v1.1.0 - Added validation and line formatting, fixed zero-length padding. Added tests.

base64url.py

@@ -1,18 +1,16 @@
-"""URL-safe Base64 encoding without padding.
-
-This format uses only characters that are safe for URLs, filenames etc.
-Refer to Python's urlsafe_b64encode and base64.urlsafe_b64decode for more details.
+"""Base64 encoding in urlsafe format without padding.
 
 Fixes Python base64 module's faults:
-- Padding "==" is optional and not produced by b64url.enc
-- Base64 type is str (stdlib is retarded and uses bytes)
-- Otherwise identical to urlsafe_b64encode/urlsafe_b64decode
+- Padding "==" is optional and not produced by base64url.enc
+- Base64 type is str (stdlib uses bytes)
+- Doesn't silently ignore invalid characters and produce garbage
 """
 
-from base64 import urlsafe_b64decode as _decode
+# We cannot use urlsafe_b64decode which misses the validation argument
+from base64 import b64decode as _decode
 from base64 import urlsafe_b64encode as _encode
 
-__all__ = ["enc", "dec"]
+__all__ = ["enc", "dec", "enc_lines", "dec_lines"]
 
 
 def enc(data: bytes) -> str:
@@ -20,7 +18,30 @@ def enc(data: bytes) -> str:
     return _encode(data).decode("ascii").rstrip("=")
 
 
-def dec(s: str) -> bytes:
-    """Decode URL-safe Base64 into bytes. Padding optional."""
+def dec(s: str, *, validate=True) -> bytes:
+    """Decode standard or urlsafe Base64, with or without padding.
+
+    Validation raises binascii.Error (ValueError) on invalid characters.
+    If False, any unrecognized characters are silently ignored.
+    """
     # Testing whether needs padding is slower, this is the fastest way and constant time.
-    return _decode(s + "=" * (4 - (len(s) % 4)))
+    return _decode(s + -len(s) % 4 * "=", altchars=b"-_", validate=validate)
+
+
+def enc_lines(data: bytes, length: int = 76, sep="\n") -> str:
+    """Base64 encode bytes to a URL-safe string split into lines.
+
+    Returns a string with newlines inserted after every `length` characters.
+    The value should be a multiple of 4 for best compatibility with other systems.
+    """
+    s = enc(data)
+    return sep.join([s[i : i + length] for i in range(0, len(s), length)])
+
+
+def dec_lines(s: str) -> bytes:
+    """Decode standard or urlsafe Base64 from a multiline string.
+
+    All whitespace is ignored to allow formatted input.
+    Raises binascii.Error (ValueError) on other invalid characters.
+    """
+    return dec("".join(s.split()))