Commit 4667a40c authored by teor's avatar teor Committed by Nick Mathewson
Browse files

Fix IPv6 support in policy_summary_reject and policy_summary_accept 

This interim fix results in too many IPv6 rejections.

No behaviour change for IPv4 counts, except for overflow fixes that
would require 4 billion redundant 0.0.0.0/0 policy entries to trigger.

Part of 21357
parent 82850d0d

src/or/policies.c

+47 −13
Original line number Diff line number Diff line
@@ -2304,6 +2304,12 @@ policy_summary_item_split(policy_summary_item_t* old, uint16_t new_starts) 
 * IPv4 /8 address blocks */

#define REJECT_CUTOFF_COUNT_IPV4 (U64_LITERAL(1) << \

                                  (IPV4_BITS - 7))



#define IPV6_BITS                (128)

/* Ports are rejected in an IPv6 summary if they are rejected in at least one

 * IPv6 /64. */

#define REJECT_CUTOFF_COUNT_IPV6 (UINT64_MAX)



/** Split an exit policy summary so that prt_min and prt_max

 * fall at exactly the start and end of an item respectively.

 */
@@ -2336,40 +2342,68 @@ policy_summary_split(smartlist_t *summary, 
  return start_at_index;

}



/** Mark port ranges as accepted if they are below the reject_count */

/** Mark port ranges as accepted if they are below the reject_count for family

 */

static void

policy_summary_accept(smartlist_t *summary,

                      uint16_t prt_min, uint16_t prt_max)

                      uint16_t prt_min, uint16_t prt_max,

                      sa_family_t family)

{

  tor_assert_nonfatal_once(family == AF_INET || family == AF_INET6);

  uint64_t family_reject_count = ((family == AF_INET) ?

                                  REJECT_CUTOFF_COUNT_IPV4 :

                                  REJECT_CUTOFF_COUNT_IPV6);



  int i = policy_summary_split(summary, prt_min, prt_max);

  while (i < smartlist_len(summary) &&

         AT(i)->prt_max <= prt_max) {

    if (!AT(i)->accepted &&

        AT(i)->reject_count <= REJECT_CUTOFF_COUNT_IPV4)

        AT(i)->reject_count <= family_reject_count)

      AT(i)->accepted = 1;

    i++;

  }

  tor_assert(i < smartlist_len(summary) || prt_max==65535);

}



/** Count the number of addresses in a network with prefixlen maskbits

 * against the given portrange. */

/** Count the number of addresses in a network in family with prefixlen

 * maskbits against the given portrange. */

static void

policy_summary_reject(smartlist_t *summary,

                      maskbits_t maskbits,

                      uint16_t prt_min, uint16_t prt_max)

                      uint16_t prt_min, uint16_t prt_max,

                      sa_family_t family)

{

  tor_assert_nonfatal_once(family == AF_INET || family == AF_INET6);



  int i = policy_summary_split(summary, prt_min, prt_max);

  /* XXX: ipv4 specific */



  /* The length of a single address mask */

  int addrbits = IPV4_BITS;

  int addrbits = (family == AF_INET) ? IPV4_BITS : IPV6_BITS;

  tor_assert_nonfatal_once(addrbits >= maskbits);



  uint64_t count = (U64_LITERAL(1) << (addrbits-maskbits));

  uint64_t count = 0;

  if (addrbits - maskbits >= 64) {

    tor_assert_nonfatal_once(family == AF_INET6);

    /* The address range is so large, it's an automatic rejection for all ports

     * in the range. */

    count = UINT64_MAX;

  } else {

    count = (U64_LITERAL(1) << (addrbits - maskbits));

  }

  tor_assert_nonfatal_once(count > 0);

  while (i < smartlist_len(summary) &&

         AT(i)->prt_max <= prt_max) {

    if (AT(i)->reject_count <= UINT64_MAX - count) {

      AT(i)->reject_count += count;

    } else {

      /* IPv4 would require a 4-billion address redundant policy to get here,

       * but IPv6 just needs to have ::/0 */

      if (family == AF_INET) {

        tor_assert_nonfatal_unreached_once();

      }

      /* If we do get here, use saturating arithmetic */

      AT(i)->reject_count = UINT64_MAX;

    }

    i++;

  }

  tor_assert(i < smartlist_len(summary) || prt_max==65535);
@@ -2389,7 +2423,7 @@ policy_summary_add_item(smartlist_t *summary, addr_policy_t *p) 
{

  if (p->policy_type == ADDR_POLICY_ACCEPT) {

    if (p->maskbits == 0) {

      policy_summary_accept(summary, p->prt_min, p->prt_max);

      policy_summary_accept(summary, p->prt_min, p->prt_max, p->addr.family);

    }

  } else if (p->policy_type == ADDR_POLICY_REJECT) {
@@ -2410,7 +2444,8 @@ policy_summary_add_item(smartlist_t *summary, addr_policy_t *p) 
     }



     if (!is_private) {

       policy_summary_reject(summary, p->maskbits, p->prt_min, p->prt_max);

       policy_summary_reject(summary, p->maskbits, p->prt_min, p->prt_max,

                             p->addr.family);

     }

  } else

    tor_assert(0);
@@ -2444,7 +2479,6 @@ policy_summarize(smartlist_t *policy, sa_family_t family) 
    }

    if (f != family)

      continue;

    /* XXXX-ipv6 More family work is needed */

    policy_summary_add_item(summary, p);

  } SMARTLIST_FOREACH_END(p);