Merge pull request #176 from cthulahoops/digests

Verify http digest is correct if specified in signature.
This commit is contained in:
Mouse Reeve 2020-05-20 08:17:00 -07:00 committed by GitHub
commit 00bd8928b0
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 91 additions and 25 deletions

View file

@ -5,7 +5,7 @@ import requests
from fedireads import models
from fedireads.tasks import app
from fedireads.signatures import make_signature
from fedireads.signatures import make_signature, make_digest
def get_public_recipients(user, software=None):
@ -67,12 +67,16 @@ def sign_and_send(sender, activity, destination):
# this shouldn't happen. it would be bad if it happened.
raise ValueError('No private key found for sender')
data = json.dumps(activity).encode('utf-8')
digest = make_digest(data)
response = requests.post(
destination,
data=json.dumps(activity),
data=data,
headers={
'Date': now,
'Signature': make_signature(sender, destination, now),
'Digest': digest,
'Signature': make_signature(sender, destination, now, digest),
'Content-Type': 'application/activity+json; charset=utf-8',
},
)

View file

@ -114,6 +114,10 @@ def get_or_create_remote_server(domain):
'https://%s/.well-known/nodeinfo' % domain,
headers={'Accept': 'application/activity+json'}
)
if response.status_code != 200:
return None
data = response.json()
try:
nodeinfo_url = data.get('links')[0].get('href')

View file

@ -1,4 +1,6 @@
import hashlib
from urllib.parse import urlparse
import datetime
from base64 import b64encode, b64decode
from Crypto import Random
@ -6,6 +8,7 @@ from Crypto.PublicKey import RSA
from Crypto.Signature import pkcs1_15 #pylint: disable=no-name-in-module
from Crypto.Hash import SHA256
MAX_SIGNATURE_AGE = 300
def create_key_pair():
random_generator = Random.new().read
@ -16,12 +19,13 @@ def create_key_pair():
return private_key, public_key
def make_signature(sender, destination, date):
def make_signature(sender, destination, date, digest):
inbox_parts = urlparse(destination)
signature_headers = [
'(request-target): post %s' % inbox_parts.path,
'host: %s' % inbox_parts.netloc,
'date: %s' % date,
'digest: %s' % digest,
]
message_to_sign = '\n'.join(signature_headers)
signer = pkcs1_15.new(RSA.import_key(sender.private_key))
@ -29,11 +33,26 @@ def make_signature(sender, destination, date):
signature = {
'keyId': '%s#main-key' % sender.remote_id,
'algorithm': 'rsa-sha256',
'headers': '(request-target) host date',
'headers': '(request-target) host date digest',
'signature': b64encode(signed_message).decode('utf8'),
}
return ','.join('%s="%s"' % (k, v) for (k, v) in signature.items())
def make_digest(data):
return 'SHA-256=' + b64encode(hashlib.sha512(data).digest()).decode('utf-8')
def verify_digest(request):
algorithm, digest = request.headers['digest'].split('=', 1)
if algorithm == 'SHA-256':
hash_function = hashlib.sha256
elif algorithm == 'SHA-512':
hash_function = hashlib.sha512
else:
raise ValueError("Unsupported hash function: {}".format(algorithm))
expected = hash_function(request.body).digest()
if b64decode(digest) != expected:
return ValueError("Invalid HTTP Digest header")
class Signature:
def __init__(self, key_id, headers, signature):
@ -60,6 +79,9 @@ class Signature:
def verify(self, public_key, request):
''' verify rsa signature '''
if http_date_age(request.headers['date']) > MAX_SIGNATURE_AGE:
raise ValueError(
"Request too old: %s" % (request.headers['date'],))
public_key = RSA.import_key(public_key)
comparison_string = []
@ -68,6 +90,8 @@ class Signature:
comparison_string.append(
'(request-target): post %s' % request.path)
else:
if signed_header_name == 'digest':
verify_digest(request)
comparison_string.append('%s: %s' % (
signed_header_name,
request.headers[signed_header_name]
@ -80,3 +104,8 @@ class Signature:
# raises a ValueError if it fails
signer.verify(digest, self.signature)
def http_date_age(datestr):
parsed = datetime.datetime.strptime(datestr, '%a, %d %b %Y %H:%M:%S GMT')
delta = datetime.datetime.utcnow() - parsed
return delta.total_seconds()

View file

@ -1,6 +1,8 @@
import time
from collections import namedtuple
from urllib.parse import urlsplit
import json
import responses
from django.test import TestCase, Client
@ -9,7 +11,10 @@ from django.utils.http import http_date
from fedireads.models import User
from fedireads.activitypub import get_follow_request
from fedireads.settings import DOMAIN
from fedireads.signatures import create_key_pair, make_signature
from fedireads.signatures import create_key_pair, make_signature, make_digest
def get_follow_data(follower, followee):
return json.dumps(get_follow_request(follower, followee)).encode('utf-8')
Sender = namedtuple('Sender', ('remote_id', 'private_key', 'public_key'))
@ -27,35 +32,44 @@ class Signature(TestCase):
public_key,
)
def send_follow(self, sender, signature, now):
def send(self, signature, now, data):
c = Client()
return c.post(
urlsplit(self.rat.inbox).path,
data=get_follow_request(
sender,
self.rat,
),
data=data,
content_type='application/json',
**{
'HTTP_DATE': now,
'HTTP_SIGNATURE': signature,
'HTTP_DIGEST': make_digest(data),
'HTTP_CONTENT_TYPE': 'application/activity+json; charset=utf-8',
'HTTP_HOST': DOMAIN,
}
)
def send_test_request(
self,
sender,
signer=None,
send_data=None,
digest=None,
date=None):
now = date or http_date()
data = get_follow_data(sender, self.rat)
signature = make_signature(
signer or sender, self.rat.inbox, now, digest or make_digest(data))
return self.send(signature, now, send_data or data)
def test_correct_signature(self):
now = http_date()
signature = make_signature(self.mouse, self.rat.inbox, now)
return self.send_follow(self.mouse, signature, now).status_code == 200
response = self.send_test_request(sender=self.mouse)
self.assertEqual(response.status_code, 200)
def test_wrong_signature(self):
''' Messages must be signed by the right actor.
(cat cannot sign messages on behalf of mouse)
'''
now = http_date()
signature = make_signature(self.cat, self.rat.inbox, now)
assert self.send_follow(self.mouse, signature, now).status_code == 401
response = self.send_test_request(sender=self.mouse, signer=self.cat)
self.assertEqual(response.status_code, 401)
@responses.activate
def test_remote_signer(self):
@ -67,10 +81,7 @@ class Signature(TestCase):
}},
status=200)
now = http_date()
sender = self.fake_remote
signature = make_signature(sender, self.rat.inbox, now)
response = self.send_follow(sender, signature, now)
response = self.send_test_request(sender=self.fake_remote)
self.assertEqual(response.status_code, 200)
@responses.activate
@ -81,8 +92,26 @@ class Signature(TestCase):
json={'error': 'not found'},
status=404)
now = http_date()
sender = self.fake_remote
signature = make_signature(sender, self.rat.inbox, now)
response = self.send_follow(sender, signature, now)
response = self.send_test_request(sender=self.fake_remote)
self.assertEqual(response.status_code, 401)
def test_changed_data(self):
'''Message data must match the digest header.'''
response = self.send_test_request(
self.mouse,
send_data=get_follow_data(self.mouse, self.cat))
self.assertEqual(response.status_code, 401)
def test_invalid_digest(self):
response = self.send_test_request(
self.mouse,
digest='SHA-256=AAAAAAAAAAAAAAAAAA')
self.assertEqual(response.status_code, 401)
def test_old_message(self):
'''Old messages should be rejected to prevent replay attacks.'''
response = self.send_test_request(
self.mouse,
date=http_date(time.time() - 301)
)
self.assertEqual(response.status_code, 401)