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-rw-r--r--src/smtp/smtp_connect.c1205
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diff --git a/src/smtp/smtp_connect.c b/src/smtp/smtp_connect.c
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+/*++
+/* NAME
+/* smtp_connect 3
+/* SUMMARY
+/* connect to SMTP/LMTP server and deliver
+/* SYNOPSIS
+/* #include "smtp.h"
+/*
+/* int smtp_connect(state)
+/* SMTP_STATE *state;
+/* DESCRIPTION
+/* This module implements SMTP/LMTP connection management and controls
+/* mail delivery.
+/*
+/* smtp_connect() attempts to establish an SMTP/LMTP session with a host
+/* that represents the destination domain, or with an optional fallback
+/* relay when {the destination cannot be found, or when all the
+/* destination servers are unavailable}. It skips over IP addresses
+/* that fail to complete the SMTP/LMTP handshake and tries to find
+/* an alternate server when an SMTP/LMTP session fails to deliver.
+/*
+/* This layer also controls what connections are retrieved from
+/* the connection cache, and what connections are saved to the cache.
+/*
+/* The destination is either a host (or domain) name or a numeric
+/* address. Symbolic or numeric service port information may be
+/* appended, separated by a colon (":"). In the case of LMTP,
+/* destinations may be specified as "unix:pathname", "inet:host"
+/* or "inet:host:port".
+/*
+/* With SMTP, the Internet domain name service is queried for mail
+/* exchanger hosts. Quote the domain name with `[' and `]' to
+/* suppress mail exchanger lookups.
+/*
+/* Numerical address information should always be quoted with `[]'.
+/* DIAGNOSTICS
+/* The delivery status is the result value.
+/* SEE ALSO
+/* smtp_proto(3) SMTP client protocol
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*
+/* Connection caching in cooperation with:
+/* Victor Duchovni
+/* Morgan Stanley
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <ctype.h>
+
+#ifndef IPPORT_SMTP
+#define IPPORT_SMTP 25
+#endif
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstream.h>
+#include <vstring.h>
+#include <split_at.h>
+#include <mymalloc.h>
+#include <inet_addr_list.h>
+#include <iostuff.h>
+#include <timed_connect.h>
+#include <stringops.h>
+#include <host_port.h>
+#include <sane_connect.h>
+#include <myaddrinfo.h>
+#include <sock_addr.h>
+#include <inet_proto.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+#include <own_inet_addr.h>
+#include <deliver_pass.h>
+#include <mail_error.h>
+#include <dsn_buf.h>
+#include <mail_addr.h>
+
+/* DNS library. */
+
+#include <dns.h>
+
+/* Application-specific. */
+
+#include <smtp.h>
+#include <smtp_addr.h>
+#include <smtp_reuse.h>
+
+ /*
+ * Forward declaration.
+ */
+static SMTP_SESSION *smtp_connect_sock(int, struct sockaddr *, int,
+ SMTP_ITERATOR *, DSN_BUF *,
+ int);
+
+/* smtp_connect_unix - connect to UNIX-domain address */
+
+static SMTP_SESSION *smtp_connect_unix(SMTP_ITERATOR *iter, DSN_BUF *why,
+ int sess_flags)
+{
+ const char *myname = "smtp_connect_unix";
+ struct sockaddr_un sock_un;
+ const char *addr = STR(iter->addr);
+ int len = strlen(addr);
+ int sock;
+
+ dsb_reset(why); /* Paranoia */
+
+ /*
+ * Sanity checks.
+ */
+ if (len >= (int) sizeof(sock_un.sun_path)) {
+ msg_warn("unix-domain name too long: %s", addr);
+ dsb_simple(why, "4.3.5", "Server configuration error");
+ return (0);
+ }
+
+ /*
+ * Initialize.
+ */
+ memset((void *) &sock_un, 0, sizeof(sock_un));
+ sock_un.sun_family = AF_UNIX;
+#ifdef HAS_SUN_LEN
+ sock_un.sun_len = len + 1;
+#endif
+ memcpy(sock_un.sun_path, addr, len + 1);
+
+ /*
+ * Create a client socket.
+ */
+ if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+ msg_fatal("%s: socket: %m", myname);
+
+ /*
+ * Connect to the server.
+ */
+ if (msg_verbose)
+ msg_info("%s: trying: %s...", myname, addr);
+
+ return (smtp_connect_sock(sock, (struct sockaddr *) &sock_un,
+ sizeof(sock_un), iter, why, sess_flags));
+}
+
+/* smtp_connect_addr - connect to explicit address */
+
+static SMTP_SESSION *smtp_connect_addr(SMTP_ITERATOR *iter, DSN_BUF *why,
+ int sess_flags)
+{
+ const char *myname = "smtp_connect_addr";
+ struct sockaddr_storage ss; /* remote */
+ struct sockaddr *sa = (struct sockaddr *) &ss;
+ SOCKADDR_SIZE salen = sizeof(ss);
+ MAI_HOSTADDR_STR hostaddr;
+ DNS_RR *addr = iter->rr;
+ unsigned port = iter->port;
+ int sock;
+ char *bind_addr;
+ char *bind_var;
+
+ dsb_reset(why); /* Paranoia */
+
+ /*
+ * Sanity checks.
+ */
+ if (dns_rr_to_sa(addr, port, sa, &salen) != 0) {
+ msg_warn("%s: skip address type %s: %m",
+ myname, dns_strtype(addr->type));
+ dsb_simple(why, "4.4.0", "network address conversion failed: %m");
+ return (0);
+ }
+
+ /*
+ * Initialize.
+ */
+ if ((sock = socket(sa->sa_family, SOCK_STREAM, 0)) < 0)
+ msg_fatal("%s: socket: %m", myname);
+
+ if (inet_windowsize > 0)
+ set_inet_windowsize(sock, inet_windowsize);
+
+ /*
+ * Allow the sysadmin to specify the source address, for example, as "-o
+ * smtp_bind_address=x.x.x.x" in the master.cf file.
+ */
+#ifdef HAS_IPV6
+ if (sa->sa_family == AF_INET6) {
+ bind_addr = var_smtp_bind_addr6;
+ bind_var = VAR_LMTP_SMTP(BIND_ADDR6);
+ } else
+#endif
+ if (sa->sa_family == AF_INET) {
+ bind_addr = var_smtp_bind_addr;
+ bind_var = VAR_LMTP_SMTP(BIND_ADDR);
+ } else
+ bind_var = bind_addr = "";
+ if (*bind_addr) {
+ int aierr;
+ struct addrinfo *res0;
+
+ if ((aierr = hostaddr_to_sockaddr(bind_addr, (char *) 0, 0, &res0)) != 0)
+ msg_fatal("%s: bad %s parameter: %s: %s",
+ myname, bind_var, bind_addr, MAI_STRERROR(aierr));
+ if (bind(sock, res0->ai_addr, res0->ai_addrlen) < 0)
+ msg_warn("%s: bind %s: %m", myname, bind_addr);
+ else if (msg_verbose)
+ msg_info("%s: bind %s", myname, bind_addr);
+ freeaddrinfo(res0);
+ }
+
+ /*
+ * When running as a virtual host, bind to the virtual interface so that
+ * the mail appears to come from the "right" machine address.
+ *
+ * XXX The IPv6 patch expands the null host (as client endpoint) and uses
+ * the result as the loopback address list.
+ */
+ else {
+ int count = 0;
+ struct sockaddr *own_addr = 0;
+ INET_ADDR_LIST *addr_list = own_inet_addr_list();
+ struct sockaddr_storage *s;
+
+ for (s = addr_list->addrs; s < addr_list->addrs + addr_list->used; s++) {
+ if (SOCK_ADDR_FAMILY(s) == sa->sa_family) {
+ if (count++ > 0)
+ break;
+ own_addr = SOCK_ADDR_PTR(s);
+ }
+ }
+ if (count == 1 && !sock_addr_in_loopback(own_addr)) {
+ if (bind(sock, own_addr, SOCK_ADDR_LEN(own_addr)) < 0) {
+ SOCKADDR_TO_HOSTADDR(own_addr, SOCK_ADDR_LEN(own_addr),
+ &hostaddr, (MAI_SERVPORT_STR *) 0, 0);
+ msg_warn("%s: bind %s: %m", myname, hostaddr.buf);
+ } else if (msg_verbose) {
+ SOCKADDR_TO_HOSTADDR(own_addr, SOCK_ADDR_LEN(own_addr),
+ &hostaddr, (MAI_SERVPORT_STR *) 0, 0);
+ msg_info("%s: bind %s", myname, hostaddr.buf);
+ }
+ }
+ }
+
+ /*
+ * Connect to the server.
+ */
+ if (msg_verbose)
+ msg_info("%s: trying: %s[%s] port %d...",
+ myname, STR(iter->host), STR(iter->addr), ntohs(port));
+
+ return (smtp_connect_sock(sock, sa, salen, iter, why, sess_flags));
+}
+
+/* smtp_connect_sock - connect a socket over some transport */
+
+static SMTP_SESSION *smtp_connect_sock(int sock, struct sockaddr *sa,
+ int salen,
+ SMTP_ITERATOR *iter,
+ DSN_BUF *why,
+ int sess_flags)
+{
+ int conn_stat;
+ int saved_errno;
+ VSTREAM *stream;
+ time_t start_time;
+ const char *name = STR(iter->host);
+ const char *addr = STR(iter->addr);
+ unsigned port = iter->port;
+
+ start_time = time((time_t *) 0);
+ if (var_smtp_conn_tmout > 0) {
+ non_blocking(sock, NON_BLOCKING);
+ conn_stat = timed_connect(sock, sa, salen, var_smtp_conn_tmout);
+ saved_errno = errno;
+ non_blocking(sock, BLOCKING);
+ errno = saved_errno;
+ } else {
+ conn_stat = sane_connect(sock, sa, salen);
+ }
+ if (conn_stat < 0) {
+ if (port)
+ dsb_simple(why, "4.4.1", "connect to %s[%s]:%d: %m",
+ name, addr, ntohs(port));
+ else
+ dsb_simple(why, "4.4.1", "connect to %s[%s]: %m", name, addr);
+ close(sock);
+ return (0);
+ }
+ stream = vstream_fdopen(sock, O_RDWR);
+
+ /*
+ * Avoid poor performance when TCP MSS > VSTREAM_BUFSIZE.
+ */
+ if (sa->sa_family == AF_INET
+#ifdef AF_INET6
+ || sa->sa_family == AF_INET6
+#endif
+ )
+ vstream_tweak_tcp(stream);
+
+ /*
+ * Bundle up what we have into a nice SMTP_SESSION object.
+ */
+ return (smtp_session_alloc(stream, iter, start_time, sess_flags));
+}
+
+/* smtp_parse_destination - parse host/port destination */
+
+static char *smtp_parse_destination(char *destination, char *def_service,
+ char **hostp, unsigned *portp)
+{
+ char *buf = mystrdup(destination);
+ char *service;
+ struct servent *sp;
+ char *protocol = "tcp"; /* XXX configurable? */
+ unsigned port;
+ const char *err;
+
+ if (msg_verbose)
+ msg_info("smtp_parse_destination: %s %s", destination, def_service);
+
+ /*
+ * Parse the host/port information. We're working with a copy of the
+ * destination argument so the parsing can be destructive.
+ */
+ if ((err = host_port(buf, hostp, (char *) 0, &service, def_service)) != 0)
+ msg_fatal("%s in server description: %s", err, destination);
+
+ /*
+ * Convert service to port number, network byte order.
+ */
+ if (alldig(service)) {
+ if ((port = atoi(service)) >= 65536 || port == 0)
+ msg_fatal("bad network port in destination: %s", destination);
+ *portp = htons(port);
+ } else {
+ if ((sp = getservbyname(service, protocol)) == 0)
+ msg_fatal("unknown service: %s/%s", service, protocol);
+ *portp = sp->s_port;
+ }
+ return (buf);
+}
+
+/* smtp_cleanup_session - clean up after using a session */
+
+static void smtp_cleanup_session(SMTP_STATE *state)
+{
+ DELIVER_REQUEST *request = state->request;
+ SMTP_SESSION *session = state->session;
+ int throttled;
+
+ /*
+ * Inform the postmaster of trouble.
+ *
+ * XXX Don't send notifications about errors while sending notifications.
+ */
+#define POSSIBLE_NOTIFICATION(sender) \
+ (*sender == 0 || strcmp(sender, mail_addr_double_bounce()) == 0)
+
+ if (session->history != 0
+ && (session->error_mask & name_mask(VAR_NOTIFY_CLASSES,
+ mail_error_masks,
+ var_notify_classes)) != 0
+ && POSSIBLE_NOTIFICATION(request->sender) == 0)
+ smtp_chat_notify(session);
+
+ /*
+ * When session caching is enabled, cache the first good session for this
+ * delivery request under the next-hop destination, and cache all good
+ * sessions under their server network address (destroying the session in
+ * the process).
+ *
+ * Caching under the next-hop destination name (rather than the fall-back
+ * destination) allows us to skip over non-responding primary or backup
+ * hosts. In fact, this is the only benefit of caching logical to
+ * physical bindings; caching a session under its own hostname provides
+ * no performance benefit, given the way smtp_connect() works.
+ */
+ throttled = THIS_SESSION_IS_THROTTLED; /* smtp_quit() may fail */
+ if (THIS_SESSION_IS_EXPIRED)
+ smtp_quit(state); /* also disables caching */
+ if (THIS_SESSION_IS_CACHED
+ /* Redundant tests for safety... */
+ && vstream_ferror(session->stream) == 0
+ && vstream_feof(session->stream) == 0) {
+ smtp_save_session(state, SMTP_KEY_MASK_SCACHE_DEST_LABEL,
+ SMTP_KEY_MASK_SCACHE_ENDP_LABEL);
+ } else {
+ smtp_session_free(session);
+ }
+ state->session = 0;
+
+ /*
+ * If this session was good, reset the scache next-hop destination, so
+ * that we won't cache connections to less-preferred servers under the
+ * same next-hop destination. Otherwise we could end up skipping over the
+ * available and more-preferred servers.
+ */
+ if (HAVE_SCACHE_REQUEST_NEXTHOP(state) && !throttled)
+ CLEAR_SCACHE_REQUEST_NEXTHOP(state);
+
+ /*
+ * Clean up the lists with todo and dropped recipients.
+ */
+ smtp_rcpt_cleanup(state);
+
+ /*
+ * Reset profiling info.
+ *
+ * XXX When one delivery request results in multiple sessions, the set-up
+ * and transmission latencies of the earlier sessions will count as
+ * connection set-up time for the later sessions.
+ *
+ * XXX On the other hand, when we first try to connect to one or more dead
+ * hosts before we reach a good host, then all that time must be counted
+ * as connection set-up time for the session with the good host.
+ *
+ * XXX So this set-up attribution problem exists only when we actually
+ * engage in a session, spend a lot of time delivering a message, find
+ * that it fails, and then connect to an alternate host.
+ */
+ memset((void *) &request->msg_stats.conn_setup_done, 0,
+ sizeof(request->msg_stats.conn_setup_done));
+ memset((void *) &request->msg_stats.deliver_done, 0,
+ sizeof(request->msg_stats.deliver_done));
+ request->msg_stats.reuse_count = 0;
+}
+
+static void smtp_cache_policy(SMTP_STATE *state, const char *dest)
+{
+ DELIVER_REQUEST *request = state->request;
+
+ state->misc_flags &= ~SMTP_MISC_FLAG_CONN_CACHE_MASK;
+
+ if (smtp_cache_dest && string_list_match(smtp_cache_dest, dest)) {
+ state->misc_flags |= SMTP_MISC_FLAG_CONN_CACHE_MASK;
+ } else if (var_smtp_cache_demand) {
+ if (request->flags & DEL_REQ_FLAG_CONN_LOAD)
+ state->misc_flags |= SMTP_MISC_FLAG_CONN_LOAD;
+ if (request->flags & DEL_REQ_FLAG_CONN_STORE)
+ state->misc_flags |= SMTP_MISC_FLAG_CONN_STORE;
+ }
+}
+
+/* smtp_connect_local - connect to local server */
+
+static void smtp_connect_local(SMTP_STATE *state, const char *path)
+{
+ const char *myname = "smtp_connect_local";
+ SMTP_ITERATOR *iter = state->iterator;
+ SMTP_SESSION *session;
+ DSN_BUF *why = state->why;
+
+ /*
+ * Do not silently ignore an unused setting.
+ */
+ if (*var_fallback_relay)
+ msg_warn("ignoring \"%s = %s\" setting for non-TCP connections",
+ VAR_LMTP_FALLBACK, var_fallback_relay);
+
+ /*
+ * It's too painful to weave this code into the SMTP connection
+ * management routine.
+ *
+ * Connection cache management is based on the UNIX-domain pathname, without
+ * the "unix:" prefix.
+ */
+ smtp_cache_policy(state, path);
+ if (state->misc_flags & SMTP_MISC_FLAG_CONN_CACHE_MASK)
+ SET_SCACHE_REQUEST_NEXTHOP(state, path);
+
+ /*
+ * Here we ensure that the iter->addr member refers to a copy of the
+ * UNIX-domain pathname, so that smtp_save_session() will cache the
+ * connection using the pathname as the physical endpoint name.
+ *
+ * We set dest=path for backwards compatibility.
+ */
+#define NO_PORT 0
+
+ SMTP_ITER_INIT(iter, path, var_myhostname, path, NO_PORT, state);
+
+ /*
+ * Opportunistic TLS for unix domain sockets does not make much sense,
+ * since the channel is private, mere encryption without authentication
+ * is just wasted cycles and opportunity for breakage. Since we are not
+ * willing to retry after TLS handshake failures here, we downgrade "may"
+ * no "none". Nothing is lost, and much waste is avoided.
+ *
+ * We don't know who is authenticating whom, so if a client cert is
+ * available, "encrypt" may be a sensible policy. Otherwise, we also
+ * downgrade "encrypt" to "none", this time just to avoid waste.
+ *
+ * We use smtp_reuse_nexthop() instead of smtp_reuse_addr(), so that we can
+ * reuse a SASL-authenticated connection (however unlikely this scenario
+ * may be). The smtp_reuse_addr() interface currently supports only reuse
+ * of SASL-unauthenticated connections.
+ */
+#ifdef USE_TLS
+ if (!smtp_tls_policy_cache_query(why, state->tls, iter)) {
+ msg_warn("TLS policy lookup error for %s/%s: %s",
+ STR(iter->host), STR(iter->addr), STR(why->reason));
+ return;
+ }
+#endif
+ if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
+ || (session = smtp_reuse_nexthop(state,
+ SMTP_KEY_MASK_SCACHE_DEST_LABEL)) == 0)
+ session = smtp_connect_unix(iter, why, state->misc_flags);
+ if ((state->session = session) != 0) {
+ session->state = state;
+#ifdef USE_TLS
+ session->tls_nexthop = var_myhostname; /* for TLS_LEV_SECURE */
+ if (state->tls->level == TLS_LEV_MAY) {
+ msg_warn("%s: opportunistic TLS encryption is not appropriate "
+ "for unix-domain destinations.", myname);
+ state->tls->level = TLS_LEV_NONE;
+ }
+#endif
+ /* All delivery errors bounce or defer. */
+ state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
+
+ /*
+ * When a TLS handshake fails, the stream is marked "dead" to avoid
+ * further I/O over a broken channel.
+ */
+ if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
+ && smtp_helo(state) != 0) {
+ if (!THIS_SESSION_IS_FORBIDDEN
+ && vstream_ferror(session->stream) == 0
+ && vstream_feof(session->stream) == 0)
+ smtp_quit(state);
+ } else {
+ smtp_xfer(state);
+ }
+
+ /*
+ * With opportunistic TLS disabled we don't expect to be asked to
+ * retry connections without TLS, and so we expect the final server
+ * flag to stay on.
+ */
+ if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_SERVER) == 0)
+ msg_panic("%s: unix-domain destination not final!", myname);
+ smtp_cleanup_session(state);
+ }
+
+ /*
+ * Cleanup.
+ */
+ if (HAVE_SCACHE_REQUEST_NEXTHOP(state))
+ CLEAR_SCACHE_REQUEST_NEXTHOP(state);
+}
+
+/* smtp_scrub_address_list - delete all cached addresses from list */
+
+static void smtp_scrub_addr_list(HTABLE *cached_addr, DNS_RR **addr_list)
+{
+ MAI_HOSTADDR_STR hostaddr;
+ DNS_RR *addr;
+ DNS_RR *next;
+
+ /*
+ * XXX Extend the DNS_RR structure with fields for the printable address
+ * and/or binary sockaddr representations, so that we can avoid repeated
+ * binary->string transformations for the same address.
+ */
+ for (addr = *addr_list; addr; addr = next) {
+ next = addr->next;
+ if (dns_rr_to_pa(addr, &hostaddr) == 0) {
+ msg_warn("cannot convert type %s record to printable address",
+ dns_strtype(addr->type));
+ continue;
+ }
+ if (htable_locate(cached_addr, hostaddr.buf))
+ *addr_list = dns_rr_remove(*addr_list, addr);
+ }
+}
+
+/* smtp_update_addr_list - common address list update */
+
+static void smtp_update_addr_list(DNS_RR **addr_list, const char *server_addr,
+ int session_count)
+{
+ DNS_RR *addr;
+ DNS_RR *next;
+ int aierr;
+ struct addrinfo *res0;
+
+ if (*addr_list == 0)
+ return;
+
+ /*
+ * Truncate the address list if we are not going to use it anyway.
+ */
+ if (session_count == var_smtp_mxsess_limit
+ || session_count == var_smtp_mxaddr_limit) {
+ dns_rr_free(*addr_list);
+ *addr_list = 0;
+ return;
+ }
+
+ /*
+ * Convert server address to internal form, and look it up in the address
+ * list.
+ *
+ * XXX smtp_reuse_session() breaks if we remove two or more adjacent list
+ * elements but do not truncate the list to zero length.
+ *
+ * XXX Extend the SMTP_SESSION structure with sockaddr information so that
+ * we can avoid repeated string->binary transformations for the same
+ * address.
+ */
+ if ((aierr = hostaddr_to_sockaddr(server_addr, (char *) 0, 0, &res0)) != 0) {
+ msg_warn("hostaddr_to_sockaddr %s: %s",
+ server_addr, MAI_STRERROR(aierr));
+ } else {
+ for (addr = *addr_list; addr; addr = next) {
+ next = addr->next;
+ if (DNS_RR_EQ_SA(addr, (struct sockaddr *) res0->ai_addr)) {
+ *addr_list = dns_rr_remove(*addr_list, addr);
+ break;
+ }
+ }
+ freeaddrinfo(res0);
+ }
+}
+
+/* smtp_reuse_session - try to use existing connection, return session count */
+
+static int smtp_reuse_session(SMTP_STATE *state, DNS_RR **addr_list,
+ int domain_best_pref)
+{
+ int session_count = 0;
+ DNS_RR *addr;
+ DNS_RR *next;
+ MAI_HOSTADDR_STR hostaddr;
+ SMTP_SESSION *session;
+ SMTP_ITERATOR *iter = state->iterator;
+ DSN_BUF *why = state->why;
+
+ /*
+ * First, search the cache by delivery request nexthop. We truncate the
+ * server address list when all the sessions for this destination are
+ * used up, to reduce the number of variables that need to be checked
+ * later.
+ *
+ * Note: connection reuse by delivery request nexthop restores the "best MX"
+ * bit.
+ *
+ * smtp_reuse_nexthop() clobbers the iterators's "dest" attribute. We save
+ * and restore it here, so that subsequent connections will use the
+ * proper nexthop information.
+ *
+ * We don't use TLS level info for nexthop-based connection cache storage
+ * keys. The combination of (service, nexthop, etc.) should be stable
+ * over the time range of interest, and the policy is still enforced on
+ * an individual connection to an MX host, before that connection is
+ * stored under a nexthop- or host-based storage key.
+ */
+#ifdef USE_TLS
+ smtp_tls_policy_dummy(state->tls);
+#endif
+ SMTP_ITER_SAVE_DEST(state->iterator);
+ if (*addr_list && SMTP_RCPT_LEFT(state) > 0
+ && HAVE_SCACHE_REQUEST_NEXTHOP(state)
+ && (session = smtp_reuse_nexthop(state, SMTP_KEY_MASK_SCACHE_DEST_LABEL)) != 0) {
+ session_count = 1;
+ smtp_update_addr_list(addr_list, STR(iter->addr), session_count);
+ if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
+ && *addr_list == 0)
+ state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
+ smtp_xfer(state);
+ smtp_cleanup_session(state);
+ }
+ SMTP_ITER_RESTORE_DEST(state->iterator);
+
+ /*
+ * Second, search the cache by primary MX address. Again, we use address
+ * list truncation so that we have to check fewer variables later.
+ *
+ * XXX This loop is safe because smtp_update_addr_list() either truncates
+ * the list to zero length, or removes at most one list element.
+ *
+ * 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 more precise control over reuse, the iterator should look up SASL and
+ * TLS policy as it evaluates mail exchangers in order, instead of
+ * relying on duplicate lookup request code in smtp_reuse(3) and
+ * smtp_session(3).
+ */
+ for (addr = *addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
+ if (addr->pref != domain_best_pref)
+ break;
+ next = addr->next;
+ 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 error 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. */
+ }
+#endif
+ if ((session = smtp_reuse_addr(state,
+ SMTP_KEY_MASK_SCACHE_ENDP_LABEL)) != 0) {
+ session->features |= SMTP_FEATURE_BEST_MX;
+ session_count += 1;
+ smtp_update_addr_list(addr_list, STR(iter->addr), session_count);
+ if (*addr_list == 0)
+ 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);
+ }
+ }
+ return (session_count);
+}
+
+/* smtp_connect_inet - establish network connection */
+
+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;
+ }
+
+ /*
+ * Do a null destination sanity check in case the primary destination is
+ * a list that consists of only separators.
+ */
+ sites = argv_split(nexthop, CHARS_COMMA_SP);
+ 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 connection caching is enabled, store the first good
+ * connection for this delivery request under the delivery request
+ * next-hop name. Good connections will also 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_SCACHE_REQUEST_NEXTHOP(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_SCACHE_REQUEST_NEXTHOP(state))
+ CLEAR_SCACHE_REQUEST_NEXTHOP(state);
+ argv_free(sites);
+}
+
+/* smtp_connect - establish SMTP connection */
+
+int smtp_connect(SMTP_STATE *state)
+{
+ DELIVER_REQUEST *request = state->request;
+ char *destination = request->nexthop;
+
+ /*
+ * All deliveries proceed along the same lines, whether they are over TCP
+ * or UNIX-domain sockets, and whether they use SMTP or LMTP: get a
+ * connection from the cache or create a new connection; deliver mail;
+ * update the connection cache or disconnect.
+ *
+ * The major differences appear at a higher level: the expansion from
+ * destination to address list, and whether to stop before we reach the
+ * end of that list.
+ */
+
+ /*
+ * With LMTP we have direct-to-host delivery only. The destination may
+ * have multiple IP addresses.
+ */
+ if (!smtp_mode) {
+ if (strncmp(destination, "unix:", 5) == 0) {
+ smtp_connect_local(state, destination + 5);
+ } else {
+ if (strncmp(destination, "inet:", 5) == 0)
+ destination += 5;
+ smtp_connect_inet(state, destination, var_smtp_tcp_port);
+ }
+ }
+
+ /*
+ * XXX We don't add support for "unix:" or "inet:" prefixes in SMTP
+ * destinations, because that would break compatibility with existing
+ * Postfix configurations that have a host with such a name.
+ */
+ else {
+ smtp_connect_inet(state, destination, var_smtp_tcp_port);
+ }
+
+ /*
+ * We still need to bounce or defer some left-over recipients: either
+ * (SMTP) mail loops or some server was unavailable.
+ *
+ * We could avoid this (and the "final server" complexity) by keeping one
+ * DSN structure per recipient in memory, by updating those in-memory
+ * structures with each delivery attempt, and by always flushing all
+ * deferred recipients at the end. We'd probably still want to bounce
+ * recipients immediately, so we'd end up with another chunk of code for
+ * defer logging only.
+ */
+ if (SMTP_RCPT_LEFT(state) > 0) {
+ state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER; /* XXX */
+ smtp_sess_fail(state);
+
+ /*
+ * Sanity check. Don't silently lose recipients.
+ */
+ smtp_rcpt_cleanup(state);
+ if (SMTP_RCPT_LEFT(state) > 0)
+ msg_panic("smtp_connect: left-over recipients");
+ }
+ return (state->status);
+}