2 * checkalias.c -- check to see if two hostnames or IP addresses are equivalent
4 * Copyright 1997 by Eric S. Raymond
5 * For license terms, see the file COPYING in this directory.
11 #include <sys/types.h>
12 #ifdef HAVE_NET_SOCKET_H
13 #include <net/socket.h>
15 #include <sys/socket.h>
17 #include <netinet/in.h>
18 #ifdef HAVE_ARPA_INET_H
19 #include <arpa/inet.h>
24 #include "fetchmail.h"
25 #include "getaddrinfo.h"
29 typedef unsigned char address_t[sizeof (struct in_addr)];
31 static int getaddresses(struct addrinfo **result, const char *name)
33 struct addrinfo hints;
35 memset(&hints, 0, sizeof(hints));
36 hints.ai_socktype=SOCK_STREAM;
37 hints.ai_protocol=PF_UNSPEC;
38 hints.ai_family=AF_UNSPEC;
39 return getaddrinfo(name, NULL, &hints, result);
42 /* XXX FIXME: doesn't detect if an IPv6-mapped IPv4 address
43 * matches a real IPv4 address */
44 static int compareaddr(const struct addrinfo *a1, const struct addrinfo *a2)
46 if (a1->ai_family != a2->ai_family) return FALSE;
47 if (a1->ai_addrlen != a2->ai_addrlen) return FALSE;
48 return (!memcmp(a1->ai_addr, a2->ai_addr, a1->ai_addrlen));
51 static int is_ip_alias(const char *name1,const char *name2)
53 * Given two hostnames as arguments, returns TRUE if they
54 * have at least one IP address in common.
55 * No check is done on errors returned by gethostbyname,
56 * the calling function does them.
61 struct addrinfo *res1 = NULL, *res2 = NULL, *ii, *ij;
63 if (getaddresses(&res1, name1))
66 if (getaddresses(&res2, name2))
69 for (ii = res1 ; ii ; ii = ii -> ai_next) {
70 for (ij = res2 ; ij ; ij = ij -> ai_next) {
71 if (compareaddr(ii, ij)) {
86 int is_host_alias(const char *name, struct query *ctl)
87 /* determine whether name is a DNS alias of the mailserver for this query */
89 struct mxentry *mxp, *mxrecords;
92 struct addrinfo hints, *res, *res_st;
94 struct hostdata *lead_server =
95 ctl->server.lead_server ? ctl->server.lead_server : &ctl->server;
98 * The first two checks are optimizations that will catch a good
101 * (1) check against the `true name' deduced from the poll label
102 * and the via option (if present) at the beginning of the poll cycle.
103 * Odds are good this will either be the mailserver's FQDN or a suffix of
104 * it with the mailserver's domain's default host name omitted.
106 * (2) Then check the rest of the `also known as'
107 * cache accumulated by previous DNS checks. This cache is primed
108 * by the aka list option.
110 * Any of these on a mail address is definitive. Only if the
111 * name doesn't match any is it time to call the bind library.
112 * If this happens odds are good we're looking at an MX name.
114 if (strcasecmp(lead_server->truename, name) == 0)
116 else if (str_in_list(&lead_server->akalist, name, TRUE))
120 * Now check for a suffix match on the akalist. The theory here is
121 * that if the user says `aka netaxs.com', we actually want to match
122 * foo.netaxs.com and bar.netaxs.com.
124 namelen = strlen(name);
125 for (idl = lead_server->akalist; idl; idl = idl->next)
130 * Test is >= here because str_in_list() should have caught the
131 * equal-length case above. Doing it this way guarantees that
132 * ep[-1] is a valid reference.
134 if (strlen(idl->id) >= namelen)
136 ep = (char *)name + (namelen - strlen(idl->id));
137 /* a suffix led by . must match */
138 if (ep[-1] == '.' && !strcasecmp(ep, idl->id))
142 if (!ctl->server.dns)
144 #ifndef HAVE_RES_SEARCH
148 * The only code that calls the BIND library is here and in the
149 * start-of-run probe with gethostbyname(3) under ETRN/Kerberos.
151 * We know DNS service was up at the beginning of the run.
152 * If it's down, our nameserver has crashed. We don't want to try
153 * delivering the current message or anything else from the
154 * current server until it's back up.
156 memset(&hints, 0, sizeof hints);
157 hints.ai_family=AF_UNSPEC;
158 hints.ai_protocol=PF_UNSPEC;
159 hints.ai_socktype=SOCK_STREAM;
160 hints.ai_flags=AI_CANONNAME;
162 e = getaddrinfo(name, NULL, &hints, &res);
165 int rr = (strcasecmp(ctl->server.truename, res->ai_canonname) == 0);
169 else if (ctl->server.checkalias && 0 == getaddrinfo(ctl->server.truename, NULL, &hints, &res_st))
171 freeaddrinfo(res_st);
172 if (outlevel >= O_DEBUG)
173 report(stdout, GT_("Checking if %s is really the same node as %s\n"),ctl->server.truename,name);
174 if (is_ip_alias(ctl->server.truename,name) == TRUE)
176 if (outlevel >= O_DEBUG)
177 report(stdout, GT_("Yes, their IP addresses match\n"));
180 if (outlevel >= O_DEBUG)
181 report(stdout, GT_("No, their IP addresses don't match\n"));
190 case EAI_NONAME: /* specified host is unknown */
194 if (outlevel != O_SILENT)
195 report_complete(stdout, "\n"); /* terminate the progress message */
197 GT_("nameserver failure while looking for '%s' during poll of %s: %s\n"),
198 name, ctl->server.pollname, gai_strerror(e));
204 * We're only here if DNS was OK but the gethostbyname() failed
205 * with a HOST_NOT_FOUND or NO_ADDRESS error.
206 * Search for a name match on MX records pointing to the server.
209 if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
213 case HOST_NOT_FOUND: /* specified host is unknown */
215 case NO_ADDRESS: /* valid, but does not have an IP address */
218 case NO_RECOVERY: /* non-recoverable name server error */
219 case TRY_AGAIN: /* temporary error on authoritative server */
222 GT_("nameserver failure while looking for `%s' during poll of %s.\n"),
223 name, ctl->server.pollname);
228 for (mxp = mxrecords; mxp->name; mxp++)
229 if (strcasecmp(ctl->server.truename, mxp->name) == 0
230 || is_ip_alias(ctl->server.truename, mxp->name) == TRUE)
236 /* add this name to relevant server's `also known as' list */
237 save_str(&lead_server->akalist, name, 0);
239 #endif /* HAVE_RES_SEARCH */
242 /* checkalias.c ends here */