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Diffstat (limited to 'frozen_deps/Cryptodome/Signature/DSS.py')
| -rw-r--r-- | frozen_deps/Cryptodome/Signature/DSS.py | 413 |
1 files changed, 413 insertions, 0 deletions
diff --git a/frozen_deps/Cryptodome/Signature/DSS.py b/frozen_deps/Cryptodome/Signature/DSS.py new file mode 100644 index 0000000..3dcbeb4 --- /dev/null +++ b/frozen_deps/Cryptodome/Signature/DSS.py @@ -0,0 +1,413 @@ +# +# Signature/DSS.py : DSS.py +# +# =================================================================== +# +# Copyright (c) 2014, Legrandin <[email protected]> +# All rights reserved. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions +# are met: +# +# 1. Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# 2. Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in +# the documentation and/or other materials provided with the +# distribution. +# +# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +# POSSIBILITY OF SUCH DAMAGE. +# =================================================================== + +__all__ = ['new'] + + +from Cryptodome.Util.asn1 import DerSequence +from Cryptodome.Util.number import long_to_bytes +from Cryptodome.Math.Numbers import Integer + +from Cryptodome.Hash import HMAC +from Cryptodome.PublicKey.ECC import EccKey + + +class DssSigScheme(object): + """A (EC)DSA signature object. + Do not instantiate directly. + Use :func:`Cryptodome.Signature.DSS.new`. + """ + + def __init__(self, key, encoding, order): + """Create a new Digital Signature Standard (DSS) object. + + Do not instantiate this object directly, + use `Cryptodome.Signature.DSS.new` instead. + """ + + self._key = key + self._encoding = encoding + self._order = order + + self._order_bits = self._order.size_in_bits() + self._order_bytes = (self._order_bits - 1) // 8 + 1 + + def can_sign(self): + """Return ``True`` if this signature object can be used + for signing messages.""" + + return self._key.has_private() + + def _compute_nonce(self, msg_hash): + raise NotImplementedError("To be provided by subclasses") + + def _valid_hash(self, msg_hash): + raise NotImplementedError("To be provided by subclasses") + + def sign(self, msg_hash): + """Produce the DSA/ECDSA signature of a message. + + :parameter msg_hash: + The hash that was carried out over the message. + The object belongs to the :mod:`Cryptodome.Hash` package. + + Under mode *'fips-186-3'*, the hash must be a FIPS + approved secure hash (SHA-1 or a member of the SHA-2 family), + of cryptographic strength appropriate for the DSA key. + For instance, a 3072/256 DSA key can only be used + in combination with SHA-512. + :type msg_hash: hash object + + :return: The signature as a *byte string* + :raise ValueError: if the hash algorithm is incompatible to the (EC)DSA key + :raise TypeError: if the (EC)DSA key has no private half + """ + + if not self._valid_hash(msg_hash): + raise ValueError("Hash is not sufficiently strong") + + # Generate the nonce k (critical!) + nonce = self._compute_nonce(msg_hash) + + # Perform signature using the raw API + z = Integer.from_bytes(msg_hash.digest()[:self._order_bytes]) + sig_pair = self._key._sign(z, nonce) + + # Encode the signature into a single byte string + if self._encoding == 'binary': + output = b"".join([long_to_bytes(x, self._order_bytes) + for x in sig_pair]) + else: + # Dss-sig ::= SEQUENCE { + # r INTEGER, + # s INTEGER + # } + # Ecdsa-Sig-Value ::= SEQUENCE { + # r INTEGER, + # s INTEGER + # } + output = DerSequence(sig_pair).encode() + + return output + + def verify(self, msg_hash, signature): + """Check if a certain (EC)DSA signature is authentic. + + :parameter msg_hash: + The hash that was carried out over the message. + This is an object belonging to the :mod:`Cryptodome.Hash` module. + + Under mode *'fips-186-3'*, the hash must be a FIPS + approved secure hash (SHA-1 or a member of the SHA-2 family), + of cryptographic strength appropriate for the DSA key. + For instance, a 3072/256 DSA key can only be used in + combination with SHA-512. + :type msg_hash: hash object + + :parameter signature: + The signature that needs to be validated + :type signature: byte string + + :raise ValueError: if the signature is not authentic + """ + + if not self._valid_hash(msg_hash): + raise ValueError("Hash is not sufficiently strong") + + if self._encoding == 'binary': + if len(signature) != (2 * self._order_bytes): + raise ValueError("The signature is not authentic (length)") + r_prime, s_prime = [Integer.from_bytes(x) + for x in (signature[:self._order_bytes], + signature[self._order_bytes:])] + else: + try: + der_seq = DerSequence().decode(signature, strict=True) + except (ValueError, IndexError): + raise ValueError("The signature is not authentic (DER)") + if len(der_seq) != 2 or not der_seq.hasOnlyInts(): + raise ValueError("The signature is not authentic (DER content)") + r_prime, s_prime = Integer(der_seq[0]), Integer(der_seq[1]) + + if not (0 < r_prime < self._order) or not (0 < s_prime < self._order): + raise ValueError("The signature is not authentic (d)") + + z = Integer.from_bytes(msg_hash.digest()[:self._order_bytes]) + result = self._key._verify(z, (r_prime, s_prime)) + if not result: + raise ValueError("The signature is not authentic") + # Make PyCryptodome code to fail + return False + + +class DeterministicDsaSigScheme(DssSigScheme): + # Also applicable to ECDSA + + def __init__(self, key, encoding, order, private_key): + super(DeterministicDsaSigScheme, self).__init__(key, encoding, order) + self._private_key = private_key + + def _bits2int(self, bstr): + """See 2.3.2 in RFC6979""" + + result = Integer.from_bytes(bstr) + q_len = self._order.size_in_bits() + b_len = len(bstr) * 8 + if b_len > q_len: + # Only keep leftmost q_len bits + result >>= (b_len - q_len) + return result + + def _int2octets(self, int_mod_q): + """See 2.3.3 in RFC6979""" + + assert 0 < int_mod_q < self._order + return long_to_bytes(int_mod_q, self._order_bytes) + + def _bits2octets(self, bstr): + """See 2.3.4 in RFC6979""" + + z1 = self._bits2int(bstr) + if z1 < self._order: + z2 = z1 + else: + z2 = z1 - self._order + return self._int2octets(z2) + + def _compute_nonce(self, mhash): + """Generate k in a deterministic way""" + + # See section 3.2 in RFC6979.txt + # Step a + h1 = mhash.digest() + # Step b + mask_v = b'\x01' * mhash.digest_size + # Step c + nonce_k = b'\x00' * mhash.digest_size + + for int_oct in (b'\x00', b'\x01'): + # Step d/f + nonce_k = HMAC.new(nonce_k, + mask_v + int_oct + + self._int2octets(self._private_key) + + self._bits2octets(h1), mhash).digest() + # Step e/g + mask_v = HMAC.new(nonce_k, mask_v, mhash).digest() + + nonce = -1 + while not (0 < nonce < self._order): + # Step h.C (second part) + if nonce != -1: + nonce_k = HMAC.new(nonce_k, mask_v + b'\x00', + mhash).digest() + mask_v = HMAC.new(nonce_k, mask_v, mhash).digest() + + # Step h.A + mask_t = b"" + + # Step h.B + while len(mask_t) < self._order_bytes: + mask_v = HMAC.new(nonce_k, mask_v, mhash).digest() + mask_t += mask_v + + # Step h.C (first part) + nonce = self._bits2int(mask_t) + return nonce + + def _valid_hash(self, msg_hash): + return True + + +class FipsDsaSigScheme(DssSigScheme): + + #: List of L (bit length of p) and N (bit length of q) combinations + #: that are allowed by FIPS 186-3. The security level is provided in + #: Table 2 of FIPS 800-57 (rev3). + _fips_186_3_L_N = ( + (1024, 160), # 80 bits (SHA-1 or stronger) + (2048, 224), # 112 bits (SHA-224 or stronger) + (2048, 256), # 128 bits (SHA-256 or stronger) + (3072, 256) # 256 bits (SHA-512) + ) + + def __init__(self, key, encoding, order, randfunc): + super(FipsDsaSigScheme, self).__init__(key, encoding, order) + self._randfunc = randfunc + + L = Integer(key.p).size_in_bits() + if (L, self._order_bits) not in self._fips_186_3_L_N: + error = ("L/N (%d, %d) is not compliant to FIPS 186-3" + % (L, self._order_bits)) + raise ValueError(error) + + def _compute_nonce(self, msg_hash): + # hash is not used + return Integer.random_range(min_inclusive=1, + max_exclusive=self._order, + randfunc=self._randfunc) + + def _valid_hash(self, msg_hash): + """Verify that SHA-1, SHA-2 or SHA-3 are used""" + return (msg_hash.oid == "1.3.14.3.2.26" or + msg_hash.oid.startswith("2.16.840.1.101.3.4.2.")) + + +class FipsEcDsaSigScheme(DssSigScheme): + + def __init__(self, key, encoding, order, randfunc): + super(FipsEcDsaSigScheme, self).__init__(key, encoding, order) + self._randfunc = randfunc + + def _compute_nonce(self, msg_hash): + return Integer.random_range(min_inclusive=1, + max_exclusive=self._key._curve.order, + randfunc=self._randfunc) + + def _valid_hash(self, msg_hash): + """Verify that SHA-[23] (256|384|512) bits are used to + match the security of P-256 (128 bits), P-384 (192 bits) + or P-521 (256 bits)""" + + modulus_bits = self._key.pointQ.size_in_bits() + + sha256 = ( "2.16.840.1.101.3.4.2.1", "2.16.840.1.101.3.4.2.8" ) + sha384 = ( "2.16.840.1.101.3.4.2.2", "2.16.840.1.101.3.4.2.9" ) + sha512 = ( "2.16.840.1.101.3.4.2.3", "2.16.840.1.101.3.4.2.10") + + if msg_hash.oid in sha256: + return modulus_bits <= 256 + elif msg_hash.oid in sha384: + return modulus_bits <= 384 + else: + return msg_hash.oid in sha512 + + +def new(key, mode, encoding='binary', randfunc=None): + """Create a signature object :class:`DSS_SigScheme` that + can perform (EC)DSA signature or verification. + + .. note:: + Refer to `NIST SP 800 Part 1 Rev 4`_ (or newer release) for an + overview of the recommended key lengths. + + :parameter key: + The key to use for computing the signature (*private* keys only) + or verifying one: it must be either + :class:`Cryptodome.PublicKey.DSA` or :class:`Cryptodome.PublicKey.ECC`. + + For DSA keys, let ``L`` and ``N`` be the bit lengths of the modulus ``p`` + and of ``q``: the pair ``(L,N)`` must appear in the following list, + in compliance to section 4.2 of `FIPS 186-4`_: + + - (1024, 160) *legacy only; do not create new signatures with this* + - (2048, 224) *deprecated; do not create new signatures with this* + - (2048, 256) + - (3072, 256) + + For ECC, only keys over P-256, P384, and P-521 are accepted. + :type key: + a key object + + :parameter mode: + The parameter can take these values: + + - *'fips-186-3'*. The signature generation is randomized and carried out + according to `FIPS 186-3`_: the nonce ``k`` is taken from the RNG. + - *'deterministic-rfc6979'*. The signature generation is not + randomized. See RFC6979_. + :type mode: + string + + :parameter encoding: + How the signature is encoded. This value determines the output of + :meth:`sign` and the input to :meth:`verify`. + + The following values are accepted: + + - *'binary'* (default), the signature is the raw concatenation + of ``r`` and ``s``. It is defined in the IEEE P.1363 standard. + + For DSA, the size in bytes of the signature is ``N/4`` bytes + (e.g. 64 for ``N=256``). + + For ECDSA, the signature is always twice the length of a point + coordinate (e.g. 64 bytes for P-256). + + - *'der'*, the signature is a ASN.1 DER SEQUENCE + with two INTEGERs (``r`` and ``s``). It is defined in RFC3279_. + The size of the signature is variable. + :type encoding: string + + :parameter randfunc: + A function that returns random *byte strings*, of a given length. + If omitted, the internal RNG is used. + Only applicable for the *'fips-186-3'* mode. + :type randfunc: callable + + .. _FIPS 186-3: http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf + .. _FIPS 186-4: http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf + .. _NIST SP 800 Part 1 Rev 4: http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r4.pdf + .. _RFC6979: http://tools.ietf.org/html/rfc6979 + .. _RFC3279: https://tools.ietf.org/html/rfc3279#section-2.2.2 + """ + + # The goal of the 'mode' parameter is to avoid to + # have the current version of the standard as default. + # + # Over time, such version will be superseded by (for instance) + # FIPS 186-4 and it will be odd to have -3 as default. + + if encoding not in ('binary', 'der'): + raise ValueError("Unknown encoding '%s'" % encoding) + + if isinstance(key, EccKey): + order = key._curve.order + private_key_attr = 'd' + else: + order = Integer(key.q) + private_key_attr = 'x' + + if key.has_private(): + private_key = getattr(key, private_key_attr) + else: + private_key = None + + if mode == 'deterministic-rfc6979': + return DeterministicDsaSigScheme(key, encoding, order, private_key) + elif mode == 'fips-186-3': + if isinstance(key, EccKey): + return FipsEcDsaSigScheme(key, encoding, order, randfunc) + else: + return FipsDsaSigScheme(key, encoding, order, randfunc) + else: + raise ValueError("Unknown DSS mode '%s'" % mode) |