Extract secret-handshake into separate lib

requirements.txt

@@ -1,3 +1,4 @@
 pynacl
 simplejson
 pytest
+secret-handshake

ssb/boxstream.py

@@ -1,77 +0,0 @@
-import struct
-from nacl.secret import SecretBox
-
-from .util import bytes_to_long, long_to_bytes
-
-NONCE_SIZE = 24
-HEADER_LENGTH = 2 + 16 + 16
-MAX_SEGMENT_SIZE = 4 * 1024
-TERMINATION_HEADER = (b'\x00' * HEADER_LENGTH)
-MAX_NONCE = (8 * NONCE_SIZE)
-
-
-def inc_nonce(nonce):
-    num = bytes_to_long(nonce) + 1
-    if num > 2**MAX_NONCE:
-        num = 0
-    bnum = long_to_bytes(num)
-    bnum = b'\x00' * (NONCE_SIZE - len(bnum)) + bnum
-    return bnum
-
-
-def get_stream_pair(reader, writer, **kwargs):
-    shared_secret = kwargs.pop('shared_secret')
-    return UnboxStream(reader, shared_secret, **kwargs), BoxStream(writer, shared_secret, **kwargs)
-
-
-class UnboxStream(object):
-    def __init__(self, reader, shared_secret, **key_data):
-        self.reader = reader
-        self.decrypt_key = key_data.get('decrypt_key')
-        self.decrypt_nonce = key_data.get('decrypt_nonce')
-
-    async def process(self):
-        while True:
-            data = await self.reader.read(HEADER_LENGTH)
-            if not data:
-                break
-
-            box = SecretBox(self.decrypt_key)
-            header = box.decrypt(data, self.decrypt_nonce)
-
-            if header == TERMINATION_HEADER:
-                return
-
-            length = struct.unpack('>H', header[:2])[0]
-            mac = header[2:]
-
-            data = await self.reader.read(length)
-
-            self.decrypt_nonce = inc_nonce(self.decrypt_nonce)
-            body = box.decrypt(mac + data, self.decrypt_nonce)
-
-            self.decrypt_nonce = inc_nonce(self.decrypt_nonce)
-            yield body
-        print('Disconnect')
-
-
-class BoxStream(object):
-    def __init__(self, writer, shared_secret, **key_data):
-        self.writer = writer
-        self.encrypt_key = key_data.get('decrypt_key')
-        self.encrypt_nonce = key_data.get('decrypt_nonce')
-
-    async def write(self, data):
-        box = SecretBox(self.encrypt_key)
-
-        # XXX: This nonce logic is almost for sure wrong
-
-        self.encrypt_nonce = inc_nonce(self.encrypt_nonce)
-
-        body = box.encrypt(data, self.encrypt_nonce)
-        header = struct.pack('>H', len(body)) + body[:16]
-
-        self.writer.write(box.encrypt(header, self.encrypt_nonce))
-
-        self.encrypt_nonce = inc_nonce(self.encrypt_nonce)
-        self.writer.write(body)

ssb/packet_stream.py

@@ -1,7 +1,7 @@
 import struct
 from enum import Enum
 
-from .shs.socket import SHSClient, SHSServer
+from secret_handshake import SHSClient, SHSServer
 
 import simplejson
 
@@ -33,17 +33,25 @@ class PSMessage(object):
 
 class PSSocket(object):
     async def read(self):
-        while True:
         try:
-                header = await self.connection.read().__anext__()
+            header = await self.connection.read()
-                body = await self.connection.read().__anext__()
+            if not header:
+                return
+            body = await self.connection.read()
             flags, length, req = struct.unpack('>BIi', header)
-                yield PSMessage(bool(flags & 0x08), bool(flags & 0x04), flags & 0x03, body)
+            return PSMessage(bool(flags & 0x08), bool(flags & 0x04), flags & 0x03, body)
         except StopAsyncIteration:
             await self.connection.disconnect()
-                break
+            return None
 
-    async def write(self, type_, data, req=0):
+    async def __aiter__(self):
+        while True:
+            data = await self.read()
+            if data is None:
+                return
+            yield data
+
+    def write(self, type_, data, req=0):
         type_ = PSMessageType[type_]
         if type_ == PSMessageType.JSON:
             data = simplejson.dumps(data)
@@ -51,27 +59,29 @@ class PSSocket(object):
         # XXX: Not yet handling flags that nicely
 
         header = struct.pack('>BIi', 0x08 | type_.value, len(data), req)
-        await self.connection.write(header)
+        self.connection.write(header)
-        await self.connection.write(data.encode('utf-8'))
+        self.connection.write(data.encode('utf-8'))
 
 
 class PSClient(PSSocket):
-    def __init__(self, host, port, client_kp, server_pub_key, ephemeral_key=None, application_key=None):
+    def __init__(self, host, port, client_kp, server_pub_key, ephemeral_key=None, application_key=None, loop=None):
         self.connection = SHSClient(host, port, client_kp, server_pub_key, ephemeral_key=ephemeral_key,
-                                    application_key=application_key)
+                                    application_key=application_key, loop=loop)
+        self.loop = loop
 
-    async def connect(self, loop=None):
+    def connect(self):
-        await self.connection.connect(loop=loop)
+        self.connection.connect()
 
 
 class PSServer(PSSocket):
-    def __init__(self, host, port, client_kp, application_key=None):
+    def __init__(self, host, port, client_kp, application_key=None, loop=None):
-        self.connection = SHSServer(host, port, client_kp, application_key=application_key)
+        self.connection = SHSServer(host, port, client_kp, application_key=application_key, loop=loop)
+        self.loop = loop
 
-    async def listen(self, loop=None):
+    def listen(self):
-        await self.connection.listen(loop=loop)
+        self.connection.listen()
 
-    def on_connect(self, handler):
+    def on_connect(self, cb):
         async def _on_connect():
-            await handler(self)
+            await cb(self)
-        self.connection._on_connect = _on_connect
+        self.connection.on_connect(_on_connect)

ssb/shs/__init__.py

@@ -1,4 +0,0 @@
-from .crypto import SHSClientCrypto, SHSServerCrypto
-from .socket import SHSClient, SHSServer
-
-__all__ = ('SHSClient', 'SHSClientCrypto', 'SHSServer', 'SHSServerCrypto')

ssb/shs/crypto.py

@@ -1,160 +0,0 @@
-import hashlib
-import hmac
-from base64 import b64decode
-
-from nacl.bindings import crypto_scalarmult, crypto_box_afternm, crypto_box_open_afternm
-from nacl.exceptions import CryptoError
-from nacl.public import PrivateKey
-from nacl.signing import VerifyKey
-
-APPLICATION_KEY = b64decode('1KHLiKZvAvjbY1ziZEHMXawbCEIM6qwjCDm3VYRan/s=')
-
-
-class SHSError(Exception):
-    """A SHS exception."""
-    pass
-
-
-class SHSCryptoBase(object):
-    def __init__(self, local_key, ephemeral_key=None, application_key=None):
-        self.local_key = local_key
-        self.application_key = application_key or APPLICATION_KEY
-        self._reset_keys(ephemeral_key or PrivateKey.generate())
-
-    def _reset_keys(self, ephemeral_key):
-        self.local_ephemeral_key = ephemeral_key
-        self.local_app_hmac = (hmac.new(self.application_key, bytes(ephemeral_key.public_key), digestmod='sha512')
-                               .digest()[:32])
-
-    def generate_challenge(self):
-        """Generate and return a challenge to be sent to the server."""
-        return self.local_app_hmac + bytes(self.local_ephemeral_key.public_key)
-
-    def verify_challenge(self, data):
-        """Verify the correctness of challenge sent from the client."""
-        assert len(data) == 64
-        sent_hmac, remote_ephemeral_key = data[:32], data[32:]
-
-        h = hmac.new(self.application_key, remote_ephemeral_key, digestmod='sha512')
-        self.remote_app_hmac = h.digest()[:32]
-        ok = self.remote_app_hmac == sent_hmac
-
-        if ok:
-            # this is (a * b)
-            self.shared_secret = crypto_scalarmult(bytes(self.local_ephemeral_key), remote_ephemeral_key)
-            self.remote_ephemeral_key = remote_ephemeral_key
-            # this is hash(a * b)
-            self.shared_hash = hashlib.sha256(self.shared_secret).digest()
-        return ok
-
-    def clean(self, new_ephemeral_key=None):
-        self._reset_keys(new_ephemeral_key or PrivateKey.generate())
-        self.shared_secret = None
-        self.shared_hash = None
-        self.remote_ephemeral_key = None
-
-    def get_box_keys(self):
-        shared_secret = hashlib.sha256(self.box_secret).digest()
-        return {
-            'shared_secret': shared_secret,
-            'encrypt_key': hashlib.sha256(shared_secret + bytes(self.remote_pub_key)).digest(),
-            'decrypt_key': hashlib.sha256(shared_secret + bytes(self.local_key.verify_key)).digest(),
-            'encrypt_nonce': self.remote_app_hmac[:24],
-            'decrypt_nonce': self.local_app_hmac[:24]
-        }
-
-
-class SHSServerCrypto(SHSCryptoBase):
-    def verify_client_auth(self, data):
-        assert len(data) == 112
-        a_bob = crypto_scalarmult(bytes(self.local_key.to_curve25519_private_key()), self.remote_ephemeral_key)
-        box_secret = hashlib.sha256(self.application_key + self.shared_secret + a_bob).digest()
-        self.hello = crypto_box_open_afternm(data, b'\x00' * 24, box_secret)
-        signature, public_key = self.hello[:64], self.hello[64:]
-        signed = self.application_key + bytes(self.local_key.verify_key) + self.shared_hash
-        pkey = VerifyKey(public_key)
-
-        # will raise an exception if verification fails
-        pkey.verify(signed, signature)
-        self.remote_pub_key = pkey
-        b_alice = crypto_scalarmult(bytes(self.local_ephemeral_key),
-                                    bytes(self.remote_pub_key.to_curve25519_public_key()))
-        self.box_secret = hashlib.sha256(self.application_key + self.shared_secret + a_bob + b_alice).digest()[:32]
-        return True
-
-    def generate_accept(self):
-        okay = self.local_key.sign(self.application_key + self.hello + self.shared_hash).signature
-        d = crypto_box_afternm(okay, b'\x00' * 24, self.box_secret)
-        return d
-
-    def clean(self, new_ephemeral_key=None):
-        super(SHSServerCrypto, self).clean(new_ephemeral_key=new_ephemeral_key)
-        self.hello = None
-        self.local_lterm_shared = None
-
-
-class SHSClientCrypto(SHSCryptoBase):
-    """An object that encapsulates all the SHS client-side crypto.
-
-    :param local_key: the :class:`ssb.keys.KeyPair` used by the client
-    :param local_ephemeral_key: a fresh local :class:`nacl.public.PrivateKey`
-    :param server_pub_key: the server's public key (``byte`` string)
-    :param application_key: the unique application key (``byte`` string), defaults to SSB's
-    """
-
-    def __init__(self, local_key, server_pub_key, ephemeral_key, application_key=None):
-        super(SHSClientCrypto, self).__init__(local_key, ephemeral_key, application_key)
-        self.remote_pub_key = VerifyKey(server_pub_key)
-
-    def verify_server_challenge(self, data):
-        """Verify the correctness of challenge sent from the server."""
-        # TODO: use super.verify_challenge and add extra logic
-        return super(SHSClientCrypto, self).verify_challenge(data)
-
-    def generate_client_auth(self):
-        """Generate box[K|a*b|a*B](H)"""
-        curve_pkey = self.remote_pub_key.to_curve25519_public_key()
-
-        # remote_lterm_shared is (a * B)
-        remote_lterm_shared = crypto_scalarmult(bytes(self.local_ephemeral_key), bytes(curve_pkey))
-        self.remote_lterm_shared = remote_lterm_shared
-
-        # this shall be hash(K | a * b | a * B)
-        box_secret = hashlib.sha256(self.application_key + self.shared_secret + remote_lterm_shared).digest()
-
-        # and message_to_box will correspond to H = sign(A)[K | Bp | hash(a * b)] | Ap
-        signed_message = self.local_key.sign(self.application_key + bytes(self.remote_pub_key) + self.shared_hash)
-        message_to_box = signed_message.signature + bytes(self.local_key.verify_key)
-        self.client_auth = message_to_box
-
-        nonce = b"\x00" * 24
-        # return box(K | a * b | a * B)[H]
-        return crypto_box_afternm(message_to_box, nonce, box_secret)
-
-    def verify_server_accept(self, data):
-        """Verify that the server's accept message is sane"""
-        curve_lkey = self.local_key.to_curve25519_private_key()
-        # local_lterm_shared is (A * b)
-        local_lterm_shared = crypto_scalarmult(bytes(curve_lkey), self.remote_ephemeral_key)
-        self.local_lterm_shared = local_lterm_shared
-        # this is hash(K | a * b | a * B | A * b)
-        self.box_secret = hashlib.sha256(self.application_key + self.shared_secret + self.remote_lterm_shared +
-                                         local_lterm_shared).digest()
-
-        nonce = b"\x00" * 24
-
-        try:
-            # let's use the box secret to unbox our encrypted message
-            signature = crypto_box_open_afternm(data, nonce, self.box_secret)
-        except CryptoError:
-            raise SHSError('Error decrypting server acceptance message')
-
-        # we should have received sign(B)[K | H | hash(a * b)]
-        # let's see if that signature can verify the reconstructed data on our side
-        self.remote_pub_key.verify(self.application_key + self.client_auth + self.shared_hash, signature)
-        return True
-
-    def clean(self, new_ephemeral_key=None):
-        super(SHSClientCrypto, self).clean(new_ephemeral_key=new_ephemeral_key)
-        self.remote_lterm_shared = None
-        self.local_lterm_shared = None

ssb/shs/socket.py

@@ -1,88 +0,0 @@
-from asyncio import open_connection, start_server
-
-from ..boxstream import get_stream_pair
-from .crypto import SHSClientCrypto, SHSServerCrypto
-
-
-class SHSClientException(Exception):
-    pass
-
-
-class SHSSocket(object):
-    async def read(self):
-        async for msg in self.read_stream.process():
-            yield msg
-
-    async def write(self, data):
-        await self.write_stream.write(data)
-
-    async def disconnect(self):
-        self.writer.close()
-
-
-class SHSServer(SHSSocket):
-    def __init__(self, host, port, server_kp, application_key=None):
-        self.host = host
-        self.port = port
-        self.crypto = SHSServerCrypto(server_kp.private_key, application_key=application_key)
-        self._on_connect = None
-
-    async def _handshake(self, reader, writer):
-        data = await reader.read(64)
-        if not self.crypto.verify_challenge(data):
-            raise SHSClientException('Client challenge is not valid')
-
-        writer.write(self.crypto.generate_challenge())
-
-        data = await reader.read(112)
-        if not self.crypto.verify_client_auth(data):
-            raise SHSClientException('Client auth is not valid')
-
-        writer.write(self.crypto.generate_accept())
-
-    async def handle_connection(self, reader, writer):
-        self.crypto.clean()
-        await self._handshake(reader, writer)
-
-        keys = self.crypto.get_box_keys()
-        self.crypto.clean()
-
-        self.read_stream, self.write_stream = get_stream_pair(reader, writer, **keys)
-        self.writer = writer
-
-        if self._on_connect:
-            await self._on_connect()
-
-    async def listen(self, loop=None):
-        await start_server(self.handle_connection, self.host, self.port, loop=loop)
-
-
-class SHSClient(SHSSocket):
-    def __init__(self, host, port, client_kp, server_pub_key, ephemeral_key=None, application_key=None):
-        self.host = host
-        self.port = port
-        self.crypto = SHSClientCrypto(client_kp.private_key, server_pub_key, ephemeral_key=ephemeral_key,
-                                      application_key=application_key)
-
-    async def _handshake(self, reader, writer):
-        writer.write(self.crypto.generate_challenge())
-
-        data = await reader.read(64)
-        if not self.crypto.verify_server_challenge(data):
-            raise SHSClientException('Server challenge is not valid')
-
-        writer.write(self.crypto.generate_client_auth())
-
-        data = await reader.read(80)
-        if not self.crypto.verify_server_accept(data):
-            raise SHSClientException('Server accept is not valid')
-
-    async def connect(self, loop=None):
-        reader, writer = await open_connection(self.host, self.port, loop=loop)
-        await self._handshake(reader, writer)
-
-        keys = self.crypto.get_box_keys()
-        self.crypto.clean()
-
-        self.read_stream, self.write_stream = get_stream_pair(reader, writer, **keys)
-        self.writer = writer

ssb/tests/test_shs.py

@@ -1,17 +0,0 @@
-import hashlib
-
-import pytest
-from nacl.public import PrivateKey
-
-from ssb.shs import SecretHandShake
-
-
-@pytest.fixture()
-def appkey():
-    return hashlib.sha256(b'app_key').digest()
-
-
-def test_client_challenge(appkey):
-    pk = PrivateKey.generate()
-    shs = SecretHandShake(pk, application_key=appkey)
-    assert shs.client_challenge

test_client.py

@@ -1,19 +1,28 @@
+import os
 from asyncio import get_event_loop
 from base64 import b64decode
 
-from ssb.keys import KeyPair
+import yaml
+from nacl.signing import SigningKey
+
 from ssb.packet_stream import PSClient
 
-server_pub_key = b64decode('--- your public key ---')
+
+with open(os.path.expanduser('~/.ssb/secret')) as f:
+    config = yaml.load(f)
+
+
+server_pub_key = b64decode(config['public'][:-8])
 
 
 async def main(loop):
-    await packet_stream.connect(loop)
+    async for msg in packet_stream:
-    async for msg in packet_stream.read():
         print(msg)
     print('bye')
 
-packet_stream = PSClient('127.0.0.1', 8008, KeyPair(), server_pub_key)
 loop = get_event_loop()
+
+packet_stream = PSClient('127.0.0.1', 8008, SigningKey.generate(), server_pub_key, loop=loop)
+packet_stream.connect()
 loop.run_until_complete(main(loop))
 loop.close()

test_server.py

@@ -1,19 +1,20 @@
+import os
 from asyncio import get_event_loop
 from base64 import b64decode
 
-from ssb.keys import KeyPair
+import yaml
+from nacl.signing import SigningKey
+
 from ssb.packet_stream import PSServer
 
 
-priv_key = b64decode('--- your private key ---')
+with open(os.path.expanduser('~/.ssb/secret')) as f:
-
+    config = yaml.load(f)
-
-async def main(loop):
-    await packet_stream.listen(loop)
 
 
 async def on_connect(server):
-    await server.write('JSON', {"name": ["createHistoryStream"],
+    server.write('JSON', {
+        "name": ["createHistoryStream"],
         "args": [{
             "id": "@/Odg52x38pt7OivNnxK1Lm+H/+x6yV4DhMeXHBQRYc0=.ed25519",
             "seq": 9,
@@ -21,11 +22,15 @@ async def on_connect(server):
             "keys": False
         }],
         "type": "source"}, req=1)
-    print(await server.read().__anext__())
+    print(await server.read())
+    server.write('JSON', {})
 
-packet_stream = PSServer('127.0.0.1', 8008, KeyPair(priv_key[:32]))
-packet_stream.on_connect(on_connect)
 loop = get_event_loop()
-loop.run_until_complete(main(loop))
+
+server_keypair = SigningKey(b64decode(config['private'][:-8])[:32])
+packet_stream = PSServer('127.0.0.1', 8008, server_keypair, loop=loop)
+packet_stream.on_connect(on_connect)
+packet_stream.listen()
+
 loop.run_forever()
 loop.close()