commit 408c53b7a78767e04124fec4c4d470fe474e4906 Author: teor teor2345@gmail.com Date: Wed Feb 1 15:31:33 2017 +1100
Scale IPv6 address counts in policy_summary_reject to avoid overflow
This disregards anything smaller than an IPv6 /64, and rejects ports that are rejected on an IPv6 /16 or larger.
Adjust existing unit tests, and add more to cover exceptional cases.
No IPv4 behaviour changes.
Fixes bug 21357 --- src/or/policies.c | 35 +++++++++++++++++++++++++++++------ src/test/test_policy.c | 42 ++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 69 insertions(+), 8 deletions(-)
diff --git a/src/or/policies.c b/src/or/policies.c index cac475d..6037ee3 100644 --- a/src/or/policies.c +++ b/src/or/policies.c @@ -2300,15 +2300,24 @@ policy_summary_item_split(policy_summary_item_t* old, uint16_t new_starts) #define AT(x) ((policy_summary_item_t*)smartlist_get(summary, x))
#define IPV4_BITS (32) +/* Every IPv4 address is counted as one rejection */ +#define REJECT_CUTOFF_SCALE_IPV4 (0) /* Ports are rejected in an IPv4 summary if they are rejected in more than two * IPv4 /8 address blocks */ #define REJECT_CUTOFF_COUNT_IPV4 (U64_LITERAL(1) << \ - (IPV4_BITS - 7)) + (IPV4_BITS - REJECT_CUTOFF_SCALE_IPV4 - 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) +/* IPv6 /64s are counted as one rejection, anything smaller is ignored */ +#define REJECT_CUTOFF_SCALE_IPV6 (64) +/* Ports are rejected in an IPv6 summary if they are rejected in more than one + * IPv6 /16 address block. + * This is rougly equivalent to the IPv4 cutoff, as only five IPv6 /12s (and + * some scattered smaller blocks) have been allocated to the RIRs. + * Network providers are typically allocated one or more IPv6 /32s. + */ +#define REJECT_CUTOFF_COUNT_IPV6 (U64_LITERAL(1) << \ + (IPV6_BITS - REJECT_CUTOFF_SCALE_IPV6 - 16))
/** Split an exit policy summary so that prt_min and prt_max * fall at exactly the start and end of an item respectively. @@ -2381,14 +2390,28 @@ policy_summary_reject(smartlist_t *summary, int addrbits = (family == AF_INET) ? IPV4_BITS : IPV6_BITS; tor_assert_nonfatal_once(addrbits >= maskbits);
+ /* We divide IPv6 address counts by (1 << scale) to keep them in a uint64_t + */ + int scale = ((family == AF_INET) ? + REJECT_CUTOFF_SCALE_IPV4 : + REJECT_CUTOFF_SCALE_IPV6); + + tor_assert_nonfatal_once(addrbits >= scale); + if (maskbits > (addrbits - scale)) { + tor_assert_nonfatal_once(family == AF_INET6); + /* The address range is so small, we'd need billions of them to reach the + * rejection limit. So we ignore this range in the reject count. */ + return; + } + uint64_t count = 0; - if (addrbits - maskbits >= 64) { + if (addrbits - scale - 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)); + count = (U64_LITERAL(1) << (addrbits - scale - maskbits)); } tor_assert_nonfatal_once(count > 0); while (i < smartlist_len(summary) && diff --git a/src/test/test_policy.c b/src/test/test_policy.c index fb7195a..f2d42b9 100644 --- a/src/test/test_policy.c +++ b/src/test/test_policy.c @@ -594,13 +594,51 @@ test_policies_general(void *arg) /* short policy with configured netblocks */ test_policy_summary_helper("reject 149.56.0.0/16," "reject6 2607:5300::/32," + "reject6 2608:5300::/64," + "reject6 2609:5300::/96," + "accept *:80," + "accept *:443," + "reject *:*", + "accept 80,443"); + /* short policy with large netblocks that do not count as a rejection */ + test_policy_summary_helper("reject 148.0.0.0/7," + "reject6 2600::/16," "accept *:80," "accept *:443," "reject *:*", "accept 80,443"); /* short policy with large netblocks that count as a rejection */ - test_policy_summary_helper("reject 149.0.0.0/6," - "reject6 2600::/6," + test_policy_summary_helper("reject 148.0.0.0/6," + "reject6 2600::/15," + "accept *:80," + "accept *:443," + "reject *:*", + "reject 1-65535"); + /* short policy with huge netblocks that count as a rejection */ + test_policy_summary_helper("reject 128.0.0.0/1," + "reject6 8000::/1," + "accept *:80," + "accept *:443," + "reject *:*", + "reject 1-65535"); + /* short policy which blocks everything using netblocks */ + test_policy_summary_helper("reject 0.0.0.0/0," + "reject6 ::/0," + "accept *:80," + "accept *:443," + "reject *:*", + "reject 1-65535"); + /* short policy which has repeated redundant netblocks */ + test_policy_summary_helper("reject 0.0.0.0/0," + "reject 0.0.0.0/0," + "reject 0.0.0.0/0," + "reject 0.0.0.0/0," + "reject 0.0.0.0/0," + "reject6 ::/0," + "reject6 ::/0," + "reject6 ::/0," + "reject6 ::/0," + "reject6 ::/0," "accept *:80," "accept *:443," "reject *:*",