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Acceptable password hashing for your software and your servers (but you should really use argon2id or scrypt)
To install bcrypt, simply:
.. code:: bash
$ pip install bcryptNote that bcrypt should build very easily on Linux provided you have a C compiler and a Rust compiler (the minimum supported Rust version is 1.56.0).
For Debian and Ubuntu, the following command will ensure that the required dependencies are installed:
.. code:: bash
$ sudo apt-get install build-essential cargoFor Fedora and RHEL-derivatives, the following command will ensure that the required dependencies are installed:
.. code:: bash
$ sudo yum install gcc cargoFor Alpine, the following command will ensure that the required dependencies are installed:
.. code:: bash
$ apk add --update musl-dev gcc cargoWhile bcrypt remains an acceptable choice for password storage, depending on your specific use case you may also want to consider using scrypt (either via standard library or cryptography) or argon2id via argon2_cffi_.
BCRYPT_ALLOW_RUST_163 environment variable.py37 and py39 wheels. This should resolve some errors
relating to initializing a module multiple times per process.kdf method.BCRYPT_ALLOW_RUST_163 environment variable)manylinux wheels.salt to checkpw could result in
a pyo3_runtime.PanicException. It now correctly raises a ValueError.bcrypt is now implemented in Rust. Users building from source will need
to have a Rust compiler available. Nothing will change for users downloading
wheels.manylinux2010 wheels. Users should upgrade to the latest
pip to ensure this doesn’t cause issues downloading wheels on their
platform. We now ship manylinux_2_28 wheels for users on new enough platforms.NUL bytes are now allowed in inputs.py.typed files in wheels so that mypy works.bcrypt with be 4.0 and it will require Rust at
compile time, for users building from source. There will be no additional
requirement for users who are installing from wheels. Users on most
platforms will be able to obtain a wheel by making sure they have an up to
date pip. The minimum supported Rust version will be 1.56.0.manylinux2010 wheels.
Going forward the minimum supported manylinux ABI for our wheels will be
manylinux2014. The vast majority of users will continue to receive
manylinux wheels provided they have an up to date pip.abi3 Windows wheels (requires pip >= 20).setuptools lower bound for PEP517 wheel building.manylinux1 wheels. Continuing to produce
them was a maintenance burden.abi3 wheels for Python 3. If you are not getting a
wheel on a compatible platform please upgrade your pip version.kdf.UserWarning when used with cffi 1.8.3.checkpw, a convenience method for verifying a password.$2y$ hash when you input a $2y$ salt.$2a hashes were vulnerable to a wraparound bug.bcrypt_pbkdf via the kdf function.gensalt.Password Hashing
Hashing and then later checking that a password matches the previous hashed
password is very simple:
.. code:: pycon
>>> import bcrypt
>>> password = b"super secret password"
>>> # Hash a password for the first time, with a randomly-generated salt
>>> hashed = bcrypt.hashpw(password, bcrypt.gensalt())
>>> # Check that an unhashed password matches one that has previously been
>>> # hashed
>>> if bcrypt.checkpw(password, hashed):
... print("It Matches!")
... else:
... print("It Does not Match :(")
KDFAs of 3.0.0 bcrypt now offers a kdf function which does bcrypt_pbkdf.
This KDF is used in OpenSSH's newer encrypted private key format.
.. code:: pycon
>>> import bcrypt
>>> key = bcrypt.kdf(
... password=b'password',
... salt=b'salt',
... desired_key_bytes=32,
... rounds=100)Adjustable Work Factor
One of bcrypt's features is an adjustable logarithmic work factor. To adjust
the work factor merely pass the desired number of rounds to
``bcrypt.gensalt(rounds=12)`` which defaults to 12):
.. code:: pycon
>>> import bcrypt
>>> password = b"super secret password"
>>> # Hash a password for the first time, with a certain number of rounds
>>> hashed = bcrypt.hashpw(password, bcrypt.gensalt(14))
>>> # Check that a unhashed password matches one that has previously been
>>> # hashed
>>> if bcrypt.checkpw(password, hashed):
... print("It Matches!")
... else:
... print("It Does not Match :(")
Adjustable PrefixAnother one of bcrypt's features is an adjustable prefix to let you define what
libraries you'll remain compatible with. To adjust this, pass either 2a or
2b (the default) to bcrypt.gensalt(prefix=b"2b") as a bytes object.
As of 3.0.0 the $2y$ prefix is still supported in hashpw but deprecated.
Maximum Password Length
The bcrypt algorithm only handles passwords up to 72 characters, any characters
beyond that are ignored. To work around this, a common approach is to hash a
password with a cryptographic hash (such as ``sha256``) and then base64
encode it to prevent NULL byte problems before hashing the result with
``bcrypt``:
.. code:: pycon
>>> password = b"an incredibly long password" * 10
>>> hashed = bcrypt.hashpw(
... base64.b64encode(hashlib.sha256(password).digest()),
... bcrypt.gensalt()
... )
Compatibility
-------------
This library should be compatible with py-bcrypt and it will run on Python
3.6+, and PyPy 3.
Security
--------
``bcrypt`` follows the `same security policy as cryptography`_, if you
identify a vulnerability, we ask you to contact us privately.
.. _`same security policy as cryptography`: https://cryptography.io/en/latest/security.html
.. _`standard library`: https://docs.python.org/3/library/hashlib.html#hashlib.scrypt
.. _`argon2_cffi`: https://argon2-cffi.readthedocs.io
.. _`cryptography`: https://cryptography.io/en/latest/hazmat/primitives/key-derivation-functions/#cryptography.hazmat.primitives.kdf.scrypt.Scrypt