| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2015 */ |
| 6 | /* Copyright (c) The Exim Maintainers 2020 */ |
| 7 | /* See the file NOTICE for conditions of use and distribution. */ |
| 8 | |
| 9 | |
| 10 | #include "../exim.h" |
| 11 | #include "rf_functions.h" |
| 12 | |
| 13 | |
| 14 | |
| 15 | /************************************************* |
| 16 | * Look up IP addresses for a set of hosts * |
| 17 | *************************************************/ |
| 18 | |
| 19 | /* This function is called by a router to fill in the IP addresses for a set of |
| 20 | hosts that are attached to an address. Each host has its name and MX value set; |
| 21 | and those that need processing have their address fields set NULL. Multihomed |
| 22 | hosts cause additional blocks to be inserted into the chain. |
| 23 | |
| 24 | This function also supports pseudo-hosts whose names end with "/MX". In this |
| 25 | case, MX records are looked up for the name, and the list of hosts obtained |
| 26 | replaces the incoming "host". In other words, "x/MX" is shorthand for "those |
| 27 | hosts pointed to by x's MX records". |
| 28 | |
| 29 | It is also possible for a port to be specified along with the host name or IP |
| 30 | address. The syntax is to add ":port" on to the end. This doesn't work with |
| 31 | IPv6 addresses, so we allow IP addresses to be enclosed in [] in order to make |
| 32 | this work. The specification of the port must come last, that is, after "/MX" |
| 33 | if that is present. |
| 34 | |
| 35 | Arguments: |
| 36 | rblock the router block |
| 37 | addr the address being routed |
| 38 | ignore_target_hosts list of hosts to ignore |
| 39 | lookup_type LK_DEFAULT or LK_BYNAME or LK_BYDNS, |
| 40 | plus LK_IPV4_{ONLY,PREFER} |
| 41 | hff_code what to do for host find failed |
| 42 | addr_new passed to rf_self_action for self=reroute |
| 43 | |
| 44 | Returns: OK |
| 45 | DEFER host lookup defer |
| 46 | PASS timeout etc and pass_on_timeout set |
| 47 | self_action: PASS, DECLINE, DEFER, FAIL, FREEZE |
| 48 | hff_code after host find failed |
| 49 | */ |
| 50 | |
| 51 | int |
| 52 | rf_lookup_hostlist(router_instance *rblock, address_item *addr, |
| 53 | uschar *ignore_target_hosts, int lookup_type, int hff_code, |
| 54 | address_item **addr_new) |
| 55 | { |
| 56 | BOOL self_send = FALSE; |
| 57 | |
| 58 | /* Look up each host address. A lookup may add additional items into the chain |
| 59 | if there are multiple addresses. Hence the use of next_h to start each cycle of |
| 60 | the loop at the next original host. If any host is identified as being the local |
| 61 | host, omit it and any subsequent hosts - i.e. treat the list like an ordered |
| 62 | list of MX hosts. If the first host is the local host, act according to the |
| 63 | "self" option in the configuration. */ |
| 64 | |
| 65 | for (host_item * prev = NULL, * h = addr->host_list, *next_h; h; h = next_h) |
| 66 | { |
| 67 | const uschar *canonical_name; |
| 68 | int rc, len, port, mx, sort_key; |
| 69 | |
| 70 | next_h = h->next; |
| 71 | if (h->address) { prev = h; continue; } |
| 72 | |
| 73 | DEBUG(D_route|D_host_lookup) |
| 74 | debug_printf("finding IP address for %s\n", h->name); |
| 75 | |
| 76 | /* Handle any port setting that may be on the name; it will be removed |
| 77 | from the end of the name. */ |
| 78 | |
| 79 | port = host_item_get_port(h); |
| 80 | |
| 81 | /* Store the previous mx and sort_key values, which were assigned in |
| 82 | host_build_hostlist and will be overwritten by host_find_bydns. */ |
| 83 | |
| 84 | mx = h->mx; |
| 85 | sort_key = h->sort_key; |
| 86 | |
| 87 | /* If the name ends with "/MX", we interpret it to mean "the list of hosts |
| 88 | pointed to by MX records with this name", and the MX record values override |
| 89 | the ordering from host_build_hostlist. */ |
| 90 | |
| 91 | len = Ustrlen(h->name); |
| 92 | if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0) |
| 93 | { |
| 94 | int whichrrs = lookup_type & LK_IPV4_ONLY |
| 95 | ? HOST_FIND_BY_MX | HOST_FIND_IPV4_ONLY |
| 96 | : lookup_type & LK_IPV4_PREFER |
| 97 | ? HOST_FIND_BY_MX | HOST_FIND_IPV4_FIRST |
| 98 | : HOST_FIND_BY_MX; |
| 99 | |
| 100 | DEBUG(D_route|D_host_lookup) |
| 101 | debug_printf("doing DNS MX lookup for %s\n", h->name); |
| 102 | |
| 103 | mx = MX_NONE; |
| 104 | h->name = string_copyn(h->name, len - 3); |
| 105 | rc = host_find_bydns(h, |
| 106 | ignore_target_hosts, |
| 107 | whichrrs, /* look only for MX records */ |
| 108 | NULL, /* SRV service not relevant */ |
| 109 | NULL, /* failing srv domains not relevant */ |
| 110 | NULL, /* no special mx failing domains */ |
| 111 | &rblock->dnssec, /* dnssec request/require */ |
| 112 | NULL, /* fully_qualified_name */ |
| 113 | NULL); /* indicate local host removed */ |
| 114 | } |
| 115 | |
| 116 | /* If explicitly configured to look up by name, or if the "host name" is |
| 117 | actually an IP address, do a byname lookup. */ |
| 118 | |
| 119 | else if (lookup_type & LK_BYNAME || string_is_ip_address(h->name, NULL) != 0) |
| 120 | { |
| 121 | DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n"); |
| 122 | rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE, |
| 123 | &canonical_name, TRUE); |
| 124 | } |
| 125 | |
| 126 | /* Otherwise, do a DNS lookup. If that yields "host not found", and the |
| 127 | lookup type is the default (i.e. "bydns" is not explicitly configured), |
| 128 | follow up with a byname lookup, just in case. */ |
| 129 | |
| 130 | else |
| 131 | { |
| 132 | BOOL removed; |
| 133 | int whichrrs = lookup_type & LK_IPV4_ONLY |
| 134 | ? HOST_FIND_BY_A |
| 135 | : lookup_type & LK_IPV4_PREFER |
| 136 | ? HOST_FIND_BY_A | HOST_FIND_BY_AAAA | HOST_FIND_IPV4_FIRST |
| 137 | : HOST_FIND_BY_A | HOST_FIND_BY_AAAA; |
| 138 | |
| 139 | DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n"); |
| 140 | switch (rc = host_find_bydns(h, ignore_target_hosts, whichrrs, NULL, |
| 141 | NULL, NULL, |
| 142 | &rblock->dnssec, /* domains for request/require */ |
| 143 | &canonical_name, &removed)) |
| 144 | { |
| 145 | case HOST_FOUND: |
| 146 | if (removed) setflag(addr, af_local_host_removed); |
| 147 | break; |
| 148 | case HOST_FIND_FAILED: |
| 149 | if (lookup_type & LK_DEFAULT) |
| 150 | { |
| 151 | DEBUG(D_route|D_host_lookup) |
| 152 | debug_printf("DNS lookup failed: trying %s\n", |
| 153 | f.running_in_test_harness |
| 154 | ? "host_fake_gethostbyname" : "getipnodebyname"); |
| 155 | rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE, |
| 156 | &canonical_name, TRUE); |
| 157 | } |
| 158 | break; |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /* Temporary failure defers, unless pass_on_timeout is set */ |
| 163 | |
| 164 | if (rc == HOST_FIND_SECURITY) |
| 165 | { |
| 166 | addr->message = string_sprintf("host lookup for %s done insecurely" , h->name); |
| 167 | addr->basic_errno = ERRNO_DNSDEFER; |
| 168 | return DEFER; |
| 169 | } |
| 170 | if (rc == HOST_FIND_AGAIN) |
| 171 | { |
| 172 | if (rblock->pass_on_timeout) |
| 173 | { |
| 174 | DEBUG(D_route) |
| 175 | debug_printf("%s router timed out and pass_on_timeout set\n", |
| 176 | rblock->name); |
| 177 | return PASS; |
| 178 | } |
| 179 | addr->message = string_sprintf("host lookup for %s did not complete " |
| 180 | "(DNS timeout?)", h->name); |
| 181 | addr->basic_errno = ERRNO_DNSDEFER; |
| 182 | return DEFER; |
| 183 | } |
| 184 | |
| 185 | /* Permanent failure is controlled by host_find_failed */ |
| 186 | |
| 187 | if (rc == HOST_FIND_FAILED) |
| 188 | { |
| 189 | if (hff_code == hff_ignore) |
| 190 | { |
| 191 | if (prev == NULL) addr->host_list = next_h; else prev->next = next_h; |
| 192 | continue; /* With the next host, leave prev unchanged */ |
| 193 | } |
| 194 | |
| 195 | if (hff_code == hff_pass) return PASS; |
| 196 | if (hff_code == hff_decline) return DECLINE; |
| 197 | |
| 198 | addr->basic_errno = ERRNO_UNKNOWNHOST; |
| 199 | addr->message = |
| 200 | string_sprintf("lookup of host \"%s\" failed in %s router%s", |
| 201 | h->name, rblock->name, |
| 202 | f.host_find_failed_syntax? ": syntax error in name" : ""); |
| 203 | |
| 204 | if (hff_code == hff_defer) return DEFER; |
| 205 | if (hff_code == hff_fail) return FAIL; |
| 206 | |
| 207 | addr->special_action = SPECIAL_FREEZE; |
| 208 | return DEFER; |
| 209 | } |
| 210 | |
| 211 | /* Deal with the settings that were previously cleared: |
| 212 | port, mx and sort_key. */ |
| 213 | |
| 214 | if (port != PORT_NONE) |
| 215 | for (host_item * hh = h; hh != next_h; hh = hh->next) |
| 216 | hh->port = port; |
| 217 | |
| 218 | if (mx != MX_NONE) |
| 219 | for (host_item * hh = h; hh != next_h; hh = hh->next) |
| 220 | { |
| 221 | hh->mx = mx; |
| 222 | hh->sort_key = sort_key; |
| 223 | } |
| 224 | |
| 225 | /* A local host gets chopped, with its successors, if there are previous |
| 226 | hosts. Otherwise the self option is used. If it is set to "send", any |
| 227 | subsequent hosts that are also the local host do NOT get chopped. */ |
| 228 | |
| 229 | if (rc == HOST_FOUND_LOCAL && !self_send) |
| 230 | { |
| 231 | if (prev) |
| 232 | { |
| 233 | DEBUG(D_route) |
| 234 | { |
| 235 | debug_printf("Removed from host list:\n"); |
| 236 | for (; h; h = h->next) debug_printf(" %s\n", h->name); |
| 237 | } |
| 238 | prev->next = NULL; |
| 239 | setflag(addr, af_local_host_removed); |
| 240 | break; |
| 241 | } |
| 242 | rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite, |
| 243 | rblock->self, addr_new); |
| 244 | if (rc != OK) |
| 245 | { |
| 246 | addr->host_list = NULL; /* Kill the host list for */ |
| 247 | return rc; /* anything other than "send" */ |
| 248 | } |
| 249 | self_send = TRUE; |
| 250 | } |
| 251 | |
| 252 | /* Ensure that prev is the host before next_h; this will not be h if a lookup |
| 253 | found multiple addresses or multiple MX records. */ |
| 254 | |
| 255 | prev = h; |
| 256 | while (prev->next != next_h) prev = prev->next; |
| 257 | } |
| 258 | |
| 259 | return OK; |
| 260 | } |
| 261 | |
| 262 | /* End of rf_lookup_hostlist.c */ |