routerparse.c

关于tor匿名通信的源代码

  if (router_get_runningrouters_hash(str, digest)) {
    log_warn(LD_DIR, "Unable to compute digest of running-routers");
    goto err;
  }
  area = memarea_new(8192);
  tokens = smartlist_create();
  if (tokenize_string(area,str,eos,tokens,dir_token_table,0)) {
    log_warn(LD_DIR, "Error tokenizing running-routers"); goto err;
  }
  tok = smartlist_get(tokens,0);
  if (tok->tp != K_NETWORK_STATUS) {
    log_warn(LD_DIR, "Network-status starts with wrong token");
    goto err;
  }

  tok = find_first_by_keyword(tokens, K_PUBLISHED);
  tor_assert(tok);
  tor_assert(tok->n_args == 1);
  if (parse_iso_time(tok->args[0], &published_on) < 0) {
     goto err;
  }
  if (!(tok = find_first_by_keyword(tokens, K_DIRECTORY_SIGNATURE))) {
    log_warn(LD_DIR, "Missing signature on running-routers");
    goto err;
  }
  declared_key = find_dir_signing_key(str, eos);
  note_crypto_pk_op(VERIFY_DIR);
  if (check_signature_token(digest, tok, declared_key, 1, "running-routers")
      < 0)
    goto err;

  /* Now that we know the signature is okay, and we have a
   * publication time, cache the list. */
  if (get_options()->DirPort && !authdir_mode_v1(get_options()))
    dirserv_set_cached_directory(str, published_on, 1);

  r = 0;
 err:
  if (declared_key) crypto_free_pk_env(declared_key);
  if (tokens) {
    SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_free(t));
    smartlist_free(tokens);
  }
  if (area) {
    DUMP_AREA(area, "v1 running-routers");
    memarea_drop_all(area);
  }
  return r;
}

/** Given a directory or running-routers string in <b>str</b>, try to
 * find the its dir-signing-key token (if any).  If this token is
 * present, extract and return the key.  Return NULL on failure. */
static crypto_pk_env_t *
find_dir_signing_key(const char *str, const char *eos)
{
  const char *cp;
  directory_token_t *tok;
  crypto_pk_env_t *key = NULL;
  memarea_t *area = NULL;
  tor_assert(str);
  tor_assert(eos);

  /* Is there a dir-signing-key in the directory? */
  cp = tor_memstr(str, eos-str, "\nopt dir-signing-key");
  if (!cp)
    cp = tor_memstr(str, eos-str, "\ndir-signing-key");
  if (!cp)
    return NULL;
  ++cp; /* Now cp points to the start of the token. */

  area = memarea_new(1024);
  tok = get_next_token(area, &cp, eos, dir_token_table);
  if (!tok) {
    log_warn(LD_DIR, "Unparseable dir-signing-key token");
    goto done;
  }
  if (tok->tp != K_DIR_SIGNING_KEY) {
    log_warn(LD_DIR, "Dir-signing-key token did not parse as expected");
    goto done;
  }

  if (tok->key) {
    key = tok->key;
    tok->key = NULL; /* steal reference. */
  } else {
    log_warn(LD_DIR, "Dir-signing-key token contained no key");
  }

 done:
  if (tok) token_free(tok);
  if (area) {
    DUMP_AREA(area, "dir-signing-key token");
    memarea_drop_all(area);
  }
  return key;
}

/** Return true iff <b>key</b> is allowed to sign directories.
 */
static int
dir_signing_key_is_trusted(crypto_pk_env_t *key)
{
  char digest[DIGEST_LEN];
  if (!key) return 0;
  if (crypto_pk_get_digest(key, digest) < 0) {
    log_warn(LD_DIR, "Error computing dir-signing-key digest");
    return 0;
  }
  if (!router_digest_is_trusted_dir(digest)) {
    log_warn(LD_DIR, "Listed dir-signing-key is not trusted");
    return 0;
  }
  return 1;
}

/** Check whether the object body of the token in <b>tok</b> has a good
 * signature for <b>digest</b> using key <b>pkey</b>.  If
 * <b>check_authority</b> is set, make sure that <b>pkey</b> is the key of a
 * directory authority.  Use <b>doctype</b> as the type of the document when
 * generating log messages.  Return 0 on success, negative on failure.
 */
static int
check_signature_token(const char *digest,
                      directory_token_t *tok,
                      crypto_pk_env_t *pkey,
                      int check_authority,
                      const char *doctype)
{
  char *signed_digest;

  tor_assert(pkey);
  tor_assert(tok);
  tor_assert(digest);
  tor_assert(doctype);

  if (check_authority && !dir_signing_key_is_trusted(pkey)) {
    log_warn(LD_DIR, "Key on %s did not come from an authority; rejecting",
             doctype);
    return -1;
  }

  if (strcmp(tok->object_type, "SIGNATURE")) {
    log_warn(LD_DIR, "Bad object type on %s signature", doctype);
    return -1;
  }

  signed_digest = tor_malloc(tok->object_size);
  if (crypto_pk_public_checksig(pkey, signed_digest, tok->object_body,
                                tok->object_size)
      != DIGEST_LEN) {
    log_warn(LD_DIR, "Error reading %s: invalid signature.", doctype);
    tor_free(signed_digest);
    return -1;
  }
//  log_debug(LD_DIR,"Signed %s hash starts %s", doctype,
//            hex_str(signed_digest,4));
  if (memcmp(digest, signed_digest, DIGEST_LEN)) {
    log_warn(LD_DIR, "Error reading %s: signature does not match.", doctype);
    tor_free(signed_digest);
    return -1;
  }
  tor_free(signed_digest);
  return 0;
}

/** Helper: move *<b>s_ptr</b> ahead to the next router, the next extra-info,
 * or to the first of the annotations proceeding the next router or
 * extra-info---whichever comes first.  Set <b>is_extrainfo_out</b> to true if
 * we found an extrainfo, or false if found a router. Do not scan beyond
 * <b>eos</b>.  Return -1 if we found nothing; 0 if we found something. */
static int
find_start_of_next_router_or_extrainfo(const char **s_ptr,
                                       const char *eos,
                                       int *is_extrainfo_out)
{
  const char *annotations = NULL;
  const char *s = *s_ptr;

  s = eat_whitespace_eos(s, eos);

  while (s < eos-32) {  /* 32 gives enough room for a the first keyword. */
    /* We're at the start of a line. */
    tor_assert(*s != '\n');

    if (*s == '@' && !annotations) {
      annotations = s;
    } else if (*s == 'r' && !strcmpstart(s, "router ")) {
      *s_ptr = annotations ? annotations : s;
      *is_extrainfo_out = 0;
      return 0;
    } else if (*s == 'e' && !strcmpstart(s, "extra-info ")) {
      *s_ptr = annotations ? annotations : s;
      *is_extrainfo_out = 1;
      return 0;
    }

    if (!(s = memchr(s+1, '\n', eos-(s+1))))
      break;
    s = eat_whitespace_eos(s, eos);
  }
  return -1;
}

/** Given a string *<b>s</b> containing a concatenated sequence of router
 * descriptors (or extra-info documents if <b>is_extrainfo</b> is set), parses
 * them and stores the result in <b>dest</b>.  All routers are marked running
 * and valid.  Advances *s to a point immediately following the last router
 * entry.  Ignore any trailing router entries that are not complete.
 *
 * If <b>saved_location</b> isn't SAVED_IN_CACHE, make a local copy of each
 * descriptor in the signed_descriptor_body field of each routerinfo_t.  If it
 * isn't SAVED_NOWHERE, remember the offset of each descriptor.
 *
 * Returns 0 on success and -1 on failure.
 */
int
router_parse_list_from_string(const char **s, const char *eos,
                              smartlist_t *dest,
                              saved_location_t saved_location,
                              int want_extrainfo,
                              int allow_annotations,
                              const char *prepend_annotations)
{
  routerinfo_t *router;
  extrainfo_t *extrainfo;
  signed_descriptor_t *signed_desc;
  void *elt;
  const char *end, *start;
  int have_extrainfo;

  tor_assert(s);
  tor_assert(*s);
  tor_assert(dest);

  start = *s;
  if (!eos)
    eos = *s + strlen(*s);

  tor_assert(eos >= *s);

  while (1) {
    if (find_start_of_next_router_or_extrainfo(s, eos, &have_extrainfo) < 0)
      break;

    end = tor_memstr(*s, eos-*s, "\nrouter-signature");
    if (end)
      end = tor_memstr(end, eos-end, "\n-----END SIGNATURE-----\n");
    if (end)
      end += strlen("\n-----END SIGNATURE-----\n");

    if (!end)
      break;

    elt = NULL;

    if (have_extrainfo && want_extrainfo) {
      routerlist_t *rl = router_get_routerlist();
      extrainfo = extrainfo_parse_entry_from_string(*s, end,
                                       saved_location != SAVED_IN_CACHE,
                                       rl->identity_map);
      if (extrainfo) {
        signed_desc = &extrainfo->cache_info;
        elt = extrainfo;
      }
    } else if (!have_extrainfo && !want_extrainfo) {
      router = router_parse_entry_from_string(*s, end,
                                              saved_location != SAVED_IN_CACHE,
                                              allow_annotations,
                                              prepend_annotations);
      if (router) {
        log_debug(LD_DIR, "Read router '%s', purpose '%s'",
                  router->nickname, router_purpose_to_string(router->purpose));
        signed_desc = &router->cache_info;
        elt = router;
      }
    }
    if (!elt) {
      *s = end;
      continue;
    }
    if (saved_location != SAVED_NOWHERE) {
      signed_desc->saved_location = saved_location;
      signed_desc->saved_offset = *s - start;
    }
    *s = end;
    smartlist_add(dest, elt);
  }

  return 0;
}

/* For debugging: define to count every descriptor digest we've seen so we
 * know if we need to try harder to avoid duplicate verifies. */
#undef COUNT_DISTINCT_DIGESTS

#ifdef COUNT_DISTINCT_DIGESTS
static digestmap_t *verified_digests = NULL;
#endif

/** Log the total count of the number of distinct router digests we've ever
 * verified.  When compared to the number of times we've verified routerdesc
 * signatures <i>in toto</i>, this will tell us if we're doing too much
 * multiple-verification. */
void
dump_distinct_digest_count(int severity)
{
#ifdef COUNT_DISTINCT_DIGESTS
  if (!verified_digests)
    verified_digests = digestmap_new();
  log(severity, LD_GENERAL, "%d *distinct* router digests verified",
      digestmap_size(verified_digests));
#else
  (void)severity; /* suppress "unused parameter" warning */
#endif
}

/** Helper function: reads a single router entry from *<b>s</b> ...
 * *<b>end</b>.  Mallocs a new router and returns it if all goes well, else
 * returns NULL.  If <b>cache_copy</b> is true, duplicate the contents of
 * s through end into the signed_descriptor_body of the resulting
 * routerinfo_t.
 *
 * If <b>allow_annotations</b>, it's okay to encounter annotations in <b>s</b>
 * before the router; if it's false, reject the router if it's annotated.  If
 * <b>prepend_annotations</b> is set, it should contain some annotations:
 * append them to the front of the router before parsing it, and keep them
 * around when caching the router.
 *
 * Only one of allow_annotations and prepend_annotations may be set.
 */
routerinfo_t *
router_parse_entry_from_string(const char *s, const char *end,
                               int cache_copy, int allow_annotations,
                               const char *prepend_annotations)
{
  routerinfo_t *router = NULL;
  char digest[128];
  smartlist_t *tokens = NULL, *exit_policy_tokens = NULL;
  directory_token_t *tok;
  struct in_addr in;
  const char *start_of_annotations, *cp;
  size_t prepend_len = prepend_annotations ? strlen(prepend_annotations) : 0;
  int ok = 1;
  memarea_t *area = NULL;

  tor_assert(!allow_annotations || !prepend_annotations);

  if (!end) {
    end = s + strlen(s);
  }

  /* point 'end' to a point immediately after the final newline. */
  while (end > s+2 && *(end-1) == '\n' && *(end-2) == '\n')
    --end;

  area = memarea_new(4096);
  tokens = smartlist_create();
  if (prepend_annotations) {
    if (tokenize_string(area,prepend_annotations,NULL,tokens,
                        routerdesc_token_table,TS_NOCHECK)) {
      log_warn(LD_DIR, "Error tokenizing router descriptor (annotations).");
      goto err;
    }
  }

  start_of_annotations = s;
  cp = tor_memstr(s, end-s, "\nrouter ");
  if (!cp) {
    if (end-s < 7 || strcmpstart(s, "router ")) {
      log_warn(LD_DIR, "No router keyword found.");
      goto err;
    }
  } else {
    s = cp+1;
  }