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TimestampSigner not working as expected when I use a - as separator #62

avinassh opened this issue May 19, 2016 · 5 comments


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To produce the error:

from itsdangerous import TimestampSigner
s = TimestampSigner('secret-key', sep='-')
string = s.sign('foo')
s.unsign(string, max_age=50)

When I ran the above code multiple times in loop, I got following exceptions: SignatureExpired or BadTimeSignature.

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I can't reproduce either error with the example given. If you got a signature expired, then you waited longer than 50 seconds before unsigning.

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Nope, I am not waiting more than 50 seconds, I am just checking instantly. Here is an video demo where I am just copy pasting repeatedly and you will see both the errors:

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I used the same code which I had posted earlier. Now I am not sure why its not generating error in your machine.

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johnlam commented Jul 11, 2016

Here's what I think is going on.
The signature will be urlsafe_b64encode()d .
So part of the signature (and/or part of the timestamp) might contain your separator - , which would result in either a wrong timestamp or a wrong signature.

A potential fix could be to check if the separator is part of the base64_urlsafe() charset and/or write that in the docs.

How to reproduce.

for i in xrange(100):
    s = TimestampSigner('secret-key',sep='-')
    mystr = s.sign('foo')

Example string foo-CmVi_g-pt8iji6JAw61H0EJm-bFJumhEZw (signature will be bFJumhEZw instead of pt8iji6JAw61H0EJm-bFJumhEZw)

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I fixed it exactly as @johnlam described. I'm not considering this API breakage because this sort of usage never worked.

@davidism davidism added this to the 1.0.0 milestone Sep 28, 2018
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this issue Nov 10, 2018
Version 1.1.0

Released 2018-10-26

-   Change default signing algorithm back to SHA-1. (`#113`_)
-   Added a default SHA-512 fallback for users who used the yanked 1.0.0
    release which defaulted to SHA-512. (`#114`_)
-   Add support for fallback algorithms during deserialization to
    support changing the default in the future without breaking existing
    signatures. (`#113`_)
-   Changed capitalization of packages back to lowercase as the change
    in capitalization broke some tooling. (`#113`_)

.. _#113: pallets/itsdangerous#113
.. _#114: pallets/itsdangerous#114

Version 1.0.0

Released 2018-10-18


*Note*: This release was yanked from PyPI because it changed the default
algorithm to SHA-512. This decision was reverted in 1.1.0 and it remains
at SHA1.

-   Drop support for Python 2.6 and 3.3.
-   Refactor code from a single module to a package. Any object in the
    API docs is still importable from the top-level ``itsdangerous``
    name, but other imports will need to be changed. A future release
    will remove many of these compatibility imports. (`#107`_)
-   Optimize how timestamps are serialized and deserialized. (`#13`_)
-   ``base64_decode`` raises ``BadData`` when it is passed invalid data.
-   Ensure value is bytes when signing to avoid a ``TypeError`` on
    Python 3. (`#29`_)
-   Add a ``serializer_kwargs`` argument to ``Serializer``, which is
    passed to ``dumps`` during ``dump_payload``. (`#36`_)
-   More compact JSON dumps for unicode strings. (`#38`_)
-   Use the full timestamp rather than an offset, allowing dates before
    2011. (`#46`_)
-   Detect a ``sep`` character that may show up in the signature itself
    and raise a ``ValueError``. (`#62`_)
-   Use a consistent signature for keyword arguments for
    ``Serializer.load_payload`` in subclasses. (`#74`_, `#75`_)
-   Change default intermediate hash from SHA-1 to SHA-512. (`#80`_)
-   Convert JWS exp header to an int when loading. (`#99`_)

.. _#13: pallets/itsdangerous#13
.. _#27: pallets/itsdangerous#27
.. _#29: pallets/itsdangerous#29
.. _#36: pallets/itsdangerous#36
.. _#38: pallets/itsdangerous#38
.. _#46: pallets/itsdangerous#46
.. _#62: pallets/itsdangerous#62
.. _#74: pallets/itsdangerous#74
.. _#75: pallets/itsdangerous#75
.. _#80: pallets/itsdangerous#80
.. _#99: pallets/itsdangerous#99
.. _#107: pallets/itsdangerous#107
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