Merge 61177c2 into 5353c4a

CHANGES.rst

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+unreleased
+-------
+
+* Remove padding characters from encoded string.
+
 1.1.1
 -------
 

README.rst

@@ -14,7 +14,7 @@ Encoding and decoding arbitrary strings into strings that are safe to put into a
 The problem
 -----------
 
-`urlsafe_b64encode` and `urlsafe_b64decode` from base64 are not enough because they leave `=` chars unquoted:
+`urlsafe_b64encode` and `urlsafe_b64decode` from base64 are not enough because they leave `=` used for padding chars unquoted:
 
 .. code-block:: python
 
@@ -45,8 +45,10 @@ II. Some libraries tolerate the `=` in query string values:
 
 but the RFC 3986 underspecifies the query string so we cannot rely on `=` chars being handled by all web applications as it is done by urlparse.
 
-Therefore we consider chars: `['+', '/', '=']` unsafe and we replace them with `['-', '_', '.']`. Characters `+` and `/` are already handled by `urlsafe_*` functions from base64 so only `=` is left for us. The `.` character has been chosen because it often appears in real world query strings and it is not used
-by base64.
+Therefore we consider chars: `['+', '/', '=']` unsafe and we replace them with `['-', '_', '.']`.
+Characters `+` and `/` are already handled by `urlsafe_*` functions from base64 so only `=` is left.
+Since the `=` is used exclusively for padding, we simply remove it, and re-attach the padding during decoding.
+Because of that, `querystringsafe_base64` is able to decode padded and unpadded string.
 
 The solution
 ------------
@@ -56,7 +58,10 @@ The solution
     import querystringsafe_base64
 
     querystringsafe_base64.encode(b'foo-bar')
-    b'Zm9vLWJhcg..'
+    b'Zm9vLWJhcg'
 
     querystringsafe_base64.decode(b'Zm9vLWJhcg..')
     b'foo-bar'
+
+    querystringsafe_base64.decode(b'Zm9vLWJhcg')
+    b'foo-bar'

src/querystringsafe_base64/__init__.py

@@ -39,7 +39,7 @@ def fill_padding(padded_string):
     length = len(padded_string)
     reminder = len(padded_string) % 4
     if reminder:
-        return padded_string.ljust(length + 4 - reminder, b'.')
+        return padded_string.ljust(length + 4 - reminder, b'=')
     return padded_string
 
 
@@ -57,7 +57,7 @@ def encode(to_encode):
         string - like base64, except characters ['+', '/', '='] are
         replaced with ['-', '_', '.'] consequently
     """
-    return urlsafe_b64encode(to_encode).replace(b'=', b'.')
+    return urlsafe_b64encode(to_encode).strip(b'=')
 
 
 def decode(encoded):
@@ -76,4 +76,4 @@ def decode(encoded):
     :return: decoded string
     """
     padded_string = fill_padding(encoded)
-    return urlsafe_b64decode(padded_string.replace(b'.', b'='))
+    return urlsafe_b64decode(padded_string)

tests/test_encode_decode.py

@@ -115,6 +115,6 @@ def test_encode_decode_unpad(string_num):
     original = test_strings[string_num]
 
     encoded = querystringsafe_base64.encode(original)
-    assert encoded.endswith(b'.')  # make sure it ends with padding for this test
+    assert len(encoded) % 4 != 0  # make sure it would end with padding
     decoded = querystringsafe_base64.decode(encoded.rstrip())
     assert decoded == original