src/src/spf.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Experimental SPF support.
   6    Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004 - 2014
   7    License: GPL
   8    Copyright (c) The Exim Maintainers 2016
   9 */
  10
  11 /* Code for calling spf checks via libspf-alt. Called from acl.c. */
  12
  13 #include "exim.h"
  14 #ifdef EXPERIMENTAL_SPF
  15
  16 /* must be kept in numeric order */
  17 static spf_result_id spf_result_id_list[] = {
  18   { US"invalid", 0},
  19   { US"neutral", 1 },
  20   { US"pass", 2 },
  21   { US"fail", 3 },
  22   { US"softfail", 4 },
  23   { US"none", 5 },
  24   { US"err_temp", 6 },  /* Deprecated Apr 2014 */
  25   { US"err_perm", 7 },  /* Deprecated Apr 2014 */
  26   { US"temperror", 6 }, /* RFC 4408 defined */
  27   { US"permerror", 7 }  /* RFC 4408 defined */
  28 };
  29
  30 SPF_server_t    *spf_server = NULL;
  31 SPF_request_t   *spf_request = NULL;
  32 SPF_response_t  *spf_response = NULL;
  33 SPF_response_t  *spf_response_2mx = NULL;
  34
  35 /* spf_init sets up a context that can be re-used for several
  36    messages on the same SMTP connection (that come from the
  37    same host with the same HELO string) */
  38
  39 int spf_init(uschar *spf_helo_domain, uschar *spf_remote_addr) {
  40
  41   spf_server = SPF_server_new(SPF_DNS_CACHE, 0);
  42
  43   if ( spf_server == NULL ) {
  44     debug_printf("spf: SPF_server_new() failed.\n");
  45     return 0;
  46   }
  47
  48   if (SPF_server_set_rec_dom(spf_server, CS primary_hostname)) {
  49     debug_printf("spf: SPF_server_set_rec_dom(\"%s\") failed.\n", primary_hostname);
  50     spf_server = NULL;
  51     return 0;
  52   }
  53
  54   spf_request = SPF_request_new(spf_server);
  55
  56   if (SPF_request_set_ipv4_str(spf_request, CS spf_remote_addr)
  57       && SPF_request_set_ipv6_str(spf_request, CS spf_remote_addr)) {
  58     debug_printf("spf: SPF_request_set_ipv4_str() and SPF_request_set_ipv6_str() failed [%s]\n", spf_remote_addr);
  59     spf_server = NULL;
  60     spf_request = NULL;
  61     return 0;
  62   }
  63
  64   if (SPF_request_set_helo_dom(spf_request, CS spf_helo_domain)) {
  65     debug_printf("spf: SPF_set_helo_dom(\"%s\") failed.\n", spf_helo_domain);
  66     spf_server = NULL;
  67     spf_request = NULL;
  68     return 0;
  69   }
  70
  71   return 1;
  72 }
  73
  74
  75 /* spf_process adds the envelope sender address to the existing
  76    context (if any), retrieves the result, sets up expansion
  77    strings and evaluates the condition outcome. */
  78
  79 int spf_process(const uschar **listptr, uschar *spf_envelope_sender, int action) {
  80   int sep = 0;
  81   const uschar *list = *listptr;
  82   uschar *spf_result_id;
  83   uschar spf_result_id_buffer[128];
  84   int rc = SPF_RESULT_PERMERROR;
  85
  86   if (!(spf_server && spf_request)) {
  87     /* no global context, assume temp error and skip to evaluation */
  88     rc = SPF_RESULT_PERMERROR;
  89     goto SPF_EVALUATE;
  90   };
  91
  92   if (SPF_request_set_env_from(spf_request, CS spf_envelope_sender)) {
  93     /* Invalid sender address. This should be a real rare occurence */
  94     rc = SPF_RESULT_PERMERROR;
  95     goto SPF_EVALUATE;
  96   }
  97
  98   /* get SPF result */
  99   if (action == SPF_PROCESS_FALLBACK)
 100     SPF_request_query_fallback(spf_request, &spf_response, CS spf_guess);
 101   else
 102     SPF_request_query_mailfrom(spf_request, &spf_response);
 103
 104   /* set up expansion items */
 105   spf_header_comment     = (uschar *)SPF_response_get_header_comment(spf_response);
 106   spf_received           = (uschar *)SPF_response_get_received_spf(spf_response);
 107   spf_result             = (uschar *)SPF_strresult(SPF_response_result(spf_response));
 108   spf_smtp_comment       = (uschar *)SPF_response_get_smtp_comment(spf_response);
 109
 110   rc = SPF_response_result(spf_response);
 111
 112   /* We got a result. Now see if we should return OK or FAIL for it */
 113   SPF_EVALUATE:
 114   debug_printf("SPF result is %s (%d)\n", SPF_strresult(rc), rc);
 115
 116   if (action == SPF_PROCESS_GUESS && (!strcmp (SPF_strresult(rc), "none")))
 117     return spf_process(listptr, spf_envelope_sender, SPF_PROCESS_FALLBACK);
 118
 119   while ((spf_result_id = string_nextinlist(&list, &sep,
 120                                      spf_result_id_buffer,
 121                                      sizeof(spf_result_id_buffer))) != NULL) {
 122     int negate = 0;
 123     int result = 0;
 124
 125     /* Check for negation */
 126     if (spf_result_id[0] == '!') {
 127       negate = 1;
 128       spf_result_id++;
 129     };
 130
 131     /* Check the result identifier */
 132     result = Ustrcmp(spf_result_id, spf_result_id_list[rc].name);
 133     if (!negate && result==0) return OK;
 134     if (negate && result!=0) return OK;
 135   };
 136
 137   /* no match */
 138   return FAIL;
 139 }
 140
 141 #endif