intial version of guard module; #32

* currently includes totp related functions

docs/api/steam.guard.rst

@@ -0,0 +1,5 @@
+guard
+=====
+
+.. automodule:: steam.guard
+    :members:

docs/api/steam.rst

@@ -6,6 +6,7 @@ steam
     steam.core
     steam.enums
     steam.globalid
+    steam.guard
     steam.steamid
     steam.webapi
     steam.webauth

steam/guard.py

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+import struct
+from binascii import hexlify
+from time import time
+from steam import webapi
+from steam.core.crypto import hmac_sha1, sha1_hash
+
+def generate_twofactor_code(shared_secret):
+    """Generate Steam 2FA code for login with current time
+
+    :param shared_secret: authenticator shared shared_secret
+    :type shared_secret: bytes
+    :return: steam two factor code
+    :rtype: str
+    """
+    return generate_twofactor_code_for_time(shared_secret, time() + get_time_offset())
+
+def generate_twofactor_code_for_time(shared_secret, timestamp):
+    """Generate Steam 2FA code for timestamp
+
+    :param shared_secret: authenticator shared secret
+    :type shared_secret: bytes
+    :param timestamp: timestamp to use, if left out uses current time
+    :type timestamp: int
+    :return: steam two factor code
+    :rtype: str
+    """
+    hmac = hmac_sha1(bytes(shared_secret),
+                     struct.pack('>Q', int(timestamp)//30))  # this will NOT stop working in 2038
+
+    start = ord(hmac[19:20]) & 0xF
+    codeint = struct.unpack('>I', hmac[start:start+4])[0] & 0x7fffffff
+
+    charset = '23456789BCDFGHJKMNPQRTVWXY'
+    code = ''
+
+    for _ in range(5):
+        codeint, i = divmod(codeint, len(charset))
+        code += charset[i]
+
+    return code
+
+def generate_confirmation_key(identity_secret, timestamp, tag=''):
+    """Generate confirmation key for trades. Can only be used once.
+
+    :param identity_secret: authenticator identity secret
+    :type identity_secret: bytes
+    :param timestamp: timestamp to use for generating key
+    :type timestamp: int
+    :param tag: tag identifies what the request, see list below
+    :type tag: str
+    :return: confirmation key
+    :rtype: bytes
+
+    Tag choices:
+
+        * ``conf`` to load the confirmations page
+        * ``details`` to load details about a trade
+        * ``allow`` to confirm a trade
+        * ``cancel`` to cancel a trade
+
+    """
+    data = struct.pack('>Q', int(timestamp)) + tag.encode('ascii') # this will NOT stop working in 2038
+    return hmac_sha1(bytes(identity_secret), data)
+
+def get_time_offset():
+    """Get time offset from steam server time via WebAPI
+
+    :return: time offset
+    :rtype: int
+    """
+    try:
+        resp = webapi.post('ITwoFactorService', 'QueryTime', 1, params={'http_timeout': 5})
+    except:
+        return 0
+
+    ts = int(time())
+    return int(resp.get('response', {}).get('server_time', ts)) - ts
+
+def generate_device_id(steamid):
+    """Generate Android device id
+
+    :param steamid: Steam ID
+    :type steamid: :class:`.SteamID`, :class:`int`
+    :return: android device id
+    :rtype: str
+    """
+    h = hexlify(sha1(str(steamid).encode('ascii'))).decode('ascii')
+    return "android:%s-%s-%s-%s-%s" % (h[:8], h[8:12], h[12:16], h[16:20], h[20:32])

tests/test_guard.py

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+import unittest
+import mock
+
+from steam import guard as g
+
+class TCguard(unittest.TestCase):
+    def test_generate_twofactor_code_for_time(self):
+        code = g.generate_twofactor_code_for_time(b'superdupersecret', timestamp=3000030)
+        self.assertEqual(code, 'YRGQJ')
+
+        code = g.generate_twofactor_code_for_time(b'superdupersecret', timestamp=3000029)
+        self.assertEqual(code, '94R9D')
+
+    def test_generate_confirmation_key(self):
+        key = g.generate_confirmation_key(b'itsmemario', 100000)
+        self.assertEqual(key, b'\xed\xb5\xe5\xad\x8f\xf1\x99\x01\xc8-w\xd6\xb5 p\xccz\xd7\xd1\x05')
+
+        key = g.generate_confirmation_key(b'itsmemario', 100000, 'allow')
+        self.assertEqual(key, b"Q'\x06\x80\xe1g\xa8m$\xb2hV\xe6g\x8b'\x8f\xf1L\xb0")