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+/*++
+/* NAME
+/* smtp_reuse 3
+/* SUMMARY
+/* SMTP session cache glue
+/* SYNOPSIS
+/* #include <smtp.h>
+/* #include <smtp_reuse.h>
+/*
+/* void smtp_save_session(state, name_key_flags, endp_key_flags)
+/* SMTP_STATE *state;
+/* int name_key_flags;
+/* int endp_key_flags;
+/*
+/* SMTP_SESSION *smtp_reuse_nexthop(state, name_key_flags)
+/* SMTP_STATE *state;
+/* int name_key_flags;
+/*
+/* SMTP_SESSION *smtp_reuse_addr(state, endp_key_flags)
+/* SMTP_STATE *state;
+/* int endp_key_flags;
+/* DESCRIPTION
+/* This module implements the SMTP client specific interface to
+/* the generic session cache infrastructure.
+/*
+/* The caller needs to include additional state in _key_flags
+/* to avoid false sharing of SASL-authenticated or TLS-authenticated
+/* sessions.
+/*
+/* smtp_save_session() stores the current session under the
+/* delivery request next-hop logical destination (if applicable)
+/* and under the remote server address. The SMTP_SESSION object
+/* is destroyed.
+/*
+/* smtp_reuse_nexthop() looks up a cached session by its
+/* delivery request next-hop destination, and verifies that
+/* the session is still alive. The restored session information
+/* includes the "best MX" bit and overrides the iterator dest,
+/* host and addr fields. The result is null in case of failure.
+/*
+/* smtp_reuse_addr() looks up a cached session by its server
+/* address, and verifies that the session is still alive.
+/* The restored session information does not include the "best
+/* MX" bit, and does not override the iterator dest, host and
+/* addr fields. The result is null in case of failure.
+/*
+/* Arguments:
+/* .IP state
+/* SMTP client state, including the current session, the original
+/* next-hop domain, etc.
+/* .IP name_key_flags
+/* Explicit declaration of context that should be used to look
+/* up a cached connection by its logical destination.
+/* See smtp_key(3) for details.
+/* .IP endp_key_flags
+/* Explicit declaration of context that should be used to look
+/* up a cached connection by its server address.
+/* See smtp_key(3) for details.
+/* 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
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <string.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <mymalloc.h>
+#include <vstream.h>
+#include <vstring.h>
+#include <htable.h>
+#include <stringops.h>
+
+/* Global library. */
+
+#include <scache.h>
+#include <mail_params.h>
+
+/* Application-specific. */
+
+#include <smtp.h>
+#include <smtp_reuse.h>
+
+ /*
+ * Key field delimiter, and place holder field value for
+ * unavailable/inapplicable information.
+ */
+#define SMTP_REUSE_KEY_DELIM_NA "\n*"
+
+/* smtp_save_session - save session under next-hop name and server address */
+
+void smtp_save_session(SMTP_STATE *state, int name_key_flags,
+ int endp_key_flags)
+{
+ SMTP_SESSION *session = state->session;
+ int fd;
+
+ /*
+ * Encode the delivery request next-hop destination, if applicable. Reuse
+ * storage that is also used for cache lookup queries.
+ *
+ * HAVE_SCACHE_REQUEST_NEXTHOP() controls whether or not to reuse or cache a
+ * connection by its delivery request next-hop destination. The idea is
+ * 1) to allow a reuse request to skip over bad hosts, and 2) to avoid
+ * caching a less-preferred connection when a more-preferred connection
+ * was possible.
+ */
+ if (HAVE_SCACHE_REQUEST_NEXTHOP(state))
+ smtp_key_prefix(state->dest_label, SMTP_REUSE_KEY_DELIM_NA,
+ state->iterator, name_key_flags);
+
+ /*
+ * Encode the physical endpoint name. Reuse storage that is also used for
+ * cache lookup queries.
+ */
+ smtp_key_prefix(state->endp_label, SMTP_REUSE_KEY_DELIM_NA,
+ state->iterator, endp_key_flags);
+
+ /*
+ * Passivate the SMTP_SESSION object, destroying the object in the
+ * process. Reuse storage that is also used for cache lookup results.
+ */
+ fd = smtp_session_passivate(session, state->dest_prop, state->endp_prop);
+ state->session = 0;
+
+ /*
+ * Save the session under the delivery request next-hop name, if
+ * applicable.
+ *
+ * XXX The logical to physical binding can be kept for as long as the DNS
+ * allows us to (but that could result in the caching of lots of unused
+ * bindings). The session should be idle for no more than 30 seconds or
+ * so.
+ */
+ if (HAVE_SCACHE_REQUEST_NEXTHOP(state))
+ scache_save_dest(smtp_scache, var_smtp_cache_conn,
+ STR(state->dest_label), STR(state->dest_prop),
+ STR(state->endp_label));
+
+ /*
+ * Save every good session under its physical endpoint address.
+ */
+ scache_save_endp(smtp_scache, var_smtp_cache_conn, STR(state->endp_label),
+ STR(state->endp_prop), fd);
+}
+
+/* smtp_reuse_common - common session reuse code */
+
+static SMTP_SESSION *smtp_reuse_common(SMTP_STATE *state, int fd,
+ const char *label)
+{
+ const char *myname = "smtp_reuse_common";
+ SMTP_ITERATOR *iter = state->iterator;
+ SMTP_SESSION *session;
+
+ if (msg_verbose) {
+ msg_info("%s: dest_prop='%s'", myname, STR(state->dest_prop));
+ msg_info("%s: endp_prop='%s'", myname, STR(state->endp_prop));
+ }
+
+ /*
+ * Re-activate the SMTP_SESSION object.
+ */
+ session = smtp_session_activate(fd, state->iterator, state->dest_prop,
+ state->endp_prop);
+ if (session == 0) {
+ msg_warn("%s: bad cached session attribute for %s", myname, label);
+ (void) close(fd);
+ return (0);
+ }
+ state->session = session;
+ session->state = state;
+
+ /*
+ * Send an RSET probe to verify that the session is still good.
+ */
+ if (smtp_rset(state) < 0
+ || (session->features & SMTP_FEATURE_RSET_REJECTED) != 0) {
+ smtp_session_free(session);
+ return (state->session = 0);
+ }
+
+ /*
+ * Avoid poor performance when TCP MSS > VSTREAM_BUFSIZE.
+ */
+ vstream_tweak_sock(session->stream);
+
+ /*
+ * Update the list of used cached addresses.
+ */
+ htable_enter(state->cache_used, STR(iter->addr), (void *) 0);
+
+ return (session);
+}
+
+/* smtp_reuse_nexthop - reuse session cached under nexthop name */
+
+SMTP_SESSION *smtp_reuse_nexthop(SMTP_STATE *state, int name_key_flags)
+{
+ const char *myname = "smtp_reuse_nexthop";
+ SMTP_SESSION *session;
+ int fd;
+
+ /*
+ * Look up the session by its logical name.
+ */
+ smtp_key_prefix(state->dest_label, SMTP_REUSE_KEY_DELIM_NA,
+ state->iterator, name_key_flags);
+ if (msg_verbose)
+ msg_info("%s: dest_label='%s'", myname, STR(state->dest_label));
+ if ((fd = scache_find_dest(smtp_scache, STR(state->dest_label),
+ state->dest_prop, state->endp_prop)) < 0)
+ return (0);
+
+ /*
+ * Re-activate the SMTP_SESSION object, and verify that the session is
+ * still good.
+ */
+ session = smtp_reuse_common(state, fd, STR(state->dest_label));
+ return (session);
+}
+
+/* smtp_reuse_addr - reuse session cached under numerical address */
+
+SMTP_SESSION *smtp_reuse_addr(SMTP_STATE *state, int endp_key_flags)
+{
+ const char *myname = "smtp_reuse_addr";
+ SMTP_SESSION *session;
+ int fd;
+
+ /*
+ * Address-based reuse is safe for security levels that require TLS
+ * certificate checks, as long as the current nexhop is included in the
+ * cache lookup key (COND_TLS_SMTP_KEY_FLAG_CUR_NEXTHOP). This is
+ * sufficient to prevent the reuse of a TLS-authenticated connection to
+ * the same MX hostname, IP address, and port, but for a different
+ * current nexthop destination with a different TLS policy.
+ */
+
+ /*
+ * Look up the session by its IP address. This means that we have no
+ * destination-to-address binding properties.
+ */
+ smtp_key_prefix(state->endp_label, SMTP_REUSE_KEY_DELIM_NA,
+ state->iterator, endp_key_flags);
+ if (msg_verbose)
+ msg_info("%s: endp_label='%s'", myname, STR(state->endp_label));
+ if ((fd = scache_find_endp(smtp_scache, STR(state->endp_label),
+ state->endp_prop)) < 0)
+ return (0);
+ VSTRING_RESET(state->dest_prop);
+ VSTRING_TERMINATE(state->dest_prop);
+
+ /*
+ * Re-activate the SMTP_SESSION object, and verify that the session is
+ * still good.
+ */
+ session = smtp_reuse_common(state, fd, STR(state->endp_label));
+
+ return (session);
+}
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