/* * ntp_restrict.c - determine host restrictions */ #ifdef HAVE_CONFIG_H #include #endif #include #include #include "ntpd.h" #include "ntp_if.h" #include "ntp_lists.h" #include "ntp_stdlib.h" #include "ntp_assert.h" /* * This code keeps a simple address-and-mask list of hosts we want * to place restrictions on (or remove them from). The restrictions * are implemented as a set of flags which tell you what the host * can't do. There is a subroutine entry to return the flags. The * list is kept sorted to reduce the average number of comparisons * and make sure you get the set of restrictions most specific to * the address. * * The algorithm is that, when looking up a host, it is first assumed * that the default set of restrictions will apply. It then searches * down through the list. Whenever it finds a match it adopts the * match's flags instead. When you hit the point where the sorted * address is greater than the target, you return with the last set of * flags you found. Because of the ordering of the list, the most * specific match will provide the final set of flags. * * This was originally intended to restrict you from sync'ing to your * own broadcasts when you are doing that, by restricting yourself from * your own interfaces. It was also thought it would sometimes be useful * to keep a misbehaving host or two from abusing your primary clock. It * has been expanded, however, to suit the needs of those with more * restrictive access policies. */ /* * We will use two lists, one for IPv4 addresses and one for IPv6 * addresses. This is not protocol-independant but for now I can't * find a way to respect this. We'll check this later... JFB 07/2001 */ #define MASK_IPV6_ADDR(dst, src, msk) \ do { \ int idx; \ for (idx = 0; idx < (int)COUNTOF((dst)->s6_addr); idx++) { \ (dst)->s6_addr[idx] = (src)->s6_addr[idx] \ & (msk)->s6_addr[idx]; \ } \ } while (0) /* * We allocate INC_RESLIST{4|6} entries to the free list whenever empty. * Auto-tune these to be just less than 1KB (leaving at least 16 bytes * for allocator overhead). */ #define INC_RESLIST4 ((1024 - 16) / V4_SIZEOF_RESTRICT_U) #define INC_RESLIST6 ((1024 - 16) / V6_SIZEOF_RESTRICT_U) /* * The restriction list */ restrict_u *restrictlist4; restrict_u *restrictlist6; static int restrictcount; /* count in the restrict lists */ /* * The free list and associated counters. Also some uninteresting * stat counters. */ static restrict_u *resfree4; /* available entries (free list) */ static restrict_u *resfree6; static u_long res_calls; static u_long res_found; static u_long res_not_found; /* * Count number of restriction entries referring to RES_LIMITED, to * control implicit activation/deactivation of the MRU monlist. */ static u_long res_limited_refcnt; /* * Our default entries. */ static restrict_u restrict_def4; static restrict_u restrict_def6; /* * "restrict source ..." enabled knob and restriction bits. */ static int restrict_source_enabled; static u_short restrict_source_flags; static u_short restrict_source_mflags; /* * private functions */ static restrict_u * alloc_res4(void); static restrict_u * alloc_res6(void); static void free_res(restrict_u *, int); static void inc_res_limited(void); static void dec_res_limited(void); static restrict_u * match_restrict4_addr(u_int32, u_short); static restrict_u * match_restrict6_addr(const struct in6_addr *, u_short); static restrict_u * match_restrict_entry(const restrict_u *, int); static int res_sorts_before4(restrict_u *, restrict_u *); static int res_sorts_before6(restrict_u *, restrict_u *); /* * init_restrict - initialize the restriction data structures */ void init_restrict(void) { /* * The restriction lists begin with a default entry with address * and mask 0, which will match any entry. The lists are kept * sorted by descending address followed by descending mask: * * address mask * 192.168.0.0 255.255.255.0 kod limited noquery nopeer * 192.168.0.0 255.255.0.0 kod limited * 0.0.0.0 0.0.0.0 kod limited noquery * * The first entry which matches an address is used. With the * example restrictions above, 192.168.0.0/24 matches the first * entry, the rest of 192.168.0.0/16 matches the second, and * everything else matches the third (default). * * Note this achieves the same result a little more efficiently * than the documented behavior, which is to keep the lists * sorted by ascending address followed by ascending mask, with * the _last_ matching entry used. * * An additional wrinkle is we may have multiple entries with * the same address and mask but differing match flags (mflags). * At present there is only one, RESM_NTPONLY. Entries with * RESM_NTPONLY are sorted earlier so they take precedence over * any otherwise similar entry without. Again, this is the same * behavior as but reversed implementation compared to the docs. * */ LINK_SLIST(restrictlist4, &restrict_def4, link); LINK_SLIST(restrictlist6, &restrict_def6, link); restrictcount = 2; } static restrict_u * alloc_res4(void) { const size_t cb = V4_SIZEOF_RESTRICT_U; const size_t count = INC_RESLIST4; restrict_u * rl; restrict_u * res; size_t i; UNLINK_HEAD_SLIST(res, resfree4, link); if (res != NULL) return res; rl = eallocarray(count, cb); /* link all but the first onto free list */ res = (void *)((char *)rl + (count - 1) * cb); for (i = count - 1; i > 0; i--) { LINK_SLIST(resfree4, res, link); res = (void *)((char *)res - cb); } INSIST(rl == res); /* allocate the first */ return res; } static restrict_u * alloc_res6(void) { const size_t cb = V6_SIZEOF_RESTRICT_U; const size_t count = INC_RESLIST6; restrict_u * rl; restrict_u * res; size_t i; UNLINK_HEAD_SLIST(res, resfree6, link); if (res != NULL) return res; rl = eallocarray(count, cb); /* link all but the first onto free list */ res = (void *)((char *)rl + (count - 1) * cb); for (i = count - 1; i > 0; i--) { LINK_SLIST(resfree6, res, link); res = (void *)((char *)res - cb); } INSIST(rl == res); /* allocate the first */ return res; } static void free_res( restrict_u * res, int v6 ) { restrict_u ** plisthead; restrict_u * unlinked; restrictcount--; if (RES_LIMITED & res->flags) dec_res_limited(); if (v6) plisthead = &restrictlist6; else plisthead = &restrictlist4; UNLINK_SLIST(unlinked, *plisthead, res, link, restrict_u); INSIST(unlinked == res); if (v6) { zero_mem(res, V6_SIZEOF_RESTRICT_U); plisthead = &resfree6; } else { zero_mem(res, V4_SIZEOF_RESTRICT_U); plisthead = &resfree4; } LINK_SLIST(*plisthead, res, link); } static void inc_res_limited(void) { if (!res_limited_refcnt) mon_start(MON_RES); res_limited_refcnt++; } static void dec_res_limited(void) { res_limited_refcnt--; if (!res_limited_refcnt) mon_stop(MON_RES); } static restrict_u * match_restrict4_addr( u_int32 addr, u_short port ) { const int v6 = 0; restrict_u * res; restrict_u * next; for (res = restrictlist4; res != NULL; res = next) { next = res->link; if (res->expire && res->expire <= current_time) free_res(res, v6); if (res->u.v4.addr == (addr & res->u.v4.mask) && (!(RESM_NTPONLY & res->mflags) || NTP_PORT == port)) break; } return res; } static restrict_u * match_restrict6_addr( const struct in6_addr * addr, u_short port ) { const int v6 = 1; restrict_u * res; restrict_u * next; struct in6_addr masked; for (res = restrictlist6; res != NULL; res = next) { next = res->link; INSIST(next != res); if (res->expire && res->expire <= current_time) free_res(res, v6); MASK_IPV6_ADDR(&masked, addr, &res->u.v6.mask); if (ADDR6_EQ(&masked, &res->u.v6.addr) && (!(RESM_NTPONLY & res->mflags) || NTP_PORT == (int)port)) break; } return res; } /* * match_restrict_entry - find an exact match on a restrict list. * * Exact match is addr, mask, and mflags all equal. * In order to use more common code for IPv4 and IPv6, this routine * requires the caller to populate a restrict_u with mflags and either * the v4 or v6 address and mask as appropriate. Other fields in the * input restrict_u are ignored. */ static restrict_u * match_restrict_entry( const restrict_u * pmatch, int v6 ) { restrict_u *res; restrict_u *rlist; size_t cb; if (v6) { rlist = restrictlist6; cb = sizeof(pmatch->u.v6); } else { rlist = restrictlist4; cb = sizeof(pmatch->u.v4); } for (res = rlist; res != NULL; res = res->link) if (res->mflags == pmatch->mflags && !memcmp(&res->u, &pmatch->u, cb)) break; return res; } /* * res_sorts_before4 - compare two restrict4 entries * * Returns nonzero if r1 sorts before r2. We sort by descending * address, then descending mask, then descending mflags, so sorting * before means having a higher value. */ static int res_sorts_before4( restrict_u *r1, restrict_u *r2 ) { int r1_before_r2; if (r1->u.v4.addr > r2->u.v4.addr) r1_before_r2 = 1; else if (r1->u.v4.addr < r2->u.v4.addr) r1_before_r2 = 0; else if (r1->u.v4.mask > r2->u.v4.mask) r1_before_r2 = 1; else if (r1->u.v4.mask < r2->u.v4.mask) r1_before_r2 = 0; else if (r1->mflags > r2->mflags) r1_before_r2 = 1; else r1_before_r2 = 0; return r1_before_r2; } /* * res_sorts_before6 - compare two restrict6 entries * * Returns nonzero if r1 sorts before r2. We sort by descending * address, then descending mask, then descending mflags, so sorting * before means having a higher value. */ static int res_sorts_before6( restrict_u *r1, restrict_u *r2 ) { int r1_before_r2; int cmp; cmp = ADDR6_CMP(&r1->u.v6.addr, &r2->u.v6.addr); if (cmp > 0) /* r1->addr > r2->addr */ r1_before_r2 = 1; else if (cmp < 0) /* r2->addr > r1->addr */ r1_before_r2 = 0; else { cmp = ADDR6_CMP(&r1->u.v6.mask, &r2->u.v6.mask); if (cmp > 0) /* r1->mask > r2->mask*/ r1_before_r2 = 1; else if (cmp < 0) /* r2->mask > r1->mask */ r1_before_r2 = 0; else if (r1->mflags > r2->mflags) r1_before_r2 = 1; else r1_before_r2 = 0; } return r1_before_r2; } /* * restrictions - return restrictions for this host */ u_short restrictions( sockaddr_u *srcadr ) { restrict_u *match; struct in6_addr *pin6; u_short flags; res_calls++; flags = 0; /* IPv4 source address */ if (IS_IPV4(srcadr)) { /* * Ignore any packets with a multicast source address * (this should be done early in the receive process, * not later!) */ if (IN_CLASSD(SRCADR(srcadr))) return (int)RES_IGNORE; match = match_restrict4_addr(SRCADR(srcadr), SRCPORT(srcadr)); INSIST(match != NULL); match->count++; /* * res_not_found counts only use of the final default * entry, not any "restrict default ntpport ...", which * would be just before the final default. */ if (&restrict_def4 == match) res_not_found++; else res_found++; flags = match->flags; } /* IPv6 source address */ if (IS_IPV6(srcadr)) { pin6 = PSOCK_ADDR6(srcadr); /* * Ignore any packets with a multicast source address * (this should be done early in the receive process, * not later!) */ if (IN6_IS_ADDR_MULTICAST(pin6)) return (int)RES_IGNORE; match = match_restrict6_addr(pin6, SRCPORT(srcadr)); INSIST(match != NULL); match->count++; if (&restrict_def6 == match) res_not_found++; else res_found++; flags = match->flags; } return (flags); } /* * hack_restrict - add/subtract/manipulate entries on the restrict list */ void hack_restrict( int op, sockaddr_u * resaddr, sockaddr_u * resmask, u_short mflags, u_short flags, u_long expire ) { int v6; restrict_u match; restrict_u * res; restrict_u ** plisthead; DPRINTF(1, ("restrict: op %d addr %s mask %s mflags %08x flags %08x\n", op, stoa(resaddr), stoa(resmask), mflags, flags)); if (NULL == resaddr) { REQUIRE(NULL == resmask); REQUIRE(RESTRICT_FLAGS == op); restrict_source_flags = flags; restrict_source_mflags = mflags; restrict_source_enabled = 1; return; } ZERO(match); #if 0 /* silence VC9 potentially uninit warnings */ // HMS: let's use a compiler-specific "enable" for this. res = NULL; v6 = 0; #endif if (IS_IPV4(resaddr)) { v6 = 0; /* * Get address and mask in host byte order for easy * comparison as u_int32 */ match.u.v4.addr = SRCADR(resaddr); match.u.v4.mask = SRCADR(resmask); match.u.v4.addr &= match.u.v4.mask; } else if (IS_IPV6(resaddr)) { v6 = 1; /* * Get address and mask in network byte order for easy * comparison as byte sequences (e.g. memcmp()) */ match.u.v6.mask = SOCK_ADDR6(resmask); MASK_IPV6_ADDR(&match.u.v6.addr, PSOCK_ADDR6(resaddr), &match.u.v6.mask); } else /* not IPv4 nor IPv6 */ REQUIRE(0); match.flags = flags; match.mflags = mflags; match.expire = expire; res = match_restrict_entry(&match, v6); switch (op) { case RESTRICT_FLAGS: /* * Here we add bits to the flags. If this is a * new restriction add it. */ if (NULL == res) { if (v6) { res = alloc_res6(); memcpy(res, &match, V6_SIZEOF_RESTRICT_U); plisthead = &restrictlist6; } else { res = alloc_res4(); memcpy(res, &match, V4_SIZEOF_RESTRICT_U); plisthead = &restrictlist4; } LINK_SORT_SLIST( *plisthead, res, (v6) ? res_sorts_before6(res, L_S_S_CUR()) : res_sorts_before4(res, L_S_S_CUR()), link, restrict_u); restrictcount++; if (RES_LIMITED & flags) inc_res_limited(); } else { if ((RES_LIMITED & flags) && !(RES_LIMITED & res->flags)) inc_res_limited(); res->flags |= flags; } break; case RESTRICT_UNFLAG: /* * Remove some bits from the flags. If we didn't * find this one, just return. */ if (res != NULL) { if ((RES_LIMITED & res->flags) && (RES_LIMITED & flags)) dec_res_limited(); res->flags &= ~flags; } break; case RESTRICT_REMOVE: case RESTRICT_REMOVEIF: /* * Remove an entry from the table entirely if we * found one. Don't remove the default entry and * don't remove an interface entry. */ if (res != NULL && (RESTRICT_REMOVEIF == op || !(RESM_INTERFACE & res->mflags)) && res != &restrict_def4 && res != &restrict_def6) free_res(res, v6); break; default: /* unknown op */ INSIST(0); break; } } /* * restrict_source - maintains dynamic "restrict source ..." entries as * peers come and go. */ void restrict_source( sockaddr_u * addr, int farewell, /* 0 to add, 1 to remove */ u_long expire /* 0 is infinite, valid until */ ) { sockaddr_u onesmask; restrict_u * res; int found_specific; if (!restrict_source_enabled || SOCK_UNSPEC(addr) || IS_MCAST(addr) || ISREFCLOCKADR(addr)) return; REQUIRE(AF_INET == AF(addr) || AF_INET6 == AF(addr)); SET_HOSTMASK(&onesmask, AF(addr)); if (farewell) { hack_restrict(RESTRICT_REMOVE, addr, &onesmask, 0, 0, 0); DPRINTF(1, ("restrict_source: %s removed", stoa(addr))); return; } /* * If there is a specific entry for this address, hands * off, as it is condidered more specific than "restrict * server ...". * However, if the specific entry found is a fleeting one * added by pool_xmit() before soliciting, replace it * immediately regardless of the expire value to make way * for the more persistent entry. */ if (IS_IPV4(addr)) { res = match_restrict4_addr(SRCADR(addr), SRCPORT(addr)); INSIST(res != NULL); found_specific = (SRCADR(&onesmask) == res->u.v4.mask); } else { res = match_restrict6_addr(&SOCK_ADDR6(addr), SRCPORT(addr)); INSIST(res != NULL); found_specific = ADDR6_EQ(&res->u.v6.mask, &SOCK_ADDR6(&onesmask)); } if (!expire && found_specific && res->expire) { found_specific = 0; free_res(res, IS_IPV6(addr)); } if (found_specific) return; hack_restrict(RESTRICT_FLAGS, addr, &onesmask, restrict_source_mflags, restrict_source_flags, expire); DPRINTF(1, ("restrict_source: %s host restriction added\n", stoa(addr))); }