1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4 /* Experimental DMARC support.
5 Copyright (c) Todd Lyons <tlyons@exim.org> 2012 - 2014
8 /* Portions Copyright (c) 2012, 2013, The Trusted Domain Project;
9 All rights reserved, licensed for use per LICENSE.opendmarc. */
11 /* Code for calling dmarc checks via libopendmarc. Called from acl.c. */
14 #ifdef EXPERIMENTAL_DMARC
15 # if !defined SUPPORT_SPF
16 # error SPF must also be enabled for DMARC
17 # elif defined DISABLE_DKIM
18 # error DKIM must also be enabled for DMARC
21 # include "functions.h"
23 # include "pdkim/pdkim.h"
25 OPENDMARC_LIB_T dmarc_ctx;
26 DMARC_POLICY_T *dmarc_pctx = NULL;
27 OPENDMARC_STATUS_T libdm_status, action, dmarc_policy;
28 OPENDMARC_STATUS_T da, sa, action;
29 BOOL dmarc_abort = FALSE;
30 uschar *dmarc_pass_fail = US"skipped";
31 header_line *from_header = NULL;
32 extern SPF_response_t *spf_response;
33 int dmarc_spf_ares_result = 0;
34 uschar *spf_sender_domain = NULL;
35 uschar *spf_human_readable = NULL;
36 u_char *header_from_sender = NULL;
37 int history_file_status = DMARC_HIST_OK;
38 uschar *dkim_history_buffer= NULL;
40 typedef struct dmarc_exim_p {
45 static dmarc_exim_p dmarc_policy_description[] = {
47 { US"", DMARC_RECORD_P_UNSPECIFIED },
48 { US"none", DMARC_RECORD_P_NONE },
49 { US"quarantine", DMARC_RECORD_P_QUARANTINE },
50 { US"reject", DMARC_RECORD_P_REJECT },
53 /* Accept an error_block struct, initialize if empty, parse to the
54 * end, and append the two strings passed to it. Used for adding
55 * variable amounts of value:pair data to the forensic emails. */
58 add_to_eblock(error_block *eblock, uschar *t1, uschar *t2)
60 error_block *eb = store_malloc(sizeof(error_block));
65 /* Find the end of the eblock struct and point it at eb */
66 error_block *tmp = eblock;
67 while(tmp->next != NULL)
77 /* dmarc_init sets up a context that can be re-used for several
78 messages on the same SMTP connection (that come from the
79 same host with the same HELO string) */
84 int *netmask = NULL; /* Ignored */
87 /* Set some sane defaults. Also clears previous results when
88 * multiple messages in one connection. */
90 dmarc_status = US"none";
92 dmarc_pass_fail = US"skipped";
93 dmarc_used_domain = US"";
94 f.dmarc_has_been_checked = FALSE;
95 header_from_sender = NULL;
96 spf_sender_domain = NULL;
97 spf_human_readable = NULL;
99 /* ACLs have "control=dmarc_disable_verify" */
100 if (f.dmarc_disable_verify == TRUE)
103 (void) memset(&dmarc_ctx, '\0', sizeof dmarc_ctx);
104 dmarc_ctx.nscount = 0;
105 libdm_status = opendmarc_policy_library_init(&dmarc_ctx);
106 if (libdm_status != DMARC_PARSE_OKAY)
108 log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to init library: %s",
109 opendmarc_policy_status_to_str(libdm_status));
114 DEBUG(D_receive) debug_printf("DMARC: no dmarc_tld_file\n");
117 else if (opendmarc_tld_read_file(CS dmarc_tld_file, NULL, NULL, NULL))
119 log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to load tld list %s: %d",
120 dmarc_tld_file, errno);
123 if (!sender_host_address)
125 DEBUG(D_receive) debug_printf("DMARC: no sender_host_address\n");
128 /* This catches locally originated email and startup errors above. */
131 is_ipv6 = string_is_ip_address(sender_host_address, netmask) == 6;
132 if (!(dmarc_pctx = opendmarc_policy_connect_init(sender_host_address, is_ipv6)))
134 log_write(0, LOG_MAIN|LOG_PANIC,
135 "DMARC failure creating policy context: ip=%s", sender_host_address);
144 /* dmarc_store_data stores the header data so that subsequent
145 dmarc_process can access the data */
148 dmarc_store_data(header_line *hdr)
150 /* No debug output because would change every test debug output */
151 if (!f.dmarc_disable_verify)
158 dmarc_send_forensic_report(u_char **ruf)
160 uschar *recipient, *save_sender;
161 BOOL send_status = FALSE;
162 error_block *eblock = NULL;
163 FILE *message_file = NULL;
165 /* Earlier ACL does not have *required* control=dmarc_enable_forensic */
166 if (!f.dmarc_enable_forensic)
169 if ( dmarc_policy == DMARC_POLICY_REJECT && action == DMARC_RESULT_REJECT
170 || dmarc_policy == DMARC_POLICY_QUARANTINE && action == DMARC_RESULT_QUARANTINE
171 || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_REJECT
172 || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_QUARANTINE
176 eblock = add_to_eblock(eblock, US"Sender Domain", dmarc_used_domain);
177 eblock = add_to_eblock(eblock, US"Sender IP Address", sender_host_address);
178 eblock = add_to_eblock(eblock, US"Received Date", tod_stamp(tod_full));
179 eblock = add_to_eblock(eblock, US"SPF Alignment",
180 sa == DMARC_POLICY_SPF_ALIGNMENT_PASS ? US"yes" : US"no");
181 eblock = add_to_eblock(eblock, US"DKIM Alignment",
182 da == DMARC_POLICY_DKIM_ALIGNMENT_PASS ? US"yes" : US"no");
183 eblock = add_to_eblock(eblock, US"DMARC Results", dmarc_status_text);
185 for (int c = 0; ruf[c]; c++)
187 recipient = string_copylc(ruf[c]);
188 if (Ustrncmp(recipient, "mailto:",7))
190 /* Move to first character past the colon */
193 debug_printf("DMARC forensic report to %s%s\n", recipient,
194 (host_checking || f.running_in_test_harness) ? " (not really)" : "");
195 if (host_checking || f.running_in_test_harness)
198 if (!moan_send_message(recipient, ERRMESS_DMARC_FORENSIC, eblock,
199 header_list, message_file, NULL))
200 log_write(0, LOG_MAIN|LOG_PANIC,
201 "failure to send DMARC forensic report to %s", recipient);
206 /* dmarc_process adds the envelope sender address to the existing
207 context (if any), retrieves the result, sets up expansion
208 strings and evaluates the condition outcome. */
213 int sr, origin; /* used in SPF section */
214 int dmarc_spf_result = 0; /* stores spf into dmarc conn ctx */
216 pdkim_signature * sig = dkim_signatures;
217 BOOL has_dmarc_record = TRUE;
218 u_char **ruf; /* forensic report addressees, if called for */
220 /* ACLs have "control=dmarc_disable_verify" */
221 if (f.dmarc_disable_verify)
224 /* Store the header From: sender domain for this part of DMARC.
225 * If there is no from_header struct, then it's likely this message
226 * is locally generated and relying on fixups to add it. Just skip
227 * the entire DMARC system if we can't find a From: header....or if
228 * there was a previous error.
232 DEBUG(D_receive) debug_printf("DMARC: no From: header\n");
235 else if (!dmarc_abort)
242 f.parse_allow_group = TRUE;
243 p = parse_find_address_end(from_header->text, FALSE);
244 saveend = *p; *p = '\0';
245 if ((header_from_sender = parse_extract_address(from_header->text, &errormsg,
246 &dummy, &dummy, &domain, FALSE)))
247 header_from_sender += domain;
250 /* The opendmarc library extracts the domain from the email address, but
251 * only try to store it if it's not empty. Otherwise, skip out of DMARC. */
252 if (!header_from_sender || (strcmp( CCS header_from_sender, "") == 0))
254 libdm_status = dmarc_abort
256 : opendmarc_policy_store_from_domain(dmarc_pctx, header_from_sender);
257 if (libdm_status != DMARC_PARSE_OKAY)
259 log_write(0, LOG_MAIN|LOG_PANIC,
260 "failure to store header From: in DMARC: %s, header was '%s'",
261 opendmarc_policy_status_to_str(libdm_status), from_header->text);
266 /* Skip DMARC if connection is SMTP Auth. Temporarily, admin should
267 * instead do this in the ACLs. */
268 if (!dmarc_abort && !sender_host_authenticated)
270 uschar * dmarc_domain;
272 /* Use the envelope sender domain for this part of DMARC */
273 spf_sender_domain = expand_string(US"$sender_address_domain");
276 /* No spf data means null envelope sender so generate a domain name
277 * from the sender_helo_name */
278 if (!spf_sender_domain)
280 spf_sender_domain = sender_helo_name;
281 log_write(0, LOG_MAIN, "DMARC using synthesized SPF sender domain = %s\n",
284 debug_printf("DMARC using synthesized SPF sender domain = %s\n",
287 dmarc_spf_result = DMARC_POLICY_SPF_OUTCOME_NONE;
288 dmarc_spf_ares_result = ARES_RESULT_UNKNOWN;
289 origin = DMARC_POLICY_SPF_ORIGIN_HELO;
290 spf_human_readable = US"";
294 sr = spf_response->result;
295 dmarc_spf_result = sr == SPF_RESULT_NEUTRAL ? DMARC_POLICY_SPF_OUTCOME_NONE :
296 sr == SPF_RESULT_PASS ? DMARC_POLICY_SPF_OUTCOME_PASS :
297 sr == SPF_RESULT_FAIL ? DMARC_POLICY_SPF_OUTCOME_FAIL :
298 sr == SPF_RESULT_SOFTFAIL ? DMARC_POLICY_SPF_OUTCOME_TMPFAIL :
299 DMARC_POLICY_SPF_OUTCOME_NONE;
300 dmarc_spf_ares_result = sr == SPF_RESULT_NEUTRAL ? ARES_RESULT_NEUTRAL :
301 sr == SPF_RESULT_PASS ? ARES_RESULT_PASS :
302 sr == SPF_RESULT_FAIL ? ARES_RESULT_FAIL :
303 sr == SPF_RESULT_SOFTFAIL ? ARES_RESULT_SOFTFAIL :
304 sr == SPF_RESULT_NONE ? ARES_RESULT_NONE :
305 sr == SPF_RESULT_TEMPERROR ? ARES_RESULT_TEMPERROR :
306 sr == SPF_RESULT_PERMERROR ? ARES_RESULT_PERMERROR :
308 origin = DMARC_POLICY_SPF_ORIGIN_MAILFROM;
309 spf_human_readable = US spf_response->header_comment;
311 debug_printf("DMARC using SPF sender domain = %s\n", spf_sender_domain);
313 if (strcmp( CCS spf_sender_domain, "") == 0)
317 libdm_status = opendmarc_policy_store_spf(dmarc_pctx, spf_sender_domain,
318 dmarc_spf_result, origin, spf_human_readable);
319 if (libdm_status != DMARC_PARSE_OKAY)
320 log_write(0, LOG_MAIN|LOG_PANIC, "failure to store spf for DMARC: %s",
321 opendmarc_policy_status_to_str(libdm_status));
324 /* Now we cycle through the dkim signature results and put into
325 * the opendmarc context, further building the DMARC reply. */
326 dkim_history_buffer = US"";
329 int dkim_result, dkim_ares_result, vs, ves;
331 vs = sig->verify_status & ~PDKIM_VERIFY_POLICY;
332 ves = sig->verify_ext_status;
333 dkim_result = vs == PDKIM_VERIFY_PASS ? DMARC_POLICY_DKIM_OUTCOME_PASS :
334 vs == PDKIM_VERIFY_FAIL ? DMARC_POLICY_DKIM_OUTCOME_FAIL :
335 vs == PDKIM_VERIFY_INVALID ? DMARC_POLICY_DKIM_OUTCOME_TMPFAIL :
336 DMARC_POLICY_DKIM_OUTCOME_NONE;
337 libdm_status = opendmarc_policy_store_dkim(dmarc_pctx, US sig->domain,
340 debug_printf("DMARC adding DKIM sender domain = %s\n", sig->domain);
341 if (libdm_status != DMARC_PARSE_OKAY)
342 log_write(0, LOG_MAIN|LOG_PANIC,
343 "failure to store dkim (%s) for DMARC: %s",
344 sig->domain, opendmarc_policy_status_to_str(libdm_status));
347 vs == PDKIM_VERIFY_PASS ? ARES_RESULT_PASS :
348 vs == PDKIM_VERIFY_FAIL ? ARES_RESULT_FAIL :
349 vs == PDKIM_VERIFY_NONE ? ARES_RESULT_NONE :
350 vs == PDKIM_VERIFY_INVALID ?
351 ves == PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE ? ARES_RESULT_PERMERROR :
352 ves == PDKIM_VERIFY_INVALID_BUFFER_SIZE ? ARES_RESULT_PERMERROR :
353 ves == PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD ? ARES_RESULT_PERMERROR :
354 ves == PDKIM_VERIFY_INVALID_PUBKEY_IMPORT ? ARES_RESULT_PERMERROR :
355 ARES_RESULT_UNKNOWN :
357 dkim_history_buffer = string_sprintf("%sdkim %s %d\n", dkim_history_buffer,
358 sig->domain, dkim_ares_result);
361 libdm_status = opendmarc_policy_query_dmarc(dmarc_pctx, US"");
362 switch (libdm_status)
364 case DMARC_DNS_ERROR_NXDOMAIN:
365 case DMARC_DNS_ERROR_NO_RECORD:
367 debug_printf("DMARC no record found for %s\n", header_from_sender);
368 has_dmarc_record = FALSE;
370 case DMARC_PARSE_OKAY:
372 debug_printf("DMARC record found for %s\n", header_from_sender);
374 case DMARC_PARSE_ERROR_BAD_VALUE:
376 debug_printf("DMARC record parse error for %s\n", header_from_sender);
377 has_dmarc_record = FALSE;
380 /* everything else, skip dmarc */
382 debug_printf("DMARC skipping (%d), unsure what to do with %s",
383 libdm_status, from_header->text);
384 has_dmarc_record = FALSE;
388 /* Store the policy string in an expandable variable. */
390 libdm_status = opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans);
391 for (c = 0; dmarc_policy_description[c].name; c++)
392 if (tmp_ans == dmarc_policy_description[c].value)
394 dmarc_domain_policy = string_sprintf("%s",dmarc_policy_description[c].name);
398 /* Can't use exim's string manipulation functions so allocate memory
399 for libopendmarc using its max hostname length definition. */
401 dmarc_domain = US calloc(DMARC_MAXHOSTNAMELEN, sizeof(uschar));
402 libdm_status = opendmarc_policy_fetch_utilized_domain(dmarc_pctx,
403 dmarc_domain, DMARC_MAXHOSTNAMELEN-1);
404 dmarc_used_domain = string_copy(dmarc_domain);
407 if (libdm_status != DMARC_PARSE_OKAY)
408 log_write(0, LOG_MAIN|LOG_PANIC,
409 "failure to read domainname used for DMARC lookup: %s",
410 opendmarc_policy_status_to_str(libdm_status));
412 dmarc_policy = libdm_status = opendmarc_get_policy_to_enforce(dmarc_pctx);
415 case DMARC_POLICY_ABSENT: /* No DMARC record found */
416 dmarc_status = US"norecord";
417 dmarc_pass_fail = US"none";
418 dmarc_status_text = US"No DMARC record";
419 action = DMARC_RESULT_ACCEPT;
421 case DMARC_FROM_DOMAIN_ABSENT: /* No From: domain */
422 dmarc_status = US"nofrom";
423 dmarc_pass_fail = US"temperror";
424 dmarc_status_text = US"No From: domain found";
425 action = DMARC_RESULT_ACCEPT;
427 case DMARC_POLICY_NONE: /* Accept and report */
428 dmarc_status = US"none";
429 dmarc_pass_fail = US"none";
430 dmarc_status_text = US"None, Accept";
431 action = DMARC_RESULT_ACCEPT;
433 case DMARC_POLICY_PASS: /* Explicit accept */
434 dmarc_status = US"accept";
435 dmarc_pass_fail = US"pass";
436 dmarc_status_text = US"Accept";
437 action = DMARC_RESULT_ACCEPT;
439 case DMARC_POLICY_REJECT: /* Explicit reject */
440 dmarc_status = US"reject";
441 dmarc_pass_fail = US"fail";
442 dmarc_status_text = US"Reject";
443 action = DMARC_RESULT_REJECT;
445 case DMARC_POLICY_QUARANTINE: /* Explicit quarantine */
446 dmarc_status = US"quarantine";
447 dmarc_pass_fail = US"fail";
448 dmarc_status_text = US"Quarantine";
449 action = DMARC_RESULT_QUARANTINE;
452 dmarc_status = US"temperror";
453 dmarc_pass_fail = US"temperror";
454 dmarc_status_text = US"Internal Policy Error";
455 action = DMARC_RESULT_TEMPFAIL;
459 libdm_status = opendmarc_policy_fetch_alignment(dmarc_pctx, &da, &sa);
460 if (libdm_status != DMARC_PARSE_OKAY)
461 log_write(0, LOG_MAIN|LOG_PANIC, "failure to read DMARC alignment: %s",
462 opendmarc_policy_status_to_str(libdm_status));
464 if (has_dmarc_record)
466 log_write(0, LOG_MAIN, "DMARC results: spf_domain=%s dmarc_domain=%s "
467 "spf_align=%s dkim_align=%s enforcement='%s'",
468 spf_sender_domain, dmarc_used_domain,
469 sa==DMARC_POLICY_SPF_ALIGNMENT_PASS ?"yes":"no",
470 da==DMARC_POLICY_DKIM_ALIGNMENT_PASS ?"yes":"no",
472 history_file_status = dmarc_write_history_file();
473 /* Now get the forensic reporting addresses, if any */
474 ruf = opendmarc_policy_fetch_ruf(dmarc_pctx, NULL, 0, 1);
475 dmarc_send_forensic_report(ruf);
479 /* shut down libopendmarc */
481 (void) opendmarc_policy_connect_shutdown(dmarc_pctx);
482 if (!f.dmarc_disable_verify)
483 (void) opendmarc_policy_library_shutdown(&dmarc_ctx);
489 dmarc_write_history_file()
494 u_char **rua; /* aggregate report addressees */
495 uschar *history_buffer = NULL;
497 if (!dmarc_history_file)
499 DEBUG(D_receive) debug_printf("DMARC history file not set\n");
500 return DMARC_HIST_DISABLED;
502 history_file_fd = log_create(dmarc_history_file);
504 if (history_file_fd < 0)
506 log_write(0, LOG_MAIN|LOG_PANIC, "failure to create DMARC history file: %s",
508 return DMARC_HIST_FILE_ERR;
511 /* Generate the contents of the history file */
512 history_buffer = string_sprintf(
513 "job %s\nreporter %s\nreceived %ld\nipaddr %s\nfrom %s\nmfrom %s\n",
514 message_id, primary_hostname, time(NULL), sender_host_address,
515 header_from_sender, expand_string(US"$sender_address_domain"));
518 history_buffer = string_sprintf("%sspf %d\n", history_buffer, dmarc_spf_ares_result);
519 /* history_buffer = string_sprintf("%sspf -1\n", history_buffer); */
521 history_buffer = string_sprintf(
522 "%s%spdomain %s\npolicy %d\n",
523 history_buffer, dkim_history_buffer, dmarc_used_domain, dmarc_policy);
525 if ((rua = opendmarc_policy_fetch_rua(dmarc_pctx, NULL, 0, 1)))
526 for (tmp_ans = 0; rua[tmp_ans]; tmp_ans++)
527 history_buffer = string_sprintf("%srua %s\n", history_buffer, rua[tmp_ans]);
529 history_buffer = string_sprintf("%srua -\n", history_buffer);
531 opendmarc_policy_fetch_pct(dmarc_pctx, &tmp_ans);
532 history_buffer = string_sprintf("%spct %d\n", history_buffer, tmp_ans);
534 opendmarc_policy_fetch_adkim(dmarc_pctx, &tmp_ans);
535 history_buffer = string_sprintf("%sadkim %d\n", history_buffer, tmp_ans);
537 opendmarc_policy_fetch_aspf(dmarc_pctx, &tmp_ans);
538 history_buffer = string_sprintf("%saspf %d\n", history_buffer, tmp_ans);
540 opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans);
541 history_buffer = string_sprintf("%sp %d\n", history_buffer, tmp_ans);
543 opendmarc_policy_fetch_sp(dmarc_pctx, &tmp_ans);
544 history_buffer = string_sprintf("%ssp %d\n", history_buffer, tmp_ans);
546 history_buffer = string_sprintf(
547 "%salign_dkim %d\nalign_spf %d\naction %d\n",
548 history_buffer, da, sa, action);
550 /* Write the contents to the history file */
552 debug_printf("DMARC logging history data for opendmarc reporting%s\n",
553 (host_checking || f.running_in_test_harness) ? " (not really)" : "");
554 if (host_checking || f.running_in_test_harness)
557 debug_printf("DMARC history data for debugging:\n%s", history_buffer);
561 written_len = write_to_fd_buf(history_file_fd,
563 Ustrlen(history_buffer));
564 if (written_len == 0)
566 log_write(0, LOG_MAIN|LOG_PANIC, "failure to write to DMARC history file: %s",
568 return DMARC_HIST_WRITE_ERR;
570 (void)close(history_file_fd);
572 return DMARC_HIST_OK;
577 dmarc_exim_expand_query(int what)
579 if (f.dmarc_disable_verify || !dmarc_pctx)
580 return dmarc_exim_expand_defaults(what);
582 if (what == DMARC_VERIFY_STATUS)
588 dmarc_exim_expand_defaults(int what)
590 if (what == DMARC_VERIFY_STATUS)
591 return f.dmarc_disable_verify ? US"off" : US"none";
597 authres_dmarc(gstring * g)
599 if (f.dmarc_has_been_checked)
601 g = string_append(g, 2, US";\n\tdmarc=", dmarc_pass_fail);
602 if (header_from_sender)
603 g = string_append(g, 2, US" header.from=", header_from_sender);
608 # endif /* SUPPORT_SPF */
609 #endif /* EXPERIMENTAL_DMARC */