1 /*	$NetBSD: postdrop.c,v 1.4 2022/10/08 16:12:47 christos Exp $	*/
2 
3 /*++
4 /* NAME
5 /*	postdrop 1
6 /* SUMMARY
7 /*	Postfix mail posting utility
8 /* SYNOPSIS
9 /*	\fBpostdrop\fR [\fB-rv\fR] [\fB-c \fIconfig_dir\fR]
10 /* DESCRIPTION
11 /*	The \fBpostdrop\fR(1) command creates a file in the \fBmaildrop\fR
12 /*	directory and copies its standard input to the file.
13 /*
14 /*	Options:
15 /* .IP "\fB-c \fIconfig_dir\fR"
16 /*	The \fBmain.cf\fR configuration file is in the named directory
17 /*	instead of the default configuration directory. See also the
18 /*	MAIL_CONFIG environment setting below.
19 /* .IP \fB-r\fR
20 /*	Use a Postfix-internal protocol for reading the message from
21 /*	standard input, and for reporting status information on standard
22 /*	output. This is currently the only supported method.
23 /* .IP \fB-v\fR
24 /*	Enable verbose logging for debugging purposes. Multiple \fB-v\fR
25 /*	options make the software increasingly verbose. As of Postfix 2.3,
26 /*	this option is available for the super-user only.
27 /* SECURITY
28 /* .ad
29 /* .fi
30 /*	The command is designed to run with set-group ID privileges, so
31 /*	that it can write to the \fBmaildrop\fR queue directory and so that
32 /*	it can connect to Postfix daemon processes.
33 /* DIAGNOSTICS
34 /*	Fatal errors: malformed input, I/O error, out of memory. Problems
35 /*	are logged to \fBsyslogd\fR(8) or \fBpostlogd\fR(8) and to
36 /*	the standard error stream.
37 /*	When the input is incomplete, or when the process receives a HUP,
38 /*	INT, QUIT or TERM signal, the queue file is deleted.
39 /* ENVIRONMENT
40 /* .ad
41 /* .fi
42 /* .IP MAIL_CONFIG
43 /*	Directory with the \fBmain.cf\fR file. In order to avoid exploitation
44 /*	of set-group ID privileges, a non-standard directory is allowed only
45 /*	if:
46 /* .RS
47 /* .IP \(bu
48 /*	The name is listed in the standard \fBmain.cf\fR file with the
49 /*	\fBalternate_config_directories\fR configuration parameter.
50 /* .IP \(bu
51 /*	The command is invoked by the super-user.
52 /* .RE
53 /* CONFIGURATION PARAMETERS
54 /* .ad
55 /* .fi
56 /*	The following \fBmain.cf\fR parameters are especially relevant to
57 /*	this program.
58 /*	The text below provides only a parameter summary. See
59 /*	\fBpostconf\fR(5) for more details including examples.
60 /* .IP "\fBalternate_config_directories (empty)\fR"
61 /*	A list of non-default Postfix configuration directories that may
62 /*	be specified with "-c config_directory" on the command line (in the
63 /*	case of \fBsendmail\fR(1), with the "-C" option), or via the MAIL_CONFIG
64 /*	environment parameter.
65 /* .IP "\fBconfig_directory (see 'postconf -d' output)\fR"
66 /*	The default location of the Postfix main.cf and master.cf
67 /*	configuration files.
68 /* .IP "\fBimport_environment (see 'postconf -d' output)\fR"
69 /*	The list of environment parameters that a privileged Postfix
70 /*	process will import from a non-Postfix parent process, or name=value
71 /*	environment overrides.
72 /* .IP "\fBqueue_directory (see 'postconf -d' output)\fR"
73 /*	The location of the Postfix top-level queue directory.
74 /* .IP "\fBsyslog_facility (mail)\fR"
75 /*	The syslog facility of Postfix logging.
76 /* .IP "\fBsyslog_name (see 'postconf -d' output)\fR"
77 /*	A prefix that is prepended to the process name in syslog
78 /*	records, so that, for example, "smtpd" becomes "prefix/smtpd".
79 /* .IP "\fBtrigger_timeout (10s)\fR"
80 /*	The time limit for sending a trigger to a Postfix daemon (for
81 /*	example, the \fBpickup\fR(8) or \fBqmgr\fR(8) daemon).
82 /* .PP
83 /*	Available in Postfix version 2.2 and later:
84 /* .IP "\fBauthorized_submit_users (static:anyone)\fR"
85 /*	List of users who are authorized to submit mail with the \fBsendmail\fR(1)
86 /*	command (and with the privileged \fBpostdrop\fR(1) helper command).
87 /* .PP
88 /*	Available in Postfix version 3.6 and later:
89 /* .IP "\fBlocal_login_sender_maps (static:*)\fR"
90 /*	A list of lookup tables that are searched by the UNIX login name,
91 /*	and that return a list of allowed envelope sender patterns separated
92 /*	by space or comma.
93 /* .IP "\fBempty_address_local_login_sender_maps_lookup_key (<>)\fR"
94 /*	The lookup key to be used in local_login_sender_maps tables, instead
95 /*	of the null sender address.
96 /* .IP "\fBrecipient_delimiter (empty)\fR"
97 /*	The set of characters that can separate an email address
98 /*	localpart, user name, or a .forward file name from its extension.
99 /* FILES
100 /*	/var/spool/postfix/maildrop, maildrop queue
101 /* SEE ALSO
102 /*	sendmail(1), compatibility interface
103 /*	postconf(5), configuration parameters
104 /*	postlogd(8), Postfix logging
105 /*	syslogd(8), system logging
106 /* LICENSE
107 /* .ad
108 /* .fi
109 /*	The Secure Mailer license must be distributed with this software.
110 /* AUTHOR(S)
111 /*	Wietse Venema
112 /*	IBM T.J. Watson Research
113 /*	P.O. Box 704
114 /*	Yorktown Heights, NY 10598, USA
115 /*
116 /*	Wietse Venema
117 /*	Google, Inc.
118 /*	111 8th Avenue
119 /*	New York, NY 10011, USA
120 /*--*/
121 
122 /* System library. */
123 
124 #include <sys_defs.h>
125 #include <sys/stat.h>
126 #include <unistd.h>
127 #include <stdlib.h>
128 #include <stdio.h>			/* remove() */
129 #include <string.h>
130 #include <stdlib.h>
131 #include <signal.h>
132 #include <errno.h>
133 #include <warn_stat.h>
134 
135 /* Utility library. */
136 
137 #include <msg.h>
138 #include <mymalloc.h>
139 #include <vstream.h>
140 #include <vstring.h>
141 #include <msg_vstream.h>
142 #include <argv.h>
143 #include <iostuff.h>
144 #include <stringops.h>
145 #include <mypwd.h>
146 
147 /* Global library. */
148 
149 #include <mail_proto.h>
150 #include <mail_queue.h>
151 #include <mail_params.h>
152 #include <mail_version.h>
153 #include <mail_conf.h>
154 #include <mail_task.h>
155 #include <clean_env.h>
156 #include <mail_stream.h>
157 #include <cleanup_user.h>
158 #include <record.h>
159 #include <rec_type.h>
160 #include <mail_dict.h>
161 #include <user_acl.h>
162 #include <rec_attr_map.h>
163 #include <mail_parm_split.h>
164 #include <maillog_client.h>
165 #include <login_sender_match.h>
166 
167 /* Application-specific. */
168 
169  /*
170   * WARNING WARNING WARNING
171   *
172   * This software is designed to run set-gid. In order to avoid exploitation of
173   * privilege, this software should not run any external commands, nor should
174   * it take any information from the user unless that information can be
175   * properly sanitized. To get an idea of how much information a process can
176   * inherit from a potentially hostile user, examine all the members of the
177   * process structure (typically, in /usr/include/sys/proc.h): the current
178   * directory, open files, timers, signals, environment, command line, umask,
179   * and so on.
180   */
181 
182  /*
183   * Local mail submission access list.
184   */
185 char   *var_submit_acl;
186 char   *var_local_login_snd_maps;
187 char   *var_null_local_login_snd_maps_key;
188 
189 static const CONFIG_STR_TABLE str_table[] = {
190     VAR_SUBMIT_ACL, DEF_SUBMIT_ACL, &var_submit_acl, 0, 0,
191     VAR_LOCAL_LOGIN_SND_MAPS, DEF_LOCAL_LOGIN_SND_MAPS, &var_local_login_snd_maps, 0, 0,
192     VAR_NULL_LOCAL_LOGIN_SND_MAPS_KEY, DEF_NULL_LOCAL_LOGIN_SND_MAPS_KEY, &var_null_local_login_snd_maps_key, 0, 0,
193     0,
194 };
195 
196  /*
197   * Queue file name. Global, so that the cleanup routine can find it when
198   * called by the run-time error handler.
199   */
200 static char *postdrop_path;
201 
202 /* postdrop_sig - catch signal and clean up */
203 
postdrop_sig(int sig)204 static void postdrop_sig(int sig)
205 {
206 
207     /*
208      * This is the fatal error handler. Don't try to do anything fancy.
209      *
210      * To avoid privilege escalation in a set-gid program, Postfix logging
211      * functions must not be called from a user-triggered signal handler,
212      * because Postfix logging functions may allocate memory on the fly (as
213      * does the syslog() library function), and the memory allocator is not
214      * reentrant.
215      *
216      * Assume atomic signal() updates, even when emulated with sigaction(). We
217      * use the in-kernel SIGINT handler address as an atomic variable to
218      * prevent nested postdrop_sig() calls. For this reason, main() must
219      * configure postdrop_sig() as SIGINT handler before other signal
220      * handlers are allowed to invoke postdrop_sig().
221      */
222     if (signal(SIGINT, SIG_IGN) != SIG_IGN) {
223 	(void) signal(SIGQUIT, SIG_IGN);
224 	(void) signal(SIGTERM, SIG_IGN);
225 	(void) signal(SIGHUP, SIG_IGN);
226 	if (postdrop_path) {
227 	    (void) remove(postdrop_path);
228 	    postdrop_path = 0;
229 	}
230 	/* Future proofing. If you need exit() here then you broke Postfix. */
231 	if (sig)
232 	    _exit(sig);
233     }
234 }
235 
236 /* postdrop_cleanup - callback for the runtime error handler */
237 
postdrop_cleanup(void)238 static void postdrop_cleanup(void)
239 {
240     postdrop_sig(0);
241 }
242 
243 /* check_login_sender_acl - check if a user is authorized to use this sender */
244 
check_login_sender_acl(uid_t uid,VSTRING * sender_buf,VSTRING * reason)245 static int check_login_sender_acl(uid_t uid, VSTRING *sender_buf,
246 				          VSTRING *reason)
247 {
248     const char myname[] = "check_login_sender_acl";
249     struct mypasswd *user_info;
250     char   *user_name;
251     VSTRING *user_name_buf = 0;
252     LOGIN_SENDER_MATCH *lsm;
253     int     res;
254 
255     /*
256      * Sanity checks.
257      */
258     if (vstring_memchr(sender_buf, '\0') != 0) {
259 	vstring_sprintf(reason, "NUL in FROM record");
260 	return (CLEANUP_STAT_BAD);
261     }
262 
263     /*
264      * Optimization.
265      */
266 #ifndef SNAPSHOT
267     if (strcmp(var_local_login_snd_maps, DEF_LOCAL_LOGIN_SND_MAPS) == 0)
268 	return (CLEANUP_STAT_OK);
269 #endif
270 
271     /*
272      * Get the username.
273      */
274     if ((user_info = mypwuid(uid)) != 0) {
275 	user_name = user_info->pw_name;
276     } else {
277 	user_name_buf = vstring_alloc(10);
278 	vstring_sprintf(user_name_buf, "uid:%ld", (long) uid);
279 	user_name = vstring_str(user_name_buf);
280     }
281 
282 
283     /*
284      * Apply the a login-sender matcher. TODO: add DICT flags.
285      */
286     lsm = login_sender_create(VAR_LOCAL_LOGIN_SND_MAPS,
287 			      var_local_login_snd_maps,
288 			      var_rcpt_delim,
289 			      var_null_local_login_snd_maps_key, "*");
290     res = login_sender_match(lsm, user_name, vstring_str(sender_buf));
291     login_sender_free(lsm);
292     if (user_name_buf)
293 	vstring_free(user_name_buf);
294     switch (res) {
295     case LSM_STAT_FOUND:
296 	return (CLEANUP_STAT_OK);
297     case LSM_STAT_NOTFOUND:
298 	vstring_sprintf(reason, "not authorized to use sender='%s'",
299 			vstring_str(sender_buf));
300 	return (CLEANUP_STAT_NOPERM);
301     case LSM_STAT_RETRY:
302     case LSM_STAT_CONFIG:
303 	vstring_sprintf(reason, "%s table lookup error for '%s'",
304 			VAR_LOCAL_LOGIN_SND_MAPS, var_local_login_snd_maps);
305 	return (CLEANUP_STAT_WRITE);
306     default:
307 	msg_panic("%s: bad login_sender_match() result: %d", myname, res);
308     }
309 }
310 
311 MAIL_VERSION_STAMP_DECLARE;
312 
313 /* main - the main program */
314 
main(int argc,char ** argv)315 int     main(int argc, char **argv)
316 {
317     struct stat st;
318     int     fd;
319     int     c;
320     VSTRING *buf;
321     int     status = CLEANUP_STAT_OK;
322     VSTRING *reason = vstring_alloc(100);
323     MAIL_STREAM *dst;
324     int     rec_type;
325     static char *segment_info[] = {
326 	REC_TYPE_POST_ENVELOPE, REC_TYPE_POST_CONTENT, REC_TYPE_POST_EXTRACT, ""
327     };
328     char  **expected;
329     uid_t   uid = getuid();
330     ARGV   *import_env;
331     const char *error_text;
332     char   *attr_name;
333     char   *attr_value;
334     const char *errstr;
335     char   *junk;
336     struct timeval start;
337     int     saved_errno;
338     int     from_count = 0;
339     int     rcpt_count = 0;
340     int     validate_input = 1;
341 
342     /*
343      * Fingerprint executables and core dumps.
344      */
345     MAIL_VERSION_STAMP_ALLOCATE;
346 
347     /*
348      * Be consistent with file permissions.
349      */
350     umask(022);
351 
352     /*
353      * To minimize confusion, make sure that the standard file descriptors
354      * are open before opening anything else. XXX Work around for 44BSD where
355      * fstat can return EBADF on an open file descriptor.
356      */
357     for (fd = 0; fd < 3; fd++)
358 	if (fstat(fd, &st) == -1
359 	    && (close(fd), open("/dev/null", O_RDWR, 0)) != fd)
360 	    msg_fatal("open /dev/null: %m");
361 
362     /*
363      * Set up logging. Censor the process name: it is provided by the user.
364      */
365     argv[0] = "postdrop";
366     msg_vstream_init(argv[0], VSTREAM_ERR);
367     maillog_client_init(mail_task("postdrop"), MAILLOG_CLIENT_FLAG_NONE);
368     set_mail_conf_str(VAR_PROCNAME, var_procname = mystrdup(argv[0]));
369 
370     /*
371      * Check the Postfix library version as soon as we enable logging.
372      */
373     MAIL_VERSION_CHECK;
374 
375     /*
376      * Parse JCL. This program is set-gid and must sanitize all command-line
377      * arguments. The configuration directory argument is validated by the
378      * mail configuration read routine. Don't do complex things until we have
379      * completed initializations.
380      */
381     while ((c = GETOPT(argc, argv, "c:rv")) > 0) {
382 	switch (c) {
383 	case 'c':
384 	    if (setenv(CONF_ENV_PATH, optarg, 1) < 0)
385 		msg_fatal("out of memory");
386 	    break;
387 	case 'r':				/* forward compatibility */
388 	    break;
389 	case 'v':
390 	    if (geteuid() == 0)
391 		msg_verbose++;
392 	    break;
393 	default:
394 	    msg_fatal("usage: %s [-c config_dir] [-v]", argv[0]);
395 	}
396     }
397 
398     /*
399      * Read the global configuration file and extract configuration
400      * information.
401      */
402     mail_conf_read();
403     /* Re-evaluate mail_task() after reading main.cf. */
404     maillog_client_init(mail_task("postdrop"), MAILLOG_CLIENT_FLAG_NONE);
405     get_mail_conf_str_table(str_table);
406 
407     /*
408      * Stop run-away process accidents by limiting the queue file size. This
409      * is not a defense against DOS attack.
410      */
411     if (ENFORCING_SIZE_LIMIT(var_message_limit)
412 	&& get_file_limit() > var_message_limit)
413 	set_file_limit((off_t) var_message_limit);
414 
415     /*
416      * This program is installed with setgid privileges. Strip the process
417      * environment so that we don't have to trust the C library.
418      */
419     import_env = mail_parm_split(VAR_IMPORT_ENVIRON, var_import_environ);
420     clean_env(import_env->argv);
421     argv_free(import_env);
422 
423     if (chdir(var_queue_dir))
424 	msg_fatal("chdir %s: %m", var_queue_dir);
425     if (msg_verbose)
426 	msg_info("chdir %s", var_queue_dir);
427 
428     /*
429      * Set up signal handlers and a runtime error handler so that we can
430      * clean up incomplete output.
431      *
432      * postdrop_sig() uses the in-kernel SIGINT handler address as an atomic
433      * variable to prevent nested postdrop_sig() calls. For this reason, the
434      * SIGINT handler must be configured before other signal handlers are
435      * allowed to invoke postdrop_sig().
436      */
437     signal(SIGPIPE, SIG_IGN);
438     signal(SIGXFSZ, SIG_IGN);
439 
440     signal(SIGINT, postdrop_sig);
441     signal(SIGQUIT, postdrop_sig);
442     if (signal(SIGTERM, SIG_IGN) == SIG_DFL)
443 	signal(SIGTERM, postdrop_sig);
444     if (signal(SIGHUP, SIG_IGN) == SIG_DFL)
445 	signal(SIGHUP, postdrop_sig);
446     msg_cleanup(postdrop_cleanup);
447 
448     /* End of initializations. */
449 
450     /*
451      * Mail submission access control. Should this be in the user-land gate,
452      * or in the daemon process?
453      */
454     mail_dict_init();
455     if ((errstr = check_user_acl_byuid(VAR_SUBMIT_ACL, var_submit_acl,
456 				       uid)) != 0)
457 	msg_fatal("User %s(%ld) is not allowed to submit mail",
458 		  errstr, (long) uid);
459 
460     /*
461      * Don't trust the caller's time information.
462      */
463     GETTIMEOFDAY(&start);
464 
465     /*
466      * Create queue file. mail_stream_file() never fails. Send the queue ID
467      * to the caller. Stash away a copy of the queue file name so we can
468      * clean up in case of a fatal error or an interrupt.
469      */
470     dst = mail_stream_file(MAIL_QUEUE_MAILDROP, MAIL_CLASS_PUBLIC,
471 			   var_pickup_service, 0444);
472     attr_print(VSTREAM_OUT, ATTR_FLAG_NONE,
473 	       SEND_ATTR_STR(MAIL_ATTR_PROTO, MAIL_ATTR_PROTO_POSTDROP),
474 	       SEND_ATTR_STR(MAIL_ATTR_QUEUEID, dst->id),
475 	       ATTR_TYPE_END);
476     vstream_fflush(VSTREAM_OUT);
477     postdrop_path = mystrdup(VSTREAM_PATH(dst->stream));
478 
479     /*
480      * Copy stdin to file. The format is checked so that we can recognize
481      * incomplete input and cancel the operation. With the sanity checks
482      * applied here, the pickup daemon could skip format checks and pass a
483      * file descriptor to the cleanup daemon. These are by no means all
484      * sanity checks - the cleanup service and queue manager services will
485      * reject messages that lack required information.
486      *
487      * If something goes wrong, slurp up the input before responding to the
488      * client, otherwise the client will give up after detecting SIGPIPE.
489      *
490      * Allow attribute records if the attribute specifies the MIME body type
491      * (sendmail -B).
492      */
493     vstream_control(VSTREAM_IN, CA_VSTREAM_CTL_PATH("stdin"), CA_VSTREAM_CTL_END);
494     buf = vstring_alloc(100);
495     expected = segment_info;
496     /* Override time information from the untrusted caller. */
497     rec_fprintf(dst->stream, REC_TYPE_TIME, REC_TYPE_TIME_FORMAT,
498 		REC_TYPE_TIME_ARG(start));
499     for (;;) {
500 	/* Don't allow PTR records. */
501 	rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit, REC_FLAG_NONE);
502 	if (rec_type == REC_TYPE_EOF) {		/* request canceled */
503 	    mail_stream_cleanup(dst);
504 	    if (remove(postdrop_path))
505 		msg_warn("uid=%ld: remove %s: %m", (long) uid, postdrop_path);
506 	    else if (msg_verbose)
507 		msg_info("remove %s", postdrop_path);
508 	    myfree(postdrop_path);
509 	    postdrop_path = 0;
510 	    exit(0);
511 	}
512 	if (rec_type == REC_TYPE_ERROR)
513 	    msg_fatal("uid=%ld: malformed input", (long) uid);
514 	if (strchr(*expected, rec_type) == 0)
515 	    msg_fatal("uid=%ld: unexpected record type: %d", (long) uid, rec_type);
516 	if (rec_type == **expected)
517 	    expected++;
518 	/* Override time information from the untrusted caller. */
519 	if (rec_type == REC_TYPE_TIME)
520 	    continue;
521 	/* Check these at submission time instead of pickup time. */
522 	if (rec_type == REC_TYPE_FROM) {
523 	    status |= check_login_sender_acl(uid, buf, reason);
524 	    from_count++;
525 	}
526 	if (rec_type == REC_TYPE_RCPT)
527 	    rcpt_count++;
528 	/* Limit the attribute types that users may specify. */
529 	if (rec_type == REC_TYPE_ATTR) {
530 	    if ((error_text = split_nameval(vstring_str(buf), &attr_name,
531 					    &attr_value)) != 0) {
532 		msg_warn("uid=%ld: ignoring malformed record: %s: %.200s",
533 			 (long) uid, error_text, vstring_str(buf));
534 		continue;
535 	    }
536 #define STREQ(x,y) (strcmp(x,y) == 0)
537 
538 	    if ((STREQ(attr_name, MAIL_ATTR_ENCODING)
539 		 && (STREQ(attr_value, MAIL_ATTR_ENC_7BIT)
540 		     || STREQ(attr_value, MAIL_ATTR_ENC_8BIT)
541 		     || STREQ(attr_value, MAIL_ATTR_ENC_NONE)))
542 		|| STREQ(attr_name, MAIL_ATTR_DSN_ENVID)
543 		|| STREQ(attr_name, MAIL_ATTR_DSN_NOTIFY)
544 		|| rec_attr_map(attr_name)
545 		|| (STREQ(attr_name, MAIL_ATTR_RWR_CONTEXT)
546 		    && (STREQ(attr_value, MAIL_ATTR_RWR_LOCAL)
547 			|| STREQ(attr_value, MAIL_ATTR_RWR_REMOTE)))
548 		|| STREQ(attr_name, MAIL_ATTR_TRACE_FLAGS)) {	/* XXX */
549 		rec_fprintf(dst->stream, REC_TYPE_ATTR, "%s=%s",
550 			    attr_name, attr_value);
551 	    } else {
552 		msg_warn("uid=%ld: ignoring attribute record: %.200s=%.200s",
553 			 (long) uid, attr_name, attr_value);
554 	    }
555 	    continue;
556 	}
557 	if (status != CLEANUP_STAT_OK
558 	    || REC_PUT_BUF(dst->stream, rec_type, buf) < 0) {
559 	    /* rec_get() errors must not clobber errno. */
560 	    saved_errno = errno;
561 	    while ((rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit,
562 					   REC_FLAG_NONE)) != REC_TYPE_END
563 		   && rec_type != REC_TYPE_EOF)
564 		if (rec_type == REC_TYPE_ERROR)
565 		    msg_fatal("uid=%ld: malformed input", (long) uid);
566 	    validate_input = 0;
567 	    errno = saved_errno;
568 	    break;
569 	}
570 	if (rec_type == REC_TYPE_END)
571 	    break;
572     }
573     vstring_free(buf);
574 
575     /*
576      * As of Postfix 2.7 the pickup daemon discards mail without recipients.
577      * Such mail may enter the maildrop queue when "postsuper -r" is invoked
578      * before the queue manager deletes an already delivered message. Looking
579      * at file ownership is not a good way to make decisions on what mail to
580      * discard. Instead, the pickup server now requires that new submissions
581      * always have at least one recipient record.
582      *
583      * The Postfix sendmail command already rejects mail without recipients.
584      * However, in the future postdrop may receive mail via other programs,
585      * so we add a redundant recipient check here for future proofing.
586      *
587      * The test for the sender address is just for consistency of error
588      * reporting (report at submission time instead of pickup time). Besides
589      * the segment terminator records, there aren't any other mandatory
590      * records in a Postfix submission queue file.
591      *
592      * TODO: return an informative reason for missing sender, too many senders,
593      * or missing recipient.
594      */
595     if (validate_input && (from_count == 0 || rcpt_count == 0))
596 	status |= CLEANUP_STAT_BAD;
597     if (status != CLEANUP_STAT_OK) {
598 	mail_stream_cleanup(dst);
599     }
600 
601     /*
602      * Finish the file.
603      */
604     else if ((status = mail_stream_finish(dst, reason)) != 0) {
605 	msg_warn("uid=%ld: %m", (long) uid);
606 	postdrop_cleanup();
607     }
608 
609     /*
610      * Disable deletion on fatal error before reporting success, so the file
611      * will not be deleted after we have taken responsibility for delivery.
612      */
613     if (postdrop_path) {
614 	junk = postdrop_path;
615 	postdrop_path = 0;
616 	myfree(junk);
617     }
618 
619     /*
620      * Send the completion status to the caller and terminate.
621      */
622     attr_print(VSTREAM_OUT, ATTR_FLAG_NONE,
623 	       SEND_ATTR_INT(MAIL_ATTR_STATUS, status),
624 	       SEND_ATTR_STR(MAIL_ATTR_WHY, status != CLEANUP_STAT_OK
625 			     && VSTRING_LEN(reason) > 0 ?
626 			     vstring_str(reason) : ""),
627 	       ATTR_TYPE_END);
628     vstream_fflush(VSTREAM_OUT);
629     exit(status);
630 }
631