relay/viera/http_signatures.py

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import aiohttp
import aiohttp.web
import base64
import logging
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA, SHA256, SHA512
from Crypto.Signature import PKCS1_v1_5
from .remote_actor import fetch_actor
HASHES = {
'sha1': SHA,
'sha256': SHA256,
'sha512': SHA512
}
def split_signature(sig):
default = {"headers": "date"}
sig = sig.strip().split(',')
for chunk in sig:
k, _, v = chunk.partition('=')
v = v.strip('\"')
default[k] = v
default['headers'] = default['headers'].split()
return default
def build_signing_string(headers, used_headers):
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return '\n'.join(map(lambda x: ': '.join([x.lower(), headers[x]]), used_headers))
def sign_headers(headers, key, key_id):
used_headers = headers.keys()
sig = {
'keyId': key_id,
'algorithm': 'rsa-sha256',
'headers': ' '.join(used_headers)
}
sigstring = build_signing_string(headers, used_headers)
pkcs = PKCS1_v1_5.new(key)
h = SHA256.new()
h.update(sigstring.encode('ascii'))
sigdata = pkcs.sign(h)
sigdata = base64.b64encode(sigdata)
sig['signature'] = sigdata.decode('ascii')
chunks = ['{}="{}"'.format(k, v) for k, v in sig.items()]
return ','.join(chunks)
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async def fetch_actor_key(actor):
actor_data = await fetch_actor(actor)
if 'publicKey' not in actor_data:
return None
if 'publicKeyPem' not in actor_data['publicKey']:
return None
return RSA.importKey(actor_data['publicKey']['publicKeyPem'])
async def validate(actor, request):
pubkey = await fetch_actor_key(actor)
logging.debug('actor key: %r', pubkey)
headers = request.headers.copy()
headers['(request-target)'] = ' '.join([request.method.lower(), request.path])
sig = split_signature(headers['signature'])
logging.debug('sigdata: %r', sig)
sigstring = build_signing_string(headers, sig['headers'])
logging.debug('sigstring: %r', sigstring)
sign_alg, _, hash_alg = sig['algorithm'].partition('-')
logging.debug('sign alg: %r, hash alg: %r', sign_alg, hash_alg)
sigdata = base64.b64decode(sig['signature'])
pkcs = PKCS1_v1_5.new(pubkey)
h = HASHES[hash_alg].new()
h.update(sigstring.encode('ascii'))
result = pkcs.verify(h, sigdata)
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request['validated'] = result
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logging.debug('validates? %r', result)
return result
async def http_signatures_middleware(app, handler):
async def http_signatures_handler(request):
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request['validated'] = False
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if 'signature' in request.headers:
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data = await request.json()
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if 'actor' not in data:
raise aiohttp.web.HTTPUnauthorized(body='signature check failed, no actor in message')
actor = data["actor"]
if not (await validate(actor, request)):
raise aiohttp.web.HTTPUnauthorized(body='signature check failed, signature did not match key')
return (await handler(request))
return (await handler(request))
return http_signatures_handler