prop224: Add Python integration tests for HS ntor.

This test is identical to the ./src/test/test_ntor.sh integration test.

.gitignore

@@ -179,6 +179,7 @@ uptime-*.json
 /src/test/test-child
 /src/test/test-memwipe
 /src/test/test-ntor-cl
+/src/test/test-hs-ntor-cl
 /src/test/test-switch-id
 /src/test/test-timers
 /src/test/test_workqueue
@@ -187,6 +188,7 @@ uptime-*.json
 /src/test/test-bt-cl.exe
 /src/test/test-child.exe
 /src/test/test-ntor-cl.exe
+/src/test/test-hs-ntor-cl.exe
 /src/test/test-memwipe.exe
 /src/test/test-switch-id.exe
 /src/test/test-timers.exe

src/test/hs_ntor_ref.py

@@ -0,0 +1,408 @@
+#!/usr/bin/python
+# Copyright 2017, The Tor Project, Inc
+# See LICENSE for licensing information
+
+"""
+hs_ntor_ref.py
+
+This module is a reference implementation of the modified ntor protocol
+proposed for Tor hidden services in proposal 224 (Next Generation Hidden
+Services) in section [NTOR-WITH-EXTRA-DATA].
+
+The modified ntor protocol is a single-round protocol, with three steps in total:
+
+    1: Client generates keys and sends them to service via INTRODUCE cell
+
+    2: Service computes key material based on client's keys, and sends its own
+       keys to client via RENDEZVOUS cell
+
+    3: Client computes key material as well.
+
+It's meant to be used to validate Tor's HS ntor implementation by conducting
+various integration tests. Specifically it conducts the following three tests:
+
+- Tests our Python implementation by running the whole protocol in Python and
+  making sure that results are consistent.
+
+- Tests little-t-tor ntor implementation. We use this Python code to instrument
+  little-t-tor and carry out the handshake by using little-t-tor code. The
+  small C wrapper at src/test/test-hs-ntor-cl is used for this Python module to
+  interface with little-t-tor.
+
+- Cross-tests Python and little-t-tor implementation by running half of the
+  protocol in Python code and the other in little-t-tor. This is actually two
+  tests so that all parts of the protocol are run both by little-t-tor and
+  Python.
+
+It requires the curve25519 python module from the curve25519-donna package.
+
+The whole logic and concept for this test suite was taken from ntor_ref.py.
+
+                *** DO NOT USE THIS IN PRODUCTION. ***
+"""
+
+import struct
+import os, sys
+import binascii
+import subprocess
+
+try:
+    import curve25519
+    curve25519mod = curve25519.keys
+except ImportError:
+    curve25519 = None
+    import slownacl_curve25519
+    curve25519mod = slownacl_curve25519
+
+try:
+    import sha3
+except ImportError:
+    # error code 77 tells automake to skip this test
+    sys.exit(77)
+
+# Import Nick's ntor reference implementation in Python
+# We are gonna use a few of its utilities.
+from ntor_ref import hash_nil
+from ntor_ref import PrivateKey
+
+# String constants used in this protocol
+PROTOID = "tor-hs-ntor-curve25519-sha3-256-1"
+T_HSENC    = PROTOID + ":hs_key_extract"
+T_HSVERIFY = PROTOID + ":hs_verify"
+T_HSMAC    = PROTOID + ":hs_mac"
+M_HSEXPAND = PROTOID + ":hs_key_expand"
+
+INTRO_SECRET_LEN = 161
+REND_SECRET_LEN = 225
+AUTH_INPUT_LEN = 199
+
+# Implements MAC(k,m) = H(htonll(len(k)) | k | m)
+def mac(k,m):
+    def htonll(num):
+        return struct.pack('!q', num)
+
+    s = sha3.SHA3256()
+    s.update(htonll(len(k)))
+    s.update(k)
+    s.update(m)
+    return s.digest()
+
+######################################################################
+
+# Functions that implement the modified HS ntor protocol
+
+"""As client compute key material for INTRODUCE cell as follows:
+
+  intro_secret_hs_input = EXP(B,x) | AUTH_KEY | X | B | PROTOID
+  info = m_hsexpand | subcredential
+  hs_keys = KDF(intro_secret_hs_input | t_hsenc | info, S_KEY_LEN+MAC_LEN)
+  ENC_KEY = hs_keys[0:S_KEY_LEN]
+  MAC_KEY = hs_keys[S_KEY_LEN:S_KEY_LEN+MAC_KEY_LEN]
+"""
+def intro2_ntor_client(intro_auth_pubkey_str, intro_enc_pubkey,
+                       client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential):
+
+    dh_result = client_ephemeral_enc_privkey.get_shared_key(intro_enc_pubkey, hash_nil)
+    secret =  dh_result + intro_auth_pubkey_str + client_ephemeral_enc_pubkey.serialize() + intro_enc_pubkey.serialize() + PROTOID
+    assert(len(secret) == INTRO_SECRET_LEN)
+    info = M_HSEXPAND + subcredential
+
+    kdf = sha3.SHAKE256()
+    kdf.update(secret + T_HSENC + info)
+    key_material = kdf.squeeze(64*8)
+
+    enc_key = key_material[0:32]
+    mac_key = key_material[32:64]
+
+    return enc_key, mac_key
+
+"""Wrapper over intro2_ntor_client()"""
+def client_part1(intro_auth_pubkey_str, intro_enc_pubkey,
+                 client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential):
+    enc_key, mac_key = intro2_ntor_client(intro_auth_pubkey_str, intro_enc_pubkey, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential)
+    assert(enc_key)
+    assert(mac_key)
+
+    return enc_key, mac_key
+
+"""As service compute key material for INTRODUCE cell as follows:
+
+  intro_secret_hs_input = EXP(X,b) | AUTH_KEY | X | B | PROTOID
+  info = m_hsexpand | subcredential
+  hs_keys = KDF(intro_secret_hs_input | t_hsenc | info, S_KEY_LEN+MAC_LEN)
+  HS_DEC_KEY = hs_keys[0:S_KEY_LEN]
+  HS_MAC_KEY = hs_keys[S_KEY_LEN:S_KEY_LEN+MAC_KEY_LEN]
+"""
+def intro2_ntor_service(intro_auth_pubkey_str, client_enc_pubkey, service_enc_privkey, service_enc_pubkey, subcredential):
+    dh_result = service_enc_privkey.get_shared_key(client_enc_pubkey, hash_nil)
+    secret = dh_result + intro_auth_pubkey_str + client_enc_pubkey.serialize() + service_enc_pubkey.serialize() + PROTOID
+    assert(len(secret) == INTRO_SECRET_LEN)
+    info = M_HSEXPAND + subcredential
+
+    kdf = sha3.SHAKE256()
+    kdf.update(secret + T_HSENC + info)
+    key_material = kdf.squeeze(64*8)
+
+    enc_key = key_material[0:32]
+    mac_key = key_material[32:64]
+
+    return enc_key, mac_key
+
+"""As service compute key material for INTRODUCE and REDNEZVOUS cells.
+
+  Use intro2_ntor_service() to calculate the INTRODUCE key material, and use
+  the following computations to do the RENDEZVOUS ones:
+
+      rend_secret_hs_input = EXP(X,y) | EXP(X,b) | AUTH_KEY | B | X | Y | PROTOID
+      NTOR_KEY_SEED = MAC(rend_secret_hs_input, t_hsenc)
+      verify = MAC(rend_secret_hs_input, t_hsverify)
+      auth_input = verify | AUTH_KEY | B | Y | X | PROTOID | "Server"
+      AUTH_INPUT_MAC = MAC(auth_input, t_hsmac)
+"""
+def service_part1(intro_auth_pubkey_str, client_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential):
+    intro_enc_key, intro_mac_key = intro2_ntor_service(intro_auth_pubkey_str, client_enc_pubkey, intro_enc_privkey, intro_enc_pubkey, subcredential)
+    assert(intro_enc_key)
+    assert(intro_mac_key)
+
+    service_ephemeral_privkey = PrivateKey()
+    service_ephemeral_pubkey = service_ephemeral_privkey.get_public()
+
+    dh_result1 = service_ephemeral_privkey.get_shared_key(client_enc_pubkey, hash_nil)
+    dh_result2 = intro_enc_privkey.get_shared_key(client_enc_pubkey, hash_nil)
+    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
+    assert(len(rend_secret_hs_input) == REND_SECRET_LEN)
+
+    ntor_key_seed = mac(rend_secret_hs_input, T_HSENC)
+    verify = mac(rend_secret_hs_input, T_HSVERIFY)
+    auth_input = verify + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + service_ephemeral_pubkey.serialize() + client_enc_pubkey.serialize() + PROTOID + "Server"
+    assert(len(auth_input) == AUTH_INPUT_LEN)
+    auth_input_mac = mac(auth_input, T_HSMAC)
+
+    assert(ntor_key_seed)
+    assert(auth_input_mac)
+    assert(service_ephemeral_pubkey)
+
+    return intro_enc_key, intro_mac_key, ntor_key_seed, auth_input_mac, service_ephemeral_pubkey
+
+"""As client compute key material for rendezvous cells as follows:
+
+  rend_secret_hs_input = EXP(Y,x) | EXP(B,x) | AUTH_KEY | B | X | Y | PROTOID
+  NTOR_KEY_SEED = MAC(ntor_secret_input, t_hsenc)
+  verify = MAC(ntor_secret_input, t_hsverify)
+  auth_input = verify | AUTH_KEY | B | Y | X | PROTOID | "Server"
+  AUTH_INPUT_MAC = MAC(auth_input, t_hsmac)
+"""
+def client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
+                 intro_enc_pubkey, service_ephemeral_rend_pubkey):
+    dh_result1 = client_ephemeral_enc_privkey.get_shared_key(service_ephemeral_rend_pubkey, hash_nil)
+    dh_result2 = client_ephemeral_enc_privkey.get_shared_key(intro_enc_pubkey, hash_nil)
+    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
+    assert(len(rend_secret_hs_input) == REND_SECRET_LEN)
+
+    ntor_key_seed = mac(rend_secret_hs_input, T_HSENC)
+    verify = mac(rend_secret_hs_input, T_HSVERIFY)
+    auth_input = verify + intro_auth_pubkey_str + intro_enc_pubkey.serialize() + service_ephemeral_rend_pubkey.serialize() + client_ephemeral_enc_pubkey.serialize() + PROTOID + "Server"
+    assert(len(auth_input) == AUTH_INPUT_LEN)
+    auth_input_mac = mac(auth_input, T_HSMAC)
+
+    assert(ntor_key_seed)
+    assert(auth_input_mac)
+
+    return ntor_key_seed, auth_input_mac
+
+#################################################################################
+
+"""
+Utilities for communicating with the little-t-tor ntor wrapper to conduct the
+integration tests
+"""
+
+PROG = b"./src/test/test-hs-ntor-cl"
+enhex=lambda s: binascii.b2a_hex(s)
+dehex=lambda s: binascii.a2b_hex(s.strip())
+
+def tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
+                client_ephemeral_enc_privkey, subcredential):
+    p = subprocess.Popen([PROG, "client1",
+                          enhex(intro_auth_pubkey_str),
+                          enhex(intro_enc_pubkey.serialize()),
+                          enhex(client_ephemeral_enc_privkey.serialize()),
+                          enhex(subcredential)],
+                         stdout=subprocess.PIPE)
+    return map(dehex, p.stdout.readlines())
+
+def tor_server1(intro_auth_pubkey_str, intro_enc_privkey,
+                client_ephemeral_enc_pubkey, subcredential):
+    p = subprocess.Popen([PROG, "server1",
+                          enhex(intro_auth_pubkey_str),
+                          enhex(intro_enc_privkey.serialize()),
+                          enhex(client_ephemeral_enc_pubkey.serialize()),
+                          enhex(subcredential)],
+                         stdout=subprocess.PIPE)
+    return map(dehex, p.stdout.readlines())
+
+def tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
+                intro_enc_pubkey, service_ephemeral_rend_pubkey, subcredential):
+    p = subprocess.Popen([PROG, "client2",
+                          enhex(intro_auth_pubkey_str),
+                          enhex(client_ephemeral_enc_privkey.serialize()),
+                          enhex(intro_enc_pubkey.serialize()),
+                          enhex(service_ephemeral_rend_pubkey.serialize()),
+                          enhex(subcredential)],
+                         stdout=subprocess.PIPE)
+    return map(dehex, p.stdout.readlines())
+
+##################################################################################
+
+# Perform a pure python ntor test
+def do_pure_python_ntor_test():
+    # Initialize all needed key material
+    client_ephemeral_enc_privkey = PrivateKey()
+    client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
+    intro_enc_privkey = PrivateKey()
+    intro_enc_pubkey = intro_enc_privkey.get_public()
+    intro_auth_pubkey_str = os.urandom(32)
+    subcredential = os.urandom(32)
+
+    client_enc_key, client_mac_key = client_part1(intro_auth_pubkey_str, intro_enc_pubkey, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey, subcredential)
+
+    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)
+
+    assert(client_enc_key == service_enc_key)
+    assert(client_mac_key == service_mac_key)
+
+    client_ntor_key_seed, client_auth_input_mac = client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
+                                                               intro_enc_pubkey, service_ephemeral_pubkey)
+
+    assert(client_ntor_key_seed == service_ntor_key_seed)
+    assert(client_auth_input_mac == service_auth_input_mac)
+
+    print "DONE: python dance [%s]" % repr(client_auth_input_mac)
+
+# Perform a pure little-t-tor integration test.
+def do_little_t_tor_ntor_test():
+    # Initialize all needed key material
+    subcredential = os.urandom(32)
+    client_ephemeral_enc_privkey = PrivateKey()
+    client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
+    intro_enc_privkey = PrivateKey()
+    intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
+    intro_auth_pubkey_str = os.urandom(32)
+
+    client_enc_key, client_mac_key = tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
+                                                 client_ephemeral_enc_privkey, subcredential)
+    assert(client_enc_key)
+    assert(client_mac_key)
+
+    service_enc_key, service_mac_key, service_ntor_auth_mac, service_ntor_key_seed, service_eph_pubkey = tor_server1(intro_auth_pubkey_str,
+                                                                                                                     intro_enc_privkey,
+                                                                                                                     client_ephemeral_enc_pubkey,
+                                                                                                                     subcredential)
+    assert(service_enc_key)
+    assert(service_mac_key)
+    assert(service_ntor_auth_mac)
+    assert(service_ntor_key_seed)
+
+    assert(client_enc_key == service_enc_key)
+    assert(client_mac_key == service_mac_key)
+
+    # Turn from bytes to key
+    service_eph_pubkey = curve25519mod.Public(service_eph_pubkey)
+
+    client_ntor_auth_mac, client_ntor_key_seed  = tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
+                                                              intro_enc_pubkey, service_eph_pubkey, subcredential)
+    assert(client_ntor_auth_mac)
+    assert(client_ntor_key_seed)
+
+    assert(client_ntor_key_seed == service_ntor_key_seed)
+    assert(client_ntor_auth_mac == service_ntor_auth_mac)
+
+    print "DONE: tor dance [%s]" % repr(client_ntor_auth_mac)
+
+"""
+Do mixed test as follows:
+    1. C -> S (python mode)
+    2. C <- S (tor mode)
+    3. Client computes keys (python mode)
+"""
+def do_first_mixed_test():
+    subcredential = os.urandom(32)
+
+    client_ephemeral_enc_privkey = PrivateKey()
+    client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
+    intro_enc_privkey = PrivateKey()
+    intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
+
+    intro_auth_pubkey_str = os.urandom(32)
+
+    # Let's do mixed
+    client_enc_key, client_mac_key = client_part1(intro_auth_pubkey_str, intro_enc_pubkey,
+                                                  client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
+                                                  subcredential)
+
+    service_enc_key, service_mac_key, service_ntor_auth_mac, service_ntor_key_seed, service_eph_pubkey = tor_server1(intro_auth_pubkey_str,
+                                                                                                                     intro_enc_privkey,
+                                                                                                                     client_ephemeral_enc_pubkey,
+                                                                                                                     subcredential)
+    assert(service_enc_key)
+    assert(service_mac_key)
+    assert(service_ntor_auth_mac)
+    assert(service_ntor_key_seed)
+    assert(service_eph_pubkey)
+
+    assert(client_enc_key == service_enc_key)
+    assert(client_mac_key == service_mac_key)
+
+    # Turn from bytes to key
+    service_eph_pubkey = curve25519mod.Public(service_eph_pubkey)
+
+    client_ntor_key_seed, client_auth_input_mac = client_part2(intro_auth_pubkey_str, client_ephemeral_enc_pubkey, client_ephemeral_enc_privkey,
+                                                               intro_enc_pubkey, service_eph_pubkey)
+
+    assert(client_auth_input_mac == service_ntor_auth_mac)
+    assert(client_ntor_key_seed == service_ntor_key_seed)
+
+    print "DONE: 1st mixed dance [%s]" % repr(client_auth_input_mac)
+
+"""
+Do mixed test as follows:
+    1. C -> S (tor mode)
+    2. C <- S (python mode)
+    3. Client computes keys (tor mode)
+"""
+def do_second_mixed_test():
+    subcredential = os.urandom(32)
+
+    client_ephemeral_enc_privkey = PrivateKey()
+    client_ephemeral_enc_pubkey = client_ephemeral_enc_privkey.get_public()
+    intro_enc_privkey = PrivateKey()
+    intro_enc_pubkey = intro_enc_privkey.get_public() # service-side enc key
+
+    intro_auth_pubkey_str = os.urandom(32)
+
+    # Let's do mixed
+    client_enc_key, client_mac_key = tor_client1(intro_auth_pubkey_str, intro_enc_pubkey,
+                                                 client_ephemeral_enc_privkey, subcredential)
+    assert(client_enc_key)
+    assert(client_mac_key)
+
+    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)
+
+    client_ntor_auth_mac, client_ntor_key_seed  = tor_client2(intro_auth_pubkey_str, client_ephemeral_enc_privkey,
+                                                              intro_enc_pubkey, service_ephemeral_pubkey, subcredential)
+    assert(client_ntor_auth_mac)
+    assert(client_ntor_key_seed)
+
+    assert(client_ntor_key_seed == service_ntor_key_seed)
+    assert(client_ntor_auth_mac == service_ntor_auth_mac)
+
+    print "DONE: 2nd mixed dance [%s]" % repr(client_ntor_auth_mac)
+
+def do_mixed_tests():
+    do_first_mixed_test()
+    do_second_mixed_test()
+
+if __name__ == '__main__':
+    do_pure_python_ntor_test()
+    do_little_t_tor_ntor_test()
+    do_mixed_tests()

src/test/include.am

@@ -20,7 +20,7 @@ TESTSCRIPTS = \
 	src/test/test_switch_id.sh
 
 if USEPYTHON
-TESTSCRIPTS += src/test/test_ntor.sh src/test/test_bt.sh
+TESTSCRIPTS += src/test/test_ntor.sh src/test/test_hs_ntor.sh src/test/test_bt.sh
 endif
 
 TESTS += src/test/test src/test/test-slow src/test/test-memwipe \
@@ -249,6 +249,7 @@ noinst_HEADERS+= \
 	src/test/vote_descriptors.inc
 
 noinst_PROGRAMS+= src/test/test-ntor-cl
+noinst_PROGRAMS+= src/test/test-hs-ntor-cl
 src_test_test_ntor_cl_SOURCES  = src/test/test_ntor_cl.c
 src_test_test_ntor_cl_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@
 src_test_test_ntor_cl_LDADD = src/or/libtor.a src/common/libor.a \
@@ -259,6 +260,17 @@ src_test_test_ntor_cl_LDADD = src/or/libtor.a src/common/libor.a \
 src_test_test_ntor_cl_AM_CPPFLAGS =	       \
 	-I"$(top_srcdir)/src/or"
 
+src_test_test_hs_ntor_cl_SOURCES  = src/test/test_hs_ntor_cl.c
+src_test_test_hs_ntor_cl_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@
+src_test_test_hs_ntor_cl_LDADD = src/or/libtor.a src/common/libor.a \
+	src/common/libor-ctime.a \
+	src/common/libor-crypto.a $(LIBKECCAK_TINY) $(LIBDONNA) \
+	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ \
+	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@
+src_test_test_hs_ntor_cl_AM_CPPFLAGS =	       \
+	-I"$(top_srcdir)/src/or"
+
+
 noinst_PROGRAMS += src/test/test-bt-cl
 src_test_test_bt_cl_SOURCES = src/test/test_bt_cl.c
 src_test_test_bt_cl_LDADD = src/common/libor-testing.a \
@@ -271,12 +283,13 @@ src_test_test_bt_cl_CPPFLAGS= $(src_test_AM_CPPFLAGS) $(TEST_CPPFLAGS)
 EXTRA_DIST += \
 	src/test/bt_test.py \
 	src/test/ntor_ref.py \
+	src/test/hs_ntor_ref.py \
 	src/test/fuzz_static_testcases.sh \
 	src/test/slownacl_curve25519.py \
 	src/test/zero_length_keys.sh \
 	src/test/test_keygen.sh \
 	src/test/test_zero_length_keys.sh \
-	src/test/test_ntor.sh src/test/test_bt.sh \
+	src/test/test_ntor.sh src/test/test_hs_ntor.sh src/test/test_bt.sh \
 	src/test/test-network.sh \
 	src/test/test_switch_id.sh \
 	src/test/test_workqueue_cancel.sh \

src/test/test_hs_ntor.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# Validate Tor's ntor implementation.
+
+exitcode=0
+
+# Run the python integration test sand return the exitcode of the python
+# script.  The python script might ask the testsuite to skip it if not all
+# python dependencies are covered.
+"${PYTHON:-python}" "${abs_top_srcdir:-.}/src/test/hs_ntor_ref.py" || exitcode=$?
+
+exit ${exitcode}

src/test/test_hs_ntor_cl.c

@@ -0,0 +1,255 @@
+/* Copyright (c) 2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/** This is a wrapper over the little-t-tor HS ntor functions. The wrapper is
+ *  used by src/test/hs_ntor_ref.py to conduct the HS ntor integration
+ *  tests.
+ *
+ *  The logic of this wrapper is basically copied from src/test/test_ntor_cl.c
+ */
+
+#include "orconfig.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#define ONION_NTOR_PRIVATE
+#include "or.h"
+#include "util.h"
+#include "compat.h"
+#include "crypto.h"
+#include "crypto_curve25519.h"
+#include "hs_ntor.h"
+#include "onion_ntor.h"
+
+#define N_ARGS(n) STMT_BEGIN {                                  \
+    if (argc < (n)) {                                           \
+      fprintf(stderr, "%s needs %d arguments.\n",argv[1],n);    \
+      return 1;                                                 \
+    }                                                           \
+  } STMT_END
+#define BASE16(idx, var, n) STMT_BEGIN {                                \
+    const char *s = argv[(idx)];                                        \
+    if (base16_decode((char*)var, n, s, strlen(s)) < (int)n ) {              \
+      fprintf(stderr, "couldn't decode argument %d (%s)\n",idx,s);      \
+      return 1;                                                         \
+    }                                                                   \
+  } STMT_END
+#define INT(idx, var) STMT_BEGIN {                                      \
+    var = atoi(argv[(idx)]);                                            \
+    if (var <= 0) {                                                     \
+      fprintf(stderr, "bad integer argument %d (%s)\n",idx,argv[(idx)]); \
+    }                                                                   \
+  } STMT_END
+
+/** The first part of the HS ntor protocol. The client-side computes all
+    necessary key material and sends the appropriate message to the service. */
+static int
+client1(int argc, char **argv)
+{
+  int retval;
+
+  /* Inputs */
+  curve25519_public_key_t intro_enc_pubkey;
+  ed25519_public_key_t intro_auth_pubkey;
+  curve25519_keypair_t client_ephemeral_enc_keypair;
+  uint8_t subcredential[DIGEST256_LEN];
+
+  /* Output */
+  hs_ntor_intro_cell_keys_t hs_ntor_intro_cell_keys;
+
+  char buf[256];
+
+  N_ARGS(6);
+  BASE16(2, intro_auth_pubkey.pubkey, ED25519_PUBKEY_LEN);
+  BASE16(3, intro_enc_pubkey.public_key, CURVE25519_PUBKEY_LEN);
+  BASE16(4, client_ephemeral_enc_keypair.seckey.secret_key,
+         CURVE25519_SECKEY_LEN);
+  BASE16(5, subcredential, DIGEST256_LEN);
+
+  /* Generate keypair */
+  curve25519_public_key_generate(&client_ephemeral_enc_keypair.pubkey,
+                                 &client_ephemeral_enc_keypair.seckey);
+
+  retval = hs_ntor_client_get_introduce1_keys(&intro_auth_pubkey,
+                                              &intro_enc_pubkey,
+                                              &client_ephemeral_enc_keypair,
+                                              subcredential,
+                                              &hs_ntor_intro_cell_keys);
+  if (retval < 0) {
+    goto done;
+  }
+
+  /* Send ENC_KEY */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_intro_cell_keys.enc_key,
+                sizeof(hs_ntor_intro_cell_keys.enc_key));
+  printf("%s\n", buf);
+  /* Send MAC_KEY */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_intro_cell_keys.mac_key,
+                sizeof(hs_ntor_intro_cell_keys.mac_key));
+  printf("%s\n", buf);
+
+ done:
+  return retval;
+}
+
+/** The second part of the HS ntor protocol. The service-side computes all
+    necessary key material and sends the appropriate message to the client */
+static int
+server1(int argc, char **argv)
+{
+  int retval;
+
+  /* Inputs */
+  curve25519_keypair_t intro_enc_keypair;
+  ed25519_public_key_t intro_auth_pubkey;
+  curve25519_public_key_t client_ephemeral_enc_pubkey;
+  uint8_t subcredential[DIGEST256_LEN];
+
+  /* Output */
+  hs_ntor_intro_cell_keys_t hs_ntor_intro_cell_keys;
+  hs_ntor_rend_cell_keys_t hs_ntor_rend_cell_keys;
+  curve25519_keypair_t service_ephemeral_rend_keypair;
+
+  char buf[256];
+
+  N_ARGS(6);
+  BASE16(2, intro_auth_pubkey.pubkey, ED25519_PUBKEY_LEN);
+  BASE16(3, intro_enc_keypair.seckey.secret_key, CURVE25519_SECKEY_LEN);
+  BASE16(4, client_ephemeral_enc_pubkey.public_key, CURVE25519_PUBKEY_LEN);
+  BASE16(5, subcredential, DIGEST256_LEN);
+
+  /* Generate keypair */
+  curve25519_public_key_generate(&intro_enc_keypair.pubkey,
+                                 &intro_enc_keypair.seckey);
+  curve25519_keypair_generate(&service_ephemeral_rend_keypair, 0);
+
+  /* Get INTRODUCE1 keys */
+  retval = hs_ntor_service_get_introduce1_keys(&intro_auth_pubkey,
+                                               &intro_enc_keypair,
+                                               &client_ephemeral_enc_pubkey,
+                                               subcredential,
+                                               &hs_ntor_intro_cell_keys);
+  if (retval < 0) {
+    goto done;
+  }
+
+  /* Get RENDEZVOUS1 keys */
+  retval = hs_ntor_service_get_rendezvous1_keys(&intro_auth_pubkey,
+                                               &intro_enc_keypair,
+                                               &service_ephemeral_rend_keypair,
+                                               &client_ephemeral_enc_pubkey,
+                                               &hs_ntor_rend_cell_keys);
+  if (retval < 0) {
+    goto done;
+  }
+
+  /* Send ENC_KEY */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_intro_cell_keys.enc_key,
+                sizeof(hs_ntor_intro_cell_keys.enc_key));
+  printf("%s\n", buf);
+  /* Send MAC_KEY */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_intro_cell_keys.mac_key,
+                sizeof(hs_ntor_intro_cell_keys.mac_key));
+  printf("%s\n", buf);
+  /* Send AUTH_MAC */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_rend_cell_keys.rend_cell_auth_mac,
+                sizeof(hs_ntor_rend_cell_keys.rend_cell_auth_mac));
+  printf("%s\n", buf);
+  /* Send NTOR_KEY_SEED */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_rend_cell_keys.ntor_key_seed,
+                sizeof(hs_ntor_rend_cell_keys.ntor_key_seed));
+  printf("%s\n", buf);
+  /* Send service ephemeral pubkey (Y) */
+  base16_encode(buf, sizeof(buf),
+                (const char*)service_ephemeral_rend_keypair.pubkey.public_key,
+                sizeof(service_ephemeral_rend_keypair.pubkey.public_key));
+  printf("%s\n", buf);
+
+ done:
+  return retval;
+}
+
+/** The final step of the ntor protocol, the client computes and returns the
+ *  rendezvous key material. */
+static int
+client2(int argc, char **argv)
+{
+  int retval;
+
+  /* Inputs */
+  curve25519_public_key_t intro_enc_pubkey;
+  ed25519_public_key_t intro_auth_pubkey;
+  curve25519_keypair_t client_ephemeral_enc_keypair;
+  curve25519_public_key_t service_ephemeral_rend_pubkey;
+  uint8_t subcredential[DIGEST256_LEN];
+
+  /* Output */
+  hs_ntor_rend_cell_keys_t hs_ntor_rend_cell_keys;
+
+  char buf[256];
+
+  N_ARGS(7);
+  BASE16(2, intro_auth_pubkey.pubkey, ED25519_PUBKEY_LEN);
+  BASE16(3, client_ephemeral_enc_keypair.seckey.secret_key,
+         CURVE25519_SECKEY_LEN);
+  BASE16(4, intro_enc_pubkey.public_key, CURVE25519_PUBKEY_LEN);
+  BASE16(5, service_ephemeral_rend_pubkey.public_key, CURVE25519_PUBKEY_LEN);
+  BASE16(6, subcredential, DIGEST256_LEN);
+
+  /* Generate keypair */
+  curve25519_public_key_generate(&client_ephemeral_enc_keypair.pubkey,
+                                 &client_ephemeral_enc_keypair.seckey);
+
+  /* Get RENDEZVOUS1 keys */
+  retval = hs_ntor_client_get_rendezvous1_keys(&intro_auth_pubkey,
+                                               &client_ephemeral_enc_keypair,
+                                               &intro_enc_pubkey,
+                                               &service_ephemeral_rend_pubkey,
+                                               &hs_ntor_rend_cell_keys);
+  if (retval < 0) {
+    goto done;
+  }
+
+  /* Send AUTH_MAC */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_rend_cell_keys.rend_cell_auth_mac,
+                sizeof(hs_ntor_rend_cell_keys.rend_cell_auth_mac));
+  printf("%s\n", buf);
+  /* Send NTOR_KEY_SEED */
+  base16_encode(buf, sizeof(buf),
+                (const char*)hs_ntor_rend_cell_keys.ntor_key_seed,
+                sizeof(hs_ntor_rend_cell_keys.ntor_key_seed));
+  printf("%s\n", buf);
+
+ done:
+  return 1;
+}
+
+/** Perform a different part of the protocol depdning on the argv used. */
+int
+main(int argc, char **argv)
+{
+  if (argc < 2) {
+    fprintf(stderr, "I need arguments. Read source for more info.\n");
+    return 1;
+  }
+
+  curve25519_init();
+  if (!strcmp(argv[1], "client1")) {
+    return client1(argc, argv);
+  } else if (!strcmp(argv[1], "server1")) {
+    return server1(argc, argv);
+  } else if (!strcmp(argv[1], "client2")) {
+    return client2(argc, argv);
+  } else {
+    fprintf(stderr, "What's a %s?\n", argv[1]);
+    return 1;
+  }
+}
+