Created utils.py to hold functions like constant_time_compare and base64-encoding

1 files changed, 39 insertions, 0 deletions

diff --git a/jwt/utils.py b/jwt/utils.py
new file mode 100644
index 0000000..16000b5
--- /dev/null
+++ b/jwt/utils.py
@@ -0,0 +1,39 @@
+import base64
+import hmac
+
+def base64url_decode(input):
+    rem = len(input) % 4
+
+    if rem > 0:
+        input += b'=' * (4 - rem)
+
+    return base64.urlsafe_b64decode(input)
+
+
+def base64url_encode(input):
+    return base64.urlsafe_b64encode(input).replace(b'=', b'')
+
+try:
+    constant_time_compare = hmac.compare_digest
+except AttributeError:
+    # Fallback for Python < 2.7.7 and Python < 3.3
+    def constant_time_compare(val1, val2):
+        """
+        Returns True if the two strings are equal, False otherwise.
+
+        The time taken is independent of the number of characters that match.
+        """
+        if len(val1) != len(val2):
+            return False
+
+        result = 0
+
+        if sys.version_info >= (3, 0, 0):
+            # Bytes are numbers
+            for x, y in zip(val1, val2):
+                result |= x ^ y
+        else:
+            for x, y in zip(val1, val2):
+                result |= ord(x) ^ ord(y)
+
+        return result == 0