192 lines
7.0 KiB
Python
192 lines
7.0 KiB
Python
import os
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import base64
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from . import _ed25519
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BadSignatureError = _ed25519.BadSignatureError
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def create_keypair(entropy=os.urandom):
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SEEDLEN = int(_ed25519.SECRETKEYBYTES/2)
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assert SEEDLEN == 32
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seed = entropy(SEEDLEN)
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sk = SigningKey(seed)
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vk = sk.get_verifying_key()
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return sk, vk
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class BadPrefixError(Exception):
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pass
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def remove_prefix(s_bytes, prefix):
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assert(type(s_bytes) == type(prefix))
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if s_bytes[:len(prefix)] != prefix:
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raise BadPrefixError("did not see expected '%s' prefix" % (prefix,))
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return s_bytes[len(prefix):]
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def to_ascii(s_bytes, prefix="", encoding="base64"):
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"""Return a version-prefixed ASCII representation of the given binary
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string. 'encoding' indicates how to do the encoding, and can be one of:
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* base64
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* base32
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* base16 (or hex)
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This function handles bytes, not bits, so it does not append any trailing
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'=' (unlike standard base64.b64encode). It also lowercases the base32
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output.
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'prefix' will be prepended to the encoded form, and is useful for
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distinguishing the purpose and version of the binary string. E.g. you
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could prepend 'pub0-' to a VerifyingKey string to allow the receiving
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code to raise a useful error if someone pasted in a signature string by
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mistake.
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"""
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assert isinstance(s_bytes, bytes)
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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if encoding == "base64":
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s_ascii = base64.b64encode(s_bytes).decode('ascii').rstrip("=")
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elif encoding == "base32":
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s_ascii = base64.b32encode(s_bytes).decode('ascii').rstrip("=").lower()
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elif encoding in ("base16", "hex"):
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s_ascii = base64.b16encode(s_bytes).decode('ascii').lower()
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else:
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raise NotImplementedError
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return prefix+s_ascii.encode('ascii')
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def from_ascii(s_ascii, prefix="", encoding="base64"):
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"""This is the opposite of to_ascii. It will throw BadPrefixError if
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the prefix is not found.
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"""
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if isinstance(s_ascii, bytes):
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s_ascii = s_ascii.decode('ascii')
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if isinstance(prefix, bytes):
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prefix = prefix.decode('ascii')
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s_ascii = remove_prefix(s_ascii.strip(), prefix)
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if encoding == "base64":
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s_ascii += "=" * ((4 - len(s_ascii) % 4) % 4)
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s_bytes = base64.b64decode(s_ascii.encode('ascii'))
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elif encoding == "base32":
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s_ascii += "=" * ((8 - len(s_ascii) % 8) % 8)
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s_bytes = base64.b32decode(s_ascii.upper().encode('ascii'))
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elif encoding in ("base16", "hex"):
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s_bytes = base64.b16decode(s_ascii.upper().encode('ascii'))
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else:
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raise NotImplementedError
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return s_bytes
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class SigningKey(object):
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# this can only be used to reconstruct a key created by create_keypair().
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def __init__(self, sk_s, prefix="", encoding=None):
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assert isinstance(sk_s, bytes)
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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sk_s = remove_prefix(sk_s, prefix)
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if encoding is not None:
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sk_s = from_ascii(sk_s, encoding=encoding)
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if len(sk_s) == 32:
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# create from seed
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vk_s, sk_s = _ed25519.publickey(sk_s)
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else:
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if len(sk_s) != 32+32:
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raise ValueError("SigningKey takes 32-byte seed or 64-byte string")
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self.sk_s = sk_s # seed+pubkey
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self.vk_s = sk_s[32:] # just pubkey
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def to_bytes(self, prefix=""):
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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return prefix+self.sk_s
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def to_ascii(self, prefix="", encoding=None):
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assert encoding
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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return to_ascii(self.to_seed(), prefix, encoding)
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def to_seed(self, prefix=""):
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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return prefix+self.sk_s[:32]
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def __eq__(self, them):
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if not isinstance(them, object): return False
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return (them.__class__ == self.__class__
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and them.sk_s == self.sk_s)
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def get_verifying_key(self):
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return VerifyingKey(self.vk_s)
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def sign(self, msg, prefix="", encoding=None):
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assert isinstance(msg, bytes)
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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sig_and_msg = _ed25519.sign(msg, self.sk_s)
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# the response is R+S+msg
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sig_R = sig_and_msg[0:32]
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sig_S = sig_and_msg[32:64]
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msg_out = sig_and_msg[64:]
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sig_out = sig_R + sig_S
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assert msg_out == msg
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if encoding:
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return to_ascii(sig_out, prefix, encoding)
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return prefix+sig_out
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class VerifyingKey(object):
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def __init__(self, vk_s, prefix="", encoding=None):
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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if not isinstance(vk_s, bytes):
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vk_s = vk_s.encode('ascii')
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assert isinstance(vk_s, bytes)
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vk_s = remove_prefix(vk_s, prefix)
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if encoding is not None:
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vk_s = from_ascii(vk_s, encoding=encoding)
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assert len(vk_s) == 32
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self.vk_s = vk_s
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def to_bytes(self, prefix=""):
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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return prefix+self.vk_s
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def to_ascii(self, prefix="", encoding=None):
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assert encoding
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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return to_ascii(self.vk_s, prefix, encoding)
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def __eq__(self, them):
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if not isinstance(them, object): return False
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return (them.__class__ == self.__class__
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and them.vk_s == self.vk_s)
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def verify(self, sig, msg, prefix="", encoding=None):
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if not isinstance(sig, bytes):
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sig = sig.encode('ascii')
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if not isinstance(prefix, bytes):
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prefix = prefix.encode('ascii')
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assert isinstance(sig, bytes)
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assert isinstance(msg, bytes)
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if encoding:
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sig = from_ascii(sig, prefix, encoding)
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else:
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sig = remove_prefix(sig, prefix)
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assert len(sig) == 64
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sig_R = sig[:32]
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sig_S = sig[32:]
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sig_and_msg = sig_R + sig_S + msg
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# this might raise BadSignatureError
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msg2 = _ed25519.open(sig_and_msg, self.vk_s)
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assert msg2 == msg
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def selftest():
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message = b"crypto libraries should always test themselves at powerup"
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sk = SigningKey(b"priv0-VIsfn5OFGa09Un2MR6Hm7BQ5++xhcQskU2OGXG8jSJl4cWLZrRrVcSN2gVYMGtZT+3354J5jfmqAcuRSD9KIyg",
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prefix="priv0-", encoding="base64")
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vk = VerifyingKey(b"pub0-eHFi2a0a1XEjdoFWDBrWU/t9+eCeY35qgHLkUg/SiMo",
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prefix="pub0-", encoding="base64")
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assert sk.get_verifying_key() == vk
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sig = sk.sign(message, prefix="sig0-", encoding="base64")
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assert sig == b"sig0-E/QrwtSF52x8+q0l4ahA7eJbRKc777ClKNg217Q0z4fiYMCdmAOI+rTLVkiFhX6k3D+wQQfKdJYMxaTUFfv1DQ", sig
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vk.verify(sig, message, prefix="sig0-", encoding="base64")
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selftest()
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