149 lines
3.8 KiB
Python
149 lines
3.8 KiB
Python
import aiohttp
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import aiohttp.web
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import base64
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import logging
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from Crypto.PublicKey import RSA
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from Crypto.Hash import SHA, SHA256, SHA512
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from Crypto.Signature import PKCS1_v1_5
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from cachetools import LFUCache
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from async_lru import alru_cache
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from .remote_actor import fetch_actor
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HASHES = {
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'sha1': SHA,
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'sha256': SHA256,
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'sha512': SHA512
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}
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def split_signature(sig):
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default = {"headers": "date"}
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sig = sig.strip().split(',')
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for chunk in sig:
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k, _, v = chunk.partition('=')
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v = v.strip('\"')
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default[k] = v
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default['headers'] = default['headers'].split()
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return default
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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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SIGSTRING_CACHE = LFUCache(1024)
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def sign_signing_string(sigstring, key):
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if sigstring in SIGSTRING_CACHE:
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return SIGSTRING_CACHE[sigstring]
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pkcs = PKCS1_v1_5.new(key)
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h = SHA256.new()
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h.update(sigstring.encode('ascii'))
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sigdata = pkcs.sign(h)
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sigdata = base64.b64encode(sigdata)
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SIGSTRING_CACHE[sigstring] = sigdata.decode('ascii')
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return SIGSTRING_CACHE[sigstring]
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def generate_body_digest(body):
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bodyhash = SIGSTRING_CACHE.get(body)
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if not bodyhash:
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h = SHA256.new(body.encode('utf-8'))
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bodyhash = base64.b64encode(h.digest()).decode('utf-8')
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SIGSTRING_CACHE[body] = bodyhash
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return bodyhash
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def sign_headers(headers, key, key_id):
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headers = {x.lower(): y for x, y in headers.items()}
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used_headers = headers.keys()
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sig = {
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'keyId': key_id,
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'algorithm': 'rsa-sha256',
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'headers': ' '.join(used_headers)
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}
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sigstring = build_signing_string(headers, used_headers)
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sig['signature'] = sign_signing_string(sigstring, key)
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chunks = ['{}="{}"'.format(k, v) for k, v in sig.items()]
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return ','.join(chunks)
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@alru_cache(maxsize=16384)
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async def fetch_actor_key(actor):
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actor_data = await fetch_actor(actor)
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if not actor_data:
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return None
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try:
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return RSA.importKey(actor_data['publicKey']['publicKeyPem'])
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except Exception as e:
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logging.debug(f'Exception occured while fetching actor key: {e}')
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async def validate(actor, request):
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pubkey = await fetch_actor_key(actor)
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if not pubkey:
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return False
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logging.debug('actor key: %r', pubkey)
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headers = request.headers.copy()
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headers['(request-target)'] = ' '.join([request.method.lower(), request.path])
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sig = split_signature(headers['signature'])
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logging.debug('sigdata: %r', sig)
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sigstring = build_signing_string(headers, sig['headers'])
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logging.debug('sigstring: %r', sigstring)
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sign_alg, _, hash_alg = sig['algorithm'].partition('-')
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logging.debug('sign alg: %r, hash alg: %r', sign_alg, hash_alg)
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sigdata = base64.b64decode(sig['signature'])
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pkcs = PKCS1_v1_5.new(pubkey)
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h = HASHES[hash_alg].new()
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h.update(sigstring.encode('ascii'))
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result = pkcs.verify(h, sigdata)
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request['validated'] = result
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logging.debug('validates? %r', result)
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return result
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async def http_signatures_middleware(app, handler):
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async def http_signatures_handler(request):
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request['validated'] = False
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if 'signature' in request.headers and request.method == 'POST':
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data = await request.json()
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if 'actor' not in data:
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raise aiohttp.web.HTTPUnauthorized(body='signature check failed, no actor in message')
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actor = data["actor"]
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if not (await validate(actor, request)):
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logging.info('Signature validation failed for: %r', actor)
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raise aiohttp.web.HTTPUnauthorized(body='signature check failed, signature did not match key')
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return (await handler(request))
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return (await handler(request))
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return http_signatures_handler
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