xref: /src/external/ibm-public/postfix/dist/src/smtp/smtp_proto.c

/*	$NetBSD: smtp_proto.c,v 1.7 2026/05/09 18:49:20 christos Exp $	*/

/*++
/* NAME
/*	smtp_proto 3
/* SUMMARY
/*	client SMTP/LMTP protocol
/* SYNOPSIS
/*	#include "smtp.h"
/*
/*	int	smtp_helo(state)
/*	SMTP_STATE *state;
/*
/*	int	smtp_xfer(state)
/*	SMTP_STATE *state;
/*
/*	int	smtp_rset(state)
/*	SMTP_STATE *state;
/*
/*	int	smtp_quit(state)
/*	SMTP_STATE *state;
/* DESCRIPTION
/*	In the subsequent text, SMTP implies LMTP.
/*	This module implements the client side of the SMTP protocol.
/*
/*	smtp_helo() performs the initial handshake with the SMTP server.
/*	When TLS is enabled, this includes STARTTLS negotiations.
/*
/*	smtp_xfer() sends message envelope information followed by the
/*	message data, and finishes the SMTP conversation. These operations
/*	are combined in one function, in order to implement SMTP pipelining.
/*	Recipients are marked as "done" in the mail queue file when
/*	bounced or delivered. The message delivery status is updated
/*	accordingly.
/*
/*	smtp_rset() sends a single RSET command and waits for the
/*	response. In case of a negative reply it sets the
/*	CANT_RSET_THIS_SESSION flag.
/*
/*	smtp_quit() sends a single QUIT command and waits for the
/*	response if configured to do so. It always turns off connection
/*	caching.
/* DIAGNOSTICS
/*	smtp_helo(), smtp_xfer(), smtp_rset() and smtp_quit() return
/*	0 in case of success, -1 in case of failure. For smtp_xfer(),
/*	smtp_rset() and smtp_quit(), success means the ability to
/*	perform an SMTP conversation, not necessarily the ability
/*	to deliver mail, or the achievement of server happiness.
/*
/*	In case of a rejected or failed connection, a connection
/*	is marked as "bad, do not cache". Otherwise, connection
/*	caching may be turned off (without being marked "bad") at
/*	the discretion of the code that implements the individual
/*	protocol steps.
/*
/*	Warnings: corrupt message file. A corrupt message is marked
/*	as "corrupt" by changing its queue file permissions.
/* BUGS
/*	Some SMTP servers will abort when the number of recipients
/*	for one message exceeds their capacity. This behavior violates
/*	the SMTP protocol.
/*	The only way around this is to limit the number of recipients
/*	per transaction to an artificially-low value.
/* SEE ALSO
/*	smtp(3h) internal data structures
/*	smtp_chat(3) query/reply SMTP support
/*	smtp_trouble(3) error handlers
/* 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
/*
/*	Wietse Venema
/*	porcupine.org
/*
/*	Pipelining code in cooperation with:
/*	Jon Ribbens
/*	Oaktree Internet Solutions Ltd.,
/*	Internet House,
/*	Canal Basin,
/*	Coventry,
/*	CV1 4LY, United Kingdom.
/*
/*	Connection caching in cooperation with:
/*	Victor Duchovni
/*	Morgan Stanley
/*
/*	TLS support originally by:
/*	Lutz Jaenicke
/*	BTU Cottbus
/*	Allgemeine Elektrotechnik
/*	Universitaetsplatz 3-4
/*	D-03044 Cottbus, Germany
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/stat.h>
#include <sys/socket.h>			/* shutdown(2) */
#include <netinet/in.h>			/* ntohs() */
#include <string.h>
#include <unistd.h>
#include <stdlib.h>			/* 44BSD stdarg.h uses abort() */
#include <stdarg.h>
#include <time.h>

#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif

/* Utility library. */

#include <msg.h>
#include <vstring.h>
#include <vstream.h>
#include <vstring_vstream.h>
#include <stringops.h>
#include <mymalloc.h>
#include <iostuff.h>
#include <split_at.h>
#include <name_code.h>
#include <name_mask.h>

/* Global library. */

#include <mail_params.h>
#include <smtp_stream.h>
#include <mail_queue.h>
#include <recipient_list.h>
#include <deliver_request.h>
#include <defer.h>
#include <bounce.h>
#include <record.h>
#include <rec_type.h>
#include <off_cvt.h>
#include <mark_corrupt.h>
#include <quote_822_local.h>
#include <mail_proto.h>
#include <mime_state.h>
#include <ehlo_mask.h>
#include <maps.h>
#include <tok822.h>
#include <mail_addr_map.h>
#include <ext_prop.h>
#include <namadr_list.h>
#include <lex_822.h>
#include <dsn_mask.h>
#include <xtext.h>
#include <uxtext.h>
#include <smtputf8.h>
#if defined(USE_TLS) && defined(USE_TLSRPT)
#include <tlsrpt_wrapper.h>
#endif

/* Application-specific. */

#include "smtp.h"
#include "smtp_sasl.h"

 /*
  * Sender and receiver state. A session does not necessarily go through a
  * linear progression, but states are guaranteed to not jump backwards.
  * Normal sessions go from MAIL->RCPT->DATA->DOT->QUIT->LAST. The states
  * MAIL, RCPT, and DATA may also be followed by ABORT->QUIT->LAST.
  *
  * When connection caching is enabled, the QUIT state is suppressed. Normal
  * sessions proceed as MAIL->RCPT->DATA->DOT->LAST, while aborted sessions
  * end with ABORT->LAST. The connection is left open for a limited time. An
  * RSET probe should be sent before attempting to reuse an open connection
  * for a new transaction.
  *
  * The code to send an RSET probe is a special case with its own initial state
  * and with its own dedicated state transitions. The session proceeds as
  * RSET->LAST. This code is kept inside the main protocol engine for
  * consistent error handling and error reporting. It is not to be confused
  * with the code that sends RSET to abort a mail transaction in progress.
  *
  * The code to send QUIT without message delivery transaction jumps into the
  * main state machine. If this introduces complications, then we should
  * introduce a second QUIT state with its own dedicated state transitions,
  * just like we did for RSET probes.
  *
  * By default, the receiver skips the QUIT response. Some SMTP servers
  * disconnect after responding to ".", and some SMTP servers wait before
  * responding to QUIT.
  *
  * Client states that are associated with sending mail (up to and including
  * SMTP_STATE_DOT) must have smaller numerical values than the non-sending
  * states (SMTP_STATE_ABORT .. SMTP_STATE_LAST).
  */
#define SMTP_STATE_XFORWARD_NAME_ADDR 0
#define SMTP_STATE_XFORWARD_PROTO_HELO 1
#define SMTP_STATE_MAIL		2
#define SMTP_STATE_RCPT		3
#define SMTP_STATE_DATA		4
#define SMTP_STATE_DOT		5
#define SMTP_STATE_ABORT	6
#define SMTP_STATE_RSET		7
#define SMTP_STATE_QUIT		8
#define SMTP_STATE_LAST		9

int    *xfer_timeouts[SMTP_STATE_LAST] = {
    &var_smtp_xfwd_tmout,		/* name/addr */
    &var_smtp_xfwd_tmout,		/* helo/proto */
    &var_smtp_mail_tmout,
    &var_smtp_rcpt_tmout,
    &var_smtp_data0_tmout,
    &var_smtp_data2_tmout,
    &var_smtp_rset_tmout,
    &var_smtp_rset_tmout,
    &var_smtp_quit_tmout,
};

char   *xfer_states[SMTP_STATE_LAST] = {
    "sending XFORWARD name/address",
    "sending XFORWARD protocol/helo_name",
    "sending MAIL FROM",
    "sending RCPT TO",
    "sending DATA command",
    "sending end of data -- message may be sent more than once",
    "sending final RSET",
    "sending RSET probe",
    "sending QUIT",
};

char   *xfer_request[SMTP_STATE_LAST] = {
    "XFORWARD name/address command",
    "XFORWARD helo/protocol command",
    "MAIL FROM command",
    "RCPT TO command",
    "DATA command",
    "end of DATA command",
    "final RSET command",
    "RSET probe",
    "QUIT command",
};

 /*
  * Note: MIME downgrade never happens for mail that must be delivered with
  * SMTPUTF8 (the sender requested SMTPUTF8, AND the delivery request
  * involves at least one UTF-8 envelope address or header value.
  */
#define SMTP_MIME_DOWNGRADE(session, request) \
    (var_disable_mime_oconv == 0 \
     && (session->features & SMTP_FEATURE_8BITMIME) == 0 \
     && strcmp(request->encoding, MAIL_ATTR_ENC_7BIT) != 0)

#ifdef USE_TLS

static int smtp_start_tls(SMTP_STATE *);

#endif

 /*
  * Call-back information for header/body checks. We don't provide call-backs
  * for actions that change the message delivery time or destination.
  */
static void smtp_hbc_logger(void *, const char *, const char *, const char *, const char *);
static void smtp_text_out(void *, int, const char *, ssize_t, off_t);

HBC_CALL_BACKS smtp_hbc_callbacks[1] = {
    smtp_hbc_logger,
    smtp_text_out,
};

static int smtp_vrfy_tgt;

/* smtp_vrfy_init - initialize */

void    smtp_vrfy_init(void)
{
    static const NAME_CODE vrfy_init_table[] = {
	SMTP_VRFY_TGT_RCPT, SMTP_STATE_RCPT,
	SMTP_VRFY_TGT_DATA, SMTP_STATE_DATA,
	0,
    };

    if ((smtp_vrfy_tgt = name_code(vrfy_init_table, NAME_CODE_FLAG_NONE,
				   var_smtp_vrfy_tgt)) == 0)
	msg_fatal("bad protocol stage: \"%s = %s\"",
		  VAR_SMTP_VRFY_TGT, var_smtp_vrfy_tgt);
}

/* smtp_helo - perform initial handshake with SMTP server */

int     smtp_helo(SMTP_STATE *state)
{
    const char *myname = "smtp_helo";
    SMTP_SESSION *session = state->session;
    DELIVER_REQUEST *request = state->request;
    SMTP_ITERATOR *iter = state->iterator;
    SMTP_RESP *resp;
    SMTP_RESP fake;
    int     except;
    char   *lines;
    char   *words;
    char   *word;
    int     n;
    static const NAME_CODE xforward_features[] = {
	XFORWARD_NAME, SMTP_FEATURE_XFORWARD_NAME,
	XFORWARD_ADDR, SMTP_FEATURE_XFORWARD_ADDR,
	XFORWARD_PORT, SMTP_FEATURE_XFORWARD_PORT,
	XFORWARD_PROTO, SMTP_FEATURE_XFORWARD_PROTO,
	XFORWARD_HELO, SMTP_FEATURE_XFORWARD_HELO,
	XFORWARD_IDENT, SMTP_FEATURE_XFORWARD_IDENT,
	XFORWARD_DOMAIN, SMTP_FEATURE_XFORWARD_DOMAIN,
	0, 0,
    };
    const char *ehlo_words;
    int     discard_mask;
    static const NAME_MASK pix_bug_table[] = {
	PIX_BUG_DISABLE_ESMTP, SMTP_FEATURE_PIX_NO_ESMTP,
	PIX_BUG_DELAY_DOTCRLF, SMTP_FEATURE_PIX_DELAY_DOTCRLF,
	0,
    };
    const char *pix_bug_words;
    const char *pix_bug_source;
    int     pix_bug_mask;

#ifdef USE_TLS
    int     saved_features = session->features;
    int     tls_helo_status;

#endif
    const char *NOCLOBBER where;

    /*
     * Skip the plaintext SMTP handshake when connecting in SMTPS mode.
     */
#ifdef USE_TLS
    if (var_smtp_tls_wrappermode
	&& (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) == 0) {
	/* XXX Mix-up of per-session and per-request flags. */
	state->misc_flags |= SMTP_MISC_FLAG_IN_STARTTLS;
	smtp_stream_setup(state->session->stream, var_smtp_starttls_tmout,
			  var_smtp_req_deadline, 0);
	tls_helo_status = smtp_start_tls(state);
	state->misc_flags &= ~SMTP_MISC_FLAG_IN_STARTTLS;
	return (tls_helo_status);
    }
#endif

    /*
     * Prepare for disaster.
     */
    smtp_stream_setup(state->session->stream, var_smtp_helo_tmout,
		      var_smtp_req_deadline, 0);
    if ((except = vstream_setjmp(state->session->stream)) != 0)
	return (smtp_stream_except(state, except, where));

    /*
     * If not recursing after STARTTLS, examine the server greeting banner
     * and decide if we are going to send EHLO as the next command.
     */
    if (var_smtp_tls_wrappermode
	|| (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) == 0) {

	/*
	 * Read and parse the server's SMTP greeting banner.
	 */
	where = "receiving the initial server greeting";
	switch ((resp = smtp_chat_resp(session))->code / 100) {
	case 2:
	    break;
	case 5:
	    if (var_smtp_skip_5xx_greeting)
		STR(resp->dsn_buf)[0] = '4';
	    /* FALLTHROUGH */
	default:
	    return (smtp_site_fail(state, STR(iter->host), resp,
				   "host %s refused to talk to me: %s",
				   session->namaddr,
				   translit(resp->str, "\n", " ")));
	}

	/*
	 * If the policy table specifies a bogus TLS security level, fail
	 * now.
	 */
#ifdef USE_TLS
	if (state->tls->level == TLS_LEV_INVALID)
	    /* Warning is already logged. */
	    return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				   SMTP_RESP_FAKE(&fake, "4.7.0"),
				   "client TLS configuration problem"));
#endif

	/*
	 * XXX Some PIX firewall versions require flush before ".<CR><LF>" so
	 * it does not span a packet boundary. This hurts performance so it
	 * is not on by default.
	 */
	if (resp->str[strspn(resp->str, "20 *\t\n")] == 0) {
	    /* Best effort only. Ignore errors. */
	    if (smtp_pix_bug_maps != 0
		&& (pix_bug_words =
		    maps_find(smtp_pix_bug_maps,
			      STR(iter->addr), 0)) != 0) {
		pix_bug_source = VAR_LMTP_SMTP(PIX_BUG_MAPS);
	    } else {
		pix_bug_words = var_smtp_pix_bug_words;
		pix_bug_source = VAR_LMTP_SMTP(PIX_BUG_WORDS);
	    }
	    if (*pix_bug_words) {
		pix_bug_mask = name_mask_opt(pix_bug_source, pix_bug_table,
					     pix_bug_words,
				     NAME_MASK_ANY_CASE | NAME_MASK_IGNORE);
		if ((pix_bug_mask & SMTP_FEATURE_PIX_DELAY_DOTCRLF)
		    && request->msg_stats.incoming_arrival.tv_sec
		    > vstream_ftime(state->session->stream) - var_smtp_pix_thresh)
		    pix_bug_mask &= ~SMTP_FEATURE_PIX_DELAY_DOTCRLF;
		msg_info("%s: enabling PIX workarounds: %s for %s",
			 request->queue_id,
			 str_name_mask("pix workaround bitmask",
				       pix_bug_table, pix_bug_mask),
			 session->namaddrport);
		session->features |= pix_bug_mask;
	    }
	}

	/*
	 * See if we are talking to ourself. This should not be possible with
	 * the way we implement DNS lookups. However, people are known to
	 * sometimes screw up the naming service. And, mailer loops are still
	 * possible when our own mailer routing tables are mis-configured.
	 */
	words = resp->str;
	(void) mystrtok(&words, "- \t\n");
	for (n = 0; (word = mystrtok(&words, " \t\n")) != 0; n++) {
	    if (n == 0 && strcasecmp(word, var_myhostname) == 0) {
		if (state->misc_flags & SMTP_MISC_FLAG_LOOP_DETECT)
		    msg_warn("host %s greeted me with my own hostname %s",
			     session->namaddrport, var_myhostname);
	    } else if (strcasecmp(word, "ESMTP") == 0)
		session->features |= SMTP_FEATURE_ESMTP;
	}
	if (smtp_mode) {
	    if (var_smtp_always_ehlo
		&& (session->features & SMTP_FEATURE_PIX_NO_ESMTP) == 0)
		session->features |= SMTP_FEATURE_ESMTP;
	    if (var_smtp_never_ehlo
		|| (session->features & SMTP_FEATURE_PIX_NO_ESMTP) != 0)
		session->features &= ~SMTP_FEATURE_ESMTP;
	} else {
	    session->features |= SMTP_FEATURE_ESMTP;
	}
    }

    /*
     * If recursing after STARTTLS, there is no server greeting banner.
     * Always send EHLO as the next command.
     */
    else {
	session->features |= SMTP_FEATURE_ESMTP;
    }

    /*
     * Return the compliment. Fall back to SMTP if our ESMTP recognition
     * heuristic failed.
     */
    if (smtp_mode) {
	where = "performing the EHLO handshake";
	if (session->features & SMTP_FEATURE_ESMTP) {
	    smtp_chat_cmd(session, "EHLO %s", var_smtp_helo_name);
	    if ((resp = smtp_chat_resp(session))->code / 100 != 2) {
		if (resp->code == 421)
		    return (smtp_site_fail(state, STR(iter->host), resp,
					"host %s refused to talk to me: %s",
					   session->namaddr,
					   translit(resp->str, "\n", " ")));
		else
		    session->features &= ~SMTP_FEATURE_ESMTP;
	    }
#ifdef USE_TLSRPT
	    if (state->tlsrpt
		&& (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) == 0)
		smtp_tlsrpt_set_ehlo_resp(state, resp->str);
#endif
	}
	if ((session->features & SMTP_FEATURE_ESMTP) == 0) {
	    where = "performing the HELO handshake";
	    smtp_chat_cmd(session, "HELO %s", var_smtp_helo_name);
	    if ((resp = smtp_chat_resp(session))->code / 100 != 2)
		return (smtp_site_fail(state, STR(iter->host), resp,
				       "host %s refused to talk to me: %s",
				       session->namaddr,
				       translit(resp->str, "\n", " ")));
#ifdef USE_TLSRPT
	    if (state->tlsrpt)
		trw_set_ehlo_resp(state->tlsrpt, resp->str);
#endif
	}
    } else {
	where = "performing the LHLO handshake";
	smtp_chat_cmd(session, "LHLO %s", var_smtp_helo_name);
	if ((resp = smtp_chat_resp(session))->code / 100 != 2)
	    return (smtp_site_fail(state, STR(iter->host), resp,
				   "host %s refused to talk to me: %s",
				   session->namaddr,
				   translit(resp->str, "\n", " ")));
    }

    /*
     * No early returns allowed, to ensure consistent handling of TLS and
     * SASL policies.
     */
    if (session->features & SMTP_FEATURE_ESMTP) {

	/*
	 * Determine what server EHLO keywords to ignore, typically to avoid
	 * inter-operability problems.
	 */
	if (smtp_ehlo_dis_maps == 0
	    || (ehlo_words = maps_find(smtp_ehlo_dis_maps,
				       STR(iter->addr), 0)) == 0)
	    ehlo_words = var_smtp_ehlo_dis_words;
	if (smtp_ehlo_dis_maps && smtp_ehlo_dis_maps->error) {
	    msg_warn("%s: %s map lookup error for %s",
		     session->state->request->queue_id,
		     smtp_ehlo_dis_maps->title, STR(iter->addr));
	    vstream_longjmp(session->stream, SMTP_ERR_DATA);
	}
	discard_mask = ehlo_mask(ehlo_words);
	if (discard_mask && !(discard_mask & EHLO_MASK_SILENT))
	    msg_info("discarding EHLO keywords: %s",
		     str_ehlo_mask(discard_mask));

	/*
	 * Pick up some useful features offered by the SMTP server. XXX Until
	 * we have a portable routine to convert from string to off_t with
	 * proper overflow detection, ignore the message size limit
	 * advertised by the SMTP server. Otherwise, we might do the wrong
	 * thing when the server advertises a really huge message size limit.
	 *
	 * XXX Allow for "code (SP|-) ehlo-keyword (SP|=) ehlo-param...",
	 * because MicroSoft implemented AUTH based on an old draft.
	 */
	lines = resp->str;
	for (n = 0; (words = mystrtok(&lines, "\n")) != 0; /* see below */ ) {
	    if (mystrtok(&words, "- ")
		&& (word = mystrtok(&words, " \t=")) != 0) {
		if (n == 0) {
		    if (session->helo != 0)
			myfree(session->helo);

		    /*
		     * XXX: Keep the original case: we don't expect a single
		     * SMTP server to randomly change the case of its helo
		     * response. If different capitalization is detected, we
		     * should assume disjoint TLS caches.
		     */
		    session->helo = mystrdup(word);
		    if (strcasecmp(word, var_myhostname) == 0
			&& (state->misc_flags & SMTP_MISC_FLAG_LOOP_DETECT) != 0) {
			msg_warn("host %s replied to HELO/EHLO"
				 " with my own hostname %s",
				 session->namaddrport, var_myhostname);
			if (session->features & SMTP_FEATURE_BEST_MX)
			    return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
					     SMTP_RESP_FAKE(&fake, "5.4.6"),
					 "mail for %s loops back to myself",
						   request->nexthop));
			else
			    return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
					     SMTP_RESP_FAKE(&fake, "4.4.6"),
					 "mail for %s loops back to myself",
						   request->nexthop));
		    }
		} else if (strcasecmp(word, "8BITMIME") == 0) {
		    if ((discard_mask & EHLO_MASK_8BITMIME) == 0)
			session->features |= SMTP_FEATURE_8BITMIME;
		} else if (strcasecmp(word, "PIPELINING") == 0) {
		    if ((discard_mask & EHLO_MASK_PIPELINING) == 0)
			session->features |= SMTP_FEATURE_PIPELINING;
		} else if (strcasecmp(word, "XFORWARD") == 0) {
		    if ((discard_mask & EHLO_MASK_XFORWARD) == 0)
			while ((word = mystrtok(&words, " \t")) != 0)
			    session->features |=
				name_code(xforward_features,
					  NAME_CODE_FLAG_NONE, word);
		} else if (strcasecmp(word, "SIZE") == 0) {
		    if ((discard_mask & EHLO_MASK_SIZE) == 0) {
			session->features |= SMTP_FEATURE_SIZE;
			if ((word = mystrtok(&words, " \t")) != 0) {
			    if (!alldig(word))
				msg_warn("bad EHLO SIZE limit \"%s\" from %s",
					 word, session->namaddrport);
			    else
				session->size_limit = off_cvt_string(word);
			}
		    }
#ifdef USE_TLS
		} else if (strcasecmp(word, "STARTTLS") == 0) {
		    /* Ignored later if we already sent STARTTLS. */
		    if ((discard_mask & EHLO_MASK_STARTTLS) == 0)
			session->features |= SMTP_FEATURE_STARTTLS;
		} else if (strcasecmp(word, "REQUIRETLS") == 0) {
		    if ((discard_mask & EHLO_MASK_REQTLS) == 0
			&& (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS))
			session->features |= SMTP_FEATURE_REQTLS;
#endif
#ifdef USE_SASL_AUTH
		} else if (var_smtp_sasl_enable
			   && strcasecmp(word, "AUTH") == 0) {
		    if ((discard_mask & EHLO_MASK_AUTH) == 0)
			smtp_sasl_helo_auth(session, words);
#endif
		} else if (strcasecmp(word, "DSN") == 0) {
		    if ((discard_mask & EHLO_MASK_DSN) == 0)
			session->features |= SMTP_FEATURE_DSN;
		} else if (strcasecmp(word, "SMTPUTF8") == 0) {
		    if ((discard_mask & EHLO_MASK_SMTPUTF8) == 0)
			session->features |= SMTP_FEATURE_SMTPUTF8;
		}
		n++;
	    }
	}
    }
    if (msg_verbose)
	msg_info("server features: 0x%x size %.0f",
		 session->features, (double) session->size_limit);

    /*
     * Require that the server supports SMTPUTF8 when delivery requires
     * SMTPUTF8.
     *
     * Fix 20140706: moved this before negotiating TLS, AUTH, and so on.
     *
     * Fix 20250824: try multiple servers before giving up.
     *
     * Fix 20250911: do not cache this session because it does not satisfy the
     * requirement expressed in the cache storage key.
     */
    if ((session->features & SMTP_FEATURE_SMTPUTF8) == 0
	&& DELIVERY_REQUIRES_SMTPUTF8(request))
	return (smtp_misc_fail(state, SMTP_MISC_FAIL_DONT_CACHE
			       | SMTP_MISC_FAIL_SOFT_NON_FINAL,
			       DSN_BY_LOCAL_MTA,
			       SMTP_RESP_FAKE(&fake, "5.6.7"),
			       "message requires SMTPUTF8, but no "
			       "server was found that supports "
			       "SMTPUTF8. The last attempted server "
			       "was %s", session->namaddr));

    /*
     * Fix 20140706: don't do silly things when the remote server announces
     * SMTPUTF8 but not 8BITMIME support. Our primary mission is to deliver
     * mail, not to force people into compliance.
     */
    if ((session->features & SMTP_FEATURE_SMTPUTF8) != 0
	&& (session->features & SMTP_FEATURE_8BITMIME) == 0) {
	msg_info("host %s offers SMTPUTF8 support, but not 8BITMIME",
		 session->namaddr);
	session->features |= SMTP_FEATURE_8BITMIME;
    }

    /*
     * Require that the server announces REQUIRETLS when the sender requested
     * REQUIRETLS. Return the message as undeliverable only when there are no
     * more alternative MX hosts. With opportunistic REQUIRETLS, only log
     * that the server does not offer REQUIRETLS.
     */
#ifdef USE_TLS
    if (state->reqtls_level > SMTP_REQTLS_POLICY_ACT_DISABLE
	&& (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) != 0) {
	if ((session->features & SMTP_FEATURE_REQTLS) != 0) {
	    if (state->tls_stats)
		smtp_tls_stat_decide_reqtls(state->tls_stats,
				 TLS_CERT_IS_MATCHED(session->tls_context) ?
					    SMTP_TLS_STAT_NAME_REQTLS :
					    SMTP_TLS_STAT_NAME_NOCMATCH,
					    POL_STAT_COMPLIANT);
	} else if (state->reqtls_level == SMTP_REQTLS_POLICY_ACT_ENFORCE) {
	    if (state->tls_stats)
		smtp_tls_stat_decide_reqtls(state->tls_stats,
					    SMTP_TLS_STAT_NAME_NONE,
					    POL_STAT_VIOLATION);
	    return (smtp_misc_fail(state, SMTP_MISC_FAIL_DONT_CACHE
				   | SMTP_MISC_FAIL_SOFT_NON_FINAL,
				   DSN_BY_LOCAL_MTA,
				   SMTP_RESP_FAKE(&fake, "5.7.30"),
				   "Sender requested REQUIRETLS, "
				   "but no server was found that "
				   "supports REQUIRETLS. The last "
				   "attempted server was %s",
				   session->namaddr));
	} else {
	    if (state->tls_stats)
		smtp_tls_stat_decide_reqtls(state->tls_stats,
					    SMTP_TLS_STAT_NAME_NONE,
					    POL_STAT_COMPLIANT);
	    msg_info("%s: Sender requested REQUIRETLS, but REQUIRETLS "
		     "support was not offered by host %s",
		     request->queue_id, session->namaddr);
	}
    }

    /*
     * TODO(wietse) Maybe log servers that announce REQUIRETLS and whether
     * the connection is authenticated?
     */
#endif

    /*
     * We use SMTP command pipelining if the server said it supported it.
     * Since we use blocking I/O, RFC 2197 says that we should inspect the
     * TCP window size and not send more than this amount of information.
     * Unfortunately this information is unavailable using the sockets
     * interface. However, we *can* get the TCP send buffer size on the local
     * TCP/IP stack. We should be able to fill this buffer without being
     * blocked, and then the kernel will effectively do non-blocking I/O for
     * us by automatically writing out the contents of its send buffer while
     * we are reading in the responses. In addition to TCP buffering we have
     * to be aware of application-level buffering by the vstream module,
     * which is limited to a couple kbytes.
     *
     * XXX No need to do this before and after STARTTLS, but it's not a big deal
     * if we do.
     *
     * XXX When TLS is turned on, the SMTP-level writes will be encapsulated as
     * TLS messages. Thus, the TCP-level payload will be larger than the
     * SMTP-level payload. This has implications for the PIPELINING engine.
     *
     * To avoid deadlock, the PIPELINING engine needs to request a TCP send
     * buffer size that can hold the unacknowledged commands plus the TLS
     * encapsulation overhead.
     *
     * The PIPELINING engine keeps the unacknowledged command size <= the
     * default VSTREAM buffer size (to avoid small-write performance issues
     * when the VSTREAM buffer size is at its default size). With a default
     * VSTREAM buffer size of 4096 there is no reason to increase the
     * unacknowledged command size as the TCP MSS increases. It's safer to
     * spread the remote SMTP server's recipient processing load over time,
     * than dumping a very large recipient list all at once.
     *
     * For TLS encapsulation overhead we make a conservative guess: take the
     * current protocol overhead of ~40 bytes, double the number for future
     * proofing (~80 bytes), then round up the result to the nearest power of
     * 2 (128 bytes). Plus, be prepared for worst-case compression that
     * expands data by 1 kbyte, so that the worst-case SMTP payload per TLS
     * message becomes 15 kbytes.
     */
#define PIPELINING_BUFSIZE	VSTREAM_BUFSIZE
#ifdef USE_TLS
#define TLS_WORST_PAYLOAD	16384
#define TLS_WORST_COMP_OVERHD	1024
#define TLS_WORST_PROTO_OVERHD	128
#define TLS_WORST_SMTP_PAYLOAD	(TLS_WORST_PAYLOAD - TLS_WORST_COMP_OVERHD)
#define TLS_WORST_TOTAL_OVERHD	(TLS_WORST_COMP_OVERHD + TLS_WORST_PROTO_OVERHD)
#endif

    if (session->features & SMTP_FEATURE_PIPELINING) {
	SOCKOPT_SIZE optlen;
	int     tcp_bufsize;
	int     enc_overhead = 0;

	optlen = sizeof(tcp_bufsize);
	if (getsockopt(vstream_fileno(session->stream), SOL_SOCKET,
		       SO_SNDBUF, (char *) &tcp_bufsize, &optlen) < 0)
	    msg_fatal("%s: getsockopt: %m", myname);
#ifdef USE_TLS
	if (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS)
	    enc_overhead +=
		(1 + (PIPELINING_BUFSIZE - 1)
		 / TLS_WORST_SMTP_PAYLOAD) * TLS_WORST_TOTAL_OVERHD;
#endif
	if (tcp_bufsize < PIPELINING_BUFSIZE + enc_overhead) {
	    tcp_bufsize = PIPELINING_BUFSIZE + enc_overhead;
	    if (setsockopt(vstream_fileno(session->stream), SOL_SOCKET,
			   SO_SNDBUF, (char *) &tcp_bufsize, optlen) < 0)
		msg_fatal("%s: setsockopt: %m", myname);
	}
	if (msg_verbose)
	    msg_info("Using %s PIPELINING, TCP send buffer size is %d, "
		     "PIPELINING buffer size is %d",
		     smtp_mode ? "ESMTP" : "LMTP",
		     tcp_bufsize, PIPELINING_BUFSIZE);
    }
#ifdef USE_TLS

    /*
     * Skip this part if we already sent STARTTLS.
     */
    if ((state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) == 0) {

	/*
	 * Optionally log unused STARTTLS opportunities.
	 */
	if ((session->features & SMTP_FEATURE_STARTTLS) &&
	    var_smtp_tls_note_starttls_offer &&
	    state->tls->level <= TLS_LEV_NONE)
	    msg_info("Host offered STARTTLS: [%s]", STR(iter->host));

	/*
	 * Decide whether or not to send STARTTLS.
	 */
	if ((session->features & SMTP_FEATURE_STARTTLS) != 0
	    && smtp_tls_ctx != 0 && state->tls->level >= TLS_LEV_MAY) {

	    /*
	     * Prepare for disaster.
	     */
	    smtp_stream_setup(state->session->stream, var_smtp_starttls_tmout,
			      var_smtp_req_deadline, 0);
	    if ((except = vstream_setjmp(state->session->stream)) != 0)
		return (smtp_stream_except(state, except,
					"receiving the STARTTLS response"));

	    /*
	     * Send STARTTLS. Recurse when the server accepts STARTTLS, after
	     * resetting the SASL and EHLO features lists.
	     *
	     * Reset the SASL mechanism list to avoid spurious warnings.
	     *
	     * Use the smtp_sasl_tls_security_options feature to allow SASL
	     * mechanisms that may not be allowed with plain-text
	     * connections.
	     */
	    smtp_chat_cmd(session, "STARTTLS");
	    if ((resp = smtp_chat_resp(session))->code / 100 == 2) {
#ifdef USE_SASL_AUTH
		if (session->features & SMTP_FEATURE_AUTH)
		    smtp_sasl_cleanup(session);
#endif
		session->features = saved_features;
		/* XXX Mix-up of per-session and per-request flags. */
		state->misc_flags |= SMTP_MISC_FLAG_IN_STARTTLS;
		tls_helo_status = smtp_start_tls(state);
		state->misc_flags &= ~SMTP_MISC_FLAG_IN_STARTTLS;
		return (tls_helo_status);
	    }
#ifdef USE_TLSRPT
	    if (state->tlsrpt)
		trw_report_failure(state->tlsrpt,
				   TLSRPT_STARTTLS_NOT_SUPPORTED,
				    /* additional_info= */ (char *) 0,
				    /* failure_reason= */ (char *) 0);
#endif

	    /*
	     * Give up if we must use TLS but the server rejects STARTTLS
	     * although support for it was announced in the EHLO response.
	     *
	     * When the sender requested REQUIRETLS, and the REQUIRETLS policy
	     * requires TLS, return the message as undeliverable only when
	     * there are no more alternative MX hosts.
	     */
	    session->features &= ~SMTP_FEATURE_STARTTLS;
	    if (TLS_REQUIRED_BY_SECURITY_LEVEL(state->tls->level)
		|| TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level)) {
		/* Before returning, decide all relevant policy status info. */
		if (TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level)) {
		    if (state->tls_stats)
			smtp_tls_stat_decide_reqtls(state->tls_stats,
						 SMTP_TLS_STAT_NAME_NOSTTLS,
						    POL_STAT_VIOLATION);
		}
		if (TLS_REQUIRED_BY_SECURITY_LEVEL(state->tls->level)) {
		    if (state->tls_stats)
			smtp_tls_stat_decide_sec_level(state->tls_stats,
						       state->tls->level,
						       POL_STAT_VIOLATION);
		}
		/* Then, REQUIRETLS failure must take precedence over other. */
		if (TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level)) {
		    return (smtp_misc_fail(state, SMTP_MISC_FAIL_DONT_CACHE
					   | SMTP_MISC_FAIL_SOFT_NON_FINAL,
					   DSN_BY_LOCAL_MTA,
					   SMTP_RESP_FAKE(&fake, "5.7.10"),
					   "Sender requested REQUIRETLS, "
					   "but host %s refused to "
					   "start TLS: %s", session->namaddr,
					   translit(resp->str, "\n", " ")));
		}
		/* TLS_REQUIRED_BY_SECURITY_LEVEL */
		return (smtp_site_fail(state, STR(iter->host), resp,
		    "TLS is required, but host %s refused to start TLS: %s",
				       session->namaddr,
				       translit(resp->str, "\n", " ")));
	    }
	    /* Else try to continue in plain-text mode. */
	}

	/*
	 * Give up if we must use TLS but can't for various reasons.
	 *
	 * 200412 Be sure to provide the default clause at the bottom of this
	 * block. When TLS is required we must never, ever, end up in
	 * plain-text mode.
	 *
	 * When the sender requested REQUIRETLS, and the REQUIRETLS policy
	 * requires TLS, return the message as undeliverable only when there
	 * are no more alternative MX hosts.
	 */
	if (TLS_REQUIRED_BY_SECURITY_LEVEL(state->tls->level)
	    || TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level)) {
	    if (!(session->features & SMTP_FEATURE_STARTTLS)) {
#ifdef USE_TLSRPT
		if (state->tlsrpt)
		    trw_report_failure(state->tlsrpt,
				       TLSRPT_STARTTLS_NOT_SUPPORTED,
				        /* additional_info= */ (char *) 0,
				        /* failure_reason= */ (char *) 0);
#endif
		/* Before returning, decide all relevant policy status info. */
		if (TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level)) {
		    if (state->tls_stats)
			smtp_tls_stat_decide_reqtls(state->tls_stats,
						 SMTP_TLS_STAT_NAME_NOSTTLS,
						    POL_STAT_VIOLATION);
		}
		if (TLS_REQUIRED_BY_SECURITY_LEVEL(state->tls->level))
		    if (state->tls_stats)
			smtp_tls_stat_decide_sec_level(state->tls_stats,
						       state->tls->level,
						       POL_STAT_VIOLATION);
		/* Then, REQUIRETLS failure must take precedence over other. */
		if (TLS_REQUIRED_BY_REQTLS_POLICY(state->reqtls_level))
		    return (smtp_misc_fail(state, SMTP_MISC_FAIL_DONT_CACHE
					   | SMTP_MISC_FAIL_SOFT_NON_FINAL,
					   DSN_BY_LOCAL_MTA,
					   SMTP_RESP_FAKE(&fake, "5.7.30"),
					   "Sender requested REQUIRETLS, "
					   "but TLS service was not "
					   "offered by host %s",
					   session->namaddr));
		/* TLS_REQUIRED_BY_SECURITY_LEVEL */
		return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				       SMTP_RESP_FAKE(&fake, "4.7.4"),
			  "TLS is required, but was not offered by host %s",
				       session->namaddr));
	    } else if (smtp_tls_ctx == 0) {
		return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				       SMTP_RESP_FAKE(&fake, "4.7.5"),
		     "TLS is required, but our TLS engine is unavailable"));
	    } else {
		msg_warn("%s: TLS is required but unavailable, don't know why",
			 myname);
		return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				       SMTP_RESP_FAKE(&fake, "4.7.0"),
				       "TLS is required, but unavailable"));
	    }
	}
	/* Continue in plain-text mode. */
	if (state->tls_stats) {
	    smtp_tls_stat_decide_sec_level(state->tls_stats, TLS_LEV_NONE,
					   POL_STAT_COMPLIANT);
	    if (state->reqtls_level > SMTP_REQTLS_POLICY_ACT_DISABLE)
		smtp_tls_stat_decide_reqtls(state->tls_stats,
					    SMTP_TLS_STAT_NAME_NONE,
					    POL_STAT_COMPLIANT);
	}
    }
#endif
#ifdef USE_SASL_AUTH
    if (var_smtp_sasl_enable && (session->features & SMTP_FEATURE_AUTH))
	return (smtp_sasl_helo_login(state));
#endif

    return (0);
}

#ifdef USE_TLS

/* smtp_start_tls - turn on TLS and recurse into the HELO dialog */

static int smtp_start_tls(SMTP_STATE *state)
{
    SMTP_SESSION *session = state->session;
    SMTP_ITERATOR *iter = state->iterator;
    TLS_CLIENT_START_PROPS start_props;
    VSTRING *serverid;
    SMTP_RESP fake;
    TLS_CLIENT_INIT_PROPS init_props;
    VSTREAM *tlsproxy;
    VSTRING *port_buf;

    /*
     * When the TLS handshake succeeds, we can reuse a connection only if TLS
     * remains turned on for the lifetime of that connection. This requires
     * that the TLS library state is maintained in some proxy process, for
     * example, in tlsproxy(8). We then store the proxy file handle in the
     * connection cache, and reuse that file handle.
     *
     * Otherwise, we must turn off connection caching. We can't turn off TLS in
     * one SMTP client process, save the open connection to a cache which is
     * shared with all SMTP clients, migrate the connection to another SMTP
     * client, and resume TLS there. When the TLS handshake fails, we can't
     * reuse the SMTP connection either, because the conversation is in an
     * unknown state.
     */
    if (state->tls->conn_reuse == 0)
	DONT_CACHE_THIS_SESSION;

    /*
     * The following assumes sites that use TLS in a perverse configuration:
     * multiple hosts per hostname, or even multiple hosts per IP address.
     * All this without a shared TLS session cache, and they still want to
     * use TLS session caching???
     *
     * The TLS session cache records the trust chain verification status of
     * cached sessions. Different transports may have different CAfile or
     * CApath settings, perhaps to allow authenticated connections to sites
     * with private CA certs without trusting said private certs for other
     * sites. So we cannot assume that a trust chain valid for one transport
     * is valid for another. Therefore the client session id must include
     * either the transport name or the values of CAfile and CApath. We use
     * the transport name.
     *
     * XXX: We store only one session per lookup key. Ideally the key maps
     * 1-to-1 to a server TLS session cache. We use the IP address, port and
     * ehlo response name to build a lookup key that works for split caches
     * (that announce distinct names) behind a load balancer.
     *
     * XXX: The TLS library will salt the serverid with further details of the
     * protocol and cipher requirements including the server ehlo response.
     * Deferring the helo to the digested suffix results in more predictable
     * SSL session lookup key lengths. Add the current TLS security level to
     * account for TLS level overrides based on message content or envelope
     * metadata.
     */
    serverid = vstring_alloc(10);
    smtp_key_prefix(serverid, "&", state->iterator, SMTP_KEY_FLAG_SERVICE
		    | SMTP_KEY_FLAG_CUR_NEXTHOP	/* With port */
		    | SMTP_KEY_FLAG_HOSTNAME
		    | SMTP_KEY_FLAG_ADDR
		    | SMTP_KEY_FLAG_TLS_LEVEL);

    if (state->tls->conn_reuse) {
	TLS_CLIENT_PARAMS tls_params;

	/*
	 * Send all our wishes in one big request.
	 */
	TLS_PROXY_CLIENT_INIT_PROPS(&init_props,
				    log_param = VAR_LMTP_SMTP(TLS_LOGLEVEL),
				    log_level = var_smtp_tls_loglevel,
				    verifydepth = var_smtp_tls_scert_vd,
				    cache_type
				    = LMTP_SMTP_SUFFIX(TLS_MGR_SCACHE),
				    chain_files = var_smtp_tls_chain_files,
				    cert_file = var_smtp_tls_cert_file,
				    key_file = var_smtp_tls_key_file,
				    dcert_file = var_smtp_tls_dcert_file,
				    dkey_file = var_smtp_tls_dkey_file,
				    eccert_file = var_smtp_tls_eccert_file,
				    eckey_file = var_smtp_tls_eckey_file,
				    CAfile = var_smtp_tls_CAfile,
				    CApath = var_smtp_tls_CApath,
				    mdalg = var_smtp_tls_fpt_dgst);
	TLS_PROXY_CLIENT_START_PROPS(&start_props,
				     timeout = var_smtp_starttls_tmout,
				     tls_level = state->tls->level,
				     enable_rpk = state->tls->enable_rpk,
				     nexthop = session->tls_nexthop,
				     host = STR(iter->host),
				     namaddr = session->namaddrport,
				     sni = state->tls->sni,
				     serverid = vstring_str(serverid),
				     helo = session->helo,
				     protocols = state->tls->protocols,
				     cipher_grade = state->tls->grade,
				     cipher_exclusions
				     = vstring_str(state->tls->exclusions),
				     matchargv = state->tls->matchargv,
				     mdalg = var_smtp_tls_fpt_dgst,
#ifdef USE_TLSRPT
				     tlsrpt = state->tlsrpt,
#else
				     tlsrpt = 0,
#endif
				     ffail_type = 0,
				     dane = state->tls->dane);

	/*
	 * The tlsproxy(8) server enforces timeouts that are larger than
	 * those specified by the tlsproxy(8) client. These timeouts are a
	 * safety net for the case that the tlsproxy(8) client fails to
	 * enforce time limits. Normally, the tlsproxy(8) client would time
	 * out and trigger a plaintext event in the tlsproxy(8) server, and
	 * cause it to tear down the session.
	 *
	 * However, the tlsproxy(8) server has no insight into the SMTP
	 * protocol, and therefore it cannot by itself support different
	 * timeouts at different SMTP protocol stages. Instead, we specify
	 * the largest timeout (end-of-data) and rely on the SMTP client to
	 * time out first, which normally results in a plaintext event in the
	 * tlsproxy(8) server. Unfortunately, we cannot permit plaintext
	 * events during the TLS handshake, so we specify a separate timeout
	 * for that stage (the end-of-data timeout would be unreasonably
	 * large anyway).
	 */
#define PROXY_OPEN_FLAGS \
        (TLS_PROXY_FLAG_ROLE_CLIENT | TLS_PROXY_FLAG_SEND_CONTEXT)

	port_buf = vstring_alloc(100);		/* minimize fragmentation */
	vstring_sprintf(port_buf, "%d", ntohs(iter->port));
	tlsproxy =
	    tls_proxy_open(var_tlsproxy_service, PROXY_OPEN_FLAGS,
			   session->stream, STR(iter->addr),
			   STR(port_buf), var_smtp_starttls_tmout,
			   var_smtp_data2_tmout, state->service,
			   tls_proxy_client_param_from_config(&tls_params),
			   &init_props, &start_props);
	vstring_free(port_buf);

	/*
	 * To insert tlsproxy(8) between this process and the remote SMTP
	 * server, we swap the file descriptors between the tlsproxy and
	 * session->stream VSTREAMS, so that we don't lose all the
	 * user-configurable session->stream attributes (such as longjump
	 * buffers or timeouts).
	 *
	 * TODO: the tlsproxy RPCs should return more error detail than a "NO"
	 * result. OTOH, the in-process TLS engine does not return such info
	 * either.
	 *
	 * If the tlsproxy request fails we do not fall back to the in-process
	 * TLS stack. Reason: the admin enabled connection reuse to respect
	 * receiver policy; silently violating such policy would not be
	 * useful.
	 *
	 * We also don't fall back to the in-process TLS stack under low-traffic
	 * conditions, to avoid frustrating attempts to debug a problem with
	 * using the tlsproxy(8) service.
	 */
	if (tlsproxy == 0) {
	    session->tls_context = 0;
	} else {
	    vstream_control(tlsproxy,
			    CA_VSTREAM_CTL_DOUBLE,
			    CA_VSTREAM_CTL_END);
	    vstream_control(session->stream,
			    CA_VSTREAM_CTL_SWAP_FD(tlsproxy),
			    CA_VSTREAM_CTL_END);
	    (void) vstream_fclose(tlsproxy);	/* direct-to-server stream! */

	    /*
	     * There must not be any pending data in the stream buffers
	     * before we read the TLS context attributes.
	     */
	    vstream_fpurge(session->stream, VSTREAM_PURGE_BOTH);

	    /*
	     * After plumbing the plaintext stream, receive the TLS context
	     * object. For this we use the same VSTREAM buffer that we also
	     * use to receive subsequent SMTP commands, therefore we must be
	     * prepared for the possibility that the remote SMTP server
	     * starts talking immediately. The tlsproxy implementation sends
	     * the TLS context before remote content. The attribute protocol
	     * is robust enough that an adversary cannot insert their own TLS
	     * context attributes.
	     */
	    session->tls_context = tls_proxy_context_receive(session->stream);
	    if (session->tls_context) {
		session->features |= SMTP_FEATURE_FROM_PROXY;
		tls_log_summary(TLS_ROLE_CLIENT, TLS_USAGE_NEW,
				session->tls_context);
	    }
	}
    } else {					/* state->tls->conn_reuse */

	/*
	 * As of Postfix 2.5, tls_client_start() tries hard to always
	 * complete the TLS handshake. It records the verification and match
	 * status in the resulting TLScontext. It is now up to the
	 * application to abort the TLS connection if it chooses.
	 *
	 * XXX When tls_client_start() fails then we don't know what state the
	 * SMTP connection is in, so we give up on this connection even if we
	 * are not required to use TLS.
	 *
	 * Large parameter lists are error-prone, so we emulate a language
	 * feature that C does not have natively: named parameter lists.
	 */
	session->tls_context =
	    TLS_CLIENT_START(&start_props,
			     ctx = smtp_tls_ctx,
			     stream = session->stream,
			     fd = -1,
			     timeout = var_smtp_starttls_tmout,
			     tls_level = state->tls->level,
			     enable_rpk = state->tls->enable_rpk,
			     nexthop = session->tls_nexthop,
			     host = STR(iter->host),
			     namaddr = session->namaddrport,
			     sni = state->tls->sni,
			     serverid = vstring_str(serverid),
			     helo = session->helo,
			     protocols = state->tls->protocols,
			     cipher_grade = state->tls->grade,
			     cipher_exclusions
			     = vstring_str(state->tls->exclusions),
			     matchargv = state->tls->matchargv,
			     mdalg = var_smtp_tls_fpt_dgst,
#ifdef USE_TLSRPT
			     tlsrpt = state->tlsrpt,
#else
			     tlsrpt = 0,
#endif
			     ffail_type = state->tls->ext_policy_failure,
			     dane = state->tls->dane);

	/*
	 * At this point there must not be any pending data in the stream
	 * buffers.
	 */
	vstream_fpurge(session->stream, VSTREAM_PURGE_BOTH);
    }						/* state->tls->conn_reuse */

    vstring_free(serverid);

    if (session->tls_context == 0) {

	/*
	 * We must avoid further I/O, the peer is in an undefined state.
	 */
	DONT_USE_FORBIDDEN_SESSION;

	/*
	 * If TLS is optional, try delivery to the same server over a
	 * plaintext connection. Otherwise we would defer mail forever with
	 * destinations that have no alternate MX host.
	 *
	 * Don't fall back to plaintext if we were willing to use SASL-over-TLS
	 * authentication. If the server doesn't announce SASL support over
	 * plaintext connections, then we don't want delivery to fail with
	 * "relay access denied".
	 *
	 * If TLS is opportunistic, don't throttle the destination, otherwise if
	 * the mail is volume is high enough we may have difficulty ever
	 * draining even the deferred mail, as new mail provides a constant
	 * stream of negative feedback.
	 */
	if (PLAINTEXT_FALLBACK_OK_AFTER_STARTTLS_FAILURE)
	    RETRY_AS_PLAINTEXT;
	/* Leave all TLS feature policy status info as 'undecided'. */
	return (smtp_misc_fail(state, state->tls->level == TLS_LEV_MAY ?
			       SMTP_MISC_FAIL_NONE : SMTP_MISC_FAIL_THROTTLE,
			       DSN_BY_LOCAL_MTA,
			       SMTP_RESP_FAKE(&fake, "4.7.5"),
			       "Cannot start TLS: handshake failure"));
    }

    /*
     * If we are verifying the server certificate and are not happy with the
     * result, abort the delivery here. We have a usable TLS session with the
     * server, so no need to disable I/O, ... we can even be polite and send
     * "QUIT".
     *
     * See src/tls/tls_level.c and src/tls/tls.h. Levels above "encrypt" require
     * matching.
     *
     * NOTE: We use "IS_MATCHED" to satisfy policy, but "IS_SECURED" to log
     * effective security.  Thus "half-dane" is never "Verified" only
     * "Trusted", but matching is enforced here.
     *
     * NOTE: When none of the TLSA records were usable, "dane" and "half-dane"
     * fall back to "encrypt", updating the tls_context level accordingly, so
     * we must check that here, and not state->tls->level.
     */
    if (TLS_MUST_MATCH(session->tls_context->level)) {
	if (!TLS_CERT_IS_MATCHED(session->tls_context)) {
	    int     trusted = TLS_CERT_IS_TRUSTED(session->tls_context);

#ifdef USE_TLSRPT

	    /*
	     * Don't create a TLSRPT 'failure' event here, if the TLS engine
	     * already reported a more specific reason.
	     */
	    if (state->tlsrpt && session->tls_context->rpt_reported == 0) {
		(void) trw_report_failure(state->tlsrpt, trusted ?
					  TLSRPT_CERTIFICATE_HOST_MISMATCH :
					  TLSRPT_CERTIFICATE_NOT_TRUSTED,
					   /* additional_info= */ (char *) 0,
					   /* failure_reason= */ (char *) 0);
	    }
#endif
	    /* Finalize TLS feature policy status info before giving up. */
	    if (state->tls_stats)
		smtp_tls_stat_decide_sec_level(state->tls_stats,
					       session->tls_context->level,
					       POL_STAT_VIOLATION);

	    /*
	     * When the sender requested REQUIRETLS, and REQUIRETLS is
	     * enforced, return the message as undeliverable only when there
	     * are no more alternative MX hosts.
	     */
	    if (state->reqtls_level == SMTP_REQTLS_POLICY_ACT_ENFORCE) {
		if (state->tls_stats)
		    smtp_tls_stat_decide_reqtls(state->tls_stats,
						SMTP_TLS_STAT_NAME_NOCMATCH,
						POL_STAT_VIOLATION);
		return (smtp_misc_fail(state, SMTP_MISC_FAIL_DONT_CACHE
				       | SMTP_MISC_FAIL_SOFT_NON_FINAL,
				       DSN_BY_LOCAL_MTA,
				       SMTP_RESP_FAKE(&fake, "5.7.10"),
				       "Sender requested REQUIRETLS, "
				       "but no %s server certificate "
				       "was found. The last attempted "
				       "server was %s", trusted ?
				       "matching" : "trusted",
				       session->namaddr));
	    } else if (state->reqtls_level > SMTP_REQTLS_POLICY_ACT_DISABLE) {
		if (state->tls_stats)
		    smtp_tls_stat_decide_reqtls(state->tls_stats,
						SMTP_TLS_STAT_NAME_NOCMATCH,
						POL_STAT_COMPLIANT);
	    }
	    return (smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				   SMTP_RESP_FAKE(&fake, "4.7.5"),
				   "Server certificate not verified"));
	}
    }

    /*
     * Create a TLSRPT 'success' event only if the TLS engine has not created
     * a TLSRPT event. For example, The TLS engine will create a TLSRPT
     * 'failure' event when the TLS handshake was be successful, but the
     * security level was downgraded from opportunistic "dane" to
     * unauthenticated "encrypt".
     */
#ifdef USE_TLSRPT
    if (state->tlsrpt && session->tls_context->rpt_reported == 0)
	(void) trw_report_success(state->tlsrpt);
#endif

    /*
     * Report relaxed enforcement if the initial TLS level was degraded.
     */
    if (state->tls_stats)
	smtp_tls_stat_decide_sec_level(state->tls_stats,
				       session->tls_context->level,
				       POL_STAT_COMPLIANT);

    /*
     * At this point we have to re-negotiate the "EHLO" to reget the
     * feature-list.
     */
    return (smtp_helo(state));
}

#endif

/* smtp_hbc_logger - logging call-back for header/body checks */

static void smtp_hbc_logger(void *context, const char *action,
			            const char *where, const char *content,
			            const char *text)
{
    const SMTP_STATE *state = (SMTP_STATE *) context;

    if (*text) {
	msg_info("%s: %s: %s %.200s: %s",
		 state->request->queue_id, action, where, content, text);
    } else {
	msg_info("%s: %s: %s %.200s",
		 state->request->queue_id, action, where, content);
    }
}

/* smtp_text_out - output one header/body record */

static void smtp_text_out(void *context, int rec_type,
			          const char *text, ssize_t len,
			          off_t unused_offset)
{
    SMTP_STATE *state = (SMTP_STATE *) context;
    SMTP_SESSION *session = state->session;
    ssize_t data_left;
    const char *data_start;

    /*
     * Deal with an impedance mismatch between Postfix queue files (record
     * length <= $message_line_length_limit) and SMTP (DATA record length <=
     * $smtp_line_length_limit). The code below does a little too much work
     * when the SMTP line length limit is disabled, but it avoids code
     * duplication, and thus, it avoids testing and maintenance problems.
     */
    data_left = len;
    data_start = text;
    do {
	if (state->space_left == var_smtp_line_limit
	    && data_left > 0 && *data_start == '.')
	    smtp_fputc('.', session->stream);
	if (ENFORCING_SIZE_LIMIT(var_smtp_line_limit)
	    && data_left >= state->space_left) {
	    smtp_fputs(data_start, state->space_left, session->stream);
	    data_start += state->space_left;
	    data_left -= state->space_left;
	    state->space_left = var_smtp_line_limit;
	    if (data_left > 0 || rec_type == REC_TYPE_CONT) {
		smtp_fputc(' ', session->stream);
		state->space_left -= 1;

		/*
		 * XXX This can insert a line break into the middle of a
		 * multi-byte character (not necessarily UTF-8). Note that
		 * multibyte characters can span queue file records, for
		 * example if line_length_limit == smtp_line_length_limit.
		 */
		if (state->logged_line_length_limit == 0) {
		    msg_info("%s: breaking line > %d bytes with <CR><LF>SPACE",
			     state->request->queue_id, var_smtp_line_limit);
		    state->logged_line_length_limit = 1;
		}
	    }
	} else {
	    if (rec_type == REC_TYPE_CONT) {
		smtp_fwrite(data_start, data_left, session->stream);
		state->space_left -= data_left;
	    } else {
		smtp_fputs(data_start, data_left, session->stream);
		state->space_left = var_smtp_line_limit;
	    }
	    break;
	}
    } while (data_left > 0);
}

/* smtp_format_out - output one header/body record */

static void PRINTFLIKE(3, 4) smtp_format_out(void *, int, const char *,...);

static void smtp_format_out(void *context, int rec_type, const char *fmt,...)
{
    static VSTRING *vp;
    va_list ap;

    if (vp == 0)
	vp = vstring_alloc(100);
    va_start(ap, fmt);
    vstring_vsprintf(vp, fmt, ap);
    va_end(ap);
    smtp_text_out(context, rec_type, vstring_str(vp), VSTRING_LEN(vp), 0);
}

/* smtp_header_out - output one message header */

static void smtp_header_out(void *context, int unused_header_class,
			            const HEADER_OPTS *unused_info,
			            VSTRING *buf, off_t offset)
{
    char   *start = vstring_str(buf);
    char   *line;
    char   *next_line;

    /*
     * This code destroys the header. We could try to avoid clobbering it,
     * but we're not going to use the data any further.
     */
    for (line = start; line; line = next_line) {
	next_line = split_at(line, '\n');
	smtp_text_out(context, REC_TYPE_NORM, line, next_line ?
		      next_line - line - 1 : strlen(line), offset);
    }
}

/* smtp_header_rewrite - rewrite message header before output */

static void smtp_header_rewrite(void *context, int header_class,
				        const HEADER_OPTS *header_info,
				        VSTRING *buf, off_t offset)
{
    SMTP_STATE *state = (SMTP_STATE *) context;
    int     did_rewrite = 0;
    char   *line;
    char   *start;
    char   *next_line;
    char   *end_line;
    char   *result;

    /*
     * Apply optional header filtering.
     */
    if (smtp_header_checks) {
	result = hbc_header_checks(context, smtp_header_checks, header_class,
				   header_info, buf, offset);
	if (result == 0)
	    return;
	if (result == HBC_CHECKS_STAT_ERROR) {
	    msg_warn("%s: smtp header checks lookup error",
		     state->request->queue_id);
	    vstream_longjmp(state->session->stream, SMTP_ERR_DATA);
	}
	if (result != STR(buf)) {
	    vstring_strcpy(buf, result);
	    myfree(result);
	}
    }

    /*
     * Rewrite primary header addresses that match the smtp_generic_maps. The
     * cleanup server already enforces that all headers have proper lengths
     * and that all addresses are in proper form, so we don't have to repeat
     * that.
     */
    if (smtp_generic_maps && header_info && header_class == MIME_HDR_PRIMARY
	&& (header_info->flags & (HDR_OPT_SENDER | HDR_OPT_RECIP)) != 0) {
	TOK822 *tree;
	TOK822 **addr_list;
	TOK822 **tpp;

	tree = tok822_parse(vstring_str(buf)
			    + strlen(header_info->name) + 1);
	addr_list = tok822_grep(tree, TOK822_ADDR);
	for (tpp = addr_list; *tpp; tpp++)
	    did_rewrite |= smtp_map11_tree(tpp[0], smtp_generic_maps,
				     smtp_ext_prop_mask & EXT_PROP_GENERIC);
	if (did_rewrite) {
	    vstring_truncate(buf, strlen(header_info->name));
	    vstring_strcat(buf, ": ");
	    tok822_externalize(buf, tree, TOK822_STR_HEAD);
	}
	myfree((void *) addr_list);
	tok822_free_tree(tree);
    }

    /*
     * Pass through unmodified headers without reconstruction.
     */
    if (did_rewrite == 0) {
	smtp_header_out(context, header_class, header_info, buf, offset);
	return;
    }

    /*
     * A rewritten address list contains one address per line. The code below
     * replaces newlines by spaces, to fit as many addresses on a line as
     * possible (without rearranging the order of addresses). Prepending
     * white space to the beginning of lines is delegated to the output
     * routine.
     *
     * Code derived from cleanup_fold_header().
     */
    for (line = start = vstring_str(buf); line != 0; line = next_line) {
	end_line = line + strcspn(line, "\n");
	if (line > start) {
	    if (end_line - start < 70) {	/* TAB counts as one */
		line[-1] = ' ';
	    } else {
		start = line;
	    }
	}
	next_line = *end_line ? end_line + 1 : 0;
    }

    /*
     * Prepend a tab to continued header lines that went through the address
     * rewriting machinery. Just like smtp_header_out(), this code destroys
     * the header. We could try to avoid clobbering it, but we're not going
     * to use the data any further.
     *
     * Code derived from cleanup_out_header().
     */
    for (line = start = vstring_str(buf); line != 0; line = next_line) {
	next_line = split_at(line, '\n');
	if (line == start || IS_SPACE_TAB(*line)) {
	    smtp_text_out(state, REC_TYPE_NORM, line, next_line ?
			  next_line - line - 1 : strlen(line), offset);
	} else {
	    smtp_format_out(state, REC_TYPE_NORM, "\t%s", line);
	}
    }
}

/* smtp_body_rewrite - rewrite message body before output */

static void smtp_body_rewrite(void *context, int type,
			              const char *buf, ssize_t len,
			              off_t offset)
{
    SMTP_STATE *state = (SMTP_STATE *) context;
    char   *result;

    /*
     * Apply optional body filtering.
     */
    if (smtp_body_checks) {
	result = hbc_body_checks(context, smtp_body_checks, buf, len, offset);
	if (result == buf) {
	    smtp_text_out(state, type, buf, len, offset);
	} else if (result == HBC_CHECKS_STAT_ERROR) {
	    msg_warn("%s: smtp body checks lookup error",
		     state->request->queue_id);
	    vstream_longjmp(state->session->stream, SMTP_ERR_DATA);
	} else if (result != 0) {
	    smtp_text_out(state, type, result, strlen(result), offset);
	    myfree(result);
	}
    }
}

/* smtp_mime_fail - MIME problem */

static void smtp_mime_fail(SMTP_STATE *state, int mime_errs)
{
    const MIME_STATE_DETAIL *detail;
    SMTP_RESP fake;

    detail = mime_state_detail(mime_errs);
    smtp_mesg_fail(state, DSN_BY_LOCAL_MTA,
		   SMTP_RESP_FAKE(&fake, detail->dsn),
		   "%s", detail->text);
}

/* smtp_out_raw_or_mime - output buffer, raw output or MIME-aware */

static int smtp_out_raw_or_mime(SMTP_STATE *state, int rec_type, VSTRING *buf)
{
    SMTP_SESSION *session = state->session;
    int     mime_errs;

    if (session->mime_state == 0) {
	smtp_text_out((void *) state, rec_type, vstring_str(buf),
		      VSTRING_LEN(buf), (off_t) 0);
    } else {
	mime_errs =
	    mime_state_update(session->mime_state, rec_type,
			      vstring_str(buf), VSTRING_LEN(buf));
	if (mime_errs) {
	    smtp_mime_fail(state, mime_errs);
	    return (-1);
	}
    }
    return (0);
}

/* smtp_out_add_header - format address header, uses session->scratch* */

static int smtp_out_add_header(SMTP_STATE *state, const char *label,
			               const char *lt, const char *addr,
			               const char *gt)
{
    SMTP_SESSION *session = state->session;

    smtp_rewrite_generic_internal(session->scratch2, addr);
    vstring_sprintf(session->scratch, "%s: %s", label, lt);
    smtp_quote_822_address_flags(session->scratch,
				 vstring_str(session->scratch2),
				 QUOTE_FLAG_DEFAULT | QUOTE_FLAG_APPEND);
    vstring_strcat(session->scratch, gt);
    return (smtp_out_raw_or_mime(state, REC_TYPE_NORM, session->scratch));
}

/* smtp_out_add_headers - output additional headers, uses session->scratch* */

static int smtp_out_add_headers(SMTP_STATE *state)
{
    /* Prepend headers in the same order as mail_copy.c. */
    if (smtp_cli_attr.flags & SMTP_CLI_FLAG_RETURN_PATH)
	if (smtp_out_add_header(state, "Return-Path", "<",
				state->request->sender, ">") < 0)
	    return (-1);
    if (smtp_cli_attr.flags & SMTP_CLI_FLAG_ORIG_RCPT)
	if (smtp_out_add_header(state, "X-Original-To", "",
			 state->request->rcpt_list.info->orig_addr, "") < 0)
	    return (-1);
    if (smtp_cli_attr.flags & SMTP_CLI_FLAG_DELIVERED_TO)
	if (smtp_out_add_header(state, "Delivered-To", "",
			   state->request->rcpt_list.info->address, "") < 0)
	    return (-1);
    return (0);
}

/* smtp_loop - exercise the SMTP protocol engine */

static int smtp_loop(SMTP_STATE *state, NOCLOBBER int send_state,
		             NOCLOBBER int recv_state)
{
    const char *myname = "smtp_loop";
    DELIVER_REQUEST *request = state->request;
    SMTP_SESSION *session = state->session;
    SMTP_ITERATOR *iter = state->iterator;
    SMTP_RESP *resp;
    RECIPIENT *rcpt;
    VSTRING *next_command = vstring_alloc(100);
    int    *NOCLOBBER survivors = 0;
    NOCLOBBER int next_state;
    NOCLOBBER int next_rcpt;
    NOCLOBBER int send_rcpt;
    NOCLOBBER int recv_rcpt;
    NOCLOBBER int nrcpt;
    NOCLOBBER int recv_done;
    int     except;
    int     rec_type;
    NOCLOBBER int prev_type = 0;
    NOCLOBBER int mail_from_rejected;
    NOCLOBBER int downgrading;
    int     mime_errs;
    SMTP_RESP fake;
    int     fail_status;

    /* Caution: changes to RETURN() also affect code outside the main loop. */

#define RETURN(x) do { \
	if (recv_state != SMTP_STATE_LAST) \
	    DONT_CACHE_THIS_SESSION; \
	vstring_free(next_command); \
	if (survivors) \
	    myfree((void *) survivors); \
	if (session->mime_state) \
	    session->mime_state = mime_state_free(session->mime_state); \
	return (x); \
    } while (0)

#define SENDER_IS_AHEAD \
	(recv_state < send_state || recv_rcpt != send_rcpt)

#define SENDER_IN_WAIT_STATE \
	(send_state == SMTP_STATE_DOT || send_state == SMTP_STATE_LAST)

#define SENDING_MAIL \
	(recv_state <= SMTP_STATE_DOT)

#define CANT_RSET_THIS_SESSION \
	(session->features |= SMTP_FEATURE_RSET_REJECTED)

    /*
     * Pipelining support requires two loops: one loop for sending and one
     * for receiving. Each loop has its own independent state. Most of the
     * time the sender can run ahead of the receiver by as much as the TCP
     * send buffer permits. There are only two places where the sender must
     * wait for status information from the receiver: once after sending DATA
     * and once after sending QUIT.
     *
     * The sender state advances until the TCP send buffer would overflow, or
     * until the sender needs status information from the receiver. At that
     * point the receiver starts processing responses. Once the receiver has
     * caught up with the sender, the sender resumes sending commands. If the
     * receiver detects a serious problem (MAIL FROM rejected, all RCPT TO
     * commands rejected, DATA rejected) it forces the sender to abort the
     * SMTP dialog with RSET and QUIT.
     */
    nrcpt = 0;
    next_rcpt = send_rcpt = recv_rcpt = recv_done = 0;
    mail_from_rejected = 0;

    /*
     * Prepare for disaster. This should not be needed because the design
     * guarantees that no output is flushed before smtp_chat_resp() is
     * called.
     *
     * 1) Every SMTP command fits entirely in a VSTREAM output buffer.
     *
     * 2) smtp_loop() never invokes smtp_chat_cmd() without making sure that
     * there is sufficient space for the command in the output buffer.
     *
     * 3) smtp_loop() flushes the output buffer to avoid server timeouts.
     *
     * Changing any of these would violate the design, and would likely break
     * SMTP pipelining.
     *
     * We set up the error handler anyway (only upon entry to avoid wasting
     * resources) because 1) there is code below that expects that VSTREAM
     * timeouts are enabled, and 2) this allows us to detect if someone broke
     * Postfix by introducing spurious flush before read operations.
     */
    if (send_state < SMTP_STATE_XFORWARD_NAME_ADDR
	|| send_state > SMTP_STATE_QUIT)
	msg_panic("%s: bad sender state %d (receiver state %d)",
		  myname, send_state, recv_state);
    smtp_stream_setup(session->stream, *xfer_timeouts[send_state],
		      var_smtp_req_deadline, 0);
    if ((except = vstream_setjmp(session->stream)) != 0) {
	msg_warn("smtp_proto: spurious flush before read in send state %d",
		 send_state);
	RETURN(SENDING_MAIL ? smtp_stream_except(state, except,
					     xfer_states[send_state]) : -1);
    }

    /*
     * The main protocol loop.
     */
    do {

	/*
	 * Build the next command.
	 */
	switch (send_state) {

	    /*
	     * Sanity check.
	     */
	default:
	    msg_panic("%s: bad sender state %d", myname, send_state);

	    /*
	     * Build the XFORWARD command. With properly sanitized
	     * information, the command length stays within the 512 byte
	     * command line length limit.
	     *
	     * XXX smtpd_xforward_preset() initializes some fields as "unknown"
	     * and some as null; historically, pickup(8) does not send any of
	     * these, and the queue manager presets absent fields to "not
	     * available" except for the rewrite context which is preset to
	     * local by way of migration aid. These definitions need to be
	     * centralized for maintainability.
	     */
#ifndef CAN_FORWARD_CLIENT_NAME
#define _ATTR_AVAIL_AND_KNOWN_(val) \
	(DEL_REQ_ATTR_AVAIL(val) && strcasecmp((val), "unknown"))
#define CAN_FORWARD_CLIENT_NAME	_ATTR_AVAIL_AND_KNOWN_
#define CAN_FORWARD_CLIENT_ADDR	_ATTR_AVAIL_AND_KNOWN_
#define CAN_FORWARD_CLIENT_PORT	_ATTR_AVAIL_AND_KNOWN_
#define CAN_FORWARD_PROTO_NAME	_ATTR_AVAIL_AND_KNOWN_
#define CAN_FORWARD_HELO_NAME	DEL_REQ_ATTR_AVAIL
#define CAN_FORWARD_IDENT_NAME	DEL_REQ_ATTR_AVAIL
#define CAN_FORWARD_RWR_CONTEXT	DEL_REQ_ATTR_AVAIL
#endif

	case SMTP_STATE_XFORWARD_NAME_ADDR:
	    vstring_strcpy(next_command, XFORWARD_CMD);
	    if ((session->features & SMTP_FEATURE_XFORWARD_NAME)
		&& CAN_FORWARD_CLIENT_NAME(request->client_name)) {
		vstring_strcat(next_command, " " XFORWARD_NAME "=");
		xtext_quote_append(next_command, request->client_name, "");
	    }
	    if ((session->features & SMTP_FEATURE_XFORWARD_ADDR)
		&& CAN_FORWARD_CLIENT_ADDR(request->client_addr)) {
		vstring_strcat(next_command, " " XFORWARD_ADDR "=");
		xtext_quote_append(next_command, request->client_addr, "");
	    }
	    if ((session->features & SMTP_FEATURE_XFORWARD_PORT)
		&& CAN_FORWARD_CLIENT_PORT(request->client_port)) {
		vstring_strcat(next_command, " " XFORWARD_PORT "=");
		xtext_quote_append(next_command, request->client_port, "");
	    }
	    if (session->send_proto_helo)
		next_state = SMTP_STATE_XFORWARD_PROTO_HELO;
	    else
		next_state = SMTP_STATE_MAIL;
	    break;

	case SMTP_STATE_XFORWARD_PROTO_HELO:
	    vstring_strcpy(next_command, XFORWARD_CMD);
	    if ((session->features & SMTP_FEATURE_XFORWARD_PROTO)
		&& CAN_FORWARD_PROTO_NAME(request->client_proto)) {
		vstring_strcat(next_command, " " XFORWARD_PROTO "=");
		xtext_quote_append(next_command, request->client_proto, "");
	    }
	    if ((session->features & SMTP_FEATURE_XFORWARD_HELO)
		&& CAN_FORWARD_HELO_NAME(request->client_helo)) {
		vstring_strcat(next_command, " " XFORWARD_HELO "=");
		xtext_quote_append(next_command, request->client_helo, "");
	    }
	    if ((session->features & SMTP_FEATURE_XFORWARD_IDENT)
		&& CAN_FORWARD_IDENT_NAME(request->log_ident)) {
		vstring_strcat(next_command, " " XFORWARD_IDENT "=");
		xtext_quote_append(next_command, request->log_ident, "");
	    }
	    if ((session->features & SMTP_FEATURE_XFORWARD_DOMAIN)
		&& CAN_FORWARD_RWR_CONTEXT(request->rewrite_context)) {
		vstring_strcat(next_command, " " XFORWARD_DOMAIN "=");
		xtext_quote_append(next_command,
		     strcmp(request->rewrite_context, MAIL_ATTR_RWR_LOCAL) ?
			      XFORWARD_DOM_REMOTE : XFORWARD_DOM_LOCAL, "");
	    }
	    next_state = SMTP_STATE_MAIL;
	    break;

	    /*
	     * Build the MAIL FROM command.
	     */
	case SMTP_STATE_MAIL:
	    request->msg_stats.reuse_count = session->reuse_count;
	    GETTIMEOFDAY(&request->msg_stats.conn_setup_done);
	    smtp_rewrite_generic_internal(session->scratch2, request->sender);
	    smtp_quote_821_address(session->scratch,
				   vstring_str(session->scratch2));
	    vstring_sprintf(next_command, "MAIL FROM:<%s>",
			    vstring_str(session->scratch));
	    /* XXX Don't announce SIZE if we're going to MIME downgrade. */
	    if (session->features & SMTP_FEATURE_SIZE	/* RFC 1870 */
		&& !SMTP_MIME_DOWNGRADE(session, request))
		vstring_sprintf_append(next_command, " SIZE=%lu",
				       request->data_size);
	    if (session->features & SMTP_FEATURE_8BITMIME) {	/* RFC 1652 */
		if (strcmp(request->encoding, MAIL_ATTR_ENC_8BIT) == 0)
		    vstring_strcat(next_command, " BODY=8BITMIME");
		else if (strcmp(request->encoding, MAIL_ATTR_ENC_7BIT) == 0)
		    vstring_strcat(next_command, " BODY=7BIT");
		else if (strcmp(request->encoding, MAIL_ATTR_ENC_NONE) != 0)
		    msg_warn("%s: unknown content encoding: %s",
			     request->queue_id, request->encoding);
	    }
	    if (session->features & SMTP_FEATURE_DSN) {
		if (request->dsn_envid[0]) {
		    vstring_sprintf_append(next_command, " ENVID=");
		    xtext_quote_append(next_command, request->dsn_envid, "+=");
		}
		/* Fix 20250825: limit content exposure in bounce. */
#ifdef USE_TLS
		if (state->reqtls_level > SMTP_REQTLS_POLICY_ACT_DISABLE
		    && (session->features & SMTP_FEATURE_REQTLS) == 0)
		    vstring_sprintf_append(next_command, " RET=%s",
					   dsn_ret_str(DSN_RET_HDRS));
		else
#endif
		if (request->dsn_ret)
		    vstring_sprintf_append(next_command, " RET=%s",
					   dsn_ret_str(request->dsn_ret));
	    }

	    /*
	     * Request SMTPUTF8 when the remote SMTP server supports SMTPUTF8
	     * and the sender requested SMTPUTF8 support.
	     *
	     * If the sender requested SMTPUTF8 but the remote SMTP server does
	     * not support SMTPUTF8, then we have already determined earlier
	     * that delivering this message without SMTPUTF8 will not break
	     * the SMTPUTF8 promise that was made to the sender.
	     */
	    if ((session->features & SMTP_FEATURE_SMTPUTF8) != 0
		&& (request->sendopts & SMTPUTF8_FLAG_REQUESTED) != 0)
		vstring_strcat(next_command, " SMTPUTF8");

	    /*
	     * Request REQUIRETLS when the remote SMTP server supports
	     * REQUIRETLS and the sender requested REQUIRETLS.
	     */
#ifdef USE_TLS
	    if (state->reqtls_level > SMTP_REQTLS_POLICY_ACT_DISABLE) {
		if ((session->features & SMTP_FEATURE_REQTLS) != 0) {
		    vstring_strcat(next_command, " REQUIRETLS");
		} else if (state->reqtls_level
			   == SMTP_REQTLS_POLICY_ACT_ENFORCE) {
		    msg_panic("Can't happen: must enforce REQUIRETLS, but "
			      "host %s did not announce REQUIRETLS support",
			      session->namaddr);
		}
	    }
#endif

	    /*
	     * We authenticate the local MTA only, but not the sender.
	     */
#ifdef USE_SASL_AUTH
	    if (var_smtp_sasl_enable
		&& var_smtp_dummy_mail_auth
		&& (session->features & SMTP_FEATURE_AUTH))
		vstring_strcat(next_command, " AUTH=<>");
#endif

	    /*
	     * CVE-2009-3555 (TLS renegotiation). Try to detect a mail
	     * hijacking attack that prepends malicious EHLO/MAIL/RCPT/DATA
	     * commands to our TLS session.
	     *
	     * For the attack to succeed, the remote SMTP server must reply to
	     * the malicious EHLO/MAIL/RCPT/DATA commands after completing
	     * TLS (re)negotiation, so that the replies arrive in our TLS
	     * session (otherwise the Postfix SMTP client would time out
	     * waiting for an answer). With some luck we can detect this
	     * specific attack as a server MAIL reply that arrives before we
	     * send our own MAIL command.
	     *
	     * We don't apply this test to the HELO command because the result
	     * would be very timing sensitive, and we don't apply this test
	     * to RCPT and DATA replies because these may be pipelined for
	     * legitimate reasons.
	     */
#ifdef USE_TLS
	    if (var_smtp_tls_blk_early_mail_reply
		&& (state->misc_flags & SMTP_MISC_FLAG_IN_STARTTLS) != 0
		&& (vstream_peek(session->stream) > 0
		    || peekfd(vstream_fileno(session->stream)) > 0))
		session->features |= SMTP_FEATURE_EARLY_TLS_MAIL_REPLY;
#endif

	    /*
	     * We now return to our regular broadcast.
	     */
	    next_state = SMTP_STATE_RCPT;
	    break;

	    /*
	     * Build one RCPT TO command before we have seen the MAIL FROM
	     * response.
	     */
	case SMTP_STATE_RCPT:
	    rcpt = request->rcpt_list.info + send_rcpt;
	    smtp_rewrite_generic_internal(session->scratch2, rcpt->address);
	    smtp_quote_821_address(session->scratch,
				   vstring_str(session->scratch2));
	    vstring_sprintf(next_command, "RCPT TO:<%s>",
			    vstring_str(session->scratch));
	    if (session->features & SMTP_FEATURE_DSN) {
		/* XXX DSN xtext encode address value not type. */
		const char *orcpt_type_addr = rcpt->dsn_orcpt;

		/* Fix 20140706: don't use empty rcpt->orig_addr. */
		if (orcpt_type_addr[0] == 0 && rcpt->orig_addr[0] != 0) {
		    quote_822_local(session->scratch, rcpt->orig_addr);
		    vstring_sprintf(session->scratch2, "%s;%s",
		    /* Fix 20140707: sender must request SMTPUTF8. */
				    ((request->sendopts & SMTPUTF8_FLAG_ALL)
				 && !allascii(vstring_str(session->scratch))
		     && valid_utf8_stringz(vstring_str(session->scratch))) ?
				    "utf-8" : "rfc822",
				    vstring_str(session->scratch));
		    orcpt_type_addr = vstring_str(session->scratch2);
		}
		if (orcpt_type_addr[0] != 0) {
		    /* Fix 20140706: don't send unquoted ORCPT. */
		    /* Fix 20140707: quoting method must match orcpt type. */
		    /* Fix 20140707: handle uxtext encoder errors. */
		    if (strncasecmp(orcpt_type_addr, "utf-8;", 6) == 0) {
			if (uxtext_quote(session->scratch,
					 orcpt_type_addr, "+=") != 0)
			    vstring_sprintf_append(next_command, " ORCPT=%s",
					     vstring_str(session->scratch));
		    } else {
			xtext_quote(session->scratch, orcpt_type_addr, "=");
			vstring_sprintf_append(next_command, " ORCPT=%s",
					     vstring_str(session->scratch));
		    }
		}
		if (rcpt->dsn_notify)
		    vstring_sprintf_append(next_command, " NOTIFY=%s",
					   dsn_notify_str(rcpt->dsn_notify));
	    }
	    if ((next_rcpt = send_rcpt + 1) == SMTP_RCPT_LEFT(state))
		next_state = (DEL_REQ_TRACE_ONLY(request->flags)
			      && smtp_vrfy_tgt == SMTP_STATE_RCPT) ?
		    SMTP_STATE_ABORT : SMTP_STATE_DATA;
	    break;

	    /*
	     * Build the DATA command before we have seen all the RCPT TO
	     * responses.
	     */
	case SMTP_STATE_DATA:
	    vstring_strcpy(next_command, "DATA");
	    next_state = SMTP_STATE_DOT;
	    break;

	    /*
	     * Build the "." command after we have seen the DATA response
	     * (DATA is a protocol synchronization point).
	     *
	     * Changing the connection caching state here is safe because it
	     * affects none of the not-yet processed replies to
	     * already-generated commands.
	     */
	case SMTP_STATE_DOT:
	    vstring_strcpy(next_command, ".");
	    if (THIS_SESSION_IS_EXPIRED)
		DONT_CACHE_THIS_SESSION;
	    next_state = THIS_SESSION_IS_CACHED ?
		SMTP_STATE_LAST : SMTP_STATE_QUIT;
	    break;

	    /*
	     * The SMTP_STATE_ABORT sender state is entered by the sender
	     * when it has verified all recipients; or it is entered by the
	     * receiver when all recipients are verified or rejected, and is
	     * then left before the bottom of the main loop.
	     *
	     * Changing the connection caching state here is safe because there
	     * are no not-yet processed replies to already-generated
	     * commands.
	     */
	case SMTP_STATE_ABORT:
	    vstring_strcpy(next_command, "RSET");
	    if (THIS_SESSION_IS_EXPIRED)
		DONT_CACHE_THIS_SESSION;
	    next_state = THIS_SESSION_IS_CACHED ?
		SMTP_STATE_LAST : SMTP_STATE_QUIT;
	    break;

	    /*
	     * Build the RSET command. This is entered as initial state from
	     * smtp_rset() and has its own dedicated state transitions. It is
	     * used to find out the status of a cached session before
	     * attempting mail delivery.
	     */
	case SMTP_STATE_RSET:
	    vstring_strcpy(next_command, "RSET");
	    next_state = SMTP_STATE_LAST;
	    break;

	    /*
	     * Build the QUIT command before we have seen the "." or RSET
	     * response. This is entered as initial state from smtp_quit(),
	     * or is reached near the end of any non-cached session.
	     *
	     * Changing the connection caching state here is safe. If this
	     * command is pipelined together with a preceding command, then
	     * connection caching was already turned off. Do not clobber the
	     * "bad connection" flag.
	     */
	case SMTP_STATE_QUIT:
	    vstring_strcpy(next_command, "QUIT");
	    next_state = SMTP_STATE_LAST;
	    if (THIS_SESSION_IS_CACHED)
		DONT_CACHE_THIS_SESSION;
	    break;

	    /*
	     * The final sender state has no action associated with it.
	     */
	case SMTP_STATE_LAST:
	    VSTRING_RESET(next_command);
	    break;
	}
	VSTRING_TERMINATE(next_command);

	/*
	 * Process responses until the receiver has caught up. Vstreams
	 * automatically flush buffered output when reading new data.
	 *
	 * Flush unsent output if command pipelining is off or if no I/O
	 * happened for a while. This limits the accumulation of client-side
	 * delays in pipelined sessions.
	 *
	 * The PIPELINING engine will flush the VSTREAM buffer if the sender
	 * could otherwise produce more output than fits the PIPELINING
	 * buffer. This generally works because we know exactly how much
	 * output we produced since the last time that the sender and
	 * receiver synchronized the SMTP state. However this logic is not
	 * applicable after the sender enters the DATA phase, where it does
	 * not synchronize with the receiver until the <CR><LF>.<CR><LF>.
	 * Thus, the PIPELINING engine no longer knows how much data is
	 * pending in the TCP send buffer. For this reason, if PIPELINING is
	 * enabled, we always pipeline QUIT after <CR><LF>.<CR><LF>. This is
	 * safe because once the receiver reads <CR><LF>.<CR><LF>, its TCP
	 * stack either has already received the QUIT<CR><LF>, or else it
	 * acknowledges all bytes up to and including <CR><LF>.<CR><LF>,
	 * making room in the sender's TCP stack for QUIT<CR><LF>.
	 */
#define CHECK_PIPELINING_BUFSIZE \
	(recv_state != SMTP_STATE_DOT || send_state != SMTP_STATE_QUIT)

	if (SENDER_IN_WAIT_STATE
	    || (SENDER_IS_AHEAD
		&& ((session->features & SMTP_FEATURE_PIPELINING) == 0
		    || (CHECK_PIPELINING_BUFSIZE
			&& (VSTRING_LEN(next_command) + 2
		    + vstream_bufstat(session->stream, VSTREAM_BST_OUT_PEND)
			    > PIPELINING_BUFSIZE))
		    || time((time_t *) 0)
		    - vstream_ftime(session->stream) > 10))) {
	    while (SENDER_IS_AHEAD) {

		/*
		 * Sanity check.
		 */
		if (recv_state < SMTP_STATE_XFORWARD_NAME_ADDR
		    || recv_state > SMTP_STATE_QUIT)
		    msg_panic("%s: bad receiver state %d (sender state %d)",
			      myname, recv_state, send_state);

		/*
		 * Receive the next server response. Use the proper timeout,
		 * and log the proper client state in case of trouble.
		 *
		 * XXX If we lose the connection before sending end-of-data,
		 * find out if the server sent a premature end-of-data reply.
		 * If this read attempt fails, report "lost connection while
		 * sending message body", not "lost connection while sending
		 * end-of-data".
		 *
		 * "except" becomes zero just above the protocol loop, and stays
		 * zero or triggers an early return from the loop. In just
		 * one case: loss of the connection when sending the message
		 * body, we record the exception, and keep processing in the
		 * hope of detecting a premature 5XX. We must be careful to
		 * not clobber this non-zero value once it is set. The
		 * variable need not survive longjmp() calls, since the only
		 * setjmp() which does not return early is the one sets this
		 * condition, subsequent failures always return early.
		 */
#define LOST_CONNECTION_INSIDE_DATA (except == SMTP_ERR_EOF)

		smtp_stream_setup(session->stream, *xfer_timeouts[recv_state],
				  var_smtp_req_deadline, 0);
		if (LOST_CONNECTION_INSIDE_DATA) {
		    if (vstream_setjmp(session->stream) != 0)
			RETURN(smtp_stream_except(state, SMTP_ERR_EOF,
						  "sending message body"));
		} else {
		    if ((except = vstream_setjmp(session->stream)) != 0)
			RETURN(SENDING_MAIL ? smtp_stream_except(state, except,
					     xfer_states[recv_state]) : -1);
		}
		resp = smtp_chat_resp(session);

		/*
		 * Process the response.
		 */
		switch (recv_state) {

		    /*
		     * Process the XFORWARD response.
		     */
		case SMTP_STATE_XFORWARD_NAME_ADDR:
		    if (resp->code / 100 != 2)
			msg_warn("host %s said: %s (in reply to %s)",
				 session->namaddrport,
				 translit(resp->str, "\n", " "),
			       xfer_request[SMTP_STATE_XFORWARD_NAME_ADDR]);
		    if (session->send_proto_helo)
			recv_state = SMTP_STATE_XFORWARD_PROTO_HELO;
		    else
			recv_state = SMTP_STATE_MAIL;
		    break;

		case SMTP_STATE_XFORWARD_PROTO_HELO:
		    if (resp->code / 100 != 2)
			msg_warn("host %s said: %s (in reply to %s)",
				 session->namaddrport,
				 translit(resp->str, "\n", " "),
			      xfer_request[SMTP_STATE_XFORWARD_PROTO_HELO]);
		    recv_state = SMTP_STATE_MAIL;
		    break;

		    /*
		     * Process the MAIL FROM response. When the server
		     * rejects the sender, set the mail_from_rejected flag so
		     * that the receiver may apply a course correction.
		     */
		case SMTP_STATE_MAIL:
		    if (resp->code / 100 != 2) {
			smtp_mesg_fail(state, STR(iter->host), resp,
				       "host %s said: %s (in reply to %s)",
				       session->namaddr,
				       translit(resp->str, "\n", " "),
				       xfer_request[SMTP_STATE_MAIL]);
			mail_from_rejected = 1;
		    }

		    /*
		     * CVE-2009-3555 (TLS renegotiation). Whatever it was
		     * that arrived before we sent our MAIL FROM command, it
		     * was not a fatal-level TLS alert message. It could be a
		     * warning-level TLS alert message, or a ChangeCipherSpec
		     * message, but such messages are not normally sent in
		     * the middle of a TLS session. We disconnect and try
		     * again later.
		     */
#ifdef USE_TLS
		    if (var_smtp_tls_blk_early_mail_reply
			&& (session->features & SMTP_FEATURE_EARLY_TLS_MAIL_REPLY)) {
			smtp_site_fail(state, DSN_BY_LOCAL_MTA,
				       SMTP_RESP_FAKE(&fake, "4.7.0"),
				       "unexpected server message");
			msg_warn("server %s violates %s policy",
				 session->namaddr,
				 VAR_LMTP_SMTP(TLS_BLK_EARLY_MAIL_REPLY));
			mail_from_rejected = 1;
		    }
#endif

		    /*
		     * We now return to our regular broadcast.
		     */
		    recv_state = SMTP_STATE_RCPT;
		    break;

		    /*
		     * Process one RCPT TO response. If MAIL FROM was
		     * rejected, ignore RCPT TO responses: all recipients are
		     * dead already. When all recipients are rejected the
		     * receiver may apply a course correction.
		     *
		     * XXX 2821: Section 4.5.3.1 says that a 552 RCPT TO reply
		     * must be treated as if the server replied with 452.
		     * However, this causes "too much mail data" to be
		     * treated as a recoverable error, which is wrong. I'll
		     * stick with RFC 821.
		     */
		case SMTP_STATE_RCPT:
		    if (!mail_from_rejected) {
#ifdef notdef
			if (resp->code == 552) {
			    resp->code = 452;
			    resp->dsn[0] = '4';
			}
#endif
			rcpt = request->rcpt_list.info + recv_rcpt;
			if (resp->code / 100 == 2) {
			    if (!smtp_mode) {
				if (survivors == 0)
				    survivors = (int *)
					mymalloc(request->rcpt_list.len
						 * sizeof(int));
				survivors[nrcpt] = recv_rcpt;
			    }
			    ++nrcpt;
			    /* If trace-only, mark the recipient done. */
			    if (DEL_REQ_TRACE_ONLY(request->flags)
				&& smtp_vrfy_tgt == SMTP_STATE_RCPT) {
				translit(resp->str, "\n", " ");
				smtp_rcpt_done(state, resp, rcpt);
			    }
			} else {
			    smtp_rcpt_fail(state, rcpt, STR(iter->host), resp,
					"host %s said: %s (in reply to %s)",
					   session->namaddr,
					   translit(resp->str, "\n", " "),
					   xfer_request[SMTP_STATE_RCPT]);
			}
		    }
		    /* If trace-only, send RSET instead of DATA. */
		    if (++recv_rcpt == SMTP_RCPT_LEFT(state))
			recv_state = (DEL_REQ_TRACE_ONLY(request->flags)
				      && smtp_vrfy_tgt == SMTP_STATE_RCPT) ?
			    SMTP_STATE_ABORT : SMTP_STATE_DATA;
		    /* XXX Also: record if non-delivering session. */
		    break;

		    /*
		     * Process the DATA response. When the server rejects
		     * DATA, set nrcpt to a negative value so that the
		     * receiver can apply a course correction.
		     */
		case SMTP_STATE_DATA:
		    recv_state = SMTP_STATE_DOT;
		    if (resp->code / 100 != 3) {
			if (nrcpt > 0)
			    smtp_mesg_fail(state, STR(iter->host), resp,
					"host %s said: %s (in reply to %s)",
					   session->namaddr,
					   translit(resp->str, "\n", " "),
					   xfer_request[SMTP_STATE_DATA]);
			nrcpt = -1;
		    }

		    /*
		     * In the case of a successful address probe with target
		     * equal to DATA, the remote server is now in the DATA
		     * state, and therefore we must not make any further
		     * attempt to send or receive on this connection. This
		     * means that we cannot not reuse the general-purpose
		     * course-correction logic below which sends RSET (and
		     * perhaps QUIT). Instead we "jump" straight to the exit
		     * and force an unceremonious disconnect.
		     */
		    else if (DEL_REQ_TRACE_ONLY(request->flags)
			     && smtp_vrfy_tgt == SMTP_STATE_DATA) {
			for (nrcpt = 0; nrcpt < recv_rcpt; nrcpt++) {
			    rcpt = request->rcpt_list.info + nrcpt;
			    if (!SMTP_RCPT_ISMARKED(rcpt)) {
				translit(resp->str, "\n", " ");
				SMTP_RESP_SET_DSN(resp, "2.0.0");
				smtp_rcpt_done(state, resp, rcpt);
			    }
			}
			DONT_CACHE_THIS_SESSION;
			send_state = recv_state = SMTP_STATE_LAST;
		    }
		    break;

		    /*
		     * Process the end of message response. Ignore the
		     * response when no recipient was accepted: all
		     * recipients are dead already, and the next receiver
		     * state is SMTP_STATE_LAST/QUIT regardless. Otherwise,
		     * if the message transfer fails, bounce all remaining
		     * recipients, else cross off the recipients that were
		     * delivered.
		     */
		case SMTP_STATE_DOT:
		    GETTIMEOFDAY(&request->msg_stats.deliver_done);
		    if (smtp_mode) {
			if (nrcpt > 0) {
			    if (resp->code / 100 != 2) {
				smtp_mesg_fail(state, STR(iter->host), resp,
					"host %s said: %s (in reply to %s)",
					       session->namaddr,
					     translit(resp->str, "\n", " "),
					       xfer_request[SMTP_STATE_DOT]);
			    } else {
				for (nrcpt = 0; nrcpt < recv_rcpt; nrcpt++) {
				    rcpt = request->rcpt_list.info + nrcpt;
				    if (!SMTP_RCPT_ISMARKED(rcpt)) {
					translit(resp->str, "\n", " ");
					smtp_rcpt_done(state, resp, rcpt);
				    }
				}
			    }
			}
		    }

		    /*
		     * With LMTP we have one response per accepted RCPT TO
		     * command. Stay in the SMTP_STATE_DOT state until we
		     * have collected all responses.
		     */
		    else {
			if (nrcpt > 0) {
			    rcpt = request->rcpt_list.info
				+ survivors[recv_done++];
			    if (resp->code / 100 != 2) {
				smtp_rcpt_fail(state, rcpt, STR(iter->host), resp,
					"host %s said: %s (in reply to %s)",
					       session->namaddr,
					     translit(resp->str, "\n", " "),
					       xfer_request[SMTP_STATE_DOT]);
			    } else {
				translit(resp->str, "\n", " ");
				smtp_rcpt_done(state, resp, rcpt);
			    }
			}
			if (msg_verbose)
			    msg_info("%s: got %d of %d end-of-data replies",
				     myname, recv_done, nrcpt);
			if (recv_done < nrcpt)
			    break;
		    }

		    /*
		     * XXX Do not change the connection caching state here,
		     * even if the connection caching timer expired between
		     * generating the command and processing the reply,
		     * otherwise the sender and receiver loops get out of
		     * sync. The caller will call smtp_quit() if appropriate.
		     */
		    if (var_skip_quit_resp || THIS_SESSION_IS_CACHED
			|| LOST_CONNECTION_INSIDE_DATA)
			recv_state = SMTP_STATE_LAST;
		    else
			recv_state = SMTP_STATE_QUIT;
		    break;

		    /*
		     * Receive the RSET response.
		     *
		     * The SMTP_STATE_ABORT sender state is entered by the
		     * sender when it has verified all recipients; or it is
		     * entered by the receiver when all recipients are
		     * verified or rejected, and is then left before the
		     * bottom of the main loop.
		     *
		     * XXX Do not change the connection caching state here, even
		     * if the server rejected RSET or if the connection
		     * caching timer expired between generating the command
		     * and processing the reply, otherwise the sender and
		     * receiver loops get out of sync. The caller will call
		     * smtp_quit() if appropriate.
		     */
		case SMTP_STATE_ABORT:
		    recv_state = (var_skip_quit_resp || THIS_SESSION_IS_CACHED ?
				  SMTP_STATE_LAST : SMTP_STATE_QUIT);
		    break;

		    /*
		     * This is the initial receiver state from smtp_rset().
		     * It is used to find out the status of a cached session
		     * before attempting mail delivery.
		     */
		case SMTP_STATE_RSET:
		    if (resp->code / 100 != 2)
			CANT_RSET_THIS_SESSION;
		    recv_state = SMTP_STATE_LAST;
		    break;

		    /*
		     * Receive, but otherwise ignore, the QUIT response.
		     */
		case SMTP_STATE_QUIT:
		    recv_state = SMTP_STATE_LAST;
		    break;
		}
	    }

	    /*
	     * At this point, the sender and receiver are fully synchronized.
	     */

	    /*
	     * We know the server response to every command that was sent.
	     * Apply a course correction if necessary: the sender wants to
	     * send RCPT TO but MAIL FROM was rejected; the sender wants to
	     * send DATA but all recipients were rejected; the sender wants
	     * to deliver the message but DATA was rejected.
	     */
	    if ((send_state == SMTP_STATE_RCPT && mail_from_rejected)
		|| (send_state == SMTP_STATE_DATA && nrcpt == 0)
		|| (send_state == SMTP_STATE_DOT && nrcpt < 0)) {
		send_state = recv_state = SMTP_STATE_ABORT;
		send_rcpt = recv_rcpt = 0;
		vstring_strcpy(next_command, "RSET");
		if (THIS_SESSION_IS_EXPIRED)
		    DONT_CACHE_THIS_SESSION;
		next_state = THIS_SESSION_IS_CACHED ?
		    SMTP_STATE_LAST : SMTP_STATE_QUIT;
		/* XXX Also: record if non-delivering session. */
		next_rcpt = 0;
	    }
	}

	/*
	 * Make the next sender state the current sender state.
	 */
	if (send_state == SMTP_STATE_LAST)
	    continue;

	/*
	 * Special case if the server accepted the DATA command. If the
	 * server accepted at least one recipient send the entire message.
	 * Otherwise, just send "." as per RFC 2197.
	 *
	 * XXX If there is a hard MIME error while downgrading to 7-bit mail,
	 * disconnect ungracefully, because there is no other way to cancel a
	 * transaction in progress.
	 */
	if (send_state == SMTP_STATE_DOT && nrcpt > 0) {

	    smtp_stream_setup(session->stream, var_smtp_data1_tmout,
			      var_smtp_req_deadline, var_smtp_min_data_rate);

	    if ((except = vstream_setjmp(session->stream)) == 0) {

		if (vstream_fseek(state->src, request->data_offset, SEEK_SET) < 0)
		    msg_fatal("seek queue file: %m");

		downgrading = SMTP_MIME_DOWNGRADE(session, request);

		/*
		 * XXX Don't downgrade just because generic_maps is turned
		 * on.
		 */
#define SMTP_ANY_CHECKS (smtp_header_checks || smtp_body_checks)

		if (downgrading || smtp_generic_maps || SMTP_ANY_CHECKS)
		    session->mime_state = mime_state_alloc(downgrading ?
							   MIME_OPT_DOWNGRADE
						 | MIME_OPT_REPORT_NESTING :
						      SMTP_ANY_CHECKS == 0 ?
						     MIME_OPT_DISABLE_MIME :
							   0,
							   smtp_generic_maps
						     || smtp_header_checks ?
						       smtp_header_rewrite :
							   smtp_header_out,
						     (MIME_STATE_ANY_END) 0,
							   smtp_body_checks ?
							 smtp_body_rewrite :
							   smtp_text_out,
						     (MIME_STATE_ANY_END) 0,
						   (MIME_STATE_ERR_PRINT) 0,
							   (void *) state);
		state->space_left = var_smtp_line_limit;

		if ((smtp_cli_attr.flags & SMTP_CLI_MASK_ADD_HEADERS) != 0
		    && smtp_out_add_headers(state) < 0)
		    RETURN(0);

		while ((rec_type = rec_get(state->src, session->scratch, 0)) > 0) {
		    if (rec_type != REC_TYPE_NORM && rec_type != REC_TYPE_CONT)
			break;
		    if (smtp_out_raw_or_mime(state, rec_type,
					     session->scratch) < 0)
			RETURN(0);
		    prev_type = rec_type;
		}

		if (session->mime_state) {

		    /*
		     * The cleanup server normally ends MIME content with a
		     * normal text record. The following code is needed to
		     * flush an internal buffer when someone submits 8-bit
		     * mail not ending in newline via /usr/sbin/sendmail
		     * while MIME input processing is turned off, and MIME
		     * 8bit->7bit conversion is requested upon delivery.
		     *
		     * Or some error while doing generic address mapping.
		     */
		    mime_errs =
			mime_state_update(session->mime_state, rec_type, "", 0);
		    if (mime_errs) {
			smtp_mime_fail(state, mime_errs);
			RETURN(0);
		    }
		} else if (prev_type == REC_TYPE_CONT)	/* missing newline */
		    smtp_fputs("", 0, session->stream);
		if (session->features & SMTP_FEATURE_PIX_DELAY_DOTCRLF) {
		    smtp_flush(session->stream);/* hurts performance */
		    sleep(var_smtp_pix_delay);	/* not to mention this */
		}
		if (vstream_ferror(state->src))
		    msg_fatal("queue file read error");
		if (rec_type != REC_TYPE_XTRA) {
		    msg_warn("%s: bad record type: %d in message content",
			     request->queue_id, rec_type);
		    fail_status = smtp_mesg_fail(state, DSN_BY_LOCAL_MTA,
					     SMTP_RESP_FAKE(&fake, "5.3.0"),
					     "unreadable mail queue entry");
		    /* Bailing out, abort stream with prejudice */
		    (void) vstream_fpurge(session->stream, VSTREAM_PURGE_BOTH);
		    DONT_USE_FORBIDDEN_SESSION;
		    /* If bounce_append() succeeded, status is still 0 */
		    if (state->status == 0)
			(void) mark_corrupt(state->src);
		    /* Don't override smtp_mesg_fail() here. */
		    RETURN(fail_status);
		}
	    } else {
		if (!LOST_CONNECTION_INSIDE_DATA)
		    RETURN(smtp_stream_except(state, except,
					      "sending message body"));

		/*
		 * We will clear the stream error flag to try and read a
		 * premature 5XX response, so it is important to flush any
		 * unwritten data. Otherwise, we will try to flush it again
		 * before reading, which may incur an unnecessary delay and
		 * will prevent the reading of any response that is not
		 * already buffered (bundled with the DATA 354 response).
		 *
		 * Not much point in sending QUIT at this point, skip right to
		 * SMTP_STATE_LAST. The read engine above will likewise avoid
		 * looking for a QUIT response.
		 */
		(void) vstream_fpurge(session->stream, VSTREAM_PURGE_WRITE);
		next_state = SMTP_STATE_LAST;
	    }
	}

	/*
	 * Copy the next command to the buffer and update the sender state.
	 */
	if (except == 0) {
	    smtp_chat_cmd(session, "%s", vstring_str(next_command));
	} else {
	    DONT_CACHE_THIS_SESSION;
	}
	send_state = next_state;
	send_rcpt = next_rcpt;
    } while (recv_state != SMTP_STATE_LAST);
    RETURN(0);
}

/* smtp_xfer - send a batch of envelope information and the message data */

int     smtp_xfer(SMTP_STATE *state)
{
    DELIVER_REQUEST *request = state->request;
    SMTP_SESSION *session = state->session;
    SMTP_RESP fake;
    int     send_state;
    int     recv_state;
    int     send_name_addr;
    int     result;

    /*
     * Sanity check. Recipients should be unmarked at this point.
     */
    if (SMTP_RCPT_LEFT(state) <= 0)
	msg_panic("smtp_xfer: bad recipient count: %d",
		  SMTP_RCPT_LEFT(state));
    if (SMTP_RCPT_ISMARKED(request->rcpt_list.info))
	msg_panic("smtp_xfer: bad recipient status: %d",
		  request->rcpt_list.info->u.status);

    /*
     * See if we should even try to send this message at all. This code sits
     * here rather than in the EHLO processing code, because of SMTP
     * connection caching.
     */
    if (session->size_limit > 0 && session->size_limit < request->data_size) {
	smtp_mesg_fail(state, DSN_BY_LOCAL_MTA,
		       SMTP_RESP_FAKE(&fake, "5.3.4"),
		    "message size %lu exceeds size limit %.0f of server %s",
		       request->data_size, (double) session->size_limit,
		       session->namaddr);
	/* Redundant. We abort this delivery attempt. */
	state->misc_flags |= SMTP_MISC_FLAG_COMPLETE_SESSION;
	return (0);
    }

    /*
     * Use XFORWARD to forward the origin of this email message across an
     * SMTP-based content filter. Send client attribute information only if
     * it exists (i.e. remote submission). Local submissions have no client
     * attributes; the mail will appear to originate from the content filter
     * which is acceptable.
     */
    send_name_addr =
	var_smtp_send_xforward
	&& (((session->features & SMTP_FEATURE_XFORWARD_NAME)
	     && CAN_FORWARD_CLIENT_NAME(request->client_name))
	    || ((session->features & SMTP_FEATURE_XFORWARD_ADDR)
		&& CAN_FORWARD_CLIENT_ADDR(request->client_addr))
	    || ((session->features & SMTP_FEATURE_XFORWARD_PORT)
		&& CAN_FORWARD_CLIENT_PORT(request->client_port)));
    session->send_proto_helo =
	var_smtp_send_xforward
	&& (((session->features & SMTP_FEATURE_XFORWARD_PROTO)
	     && CAN_FORWARD_PROTO_NAME(request->client_proto))
	    || ((session->features & SMTP_FEATURE_XFORWARD_HELO)
		&& CAN_FORWARD_HELO_NAME(request->client_helo))
	    || ((session->features & SMTP_FEATURE_XFORWARD_IDENT)
		&& CAN_FORWARD_IDENT_NAME(request->log_ident))
	    || ((session->features & SMTP_FEATURE_XFORWARD_DOMAIN)
		&& CAN_FORWARD_RWR_CONTEXT(request->rewrite_context)));
    if (send_name_addr)
	recv_state = send_state = SMTP_STATE_XFORWARD_NAME_ADDR;
    else if (session->send_proto_helo)
	recv_state = send_state = SMTP_STATE_XFORWARD_PROTO_HELO;
    else
	recv_state = send_state = SMTP_STATE_MAIL;

    /*
     * Remember this session's "normal completion", even if the server 4xx-ed
     * some or all recipients. Connection or handshake errors with a later MX
     * host should not cause this destination be marked as unreachable.
     */
    result = smtp_loop(state, send_state, recv_state);

    if (result == 0
    /* Just in case */
	&& vstream_ferror(session->stream) == 0
	&& vstream_feof(session->stream) == 0)
	state->misc_flags |= SMTP_MISC_FLAG_COMPLETE_SESSION;

    return (result);
}

/* smtp_rset - send a lone RSET command */

int     smtp_rset(SMTP_STATE *state)
{

    /*
     * This works because SMTP_STATE_RSET is a dedicated sender/recipient
     * entry state, with SMTP_STATE_LAST as next sender/recipient state.
     */
    return (smtp_loop(state, SMTP_STATE_RSET, SMTP_STATE_RSET));
}

/* smtp_quit - send a lone QUIT command */

int     smtp_quit(SMTP_STATE *state)
{

    /*
     * This works because SMTP_STATE_QUIT is the last state with a sender
     * action, with SMTP_STATE_LAST as the next sender/recipient state.
     */
    return (smtp_loop(state, SMTP_STATE_QUIT, var_skip_quit_resp ?
		      SMTP_STATE_LAST : SMTP_STATE_QUIT));
}