microblog/app/ldsig.py

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2022-06-27 18:56:13 +00:00
import base64
import hashlib
import typing
from datetime import datetime
from functools import lru_cache
from typing import Any
from Crypto.Hash import SHA256
from Crypto.Signature import PKCS1_v1_5
from pyld import jsonld # type: ignore
if typing.TYPE_CHECKING:
from app.key import Key
_LOADER = jsonld.requests_document_loader()
@lru_cache(256)
def _caching_document_loader(url: str) -> Any:
return _LOADER(url)
jsonld.set_document_loader(_caching_document_loader)
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, key: "Key"):
to_be_signed = _options_hash(doc) + _doc_hash(doc)
signature = doc["signature"]["signatureValue"]
signer = PKCS1_v1_5.new(key.pubkey or key.privkey) # type: ignore
digest = SHA256.new()
digest.update(to_be_signed.encode("utf-8"))
return signer.verify(digest, base64.b64decode(signature)) # type: ignore
def generate_signature(doc, key: "Key"):
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)
if not key.privkey:
raise ValueError(f"missing privkey on key {key!r}")
signer = PKCS1_v1_5.new(key.privkey)
digest = SHA256.new()
digest.update(to_be_signed.encode("utf-8"))
sig = base64.b64encode(signer.sign(digest)) # type: ignore
options["signatureValue"] = sig.decode("utf-8")