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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import annotations
import threading
import typing
from cryptography.exceptions import (
InvalidSignature,
UnsupportedAlgorithm,
_Reasons,
)
from cryptography.hazmat.backends.openssl.utils import (
_calculate_digest_and_algorithm,
)
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import utils as asym_utils
from cryptography.hazmat.primitives.asymmetric.padding import (
MGF1,
OAEP,
PSS,
AsymmetricPadding,
PKCS1v15,
_Auto,
_DigestLength,
_MaxLength,
calculate_max_pss_salt_length,
)
from cryptography.hazmat.primitives.asymmetric.rsa import (
RSAPrivateKey,
RSAPrivateNumbers,
RSAPublicKey,
RSAPublicNumbers,
)
if typing.TYPE_CHECKING:
from cryptography.hazmat.backends.openssl.backend import Backend
def _get_rsa_pss_salt_length(
backend: Backend,
pss: PSS,
key: typing.Union[RSAPrivateKey, RSAPublicKey],
hash_algorithm: hashes.HashAlgorithm,
) -> int:
salt = pss._salt_length
if isinstance(salt, _MaxLength):
return calculate_max_pss_salt_length(key, hash_algorithm)
elif isinstance(salt, _DigestLength):
return hash_algorithm.digest_size
elif isinstance(salt, _Auto):
if isinstance(key, RSAPrivateKey):
raise ValueError(
"PSS salt length can only be set to AUTO when verifying"
)
return backend._lib.RSA_PSS_SALTLEN_AUTO
else:
return salt
def _enc_dec_rsa(
backend: Backend,
key: typing.Union[_RSAPrivateKey, _RSAPublicKey],
data: bytes,
padding: AsymmetricPadding,
) -> bytes:
if not isinstance(padding, AsymmetricPadding):
raise TypeError("Padding must be an instance of AsymmetricPadding.")
if isinstance(padding, PKCS1v15):
padding_enum = backend._lib.RSA_PKCS1_PADDING
elif isinstance(padding, OAEP):
padding_enum = backend._lib.RSA_PKCS1_OAEP_PADDING
if not isinstance(padding._mgf, MGF1):
raise UnsupportedAlgorithm(
"Only MGF1 is supported by this backend.",
_Reasons.UNSUPPORTED_MGF,
)
if not backend.rsa_padding_supported(padding):
raise UnsupportedAlgorithm(
"This combination of padding and hash algorithm is not "
"supported by this backend.",
_Reasons.UNSUPPORTED_PADDING,
)
else:
raise UnsupportedAlgorithm(
f"{padding.name} is not supported by this backend.",
_Reasons.UNSUPPORTED_PADDING,
)
return _enc_dec_rsa_pkey_ctx(backend, key, data, padding_enum, padding)
def _enc_dec_rsa_pkey_ctx(
backend: Backend,
key: typing.Union[_RSAPrivateKey, _RSAPublicKey],
data: bytes,
padding_enum: int,
padding: AsymmetricPadding,
) -> bytes:
init: typing.Callable[[typing.Any], int]
crypt: typing.Callable[[typing.Any, typing.Any, int, bytes, int], int]
if isinstance(key, _RSAPublicKey):
init = backend._lib.EVP_PKEY_encrypt_init
crypt = backend._lib.EVP_PKEY_encrypt
else:
init = backend._lib.EVP_PKEY_decrypt_init
crypt = backend._lib.EVP_PKEY_decrypt
pkey_ctx = backend._lib.EVP_PKEY_CTX_new(key._evp_pkey, backend._ffi.NULL)
backend.openssl_assert(pkey_ctx != backend._ffi.NULL)
pkey_ctx = backend._ffi.gc(pkey_ctx, backend._lib.EVP_PKEY_CTX_free)
res = init(pkey_ctx)
backend.openssl_assert(res == 1)
res = backend._lib.EVP_PKEY_CTX_set_rsa_padding(pkey_ctx, padding_enum)
backend.openssl_assert(res > 0)
buf_size = backend._lib.EVP_PKEY_size(key._evp_pkey)
backend.openssl_assert(buf_size > 0)
if isinstance(padding, OAEP):
mgf1_md = backend._evp_md_non_null_from_algorithm(
padding._mgf._algorithm
)
res = backend._lib.EVP_PKEY_CTX_set_rsa_mgf1_md(pkey_ctx, mgf1_md)
backend.openssl_assert(res > 0)
oaep_md = backend._evp_md_non_null_from_algorithm(padding._algorithm)
res = backend._lib.EVP_PKEY_CTX_set_rsa_oaep_md(pkey_ctx, oaep_md)
backend.openssl_assert(res > 0)
if (
isinstance(padding, OAEP)
and padding._label is not None
and len(padding._label) > 0
):
# set0_rsa_oaep_label takes ownership of the char * so we need to
# copy it into some new memory
labelptr = backend._lib.OPENSSL_malloc(len(padding._label))
backend.openssl_assert(labelptr != backend._ffi.NULL)
backend._ffi.memmove(labelptr, padding._label, len(padding._label))
res = backend._lib.EVP_PKEY_CTX_set0_rsa_oaep_label(
pkey_ctx, labelptr, len(padding._label)
)
backend.openssl_assert(res == 1)
outlen = backend._ffi.new("size_t *", buf_size)
buf = backend._ffi.new("unsigned char[]", buf_size)
# Everything from this line onwards is written with the goal of being as
# constant-time as is practical given the constraints of Python and our
# API. See Bleichenbacher's '98 attack on RSA, and its many many variants.
# As such, you should not attempt to change this (particularly to "clean it
# up") without understanding why it was written this way (see
# Chesterton's Fence), and without measuring to verify you have not
# introduced observable time differences.
res = crypt(pkey_ctx, buf, outlen, data, len(data))
resbuf = backend._ffi.buffer(buf)[: outlen[0]]
backend._lib.ERR_clear_error()
if res <= 0:
raise ValueError("Encryption/decryption failed.")
return resbuf
def _rsa_sig_determine_padding(
backend: Backend,
key: typing.Union[_RSAPrivateKey, _RSAPublicKey],
padding: AsymmetricPadding,
algorithm: typing.Optional[hashes.HashAlgorithm],
) -> int:
if not isinstance(padding, AsymmetricPadding):
raise TypeError("Expected provider of AsymmetricPadding.")
pkey_size = backend._lib.EVP_PKEY_size(key._evp_pkey)
backend.openssl_assert(pkey_size > 0)
if isinstance(padding, PKCS1v15):
# Hash algorithm is ignored for PKCS1v15-padding, may be None.
padding_enum = backend._lib.RSA_PKCS1_PADDING
elif isinstance(padding, PSS):
if not isinstance(padding._mgf, MGF1):
raise UnsupportedAlgorithm(
"Only MGF1 is supported by this backend.",
_Reasons.UNSUPPORTED_MGF,
)
# PSS padding requires a hash algorithm
if not isinstance(algorithm, hashes.HashAlgorithm):
raise TypeError("Expected instance of hashes.HashAlgorithm.")
# Size of key in bytes - 2 is the maximum
# PSS signature length (salt length is checked later)
if pkey_size - algorithm.digest_size - 2 < 0:
raise ValueError(
"Digest too large for key size. Use a larger "
"key or different digest."
)
padding_enum = backend._lib.RSA_PKCS1_PSS_PADDING
else:
raise UnsupportedAlgorithm(
f"{padding.name} is not supported by this backend.",
_Reasons.UNSUPPORTED_PADDING,
)
return padding_enum
# Hash algorithm can be absent (None) to initialize the context without setting
# any message digest algorithm. This is currently only valid for the PKCS1v15
# padding type, where it means that the signature data is encoded/decoded
# as provided, without being wrapped in a DigestInfo structure.
def _rsa_sig_setup(
backend: Backend,
padding: AsymmetricPadding,
algorithm: typing.Optional[hashes.HashAlgorithm],
key: typing.Union[_RSAPublicKey, _RSAPrivateKey],
init_func: typing.Callable[[typing.Any], int],
):
padding_enum = _rsa_sig_determine_padding(backend, key, padding, algorithm)
pkey_ctx = backend._lib.EVP_PKEY_CTX_new(key._evp_pkey, backend._ffi.NULL)
backend.openssl_assert(pkey_ctx != backend._ffi.NULL)
pkey_ctx = backend._ffi.gc(pkey_ctx, backend._lib.EVP_PKEY_CTX_free)
res = init_func(pkey_ctx)
if res != 1:
errors = backend._consume_errors()
raise ValueError("Unable to sign/verify with this key", errors)
if algorithm is not None:
evp_md = backend._evp_md_non_null_from_algorithm(algorithm)
res = backend._lib.EVP_PKEY_CTX_set_signature_md(pkey_ctx, evp_md)
if res <= 0:
backend._consume_errors()
raise UnsupportedAlgorithm(
"{} is not supported by this backend for RSA signing.".format(
algorithm.name
),
_Reasons.UNSUPPORTED_HASH,
)
res = backend._lib.EVP_PKEY_CTX_set_rsa_padding(pkey_ctx, padding_enum)
if res <= 0:
backend._consume_errors()
raise UnsupportedAlgorithm(
"{} is not supported for the RSA signature operation.".format(
padding.name
),
_Reasons.UNSUPPORTED_PADDING,
)
if isinstance(padding, PSS):
assert isinstance(algorithm, hashes.HashAlgorithm)
res = backend._lib.EVP_PKEY_CTX_set_rsa_pss_saltlen(
pkey_ctx,
_get_rsa_pss_salt_length(backend, padding, key, algorithm),
)
backend.openssl_assert(res > 0)
mgf1_md = backend._evp_md_non_null_from_algorithm(
padding._mgf._algorithm
)
res = backend._lib.EVP_PKEY_CTX_set_rsa_mgf1_md(pkey_ctx, mgf1_md)
backend.openssl_assert(res > 0)
return pkey_ctx
def _rsa_sig_sign(
backend: Backend,
padding: AsymmetricPadding,
algorithm: hashes.HashAlgorithm,
private_key: _RSAPrivateKey,
data: bytes,
) -> bytes:
pkey_ctx = _rsa_sig_setup(
backend,
padding,
algorithm,
private_key,
backend._lib.EVP_PKEY_sign_init,
)
buflen = backend._ffi.new("size_t *")
res = backend._lib.EVP_PKEY_sign(
pkey_ctx, backend._ffi.NULL, buflen, data, len(data)
)
backend.openssl_assert(res == 1)
buf = backend._ffi.new("unsigned char[]", buflen[0])
res = backend._lib.EVP_PKEY_sign(pkey_ctx, buf, buflen, data, len(data))
if res != 1:
errors = backend._consume_errors()
raise ValueError(
"Digest or salt length too long for key size. Use a larger key "
"or shorter salt length if you are specifying a PSS salt",
errors,
)
return backend._ffi.buffer(buf)[:]
def _rsa_sig_verify(
backend: Backend,
padding: AsymmetricPadding,
algorithm: hashes.HashAlgorithm,
public_key: _RSAPublicKey,
signature: bytes,
data: bytes,
) -> None:
pkey_ctx = _rsa_sig_setup(
backend,
padding,
algorithm,
public_key,
backend._lib.EVP_PKEY_verify_init,
)
res = backend._lib.EVP_PKEY_verify(
pkey_ctx, signature, len(signature), data, len(data)
)
# The previous call can return negative numbers in the event of an
# error. This is not a signature failure but we need to fail if it
# occurs.
backend.openssl_assert(res >= 0)
if res == 0:
backend._consume_errors()
raise InvalidSignature
def _rsa_sig_recover(
backend: Backend,
padding: AsymmetricPadding,
algorithm: typing.Optional[hashes.HashAlgorithm],
public_key: _RSAPublicKey,
signature: bytes,
) -> bytes:
pkey_ctx = _rsa_sig_setup(
backend,
padding,
algorithm,
public_key,
backend._lib.EVP_PKEY_verify_recover_init,
)
# Attempt to keep the rest of the code in this function as constant/time
# as possible. See the comment in _enc_dec_rsa_pkey_ctx. Note that the
# buflen parameter is used even though its value may be undefined in the
# error case. Due to the tolerant nature of Python slicing this does not
# trigger any exceptions.
maxlen = backend._lib.EVP_PKEY_size(public_key._evp_pkey)
backend.openssl_assert(maxlen > 0)
buf = backend._ffi.new("unsigned char[]", maxlen)
buflen = backend._ffi.new("size_t *", maxlen)
res = backend._lib.EVP_PKEY_verify_recover(
pkey_ctx, buf, buflen, signature, len(signature)
)
resbuf = backend._ffi.buffer(buf)[: buflen[0]]
backend._lib.ERR_clear_error()
# Assume that all parameter errors are handled during the setup phase and
# any error here is due to invalid signature.
if res != 1:
raise InvalidSignature
return resbuf
class _RSAPrivateKey(RSAPrivateKey):
_evp_pkey: object
_rsa_cdata: object
_key_size: int
def __init__(
self,
backend: Backend,
rsa_cdata,
evp_pkey,
*,
unsafe_skip_rsa_key_validation: bool,
):
res: int
# RSA_check_key is slower in OpenSSL 3.0.0 due to improved
# primality checking. In normal use this is unlikely to be a problem
# since users don't load new keys constantly, but for TESTING we've
# added an init arg that allows skipping the checks. You should not
# use this in production code unless you understand the consequences.
if not unsafe_skip_rsa_key_validation:
res = backend._lib.RSA_check_key(rsa_cdata)
if res != 1:
errors = backend._consume_errors()
raise ValueError("Invalid private key", errors)
# 2 is prime and passes an RSA key check, so we also check
# if p and q are odd just to be safe.
p = backend._ffi.new("BIGNUM **")
q = backend._ffi.new("BIGNUM **")
backend._lib.RSA_get0_factors(rsa_cdata, p, q)
backend.openssl_assert(p[0] != backend._ffi.NULL)
backend.openssl_assert(q[0] != backend._ffi.NULL)
p_odd = backend._lib.BN_is_odd(p[0])
q_odd = backend._lib.BN_is_odd(q[0])
if p_odd != 1 or q_odd != 1:
errors = backend._consume_errors()
raise ValueError("Invalid private key", errors)
self._backend = backend
self._rsa_cdata = rsa_cdata
self._evp_pkey = evp_pkey
# Used for lazy blinding
self._blinded = False
self._blinding_lock = threading.Lock()
n = self._backend._ffi.new("BIGNUM **")
self._backend._lib.RSA_get0_key(
self._rsa_cdata,
n,
self._backend._ffi.NULL,
self._backend._ffi.NULL,
)
self._backend.openssl_assert(n[0] != self._backend._ffi.NULL)
self._key_size = self._backend._lib.BN_num_bits(n[0])
def _enable_blinding(self) -> None:
# If you call blind on an already blinded RSA key OpenSSL will turn
# it off and back on, which is a performance hit we want to avoid.
if not self._blinded:
with self._blinding_lock:
self._non_threadsafe_enable_blinding()
def _non_threadsafe_enable_blinding(self) -> None:
# This is only a separate function to allow for testing to cover both
# branches. It should never be invoked except through _enable_blinding.
# Check if it's not True again in case another thread raced past the
# first non-locked check.
if not self._blinded:
res = self._backend._lib.RSA_blinding_on(
self._rsa_cdata, self._backend._ffi.NULL
)
self._backend.openssl_assert(res == 1)
self._blinded = True
@property
def key_size(self) -> int:
return self._key_size
def decrypt(self, ciphertext: bytes, padding: AsymmetricPadding) -> bytes:
self._enable_blinding()
key_size_bytes = (self.key_size + 7) // 8
if key_size_bytes != len(ciphertext):
raise ValueError("Ciphertext length must be equal to key size.")
return _enc_dec_rsa(self._backend, self, ciphertext, padding)
def public_key(self) -> RSAPublicKey:
ctx = self._backend._lib.RSAPublicKey_dup(self._rsa_cdata)
self._backend.openssl_assert(ctx != self._backend._ffi.NULL)
ctx = self._backend._ffi.gc(ctx, self._backend._lib.RSA_free)
evp_pkey = self._backend._rsa_cdata_to_evp_pkey(ctx)
return _RSAPublicKey(self._backend, ctx, evp_pkey)
def private_numbers(self) -> RSAPrivateNumbers:
n = self._backend._ffi.new("BIGNUM **")
e = self._backend._ffi.new("BIGNUM **")
d = self._backend._ffi.new("BIGNUM **")
p = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
dmp1 = self._backend._ffi.new("BIGNUM **")
dmq1 = self._backend._ffi.new("BIGNUM **")
iqmp = self._backend._ffi.new("BIGNUM **")
self._backend._lib.RSA_get0_key(self._rsa_cdata, n, e, d)
self._backend.openssl_assert(n[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(e[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(d[0] != self._backend._ffi.NULL)
self._backend._lib.RSA_get0_factors(self._rsa_cdata, p, q)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(q[0] != self._backend._ffi.NULL)
self._backend._lib.RSA_get0_crt_params(
self._rsa_cdata, dmp1, dmq1, iqmp
)
self._backend.openssl_assert(dmp1[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(dmq1[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(iqmp[0] != self._backend._ffi.NULL)
return RSAPrivateNumbers(
p=self._backend._bn_to_int(p[0]),
q=self._backend._bn_to_int(q[0]),
d=self._backend._bn_to_int(d[0]),
dmp1=self._backend._bn_to_int(dmp1[0]),
dmq1=self._backend._bn_to_int(dmq1[0]),
iqmp=self._backend._bn_to_int(iqmp[0]),
public_numbers=RSAPublicNumbers(
e=self._backend._bn_to_int(e[0]),
n=self._backend._bn_to_int(n[0]),
),
)
def private_bytes(
self,
encoding: serialization.Encoding,
format: serialization.PrivateFormat,
encryption_algorithm: serialization.KeySerializationEncryption,
) -> bytes:
return self._backend._private_key_bytes(
encoding,
format,
encryption_algorithm,
self,
self._evp_pkey,
self._rsa_cdata,
)
def sign(
self,
data: bytes,
padding: AsymmetricPadding,
algorithm: typing.Union[asym_utils.Prehashed, hashes.HashAlgorithm],
) -> bytes:
self._enable_blinding()
data, algorithm = _calculate_digest_and_algorithm(data, algorithm)
return _rsa_sig_sign(self._backend, padding, algorithm, self, data)
class _RSAPublicKey(RSAPublicKey):
_evp_pkey: object
_rsa_cdata: object
_key_size: int
def __init__(self, backend: Backend, rsa_cdata, evp_pkey):
self._backend = backend
self._rsa_cdata = rsa_cdata
self._evp_pkey = evp_pkey
n = self._backend._ffi.new("BIGNUM **")
self._backend._lib.RSA_get0_key(
self._rsa_cdata,
n,
self._backend._ffi.NULL,
self._backend._ffi.NULL,
)
self._backend.openssl_assert(n[0] != self._backend._ffi.NULL)
self._key_size = self._backend._lib.BN_num_bits(n[0])
@property
def key_size(self) -> int:
return self._key_size
def __eq__(self, other: object) -> bool:
if not isinstance(other, _RSAPublicKey):
return NotImplemented
return (
self._backend._lib.EVP_PKEY_cmp(self._evp_pkey, other._evp_pkey)
== 1
)
def encrypt(self, plaintext: bytes, padding: AsymmetricPadding) -> bytes:
return _enc_dec_rsa(self._backend, self, plaintext, padding)
def public_numbers(self) -> RSAPublicNumbers:
n = self._backend._ffi.new("BIGNUM **")
e = self._backend._ffi.new("BIGNUM **")
self._backend._lib.RSA_get0_key(
self._rsa_cdata, n, e, self._backend._ffi.NULL
)
self._backend.openssl_assert(n[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(e[0] != self._backend._ffi.NULL)
return RSAPublicNumbers(
e=self._backend._bn_to_int(e[0]),
n=self._backend._bn_to_int(n[0]),
)
def public_bytes(
self,
encoding: serialization.Encoding,
format: serialization.PublicFormat,
) -> bytes:
return self._backend._public_key_bytes(
encoding, format, self, self._evp_pkey, self._rsa_cdata
)
def verify(
self,
signature: bytes,
data: bytes,
padding: AsymmetricPadding,
algorithm: typing.Union[asym_utils.Prehashed, hashes.HashAlgorithm],
) -> None:
data, algorithm = _calculate_digest_and_algorithm(data, algorithm)
_rsa_sig_verify(
self._backend, padding, algorithm, self, signature, data
)
def recover_data_from_signature(
self,
signature: bytes,
padding: AsymmetricPadding,
algorithm: typing.Optional[hashes.HashAlgorithm],
) -> bytes:
if isinstance(algorithm, asym_utils.Prehashed):
raise TypeError(
"Prehashed is only supported in the sign and verify methods. "
"It cannot be used with recover_data_from_signature."
)
return _rsa_sig_recover(
self._backend, padding, algorithm, self, signature
)
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