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Diffstat (limited to 'frozen_deps/Cryptodome/Signature/eddsa.py')
| -rw-r--r-- | frozen_deps/Cryptodome/Signature/eddsa.py | 341 |
1 files changed, 341 insertions, 0 deletions
diff --git a/frozen_deps/Cryptodome/Signature/eddsa.py b/frozen_deps/Cryptodome/Signature/eddsa.py new file mode 100644 index 0000000..e80a866 --- /dev/null +++ b/frozen_deps/Cryptodome/Signature/eddsa.py @@ -0,0 +1,341 @@ +# =================================================================== +# +# Copyright (c) 2022, 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. +# =================================================================== + +from Cryptodome.Math.Numbers import Integer + +from Cryptodome.Hash import SHA512, SHAKE256 +from Cryptodome.Util.py3compat import bchr, is_bytes +from Cryptodome.PublicKey.ECC import (EccKey, + construct, + _import_ed25519_public_key, + _import_ed448_public_key) + + +def import_public_key(encoded): + """Import an EdDSA ECC public key, when encoded as raw ``bytes`` as described + in RFC8032. + + Args: + encoded (bytes): + The EdDSA public key to import. + It must be 32 bytes for Ed25519, and 57 bytes for Ed448. + + Returns: + :class:`Cryptodome.PublicKey.EccKey` : a new ECC key object. + + Raises: + ValueError: when the given key cannot be parsed. + """ + + if len(encoded) == 32: + x, y = _import_ed25519_public_key(encoded) + curve_name = "Ed25519" + elif len(encoded) == 57: + x, y = _import_ed448_public_key(encoded) + curve_name = "Ed448" + else: + raise ValueError("Not an EdDSA key (%d bytes)" % len(encoded)) + return construct(curve=curve_name, point_x=x, point_y=y) + + +def import_private_key(encoded): + """Import an EdDSA ECC private key, when encoded as raw ``bytes`` as described + in RFC8032. + + Args: + encoded (bytes): + The EdDSA private key to import. + It must be 32 bytes for Ed25519, and 57 bytes for Ed448. + + Returns: + :class:`Cryptodome.PublicKey.EccKey` : a new ECC key object. + + Raises: + ValueError: when the given key cannot be parsed. + """ + + if len(encoded) == 32: + curve_name = "ed25519" + elif len(encoded) == 57: + curve_name = "ed448" + else: + raise ValueError("Incorrect length. Only EdDSA private keys are supported.") + + # Note that the private key is truly a sequence of random bytes, + # so we cannot check its correctness in any way. + + return construct(seed=encoded, curve=curve_name) + + +class EdDSASigScheme(object): + """An EdDSA signature object. + Do not instantiate directly. + Use :func:`Cryptodome.Signature.eddsa.new`. + """ + + def __init__(self, key, context): + """Create a new EdDSA object. + + Do not instantiate this object directly, + use `Cryptodome.Signature.DSS.new` instead. + """ + + self._key = key + self._context = context + self._A = key._export_eddsa() + self._order = key._curve.order + + def can_sign(self): + """Return ``True`` if this signature object can be used + for signing messages.""" + + return self._key.has_private() + + def sign(self, msg_or_hash): + """Compute the EdDSA signature of a message. + + Args: + msg_or_hash (bytes or a hash object): + The message to sign (``bytes``, in case of *PureEdDSA*) or + the hash that was carried out over the message (hash object, for *HashEdDSA*). + + The hash object must be :class:`Cryptodome.Hash.SHA512` for Ed25519, + and :class:`Cryptodome.Hash.SHAKE256` object for Ed448. + + :return: The signature as ``bytes``. It is always 64 bytes for Ed25519, and 114 bytes for Ed448. + :raise TypeError: if the EdDSA key has no private half + """ + + if not self._key.has_private(): + raise TypeError("Private key is needed to sign") + + if self._key._curve.name == "ed25519": + ph = isinstance(msg_or_hash, SHA512.SHA512Hash) + if not (ph or is_bytes(msg_or_hash)): + raise TypeError("'msg_or_hash' must be bytes of a SHA-512 hash") + eddsa_sign_method = self._sign_ed25519 + + elif self._key._curve.name == "ed448": + ph = isinstance(msg_or_hash, SHAKE256.SHAKE256_XOF) + if not (ph or is_bytes(msg_or_hash)): + raise TypeError("'msg_or_hash' must be bytes of a SHAKE256 hash") + eddsa_sign_method = self._sign_ed448 + + else: + raise ValueError("Incorrect curve for EdDSA") + + return eddsa_sign_method(msg_or_hash, ph) + + def _sign_ed25519(self, msg_or_hash, ph): + + if self._context or ph: + flag = int(ph) + # dom2(flag, self._context) + dom2 = b'SigEd25519 no Ed25519 collisions' + bchr(flag) + \ + bchr(len(self._context)) + self._context + else: + dom2 = b'' + + PHM = msg_or_hash.digest() if ph else msg_or_hash + + # See RFC 8032, section 5.1.6 + + # Step 2 + r_hash = SHA512.new(dom2 + self._key._prefix + PHM).digest() + r = Integer.from_bytes(r_hash, 'little') % self._order + # Step 3 + R_pk = EccKey(point=r * self._key._curve.G)._export_eddsa() + # Step 4 + k_hash = SHA512.new(dom2 + R_pk + self._A + PHM).digest() + k = Integer.from_bytes(k_hash, 'little') % self._order + # Step 5 + s = (r + k * self._key.d) % self._order + + return R_pk + s.to_bytes(32, 'little') + + def _sign_ed448(self, msg_or_hash, ph): + + flag = int(ph) + # dom4(flag, self._context) + dom4 = b'SigEd448' + bchr(flag) + \ + bchr(len(self._context)) + self._context + + PHM = msg_or_hash.read(64) if ph else msg_or_hash + + # See RFC 8032, section 5.2.6 + + # Step 2 + r_hash = SHAKE256.new(dom4 + self._key._prefix + PHM).read(114) + r = Integer.from_bytes(r_hash, 'little') % self._order + # Step 3 + R_pk = EccKey(point=r * self._key._curve.G)._export_eddsa() + # Step 4 + k_hash = SHAKE256.new(dom4 + R_pk + self._A + PHM).read(114) + k = Integer.from_bytes(k_hash, 'little') % self._order + # Step 5 + s = (r + k * self._key.d) % self._order + + return R_pk + s.to_bytes(57, 'little') + + def verify(self, msg_or_hash, signature): + """Check if an EdDSA signature is authentic. + + Args: + msg_or_hash (bytes or a hash object): + The message to verify (``bytes``, in case of *PureEdDSA*) or + the hash that was carried out over the message (hash object, for *HashEdDSA*). + + The hash object must be :class:`Cryptodome.Hash.SHA512` object for Ed25519, + and :class:`Cryptodome.Hash.SHAKE256` for Ed448. + + signature (``bytes``): + The signature that needs to be validated. + It must be 64 bytes for Ed25519, and 114 bytes for Ed448. + + :raise ValueError: if the signature is not authentic + """ + + if self._key._curve.name == "ed25519": + ph = isinstance(msg_or_hash, SHA512.SHA512Hash) + if not (ph or is_bytes(msg_or_hash)): + raise TypeError("'msg_or_hash' must be bytes of a SHA-512 hash") + eddsa_verify_method = self._verify_ed25519 + + elif self._key._curve.name == "ed448": + ph = isinstance(msg_or_hash, SHAKE256.SHAKE256_XOF) + if not (ph or is_bytes(msg_or_hash)): + raise TypeError("'msg_or_hash' must be bytes of a SHAKE256 hash") + eddsa_verify_method = self._verify_ed448 + + else: + raise ValueError("Incorrect curve for EdDSA") + + return eddsa_verify_method(msg_or_hash, signature, ph) + + def _verify_ed25519(self, msg_or_hash, signature, ph): + + if len(signature) != 64: + raise ValueError("The signature is not authentic (length)") + + if self._context or ph: + flag = int(ph) + dom2 = b'SigEd25519 no Ed25519 collisions' + bchr(flag) + \ + bchr(len(self._context)) + self._context + else: + dom2 = b'' + + PHM = msg_or_hash.digest() if ph else msg_or_hash + + # Section 5.1.7 + + # Step 1 + try: + R = import_public_key(signature[:32]).pointQ + except ValueError: + raise ValueError("The signature is not authentic (R)") + s = Integer.from_bytes(signature[32:], 'little') + if s > self._order: + raise ValueError("The signature is not authentic (S)") + # Step 2 + k_hash = SHA512.new(dom2 + signature[:32] + self._A + PHM).digest() + k = Integer.from_bytes(k_hash, 'little') % self._order + # Step 3 + point1 = s * 8 * self._key._curve.G + # OPTIMIZE: with double-scalar multiplication, with no SCA + # countermeasures because it is public values + point2 = 8 * R + k * 8 * self._key.pointQ + if point1 != point2: + raise ValueError("The signature is not authentic") + + def _verify_ed448(self, msg_or_hash, signature, ph): + + if len(signature) != 114: + raise ValueError("The signature is not authentic (length)") + + flag = int(ph) + # dom4(flag, self._context) + dom4 = b'SigEd448' + bchr(flag) + \ + bchr(len(self._context)) + self._context + + PHM = msg_or_hash.read(64) if ph else msg_or_hash + + # Section 5.2.7 + + # Step 1 + try: + R = import_public_key(signature[:57]).pointQ + except ValueError: + raise ValueError("The signature is not authentic (R)") + s = Integer.from_bytes(signature[57:], 'little') + if s > self._order: + raise ValueError("The signature is not authentic (S)") + # Step 2 + k_hash = SHAKE256.new(dom4 + signature[:57] + self._A + PHM).read(114) + k = Integer.from_bytes(k_hash, 'little') % self._order + # Step 3 + point1 = s * 8 * self._key._curve.G + # OPTIMIZE: with double-scalar multiplication, with no SCA + # countermeasures because it is public values + point2 = 8 * R + k * 8 * self._key.pointQ + if point1 != point2: + raise ValueError("The signature is not authentic") + + +def new(key, mode, context=None): + """Create a signature object :class:`EdDSASigScheme` that + can perform or verify an EdDSA signature. + + Args: + key (:class:`Cryptodome.PublicKey.ECC` object: + The key to use for computing the signature (*private* keys only) + or for verifying one. + The key must be on the curve ``Ed25519`` or ``Ed448``. + + mode (string): + This parameter must be ``'rfc8032'``. + + context (bytes): + Up to 255 bytes of `context <https://datatracker.ietf.org/doc/html/rfc8032#page-41>`_, + which is a constant byte string to segregate different protocols or + different applications of the same key. + """ + + if not isinstance(key, EccKey) or not key._is_eddsa(): + raise ValueError("EdDSA can only be used with EdDSA keys") + + if mode != 'rfc8032': + raise ValueError("Mode must be 'rfc8032'") + + if context is None: + context = b'' + elif len(context) > 255: + raise ValueError("Context for EdDSA must not be longer than 255 bytes") + + return EdDSASigScheme(key, context) |