policies.c

关于tor匿名通信的源代码

  if (parse_addr_policy(options->AuthDirReject, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirReject entry.");
  if (parse_addr_policy(options->AuthDirInvalid, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirInvalid entry.");
  if (parse_addr_policy(options->AuthDirBadDir, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirBadDir entry.");
  if (parse_addr_policy(options->AuthDirBadExit, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirBadExit entry.");

  if (parse_addr_policy(options->ReachableAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableAddresses entry.");
  if (parse_addr_policy(options->ReachableORAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableORAddresses entry.");
  if (parse_addr_policy(options->ReachableDirAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableDirAddresses entry.");
  if (parse_addr_policy(options->AuthDirReject, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirReject entry.");
  if (parse_addr_policy(options->AuthDirInvalid, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirInvalid entry.");

err:
  addr_policy_list_free(addr_policy);
  return *msg ? -1 : 0;
#undef REJECT
}

/** Parse <b>string</b> in the same way that the exit policy
 * is parsed, and put the processed version in *<b>policy</b>.
 * Ignore port specifiers.
 */
static int
load_policy_from_option(config_line_t *config, smartlist_t **policy,
                        int assume_action)
{
  int r;
  addr_policy_list_free(*policy);
  *policy = NULL;
  r = parse_addr_policy(config, policy, assume_action);
  if (r < 0) {
    return -1;
  }
  if (*policy) {
    SMARTLIST_FOREACH(*policy, addr_policy_t *, n, {
        /* ports aren't used. */
        n->prt_min = 1;
        n->prt_max = 65535;
      });
  }
  return 0;
}

/** Set all policies based on <b>options</b>, which should have been validated
 * first by validate_addr_policies. */
int
policies_parse_from_options(or_options_t *options)
{
  int ret = 0;
  if (load_policy_from_option(options->SocksPolicy, &socks_policy, -1) < 0)
    ret = -1;
  if (load_policy_from_option(options->DirPolicy, &dir_policy, -1) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirReject,
                              &authdir_reject_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirInvalid,
                              &authdir_invalid_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirBadDir,
                              &authdir_baddir_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirBadExit,
                              &authdir_badexit_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (parse_reachable_addresses() < 0)
    ret = -1;
  return ret;
}

/** Compare two provided address policy items, and return -1, 0, or 1
 * if the first is less than, equal to, or greater than the second. */
static int
cmp_single_addr_policy(addr_policy_t *a, addr_policy_t *b)
{
  int r;
  if ((r=((int)a->policy_type - (int)b->policy_type)))
    return r;
  if ((r=((int)a->is_private - (int)b->is_private)))
    return r;
  if ((r=((int)a->addr - (int)b->addr)))
    return r;
  if ((r=((int)a->maskbits - (int)b->maskbits)))
    return r;
  if ((r=((int)a->prt_min - (int)b->prt_min)))
    return r;
  if ((r=((int)a->prt_max - (int)b->prt_max)))
    return r;
  return 0;
}

/** Like cmp_single_addr_policy() above, but looks at the
 * whole set of policies in each case. */
int
cmp_addr_policies(smartlist_t *a, smartlist_t *b)
{
  int r, i;
  int len_a = a ? smartlist_len(a) : 0;
  int len_b = b ? smartlist_len(b) : 0;

  for (i = 0; i < len_a && i < len_b; ++i) {
    if ((r = cmp_single_addr_policy(smartlist_get(a, i), smartlist_get(b, i))))
      return r;
  }
  if (i == len_a && i == len_b)
    return 0;
  if (i < len_a)
    return -1;
  else
    return 1;
}

/** Node in hashtable used to store address policy entries. */
typedef struct policy_map_ent_t {
  HT_ENTRY(policy_map_ent_t) node;
  addr_policy_t *policy;
} policy_map_ent_t;

static HT_HEAD(policy_map, policy_map_ent_t) policy_root = HT_INITIALIZER();

/** Return true iff a and b are equal. */
static INLINE int
policy_eq(policy_map_ent_t *a, policy_map_ent_t *b)
{
  return cmp_single_addr_policy(a->policy, b->policy) == 0;
}

/** Return a hashcode for <b>ent</b> */
static unsigned int
policy_hash(policy_map_ent_t *ent)
{
  addr_policy_t *a = ent->policy;
  unsigned int r;
  if (a->is_private)
    r = 0x1234abcd;
  else
    r = (unsigned int)a->addr;
  r += a->prt_min << 8;
  r += a->prt_max << 16;
  r += a->maskbits;
  if (a->policy_type == ADDR_POLICY_REJECT)
    r ^= 0xffffffff;

  return r;
}

HT_PROTOTYPE(policy_map, policy_map_ent_t, node, policy_hash,
             policy_eq)
HT_GENERATE(policy_map, policy_map_ent_t, node, policy_hash,
            policy_eq, 0.6, malloc, realloc, free)

/** Given a pointer to an addr_policy_t, return a copy of the pointer to the
 * "canonical" copy of that addr_policy_t; the canonical copy is a single
 * reference-counted object. */
addr_policy_t *
addr_policy_get_canonical_entry(addr_policy_t *e)
{
  policy_map_ent_t search, *found;
  if (e->is_canonical)
    return e;

  search.policy = e;
  found = HT_FIND(policy_map, &policy_root, &search);
  if (!found) {
    found = tor_malloc_zero(sizeof(policy_map_ent_t));
    found->policy = tor_memdup(e, sizeof(addr_policy_t));
    found->policy->is_canonical = 1;
    found->policy->refcnt = 0;
    HT_INSERT(policy_map, &policy_root, found);
  }

  tor_assert(!cmp_single_addr_policy(found->policy, e));
  ++found->policy->refcnt;
  return found->policy;
}

/** Decide whether a given addr:port is definitely accepted,
 * definitely rejected, probably accepted, or probably rejected by a
 * given policy.  If <b>addr</b> is 0, we don't know the IP of the
 * target address. If <b>port</b> is 0, we don't know the port of the
 * target address.
 *
 * For now, the algorithm is pretty simple: we look for definite and
 * uncertain matches.  The first definite match is what we guess; if
 * it was preceded by no uncertain matches of the opposite policy,
 * then the guess is definite; otherwise it is probable.  (If we
 * have a known addr and port, all matches are definite; if we have an
 * unknown addr/port, any address/port ranges other than "all" are
 * uncertain.)
 *
 * We could do better by assuming that some ranges never match typical
 * addresses (127.0.0.1, and so on).  But we'll try this for now.
 */
addr_policy_result_t
compare_addr_to_addr_policy(uint32_t addr, uint16_t port,
                            smartlist_t *policy)
{
  int maybe_reject = 0;
  int maybe_accept = 0;
  int match = 0;
  int maybe = 0;
  int i, len;

  len = policy ? smartlist_len(policy) : 0;

  for (i = 0; i < len; ++i) {
    addr_policy_t *tmpe = smartlist_get(policy, i);
    maybe = 0;
    if (!addr) {
      /* Address is unknown. */
      if ((port >= tmpe->prt_min && port <= tmpe->prt_max) ||
           (!port && tmpe->prt_min<=1 && tmpe->prt_max>=65535)) {
        /* The port definitely matches. */
        if (tmpe->maskbits == 0) {
          match = 1;
        } else {
          maybe = 1;
        }
      } else if (!port) {
        /* The port maybe matches. */
        maybe = 1;
      }
    } else {
      /* Address is known */
      if (!addr_mask_cmp_bits(addr, tmpe->addr, tmpe->maskbits)) {
        if (port >= tmpe->prt_min && port <= tmpe->prt_max) {
          /* Exact match for the policy */
          match = 1;
        } else if (!port) {
          maybe = 1;
        }
      }
    }
    if (maybe) {
      if (tmpe->policy_type == ADDR_POLICY_REJECT)
        maybe_reject = 1;
      else
        maybe_accept = 1;
    }
    if (match) {
      if (tmpe->policy_type == ADDR_POLICY_ACCEPT) {
        /* If we already hit a clause that might trigger a 'reject', than we
         * can't be sure of this certain 'accept'.*/
        return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED :
                              ADDR_POLICY_ACCEPTED;
      } else {
        return maybe_accept ? ADDR_POLICY_PROBABLY_REJECTED :
                              ADDR_POLICY_REJECTED;
      }
    }
  }

  /* accept all by default. */
  return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED : ADDR_POLICY_ACCEPTED;
}

/** Return true iff the address policy <b>a</b> covers every case that
 * would be covered by <b>b</b>, so that a,b is redundant. */
static int
addr_policy_covers(addr_policy_t *a, addr_policy_t *b)
{
  /* We can ignore accept/reject, since "accept *:80, reject *:80" reduces
   * to "accept *:80". */
  if (a->maskbits > b->maskbits) {
    /* a has more fixed bits than b; it can't possibly cover b. */
    return 0;
  }
  if (addr_mask_cmp_bits(a->addr, b->addr, a->maskbits)) {
    /* There's a fixed bit in a that's set differently in b. */
    return 0;
  }
  return (a->prt_min <= b->prt_min && a->prt_max >= b->prt_max);
}

/** Return true iff the address policies <b>a</b> and <b>b</b> intersect,
 * that is, there exists an address/port that is covered by <b>a</b> that
 * is also covered by <b>b</b>.
 */
static int
addr_policy_intersects(addr_policy_t *a, addr_policy_t *b)
{
  maskbits_t minbits;
  /* All the bits we care about are those that are set in both
   * netmasks.  If they are equal in a and b's networkaddresses
   * then the networks intersect.  If there is a difference,
   * then they do not. */
  if (a->maskbits < b->maskbits)
    minbits = a->maskbits;
  else
    minbits = b->maskbits;
  if (addr_mask_cmp_bits(a->addr, b->addr, minbits))
    return 0;
  if (a->prt_max < b->prt_min || b->prt_max < a->prt_min)
    return 0;
  return 1;
}