111 lines
3.7 KiB
Python
111 lines
3.7 KiB
Python
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"""
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Create and verify jws-js format Ed25519 signatures.
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"""
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import json
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from ..util import urlsafe_b64decode, urlsafe_b64encode, native, binary
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__all__ = ['sign', 'verify']
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ed25519ll = None
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ALG = "Ed25519"
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def get_ed25519ll():
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"""Lazy import-and-test of ed25519 module"""
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global ed25519ll
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if not ed25519ll:
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try:
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import ed25519ll # fast (thousands / s)
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except (ImportError, OSError): # pragma nocover
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from . import ed25519py as ed25519ll # pure Python (hundreds / s)
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test()
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return ed25519ll
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def sign(payload, keypair):
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"""Return a JWS-JS format signature given a JSON-serializable payload and
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an Ed25519 keypair."""
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get_ed25519ll()
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#
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header = {
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"alg": ALG,
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"jwk": {
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"kty": ALG, # alg -> kty in jwk-08.
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"vk": native(urlsafe_b64encode(keypair.vk))
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}
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}
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encoded_header = urlsafe_b64encode(binary(json.dumps(header, sort_keys=True)))
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encoded_payload = urlsafe_b64encode(binary(json.dumps(payload, sort_keys=True)))
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secured_input = b".".join((encoded_header, encoded_payload))
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sig_msg = ed25519ll.crypto_sign(secured_input, keypair.sk)
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signature = sig_msg[:ed25519ll.SIGNATUREBYTES]
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encoded_signature = urlsafe_b64encode(signature)
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return {"recipients":
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[{"header": native(encoded_header),
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"signature": native(encoded_signature)}],
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"payload": native(encoded_payload)}
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def assertTrue(condition, message=""):
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if not condition:
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raise ValueError(message)
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def verify(jwsjs):
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"""Return (decoded headers, payload) if all signatures in jwsjs are
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consistent, else raise ValueError.
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Caller must decide whether the keys are actually trusted."""
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get_ed25519ll()
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# XXX forbid duplicate keys in JSON input using object_pairs_hook (2.7+)
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recipients = jwsjs["recipients"]
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encoded_payload = binary(jwsjs["payload"])
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headers = []
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for recipient in recipients:
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assertTrue(len(recipient) == 2, "Unknown recipient key {0}".format(recipient))
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h = binary(recipient["header"])
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s = binary(recipient["signature"])
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header = json.loads(native(urlsafe_b64decode(h)))
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assertTrue(header["alg"] == ALG,
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"Unexpected algorithm {0}".format(header["alg"]))
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if "alg" in header["jwk"] and "kty" not in header["jwk"]:
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header["jwk"]["kty"] = header["jwk"]["alg"] # b/w for JWK < -08
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assertTrue(header["jwk"]["kty"] == ALG, # true for Ed25519
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"Unexpected key type {0}".format(header["jwk"]["kty"]))
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vk = urlsafe_b64decode(binary(header["jwk"]["vk"]))
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secured_input = b".".join((h, encoded_payload))
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sig = urlsafe_b64decode(s)
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sig_msg = sig+secured_input
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verified_input = native(ed25519ll.crypto_sign_open(sig_msg, vk))
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verified_header, verified_payload = verified_input.split('.')
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verified_header = binary(verified_header)
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decoded_header = native(urlsafe_b64decode(verified_header))
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headers.append(json.loads(decoded_header))
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verified_payload = binary(verified_payload)
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# only return header, payload that have passed through the crypto library.
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payload = json.loads(native(urlsafe_b64decode(verified_payload)))
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return headers, payload
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def test():
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kp = ed25519ll.crypto_sign_keypair()
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payload = {'test': 'onstartup'}
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jwsjs = json.loads(json.dumps(sign(payload, kp)))
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verify(jwsjs)
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jwsjs['payload'] += 'x'
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try:
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verify(jwsjs)
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except ValueError:
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pass
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else: # pragma no cover
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raise RuntimeError("No error from bad wheel.signatures payload.")
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