FortunaAccumulator: Use time.monotonic if available (i.e. Python 3.3 and later)

2 files changed, 33 insertions, 2 deletions

diff --git a/lib/Crypto/Random/Fortuna/FortunaAccumulator.py b/lib/Crypto/Random/Fortuna/FortunaAccumulator.py
index 5ebbe2b..42e998c 100644
--- a/lib/Crypto/Random/Fortuna/FortunaAccumulator.py
+++ b/lib/Crypto/Random/Fortuna/FortunaAccumulator.py
@@ -36,6 +36,9 @@ import warnings
 from Crypto.pct_warnings import ClockRewindWarning
 import SHAd256
 
+# If the system has monotonic time, we'll use it.
+from Crypto.Util._time import maybe_monotonic_time
+
 import FortunaGenerator
 
 class FortunaPool(object):
@@ -110,7 +113,7 @@ class FortunaAccumulator(object):
         assert(self.pools[0] is not self.pools[1])
 
     def random_data(self, bytes):
-        current_time = time.time()
+        current_time = maybe_monotonic_time()
         if (self.last_reseed is not None and self.last_reseed > current_time): # Avoid float comparison to None to make Py3k happy
             warnings.warn("Clock rewind detected. Resetting last_reseed.", ClockRewindWarning)
             self.last_reseed = None
@@ -123,7 +126,7 @@ class FortunaAccumulator(object):
 
     def _reseed(self, current_time=None):
         if current_time is None:
-            current_time = time.time()
+            current_time = maybe_monotonic_time()
         seed = []
         self.reseed_count += 1
         self.last_reseed = current_time
diff --git a/lib/Crypto/Util/_time.py b/lib/Crypto/Util/_time.py
new file mode 100644
index 0000000..ff4c6a9
--- /dev/null
+++ b/lib/Crypto/Util/_time.py
@@ -0,0 +1,28 @@
+# -*- coding: ascii -*-
+#
+#  _time.py : Internal monotonic time module.
+#
+# Written in 2013 by Dwayne C. Litzenberger <dlitz@dlitz.net>
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain.  To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+try:
+    from time import monotonic as maybe_monotonic_time
+except ImportError:
+    from time import time as maybe_monotonic_time