Debugging: fix potential null-derefs in DSN debug_printfs
[exim.git] / src / src / routers / rf_lookup_hostlist.c
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1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4
3386088d 5/* Copyright (c) University of Cambridge 1995 - 2015 */
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6/* See the file NOTICE for conditions of use and distribution. */
7
8
9#include "../exim.h"
10#include "rf_functions.h"
11
12
13
14/*************************************************
15* Look up IP addresses for a set of hosts *
16*************************************************/
17
18/* This function is called by a router to fill in the IP addresses for a set of
19hosts that are attached to an address. Each host has its name and MX value set;
20and those that need processing have their address fields set NULL. Multihomed
21hosts cause additional blocks to be inserted into the chain.
22
23This function also supports pseudo-hosts whose names end with "/MX". In this
24case, MX records are looked up for the name, and the list of hosts obtained
25replaces the incoming "host". In other words, "x/MX" is shorthand for "those
26hosts pointed to by x's MX records".
27
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28It is also possible for a port to be specified along with the host name or IP
29address. The syntax is to add ":port" on to the end. This doesn't work with
30IPv6 addresses, so we allow IP addresses to be enclosed in [] in order to make
31this work. The specification of the port must come last, that is, after "/MX"
32if that is present.
33
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34Arguments:
35 rblock the router block
36 addr the address being routed
37 ignore_target_hosts list of hosts to ignore
38 lookup_type lk_default or lk_byname or lk_bydns
39 hff_code what to do for host find failed
40 addr_new passed to rf_self_action for self=reroute
41
42Returns: OK
43 DEFER host lookup defer
44 PASS timeout etc and pass_on_timeout set
45 self_action: PASS, DECLINE, DEFER, FAIL, FREEZE
46 hff_code after host find failed
47*/
48
49int
50rf_lookup_hostlist(router_instance *rblock, address_item *addr,
51 uschar *ignore_target_hosts, int lookup_type, int hff_code,
52 address_item **addr_new)
53{
54BOOL self_send = FALSE;
55host_item *h, *next_h, *prev;
56
57/* Look up each host address. A lookup may add additional items into the chain
58if there are multiple addresses. Hence the use of next_h to start each cycle of
59the loop at the next original host. If any host is identified as being the local
60host, omit it and any subsequent hosts - i.e. treat the list like an ordered
61list of MX hosts. If the first host is the local host, act according to the
62"self" option in the configuration. */
63
fff1b300 64for (prev = NULL, h = addr->host_list; h; h = next_h)
0756eb3c 65 {
55414b25 66 const uschar *canonical_name;
fff1b300 67 int rc, len, port, mx, sort_key;
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68
69 next_h = h->next;
fff1b300 70 if (h->address) { prev = h; continue; }
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71
72 DEBUG(D_route|D_host_lookup)
73 debug_printf("finding IP address for %s\n", h->name);
74
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75 /* Handle any port setting that may be on the name; it will be removed
76 from the end of the name. */
77
78 port = host_item_get_port(h);
79
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80 /* Store the previous mx and sort_key values, which were assigned in
81 host_build_hostlist and will be overwritten by host_find_bydns. */
82
83 mx = h->mx;
84 sort_key = h->sort_key;
85
0756eb3c 86 /* If the name ends with "/MX", we interpret it to mean "the list of hosts
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87 pointed to by MX records with this name", and the MX record values override
88 the ordering from host_build_hostlist. */
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89
90 len = Ustrlen(h->name);
91 if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0)
92 {
93 DEBUG(D_route|D_host_lookup)
94 debug_printf("doing DNS MX lookup for %s\n", h->name);
95
fff1b300 96 mx = MX_NONE;
7cd1141b 97 h->name = string_copyn(h->name, len - 3);
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98 rc = host_find_bydns(h,
99 ignore_target_hosts,
100 HOST_FIND_BY_MX, /* look only for MX records */
101 NULL, /* SRV service not relevant */
102 NULL, /* failing srv domains not relevant */
103 NULL, /* no special mx failing domains */
7cd171b7 104 &rblock->dnssec, /* dnssec request/require */
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105 NULL, /* fully_qualified_name */
106 NULL); /* indicate local host removed */
107 }
108
109 /* If explicitly configured to look up by name, or if the "host name" is
110 actually an IP address, do a byname lookup. */
111
7e66e54d 112 else if (lookup_type == lk_byname || string_is_ip_address(h->name, NULL) != 0)
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113 {
114 DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n");
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115 rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
116 &canonical_name, TRUE);
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117 }
118
119 /* Otherwise, do a DNS lookup. If that yields "host not found", and the
120 lookup type is the default (i.e. "bydns" is not explicitly configured),
121 follow up with a byname lookup, just in case. */
122
123 else
124 {
125 BOOL removed;
126 DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n");
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127 switch (rc = host_find_bydns(h, ignore_target_hosts, HOST_FIND_BY_A, NULL,
128 NULL, NULL,
129 &rblock->dnssec, /* domains for request/require */
130 &canonical_name, &removed))
0756eb3c 131 {
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132 case HOST_FOUND:
133 if (removed) setflag(addr, af_local_host_removed);
134 break;
135 case HOST_FIND_FAILED:
136 if (lookup_type == lk_default)
137 {
138 DEBUG(D_route|D_host_lookup)
139 debug_printf("DNS lookup failed: trying getipnodebyname\n");
140 rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
141 &canonical_name, TRUE);
142 }
143 break;
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144 }
145 }
146
147 /* Temporary failure defers, unless pass_on_timeout is set */
148
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149 if (rc == HOST_FIND_SECURITY)
150 {
151 addr->message = string_sprintf("host lookup for %s done insecurely" , h->name);
152 addr->basic_errno = ERRNO_DNSDEFER;
153 return DEFER;
154 }
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155 if (rc == HOST_FIND_AGAIN)
156 {
157 if (rblock->pass_on_timeout)
158 {
159 DEBUG(D_route)
160 debug_printf("%s router timed out and pass_on_timeout set\n",
161 rblock->name);
162 return PASS;
163 }
164 addr->message = string_sprintf("host lookup for %s did not complete "
165 "(DNS timeout?)", h->name);
166 addr->basic_errno = ERRNO_DNSDEFER;
167 return DEFER;
168 }
169
170 /* Permanent failure is controlled by host_find_failed */
171
172 if (rc == HOST_FIND_FAILED)
173 {
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174 if (hff_code == hff_ignore)
175 {
176 if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
cd9868ec 177 continue; /* With the next host, leave prev unchanged */
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178 }
179
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180 if (hff_code == hff_pass) return PASS;
181 if (hff_code == hff_decline) return DECLINE;
182
bd4ece7d 183 addr->basic_errno = ERRNO_UNKNOWNHOST;
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184 addr->message =
185 string_sprintf("lookup of host \"%s\" failed in %s router%s",
186 h->name, rblock->name,
187 host_find_failed_syntax? ": syntax error in name" : "");
188
189 if (hff_code == hff_defer) return DEFER;
190 if (hff_code == hff_fail) return FAIL;
191
192 addr->special_action = SPECIAL_FREEZE;
193 return DEFER;
194 }
195
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196 /* Deal with the settings that were previously cleared:
197 port, mx and sort_key. */
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198
199 if (port != PORT_NONE)
200 {
201 host_item *hh;
202 for (hh = h; hh != next_h; hh = hh->next) hh->port = port;
203 }
204
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205 if (mx != MX_NONE)
206 {
207 host_item *hh;
208 for (hh = h; hh != next_h; hh = hh->next)
209 {
210 hh->mx = mx;
211 hh->sort_key = sort_key;
212 }
213 }
214
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215 /* A local host gets chopped, with its successors, if there are previous
216 hosts. Otherwise the self option is used. If it is set to "send", any
217 subsequent hosts that are also the local host do NOT get chopped. */
218
219 if (rc == HOST_FOUND_LOCAL && !self_send)
220 {
fff1b300 221 if (prev)
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222 {
223 DEBUG(D_route)
224 {
225 debug_printf("Removed from host list:\n");
226 for (; h != NULL; h = h->next) debug_printf(" %s\n", h->name);
227 }
228 prev->next = NULL;
229 setflag(addr, af_local_host_removed);
230 break;
231 }
232 rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
233 rblock->self, addr_new);
234 if (rc != OK)
235 {
236 addr->host_list = NULL; /* Kill the host list for */
237 return rc; /* anything other than "send" */
238 }
239 self_send = TRUE;
240 }
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241
242 /* Ensure that prev is the host before next_h; this will not be h if a lookup
243 found multiple addresses or multiple MX records. */
244
245 prev = h;
246 while (prev->next != next_h) prev = prev->next;
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247 }
248
249return OK;
250}
251
252/* End of rf_lookup_hostlist.c */