68 lines
1.8 KiB
Python
68 lines
1.8 KiB
Python
import json
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import nacl.encoding
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import nacl.signing
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import multicodec
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import multiformats
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from nacl.signing import VerifyKey
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from sign import to_jws_payload
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def get_signing_input(payload):
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header = b'{"alg":"EdDSA","crit":["b64"],"b64":false}'
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header_b64 = nacl.encoding.URLSafeBase64Encoder.encode(header)
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signing_input = header_b64 + b"." + payload
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return header_b64, signing_input
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def get_message(vc):
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document = vc.copy()
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proof = document.pop("proof", {})
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jws = proof.pop("jws", None)
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proof['@context'] = 'https://w3id.org/security/v2'
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if not jws:
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return None, False
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return jws+"==", to_jws_payload(document, proof)
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def get_verify_key(vc):
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did = vc["proof"]["verificationMethod"].split("#")[0]
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pub = did.split(":")[-1]
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mc = multiformats.multibase.decode(pub)
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public_key_bytes = multicodec.remove_prefix(mc)
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return VerifyKey(public_key_bytes)
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def jws_split(jws):
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header, sig_b64 = jws.split("..")
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signature = nacl.encoding.URLSafeBase64Encoder.decode(sig_b64.encode())
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return header.encode(), signature
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def verify_vc(credential):
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vc = json.loads(credential)
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header = {"alg": "EdDSA", "crit": ["b64"], "b64": False}
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jws, message = get_message(vc)
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if not message:
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return False
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header_b64, signature = get_signing_input(message)
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header_jws, signature_jws = jws_split(jws)
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if header_jws != header_b64:
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return False
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header_jws_json = json.loads(
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nacl.encoding.URLSafeBase64Encoder.decode(header_jws)
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)
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for k, v in header.items():
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if header_jws_json.get(k) != v:
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return False
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verify_key = get_verify_key(vc)
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data_verified = verify_key.verify(signature_jws+signature)
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return data_verified == signature
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