#include "common.h" #include enum { Nmx= 16, Maxstring= 256, }; typedef struct Mx Mx; struct Mx { char host[256]; char ip[24]; int pref; }; static Mx mx[Nmx]; typedef struct DS DS; struct DS { /* dist string */ char buf[128]; char *netdir; char *proto; char *host; char *service; }; Ndb *db; extern int debug; static int mxlookup(DS*, char*); static int mxlookup1(DS*, char*); static int compar(void*, void*); static int callmx(DS*, char*, char*); static void dial_string_parse(char*, DS*); extern int cistrcmp(char*, char*); int mxdial(char *addr, char *ddomain, char *gdomain) { int fd; DS ds; char err[Errlen]; addr = netmkaddr(addr, 0, "smtp"); dial_string_parse(addr, &ds); /* try connecting to destination or any of it's mail routers */ fd = callmx(&ds, addr, ddomain); /* try our mail gateway */ rerrstr(err, sizeof(err)); if(fd < 0 && gdomain && strstr(err, "can't translate") != 0) fd = dial(netmkaddr(gdomain, 0, "smtp"), 0, 0, 0); return fd; } /* * take an address and return all the mx entries for it, * most preferred first */ static int callmx(DS *ds, char *dest, char *domain) { int fd, i, nmx; char addr[Maxstring]; /* get a list of mx entries */ nmx = mxlookup(ds, domain); if(nmx < 0){ /* dns isn't working, don't just dial */ return -1; } if(nmx == 0){ if(debug) fprint(2, "mxlookup returns nothing\n"); return dial(dest, 0, 0, 0); } /* refuse to honor loopback addresses given by dns */ for(i = 0; i < nmx; i++){ if(strcmp(mx[i].ip, "127.0.0.1") == 0){ if(debug) fprint(2, "mxlookup returns loopback\n"); werrstr("illegal: domain lists 127.0.0.1 as mail server"); return -1; } } /* sort by preference */ if(nmx > 1) qsort(mx, nmx, sizeof(Mx), compar); /* dial each one in turn */ for(i = 0; i < nmx; i++){ snprint(addr, sizeof(addr), "%s/%s!%s!%s", ds->netdir, ds->proto, mx[i].host, ds->service); if(debug) fprint(2, "mxdial trying %s\n", addr); fd = dial(addr, 0, 0, 0); if(fd >= 0) return fd; } return -1; } /* * call the dns process and have it try to resolve the mx request * * this routine knows about the firewall and tries inside and outside * dns's seperately. */ static int mxlookup(DS *ds, char *domain) { int n; /* just in case we find no domain name */ strcpy(domain, ds->host); if(ds->netdir){ n = mxlookup1(ds, domain); } else { ds->netdir = "/net"; n = mxlookup1(ds, domain); if(n == 0) { ds->netdir = "/net.alt"; n = mxlookup1(ds, domain); } } return n; } static int mxlookup1(DS *ds, char *domain) { char buf[1024]; char dnsname[Maxstring]; char *fields[4]; int i, n, fd, nmx; snprint(dnsname, sizeof dnsname, "%s/dns", ds->netdir); fd = open(dnsname, ORDWR); if(fd < 0) return 0; nmx = 0; snprint(buf, sizeof(buf), "%s mx", ds->host); if(debug) fprint(2, "sending %s '%s'\n", dnsname, buf); n = write(fd, buf, strlen(buf)); if(n < 0){ rerrstr(buf, sizeof buf); if(debug) fprint(2, "dns: %s\n", buf); if(strstr(buf, "dns failure")){ /* if dns fails for the mx lookup, we have to stop */ close(fd); return -1; } } else { /* * get any mx entries */ seek(fd, 0, 0); while(nmx < Nmx && (n = read(fd, buf, sizeof(buf)-1)) > 0){ buf[n] = 0; if(debug) fprint(2, "dns mx: %s\n", buf); n = getfields(buf, fields, 4, 1, " \t"); if(n < 4) continue; if(strchr(domain, '.') == 0) strcpy(domain, fields[0]); strncpy(mx[nmx].host, fields[3], sizeof(mx[n].host)-1); mx[nmx].pref = atoi(fields[2]); nmx++; } if(debug) fprint(2, "dns mx; got %d entries\n", nmx); } /* * no mx record? try name itself. */ /* * BUG? If domain has no dots, then we used to look up ds->host * but return domain instead of ds->host in the list. Now we return * ds->host. What will this break? */ if(nmx == 0){ mx[0].pref = 1; strncpy(mx[0].host, ds->host, sizeof(mx[0].host)); nmx++; } /* * look up all ip addresses */ for(i = 0; i < nmx; i++){ seek(fd, 0, 0); snprint(buf, sizeof buf, "%s ip", mx[i].host); mx[i].ip[0] = 0; if(write(fd, buf, strlen(buf)) < 0) goto no; seek(fd, 0, 0); if((n = read(fd, buf, sizeof buf-1)) < 0) goto no; buf[n] = 0; if(getfields(buf, fields, 4, 1, " \t") < 3) goto no; strncpy(mx[i].ip, fields[2], sizeof(mx[i].ip)-1); continue; no: /* remove mx[i] and go around again */ nmx--; mx[i] = mx[nmx]; i--; } return nmx; } static int compar(void *a, void *b) { return ((Mx*)a)->pref - ((Mx*)b)->pref; } /* break up an address to its component parts */ static void dial_string_parse(char *str, DS *ds) { char *p, *p2; strncpy(ds->buf, str, sizeof(ds->buf)); ds->buf[sizeof(ds->buf)-1] = 0; p = strchr(ds->buf, '!'); if(p == 0) { ds->netdir = 0; ds->proto = "net"; ds->host = ds->buf; } else { if(*ds->buf != '/'){ ds->netdir = 0; ds->proto = ds->buf; } else { for(p2 = p; *p2 != '/'; p2--) ; *p2++ = 0; ds->netdir = ds->buf; ds->proto = p2; } *p = 0; ds->host = p + 1; } ds->service = strchr(ds->host, '!'); if(ds->service) *ds->service++ = 0; } char * expand_meta(char *addr) { DS ds; int fd, n; char *p, cs[128]; static char buf[1024]; dial_string_parse(addr, &ds); if (*ds.host != '$') return addr; if (! ds.netdir) ds.netdir = "/net"; snprint(cs, sizeof(cs), "%s/cs", ds.netdir); if ((fd = open(cs, ORDWR)) == -1){ syslog(0, "smtp", "cannot open cs: %r", cs); return addr; } snprint(buf, sizeof(buf), "!ipinfo %s", ds.host+1); // +1 to skip $ if(write(fd, buf, strlen(buf)) <= 0){ syslog(0, "smtp", "%s to %s - write failed: %r", buf, cs); close(fd); return addr; } seek(fd, 0, 0); if((n = read(fd, buf, sizeof(buf)-1)) < 0){ syslog(0, "smtp", "%s - read failed: %r", cs); close(fd); return addr; } close(fd); buf[n] = 0; if((p = strchr(buf, '=')) == nil){ syslog(0, "smtp", "%q from %s - bad response: %r", buf, cs); return addr; } return p+1; // +1 to skip = }