Filter out zero-length MX records
[citadel] / citadel / modules / smtp / serv_smtpclient.c
1 /*
2  * Transmit outbound SMTP mail to the big wide world of the Internet
3  *
4  * This is the new, exciting, clever version that makes libcurl do all the work  :)
5  *
6  * Copyright (c) 1997-2021 by the citadel.org team
7  *
8  * This program is open source software; you can redistribute it and/or
9  * modify it under the terms of the GNU General Public License as published
10  * by the Free Software Foundation; either version 3 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  */
18
19 #include <stdlib.h>
20 #include <unistd.h>
21 #include <stdio.h>
22 #include <sysconfig.h>
23 #include <time.h>
24 #include <ctype.h>
25 #include <string.h>
26 #include <errno.h>
27 #include <sys/types.h>
28 #include <sys/stat.h>
29 #include <libcitadel.h>
30 #include <curl/curl.h>
31 #include "citadel.h"
32 #include "server.h"
33 #include "citserver.h"
34 #include "support.h"
35 #include "config.h"
36 #include "ctdl_module.h"
37 #include "clientsocket.h"
38 #include "msgbase.h"
39 #include "domain.h"
40 #include "internet_addressing.h"
41 #include "citadel_dirs.h"
42 #include "modules/smtp/smtp_util.h"
43
44 struct smtpmsgsrc {             // Data passed in and out of libcurl for message upload
45         StrBuf *TheMessage;
46         int bytes_total;
47         int bytes_sent;
48 };
49
50 static int doing_smtpclient = 0;
51 long *smtpq = NULL;             // array of msgnums containing queue instructions
52 int smtpq_count = 0;            // number of queue messages in smtpq
53 int smtpq_alloc = 0;            // current allocation size for smtpq
54
55
56 /*
57  * Initialize the SMTP outbound queue
58  */
59 void smtp_init_spoolout(void) {
60         struct ctdlroom qrbuf;
61
62         /*
63          * Create the room.  This will silently fail if the room already
64          * exists, and that's perfectly ok, because we want it to exist.
65          */
66         CtdlCreateRoom(SMTP_SPOOLOUT_ROOM, 3, "", 0, 1, 0, VIEW_QUEUE);
67
68         /*
69          * Make sure it's set to be a "system room" so it doesn't show up
70          * in the <K>nown rooms list for administrators.
71          */
72         if (CtdlGetRoomLock(&qrbuf, SMTP_SPOOLOUT_ROOM) == 0) {
73                 qrbuf.QRflags2 |= QR2_SYSTEM;
74                 CtdlPutRoomLock(&qrbuf);
75         }
76 }
77
78
79 /* For internet mail, generate delivery instructions.
80  * Yes, this is recursive.  Deal with it.  Infinite recursion does
81  * not happen because the delivery instructions message does not
82  * contain a recipient.
83  */
84 int smtp_aftersave(struct CtdlMessage *msg, struct recptypes *recps) {
85         if ((recps != NULL) && (recps->num_internet > 0)) {
86                 struct CtdlMessage *imsg = NULL;
87                 char recipient[SIZ];
88                 StrBuf *SpoolMsg = NewStrBuf();
89                 long nTokens;
90                 int i;
91
92                 syslog(LOG_DEBUG, "smtpclient: generating delivery instructions");
93
94                 StrBufPrintf(SpoolMsg,
95                              "Content-type: " SPOOLMIME "\n"
96                              "\n"
97                              "msgid|%s\n"
98                              "submitted|%ld\n" "bounceto|%s\n", msg->cm_fields[eVltMsgNum], (long) time(NULL), recps->bounce_to);
99
100                 if (recps->envelope_from != NULL) {
101                         StrBufAppendBufPlain(SpoolMsg, HKEY("envelope_from|"), 0);
102                         StrBufAppendBufPlain(SpoolMsg, recps->envelope_from, -1, 0);
103                         StrBufAppendBufPlain(SpoolMsg, HKEY("\n"), 0);
104                 }
105                 if (recps->sending_room != NULL) {
106                         StrBufAppendBufPlain(SpoolMsg, HKEY("source_room|"), 0);
107                         StrBufAppendBufPlain(SpoolMsg, recps->sending_room, -1, 0);
108                         StrBufAppendBufPlain(SpoolMsg, HKEY("\n"), 0);
109                 }
110
111                 nTokens = num_tokens(recps->recp_internet, '|');
112                 for (i = 0; i < nTokens; i++) {
113                         long len;
114                         len = extract_token(recipient, recps->recp_internet, i, '|', sizeof recipient);
115                         if (len > 0) {
116                                 StrBufAppendBufPlain(SpoolMsg, HKEY("remote|"), 0);
117                                 StrBufAppendBufPlain(SpoolMsg, recipient, len, 0);
118                                 StrBufAppendBufPlain(SpoolMsg, HKEY("|0||\n"), 0);
119                         }
120                 }
121
122                 imsg = malloc(sizeof(struct CtdlMessage));
123                 memset(imsg, 0, sizeof(struct CtdlMessage));
124                 imsg->cm_magic = CTDLMESSAGE_MAGIC;
125                 imsg->cm_anon_type = MES_NORMAL;
126                 imsg->cm_format_type = FMT_RFC822;
127                 CM_SetField(imsg, eMsgSubject, HKEY("QMSG"));
128                 CM_SetField(imsg, eAuthor, HKEY("Citadel"));
129                 CM_SetField(imsg, eJournal, HKEY("do not journal"));
130                 CM_SetAsFieldSB(imsg, eMesageText, &SpoolMsg);
131                 CtdlSubmitMsg(imsg, NULL, SMTP_SPOOLOUT_ROOM);
132                 CM_Free(imsg);
133         }
134         return 0;
135 }
136
137
138 /*
139  * Callback for smtp_attempt_delivery() to supply libcurl with upload data.
140  */
141 static size_t upload_source(void *ptr, size_t size, size_t nmemb, void *userp) {
142         struct smtpmsgsrc *s = (struct smtpmsgsrc *) userp;
143         int sendbytes = 0;
144         const char *send_this = NULL;
145
146         sendbytes = (size * nmemb);
147
148         if (s->bytes_sent >= s->bytes_total) {
149                 return (0);     // no data remaining; we are done
150         }
151
152         if (sendbytes > (s->bytes_total - s->bytes_sent)) {
153                 sendbytes = s->bytes_total - s->bytes_sent;     // can't send more than we have
154         }
155
156         send_this = ChrPtr(s->TheMessage);
157         send_this += s->bytes_sent;     // start where we last left off
158
159         memcpy(ptr, send_this, sendbytes);
160         s->bytes_sent += sendbytes;
161         return (sendbytes);     // return the number of bytes _actually_ copied
162 }
163
164
165 /*
166  * The libcurl API doesn't provide a way to capture the actual SMTP result message returned
167  * by the remote server.  This is an ugly way to extract it, by capturing debug data from
168  * the library and filtering on the lines we want.
169  */
170 int ctdl_libcurl_smtp_debug_callback(CURL *handle, curl_infotype type, char *data, size_t size, void *userptr) {
171         if (type != CURLINFO_HEADER_IN)
172                 return 0;
173         if (!userptr)
174                 return 0;
175         char *debugbuf = (char *) userptr;
176
177         int len = strlen(debugbuf);
178         if (len + size > SIZ)
179                 return 0;
180
181         memcpy(&debugbuf[len], data, size);
182         debugbuf[len + size] = 0;
183         return 0;
184 }
185
186
187 /*
188  * Go through the debug output of an SMTP transaction, and boil it down to just the final success or error response message.
189  */
190 void trim_response(long response_code, char *response) {
191         if ((response_code < 100) || (response_code > 999) || (IsEmptyStr(response))) {
192                 return;
193         }
194
195         char *t = malloc(strlen(response));
196         if (!t) {
197                 return;
198         }
199         t[0] = 0;
200
201         char *p;
202         for (p = response; *p != 0; ++p) {
203                 if ( (*p != '\n') && (!isprint(*p)) ) {         // expunge any nonprintables except for newlines
204                         *p = ' ';
205                 }
206         }
207
208         char response_code_str[4];
209         snprintf(response_code_str, sizeof response_code_str, "%ld", response_code);
210         char *respstart = strstr(response, response_code_str);
211         if (respstart == NULL) {                                // If we have a response code but no response text,
212                 strcpy(response, smtpstatus(response_code));    // use one of our canned messages.
213                 return;
214         }
215         strcpy(response, respstart);
216
217         p = strstr(response, "\n");
218         if (p != NULL) {
219                 *p = 0;
220         }
221 }
222
223
224 /*
225  * Attempt a delivery to one recipient.
226  * Returns a three-digit SMTP status code.
227  */
228 int smtp_attempt_delivery(long msgid, char *recp, char *envelope_from, char *response) {
229         struct smtpmsgsrc s;
230         char *fromaddr = NULL;
231         CURL *curl;
232         CURLcode res = CURLE_OK;
233         struct curl_slist *recipients = NULL;
234         long response_code = 421;
235         int num_mx = 0;
236         char mxes[SIZ];
237         char user[1024];
238         char node[1024];
239         char name[1024];
240         char try_this_mx[256];
241         char smtp_url[512];
242         int i;
243
244         syslog(LOG_DEBUG, "smtpclient: smtp_attempt_delivery(%ld, %s)", msgid, recp);
245
246         process_rfc822_addr(recp, user, node, name);    // split recipient address into username, hostname, displayname
247         num_mx = getmx(mxes, node);
248         if (num_mx < 1) {
249                 return (421);
250         }
251
252         CC->redirect_buffer = NewStrBufPlain(NULL, SIZ);
253         CtdlOutputMsg(msgid, MT_RFC822, HEADERS_ALL, 0, 1, NULL, 0, NULL, &fromaddr, NULL);
254         s.TheMessage = CC->redirect_buffer;
255         s.bytes_total = StrLength(CC->redirect_buffer);
256         s.bytes_sent = 0;
257         CC->redirect_buffer = NULL;
258         response_code = 421;
259
260         for (i = 0; ((i < num_mx) && ((response_code / 100) == 4)); ++i) {      // keep trying MXes until one works or we run out
261                 response_code = 421;    // default 421 makes non-protocol errors transient
262                 s.bytes_sent = 0;       // rewind our buffer in case we try multiple MXes
263
264                 curl = curl_easy_init();
265                 if (curl) {
266                         response[0] = 0;
267
268                         if (!IsEmptyStr(envelope_from)) {
269                                 curl_easy_setopt(curl, CURLOPT_MAIL_FROM, envelope_from);
270                         } else {
271                                 curl_easy_setopt(curl, CURLOPT_MAIL_FROM, fromaddr);
272                         }
273
274                         recipients = curl_slist_append(recipients, recp);
275                         curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
276                         curl_easy_setopt(curl, CURLOPT_READFUNCTION, upload_source);
277                         curl_easy_setopt(curl, CURLOPT_READDATA, &s);
278                         curl_easy_setopt(curl, CURLOPT_UPLOAD, 1);      // tell libcurl we are uploading
279                         curl_easy_setopt(curl, CURLOPT_TIMEOUT, 20L);   // Time out after 20 seconds
280                         if (CtdlGetConfigInt("c_smtpclient_disable_starttls") == 0) {
281                                 curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_TRY);        // Attempt STARTTLS if offered
282                         }
283                         curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
284                         curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
285                         curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, ctdl_libcurl_smtp_debug_callback);
286                         curl_easy_setopt(curl, CURLOPT_DEBUGDATA, (void *) response);
287                         curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
288
289                         // Construct an SMTP URL in the form of:
290                         //      smtp[s]://target_host/source_host
291                         // This looks weird but libcurl uses that last part to set our name for EHLO or HELO.
292                         // We check for "smtp://" and "smtps://" because the admin may have put those prefixes in a smart-host entry.
293                         // If there is no prefix we add "smtp://"
294                         extract_token(try_this_mx, mxes, i, '|', (sizeof try_this_mx - 7));
295                         snprintf(smtp_url, sizeof smtp_url, "%s%s/%s", (((!strncasecmp(try_this_mx, HKEY("smtp://")))
296                                                                          ||
297                                                                          (!strncasecmp
298                                                                           (try_this_mx,
299                                                                            HKEY("smtps://")))) ? "" : "smtp://"),
300                                  try_this_mx, CtdlGetConfigStr("c_fqdn")
301                             );
302                         curl_easy_setopt(curl, CURLOPT_URL, smtp_url);
303                         syslog(LOG_DEBUG, "smtpclient: trying MX %d of %d <%s>", i+1, num_mx, smtp_url);        // send the message
304                         res = curl_easy_perform(curl);
305                         curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response_code);
306                         syslog(LOG_DEBUG,
307                                "smtpclient: libcurl returned %d (%s) , SMTP response %ld",
308                                res, curl_easy_strerror(res), response_code);
309
310                         if ((res != CURLE_OK) && (response_code == 0)) {        // check for errors
311                                 response_code = 421;
312                         }
313
314                         curl_slist_free_all(recipients);
315                         recipients = NULL;      // this gets reused; avoid double-free
316                         curl_easy_cleanup(curl);
317                         curl = NULL;    // this gets reused; avoid double-free
318
319                         /* Trim the error message buffer down to just the actual message */
320                         trim_response(response_code, response);
321                 }
322         }
323
324         FreeStrBuf(&s.TheMessage);
325         if (fromaddr)
326                 free(fromaddr);
327         return ((int) response_code);
328 }
329
330
331 /*
332  * Process one outbound message.
333  */
334 void smtp_process_one_msg(long qmsgnum) {
335         struct CtdlMessage *msg = NULL;
336         char *instr = NULL;
337         int i;
338         int num_success = 0;
339         int num_fail = 0;
340         int num_delayed = 0;
341         long deletes[2];
342         int delete_this_queue = 0;
343         char server_response[SIZ];
344
345         msg = CtdlFetchMessage(qmsgnum, 1);
346         if (msg == NULL) {
347                 syslog(LOG_WARNING, "smtpclient: %ld does not exist", qmsgnum);
348                 return;
349         }
350
351         instr = msg->cm_fields[eMesageText];
352         msg->cm_fields[eMesageText] = NULL;
353         CM_Free(msg);
354
355         // if the queue message has any CRLF's convert them to LF's
356         char *crlf = NULL;
357         while (crlf = strstr(instr, "\r\n"), crlf != NULL) {
358                 strcpy(crlf, crlf + 1);
359         }
360
361         // Strip out the headers and we are now left with just the instructions.
362         char *soi = strstr(instr, "\n\n");
363         if (soi) {
364                 strcpy(instr, soi + 2);
365         }
366
367         long msgid = 0;
368         time_t submitted = time(NULL);
369         time_t attempted = 0;
370         char *bounceto = NULL;
371         char *envelope_from = NULL;
372
373         char cfgline[SIZ];
374         for (i = 0; i < num_tokens(instr, '\n'); ++i) {
375                 extract_token(cfgline, instr, i, '\n', sizeof cfgline);
376                 if (!strncasecmp(cfgline, HKEY("msgid|")))
377                         msgid = atol(&cfgline[6]);
378                 if (!strncasecmp(cfgline, HKEY("submitted|")))
379                         submitted = atol(&cfgline[10]);
380                 if (!strncasecmp(cfgline, HKEY("attempted|")))
381                         attempted = atol(&cfgline[10]);
382                 if (!strncasecmp(cfgline, HKEY("bounceto|")))
383                         bounceto = strdup(&cfgline[9]);
384                 if (!strncasecmp(cfgline, HKEY("envelope_from|")))
385                         envelope_from = strdup(&cfgline[14]);
386         }
387
388         int should_try_now = 0;
389         if (attempted < submitted) {    // If no attempts have been made yet, try now
390                 should_try_now = 1;
391         } else if ((attempted - submitted) <= 14400) {
392                 if ((time(NULL) - attempted) > 1800) {  // First four hours, retry every 30 minutes
393                         should_try_now = 1;
394                 }
395         } else {
396                 if ((time(NULL) - attempted) > 14400) { // After that, retry once every 4 hours
397                         should_try_now = 1;
398                 }
399         }
400
401         if (should_try_now) {
402                 syslog(LOG_DEBUG, "smtpclient: %ld attempting delivery now", qmsgnum);
403                 StrBuf *NewInstr = NewStrBuf();
404                 StrBufAppendPrintf(NewInstr, "Content-type: " SPOOLMIME "\n\n");
405                 StrBufAppendPrintf(NewInstr, "msgid|%ld\n", msgid);
406                 StrBufAppendPrintf(NewInstr, "submitted|%ld\n", submitted);
407                 if (bounceto)
408                         StrBufAppendPrintf(NewInstr, "bounceto|%s\n", bounceto);
409                 if (envelope_from)
410                         StrBufAppendPrintf(NewInstr, "envelope_from|%s\n", envelope_from);
411
412                 for (i = 0; i < num_tokens(instr, '\n'); ++i) {
413                         extract_token(cfgline, instr, i, '\n', sizeof cfgline);
414                         if (!strncasecmp(cfgline, HKEY("remote|"))) {
415                                 char recp[SIZ];
416                                 int previous_result = extract_int(cfgline, 2);
417                                 if ((previous_result == 0)
418                                     || (previous_result == 4)) {
419                                         int new_result = 421;
420                                         extract_token(recp, cfgline, 1, '|', sizeof recp);
421                                         new_result = smtp_attempt_delivery(msgid, recp, envelope_from, server_response);
422                                         syslog(LOG_DEBUG,
423                                                "smtpclient: recp: <%s> , result: %d (%s)", recp, new_result, server_response);
424                                         if ((new_result / 100) == 2) {
425                                                 ++num_success;
426                                         } else {
427                                                 if ((new_result / 100) == 5) {
428                                                         ++num_fail;
429                                                 } else {
430                                                         ++num_delayed;
431                                                 }
432                                                 StrBufAppendPrintf
433                                                     (NewInstr,
434                                                      "remote|%s|%ld|%ld (%s)\n",
435                                                      recp, (new_result / 100), new_result, server_response);
436                                         }
437                                 }
438                         }
439                 }
440
441                 StrBufAppendPrintf(NewInstr, "attempted|%ld\n", time(NULL));
442
443                 // All deliveries have now been attempted.  Now determine the disposition of this queue entry.
444
445                 time_t age = time(NULL) - submitted;
446                 syslog(LOG_DEBUG,
447                        "smtpclient: submission age: %ldd%ldh%ldm%lds",
448                        (age / 86400), ((age % 86400) / 3600), ((age % 3600) / 60), (age % 60));
449                 syslog(LOG_DEBUG, "smtpclient: num_success=%d , num_fail=%d , num_delayed=%d", num_success, num_fail, num_delayed);
450
451                 // If there are permanent fails on this attempt, deliver a bounce to the user.
452                 // The 5XX fails will be recorded in the rewritten queue, but they will be removed before the next attempt.
453                 if (num_fail > 0) {
454                         smtp_do_bounce(ChrPtr(NewInstr), SDB_BOUNCE_FATALS);
455                 }
456                 // If all deliveries have either succeeded or failed, we are finished with this queue entry.
457                 //
458                 if (num_delayed == 0) {
459                         delete_this_queue = 1;
460                 }
461                 // If it's been more than five days, give up and tell the sender that delivery failed
462                 //
463                 else if ((time(NULL) - submitted) > SMTP_DELIVER_FAIL) {
464                         smtp_do_bounce(ChrPtr(NewInstr), SDB_BOUNCE_ALL);
465                         delete_this_queue = 1;
466                 }
467                 // If it's been more than four hours but less than five days, warn the sender that delivery is delayed
468                 //
469                 else if (((attempted - submitted) < SMTP_DELIVER_WARN)
470                          && ((time(NULL) - submitted) >= SMTP_DELIVER_WARN)) {
471                         smtp_do_bounce(ChrPtr(NewInstr), SDB_WARN);
472                 }
473
474                 if (delete_this_queue) {
475                         syslog(LOG_DEBUG, "smtpclient: %ld deleting", qmsgnum);
476                         deletes[0] = qmsgnum;
477                         deletes[1] = msgid;
478                         CtdlDeleteMessages(SMTP_SPOOLOUT_ROOM, deletes, 2, "");
479                         FreeStrBuf(&NewInstr);  // We have to free NewInstr here, no longer needed
480                 } else {
481                         // replace the old queue entry with the new one
482                         syslog(LOG_DEBUG, "smtpclient: %ld rewriting", qmsgnum);
483                         msg = convert_internet_message_buf(&NewInstr);  // This function will free NewInstr for us
484                         CtdlSubmitMsg(msg, NULL, SMTP_SPOOLOUT_ROOM);
485                         CM_Free(msg);
486                         CtdlDeleteMessages(SMTP_SPOOLOUT_ROOM, &qmsgnum, 1, "");
487                 }
488         } else {
489                 syslog(LOG_DEBUG, "smtpclient: %ld retry time not reached", qmsgnum);
490         }
491
492         if (bounceto != NULL)
493                 free(bounceto);
494         if (envelope_from != NULL)
495                 free(envelope_from);
496         free(instr);
497 }
498
499
500 /*
501  * Callback for smtp_do_queue()
502  */
503 void smtp_add_msg(long msgnum, void *userdata) {
504
505         if (smtpq == NULL) {
506                 smtpq_count = 0;
507                 smtpq_alloc = 100;
508                 smtpq = malloc(smtpq_alloc * sizeof(long));
509         }
510
511         if (smtpq_alloc >= smtpq_count) {
512                 smtpq_alloc += 100;
513                 smtpq = realloc(smtpq, (smtpq_alloc * sizeof(long)));
514         }
515
516         smtpq[smtpq_count++] = msgnum;
517 }
518
519
520 /*
521  * Run through the queue sending out messages.
522  */
523 void smtp_do_queue(void) {
524         int i = 0;
525
526         /*
527          * This is a simple concurrency check to make sure only one smtpclient
528          * run is done at a time.  We could do this with a mutex, but since we
529          * don't really require extremely fine granularity here, we'll do it
530          * with a static variable instead.
531          */
532         if (doing_smtpclient)
533                 return;
534         doing_smtpclient = 1;
535
536         syslog(LOG_DEBUG, "smtpclient: start queue run");
537
538         if (CtdlGetRoom(&CC->room, SMTP_SPOOLOUT_ROOM) != 0) {
539                 syslog(LOG_WARNING, "Cannot find room <%s>", SMTP_SPOOLOUT_ROOM);
540                 doing_smtpclient = 0;
541                 return;
542         }
543         // Put the queue in memory so we can close the db cursor
544         CtdlForEachMessage(MSGS_ALL, 0L, NULL, SPOOLMIME, NULL, smtp_add_msg, NULL);
545
546         // We are ready to run through the queue now.
547         for (i = 0; i < smtpq_count; ++i) {
548                 smtp_process_one_msg(smtpq[i]);
549         }
550
551         smtpq_count = 0;        // don't free it, we will use this memory on the next run
552         doing_smtpclient = 0;
553         syslog(LOG_DEBUG, "smtpclient: end queue run");
554 }
555
556
557 /*
558  * Module entry point
559  */
560 CTDL_MODULE_INIT(smtpclient)
561 {
562         if (!threading) {
563                 CtdlRegisterMessageHook(smtp_aftersave, EVT_AFTERSAVE);
564                 CtdlRegisterSessionHook(smtp_do_queue, EVT_TIMER, PRIO_AGGR + 50);
565                 smtp_init_spoolout();
566         }
567
568         /* return our module id for the log */
569         return "smtpclient";
570 }