spf_get_exp.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of either:
 *
 *   a) The GNU Lesser General Public License as published by the Free
 *        Software Foundation; either version 2.1, or (at your option) any
 *        later version,
 *
 *   OR
 *
 *   b) The two-clause BSD license.
 *
 * These licenses can be found with the distribution in the file LICENSES
 */

#include "spf_sys_config.h"

#ifdef STDC_HEADERS
# include <stdlib.h>       /* malloc / free */
# include <stdio.h>             /* stdin / stdout */
#endif

#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif

#ifdef HAVE_STRING_H
# include <string.h>       /* strstr / strdup */
#else
# ifdef HAVE_STRINGS_H
#  include <strings.h>       /* strstr / strdup */
# endif
#endif


#include "spf.h"
#include "spf_dns.h"
#include "spf_internal.h"
#include "spf_dns_internal.h"


        /* This never happens. We get SPF_DEFAULT_EXP instead.
         * This is a panic response which must not contain macros. */
#define SPF_LAME_EXP    "SPF failure: no explanation available"

static SPF_errcode_t
SPF_server_get_default_explanation(SPF_server_t *spf_server,
                                                SPF_request_t *spf_request,
                                                SPF_response_t *spf_response,
                                                char **bufp, size_t *buflenp)
{
        SPF_errcode_t            err;
        SPF_macro_t                     *spf_macro;

        spf_macro = spf_server->explanation;
        if (spf_macro != NULL) {
                err = SPF_record_expand_data(spf_server,
                                                spf_request, spf_response,
                                                SPF_macro_data(spf_macro), spf_macro->macro_len,
                                                bufp, buflenp);
                return err;
        }
        else {
                size_t  len = sizeof(SPF_LAME_EXP) + 1;
                if (*buflenp < len) {
                        char    *tmp = realloc(*bufp, len);
                        if (tmp == NULL)
                                return SPF_E_NO_MEMORY;
                        *bufp = tmp;
                        *buflenp = len;
                }
                strcpy(*bufp, SPF_LAME_EXP);
                return SPF_E_SUCCESS;
        }
}

#define RETURN_DEFAULT_EXP() do { \
                return SPF_server_get_default_explanation(spf_server, \
                                                spf_request, spf_response, bufp, buflenp); \
                                } while(0)

SPF_errcode_t
SPF_request_get_exp(SPF_server_t *spf_server,
                                                SPF_request_t *spf_request,
                                                SPF_response_t *spf_response,
                                                SPF_record_t *spf_record,
                                                char **bufp, size_t *buflenp)
{
        SPF_macro_t                     *spf_macro;
        SPF_dns_server_t        *resolver;
        SPF_dns_rr_t            *rr_txt;
        SPF_errcode_t            err;
        const char                      *domain;


        /*
         * There are lots of places to look for the explanation message,
         * some require DNS lookups, some don't.
         */

        SPF_ASSERT_NOTNULL(spf_server);
        SPF_ASSERT_NOTNULL(spf_request);
        SPF_ASSERT_NOTNULL(spf_response);
        SPF_ASSERT_NOTNULL(spf_record);
        SPF_ASSERT_NOTNULL(bufp);
        SPF_ASSERT_NOTNULL(buflenp);

        domain = spf_request->cur_dom;

        if ( domain == NULL )
                return SPF_response_add_warn(spf_response, SPF_E_NOT_CONFIG,
                                "Could not identify current domain for explanation");

        /*
         * start looking...  check spfid for exp-text=
         */

        err = SPF_record_find_mod_value(spf_server, spf_request,
                                        spf_response, spf_record,
                                        SPF_EXP_MOD_NAME, bufp, buflenp);
        if (err == SPF_E_SUCCESS)
                return err;


        /*
         * still looking...  check the spfid for exp=
         */

        err = SPF_record_find_mod_value(spf_server, spf_request,
                                        spf_response, spf_record,
                                        "exp", bufp, buflenp );
        if (err != SPF_E_SUCCESS) {
                /*
                 * still looking...  try to return default exp from spfcid
                 */
                RETURN_DEFAULT_EXP();
        }

        if (*bufp == NULL  ||  (*bufp)[0] == '\0') {
                /*
                 * still looking...  try to return default exp from spfcid
                 */
                SPF_response_add_warn(spf_response, SPF_E_NOT_SPF,
                                                "Explanation is blank!");
                RETURN_DEFAULT_EXP();
        }


        /*
         * still looking...  try doing a DNS lookup on the exp= name
         */

        resolver = spf_server->resolver;

        if (resolver->get_exp)
                return resolver->get_exp(spf_server, *bufp, bufp, buflenp);

        rr_txt = SPF_dns_lookup(resolver, *bufp, ns_t_txt, TRUE);
        if (rr_txt == NULL) {
                SPF_dns_rr_free(rr_txt);
                RETURN_DEFAULT_EXP();
        }

        switch (rr_txt->herrno) {
                case HOST_NOT_FOUND:
                case NO_DATA:
                        SPF_dns_rr_free(rr_txt);
                        RETURN_DEFAULT_EXP();
                        break;

                case TRY_AGAIN:
                        SPF_dns_rr_free(rr_txt);
                        RETURN_DEFAULT_EXP();
                        break;

                case NETDB_SUCCESS:
                        break;

                default:
                        SPF_warning("Unknown DNS lookup error code");
                        SPF_dns_rr_free(rr_txt);
                        RETURN_DEFAULT_EXP();
                        break;
        }

        if (rr_txt->num_rr == 0) {
                SPF_response_add_warn(spf_response, SPF_E_NOT_SPF,
                                "No TXT records returned from DNS lookup");
                RETURN_DEFAULT_EXP();
        }


        /*
         * still looking...  try compiling this TXT record
         */

        /* FIXME  we are supposed to concatenate the TXT records */

        /* FIXME: If this generates any errors, demote them to warnings. */
        spf_macro = NULL;
        err = SPF_record_compile_macro(spf_server, spf_response, &spf_macro,
                                                                rr_txt->rr[0]->txt);
        if (err != SPF_E_SUCCESS) {
                if (spf_macro)
                        SPF_macro_free(spf_macro);
                SPF_dns_rr_free(rr_txt);
                RETURN_DEFAULT_EXP();
        }

        err = SPF_record_expand_data(spf_server,
                                        spf_request, spf_response,
                                        SPF_macro_data(spf_macro), spf_macro->macro_len,
                                        bufp, buflenp);
        SPF_macro_free(spf_macro);
        SPF_dns_rr_free(rr_txt);

        return err;
}

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