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426 lines
18 KiB
Python
426 lines
18 KiB
Python
#!/usr/bin/python
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# Copyright 2017, The Tor Project, Inc
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# See LICENSE for licensing information
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"""
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hs_ntor_ref.py
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This module is a reference implementation of the modified ntor protocol
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proposed for Tor hidden services in proposal 224 (Next Generation Hidden
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Services) in section [NTOR-WITH-EXTRA-DATA].
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The modified ntor protocol is a single-round protocol, with three steps in total:
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1: Client generates keys and sends them to service via INTRODUCE cell
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2: Service computes key material based on client's keys, and sends its own
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keys to client via RENDEZVOUS cell
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3: Client computes key material as well.
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It's meant to be used to validate Tor's HS ntor implementation by conducting
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various integration tests. Specifically it conducts the following three tests:
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- Tests our Python implementation by running the whole protocol in Python and
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making sure that results are consistent.
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- Tests little-t-tor ntor implementation. We use this Python code to instrument
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little-t-tor and carry out the handshake by using little-t-tor code. The
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small C wrapper at src/test/test-hs-ntor-cl is used for this Python module to
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interface with little-t-tor.
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- Cross-tests Python and little-t-tor implementation by running half of the
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protocol in Python code and the other in little-t-tor. This is actually two
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tests so that all parts of the protocol are run both by little-t-tor and
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Python.
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It requires the curve25519 python module from the curve25519-donna package.
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The whole logic and concept for this test suite was taken from ntor_ref.py.
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*** DO NOT USE THIS IN PRODUCTION. ***
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"""
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import struct
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import os, sys
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import binascii
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import subprocess
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try:
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import curve25519
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curve25519mod = curve25519.keys
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except ImportError:
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curve25519 = None
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import slownacl_curve25519
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curve25519mod = slownacl_curve25519
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import hashlib
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try:
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import sha3
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except ImportError:
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# In python 3.6, the sha3 functions are in hashlib whether we
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# import sha3 or not.
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sha3 = None
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try:
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# Pull the sha3 functions in.
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from hashlib import sha3_256, shake_256
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shake_squeeze = shake_256.digest
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except ImportError:
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if hasattr(sha3, "SHA3256"):
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# If this happens, then we have the old "sha3" module which
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# hashlib and pysha3 superseded.
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sha3_256 = sha3.SHA3256
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shake_256 = sha3.SHAKE256
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shake_squeeze = shake_256.squeeze
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else:
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# error code 77 tells automake to skip this test
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sys.exit(77)
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# Import Nick's ntor reference implementation in Python
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# We are gonna use a few of its utilities.
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from ntor_ref import hash_nil
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from ntor_ref import PrivateKey
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# String constants used in this protocol
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PROTOID = b"tor-hs-ntor-curve25519-sha3-256-1"
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T_HSENC = PROTOID + b":hs_key_extract"
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T_HSVERIFY = PROTOID + b":hs_verify"
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T_HSMAC = PROTOID + b":hs_mac"
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M_HSEXPAND = PROTOID + b":hs_key_expand"
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INTRO_SECRET_LEN = 161
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REND_SECRET_LEN = 225
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AUTH_INPUT_LEN = 199
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# Implements MAC(k,m) = H(htonll(len(k)) | k | m)
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def mac(k,m):
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def htonll(num):
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return struct.pack('!q', num)
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s = sha3_256()
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s.update(htonll(len(k)))
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s.update(k)
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s.update(m)
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return s.digest()
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######################################################################
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# Functions that implement the modified HS ntor protocol
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"""As client compute key material for INTRODUCE cell as follows:
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intro_secret_hs_input = EXP(B,x) | AUTH_KEY | X | B | PROTOID
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info = m_hsexpand | subcredential
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hs_keys = KDF(intro_secret_hs_input | t_hsenc | info, S_KEY_LEN+MAC_LEN)
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ENC_KEY = hs_keys[0:S_KEY_LEN]
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MAC_KEY = hs_keys[S_KEY_LEN:S_KEY_LEN+MAC_KEY_LEN]
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"""
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def intro2_ntor_client(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential):
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dh_result = client_ephemeral_enc_privkey.get_shared_key(intro_enc_pubkey, hash_nil)
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secret = dh_result + intro_auth_pubkey_str + client_ephemeral_enc_pubkey.serialize() + intro_enc_pubkey.serialize() + PROTOID
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assert(len(secret) == INTRO_SECRET_LEN)
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info = M_HSEXPAND + subcredential
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kdf = shake_256()
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kdf.update(secret + T_HSENC + info)
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key_material = shake_squeeze(kdf, 64*8)
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enc_key = key_material[0:32]
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mac_key = key_material[32:64]
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return enc_key, mac_key
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"""Wrapper over intro2_ntor_client()"""
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def client_part1(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential):
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enc_key, mac_key = intro2_ntor_client(intro_auth_pubkey_str, intro_enc_pubkey, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential)
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assert(enc_key)
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assert(mac_key)
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return enc_key, mac_key
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"""As service compute key material for INTRODUCE cell as follows:
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intro_secret_hs_input = EXP(X,b) | AUTH_KEY | X | B | PROTOID
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info = m_hsexpand | subcredential
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hs_keys = KDF(intro_secret_hs_input | t_hsenc | info, S_KEY_LEN+MAC_LEN)
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HS_DEC_KEY = hs_keys[0:S_KEY_LEN]
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HS_MAC_KEY = hs_keys[S_KEY_LEN:S_KEY_LEN+MAC_KEY_LEN]
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"""
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def intro2_ntor_service(intro_auth_pubkey_str, client_enc_pubkey, service_enc_privkey, service_enc_pubkey, subcredential):
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dh_result = service_enc_privkey.get_shared_key(client_enc_pubkey, hash_nil)
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secret = dh_result + intro_auth_pubkey_str + client_enc_pubkey.serialize() + service_enc_pubkey.serialize() + PROTOID
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assert(len(secret) == INTRO_SECRET_LEN)
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info = M_HSEXPAND + subcredential
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kdf = shake_256()
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kdf.update(secret + T_HSENC + info)
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key_material = shake_squeeze(kdf, 64*8)
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enc_key = key_material[0:32]
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mac_key = key_material[32:64]
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return enc_key, mac_key
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"""As service compute key material for INTRODUCE and REDNEZVOUS cells.
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Use intro2_ntor_service() to calculate the INTRODUCE key material, and use
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the following computations to do the RENDEZVOUS ones:
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rend_secret_hs_input = EXP(X,y) | EXP(X,b) | AUTH_KEY | B | X | Y | PROTOID
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NTOR_KEY_SEED = MAC(rend_secret_hs_input, t_hsenc)
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verify = MAC(rend_secret_hs_input, t_hsverify)
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auth_input = verify | AUTH_KEY | B | Y | X | PROTOID | "Server"
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AUTH_INPUT_MAC = MAC(auth_input, t_hsmac)
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"""
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def service_part1(intro_auth_pubkey_str, client_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential):
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intro_enc_key, intro_mac_key = intro2_ntor_service(intro_auth_pubkey_str, client_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential)
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assert(intro_enc_key)
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assert(intro_mac_key)
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service_ephemeral_privkey = PrivateKey()
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service_ephemeral_pubkey = service_ephemeral_privkey.get_public()
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dh_result1 = service_ephemeral_privkey.get_shared_key(client_enc_pubkey, hash_nil)
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dh_result2 = intro_enc_privkey.get_shared_key(client_enc_pubkey, hash_nil)
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rend_secret_hs_input = dh_result1 + dh_result2 + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + client_enc_pubkey.serialize() + service_ephemeral_pubkey.serialize() + PROTOID
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assert(len(rend_secret_hs_input) == REND_SECRET_LEN)
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ntor_key_seed = mac(rend_secret_hs_input, T_HSENC)
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verify = mac(rend_secret_hs_input, T_HSVERIFY)
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auth_input = verify + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + service_ephemeral_pubkey.serialize() + client_enc_pubkey.serialize() + PROTOID + b"Server"
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assert(len(auth_input) == AUTH_INPUT_LEN)
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auth_input_mac = mac(auth_input, T_HSMAC)
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assert(ntor_key_seed)
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assert(auth_input_mac)
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assert(service_ephemeral_pubkey)
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return intro_enc_key, intro_mac_key, ntor_key_seed, auth_input_mac, service_ephemeral_pubkey
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"""As client compute key material for rendezvous cells as follows:
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rend_secret_hs_input = EXP(Y,x) | EXP(B,x) | AUTH_KEY | B | X | Y | PROTOID
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NTOR_KEY_SEED = MAC(ntor_secret_input, t_hsenc)
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verify = MAC(ntor_secret_input, t_hsverify)
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auth_input = verify | AUTH_KEY | B | Y | X | PROTOID | "Server"
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AUTH_INPUT_MAC = MAC(auth_input, t_hsmac)
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"""
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def client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_ephemeral_rend_pubkey):
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dh_result1 = client_ephemeral_enc_privkey.get_shared_key(service_ephemeral_rend_pubkey, hash_nil)
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dh_result2 = client_ephemeral_enc_privkey.get_shared_key(intro_enc_pubkey, hash_nil)
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rend_secret_hs_input = dh_result1 + dh_result2 + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + client_ephemeral_enc_pubkey.serialize() + service_ephemeral_rend_pubkey.serialize() + PROTOID
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assert(len(rend_secret_hs_input) == REND_SECRET_LEN)
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ntor_key_seed = mac(rend_secret_hs_input, T_HSENC)
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verify = mac(rend_secret_hs_input, T_HSVERIFY)
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auth_input = verify + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + service_ephemeral_rend_pubkey.serialize() + client_ephemeral_enc_pubkey.serialize() + PROTOID + b"Server"
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assert(len(auth_input) == AUTH_INPUT_LEN)
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auth_input_mac = mac(auth_input, T_HSMAC)
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assert(ntor_key_seed)
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assert(auth_input_mac)
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return ntor_key_seed, auth_input_mac
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#################################################################################
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"""
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Utilities for communicating with the little-t-tor ntor wrapper to conduct the
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integration tests
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"""
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PROG = b"./src/test/test-hs-ntor-cl"
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enhex=lambda s: binascii.b2a_hex(s)
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dehex=lambda s: binascii.a2b_hex(s.strip())
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def tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_privkey, subcredential):
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p = subprocess.Popen([PROG, "client1",
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enhex(intro_auth_pubkey_str),
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enhex(intro_enc_pubkey.serialize()),
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enhex(client_ephemeral_enc_privkey.serialize()),
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enhex(subcredential)],
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stdout=subprocess.PIPE)
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return map(dehex, p.stdout.readlines())
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def tor_server1(intro_auth_pubkey_str, intro_enc_privkey,
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client_ephemeral_enc_pubkey, subcredential):
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p = subprocess.Popen([PROG, "server1",
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enhex(intro_auth_pubkey_str),
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enhex(intro_enc_privkey.serialize()),
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enhex(client_ephemeral_enc_pubkey.serialize()),
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enhex(subcredential)],
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stdout=subprocess.PIPE)
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return map(dehex, p.stdout.readlines())
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def tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_ephemeral_rend_pubkey, subcredential):
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p = subprocess.Popen([PROG, "client2",
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enhex(intro_auth_pubkey_str),
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enhex(client_ephemeral_enc_privkey.serialize()),
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enhex(intro_enc_pubkey.serialize()),
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enhex(service_ephemeral_rend_pubkey.serialize()),
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enhex(subcredential)],
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stdout=subprocess.PIPE)
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return map(dehex, p.stdout.readlines())
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##################################################################################
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# Perform a pure python ntor test
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def do_pure_python_ntor_test():
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# Initialize all needed key material
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client_ephemeral_enc_privkey = PrivateKey()
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client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
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intro_enc_privkey = PrivateKey()
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intro_enc_pubkey = intro_enc_privkey.get_public()
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intro_auth_pubkey_str = os.urandom(32)
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subcredential = os.urandom(32)
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client_enc_key, client_mac_key = client_part1(intro_auth_pubkey_str, intro_enc_pubkey, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential)
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service_enc_key, service_mac_key, service_ntor_key_seed, service_auth_input_mac, service_ephemeral_pubkey = service_part1(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential)
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assert(client_enc_key == service_enc_key)
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assert(client_mac_key == service_mac_key)
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client_ntor_key_seed, client_auth_input_mac = client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_ephemeral_pubkey)
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assert(client_ntor_key_seed == service_ntor_key_seed)
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assert(client_auth_input_mac == service_auth_input_mac)
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print("DONE: python dance [%s]" % repr(client_auth_input_mac))
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# Perform a pure little-t-tor integration test.
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def do_little_t_tor_ntor_test():
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# Initialize all needed key material
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subcredential = os.urandom(32)
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client_ephemeral_enc_privkey = PrivateKey()
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client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
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intro_enc_privkey = PrivateKey()
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intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
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intro_auth_pubkey_str = os.urandom(32)
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client_enc_key, client_mac_key = tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_privkey, subcredential)
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assert(client_enc_key)
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assert(client_mac_key)
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service_enc_key, service_mac_key, service_ntor_auth_mac, service_ntor_key_seed, service_eph_pubkey = tor_server1(intro_auth_pubkey_str,
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intro_enc_privkey,
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client_ephemeral_enc_pubkey,
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subcredential)
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assert(service_enc_key)
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assert(service_mac_key)
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assert(service_ntor_auth_mac)
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assert(service_ntor_key_seed)
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assert(client_enc_key == service_enc_key)
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assert(client_mac_key == service_mac_key)
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# Turn from bytes to key
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service_eph_pubkey = curve25519mod.Public(service_eph_pubkey)
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client_ntor_auth_mac, client_ntor_key_seed = tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_eph_pubkey, subcredential)
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assert(client_ntor_auth_mac)
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assert(client_ntor_key_seed)
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assert(client_ntor_key_seed == service_ntor_key_seed)
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assert(client_ntor_auth_mac == service_ntor_auth_mac)
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print("DONE: tor dance [%s]" % repr(client_ntor_auth_mac))
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"""
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Do mixed test as follows:
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1. C -> S (python mode)
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2. C <- S (tor mode)
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3. Client computes keys (python mode)
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"""
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def do_first_mixed_test():
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subcredential = os.urandom(32)
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client_ephemeral_enc_privkey = PrivateKey()
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client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
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intro_enc_privkey = PrivateKey()
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intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
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intro_auth_pubkey_str = os.urandom(32)
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# Let's do mixed
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client_enc_key, client_mac_key = client_part1(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
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subcredential)
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service_enc_key, service_mac_key, service_ntor_auth_mac, service_ntor_key_seed, service_eph_pubkey = tor_server1(intro_auth_pubkey_str,
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intro_enc_privkey,
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client_ephemeral_enc_pubkey,
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subcredential)
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assert(service_enc_key)
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assert(service_mac_key)
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assert(service_ntor_auth_mac)
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assert(service_ntor_key_seed)
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assert(service_eph_pubkey)
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assert(client_enc_key == service_enc_key)
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assert(client_mac_key == service_mac_key)
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# Turn from bytes to key
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service_eph_pubkey = curve25519mod.Public(service_eph_pubkey)
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client_ntor_key_seed, client_auth_input_mac = client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_eph_pubkey)
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assert(client_auth_input_mac == service_ntor_auth_mac)
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assert(client_ntor_key_seed == service_ntor_key_seed)
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print("DONE: 1st mixed dance [%s]" % repr(client_auth_input_mac))
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"""
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Do mixed test as follows:
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1. C -> S (tor mode)
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2. C <- S (python mode)
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3. Client computes keys (tor mode)
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"""
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def do_second_mixed_test():
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subcredential = os.urandom(32)
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client_ephemeral_enc_privkey = PrivateKey()
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client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
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intro_enc_privkey = PrivateKey()
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intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
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intro_auth_pubkey_str = os.urandom(32)
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# Let's do mixed
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client_enc_key, client_mac_key = tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
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client_ephemeral_enc_privkey, subcredential)
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assert(client_enc_key)
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assert(client_mac_key)
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service_enc_key, service_mac_key, service_ntor_key_seed, service_ntor_auth_mac, service_ephemeral_pubkey = service_part1(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential)
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client_ntor_auth_mac, client_ntor_key_seed = tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
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intro_enc_pubkey, service_ephemeral_pubkey, subcredential)
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assert(client_ntor_auth_mac)
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assert(client_ntor_key_seed)
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assert(client_ntor_key_seed == service_ntor_key_seed)
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assert(client_ntor_auth_mac == service_ntor_auth_mac)
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|
|
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print("DONE: 2nd mixed dance [%s]" % repr(client_ntor_auth_mac))
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def do_mixed_tests():
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do_first_mixed_test()
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|
do_second_mixed_test()
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|
|
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if __name__ == '__main__':
|
|
do_pure_python_ntor_test()
|
|
do_little_t_tor_ntor_test()
|
|
do_mixed_tests()
|