diff options
Diffstat (limited to 'docs/hazmat')
| -rw-r--r-- | docs/hazmat/backends/interfaces.rst | 14 | ||||
| -rw-r--r-- | docs/hazmat/primitives/asymmetric/rsa.rst | 98 | ||||
| -rw-r--r-- | docs/hazmat/primitives/key-derivation-functions.rst | 92 | ||||
| -rw-r--r-- | docs/hazmat/primitives/symmetric-encryption.rst | 2 |
4 files changed, 169 insertions, 37 deletions
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst index f363b541..1e1a6b28 100644 --- a/docs/hazmat/backends/interfaces.rst +++ b/docs/hazmat/backends/interfaces.rst @@ -275,6 +275,14 @@ A specific ``backend`` may provide one or more of these interfaces. :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` provider. + :return bytes: The decrypted data. + + :raises cryptography.exceptions.UnsupportedAlgorithm: If an unsupported + MGF, hash function, or padding is chosen. + + :raises ValueError: When decryption fails or key size does not match + ciphertext length. + .. method:: encrypt_rsa(public_key, plaintext, padding) :param public_key: An instance of an @@ -287,6 +295,12 @@ A specific ``backend`` may provide one or more of these interfaces. :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` provider. + :return bytes: The encrypted data. + + :raises cryptography.exceptions.UnsupportedAlgorithm: If an unsupported + MGF, hash function, or padding is chosen. + + :raises ValueError: When plaintext is too long for the key size. .. class:: TraditionalOpenSSLSerializationBackend diff --git a/docs/hazmat/primitives/asymmetric/rsa.rst b/docs/hazmat/primitives/asymmetric/rsa.rst index 2700154c..234a5c66 100644 --- a/docs/hazmat/primitives/asymmetric/rsa.rst +++ b/docs/hazmat/primitives/asymmetric/rsa.rst @@ -85,7 +85,10 @@ RSA :param padding: An instance of a :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` - provider. + provider. Valid values are + :class:`~cryptography.hazmat.primitives.asymmetric.padding.PSS` and + :class:`~cryptography.hazmat.primitives.asymmetric.padding.PKCS1v15` + (``PSS`` is recommended for all new applications). :param algorithm: An instance of a :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` @@ -154,21 +157,39 @@ RSA :class:`~cryptography.hazmat.primitives.asymmetric.padding.OAEP` it may also be raised for invalid label values. - .. code-block:: python + .. doctest:: - from cryptography.hazmat.backends import default_backend - from cryptography.hazmat.primitives import hashes - from cryptography.hazmat.primitives.asymmetric import padding + >>> from cryptography.hazmat.backends import default_backend + >>> from cryptography.hazmat.primitives import hashes + >>> from cryptography.hazmat.primitives.asymmetric import padding - plaintext = private_key.decrypt( - ciphertext, - padding.OAEP( - mgf=padding.MGF1(algorithm=hashes.SHA1()), - algorithm=hashes.SHA1(), - label=None - ), - default_backend() - ) + >>> # Generate a key + >>> private_key = rsa.RSAPrivateKey.generate( + ... public_exponent=65537, + ... key_size=2048, + ... backend=default_backend() + ... ) + >>> public_key = private_key.public_key() + >>> # encrypt some data + >>> ciphertext = public_key.encrypt( + ... b"encrypted data", + ... padding.OAEP( + ... mgf=padding.MGF1(algorithm=hashes.SHA1()), + ... algorithm=hashes.SHA1(), + ... label=None + ... ), + ... default_backend() + ... ) + >>> # Now do the actual decryption + >>> plaintext = private_key.decrypt( + ... ciphertext, + ... padding.OAEP( + ... mgf=padding.MGF1(algorithm=hashes.SHA1()), + ... algorithm=hashes.SHA1(), + ... label=None + ... ), + ... default_backend() + ... ) .. class:: RSAPublicKey(public_exponent, modulus) @@ -236,7 +257,10 @@ RSA :param padding: An instance of a :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding` - provider. + provider. Valid values are + :class:`~cryptography.hazmat.primitives.asymmetric.padding.PSS` and + :class:`~cryptography.hazmat.primitives.asymmetric.padding.PKCS1v15` + (``PSS`` is recommended for all new applications). :param algorithm: An instance of a :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` @@ -306,27 +330,29 @@ RSA :class:`~cryptography.hazmat.primitives.asymmetric.padding.OAEP` it may also be raised for invalid label values. - .. code-block:: python - - from cryptography.hazmat.backends import default_backend - from cryptography.hazmat.primitives import hashes - from cryptography.hazmat.primitives.asymmetric import padding, rsa - - private_key = rsa.RSAPrivateKey.generate( - public_exponent=65537, - key_size=2048, - backend=default_backend() - ) - public_key = private_key.public_key() - ciphertext = public_key.encrypt( - plaintext, - padding.OAEP( - mgf=padding.MGF1(algorithm=hashes.SHA1()), - algorithm=hashes.SHA1(), - label=None - ), - default_backend() - ) + .. doctest:: + + >>> from cryptography.hazmat.backends import default_backend + >>> from cryptography.hazmat.primitives import hashes + >>> from cryptography.hazmat.primitives.asymmetric import padding + + >>> # Generate a key + >>> private_key = rsa.RSAPrivateKey.generate( + ... public_exponent=65537, + ... key_size=2048, + ... backend=default_backend() + ... ) + >>> public_key = private_key.public_key() + >>> # encrypt some data + >>> ciphertext = public_key.encrypt( + ... b"encrypted data", + ... padding.OAEP( + ... mgf=padding.MGF1(algorithm=hashes.SHA1()), + ... algorithm=hashes.SHA1(), + ... label=None + ... ), + ... default_backend() + ... ) Handling partial RSA private keys diff --git a/docs/hazmat/primitives/key-derivation-functions.rst b/docs/hazmat/primitives/key-derivation-functions.rst index ee8f8ab6..de6bf5f8 100644 --- a/docs/hazmat/primitives/key-derivation-functions.rst +++ b/docs/hazmat/primitives/key-derivation-functions.rst @@ -219,6 +219,98 @@ Different KDFs are suitable for different tasks such as: ``key_material`` generates the same key as the ``expected_key``, and raises an exception if they do not match. + +.. class:: HKDFExpand(algorithm, length, info, backend) + + .. versionadded:: 0.5 + + HKDF consists of two stages, extract and expand. This class exposes an + expand only version of HKDF that is suitable when the key material is + already cryptographically strong. + + .. warning:: + + HKDFExpand should only be used if the key material is + cryptographically strong. You should use + :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF` if + you are unsure. + + .. doctest:: + + >>> import os + >>> from cryptography.hazmat.primitives import hashes + >>> from cryptography.hazmat.primitives.kdf.hkdf import HKDFExpand + >>> from cryptography.hazmat.backends import default_backend + >>> backend = default_backend() + >>> info = b"hkdf-example" + >>> key_material = os.urandom(16) + >>> hkdf = HKDFExpand( + ... algorithm=hashes.SHA256(), + ... length=32, + ... info=info, + ... backend=backend + ... ) + >>> key = hkdf.derive(key_material) + >>> hkdf = HKDFExpand( + ... algorithm=hashes.SHA256(), + ... length=32, + ... info=info, + ... backend=backend + ... ) + >>> hkdf.verify(key_material, key) + + :param algorithm: An instance of a + :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` + provider. + + :param int length: The desired length of the derived key. Maximum is + ``255 * (algorithm.digest_size // 8)``. + + :param bytes info: Application specific context information. If ``None`` + is explicitly passed an empty byte string will be used. + + :param backend: A + :class:`~cryptography.hazmat.backends.interfaces.HMACBackend` + provider. + + :raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if the + provided ``backend`` does not implement + :class:`~cryptography.hazmat.backends.interfaces.HMACBackend` + :raises TypeError: This is raised if the provided ``info`` is a unicode object + + .. method:: derive(key_material) + + :param bytes key_material: The input key material. + :return bytes: The derived key. + + :raises TypeError: This is raised if the provided ``key_material`` is + a unicode object + + Derives a new key from the input key material by performing both the + extract and expand operations. + + .. method:: verify(key_material, expected_key) + + :param key_material bytes: The input key material. This is the same as + ``key_material`` in :meth:`derive`. + :param expected_key bytes: The expected result of deriving a new key, + this is the same as the return value of + :meth:`derive`. + :raises cryptography.exceptions.InvalidKey: This is raised when the + derived key does not match + the expected key. + :raises cryptography.exceptions.AlreadyFinalized: This is raised when + :meth:`derive` or + :meth:`verify` is + called more than + once. + :raises TypeError: This is raised if the provided ``key_material`` is + a unicode object + + This checks whether deriving a new key from the supplied + ``key_material`` generates the same key as the ``expected_key``, and + raises an exception if they do not match. + .. _`NIST SP 800-132`: http://csrc.nist.gov/publications/nistpubs/800-132/nist-sp800-132.pdf .. _`Password Storage Cheat Sheet`: https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet .. _`PBKDF2`: https://en.wikipedia.org/wiki/PBKDF2 diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst index 78bf6637..e5d8c65b 100644 --- a/docs/hazmat/primitives/symmetric-encryption.rst +++ b/docs/hazmat/primitives/symmetric-encryption.rst @@ -20,7 +20,7 @@ provides secrecy but not authenticity. That means an attacker can't see the message but an attacker can create bogus messages and force the application to decrypt them. -For this reason it is *strongly* recommended to combine encryption with a +For this reason it is **strongly** recommended to combine encryption with a message authentication code, such as :doc:`HMAC </hazmat/primitives/mac/hmac>`, in an "encrypt-then-MAC" formulation as `described by Colin Percival`_. |