microblog.pub/utils/linked_data_sig.py

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