/************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Experimental DMARC support. Copyright (c) Todd Lyons 2012, 2013 License: GPL */ /* Portions Copyright (c) 2012, 2013, The Trusted Domain Project; All rights reserved, licensed for use per LICENSE.opendmarc. */ /* Code for calling dmarc checks via libopendmarc. Called from acl.c. */ #include "exim.h" #ifdef EXPERIMENTAL_DMARC #if !defined EXPERIMENTAL_SPF #error SPF must also be enabled for DMARC #elif defined DISABLE_DKIM #error DKIM must also be enabled for DMARC #else #include "functions.h" #include "dmarc.h" #include "pdkim/pdkim.h" OPENDMARC_LIB_T dmarc_ctx; DMARC_POLICY_T *dmarc_pctx = NULL; OPENDMARC_STATUS_T libdm_status, action, dmarc_policy; OPENDMARC_STATUS_T da, sa, action; BOOL dmarc_abort = FALSE; uschar *dmarc_pass_fail = US"skipped"; extern pdkim_signature *dkim_signatures; header_line *from_header = NULL; extern SPF_response_t *spf_response; int dmarc_spf_ares_result = 0; uschar *spf_sender_domain = NULL; uschar *spf_human_readable = NULL; u_char *header_from_sender = NULL; int history_file_status = DMARC_HIST_OK; uschar *dkim_history_buffer= NULL; /* Accept an error_block struct, initialize if empty, parse to the * end, and append the two strings passed to it. Used for adding * variable amounts of value:pair data to the forensic emails. */ static error_block * add_to_eblock(error_block *eblock, uschar *t1, uschar *t2) { error_block *eb = malloc(sizeof(error_block)); if (eblock == NULL) eblock = eb; else { /* Find the end of the eblock struct and point it at eb */ error_block *tmp = eblock; while(tmp->next != NULL) tmp = tmp->next; tmp->next = eb; } eb->text1 = t1; eb->text2 = t2; eb->next = NULL; return eblock; } /* dmarc_init sets up a context that can be re-used for several messages on the same SMTP connection (that come from the same host with the same HELO string) */ int dmarc_init() { int *netmask = NULL; /* Ignored */ int is_ipv6 = 0; char *tld_file = (dmarc_tld_file == NULL) ? "/etc/exim/opendmarc.tlds" : (char *)dmarc_tld_file; /* Set some sane defaults. Also clears previous results when * multiple messages in one connection. */ dmarc_pctx = NULL; dmarc_status = US"none"; dmarc_abort = FALSE; dmarc_pass_fail = US"skipped"; dmarc_used_domain = US""; dmarc_ar_header = NULL; dmarc_has_been_checked = FALSE; header_from_sender = NULL; spf_sender_domain = NULL; spf_human_readable = NULL; /* ACLs have "control=dmarc_disable_verify" */ if (dmarc_disable_verify == TRUE) return OK; (void) memset(&dmarc_ctx, '\0', sizeof dmarc_ctx); dmarc_ctx.nscount = 0; libdm_status = opendmarc_policy_library_init(&dmarc_ctx); if (libdm_status != DMARC_PARSE_OKAY) { log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to init library: %s", opendmarc_policy_status_to_str(libdm_status)); dmarc_abort = TRUE; } if (dmarc_tld_file == NULL) dmarc_abort = TRUE; else if (opendmarc_tld_read_file(tld_file, NULL, NULL, NULL)) { log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to load tld list %s: %d", tld_file, errno); dmarc_abort = TRUE; } if (sender_host_address == NULL) dmarc_abort = TRUE; /* This catches locally originated email and startup errors above. */ if ( dmarc_abort == FALSE ) { is_ipv6 = string_is_ip_address(sender_host_address, netmask); is_ipv6 = (is_ipv6 == 6) ? TRUE : (is_ipv6 == 4) ? FALSE : FALSE; dmarc_pctx = opendmarc_policy_connect_init(sender_host_address, is_ipv6); if (dmarc_pctx == NULL ) { log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure creating policy context: ip=%s", sender_host_address); dmarc_abort = TRUE; } } return OK; } /* dmarc_store_data stores the header data so that subsequent * dmarc_process can access the data */ int dmarc_store_data(header_line *hdr) { /* No debug output because would change every test debug output */ if (dmarc_disable_verify != TRUE) from_header = hdr; return OK; } /* dmarc_process adds the envelope sender address to the existing context (if any), retrieves the result, sets up expansion strings and evaluates the condition outcome. */ int dmarc_process() { int sr, origin; /* used in SPF section */ int dmarc_spf_result = 0; /* stores spf into dmarc conn ctx */ pdkim_signature *sig = NULL; BOOL has_dmarc_record = TRUE; u_char **ruf; /* forensic report addressees, if called for */ /* ACLs have "control=dmarc_disable_verify" */ if (dmarc_disable_verify == TRUE) { dmarc_ar_header = dmarc_auth_results_header(from_header, NULL); return OK; } /* Store the header From: sender domain for this part of DMARC. * If there is no from_header struct, then it's likely this message * is locally generated and relying on fixups to add it. Just skip * the entire DMARC system if we can't find a From: header....or if * there was a previous error. */ if (from_header == NULL || dmarc_abort == TRUE) dmarc_abort = TRUE; else { /* I strongly encourage anybody who can make this better to contact me directly! * Is this an insane way to extract the email address from the From: header? * it's sure a horrid layer-crossing.... * I'm not denying that :-/ * there may well be no better though */ header_from_sender = expand_string( string_sprintf("${domain:${extract{1}{:}{${addresses:%s}}}}", from_header->text) ); /* The opendmarc library extracts the domain from the email address, but * only try to store it if it's not empty. Otherwise, skip out of DMARC. */ if (strcmp( CCS header_from_sender, "") == 0) dmarc_abort = TRUE; libdm_status = (dmarc_abort == TRUE) ? DMARC_PARSE_OKAY : opendmarc_policy_store_from_domain(dmarc_pctx, header_from_sender); if (libdm_status != DMARC_PARSE_OKAY) { log_write(0, LOG_MAIN|LOG_PANIC, "failure to store header From: in DMARC: %s, header was '%s'", opendmarc_policy_status_to_str(libdm_status), from_header->text); dmarc_abort = TRUE; } } /* Skip DMARC if connection is SMTP Auth. Temporarily, admin should * instead do this in the ACLs. */ if (dmarc_abort == FALSE && sender_host_authenticated == NULL) { /* Use the envelope sender domain for this part of DMARC */ spf_sender_domain = expand_string(US"$sender_address_domain"); if ( spf_response == NULL ) { /* No spf data means null envelope sender so generate a domain name * from the sender_helo_name */ if (spf_sender_domain == NULL) { spf_sender_domain = sender_helo_name; log_write(0, LOG_MAIN, "DMARC using synthesized SPF sender domain = %s\n", spf_sender_domain); DEBUG(D_receive) debug_printf("DMARC using synthesized SPF sender domain = %s\n", spf_sender_domain); } dmarc_spf_result = DMARC_POLICY_SPF_OUTCOME_NONE; dmarc_spf_ares_result = ARES_RESULT_UNKNOWN; origin = DMARC_POLICY_SPF_ORIGIN_HELO; spf_human_readable = US""; } else { sr = spf_response->result; dmarc_spf_result = (sr == SPF_RESULT_NEUTRAL) ? DMARC_POLICY_SPF_OUTCOME_NONE : (sr == SPF_RESULT_PASS) ? DMARC_POLICY_SPF_OUTCOME_PASS : (sr == SPF_RESULT_FAIL) ? DMARC_POLICY_SPF_OUTCOME_FAIL : (sr == SPF_RESULT_SOFTFAIL) ? DMARC_POLICY_SPF_OUTCOME_TMPFAIL : DMARC_POLICY_SPF_OUTCOME_NONE; dmarc_spf_ares_result = (sr == SPF_RESULT_NEUTRAL) ? ARES_RESULT_NEUTRAL : (sr == SPF_RESULT_PASS) ? ARES_RESULT_PASS : (sr == SPF_RESULT_FAIL) ? ARES_RESULT_FAIL : (sr == SPF_RESULT_SOFTFAIL) ? ARES_RESULT_SOFTFAIL : (sr == SPF_RESULT_NONE) ? ARES_RESULT_NONE : (sr == SPF_RESULT_TEMPERROR) ? ARES_RESULT_TEMPERROR : (sr == SPF_RESULT_PERMERROR) ? ARES_RESULT_PERMERROR : ARES_RESULT_UNKNOWN; origin = DMARC_POLICY_SPF_ORIGIN_MAILFROM; spf_human_readable = (uschar *)spf_response->header_comment; DEBUG(D_receive) debug_printf("DMARC using SPF sender domain = %s\n", spf_sender_domain); } if (strcmp( CCS spf_sender_domain, "") == 0) dmarc_abort = TRUE; if (dmarc_abort == FALSE) { libdm_status = opendmarc_policy_store_spf(dmarc_pctx, spf_sender_domain, dmarc_spf_result, origin, spf_human_readable); if (libdm_status != DMARC_PARSE_OKAY) log_write(0, LOG_MAIN|LOG_PANIC, "failure to store spf for DMARC: %s", opendmarc_policy_status_to_str(libdm_status)); } /* Now we cycle through the dkim signature results and put into * the opendmarc context, further building the DMARC reply. */ sig = dkim_signatures; dkim_history_buffer = US""; while (sig != NULL) { int dkim_result, dkim_ares_result, vs, ves; vs = sig->verify_status; ves = sig->verify_ext_status; dkim_result = ( vs == PDKIM_VERIFY_PASS ) ? DMARC_POLICY_DKIM_OUTCOME_PASS : ( vs == PDKIM_VERIFY_FAIL ) ? DMARC_POLICY_DKIM_OUTCOME_FAIL : ( vs == PDKIM_VERIFY_INVALID ) ? DMARC_POLICY_DKIM_OUTCOME_TMPFAIL : DMARC_POLICY_DKIM_OUTCOME_NONE; libdm_status = opendmarc_policy_store_dkim(dmarc_pctx, (uschar *)sig->domain, dkim_result, US""); DEBUG(D_receive) debug_printf("DMARC adding DKIM sender domain = %s\n", sig->domain); if (libdm_status != DMARC_PARSE_OKAY) log_write(0, LOG_MAIN|LOG_PANIC, "failure to store dkim (%s) for DMARC: %s", sig->domain, opendmarc_policy_status_to_str(libdm_status)); dkim_ares_result = ( vs == PDKIM_VERIFY_PASS ) ? ARES_RESULT_PASS : ( vs == PDKIM_VERIFY_FAIL ) ? ARES_RESULT_FAIL : ( vs == PDKIM_VERIFY_NONE ) ? ARES_RESULT_NONE : ( vs == PDKIM_VERIFY_INVALID ) ? ( ves == PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE ? ARES_RESULT_PERMERROR : ves == PDKIM_VERIFY_INVALID_BUFFER_SIZE ? ARES_RESULT_PERMERROR : ves == PDKIM_VERIFY_INVALID_PUBKEY_PARSING ? ARES_RESULT_PERMERROR : ARES_RESULT_UNKNOWN ) : ARES_RESULT_UNKNOWN; dkim_history_buffer = string_sprintf("%sdkim %s %d\n", dkim_history_buffer, sig->domain, dkim_ares_result); sig = sig->next; } libdm_status = opendmarc_policy_query_dmarc(dmarc_pctx, US""); switch (libdm_status) { case DMARC_DNS_ERROR_NXDOMAIN: case DMARC_DNS_ERROR_NO_RECORD: DEBUG(D_receive) debug_printf("DMARC no record found for %s\n", header_from_sender); has_dmarc_record = FALSE; break; case DMARC_PARSE_OKAY: DEBUG(D_receive) debug_printf("DMARC record found for %s\n", header_from_sender); break; case DMARC_PARSE_ERROR_BAD_VALUE: DEBUG(D_receive) debug_printf("DMARC record parse error for %s\n", header_from_sender); has_dmarc_record = FALSE; break; default: /* everything else, skip dmarc */ DEBUG(D_receive) debug_printf("DMARC skipping (%d), unsure what to do with %s", libdm_status, from_header->text); has_dmarc_record = FALSE; break; } /* Can't use exim's string manipulation functions so allocate memory * for libopendmarc using its max hostname length definition. */ uschar *dmarc_domain = (uschar *)calloc(DMARC_MAXHOSTNAMELEN, sizeof(uschar)); libdm_status = opendmarc_policy_fetch_utilized_domain(dmarc_pctx, dmarc_domain, DMARC_MAXHOSTNAMELEN-1); dmarc_used_domain = string_copy(dmarc_domain); free(dmarc_domain); if (libdm_status != DMARC_PARSE_OKAY) { log_write(0, LOG_MAIN|LOG_PANIC, "failure to read domainname used for DMARC lookup: %s", opendmarc_policy_status_to_str(libdm_status)); } libdm_status = opendmarc_get_policy_to_enforce(dmarc_pctx); dmarc_policy = libdm_status; switch(libdm_status) { case DMARC_POLICY_ABSENT: /* No DMARC record found */ dmarc_status = US"norecord"; dmarc_pass_fail = US"temperror"; dmarc_status_text = US"No DMARC record"; action = DMARC_RESULT_ACCEPT; break; case DMARC_FROM_DOMAIN_ABSENT: /* No From: domain */ dmarc_status = US"nofrom"; dmarc_pass_fail = US"temperror"; dmarc_status_text = US"No From: domain found"; action = DMARC_RESULT_ACCEPT; break; case DMARC_POLICY_NONE: /* Accept and report */ dmarc_status = US"none"; dmarc_pass_fail = US"none"; dmarc_status_text = US"None, Accept"; action = DMARC_RESULT_ACCEPT; break; case DMARC_POLICY_PASS: /* Explicit accept */ dmarc_status = US"accept"; dmarc_pass_fail = US"pass"; dmarc_status_text = US"Accept"; action = DMARC_RESULT_ACCEPT; break; case DMARC_POLICY_REJECT: /* Explicit reject */ dmarc_status = US"reject"; dmarc_pass_fail = US"fail"; dmarc_status_text = US"Reject"; action = DMARC_RESULT_REJECT; break; case DMARC_POLICY_QUARANTINE: /* Explicit quarantine */ dmarc_status = US"quarantine"; dmarc_pass_fail = US"fail"; dmarc_status_text = US"Quarantine"; action = DMARC_RESULT_QUARANTINE; break; default: dmarc_status = US"temperror"; dmarc_pass_fail = US"temperror"; dmarc_status_text = US"Internal Policy Error"; action = DMARC_RESULT_TEMPFAIL; break; } libdm_status = opendmarc_policy_fetch_alignment(dmarc_pctx, &da, &sa); if (libdm_status != DMARC_PARSE_OKAY) { log_write(0, LOG_MAIN|LOG_PANIC, "failure to read DMARC alignment: %s", opendmarc_policy_status_to_str(libdm_status)); } if (has_dmarc_record == TRUE) { log_write(0, LOG_MAIN, "DMARC results: spf_domain=%s dmarc_domain=%s " "spf_align=%s dkim_align=%s enforcement='%s'", spf_sender_domain, dmarc_used_domain, (sa==DMARC_POLICY_SPF_ALIGNMENT_PASS) ?"yes":"no", (da==DMARC_POLICY_DKIM_ALIGNMENT_PASS)?"yes":"no", dmarc_status_text); history_file_status = dmarc_write_history_file(); /* Now get the forensic reporting addresses, if any */ ruf = opendmarc_policy_fetch_ruf(dmarc_pctx, NULL, 0, 1); dmarc_send_forensic_report(ruf); } } /* set some global variables here */ dmarc_ar_header = dmarc_auth_results_header(from_header, NULL); /* shut down libopendmarc */ if ( dmarc_pctx != NULL ) (void) opendmarc_policy_connect_shutdown(dmarc_pctx); if ( dmarc_disable_verify == FALSE ) (void) opendmarc_policy_library_shutdown(&dmarc_ctx); return OK; } int dmarc_write_history_file() { int history_file_fd; ssize_t written_len; int tmp_ans; u_char **rua; /* aggregate report addressees */ uschar *history_buffer = NULL; if (dmarc_history_file == NULL) return DMARC_HIST_DISABLED; history_file_fd = log_create(dmarc_history_file); if (history_file_fd < 0) { log_write(0, LOG_MAIN|LOG_PANIC, "failure to create DMARC history file: %s", dmarc_history_file); return DMARC_HIST_FILE_ERR; } /* Generate the contents of the history file */ history_buffer = string_sprintf("job %s\n", message_id); history_buffer = string_sprintf("%sreporter %s\n", history_buffer, primary_hostname); history_buffer = string_sprintf("%sreceived %ld\n", history_buffer, time(NULL)); history_buffer = string_sprintf("%sipaddr %s\n", history_buffer, sender_host_address); history_buffer = string_sprintf("%sfrom %s\n", history_buffer, header_from_sender); history_buffer = string_sprintf("%smfrom %s\n", history_buffer, expand_string(US"$sender_address_domain")); if (spf_response != NULL) history_buffer = string_sprintf("%sspf %d\n", history_buffer, dmarc_spf_ares_result); // history_buffer = string_sprintf("%sspf -1\n", history_buffer); history_buffer = string_sprintf("%s%s", history_buffer, dkim_history_buffer); history_buffer = string_sprintf("%spdomain %s\n", history_buffer, dmarc_used_domain); history_buffer = string_sprintf("%spolicy %d\n", history_buffer, dmarc_policy); rua = opendmarc_policy_fetch_rua(dmarc_pctx, NULL, 0, 1); if (rua != NULL) { for (tmp_ans = 0; rua[tmp_ans] != NULL; tmp_ans++) { history_buffer = string_sprintf("%srua %s\n", history_buffer, rua[tmp_ans]); } } else history_buffer = string_sprintf("%srua -\n", history_buffer); opendmarc_policy_fetch_pct(dmarc_pctx, &tmp_ans); history_buffer = string_sprintf("%spct %d\n", history_buffer, tmp_ans); opendmarc_policy_fetch_adkim(dmarc_pctx, &tmp_ans); history_buffer = string_sprintf("%sadkim %d\n", history_buffer, tmp_ans); opendmarc_policy_fetch_aspf(dmarc_pctx, &tmp_ans); history_buffer = string_sprintf("%saspf %d\n", history_buffer, tmp_ans); opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans); history_buffer = string_sprintf("%sp %d\n", history_buffer, tmp_ans); opendmarc_policy_fetch_sp(dmarc_pctx, &tmp_ans); history_buffer = string_sprintf("%ssp %d\n", history_buffer, tmp_ans); history_buffer = string_sprintf("%salign_dkim %d\n", history_buffer, da); history_buffer = string_sprintf("%salign_spf %d\n", history_buffer, sa); history_buffer = string_sprintf("%saction %d\n", history_buffer, action); /* Write the contents to the history file */ DEBUG(D_receive) debug_printf("DMARC logging history data for opendmarc reporting%s\n", (host_checking || running_in_test_harness) ? " (not really)" : ""); if (host_checking || running_in_test_harness) { DEBUG(D_receive) debug_printf("DMARC history data for debugging:\n%s", history_buffer); } else { written_len = write_to_fd_buf(history_file_fd, history_buffer, Ustrlen(history_buffer)); if (written_len == 0) { log_write(0, LOG_MAIN|LOG_PANIC, "failure to write to DMARC history file: %s", dmarc_history_file); return DMARC_HIST_WRITE_ERR; } (void)close(history_file_fd); } return DMARC_HIST_OK; } void dmarc_send_forensic_report(u_char **ruf) { int c; uschar *recipient, *save_sender; BOOL send_status = FALSE; error_block *eblock = NULL; FILE *message_file = NULL; /* Earlier ACL does not have *required* control=dmarc_enable_forensic */ if (dmarc_enable_forensic == FALSE) return; if ((dmarc_policy == DMARC_POLICY_REJECT && action == DMARC_RESULT_REJECT) || (dmarc_policy == DMARC_POLICY_QUARANTINE && action == DMARC_RESULT_QUARANTINE) ) { if (ruf != NULL) { eblock = add_to_eblock(eblock, US"Sender Domain", dmarc_used_domain); eblock = add_to_eblock(eblock, US"Sender IP Address", sender_host_address); eblock = add_to_eblock(eblock, US"Received Date", tod_stamp(tod_full)); eblock = add_to_eblock(eblock, US"SPF Alignment", (sa==DMARC_POLICY_SPF_ALIGNMENT_PASS) ?US"yes":US"no"); eblock = add_to_eblock(eblock, US"DKIM Alignment", (da==DMARC_POLICY_DKIM_ALIGNMENT_PASS)?US"yes":US"no"); eblock = add_to_eblock(eblock, US"DMARC Results", dmarc_status_text); /* Set a sane default envelope sender */ dsn_from = dmarc_forensic_sender ? dmarc_forensic_sender : dsn_from ? dsn_from : string_sprintf("do-not-reply@%s",primary_hostname); for (c = 0; ruf[c] != NULL; c++) { recipient = string_copylc(ruf[c]); if (Ustrncmp(recipient, "mailto:",7)) continue; /* Move to first character past the colon */ recipient += 7; DEBUG(D_receive) debug_printf("DMARC forensic report to %s%s\n", recipient, (host_checking || running_in_test_harness) ? " (not really)" : ""); if (host_checking || running_in_test_harness) continue; save_sender = sender_address; sender_address = recipient; send_status = moan_to_sender(ERRMESS_DMARC_FORENSIC, eblock, header_list, message_file, FALSE); sender_address = save_sender; if (send_status == FALSE) log_write(0, LOG_MAIN|LOG_PANIC, "failure to send DMARC forensic report to %s", recipient); } } } } uschar *dmarc_exim_expand_query(int what) { if (dmarc_disable_verify || !dmarc_pctx) return dmarc_exim_expand_defaults(what); switch(what) { case DMARC_VERIFY_STATUS: return(dmarc_status); default: return US""; } } uschar *dmarc_exim_expand_defaults(int what) { switch(what) { case DMARC_VERIFY_STATUS: return (dmarc_disable_verify) ? US"off" : US"none"; default: return US""; } } uschar *dmarc_auth_results_header(header_line *from_header, uschar *hostname) { uschar *hdr_tmp = US""; /* Allow a server hostname to be passed to this function, but is * currently unused */ if (hostname == NULL) hostname = primary_hostname; hdr_tmp = string_sprintf("%s %s;", DMARC_AR_HEADER, hostname); #if 0 /* I don't think this belongs here, but left it here commented out * because it was a lot of work to get working right. */ if (spf_response != NULL) { uschar *dmarc_ar_spf = US""; int sr = 0; sr = spf_response->result; dmarc_ar_spf = (sr == SPF_RESULT_NEUTRAL) ? US"neutral" : (sr == SPF_RESULT_PASS) ? US"pass" : (sr == SPF_RESULT_FAIL) ? US"fail" : (sr == SPF_RESULT_SOFTFAIL) ? US"softfail" : US"none"; hdr_tmp = string_sprintf("%s spf=%s (%s) smtp.mail=%s;", hdr_tmp, dmarc_ar_spf_result, spf_response->header_comment, expand_string(US"$sender_address") ); } #endif hdr_tmp = string_sprintf("%s dmarc=%s", hdr_tmp, dmarc_pass_fail); if (header_from_sender) hdr_tmp = string_sprintf("%s header.from=%s", hdr_tmp, header_from_sender); return hdr_tmp; } #endif /* EXPERIMENTAL_SPF */ #endif /* EXPERIMENTAL_DMARC */ // vim:sw=2 expandtab