1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 Copyright (c) Todd Lyons <tlyons@exim.org> 2012 - 2014
6 Copyright (c) The Exim Maintainers 2019
9 /* Portions Copyright (c) 2012, 2013, The Trusted Domain Project;
10 All rights reserved, licensed for use per LICENSE.opendmarc. */
12 /* Code for calling dmarc checks via libopendmarc. Called from acl.c. */
16 # if !defined SUPPORT_SPF
17 # error SPF must also be enabled for DMARC
18 # elif defined DISABLE_DKIM
19 # error DKIM must also be enabled for DMARC
22 # include "functions.h"
24 # include "pdkim/pdkim.h"
26 OPENDMARC_LIB_T dmarc_ctx;
27 DMARC_POLICY_T *dmarc_pctx = NULL;
28 OPENDMARC_STATUS_T libdm_status, action, dmarc_policy;
29 OPENDMARC_STATUS_T da, sa, action;
30 BOOL dmarc_abort = FALSE;
31 uschar *dmarc_pass_fail = US"skipped";
32 header_line *from_header = NULL;
33 extern SPF_response_t *spf_response;
34 int dmarc_spf_ares_result = 0;
35 uschar *spf_sender_domain = NULL;
36 uschar *spf_human_readable = NULL;
37 u_char *header_from_sender = NULL;
38 int history_file_status = DMARC_HIST_OK;
39 uschar *dkim_history_buffer= NULL;
41 typedef struct dmarc_exim_p {
46 static dmarc_exim_p dmarc_policy_description[] = {
48 { US"", DMARC_RECORD_P_UNSPECIFIED },
49 { US"none", DMARC_RECORD_P_NONE },
50 { US"quarantine", DMARC_RECORD_P_QUARANTINE },
51 { US"reject", DMARC_RECORD_P_REJECT },
54 /* Accept an error_block struct, initialize if empty, parse to the
55 * end, and append the two strings passed to it. Used for adding
56 * variable amounts of value:pair data to the forensic emails. */
59 add_to_eblock(error_block *eblock, uschar *t1, uschar *t2)
61 error_block *eb = store_malloc(sizeof(error_block));
66 /* Find the end of the eblock struct and point it at eb */
67 error_block *tmp = eblock;
68 while(tmp->next != NULL)
78 /* dmarc_init sets up a context that can be re-used for several
79 messages on the same SMTP connection (that come from the
80 same host with the same HELO string) */
85 int *netmask = NULL; /* Ignored */
88 /* Set some sane defaults. Also clears previous results when
89 * multiple messages in one connection. */
91 dmarc_status = US"none";
93 dmarc_pass_fail = US"skipped";
94 dmarc_used_domain = US"";
95 f.dmarc_has_been_checked = FALSE;
96 header_from_sender = NULL;
97 spf_sender_domain = NULL;
98 spf_human_readable = NULL;
100 /* ACLs have "control=dmarc_disable_verify" */
101 if (f.dmarc_disable_verify == TRUE)
104 (void) memset(&dmarc_ctx, '\0', sizeof dmarc_ctx);
105 dmarc_ctx.nscount = 0;
106 libdm_status = opendmarc_policy_library_init(&dmarc_ctx);
107 if (libdm_status != DMARC_PARSE_OKAY)
109 log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to init library: %s",
110 opendmarc_policy_status_to_str(libdm_status));
113 if (!dmarc_tld_file || !*dmarc_tld_file)
115 DEBUG(D_receive) debug_printf("DMARC: no dmarc_tld_file\n");
118 else if (opendmarc_tld_read_file(CS dmarc_tld_file, NULL, NULL, NULL))
120 log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to load tld list '%s': %s",
121 dmarc_tld_file, strerror(errno));
124 if (!sender_host_address)
126 DEBUG(D_receive) debug_printf("DMARC: no sender_host_address\n");
129 /* This catches locally originated email and startup errors above. */
132 is_ipv6 = string_is_ip_address(sender_host_address, netmask) == 6;
133 if (!(dmarc_pctx = opendmarc_policy_connect_init(sender_host_address, is_ipv6)))
135 log_write(0, LOG_MAIN|LOG_PANIC,
136 "DMARC failure creating policy context: ip=%s", sender_host_address);
145 /* dmarc_store_data stores the header data so that subsequent
146 dmarc_process can access the data */
149 dmarc_store_data(header_line *hdr)
151 /* No debug output because would change every test debug output */
152 if (!f.dmarc_disable_verify)
159 dmarc_send_forensic_report(u_char **ruf)
161 uschar *recipient, *save_sender;
162 BOOL send_status = FALSE;
163 error_block *eblock = NULL;
164 FILE *message_file = NULL;
166 /* Earlier ACL does not have *required* control=dmarc_enable_forensic */
167 if (!f.dmarc_enable_forensic)
170 if ( dmarc_policy == DMARC_POLICY_REJECT && action == DMARC_RESULT_REJECT
171 || dmarc_policy == DMARC_POLICY_QUARANTINE && action == DMARC_RESULT_QUARANTINE
172 || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_REJECT
173 || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_QUARANTINE
177 eblock = add_to_eblock(eblock, US"Sender Domain", dmarc_used_domain);
178 eblock = add_to_eblock(eblock, US"Sender IP Address", sender_host_address);
179 eblock = add_to_eblock(eblock, US"Received Date", tod_stamp(tod_full));
180 eblock = add_to_eblock(eblock, US"SPF Alignment",
181 sa == DMARC_POLICY_SPF_ALIGNMENT_PASS ? US"yes" : US"no");
182 eblock = add_to_eblock(eblock, US"DKIM Alignment",
183 da == DMARC_POLICY_DKIM_ALIGNMENT_PASS ? US"yes" : US"no");
184 eblock = add_to_eblock(eblock, US"DMARC Results", dmarc_status_text);
186 for (int c = 0; ruf[c]; c++)
188 recipient = string_copylc(ruf[c]);
189 if (Ustrncmp(recipient, "mailto:",7))
191 /* Move to first character past the colon */
194 debug_printf("DMARC forensic report to %s%s\n", recipient,
195 (host_checking || f.running_in_test_harness) ? " (not really)" : "");
196 if (host_checking || f.running_in_test_harness)
199 if (!moan_send_message(recipient, ERRMESS_DMARC_FORENSIC, eblock,
200 header_list, message_file, NULL))
201 log_write(0, LOG_MAIN|LOG_PANIC,
202 "failure to send DMARC forensic report to %s", recipient);
208 /* Look up a DNS dmarc record for the given domain. Return it or NULL */
211 dmarc_dns_lookup(uschar * dom)
213 dns_answer * dnsa = store_get_dns_answer();
215 int rc = dns_lookup(dnsa, string_sprintf("_dmarc.%s", dom), T_TXT, NULL);
217 if (rc == DNS_SUCCEED)
218 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
219 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
220 if (rr->type == T_TXT && rr->size > 3)
221 return string_copyn(US rr->data, rr->size);
227 dmarc_write_history_file()
230 u_char **rua; /* aggregate report addressees */
231 uschar *history_buffer = NULL;
233 if (!dmarc_history_file)
235 DEBUG(D_receive) debug_printf("DMARC history file not set\n");
236 return DMARC_HIST_DISABLED;
239 /* Generate the contents of the history file */
240 history_buffer = string_sprintf(
241 "job %s\nreporter %s\nreceived %ld\nipaddr %s\nfrom %s\nmfrom %s\n",
242 message_id, primary_hostname, time(NULL), sender_host_address,
243 header_from_sender, expand_string(US"$sender_address_domain"));
246 history_buffer = string_sprintf("%sspf %d\n", history_buffer, dmarc_spf_ares_result);
247 /* history_buffer = string_sprintf("%sspf -1\n", history_buffer); */
249 history_buffer = string_sprintf(
250 "%s%spdomain %s\npolicy %d\n",
251 history_buffer, dkim_history_buffer, dmarc_used_domain, dmarc_policy);
253 if ((rua = opendmarc_policy_fetch_rua(dmarc_pctx, NULL, 0, 1)))
254 for (tmp_ans = 0; rua[tmp_ans]; tmp_ans++)
255 history_buffer = string_sprintf("%srua %s\n", history_buffer, rua[tmp_ans]);
257 history_buffer = string_sprintf("%srua -\n", history_buffer);
259 opendmarc_policy_fetch_pct(dmarc_pctx, &tmp_ans);
260 history_buffer = string_sprintf("%spct %d\n", history_buffer, tmp_ans);
262 opendmarc_policy_fetch_adkim(dmarc_pctx, &tmp_ans);
263 history_buffer = string_sprintf("%sadkim %d\n", history_buffer, tmp_ans);
265 opendmarc_policy_fetch_aspf(dmarc_pctx, &tmp_ans);
266 history_buffer = string_sprintf("%saspf %d\n", history_buffer, tmp_ans);
268 opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans);
269 history_buffer = string_sprintf("%sp %d\n", history_buffer, tmp_ans);
271 opendmarc_policy_fetch_sp(dmarc_pctx, &tmp_ans);
272 history_buffer = string_sprintf("%ssp %d\n", history_buffer, tmp_ans);
274 history_buffer = string_sprintf(
275 "%salign_dkim %d\nalign_spf %d\naction %d\n",
276 history_buffer, da, sa, action);
278 /* Write the contents to the history file */
280 debug_printf("DMARC logging history data for opendmarc reporting%s\n",
281 (host_checking || f.running_in_test_harness) ? " (not really)" : "");
282 if (host_checking || f.running_in_test_harness)
285 debug_printf("DMARC history data for debugging:\n%s", history_buffer);
290 const int history_file_fd = log_open_as_exim(dmarc_history_file);
292 if (history_file_fd < 0)
294 log_write(0, LOG_MAIN|LOG_PANIC, "failure to create DMARC history file: %s",
296 return DMARC_HIST_FILE_ERR;
299 written_len = write_to_fd_buf(history_file_fd,
301 Ustrlen(history_buffer));
303 (void)close(history_file_fd);
305 if (written_len <= 0)
307 log_write(0, LOG_MAIN|LOG_PANIC, "failure to write to DMARC history file: %s",
309 return DMARC_HIST_WRITE_ERR;
312 return DMARC_HIST_OK;
316 /* dmarc_process adds the envelope sender address to the existing
317 context (if any), retrieves the result, sets up expansion
318 strings and evaluates the condition outcome. */
323 int sr, origin; /* used in SPF section */
324 int dmarc_spf_result = 0; /* stores spf into dmarc conn ctx */
326 pdkim_signature * sig = dkim_signatures;
328 BOOL has_dmarc_record = TRUE;
329 u_char **ruf; /* forensic report addressees, if called for */
331 /* ACLs have "control=dmarc_disable_verify" */
332 if (f.dmarc_disable_verify)
335 /* Store the header From: sender domain for this part of DMARC.
336 * If there is no from_header struct, then it's likely this message
337 * is locally generated and relying on fixups to add it. Just skip
338 * the entire DMARC system if we can't find a From: header....or if
339 * there was a previous error.
343 DEBUG(D_receive) debug_printf("DMARC: no From: header\n");
346 else if (!dmarc_abort)
353 f.parse_allow_group = TRUE;
354 p = parse_find_address_end(from_header->text, FALSE);
355 saveend = *p; *p = '\0';
356 if ((header_from_sender = parse_extract_address(from_header->text, &errormsg,
357 &dummy, &dummy, &domain, FALSE)))
358 header_from_sender += domain;
361 /* The opendmarc library extracts the domain from the email address, but
362 * only try to store it if it's not empty. Otherwise, skip out of DMARC. */
363 if (!header_from_sender || (strcmp( CCS header_from_sender, "") == 0))
365 libdm_status = dmarc_abort
367 : opendmarc_policy_store_from_domain(dmarc_pctx, header_from_sender);
368 if (libdm_status != DMARC_PARSE_OKAY)
370 log_write(0, LOG_MAIN|LOG_PANIC,
371 "failure to store header From: in DMARC: %s, header was '%s'",
372 opendmarc_policy_status_to_str(libdm_status), from_header->text);
377 /* Skip DMARC if connection is SMTP Auth. Temporarily, admin should
378 * instead do this in the ACLs. */
379 if (!dmarc_abort && !sender_host_authenticated)
381 uschar * dmarc_domain;
383 /* Use the envelope sender domain for this part of DMARC */
384 spf_sender_domain = expand_string(US"$sender_address_domain");
387 /* No spf data means null envelope sender so generate a domain name
388 * from the sender_helo_name */
389 if (!spf_sender_domain)
391 spf_sender_domain = sender_helo_name;
392 log_write(0, LOG_MAIN, "DMARC using synthesized SPF sender domain = %s\n",
395 debug_printf("DMARC using synthesized SPF sender domain = %s\n",
398 dmarc_spf_result = DMARC_POLICY_SPF_OUTCOME_NONE;
399 dmarc_spf_ares_result = ARES_RESULT_UNKNOWN;
400 origin = DMARC_POLICY_SPF_ORIGIN_HELO;
401 spf_human_readable = US"";
405 sr = spf_response->result;
406 dmarc_spf_result = sr == SPF_RESULT_NEUTRAL ? DMARC_POLICY_SPF_OUTCOME_NONE :
407 sr == SPF_RESULT_PASS ? DMARC_POLICY_SPF_OUTCOME_PASS :
408 sr == SPF_RESULT_FAIL ? DMARC_POLICY_SPF_OUTCOME_FAIL :
409 sr == SPF_RESULT_SOFTFAIL ? DMARC_POLICY_SPF_OUTCOME_TMPFAIL :
410 DMARC_POLICY_SPF_OUTCOME_NONE;
411 dmarc_spf_ares_result = sr == SPF_RESULT_NEUTRAL ? ARES_RESULT_NEUTRAL :
412 sr == SPF_RESULT_PASS ? ARES_RESULT_PASS :
413 sr == SPF_RESULT_FAIL ? ARES_RESULT_FAIL :
414 sr == SPF_RESULT_SOFTFAIL ? ARES_RESULT_SOFTFAIL :
415 sr == SPF_RESULT_NONE ? ARES_RESULT_NONE :
416 sr == SPF_RESULT_TEMPERROR ? ARES_RESULT_TEMPERROR :
417 sr == SPF_RESULT_PERMERROR ? ARES_RESULT_PERMERROR :
419 origin = DMARC_POLICY_SPF_ORIGIN_MAILFROM;
420 spf_human_readable = US spf_response->header_comment;
422 debug_printf("DMARC using SPF sender domain = %s\n", spf_sender_domain);
424 if (strcmp( CCS spf_sender_domain, "") == 0)
428 libdm_status = opendmarc_policy_store_spf(dmarc_pctx, spf_sender_domain,
429 dmarc_spf_result, origin, spf_human_readable);
430 if (libdm_status != DMARC_PARSE_OKAY)
431 log_write(0, LOG_MAIN|LOG_PANIC, "failure to store spf for DMARC: %s",
432 opendmarc_policy_status_to_str(libdm_status));
435 /* Now we cycle through the dkim signature results and put into
436 * the opendmarc context, further building the DMARC reply. */
437 dkim_history_buffer = US"";
440 int dkim_result, dkim_ares_result, vs, ves;
442 vs = sig->verify_status & ~PDKIM_VERIFY_POLICY;
443 ves = sig->verify_ext_status;
444 dkim_result = vs == PDKIM_VERIFY_PASS ? DMARC_POLICY_DKIM_OUTCOME_PASS :
445 vs == PDKIM_VERIFY_FAIL ? DMARC_POLICY_DKIM_OUTCOME_FAIL :
446 vs == PDKIM_VERIFY_INVALID ? DMARC_POLICY_DKIM_OUTCOME_TMPFAIL :
447 DMARC_POLICY_DKIM_OUTCOME_NONE;
448 libdm_status = opendmarc_policy_store_dkim(dmarc_pctx, US sig->domain,
451 debug_printf("DMARC adding DKIM sender domain = %s\n", sig->domain);
452 if (libdm_status != DMARC_PARSE_OKAY)
453 log_write(0, LOG_MAIN|LOG_PANIC,
454 "failure to store dkim (%s) for DMARC: %s",
455 sig->domain, opendmarc_policy_status_to_str(libdm_status));
458 vs == PDKIM_VERIFY_PASS ? ARES_RESULT_PASS :
459 vs == PDKIM_VERIFY_FAIL ? ARES_RESULT_FAIL :
460 vs == PDKIM_VERIFY_NONE ? ARES_RESULT_NONE :
461 vs == PDKIM_VERIFY_INVALID ?
462 ves == PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE ? ARES_RESULT_PERMERROR :
463 ves == PDKIM_VERIFY_INVALID_BUFFER_SIZE ? ARES_RESULT_PERMERROR :
464 ves == PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD ? ARES_RESULT_PERMERROR :
465 ves == PDKIM_VERIFY_INVALID_PUBKEY_IMPORT ? ARES_RESULT_PERMERROR :
466 ARES_RESULT_UNKNOWN :
468 dkim_history_buffer = string_sprintf("%sdkim %s %d\n", dkim_history_buffer,
469 sig->domain, dkim_ares_result);
473 /* Look up DMARC policy record in DNS. We do this explicitly, rather than
474 letting the dmarc library do it with opendmarc_policy_query_dmarc(), so that
475 our dns access path is used for debug tracing and for the testsuite
478 libdm_status = (rr = dmarc_dns_lookup(header_from_sender))
479 ? opendmarc_policy_store_dmarc(dmarc_pctx, rr, header_from_sender, NULL)
480 : DMARC_DNS_ERROR_NO_RECORD;
481 switch (libdm_status)
483 case DMARC_DNS_ERROR_NXDOMAIN:
484 case DMARC_DNS_ERROR_NO_RECORD:
486 debug_printf("DMARC no record found for %s\n", header_from_sender);
487 has_dmarc_record = FALSE;
489 case DMARC_PARSE_OKAY:
491 debug_printf("DMARC record found for %s\n", header_from_sender);
493 case DMARC_PARSE_ERROR_BAD_VALUE:
495 debug_printf("DMARC record parse error for %s\n", header_from_sender);
496 has_dmarc_record = FALSE;
499 /* everything else, skip dmarc */
501 debug_printf("DMARC skipping (%d), unsure what to do with %s",
502 libdm_status, from_header->text);
503 has_dmarc_record = FALSE;
507 /* Store the policy string in an expandable variable. */
509 libdm_status = opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans);
510 for (c = 0; dmarc_policy_description[c].name; c++)
511 if (tmp_ans == dmarc_policy_description[c].value)
513 dmarc_domain_policy = string_sprintf("%s",dmarc_policy_description[c].name);
517 /* Can't use exim's string manipulation functions so allocate memory
518 for libopendmarc using its max hostname length definition. */
520 dmarc_domain = store_get(DMARC_MAXHOSTNAMELEN, TRUE);
521 libdm_status = opendmarc_policy_fetch_utilized_domain(dmarc_pctx,
522 dmarc_domain, DMARC_MAXHOSTNAMELEN-1);
523 store_release_above(dmarc_domain + Ustrlen(dmarc_domain)+1);
524 dmarc_used_domain = dmarc_domain;
526 if (libdm_status != DMARC_PARSE_OKAY)
527 log_write(0, LOG_MAIN|LOG_PANIC,
528 "failure to read domainname used for DMARC lookup: %s",
529 opendmarc_policy_status_to_str(libdm_status));
531 dmarc_policy = libdm_status = opendmarc_get_policy_to_enforce(dmarc_pctx);
534 case DMARC_POLICY_ABSENT: /* No DMARC record found */
535 dmarc_status = US"norecord";
536 dmarc_pass_fail = US"none";
537 dmarc_status_text = US"No DMARC record";
538 action = DMARC_RESULT_ACCEPT;
540 case DMARC_FROM_DOMAIN_ABSENT: /* No From: domain */
541 dmarc_status = US"nofrom";
542 dmarc_pass_fail = US"temperror";
543 dmarc_status_text = US"No From: domain found";
544 action = DMARC_RESULT_ACCEPT;
546 case DMARC_POLICY_NONE: /* Accept and report */
547 dmarc_status = US"none";
548 dmarc_pass_fail = US"none";
549 dmarc_status_text = US"None, Accept";
550 action = DMARC_RESULT_ACCEPT;
552 case DMARC_POLICY_PASS: /* Explicit accept */
553 dmarc_status = US"accept";
554 dmarc_pass_fail = US"pass";
555 dmarc_status_text = US"Accept";
556 action = DMARC_RESULT_ACCEPT;
558 case DMARC_POLICY_REJECT: /* Explicit reject */
559 dmarc_status = US"reject";
560 dmarc_pass_fail = US"fail";
561 dmarc_status_text = US"Reject";
562 action = DMARC_RESULT_REJECT;
564 case DMARC_POLICY_QUARANTINE: /* Explicit quarantine */
565 dmarc_status = US"quarantine";
566 dmarc_pass_fail = US"fail";
567 dmarc_status_text = US"Quarantine";
568 action = DMARC_RESULT_QUARANTINE;
571 dmarc_status = US"temperror";
572 dmarc_pass_fail = US"temperror";
573 dmarc_status_text = US"Internal Policy Error";
574 action = DMARC_RESULT_TEMPFAIL;
578 libdm_status = opendmarc_policy_fetch_alignment(dmarc_pctx, &da, &sa);
579 if (libdm_status != DMARC_PARSE_OKAY)
580 log_write(0, LOG_MAIN|LOG_PANIC, "failure to read DMARC alignment: %s",
581 opendmarc_policy_status_to_str(libdm_status));
583 if (has_dmarc_record)
585 log_write(0, LOG_MAIN, "DMARC results: spf_domain=%s dmarc_domain=%s "
586 "spf_align=%s dkim_align=%s enforcement='%s'",
587 spf_sender_domain, dmarc_used_domain,
588 sa==DMARC_POLICY_SPF_ALIGNMENT_PASS ?"yes":"no",
589 da==DMARC_POLICY_DKIM_ALIGNMENT_PASS ?"yes":"no",
591 history_file_status = dmarc_write_history_file();
592 /* Now get the forensic reporting addresses, if any */
593 ruf = opendmarc_policy_fetch_ruf(dmarc_pctx, NULL, 0, 1);
594 dmarc_send_forensic_report(ruf);
598 /* shut down libopendmarc */
600 (void) opendmarc_policy_connect_shutdown(dmarc_pctx);
601 if (!f.dmarc_disable_verify)
602 (void) opendmarc_policy_library_shutdown(&dmarc_ctx);
608 dmarc_exim_expand_query(int what)
610 if (f.dmarc_disable_verify || !dmarc_pctx)
611 return dmarc_exim_expand_defaults(what);
613 if (what == DMARC_VERIFY_STATUS)
619 dmarc_exim_expand_defaults(int what)
621 if (what == DMARC_VERIFY_STATUS)
622 return f.dmarc_disable_verify ? US"off" : US"none";
628 authres_dmarc(gstring * g)
630 if (f.dmarc_has_been_checked)
632 g = string_append(g, 2, US";\n\tdmarc=", dmarc_pass_fail);
633 if (header_from_sender)
634 g = string_append(g, 2, US" header.from=", header_from_sender);
639 # endif /* SUPPORT_SPF */
640 #endif /* SUPPORT_DMARC */