Description

DemiMarie

opened on Jul 9, 2022

Issue body actions

Bug report

The following code should raise binascii.Error but does not:

import binascii
binascii.a2b_base64(b'=aa==')

It appears (from looking at the source code) that this is also the case in 3.11, even in strict mode.

Your environment

• CPython versions tested on: 3.10
• Operating system and architecture: Fedora 36, Linux 5.15.52, x86_64

Activity

1. DemiMarie

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Jul 9, 2022
2. yourlefthandman commented on Jul 9, 2022

   

   yourlefthandman

   on Jul 9, 2022

   Contributor

   More actions

   When running the code from main, the behaviour is as you expect it to be :)

   >>> binascii.a2b_base64(b'=aa==', strict_mode=True)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   binascii.Error: Leading padding not allowed
   

   The following code handles it-

   if (strict_mode && ascii_len > 0 && ascii_data[0] == '=') {
       state = get_binascii_state(module);
       if (state) {
           PyErr_SetString(state->Error, "Leading padding not allowed");
       }
       goto error_end;
   }
   

   Looking at 3.11, i see the code is there too - link
3. DemiMarie commented on Jul 10, 2022

   

   DemiMarie

   on Jul 10, 2022

   Author

   More actions

   Does it reject this input?

   import binascii
   binascii.a2b_base64(b'aaaa=aa==', strict_mode=True)
   

   ?
4. yourlefthandman commented on Jul 10, 2022

   

   yourlefthandman

   on Jul 10, 2022

   Contributor

   More actions

   Yup :)

   >>> import binascii
   >>> binascii.a2b_base64(b'aaaa=aa==', strict_mode=True)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   binascii.Error: Discontinuous padding not allowed
   
5. Mohitduklan commented on Jul 24, 2022

   

   Mohitduklan

   on Jul 24, 2022

   More actions

   Is it because python 3.10.5 uses REF 4648. https://docs.python.org/3/library/base64.html
6. idan22moral commented on Nov 4, 2022

   

   idan22moral

   on Nov 4, 2022

   Contributor

   More actions

   Hi @DemiMarie,
   This behavior is normal in 3.10, since the strict_mode flag was not introduced yet.
   In 3.11.0 it behaves as expected:

   Python 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)] on win32
   Type "help", "copyright", "credits" or "license" for more information.
   >>> import binascii
   >>> binascii.a2b_base64(b'=aa==')
   b'i'
   >>> binascii.a2b_base64(b'=aa==', strict_mode=True)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   binascii.Error: Leading padding not allowed
   >>> binascii.a2b_base64(b'aaaa=aa==')
   b'i\xa6\x9ai'
   >>> binascii.a2b_base64(b'aaaa=aa==', strict_mode=True)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   binascii.Error: Discontinuous padding not allowed
   

   For further information, please read:

   • https://docs.python.org/3/library/binascii.html?highlight=strict_mode#binascii.a2b_base64
   • bpo-43086: Added handling for excess data in binascii.a2b_base64 #24402
7. DemiMarie

   closed this as completedon Nov 4, 2022

Issue actions