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-rw-r--r--src/spf.c420
1 files changed, 420 insertions, 0 deletions
diff --git a/src/spf.c b/src/spf.c
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+++ b/src/spf.c
@@ -0,0 +1,420 @@
+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/* SPF support.
+ Copyright (c) The Exim Maintainers 2015 - 2022
+ Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004 - 2014
+ License: GPL
+*/
+
+/* Code for calling spf checks via libspf-alt. Called from acl.c. */
+
+#include "exim.h"
+#ifdef SUPPORT_SPF
+
+/* must be kept in numeric order */
+static spf_result_id spf_result_id_list[] = {
+ /* name value */
+ { US"invalid", 0},
+ { US"neutral", 1 },
+ { US"pass", 2 },
+ { US"fail", 3 },
+ { US"softfail", 4 },
+ { US"none", 5 },
+ { US"temperror", 6 }, /* RFC 4408 defined */
+ { US"permerror", 7 } /* RFC 4408 defined */
+};
+
+SPF_server_t *spf_server = NULL;
+SPF_request_t *spf_request = NULL;
+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
+};
+int dns_rc;
+
+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_rc = dns_lookup(dnsa, US domain, rr_type, NULL))
+ {
+ case DNS_SUCCEED: srr.herrno = NETDB_SUCCESS; break;
+ 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;
+ }
+
+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) found++;
+
+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:
+ 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 (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;
+ }
+
+ for (int off = 0; off < rr->size; off += chunk_len)
+ {
+ if (!(chunk_len = s[off++])) 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)
+ {
+ free(spf_dns_server);
+ return NULL;
+ }
+
+return spf_dns_server;
+}
+
+
+
+
+/* Construct the SPF library stack.
+ Return: Boolean success.
+*/
+
+BOOL
+spf_init(void)
+{
+SPF_dns_server_t * dc;
+int debug = 0;
+const uschar *s;
+
+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))
+ {
+ DEBUG(D_receive) debug_printf("spf: SPF_server_set_rec_dom(\"%s\") failed.\n",
+ primary_hostname);
+ spf_server = NULL;
+ return FALSE;
+ }
+
+spf_request = SPF_request_new(spf_server);
+
+if ( SPF_request_set_ipv4_str(spf_request, CS spf_remote_addr)
+ && SPF_request_set_ipv6_str(spf_request, CS spf_remote_addr)
+ )
+ {
+ DEBUG(D_receive)
+ debug_printf("spf: SPF_request_set_ipv4_str() and "
+ "SPF_request_set_ipv6_str() failed [%s]\n", spf_remote_addr);
+ spf_server = NULL;
+ spf_request = NULL;
+ return FALSE;
+ }
+
+if (SPF_request_set_helo_dom(spf_request, CS spf_helo_domain))
+ {
+ DEBUG(D_receive) debug_printf("spf: SPF_set_helo_dom(\"%s\") failed.\n",
+ spf_helo_domain);
+ spf_server = NULL;
+ spf_request = NULL;
+ return FALSE;
+ }
+
+return TRUE;
+}
+
+
+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.
+
+Return: OK/FAIL */
+
+int
+spf_process(const uschar **listptr, uschar *spf_envelope_sender, int action)
+{
+int sep = 0;
+const uschar *list = *listptr;
+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;
+
+else if (SPF_request_set_env_from(spf_request, CS spf_envelope_sender))
+ /* Invalid sender address. This should be a real rare occurrence */
+ rc = SPF_RESULT_PERMERROR;
+
+else
+ {
+ /* get SPF result */
+ if (action == SPF_PROCESS_FALLBACK)
+ {
+ SPF_request_query_fallback(spf_request, &spf_response, CS spf_guess);
+ spf_result_guessed = TRUE;
+ }
+ else
+ SPF_request_query_mailfrom(spf_request, &spf_response);
+
+ /* set up expansion items */
+ spf_header_comment = US SPF_response_get_header_comment(spf_response);
+ spf_received = US SPF_response_get_received_spf(spf_response);
+ spf_result = US SPF_strresult(SPF_response_result(spf_response));
+ 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 */
+DEBUG(D_acl) debug_printf("SPF result is %s (%d)\n", SPF_strresult(rc), rc);
+
+if (action == SPF_PROCESS_GUESS && (!strcmp (SPF_strresult(rc), "none")))
+ return spf_process(listptr, spf_envelope_sender, SPF_PROCESS_FALLBACK);
+
+while ((spf_result_id = string_nextinlist(&list, &sep, NULL, 0)))
+ {
+ BOOL negate, result;
+
+ if ((negate = spf_result_id[0] == '!'))
+ spf_result_id++;
+
+ result = Ustrcmp(spf_result_id, spf_result_id_list[rc].name) == 0;
+ if (negate != result) return OK;
+ }
+
+/* no match */
+return FAIL;
+}
+
+
+
+gstring *
+authres_spf(gstring * g)
+{
+uschar * s;
+if (!spf_result) return 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)");
+
+s = expand_string(US"$sender_address_domain");
+if (s && *s)
+ return string_append(g, 2, US" smtp.mailfrom=", s);
+
+s = sender_helo_name;
+return s && *s
+ ? string_append(g, 2, US" smtp.helo=", s)
+ : string_cat(g, US" smtp.mailfrom=<>");
+}
+
+
+#endif
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