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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;
/*
* 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)
{
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 ((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)
{
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 ((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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