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150 lines
6.9 KiB
150 lines
6.9 KiB
Frequently asked questions
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==========================
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``cryptography`` failed to install!
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-----------------------------------
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If you are having issues installing ``cryptography`` the first troubleshooting
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step is to upgrade ``pip`` and then try to install again. For most users this will
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take the form of ``pip install -U pip``, but on Windows you should do
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``python -m pip install -U pip``. If you are still seeing errors after upgrading
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and trying ``pip install cryptography`` again, please see the :doc:`/installation`
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documentation.
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How does ``cryptography`` compare to NaCl (Networking and Cryptography Library)?
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--------------------------------------------------------------------------------
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While ``cryptography`` and `NaCl`_ both share the goal of making cryptography
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easier, and safer, to use for developers, ``cryptography`` is designed to be a
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general purpose library, interoperable with existing systems, while NaCl
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features a collection of hand selected algorithms.
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``cryptography``'s :ref:`recipes <cryptography-layout>` layer has similar goals
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to NaCl.
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If you prefer NaCl's design, we highly recommend `PyNaCl`_, which is also
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maintained by the PyCA team.
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Why use ``cryptography``?
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-------------------------
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If you've done cryptographic work in Python before you have likely encountered
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other libraries in Python such as *M2Crypto*, *PyCrypto*, or *PyOpenSSL*. In
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building ``cryptography`` we wanted to address a few issues we observed in the
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legacy libraries:
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* Extremely error prone APIs and insecure defaults.
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* Use of poor implementations of algorithms (i.e. ones with known side-channel
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attacks).
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* Lack of maintenance.
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* Lack of high level APIs.
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* Lack of PyPy and Python 3 support.
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* Absence of algorithms such as
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:class:`AES-GCM <cryptography.hazmat.primitives.ciphers.modes.GCM>` and
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:class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`.
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Compiling ``cryptography`` on macOS produces a ``fatal error: 'openssl/aes.h' file not found`` error
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----------------------------------------------------------------------------------------------------
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This happens because macOS 10.11 no longer includes a copy of OpenSSL.
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``cryptography`` now provides wheels which include a statically linked copy of
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OpenSSL. You're seeing this error because your copy of pip is too old to find
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our wheel files. Upgrade your copy of pip with ``pip install -U pip`` and then
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try install ``cryptography`` again.
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If you are using PyPy, we do not currently ship ``cryptography`` wheels for
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PyPy. You will need to install your own copy of OpenSSL -- we recommend using
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Homebrew.
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``cryptography`` raised an ``InternalError`` and I'm not sure what to do?
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-------------------------------------------------------------------------
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Frequently ``InternalError`` is raised when there are errors on the OpenSSL
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error stack that were placed there by other libraries that are also using
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OpenSSL. Try removing the other libraries and see if the problem persists.
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If you have no other libraries using OpenSSL in your process, or they do not
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appear to be at fault, it's possible that this is a bug in ``cryptography``.
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Please file an `issue`_ with instructions on how to reproduce it.
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error: ``-Werror=sign-conversion``: No option ``-Wsign-conversion`` during installation
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---------------------------------------------------------------------------------------
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The compiler you are using is too old and not supported by ``cryptography``.
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Please upgrade to a more recent version. If you are running OpenBSD 6.1 or
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earlier the default compiler is extremely old. Use ``pkg_add`` to install a
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newer ``gcc`` and then install ``cryptography`` using
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``CC=/path/to/newer/gcc pip install cryptography``.
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Installing ``cryptography`` fails with ``Invalid environment marker: python_version < '3'``
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-------------------------------------------------------------------------------------------
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Your ``pip`` and/or ``setuptools`` are outdated. Please upgrade to the latest
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versions with ``pip install -U pip setuptools`` (or on Windows
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``python -m pip install -U pip setuptools``).
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Installing cryptography with OpenSSL 0.9.8 or 1.0.0 fails
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---------------------------------------------------------
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The OpenSSL project has dropped support for the 0.9.8 and 1.0.0 release series.
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Since they are no longer receiving security patches from upstream,
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``cryptography`` is also dropping support for them. To fix this issue you
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should upgrade to a newer version of OpenSSL (1.0.2 or later). This may require
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you to upgrade to a newer operating system.
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Why are there no wheels for Python 3.5+ on Linux or macOS?
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----------------------------------------------------------
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Our Python3 wheels, for macOS and Linux, are ``abi3`` wheels. This means they
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support multiple versions of Python. The Python 3.4 ``abi3`` wheel can be used
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with any version of Python greater than or equal to 3.4. Recent versions of
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``pip`` will automatically install ``abi3`` wheels.
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``ImportError``: ``idna`` is not installed
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------------------------------------------
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``cryptography`` deprecated passing :term:`U-label` strings to various X.509
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constructors in version 2.1 and in version 2.5 moved the ``idna`` dependency
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to a ``setuptools`` extra. If you see this exception you should upgrade your
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software so that it no longer depends on this deprecated feature. If that is
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not yet possible you can also install ``cryptography`` with
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``pip install cryptography[idna]`` to automatically install the missing
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dependency. This workaround will be available until the feature is fully
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removed.
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Why can't I import my PEM file?
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-------------------------------
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PEM is a format (defined by several RFCs, but originally :rfc:`1421`) for
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encoding keys, certificates and others cryptographic data into a regular form.
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The data is encoded as base64 and wrapped with a header and footer.
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If you are having trouble importing PEM files, make sure your file fits
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the following rules:
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* has a one-line header like this: ``-----BEGIN [FILE TYPE]-----``
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(where ``[FILE TYPE]`` is ``CERTIFICATE``, ``PUBLIC KEY``, ``PRIVATE KEY``,
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etc.)
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* has a one-line footer like this: ``-----END [FILE TYPE]-----``
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* all lines, except for the final one, must consist of exactly 64
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characters.
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For example, this is a PEM file for a RSA Public Key: ::
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-----BEGIN PUBLIC KEY-----
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MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7CsKFSzq20NLb2VQDXma
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9DsDXtKADv0ziI5hT1KG6Bex5seE9pUoEcUxNv4uXo2jzAUgyRweRl/DLU8SoN8+
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WWd6YWik4GZvNv7j0z28h9Q5jRySxy4dmElFtIRHGiKhqd1Z06z4AzrmKEzgxkOk
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LJjY9cvwD+iXjpK2oJwNNyavvjb5YZq6V60RhpyNtKpMh2+zRLgIk9sROEPQeYfK
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22zj2CnGBMg5Gm2uPOsGDltl/I/Fdh1aO3X4i1GXwCuPf1kSAg6lPJD0batftkSG
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v0X0heUaV0j1HSNlBWamT4IR9+iJfKJHekOqvHQBcaCu7Ja4kXzx6GZ3M2j/Ja3A
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2QIDAQAB
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-----END PUBLIC KEY-----
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.. _`NaCl`: https://nacl.cr.yp.to/
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.. _`PyNaCl`: https://pynacl.readthedocs.io
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.. _`WSGIApplicationGroup`: https://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIApplicationGroup.html
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.. _`issue`: https://github.com/pyca/cryptography/issues
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