system. If False, None will be returned if it is unavailable.
+ :type raise_error_if_unavailable: bool
+ :param args: Args to pass to the MD5 constructor
+ :param kwargs: Key word arguments to pass to the MD5 constructor
+ :return: An MD5 hashing object if available. If it is unavailable, None
+ is returned if raise_error_if_unavailable is set to False.
+ """
+ if MD5_AVAILABLE:
+ return hashlib.md5(*args, **kwargs)
+ else:
+ raise MD5UnavailableError()

botocore/exceptions.py

@@ -367,3 +367,7 @@ class InvalidConfigError(BotoCoreError):
 
 class RefreshWithMFAUnsupportedError(BotoCoreError):
  fmt = 'Cannot refresh credentials: MFA token required.'
+
+
+class MD5UnavailableError(BotoCoreError):
+ fmt = "This system does not support MD5 generation."

botocore/handlers.py

@@ -17,15 +17,14 @@
 """
 
 import base64
-import hashlib
 import logging
 import xml.etree.cElementTree
 import copy
 import re
 import warnings
 
 from botocore.compat import urlsplit, urlunsplit, unquote, \
- json, quote, six, unquote_str, ensure_bytes
+ json, quote, six, unquote_str, ensure_bytes, get_md5, MD5_AVAILABLE
 from botocore.docs.utils import AutoPopulatedParam
 from botocore.docs.utils import HideParamFromOperations
 from botocore.docs.utils import AppendParamDocumentation
@@ -134,13 +133,13 @@ def calculate_md5(params, **kwargs):
 
 
 def _calculate_md5_from_bytes(body_bytes):
- md5 = hashlib.md5(body_bytes)
+ md5 = get_md5(body_bytes)
  return md5.digest()
 
 
 def _calculate_md5_from_file(fileobj):
  start_position = fileobj.tell()
- md5 = hashlib.md5()
+ md5 = get_md5()
  for chunk in iter(lambda: fileobj.read(1024 * 1024), b''):
  md5.update(chunk)
  fileobj.seek(start_position)
@@ -150,7 +149,7 @@ def _calculate_md5_from_file(fileobj):
 def conditionally_calculate_md5(params, **kwargs):
  """Only add a Content-MD5 when not using sigv4"""
  signer = kwargs['request_signer']
- if signer.signature_version not in ['v4', 's3v4']:
+ if signer.signature_version not in ['v4', 's3v4'] and MD5_AVAILABLE:
  calculate_md5(params, **kwargs)
 
 
@@ -188,13 +187,14 @@ def copy_source_sse_md5(params, **kwargs):
 def _sse_md5(params, sse_member_prefix='SSECustomer'):
  if not _needs_s3_sse_customization(params, sse_member_prefix):
  return
+
  sse_key_member = sse_member_prefix + 'Key'
  sse_md5_member = sse_member_prefix + 'KeyMD5'
  key_as_bytes = params[sse_key_member]
  if isinstance(key_as_bytes, six.text_type):
  key_as_bytes = key_as_bytes.encode('utf-8')
  key_md5_str = base64.b64encode(
- hashlib.md5(key_as_bytes).digest()).decode('utf-8')
+ get_md5(key_as_bytes).digest()).decode('utf-8')
  key_b64_encoded = base64.b64encode(key_as_bytes).decode('utf-8')
  params[sse_key_member] = key_b64_encoded
  params[sse_md5_member] = key_md5_str

tests/unit/test_compat.py

@@ -12,8 +12,12 @@
 # language governing permissions and limitations under the License.
 
 import datetime
+import mock
 
-from botocore.compat import total_seconds, unquote_str, six, ensure_bytes
+from botocore.exceptions import MD5UnavailableError
+from botocore.compat import (
+ total_seconds, unquote_str, six, ensure_bytes, get_md5
+)
 
 from tests import BaseEnvVar, unittest
 
@@ -78,3 +82,16 @@ def test_non_string_or_bytes_raises_error(self):
  value = 500
  with self.assertRaises(ValueError):
  ensure_bytes(value)
+
+
+class TestGetMD5(unittest.TestCase):
+ def test_available(self):
+ md5 = mock.Mock()
+ with mock.patch('botocore.compat.MD5_AVAILABLE', True):
+ with mock.patch('hashlib.md5', mock.Mock(return_value=md5)):
+ self.assertEqual(get_md5(), md5)
+
+ def test_unavailable_raises_error(self):
+ with mock.patch('botocore.compat.MD5_AVAILABLE', False):
+ with self.assertRaises(MD5UnavailableError):
+ get_md5()