static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop, char *def_service) { DELIVER_REQUEST *request = state->request; SMTP_ITERATOR *iter = state->iterator; ARGV *sites; char *dest; char **cpp; int non_fallback_sites; int retry_plain = 0; DSN_BUF *why = state->why; /* * For sanity, require that at least one of INET or INET6 is enabled. * Otherwise, we can't look up interface information, and we can't * convert names or addresses. */ if (inet_proto_info()->ai_family_list[0] == 0) { dsb_simple(why, "4.4.4", "all network protocols are disabled"); return; } /* * Future proofing: do a null destination sanity check in case we allow * the primary destination to be a list (it could be just separators). */ sites = argv_alloc(1); argv_add(sites, nexthop, (char *) 0); if (sites->argc == 0) msg_panic("null destination: \"%s\"", nexthop); non_fallback_sites = sites->argc; argv_split_append(sites, var_fallback_relay, CHARS_COMMA_SP); /* * Don't give up after a hard host lookup error until we have tried the * fallback relay servers. * * Don't bounce mail after a host lookup problem with a relayhost or with a * fallback relay. * * Don't give up after a qualifying soft error until we have tried all * qualifying backup mail servers. * * All this means that error handling and error reporting depends on whether * the error qualifies for trying to deliver to a backup mail server, or * whether we're looking up a relayhost or fallback relay. The challenge * then is to build this into the pre-existing SMTP client without * getting lost in the complexity. */ #define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \ (*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites)) for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP); SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0; cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) { char *dest_buf; char *domain; unsigned port; DNS_RR *addr_list; DNS_RR *addr; DNS_RR *next; int addr_count; int sess_count; SMTP_SESSION *session; int lookup_mx; unsigned domain_best_pref; MAI_HOSTADDR_STR hostaddr; if (cpp[1] == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; /* * Parse the destination. If no TCP port is specified, use the port * that is reserved for the protocol (SMTP or LMTP). */ dest_buf = smtp_parse_destination(dest, def_service, &domain, &port); if (var_helpful_warnings && var_smtp_tls_wrappermode == 0 && ntohs(port) == 465) { msg_info("SMTPS wrappermode (TCP port 465) requires setting " "\"%s = yes\", and \"%s = encrypt\" (or stronger)", VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL)); } #define NO_HOST "" /* safety */ #define NO_ADDR "" /* safety */ SMTP_ITER_INIT(iter, dest, NO_HOST, NO_ADDR, port, state); /* * Resolve an SMTP or LMTP server. In the case of SMTP, skip mail * exchanger lookups when a quoted host is specified or when DNS * lookups are disabled. */ if (msg_verbose) msg_info("connecting to %s port %d", domain, ntohs(port)); if (smtp_mode) { if (ntohs(port) == IPPORT_SMTP) state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT; else state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT; lookup_mx = (smtp_dns_support != SMTP_DNS_DISABLED && *dest != '['); } else lookup_mx = 0; if (!lookup_mx) { addr_list = smtp_host_addr(domain, state->misc_flags, why); /* XXX We could be an MX host for this destination... */ } else { int i_am_mx = 0; addr_list = smtp_domain_addr(domain, &iter->mx, state->misc_flags, why, &i_am_mx); /* If we're MX host, don't connect to non-MX backups. */ if (i_am_mx) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; } /* * Don't try fall-back hosts if mail loops to myself. That would just * make the problem worse. */ if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why)) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; /* * No early loop exit or we have a memory leak with dest_buf. */ if (addr_list) domain_best_pref = addr_list->pref; /* * When session caching is enabled, store the first good session for * this delivery request under the next-hop destination name. All * good sessions will be stored under their specific server IP * address. * * XXX smtp_session_cache_destinations specifies domain names without * :port, because : is already used for maptype:mapname. Because of * this limitation we use the bare domain without the optional [] or * non-default TCP port. * * Opportunistic (a.k.a. on-demand) session caching on request by the * queue manager. This is turned temporarily when a destination has a * high volume of mail in the active queue. When the surge reaches * its end, the queue manager requests that connections be retrieved * but not stored. */ if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) { smtp_cache_policy(state, domain); if (state->misc_flags & SMTP_MISC_FLAG_CONN_CACHE_MASK) SET_NEXTHOP_STATE(state, dest); } /* * Delete visited cached hosts from the address list. * * Optionally search the connection cache by domain name or by primary * MX address before we try to create new connections. * * Enforce the MX session and MX address counts per next-hop or * fall-back destination. smtp_reuse_session() will truncate the * address list when either limit is reached. */ if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) { if (state->cache_used->used > 0) smtp_scrub_addr_list(state->cache_used, &addr_list); sess_count = addr_count = smtp_reuse_session(state, &addr_list, domain_best_pref); } else sess_count = addr_count = 0; /* * Connect to an SMTP server: create primary MX connections, and * reuse or create backup MX connections. * * At the start of an SMTP session, all recipients are unmarked. In the * course of an SMTP session, recipients are marked as KEEP (deliver * to alternate mail server) or DROP (remove from recipient list). At * the end of an SMTP session, weed out the recipient list. Unmark * any left-over recipients and try to deliver them to a backup mail * server. * * Cache the first good session under the next-hop destination name. * Cache all good sessions under their physical endpoint. * * Don't query the session cache for primary MX hosts. We already did * that in smtp_reuse_session(), and if any were found in the cache, * they were already deleted from the address list. * * Currently, we use smtp_reuse_addr() only for SASL-unauthenticated * connections. Furthermore, we rely on smtp_reuse_addr() to look up * an existing SASL-unauthenticated connection only when a new * connection would be guaranteed not to require SASL authentication. * * In addition, we rely on smtp_reuse_addr() to look up an existing * plaintext connection only when a new connection would be * guaranteed not to use TLS. */ for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) { next = addr->next; if (++addr_count == var_smtp_mxaddr_limit) next = 0; if (dns_rr_to_pa(addr, &hostaddr) == 0) { msg_warn("cannot convert type %s record to printable address", dns_strtype(addr->type)); /* XXX Assume there is no code at the end of this loop. */ continue; } vstring_strcpy(iter->addr, hostaddr.buf); vstring_strcpy(iter->host, SMTP_HNAME(addr)); iter->rr = addr; #ifdef USE_TLS if (!smtp_tls_policy_cache_query(why, state->tls, iter)) { msg_warn("TLS policy lookup for %s/%s: %s", STR(iter->dest), STR(iter->host), STR(why->reason)); continue; /* XXX Assume there is no code at the end of this loop. */ } if (var_smtp_tls_wrappermode && state->tls->level < TLS_LEV_ENCRYPT) { msg_warn("%s requires \"%s = encrypt\" (or stronger)", VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL)); continue; /* XXX Assume there is no code at the end of this loop. */ } /* Disable TLS when retrying after a handshake failure */ if (retry_plain) { state->tls->level = TLS_LEV_NONE; retry_plain = 0; } #endif if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0 || addr->pref == domain_best_pref || !(session = smtp_reuse_addr(state, SMTP_KEY_MASK_SCACHE_ENDP_LABEL))) session = smtp_connect_addr(iter, why, state->misc_flags); if ((state->session = session) != 0) { session->state = state; #ifdef USE_TLS session->tls_nexthop = domain; #endif if (addr->pref == domain_best_pref) session->features |= SMTP_FEATURE_BEST_MX; /* Don't count handshake errors towards the session limit. */ if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) && next == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER; if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0 && smtp_helo(state) != 0) { #ifdef USE_TLS /* * When an opportunistic TLS handshake fails, try the * same address again, with TLS disabled. See also the * RETRY_AS_PLAINTEXT macro. */ if ((retry_plain = session->tls_retry_plain) != 0) { --addr_count; next = addr; } #endif /* * When a TLS handshake fails, the stream is marked * "dead" to avoid further I/O over a broken channel. */ if (!THIS_SESSION_IS_FORBIDDEN && vstream_ferror(session->stream) == 0 && vstream_feof(session->stream) == 0) smtp_quit(state); } else { /* Do count delivery errors towards the session limit. */ if (++sess_count == var_smtp_mxsess_limit) next = 0; if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) && next == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER; smtp_xfer(state); #ifdef USE_TLS /* * When opportunistic TLS fails after the STARTTLS * handshake, try the same address again, with TLS * disabled. See also the RETRY_AS_PLAINTEXT macro. */ if ((retry_plain = session->tls_retry_plain) != 0) { --sess_count; --addr_count; next = addr; } #endif } smtp_cleanup_session(state); } else { /* The reason already includes the IP address and TCP port. */ msg_info("%s", STR(why->reason)); } /* XXX Code above assumes there is no code at this loop ending. */ } dns_rr_free(addr_list); if (iter->mx) { dns_rr_free(iter->mx); iter->mx = 0; /* Just in case */ } myfree(dest_buf); if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) break; } /* * We still need to deliver, bounce or defer some left-over recipients: * either mail loops or some backup mail server was unavailable. */ if (SMTP_RCPT_LEFT(state) > 0) { /* * In case of a "no error" indication we make up an excuse: we did * find the host address, but we did not attempt to connect to it. * This can happen when the fall-back relay was already tried via a * cached connection, so that the address list scrubber left behind * an empty list. */ if (!SMTP_HAS_DSN(why)) { dsb_simple(why, "4.3.0", "server unavailable or unable to receive mail"); } /* * Pay attention to what could be configuration problems, and pretend * that these are recoverable rather than bouncing the mail. */ else if (!SMTP_HAS_SOFT_DSN(why)) { /* * The fall-back destination did not resolve as expected, or it * is refusing to talk to us, or mail for it loops back to us. */ if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) { msg_warn("%s configuration problem", VAR_SMTP_FALLBACK); vstring_strcpy(why->status, "4.3.5"); /* XXX Keep the diagnostic code and MTA. */ } /* * The next-hop relayhost did not resolve as expected, or it is * refusing to talk to us, or mail for it loops back to us. * * XXX There is no equivalent safety net for mis-configured * sender-dependent relay hosts. The trivial-rewrite resolver * would have to flag the result, and the queue manager would * have to provide that information to delivery agents. */ else if (smtp_mode && strcmp(sites->argv[0], var_relayhost) == 0) { msg_warn("%s configuration problem", VAR_RELAYHOST); vstring_strcpy(why->status, "4.3.5"); /* XXX Keep the diagnostic code and MTA. */ } /* * Mail for the next-hop destination loops back to myself. Pass * the mail to the best_mx_transport or bounce it. */ else if (smtp_mode && SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) { dsb_reset(why); /* XXX */ state->status = deliver_pass_all(MAIL_CLASS_PRIVATE, var_bestmx_transp, request); SMTP_RCPT_LEFT(state) = 0; /* XXX */ } } } /* * Cleanup. */ if (HAVE_NEXTHOP_STATE(state)) FREE_NEXTHOP_STATE(state); argv_free(sites); }
static void smtp_connect_remote(SMTP_STATE *state, const char *nexthop, char *def_service) { DELIVER_REQUEST *request = state->request; ARGV *sites; char *dest; char **cpp; int non_fallback_sites; int retry_plain = 0; DSN_BUF *why = state->why; /* * First try to deliver to the indicated destination, then try to deliver * to the optional fall-back relays. * * Future proofing: do a null destination sanity check in case we allow the * primary destination to be a list (it could be just separators). */ sites = argv_alloc(1); argv_add(sites, nexthop, (char *) 0); if (sites->argc == 0) msg_panic("null destination: \"%s\"", nexthop); non_fallback_sites = sites->argc; if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) argv_split_append(sites, var_fallback_relay, ", \t\r\n"); /* * Don't give up after a hard host lookup error until we have tried the * fallback relay servers. * * Don't bounce mail after a host lookup problem with a relayhost or with a * fallback relay. * * Don't give up after a qualifying soft error until we have tried all * qualifying backup mail servers. * * All this means that error handling and error reporting depends on whether * the error qualifies for trying to deliver to a backup mail server, or * whether we're looking up a relayhost or fallback relay. The challenge * then is to build this into the pre-existing SMTP client without * getting lost in the complexity. */ #define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \ (*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites)) for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP); SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0; cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) { char *dest_buf; char *domain; unsigned port; DNS_RR *addr_list; DNS_RR *addr; DNS_RR *next; int addr_count; int sess_count; SMTP_SESSION *session; int lookup_mx; unsigned domain_best_pref; MAI_HOSTADDR_STR hostaddr; if (cpp[1] == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; /* * Parse the destination. Default is to use the SMTP port. Look up * the address instead of the mail exchanger when a quoted host is * specified, or when DNS lookups are disabled. */ dest_buf = smtp_parse_destination(dest, def_service, &domain, &port); if (var_helpful_warnings && ntohs(port) == 465) { msg_info("CLIENT wrappermode (port smtps/465) is unimplemented"); msg_info("instead, send to (port submission/587) with STARTTLS"); } /* * Resolve an SMTP server. Skip mail exchanger lookups when a quoted * host is specified, or when DNS lookups are disabled. */ if (msg_verbose) msg_info("connecting to %s port %d", domain, ntohs(port)); if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) { if (ntohs(port) == IPPORT_SMTP) state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT; else state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT; lookup_mx = (var_disable_dns == 0 && *dest != '['); } else lookup_mx = 0; if (!lookup_mx) { addr_list = smtp_host_addr(domain, state->misc_flags, why); /* XXX We could be an MX host for this destination... */ } else { int i_am_mx = 0; addr_list = smtp_domain_addr(domain, state->misc_flags, why, &i_am_mx); /* If we're MX host, don't connect to non-MX backups. */ if (i_am_mx) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; } /* * Don't try fall-back hosts if mail loops to myself. That would just * make the problem worse. */ if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why)) state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP; /* * No early loop exit or we have a memory leak with dest_buf. */ if (addr_list) domain_best_pref = addr_list->pref; /* * When session caching is enabled, store the first good session for * this delivery request under the next-hop destination name. All * good sessions will be stored under their specific server IP * address. * * XXX Replace sites->argv by (lookup_mx, domain, port) triples so we * don't have to make clumsy ad-hoc copies and keep track of who * free()s the memory. * * XXX smtp_session_cache_destinations specifies domain names without * :port, because : is already used for maptype:mapname. Because of * this limitation we use the bare domain without the optional [] or * non-default TCP port. * * Opportunistic (a.k.a. on-demand) session caching on request by the * queue manager. This is turned temporarily when a destination has a * high volume of mail in the active queue. * * XXX Disable connection caching when sender-dependent authentication * is enabled. We must not send someone elses mail over an * authenticated connection, and we must not send mail that requires * authentication over a connection that wasn't authenticated. */ if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) { smtp_cache_policy(state, domain); if (state->misc_flags & SMTP_MISC_FLAG_CONN_STORE) SET_NEXTHOP_STATE(state, lookup_mx, domain, port); } /* * Delete visited cached hosts from the address list. * * Optionally search the connection cache by domain name or by primary * MX address before we try to create new connections. * * Enforce the MX session and MX address counts per next-hop or * fall-back destination. smtp_reuse_session() will truncate the * address list when either limit is reached. */ if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) { if (state->cache_used->used > 0) smtp_scrub_addr_list(state->cache_used, &addr_list); sess_count = addr_count = smtp_reuse_session(state, lookup_mx, domain, port, &addr_list, domain_best_pref); } else sess_count = addr_count = 0; /* * Connect to an SMTP server: create primary MX connections, and * reuse or create backup MX connections. * * At the start of an SMTP session, all recipients are unmarked. In the * course of an SMTP session, recipients are marked as KEEP (deliver * to alternate mail server) or DROP (remove from recipient list). At * the end of an SMTP session, weed out the recipient list. Unmark * any left-over recipients and try to deliver them to a backup mail * server. * * Cache the first good session under the next-hop destination name. * Cache all good sessions under their physical endpoint. * * Don't query the session cache for primary MX hosts. We already did * that in smtp_reuse_session(), and if any were found in the cache, * they were already deleted from the address list. */ for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) { next = addr->next; if (++addr_count == var_smtp_mxaddr_limit) next = 0; if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0 || addr->pref == domain_best_pref || dns_rr_to_pa(addr, &hostaddr) == 0 || !(session = smtp_reuse_addr(state, hostaddr.buf, port))) session = smtp_connect_addr(dest, addr, port, why, state->misc_flags); if ((state->session = session) != 0) { session->state = state; if (addr->pref == domain_best_pref) session->features |= SMTP_FEATURE_BEST_MX; /* Don't count handshake errors towards the session limit. */ if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) && next == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER; #ifdef USE_TLS /* Disable TLS when retrying after a handshake failure */ if (retry_plain) { if (session->tls_level >= TLS_LEV_ENCRYPT) msg_panic("Plain-text retry wrong for mandatory TLS"); session->tls_level = TLS_LEV_NONE; retry_plain = 0; } session->tls_nexthop = domain; /* for TLS_LEV_SECURE */ #endif if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0 && smtp_helo(state) != 0) { #ifdef USE_TLS /* * When an opportunistic TLS handshake fails, try the * same address again, with TLS disabled. See also the * RETRY_AS_PLAINTEXT macro. */ if ((retry_plain = session->tls_retry_plain) != 0) { --addr_count; next = addr; } #endif /* * When a TLS handshake fails, the stream is marked * "dead" to avoid further I/O over a broken channel. */ if (!THIS_SESSION_IS_DEAD && vstream_ferror(session->stream) == 0 && vstream_feof(session->stream) == 0) smtp_quit(state); } else { /* Do count delivery errors towards the session limit. */ if (++sess_count == var_smtp_mxsess_limit) next = 0; if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) && next == 0) state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER; smtp_xfer(state); } smtp_cleanup_session(state); } else { /* The reason already includes the IP address and TCP port. */ msg_info("%s", STR(why->reason)); } /* Insert: test if we must skip the remaining MX hosts. */ } dns_rr_free(addr_list); myfree(dest_buf); if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP) break; } /* * We still need to deliver, bounce or defer some left-over recipients: * either mail loops or some backup mail server was unavailable. */ if (SMTP_RCPT_LEFT(state) > 0) { /* * In case of a "no error" indication we make up an excuse: we did * find the host address, but we did not attempt to connect to it. * This can happen when the fall-back relay was already tried via a * cached connection, so that the address list scrubber left behind * an empty list. */ if (!SMTP_HAS_DSN(why)) { dsb_simple(why, "4.3.0", "server unavailable or unable to receive mail"); } /* * Pay attention to what could be configuration problems, and pretend * that these are recoverable rather than bouncing the mail. */ else if (!SMTP_HAS_SOFT_DSN(why) && (state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) { /* * The fall-back destination did not resolve as expected, or it * is refusing to talk to us, or mail for it loops back to us. */ if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) { msg_warn("%s configuration problem", VAR_SMTP_FALLBACK); vstring_strcpy(why->status, "4.3.5"); /* XXX Keep the diagnostic code and MTA. */ } /* * The next-hop relayhost did not resolve as expected, or it is * refusing to talk to us, or mail for it loops back to us. */ else if (strcmp(sites->argv[0], var_relayhost) == 0) { msg_warn("%s configuration problem", VAR_RELAYHOST); vstring_strcpy(why->status, "4.3.5"); /* XXX Keep the diagnostic code and MTA. */ } /* * Mail for the next-hop destination loops back to myself. Pass * the mail to the best_mx_transport or bounce it. */ else if (SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) { dsb_reset(why); /* XXX */ state->status = deliver_pass_all(MAIL_CLASS_PRIVATE, var_bestmx_transp, request); SMTP_RCPT_LEFT(state) = 0; /* XXX */ } } } /* * Cleanup. */ if (HAVE_NEXTHOP_STATE(state)) FREE_NEXTHOP_STATE(state); argv_free(sites); }