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- Frequently asked questions
- ==========================
- .. _faq-howto-handle-deprecation-warning:
- I cannot suppress the deprecation warning that ``cryptography`` emits on import
- -------------------------------------------------------------------------------
- .. hint::
- The deprecation warning emitted on import does not inherit
- :py:exc:`DeprecationWarning` but inherits :py:exc:`UserWarning`
- instead.
- If your pytest setup follows the best practices of failing on
- emitted warnings (``filterwarnings = error``), you may ignore it
- by adding the following line at the end of the list::
- ignore:Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in a future release.:UserWarning
- **Note:** Using ``cryptography.utils.CryptographyDeprecationWarning``
- is not possible here because specifying it triggers
- ``import cryptography`` internally that emits the warning before
- the ignore rule even kicks in.
- Ref: https://github.com/pytest-dev/pytest/issues/7524
- The same applies when you use :py:func:`~warnings.filterwarnings` in
- your code or invoke CPython with :std:option:`-W` command line option.
- ``cryptography`` failed to install!
- -----------------------------------
- If you are having issues installing ``cryptography`` the first troubleshooting
- step is to upgrade ``pip`` and then try to install again. For most users this will
- take the form of ``pip install -U pip``, but on Windows you should do
- ``python -m pip install -U pip``. If you are still seeing errors after upgrading
- and trying ``pip install cryptography`` again, please see the :doc:`/installation`
- documentation.
- How does ``cryptography`` compare to NaCl (Networking and Cryptography Library)?
- --------------------------------------------------------------------------------
- While ``cryptography`` and `NaCl`_ both share the goal of making cryptography
- easier, and safer, to use for developers, ``cryptography`` is designed to be a
- general purpose library, interoperable with existing systems, while NaCl
- features a collection of hand selected algorithms.
- ``cryptography``'s :ref:`recipes <cryptography-layout>` layer has similar goals
- to NaCl.
- If you prefer NaCl's design, we highly recommend `PyNaCl`_, which is also
- maintained by the PyCA team.
- Why use ``cryptography``?
- -------------------------
- If you've done cryptographic work in Python before you have likely encountered
- other libraries in Python such as *M2Crypto*, *PyCrypto*, or *PyOpenSSL*. In
- building ``cryptography`` we wanted to address a few issues we observed in the
- legacy libraries:
- * Extremely error prone APIs and insecure defaults.
- * Use of poor implementations of algorithms (i.e. ones with known side-channel
- attacks).
- * Lack of maintenance.
- * Lack of high level APIs.
- * Lack of PyPy and Python 3 support.
- * Absence of algorithms such as
- :class:`AES-GCM <cryptography.hazmat.primitives.ciphers.modes.GCM>` and
- :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`.
- Installing ``cryptography`` produces a ``fatal error: 'openssl/opensslv.h' file not found`` error
- -------------------------------------------------------------------------------------------------
- ``cryptography`` provides wheels which include a statically linked copy of
- OpenSSL. If you see this error it is likely because your copy of ``pip`` is too
- old to find our wheel files. Upgrade your ``pip`` with ``pip install -U pip``
- and then try to install ``cryptography`` again.
- Users on PyPy, unusual CPU architectures, or distributions of Linux using
- ``musl`` (like Alpine) will need to compile ``cryptography`` themselves. Please
- view our :doc:`/installation` documentation.
- ``cryptography`` raised an ``InternalError`` and I'm not sure what to do?
- -------------------------------------------------------------------------
- Frequently ``InternalError`` is raised when there are errors on the OpenSSL
- error stack that were placed there by other libraries that are also using
- OpenSSL. Try removing the other libraries and see if the problem persists.
- If you have no other libraries using OpenSSL in your process, or they do not
- appear to be at fault, it's possible that this is a bug in ``cryptography``.
- Please file an `issue`_ with instructions on how to reproduce it.
- error: ``-Werror=sign-conversion``: No option ``-Wsign-conversion`` during installation
- ---------------------------------------------------------------------------------------
- The compiler you are using is too old and not supported by ``cryptography``.
- Please upgrade to a more recent version. If you are running OpenBSD 6.1 or
- earlier the default compiler is extremely old. Use ``pkg_add`` to install a
- newer ``gcc`` and then install ``cryptography`` using
- ``CC=/path/to/newer/gcc pip install cryptography``.
- Installing ``cryptography`` fails with ``Invalid environment marker: python_version < '3'``
- -------------------------------------------------------------------------------------------
- Your ``pip`` and/or ``setuptools`` are outdated. Please upgrade to the latest
- versions with ``pip install -U pip setuptools`` (or on Windows
- ``python -m pip install -U pip setuptools``).
- Installing cryptography with OpenSSL 0.9.8, 1.0.0, 1.0.1, 1.0.2 fails
- ---------------------------------------------------------------------
- The OpenSSL project has dropped support for the 0.9.8, 1.0.0, 1.0.1, and 1.0.2
- release series. Since they are no longer receiving security patches from
- upstream, ``cryptography`` is also dropping support for them. To fix this issue
- you should upgrade to a newer version of OpenSSL (1.1.0 or later). This may
- require you to upgrade to a newer operating system.
- Why are there no wheels for my Python3.x version?
- -------------------------------------------------
- Our Python3 wheels are ``abi3`` wheels. This means they support multiple
- versions of Python. The ``abi3`` wheel can be used with any version of Python
- greater than or equal to the version it specifies. Recent versions of ``pip``
- will automatically install ``abi3`` wheels.
- Why can't I import my PEM file?
- -------------------------------
- PEM is a format (defined by several RFCs, but originally :rfc:`1421`) for
- encoding keys, certificates and others cryptographic data into a regular form.
- The data is encoded as base64 and wrapped with a header and footer.
- If you are having trouble importing PEM files, make sure your file fits
- the following rules:
- * has a one-line header like this: ``-----BEGIN [FILE TYPE]-----``
- (where ``[FILE TYPE]`` is ``CERTIFICATE``, ``PUBLIC KEY``, ``PRIVATE KEY``,
- etc.)
- * has a one-line footer like this: ``-----END [FILE TYPE]-----``
- * all lines, except for the final one, must consist of exactly 64
- characters.
- For example, this is a PEM file for a RSA Public Key: ::
- -----BEGIN PUBLIC KEY-----
- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7CsKFSzq20NLb2VQDXma
- 9DsDXtKADv0ziI5hT1KG6Bex5seE9pUoEcUxNv4uXo2jzAUgyRweRl/DLU8SoN8+
- WWd6YWik4GZvNv7j0z28h9Q5jRySxy4dmElFtIRHGiKhqd1Z06z4AzrmKEzgxkOk
- LJjY9cvwD+iXjpK2oJwNNyavvjb5YZq6V60RhpyNtKpMh2+zRLgIk9sROEPQeYfK
- 22zj2CnGBMg5Gm2uPOsGDltl/I/Fdh1aO3X4i1GXwCuPf1kSAg6lPJD0batftkSG
- v0X0heUaV0j1HSNlBWamT4IR9+iJfKJHekOqvHQBcaCu7Ja4kXzx6GZ3M2j/Ja3A
- 2QIDAQAB
- -----END PUBLIC KEY-----
- .. _`NaCl`: https://nacl.cr.yp.to/
- .. _`PyNaCl`: https://pynacl.readthedocs.io
- .. _`WSGIApplicationGroup`: https://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIApplicationGroup.html
- .. _`issue`: https://github.com/pyca/cryptography/issues
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