* Exim - an Internet mail transport agent *
*************************************************/
-/* Experimental SPF support.
+/* SPF support.
+ Copyright (c) The Exim Maintainers 2015 - 2023
Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004 - 2014
License: GPL
- Copyright (c) The Exim Maintainers 2015 - 2018
+ SPDX-License-Identifier: GPL-2.0-or-later
*/
/* Code for calling spf checks via libspf-alt. Called from acl.c. */
SPF_response_t *spf_response = NULL;
SPF_response_t *spf_response_2mx = NULL;
+SPF_dns_rr_t * spf_nxdomain = NULL;
+
+
+gstring *
+spf_lib_version_report(gstring * g)
+{
+int maj, min, patch;
+
+SPF_get_lib_version(&maj, &min, &patch);
+g = string_fmt_append(g, "Library version: spf2: Compile: %d.%d.%d\n",
+ SPF_LIB_VERSION_MAJOR, SPF_LIB_VERSION_MINOR, SPF_LIB_VERSION_PATCH);
+g = string_fmt_append(g, " Runtime: %d.%d.%d\n",
+ maj, min, patch);
+return g;
+}
+
+
+
+static SPF_dns_rr_t *
+SPF_dns_exim_lookup(SPF_dns_server_t *spf_dns_server,
+ const char *domain, ns_type rr_type, int should_cache)
+{
+dns_answer * dnsa = store_get_dns_answer();
+dns_scan dnss;
+SPF_dns_rr_t * spfrr;
+unsigned found = 0;
+
+SPF_dns_rr_t srr = {
+ .domain = CS domain, /* query information */
+ .domain_buf_len = 0,
+ .rr_type = rr_type,
+
+ .rr_buf_len = 0, /* answer information */
+ .rr_buf_num = 0, /* no free of s */
+ .utc_ttl = 0,
+
+ .hook = NULL, /* misc information */
+ .source = spf_dns_server
+};
+
+DEBUG(D_receive) debug_printf("SPF_dns_exim_lookup '%s'\n", domain);
+
+/* Shortcircuit SPF RR lookups by returning NO_DATA. They were obsoleted by
+RFC 6686/7208 years ago. see bug #1294 */
+
+if (rr_type == T_SPF)
+ {
+ HDEBUG(D_host_lookup) debug_printf("faking NO_DATA for SPF RR(99) lookup\n");
+ srr.herrno = NO_DATA;
+ SPF_dns_rr_dup(&spfrr, &srr);
+ store_free_dns_answer(dnsa);
+ return spfrr;
+ }
+
+switch (dns_lookup(dnsa, US domain, rr_type, NULL))
+ {
+ case DNS_AGAIN: srr.herrno = TRY_AGAIN; break;
+ case DNS_NOMATCH: srr.herrno = HOST_NOT_FOUND; break;
+ case DNS_NODATA: srr.herrno = NO_DATA; break;
+ case DNS_FAIL:
+ default: srr.herrno = NO_RECOVERY; break;
+ case DNS_SUCCEED:
+ srr.herrno = NETDB_SUCCESS;
+ for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
+ rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ /* Need to alloc space for all records, so no early-out */
+ if (rr->type == rr_type) found++;
+ break;
+ }
+
+if (found == 0)
+ {
+ SPF_dns_rr_dup(&spfrr, &srr);
+ store_free_dns_answer(dnsa);
+ return spfrr;
+ }
+
+srr.rr = store_malloc(sizeof(SPF_dns_rr_data_t) * found);
+
+found = 0;
+for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
+ rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ if (rr->type == rr_type)
+ {
+ const uschar * s = rr->data;
+
+ srr.ttl = rr->ttl;
+ switch(rr_type)
+ {
+ case T_MX:
+ if (rr->size < 2) continue;
+ s += 2; /* skip the MX precedence field */
+ case T_PTR:
+ {
+ uschar * buf = store_malloc(256);
+ (void)dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, s,
+ (DN_EXPAND_ARG4_TYPE)buf, 256);
+ s = buf;
+ break;
+ }
+
+ case T_TXT:
+ {
+ gstring * g = NULL;
+ uschar chunk_len;
+
+ if (rr->size < 1+6) continue; /* min for version str */
+ if (strncmpic(rr->data+1, US SPF_VER_STR, 6) != 0)
+ {
+ HDEBUG(D_host_lookup) debug_printf("not an spf record: %.*s\n",
+ (int) s[0], s+1);
+ continue;
+ }
+
+ /* require 1 byte for the chunk_len */
+ for (int off = 0; off < rr->size - 1; off += chunk_len)
+ {
+ if ( !(chunk_len = s[off++])
+ || rr->size < off + chunk_len /* ignore bogus size chunks */
+ ) break;
+ g = string_catn(g, s+off, chunk_len);
+ }
+ if (!g)
+ continue;
+ gstring_release_unused(g);
+ s = string_copy_malloc(string_from_gstring(g));
+ DEBUG(D_receive) debug_printf("SPF_dns_exim_lookup '%s'\n", s);
+ break;
+ }
+
+ case T_A:
+ case T_AAAA:
+ default:
+ {
+ uschar * buf = store_malloc(dnsa->answerlen + 1);
+ s = memcpy(buf, s, dnsa->answerlen + 1);
+ break;
+ }
+ }
+ srr.rr[found++] = (void *) s;
+ }
+
+/* Did we filter out all TXT RRs? Return NO_DATA instead of SUCCESS with
+empty ANSWER section. */
+
+if (!(srr.num_rr = found))
+ srr.herrno = NO_DATA;
+
+/* spfrr->rr must have been malloc()d for this */
+SPF_dns_rr_dup(&spfrr, &srr);
+store_free_dns_answer(dnsa);
+return spfrr;
+}
+
+
+
+SPF_dns_server_t *
+SPF_dns_exim_new(int debug)
+{
+SPF_dns_server_t * spf_dns_server = store_malloc(sizeof(SPF_dns_server_t));
+
+DEBUG(D_receive) debug_printf("SPF_dns_exim_new\n");
+
+memset(spf_dns_server, 0, sizeof(SPF_dns_server_t));
+spf_dns_server->destroy = NULL;
+spf_dns_server->lookup = SPF_dns_exim_lookup;
+spf_dns_server->get_spf = NULL;
+spf_dns_server->get_exp = NULL;
+spf_dns_server->add_cache = NULL;
+spf_dns_server->layer_below = NULL;
+spf_dns_server->name = "exim";
+spf_dns_server->debug = debug;
+
+/* XXX This might have to return NO_DATA sometimes. */
+
+spf_nxdomain = SPF_dns_rr_new_init(spf_dns_server,
+ "", ns_t_any, 24 * 60 * 60, HOST_NOT_FOUND);
+if (!spf_nxdomain)
+ {
+ store_free(spf_dns_server);
+ return NULL;
+ }
+
+return spf_dns_server;
+}
+
-/* spf_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)
-Return: Boolean success */
+
+/* Construct the SPF library stack.
+ Return: Boolean success.
+*/
BOOL
-spf_init(uschar *spf_helo_domain, uschar *spf_remote_addr)
+spf_init(void)
{
-spf_server = SPF_server_new(SPF_DNS_CACHE, 0);
+SPF_dns_server_t * dc;
+int debug = 0;
+const uschar *s;
-if (!spf_server)
+DEBUG(D_receive) debug = 1;
+
+/* We insert our own DNS access layer rather than letting the spf library
+do it, so that our dns access path is used for debug tracing and for the
+testsuite. */
+
+if (!(dc = SPF_dns_exim_new(debug)))
+ {
+ DEBUG(D_receive) debug_printf("spf: SPF_dns_exim_new() failed\n");
+ return FALSE;
+ }
+if (!(dc = SPF_dns_cache_new(dc, NULL, debug, 8)))
+ {
+ DEBUG(D_receive) debug_printf("spf: SPF_dns_cache_new() failed\n");
+ return FALSE;
+ }
+if (!(spf_server = SPF_server_new_dns(dc, debug)))
{
DEBUG(D_receive) debug_printf("spf: SPF_server_new() failed.\n");
return FALSE;
}
+ /* Override the outdated explanation URL.
+ See https://www.mail-archive.com/mailop@mailop.org/msg08019.html
+ Used to work as "Please%_see%_http://www.open-spf.org/Why?id=%{S}&ip=%{C}&receiver=%{R}",
+ but is broken now (May 18th, 2020) */
+if (!(s = expand_string(spf_smtp_comment_template)))
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "expansion of spf_smtp_comment_template failed");
+
+SPF_server_set_explanation(spf_server, CCS s, &spf_response);
+if (SPF_response_errcode(spf_response) != SPF_E_SUCCESS)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "%s", SPF_strerror(SPF_response_errcode(spf_response)));
+
+return TRUE;
+}
+
+
+/* Set 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).
+
+Return: Boolean success
+*/
+
+BOOL
+spf_conn_init(uschar * spf_helo_domain, uschar * spf_remote_addr)
+{
+DEBUG(D_receive)
+ debug_printf("spf_conn_init: %s %s\n", spf_helo_domain, spf_remote_addr);
+
+if (!spf_server && !spf_init()) return FALSE;
if (SPF_server_set_rec_dom(spf_server, CS primary_hostname))
{
}
+void
+spf_response_debug(SPF_response_t * spf_response)
+{
+if (SPF_response_messages(spf_response) == 0)
+ debug_printf(" (no errors)\n");
+else for (int i = 0; i < SPF_response_messages(spf_response); i++)
+ {
+ SPF_error_t * err = SPF_response_message(spf_response, i);
+ debug_printf( "%s_msg = (%d) %s\n",
+ (SPF_error_errorp(err) ? "warn" : "err"),
+ SPF_error_code(err),
+ SPF_error_message(err));
+ }
+}
+
+
/* spf_process adds the envelope sender address to the existing
context (if any), retrieves the result, sets up expansion
strings and evaluates the condition outcome.
uschar *spf_result_id;
int rc = SPF_RESULT_PERMERROR;
+DEBUG(D_receive) debug_printf("spf_process\n");
+
if (!(spf_server && spf_request))
/* no global context, assume temp error and skip to evaluation */
rc = SPF_RESULT_PERMERROR;
spf_smtp_comment = US SPF_response_get_smtp_comment(spf_response);
rc = SPF_response_result(spf_response);
+
+ DEBUG(D_acl) spf_response_debug(spf_response);
}
/* We got a result. Now see if we should return OK or FAIL for it */
authres_spf(gstring * g)
{
uschar * s;
-if (!spf_result) return g;
+if (spf_result)
+ {
+ int start = 0; /* Compiler quietening */
+ DEBUG(D_acl) start = gstring_length(g);
-g = string_append(g, 2, US";\n\tspf=", spf_result);
-if (spf_result_guessed)
- g = string_cat(g, US" (best guess record for domain)");
+ g = string_append(g, 2, US";\n\tspf=", spf_result);
+ if (spf_result_guessed)
+ g = string_cat(g, US" (best guess record for domain)");
-s = expand_string(US"$sender_address_domain");
-return s && *s
- ? string_append(g, 2, US" smtp.mailfrom=", s)
- : string_cat(g, US" smtp.mailfrom=<>");
+ s = expand_string(US"$sender_address_domain");
+ if (s && *s)
+ g = string_append(g, 2, US" smtp.mailfrom=", s);
+ else
+ {
+ s = sender_helo_name;
+ g = s && *s
+ ? string_append(g, 2, US" smtp.helo=", s)
+ : string_cat(g, US" smtp.mailfrom=<>");
+ }
+ DEBUG(D_acl) debug_printf("SPF:\tauthres '%.*s'\n",
+ gstring_length(g) - start - 3, g->s + start + 3);
+ }
+else
+ DEBUG(D_acl) debug_printf("SPF:\tno authres\n");
+return g;
}
git://git.exim.org / exim.git / blobdiff