1 files changed, 476 insertions, 0 deletions

diff --git a/src/smtp/smtp_trouble.c b/src/smtp/smtp_trouble.c
new file mode 100644
index 0000000..60880df
--- /dev/null
+++ b/src/smtp/smtp_trouble.c
@@ -0,0 +1,476 @@
+/*++
+/* NAME
+/*	smtp_trouble 3
+/* SUMMARY
+/*	error handler policies
+/* SYNOPSIS
+/*	#include "smtp.h"
+/*
+/*	int	smtp_sess_fail(state)
+/*	SMTP_STATE *state;
+/*
+/*	int	smtp_site_fail(state, mta_name, resp, format, ...)
+/*	SMTP_STATE *state;
+/*	const char *mta_name;
+/*	SMTP_RESP *resp;
+/*	const char *format;
+/*
+/*	int	smtp_mesg_fail(state, mta_name, resp, format, ...)
+/*	SMTP_STATE *state;
+/*	const char *mta_name;
+/*	SMTP_RESP *resp;
+/*	const char *format;
+/*
+/*	void	smtp_rcpt_fail(state, recipient, mta_name, resp, format, ...)
+/*	SMTP_STATE *state;
+/*	RECIPIENT *recipient;
+/*	const char *mta_name;
+/*	SMTP_RESP *resp;
+/*	const char *format;
+/*
+/*	int	smtp_stream_except(state, exception, description)
+/*	SMTP_STATE *state;
+/*	int	exception;
+/*	const char *description;
+/* AUXILIARY FUNCTIONS
+/*	int	smtp_misc_fail(state, throttle, mta_name, resp, format, ...)
+/*	SMTP_STATE *state;
+/*	int	throttle;
+/*	const char *mta_name;
+/*	SMTP_RESP *resp;
+/*	const char *format;
+/* DESCRIPTION
+/*	This module handles all non-fatal errors that can happen while
+/*	attempting to deliver mail via SMTP, and implements the policy
+/*	of how to deal with the error. Depending on the nature of
+/*	the problem, delivery of a single message is deferred, delivery
+/*	of all messages to the same domain is deferred, or one or more
+/*	recipients are given up as non-deliverable and a bounce log is
+/*	updated. In any case, the recipient is marked as either KEEP
+/*	(try again with a backup host) or DROP (delete recipient from
+/*	delivery request).
+/*
+/*	In addition, when an unexpected response code is seen such
+/*	as 3xx where only 4xx or 5xx are expected, or any error code
+/*	that suggests a syntax error or something similar, the
+/*	protocol error flag is set so that the postmaster receives
+/*	a transcript of the session. No notification is generated for
+/*	what appear to be configuration errors - very likely, they
+/*	would suffer the same problem and just cause more trouble.
+/*
+/*	In case of a soft error, action depends on whether the error
+/*	qualifies for trying the request with other mail servers (log
+/*	an informational record only and try a backup server) or
+/*	whether this is the final server (log recipient delivery status
+/*	records and delete the recipient from the request).
+/*
+/*	smtp_sess_fail() takes a pre-formatted error report after
+/*	failure to complete some protocol handshake.  The policy is
+/*	as with smtp_site_fail().
+/*
+/*	smtp_site_fail() handles the case where the program fails to
+/*	complete the initial handshake: the server is not reachable,
+/*	is not running, does not want talk to us, or we talk to ourselves.
+/*	The \fIcode\fR gives an error status code; the \fIformat\fR
+/*	argument gives a textual description.
+/*	The policy is: soft error, non-final server: log an informational
+/*	record why the host is being skipped; soft error, final server:
+/*	defer delivery of all remaining recipients and mark the destination
+/*	as problematic; hard error: bounce all remaining recipients.
+/*	The session is marked as "do not cache".
+/*	The result is non-zero.
+/*
+/*	smtp_mesg_fail() handles the case where the smtp server
+/*	does not accept the sender address or the message data,
+/*	or when the local MTA is unable to convert the message data.
+/*	The policy is: soft error, non-final server: log an informational
+/*	record why the host is being skipped; soft error, final server:
+/*	defer delivery of all remaining recipients; hard error: bounce all
+/*	remaining recipients.
+/*	The result is non-zero.
+/*
+/*	smtp_misc_fail() provides a more detailed interface than
+/*	smtp_site_fail() and smtp_mesg_fail(), which are convenience
+/*	wrappers around smtp_misc_fail(). The throttle argument
+/*	is either SMTP_THROTTLE or SMTP_NOTHROTTLE; it is used only
+/*	in the "soft error, final server" policy, and determines
+/*	whether a destination will be marked as problematic.
+/*
+/*	smtp_rcpt_fail() handles the case where a recipient is not
+/*	accepted by the server for reasons other than that the server
+/*	recipient limit is reached.
+/*	The policy is: soft error, non-final server: log an informational
+/*	record why the recipient is being skipped; soft error, final server:
+/*	defer delivery of this recipient; hard error: bounce this
+/*	recipient.
+/*
+/*	smtp_stream_except() handles the exceptions generated by
+/*	the smtp_stream(3) module (i.e. timeouts and I/O errors).
+/*	The \fIexception\fR argument specifies the type of problem.
+/*	The \fIdescription\fR argument describes at what stage of
+/*	the SMTP dialog the problem happened.
+/*	The policy is: non-final server: log an informational record
+/*	with the reason why the host is being skipped; final server:
+/*	defer delivery of all remaining recipients.
+/*	Retry plaintext delivery after TLS post-handshake session
+/*	failure, provided that at least one recipient was not
+/*	deferred or rejected during the TLS phase, and that global
+/*	preconditions for plaintext fallback are met.
+/*	The session is marked as "do not cache".
+/*	The result is non-zero.
+/*
+/*	Arguments:
+/* .IP state
+/*	SMTP client state per delivery request.
+/* .IP resp
+/*	Server response including reply code and text.
+/* .IP recipient
+/*	Undeliverable recipient address information.
+/* .IP format
+/*	Human-readable description of why mail is not deliverable.
+/* DIAGNOSTICS
+/*	Panic: unknown exception code.
+/* SEE ALSO
+/*	smtp_proto(3) smtp high-level protocol
+/*	smtp_stream(3) smtp low-level protocol
+/*	defer(3) basic message defer interface
+/*	bounce(3) basic message bounce interface
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	IBM T.J. Watson Research
+/*	P.O. Box 704
+/*	Yorktown Heights, NY 10598, USA
+/*
+/*	Wietse Venema
+/*	Google, Inc.
+/*	111 8th Avenue
+/*	New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <stdlib.h>			/* 44BSD stdarg.h uses abort() */
+#include <stdarg.h>
+#include <string.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstring.h>
+#include <stringops.h>
+
+/* Global library. */
+
+#include <smtp_stream.h>
+#include <deliver_request.h>
+#include <deliver_completed.h>
+#include <bounce.h>
+#include <defer.h>
+#include <mail_error.h>
+#include <dsn_buf.h>
+#include <dsn.h>
+#include <mail_params.h>
+
+/* Application-specific. */
+
+#include "smtp.h"
+#include "smtp_sasl.h"
+
+/* smtp_check_code - check response code */
+
+static void smtp_check_code(SMTP_SESSION *session, int code)
+{
+
+    /*
+     * The intention of this code is to alert the postmaster when the local
+     * Postfix SMTP client screws up, protocol wise. RFC 821 says that x0z
+     * replies "refer to syntax errors, syntactically correct commands that
+     * don't fit any functional category, and unimplemented or superfluous
+     * commands". Unfortunately, this also triggers postmaster notices when
+     * remote servers screw up, protocol wise. This is becoming a common
+     * problem now that response codes are configured manually as part of
+     * anti-UCE systems, by people who aren't aware of RFC details.
+     * 
+     * Fix 20190621: don't cache an SMTP session after an SMTP protocol error.
+     * The protocol may be in a bad state. Disable caching here so that the
+     * protocol engine will send QUIT.
+     */
+    if (code < 400 || code > 599
+	|| code == 555			/* RFC 1869, section 6.1. */
+	|| (code >= 500 && code < 510)) {
+	session->error_mask |= MAIL_ERROR_PROTOCOL;
+	DONT_CACHE_THIS_SESSION;
+    }
+}
+
+/* smtp_bulk_fail - skip, defer or bounce recipients, maybe throttle queue */
+
+static int smtp_bulk_fail(SMTP_STATE *state, int throttle_queue)
+{
+    DELIVER_REQUEST *request = state->request;
+    SMTP_SESSION *session = state->session;
+    DSN_BUF *why = state->why;
+    RECIPIENT *rcpt;
+    int     status;
+    int     aggregate_status;
+    int     soft_error = (STR(why->status)[0] == '4');
+    int     soft_bounce_error = (STR(why->status)[0] == '5' && var_soft_bounce);
+    int     nrcpt;
+
+    /*
+     * Don't defer the recipients just yet when this error qualifies them for
+     * delivery to a backup server. Just log something informative to show
+     * why we're skipping this host.
+     */
+    if ((soft_error || soft_bounce_error)
+	&& (state->misc_flags & SMTP_MISC_FLAG_FINAL_SERVER) == 0) {
+	msg_info("%s: %s", request->queue_id, STR(why->reason));
+	for (nrcpt = 0; nrcpt < SMTP_RCPT_LEFT(state); nrcpt++) {
+	    rcpt = request->rcpt_list.info + nrcpt;
+	    if (SMTP_RCPT_ISMARKED(rcpt))
+		continue;
+	    SMTP_RCPT_KEEP(state, rcpt);
+	}
+    }
+
+    /*
+     * Defer or bounce all the remaining recipients, and delete them from the
+     * delivery request. If a bounce fails, defer instead and do not qualify
+     * the recipient for delivery to a backup server.
+     */
+    else {
+
+	/*
+	 * If we are still in the connection set-up phase, update the set-up
+	 * completion time here, otherwise the time spent in set-up latency
+	 * will be attributed as message transfer latency.
+	 * 
+	 * All remaining recipients have failed at this point, so we update the
+	 * delivery completion time stamp so that multiple recipient status
+	 * records show the same delay values.
+	 */
+	if (request->msg_stats.conn_setup_done.tv_sec == 0) {
+	    GETTIMEOFDAY(&request->msg_stats.conn_setup_done);
+	    request->msg_stats.deliver_done =
+		request->msg_stats.conn_setup_done;
+	} else
+	    GETTIMEOFDAY(&request->msg_stats.deliver_done);
+
+	(void) DSN_FROM_DSN_BUF(why);
+	aggregate_status = 0;
+	for (nrcpt = 0; nrcpt < SMTP_RCPT_LEFT(state); nrcpt++) {
+	    rcpt = request->rcpt_list.info + nrcpt;
+	    if (SMTP_RCPT_ISMARKED(rcpt))
+		continue;
+	    status = (soft_error ? defer_append : bounce_append)
+		(DEL_REQ_TRACE_FLAGS(request->flags), request->queue_id,
+		 &request->msg_stats, rcpt,
+		 session ? session->namaddrport : "none", &why->dsn);
+	    if (status == 0)
+		deliver_completed(state->src, rcpt->offset);
+	    SMTP_RCPT_DROP(state, rcpt);
+	    aggregate_status |= status;
+	}
+	state->status |= aggregate_status;
+	if ((state->misc_flags & SMTP_MISC_FLAG_COMPLETE_SESSION) == 0
+	    && throttle_queue && aggregate_status
+	    && request->hop_status == 0)
+	    request->hop_status = DSN_COPY(&why->dsn);
+    }
+
+    /*
+     * Don't cache this session. We can't talk to this server.
+     */
+    if (throttle_queue && session)
+	DONT_CACHE_THROTTLED_SESSION;
+
+    return (-1);
+}
+
+/* smtp_sess_fail - skip site, defer or bounce all recipients */
+
+int     smtp_sess_fail(SMTP_STATE *state)
+{
+
+    /*
+     * We can't avoid copying copying lots of strings into VSTRING buffers,
+     * because this error information is collected by a routine that
+     * terminates BEFORE the error is reported.
+     */
+    return (smtp_bulk_fail(state, SMTP_THROTTLE));
+}
+
+/* vsmtp_fill_dsn - fill in temporary DSN structure */
+
+static void vsmtp_fill_dsn(SMTP_STATE *state, const char *mta_name,
+			           const char *status, const char *reply,
+			           const char *format, va_list ap)
+{
+    DSN_BUF *why = state->why;
+
+    /*
+     * We could avoid copying lots of strings into VSTRING buffers, because
+     * this error information is given to us by a routine that terminates
+     * AFTER the error is reported. However, this results in ugly kludges
+     * when informal text needs to be formatted. So we maintain consistency
+     * with other error reporting in the SMTP client even if we waste a few
+     * cycles.
+     * 
+     * Fix 20190621: don't cache an SMTP session after an SMTP protocol error.
+     * The protocol may be in a bad state. Disable caching here so that the
+     * protocol engine will send QUIT.
+     */
+    VSTRING_RESET(why->reason);
+    if (mta_name && status && status[0] != '4' && status[0] != '5') {
+	SMTP_SESSION *session = state->session;
+
+	session->error_mask |= MAIL_ERROR_PROTOCOL;
+	DONT_CACHE_THIS_SESSION;
+	vstring_strcpy(why->reason, "Protocol error: ");
+	status = "5.5.0";
+    }
+    vstring_vsprintf_append(why->reason, format, ap);
+    dsb_formal(why, status, DSB_DEF_ACTION,
+	       mta_name ? DSB_MTYPE_DNS : DSB_MTYPE_NONE, mta_name,
+	       reply ? DSB_DTYPE_SMTP : DSB_DTYPE_NONE, reply);
+}
+
+/* smtp_misc_fail - maybe throttle queue; skip/defer/bounce all recipients */
+
+int     smtp_misc_fail(SMTP_STATE *state, int throttle, const char *mta_name,
+		               SMTP_RESP *resp, const char *format,...)
+{
+    va_list ap;
+
+    /*
+     * Initialize.
+     */
+    va_start(ap, format);
+    vsmtp_fill_dsn(state, mta_name, resp->dsn, resp->str, format, ap);
+    va_end(ap);
+
+    if (state->session && mta_name)
+	smtp_check_code(state->session, resp->code);
+
+    /*
+     * Skip, defer or bounce recipients, and throttle this queue.
+     */
+    return (smtp_bulk_fail(state, throttle));
+}
+
+/* smtp_rcpt_fail - skip, defer, or bounce recipient */
+
+void    smtp_rcpt_fail(SMTP_STATE *state, RECIPIENT *rcpt, const char *mta_name,
+		               SMTP_RESP *resp, const char *format,...)
+{
+    DELIVER_REQUEST *request = state->request;
+    SMTP_SESSION *session = state->session;
+    DSN_BUF *why = state->why;
+    int     status;
+    int     soft_error;
+    int     soft_bounce_error;
+    va_list ap;
+
+    /*
+     * Sanity check.
+     */
+    if (SMTP_RCPT_ISMARKED(rcpt))
+	msg_panic("smtp_rcpt_fail: recipient <%s> is marked", rcpt->address);
+
+    /*
+     * Initialize.
+     */
+    va_start(ap, format);
+    vsmtp_fill_dsn(state, mta_name, resp->dsn, resp->str, format, ap);
+    va_end(ap);
+    soft_error = STR(why->status)[0] == '4';
+    soft_bounce_error = (STR(why->status)[0] == '5' && var_soft_bounce);
+
+    if (state->session && mta_name)
+	smtp_check_code(state->session, resp->code);
+
+    /*
+     * Don't defer this recipient record just yet when this error qualifies
+     * for trying other mail servers. Just log something informative to show
+     * why we're skipping this recipient now.
+     */
+    if ((soft_error || soft_bounce_error)
+	&& (state->misc_flags & SMTP_MISC_FLAG_FINAL_SERVER) == 0) {
+	msg_info("%s: %s", request->queue_id, STR(why->reason));
+	SMTP_RCPT_KEEP(state, rcpt);
+    }
+
+    /*
+     * Defer or bounce this recipient, and delete from the delivery request.
+     * If the bounce fails, defer instead and do not qualify the recipient
+     * for delivery to a backup server.
+     * 
+     * Note: we may still make an SMTP connection to deliver other recipients
+     * that did qualify for delivery to a backup server.
+     */
+    else {
+	(void) DSN_FROM_DSN_BUF(state->why);
+	status = (soft_error ? defer_append : bounce_append)
+	    (DEL_REQ_TRACE_FLAGS(request->flags), request->queue_id,
+	     &request->msg_stats, rcpt,
+	     session ? session->namaddrport : "none", &why->dsn);
+	if (status == 0)
+	    deliver_completed(state->src, rcpt->offset);
+	SMTP_RCPT_DROP(state, rcpt);
+	state->status |= status;
+    }
+}
+
+/* smtp_stream_except - defer domain after I/O problem */
+
+int     smtp_stream_except(SMTP_STATE *state, int code, const char *description)
+{
+    SMTP_SESSION *session = state->session;
+    DSN_BUF *why = state->why;
+
+    /*
+     * Sanity check.
+     */
+    if (session == 0)
+	msg_panic("smtp_stream_except: no session");
+
+    /*
+     * Initialize.
+     */
+    switch (code) {
+    default:
+	msg_panic("smtp_stream_except: unknown exception %d", code);
+    case SMTP_ERR_EOF:
+	dsb_simple(why, "4.4.2", "lost connection with %s while %s",
+		   session->namaddr, description);
+#ifdef USE_TLS
+	if (PLAINTEXT_FALLBACK_OK_AFTER_TLS_SESSION_FAILURE)
+	    RETRY_AS_PLAINTEXT;
+#endif
+	break;
+    case SMTP_ERR_TIME:
+	dsb_simple(why, "4.4.2", "conversation with %s timed out while %s",
+		   session->namaddr, description);
+#ifdef USE_TLS
+	if (PLAINTEXT_FALLBACK_OK_AFTER_TLS_SESSION_FAILURE)
+	    RETRY_AS_PLAINTEXT;
+#endif
+	break;
+    case SMTP_ERR_DATA:
+	session->error_mask |= MAIL_ERROR_DATA;
+	dsb_simple(why, "4.3.0", "local data error while talking to %s",
+		   session->namaddr);
+    }
+
+    /*
+     * The smtp_bulk_fail() call below will not throttle the destination when
+     * falling back to plaintext, because RETRY_AS_PLAINTEXT clears the
+     * FINAL_SERVER flag.
+     */
+    return (smtp_bulk_fail(state, SMTP_THROTTLE));
+}