Add reference implementation for ntor, plus compatibility test

Before I started coding ntor in C, I did another one in Python.
Turns out, they interoperate just fine.

src/test/test_ntor_cl.c

@@ -0,0 +1,166 @@
+/* Copyright (c) 2012, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#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 "onion_ntor.h"
+
+#ifndef CURVE25519_ENABLED
+#error "This isn't going to work without curve25519."
+#endif
+
+#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)) < 0 ) {              \
+      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
+
+static int
+client1(int argc, char **argv)
+{
+  /* client1 nodeID B -> msg state */
+  curve25519_public_key_t B;
+  uint8_t node_id[DIGEST_LEN];
+  ntor_handshake_state_t *state;
+  uint8_t msg[NTOR_ONIONSKIN_LEN];
+
+  char buf[1024];
+
+  memset(&state, 0, sizeof(state));
+
+  N_ARGS(4);
+  BASE16(2, node_id, DIGEST_LEN);
+  BASE16(3, B.public_key, CURVE25519_PUBKEY_LEN);
+
+  if (onion_skin_ntor_create(node_id, &B, &state, msg)<0) {
+    fprintf(stderr, "handshake failed");
+    return 2;
+  }
+
+  base16_encode(buf, sizeof(buf), (const char*)msg, sizeof(msg));
+  printf("%s\n", buf);
+  base16_encode(buf, sizeof(buf), (void*)state, sizeof(*state));
+  printf("%s\n", buf);
+  ntor_handshake_state_free(state);
+  return 0;
+}
+
+static int
+server1(int argc, char **argv)
+{
+  uint8_t msg_in[NTOR_ONIONSKIN_LEN];
+  curve25519_keypair_t kp;
+  di_digest256_map_t *keymap=NULL;
+  uint8_t node_id[DIGEST_LEN];
+  int keybytes;
+
+  uint8_t msg_out[NTOR_REPLY_LEN];
+  uint8_t *keys;
+  char *hexkeys;
+
+  char buf[256];
+
+  /* server1: b nodeID msg N -> msg keys */
+  N_ARGS(6);
+  BASE16(2, kp.seckey.secret_key, CURVE25519_SECKEY_LEN);
+  BASE16(3, node_id, DIGEST_LEN);
+  BASE16(4, msg_in, NTOR_ONIONSKIN_LEN);
+  INT(5, keybytes);
+
+  curve25519_public_key_generate(&kp.pubkey, &kp.seckey);
+  dimap_add_entry(&keymap, kp.pubkey.public_key, &kp);
+
+  keys = tor_malloc(keybytes);
+  hexkeys = tor_malloc(keybytes*2+1);
+  if (onion_skin_ntor_server_handshake(
+                                msg_in, keymap, NULL, node_id, msg_out, keys,
+                                (size_t)keybytes)<0) {
+    fprintf(stderr, "handshake failed");
+    return 2;
+  }
+
+  base16_encode(buf, sizeof(buf), (const char*)msg_out, sizeof(msg_out));
+  printf("%s\n", buf);
+  base16_encode(hexkeys, keybytes*2+1, (const char*)keys, keybytes);
+  printf("%s\n", hexkeys);
+
+  tor_free(keys);
+  tor_free(hexkeys);
+  return 0;
+}
+
+static int
+client2(int argc, char **argv)
+{
+  struct ntor_handshake_state_t state;
+  uint8_t msg[NTOR_REPLY_LEN];
+  int keybytes;
+  uint8_t *keys;
+  char *hexkeys;
+
+  N_ARGS(5);
+  BASE16(2, (&state), sizeof(state));
+  BASE16(3, msg, sizeof(msg));
+  INT(4, keybytes);
+
+  keys = tor_malloc(keybytes);
+  hexkeys = tor_malloc(keybytes*2+1);
+  if (onion_skin_ntor_client_handshake(&state, msg, keys, keybytes)<0) {
+    fprintf(stderr, "handshake failed");
+    return 2;
+  }
+
+  base16_encode(hexkeys, keybytes*2+1, (const char*)keys, keybytes);
+  printf("%s\n", hexkeys);
+
+  tor_free(keys);
+  tor_free(hexkeys);
+
+  return 0;
+}
+
+int
+main(int argc, char **argv)
+{
+  /*
+    client1: nodeID B -> msg state
+    server1: b nodeID msg N -> msg keys
+    client2: state msg N -> keys
+  */
+  if (argc < 2) {
+    fprintf(stderr, "I need arguments. Read source for more info.\n");
+    return 1;
+  } else 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;
+  }
+}
+