2018-05-18 13:41:41 -05:00
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from pyld import jsonld
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import hashlib
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from datetime import datetime
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from Crypto.Signature import PKCS1_v1_5
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from Crypto.Hash import SHA256
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import base64
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2018-05-30 15:27:07 -05:00
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from typing import Any, Dict
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# cache the downloaded "schemas", otherwise the library is super slow
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# (https://github.com/digitalbazaar/pyld/issues/70)
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_CACHE: Dict[str, Any] = {}
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LOADER = jsonld.requests_document_loader()
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def _caching_document_loader(url: str) -> Any:
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if url in _CACHE:
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return _CACHE[url]
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resp = LOADER(url)
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_CACHE[url] = resp
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return resp
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jsonld.set_document_loader(_caching_document_loader)
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2018-05-18 13:41:41 -05:00
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def options_hash(doc):
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doc = dict(doc['signature'])
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for k in ['type', 'id', 'signatureValue']:
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if k in doc:
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del doc[k]
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doc['@context'] = 'https://w3id.org/identity/v1'
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normalized = jsonld.normalize(doc, {'algorithm': 'URDNA2015', 'format': 'application/nquads'})
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h = hashlib.new('sha256')
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h.update(normalized.encode('utf-8'))
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return h.hexdigest()
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def doc_hash(doc):
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doc = dict(doc)
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if 'signature' in doc:
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del doc['signature']
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normalized = jsonld.normalize(doc, {'algorithm': 'URDNA2015', 'format': 'application/nquads'})
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h = hashlib.new('sha256')
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h.update(normalized.encode('utf-8'))
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return h.hexdigest()
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def verify_signature(doc, pubkey):
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to_be_signed = options_hash(doc) + doc_hash(doc)
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signature = doc['signature']['signatureValue']
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signer = PKCS1_v1_5.new(pubkey)
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digest = SHA256.new()
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digest.update(to_be_signed.encode('utf-8'))
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return signer.verify(digest, base64.b64decode(signature))
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def generate_signature(doc, privkey):
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options = {
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'type': 'RsaSignature2017',
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'creator': doc['actor'] + '#main-key',
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'created': datetime.utcnow().replace(microsecond=0).isoformat() + 'Z',
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}
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doc['signature'] = options
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to_be_signed = options_hash(doc) + doc_hash(doc)
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signer = PKCS1_v1_5.new(privkey)
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digest = SHA256.new()
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digest.update(to_be_signed.encode('utf-8'))
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sig = base64.b64encode(signer.sign(digest))
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options['signatureValue'] = sig.decode('utf-8')
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