gh-125346: Fix decoding with non-standard Base64 alphabet #141128
Conversation
The "+" and "/" characters are no longer recognized as the part of the Base64 alphabet in base64.urlsafe_b64decode() and base64.b64decode() the altchars argument that does not contain them.
|
@serhiy-storchaka Thanks for this, can you link this PR to either the original issue or a new issue for tracking purposes. |
There was a problem hiding this comment.
I'm really concerned about the subtle breakages that this change could cause, especially because the default behavior is to throw away characters that aren't in the current alphabet. If the default behavior was to raise an error I would feel better about this change.
Makes me wonder if we should target validate=True with this behavior change (because IMO, the silent dropping of invalid characters is in itself a concerning behavior) and then long-term move to having validate be enabled by default?
There was a problem hiding this comment.
This worries me too. We can keep the old behavior but emit a warning if characters + or / occur in Base64 data with the alternative alphabet.
But urlsafe_b64decode() does not have the validate parameter.
I wonder if for |
|
But is not passing |
|
@serhiy-storchaka Yes maybe you're right that using |
|
If this is only for 3.15, then making validate=True by default will make the code more reliable by default. |
The "+" and "/" characters are no longer recognized as the part of the Base64 alphabet in base64.urlsafe_b64decode() and base64.b64decode() the altchars argument that does not contain them.