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119 lines
3.3 KiB
119 lines
3.3 KiB
"""
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Mastodon instances won't accept requests that are not signed using this scheme.
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"""
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import base64
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import hashlib
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import logging
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from datetime import datetime
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from typing import Any
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from typing import Dict
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from typing import Optional
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from urllib.parse import urlsplit
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from Crypto.Hash import SHA256
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from Crypto.Signature import PKCS1_v1_5
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from key import Key
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logger = logging.getLogger(__name__)
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def build_signing_string(headers, used_headers):
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return '\n'.join(map(lambda x: ': '.join([x.lower(), headers[x]]), used_headers))
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def _build_signed_string(
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signed_headers: str, method: str, path: str, headers: Any, body_digest: str
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) -> str:
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out = []
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for signed_header in signed_headers.split(" "):
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if signed_header == "(request-target)":
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out.append("(request-target): " + method.lower() + " " + path)
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elif signed_header == "digest":
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out.append("digest: " + body_digest)
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else:
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out.append(signed_header + ": " + headers[signed_header])
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return "\n".join(out)
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def _parse_sig_header(val: Optional[str]) -> Optional[Dict[str, str]]:
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if not val:
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return None
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out = {}
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for data in val.split(","):
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k, v = data.split("=", 1)
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out[k] = v[1: len(v) - 1] # noqa: black conflict
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return out
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def _verify_h(signed_string, signature, pubkey):
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signer = PKCS1_v1_5.new(pubkey)
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digest = SHA256.new()
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digest.update(signed_string.encode("utf-8"))
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return signer.verify(digest, signature)
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def verify(hsig, request, actor):
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k = Key(actor["id"])
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k.load_pub(actor["publicKey"]["publicKeyPem"])
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if k.key_id() != hsig["keyId"]:
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return False
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signed_string = _build_signed_string(
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hsig["headers"], request.method, request.path,
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request.headers, _body_digest(request.body)
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)
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return _verify_h(signed_string, base64.b64decode(hsig["signature"]), k.pubkey)
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def _body_digest(body: str) -> str:
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h = hashlib.new("sha256")
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h.update(body) # type: ignore
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return "SHA-256=" + base64.b64encode(h.digest()).decode("utf-8")
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class HTTPSigAuth:
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"""Requests auth plugin for signing requests on the fly."""
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def __init__(self, key, headers) -> None:
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self.key = key
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self.headers = headers
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def sign(self, url, body):
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headers = self.headers.copy()
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spl_url = urlsplit(url)
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bh = hashlib.new("sha256")
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try:
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body = body.encode("utf-8")
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except AttributeError:
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pass
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bh.update(body)
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headers.update({
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'request-target': f'post {spl_url.path}',
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"date": datetime.utcnow().strftime("%a, %d %b %Y %H:%M:%S GMT"),
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'host': spl_url.netloc,
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'digest': "SHA-256=" + base64.b64encode(bh.digest()).decode("utf-8")
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})
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sigheaders = headers.keys()
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sigstring = build_signing_string(headers, sigheaders)
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signer = PKCS1_v1_5.new(self.key.privkey)
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digest = SHA256.new()
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digest.update(sigstring.encode("ascii"))
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sigdata = base64.b64encode(signer.sign(digest))
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sig = {
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'keyId': self.key.key_id(),
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'algorithm': 'rsa-sha256',
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'headers': ' '.join(sigheaders),
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'signature': sigdata.decode('ascii')
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}
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headers["signature"] = ','.join(['{}="{}"'.format(k, v) for k, v in sig.items()])
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return headers
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