dane.c

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/*
 * Verify or create TLS authentication with DANE (RFC6698)
 *
 * (c) NLnetLabs 2012-2020
 *
 * See the file LICENSE for the license.
 *
 */
 
#include <ldns/config.h>
#ifdef USE_DANE
 
#include <ldns/ldns.h>
#include <ldns/dane.h>
 
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
 
#ifdef HAVE_SSL
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/x509v3.h>
#endif
 
/* OpenSSL context options. At the moment, disable SSLv2, SSLv3
 * and Compression, if available. TLSv1.0 is allowed at the moment.
 * TLSv1.1 is the first to provide elliptic curves, so it is usually
 * allowed in a TLS stack. TLSv1.2 is the first to provide authentication
 * modes of operation, like GCM. The defines below are a moving
 * target based on OpenSSL library version. Grep is useful to find
 * the defines: grep -IR SSL_OP_NO_ /usr/include/openssl.
 */
#ifdef HAVE_SSL
# ifdef SSL_OP_NO_SSLv2
        const long NoOpenSSLv2 = SSL_OP_NO_SSLv2;
# else
        const long NoOpenSSLv2 = 0L;
# endif
# ifdef SSL_OP_NO_SSLv3
        const long NoOpenSSLv3 = SSL_OP_NO_SSLv3;
# else
        const long NoOpenSSLv3 = 0L;
# endif
# ifdef SSL_OP_NO_TLSv1
        const long NoOpenTLSv1 = SSL_OP_NO_TLSv1;
# else
        const long NoOpenTLSv1 = 0L;
# endif
# ifdef SSL_OP_NO_DTLSv1
        const long NoOpenDTLSv1 = SSL_OP_NO_DTLSv1;
# else
        const long NoOpenDTLSv1 = 0L;
# endif
# ifdef SSL_OP_NO_COMPRESSION
        const long NoOpenSSLCompression = SSL_OP_NO_COMPRESSION;
# else
        const long NoOpenSSLCompression = 0L;
# endif
#endif
 
#if defined(USE_DANE_VERIFY) && defined(USE_DANE_TA_USAGE)
static SSL_CTX*
ldns_dane_new_ssl_context(void)
{
        SSL_CTX* ssl_ctx;
 
        ssl_ctx = SSL_CTX_new(TLS_client_method());
        if (ssl_ctx != NULL)
        {
                /* ldns allows TLS and DTLS v1.0 at the moment. Some may disagree.
                 * Sometime in the future they may be disabled, too. Maybe
                 * --disable-tlsv1 and --disable-dtlsv1 should be configure options.
                 */
                long flags = NoOpenSSLv2 | NoOpenSSLv3 | NoOpenSSLCompression;
                SSL_CTX_set_options(ssl_ctx, flags);
        }
 
        return ssl_ctx;
}
#endif
 
ldns_status
ldns_dane_create_tlsa_owner(ldns_rdf** tlsa_owner, const ldns_rdf* name,
                uint16_t port, ldns_dane_transport transport)
{
        char buf[LDNS_MAX_DOMAINLEN];
        size_t s;
 
        assert(tlsa_owner != NULL);
        assert(name != NULL);
        assert(ldns_rdf_get_type(name) == LDNS_RDF_TYPE_DNAME);
 
        s = (size_t)snprintf(buf, LDNS_MAX_DOMAINLEN, "X_%d", (int)port);
        buf[0] = (char)(s - 1);
 
        switch(transport) {
        case LDNS_DANE_TRANSPORT_TCP:
                s += snprintf(buf + s, LDNS_MAX_DOMAINLEN - s, "\004_tcp");
                break;
        
        case LDNS_DANE_TRANSPORT_UDP:
                s += snprintf(buf + s, LDNS_MAX_DOMAINLEN - s, "\004_udp");
                break;
 
        case LDNS_DANE_TRANSPORT_SCTP:
                s += snprintf(buf + s, LDNS_MAX_DOMAINLEN - s, "\005_sctp");
                break;
        
        default:
                return LDNS_STATUS_DANE_UNKNOWN_TRANSPORT;
        }
        if (s + ldns_rdf_size(name) > LDNS_MAX_DOMAINLEN) {
                return LDNS_STATUS_DOMAINNAME_OVERFLOW;
        }
        memcpy(buf + s, ldns_rdf_data(name), ldns_rdf_size(name));
        *tlsa_owner = ldns_rdf_new_frm_data(LDNS_RDF_TYPE_DNAME,
                        s + ldns_rdf_size(name), buf);
        if (*tlsa_owner == NULL) {
                return LDNS_STATUS_MEM_ERR;
        }
        return LDNS_STATUS_OK;
}
 
 
#ifdef HAVE_SSL
ldns_status
ldns_dane_cert2rdf(ldns_rdf** rdf, X509* cert,
                ldns_tlsa_selector      selector,
                ldns_tlsa_matching_type matching_type)
{
        unsigned char* buf = NULL;
        size_t len;
 
        X509_PUBKEY* xpubkey;
        EVP_PKEY* epubkey;
 
        unsigned char* digest;
 
        assert(rdf != NULL);
        assert(cert != NULL);
 
        switch(selector) {
        case LDNS_TLSA_SELECTOR_FULL_CERTIFICATE:
 
                len = (size_t)i2d_X509(cert, &buf);
                break;
 
        case LDNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO:
 
#ifndef S_SPLINT_S
                xpubkey = X509_get_X509_PUBKEY(cert);
#endif
                if (! xpubkey) {
                        return LDNS_STATUS_SSL_ERR;
                }
                epubkey = X509_PUBKEY_get(xpubkey);
                if (! epubkey) {
                        return LDNS_STATUS_SSL_ERR;
                }
                len = (size_t)i2d_PUBKEY(epubkey, &buf);
                break;
        
        default:
                return LDNS_STATUS_DANE_UNKNOWN_SELECTOR;
        }
 
        switch(matching_type) {
        case LDNS_TLSA_MATCHING_TYPE_NO_HASH_USED:
 
                *rdf = ldns_rdf_new(LDNS_RDF_TYPE_HEX, len, buf);
                
                return *rdf ? LDNS_STATUS_OK : LDNS_STATUS_MEM_ERR;
                break;
        
        case LDNS_TLSA_MATCHING_TYPE_SHA256:
 
                digest = LDNS_XMALLOC(unsigned char, LDNS_SHA256_DIGEST_LENGTH);
                if (digest == NULL) {
                        LDNS_FREE(buf);
                        return LDNS_STATUS_MEM_ERR;
                }
                (void) ldns_sha256(buf, (unsigned int)len, digest);
                *rdf = ldns_rdf_new(LDNS_RDF_TYPE_HEX, LDNS_SHA256_DIGEST_LENGTH,
                                digest);
                LDNS_FREE(buf);
 
                return *rdf ? LDNS_STATUS_OK : LDNS_STATUS_MEM_ERR;
                break;
 
        case LDNS_TLSA_MATCHING_TYPE_SHA512:
 
                digest = LDNS_XMALLOC(unsigned char, LDNS_SHA512_DIGEST_LENGTH);
                if (digest == NULL) {
                        LDNS_FREE(buf);
                        return LDNS_STATUS_MEM_ERR;
                }
                (void) ldns_sha512(buf, (unsigned int)len, digest);
                *rdf = ldns_rdf_new(LDNS_RDF_TYPE_HEX, LDNS_SHA512_DIGEST_LENGTH,
                                digest);
                LDNS_FREE(buf);
 
                return *rdf ? LDNS_STATUS_OK : LDNS_STATUS_MEM_ERR;
                break;
        
        default:
                LDNS_FREE(buf);
                return LDNS_STATUS_DANE_UNKNOWN_MATCHING_TYPE;
        }
}
 
 
/* Ordinary PKIX validation of cert (with extra_certs to help)
 * against the CA's in store
 */
static ldns_status
ldns_dane_pkix_validate(X509* cert, STACK_OF(X509)* extra_certs,
                X509_STORE* store)
{
        X509_STORE_CTX* vrfy_ctx;
        ldns_status s;
 
        if (! store) {
                return LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
        }
        vrfy_ctx = X509_STORE_CTX_new();
        if (! vrfy_ctx) {
 
                return LDNS_STATUS_SSL_ERR;
 
        } else if (X509_STORE_CTX_init(vrfy_ctx, store,
                                cert, extra_certs) != 1) {
                s = LDNS_STATUS_SSL_ERR;
 
        } else if (X509_verify_cert(vrfy_ctx) == 1) {
 
                s = LDNS_STATUS_OK;
 
        } else {
                s = LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
        }
        X509_STORE_CTX_free(vrfy_ctx);
        return s;
}
 
 
/* Ordinary PKIX validation of cert (with extra_certs to help)
 * against the CA's in store, but also return the validation chain.
 */
static ldns_status
ldns_dane_pkix_validate_and_get_chain(STACK_OF(X509)** chain, X509* cert,
                STACK_OF(X509)* extra_certs, X509_STORE* store)
{
        ldns_status s;
        X509_STORE* empty_store = NULL;
        X509_STORE_CTX* vrfy_ctx;
 
        assert(chain != NULL);
 
        if (! store) {
                store = empty_store = X509_STORE_new();
        }
        s = LDNS_STATUS_SSL_ERR;
        vrfy_ctx = X509_STORE_CTX_new();
        if (! vrfy_ctx) {
 
                goto exit_free_empty_store;
 
        } else if (X509_STORE_CTX_init(vrfy_ctx, store,
                                        cert, extra_certs) != 1) {
                goto exit_free_vrfy_ctx;
 
        } else if (X509_verify_cert(vrfy_ctx) == 1) {
 
                s = LDNS_STATUS_OK;
 
        } else {
                s = LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
        }
        *chain = X509_STORE_CTX_get1_chain(vrfy_ctx);
        if (! *chain) {
                s = LDNS_STATUS_SSL_ERR;
        }
 
exit_free_vrfy_ctx:
        X509_STORE_CTX_free(vrfy_ctx);
 
exit_free_empty_store:
        if (empty_store) {
                X509_STORE_free(empty_store);
        }
        return s;
}
 
 
/* Return the validation chain that can be build out of cert, with extra_certs.
 */
static ldns_status
ldns_dane_pkix_get_chain(STACK_OF(X509)** chain,
                X509* cert, STACK_OF(X509)* extra_certs)
{
        ldns_status s;
        X509_STORE* empty_store = NULL;
        X509_STORE_CTX* vrfy_ctx;
 
        assert(chain != NULL);
 
        empty_store = X509_STORE_new();
        s = LDNS_STATUS_SSL_ERR;
        vrfy_ctx = X509_STORE_CTX_new();
        if (! vrfy_ctx) {
 
                goto exit_free_empty_store;
 
        } else if (X509_STORE_CTX_init(vrfy_ctx, empty_store,
                                        cert, extra_certs) != 1) {
                goto exit_free_vrfy_ctx;
        }
        (void) X509_verify_cert(vrfy_ctx);
        *chain = X509_STORE_CTX_get1_chain(vrfy_ctx);
        if (! *chain) {
                s = LDNS_STATUS_SSL_ERR;
        } else {
                s = LDNS_STATUS_OK;
        }
exit_free_vrfy_ctx:
        X509_STORE_CTX_free(vrfy_ctx);
 
exit_free_empty_store:
        X509_STORE_free(empty_store);
        return s;
}
 
 
/* Pop n+1 certs and return the last popped.
 */
static ldns_status
ldns_dane_get_nth_cert_from_validation_chain(
                X509** cert, STACK_OF(X509)* chain, int n, bool ca)
{
        if (n >= sk_X509_num(chain) || n < 0) {
                return LDNS_STATUS_DANE_OFFSET_OUT_OF_RANGE;
        }
        *cert = sk_X509_pop(chain);
        while (n-- > 0) {
                X509_free(*cert);
                *cert = sk_X509_pop(chain);
        }
        if (ca && ! X509_check_ca(*cert)) {
                return LDNS_STATUS_DANE_NON_CA_CERTIFICATE;
        }
        return LDNS_STATUS_OK;
}
 
 
/* Create validation chain with cert and extra_certs and returns the last
 * self-signed (if present).
 */
static ldns_status
ldns_dane_pkix_get_last_self_signed(X509** out_cert,
                X509* cert, STACK_OF(X509)* extra_certs)
{
        ldns_status s;
        X509_STORE* empty_store = NULL;
        X509_STORE_CTX* vrfy_ctx;
 
        assert(out_cert != NULL);
 
        empty_store = X509_STORE_new();
        s = LDNS_STATUS_SSL_ERR;
        vrfy_ctx = X509_STORE_CTX_new();
        if (! vrfy_ctx) {
                goto exit_free_empty_store;
 
        } else if (X509_STORE_CTX_init(vrfy_ctx, empty_store,
                                        cert, extra_certs) != 1) {
                goto exit_free_vrfy_ctx;
 
        }
        (void) X509_verify_cert(vrfy_ctx);
        if (X509_STORE_CTX_get_error(vrfy_ctx) == X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN ||
            X509_STORE_CTX_get_error(vrfy_ctx) == X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT){
 
                *out_cert = X509_STORE_CTX_get_current_cert( vrfy_ctx);
                s = LDNS_STATUS_OK;
        } else {
                s = LDNS_STATUS_DANE_PKIX_NO_SELF_SIGNED_TRUST_ANCHOR;
        }
exit_free_vrfy_ctx:
        X509_STORE_CTX_free(vrfy_ctx);
 
exit_free_empty_store:
        X509_STORE_free(empty_store);
        return s;
}
 
 
ldns_status
ldns_dane_select_certificate(X509** selected_cert,
                X509* cert, STACK_OF(X509)* extra_certs,
                X509_STORE* pkix_validation_store,
                ldns_tlsa_certificate_usage cert_usage, int offset)
{
        ldns_status s;
        STACK_OF(X509)* pkix_validation_chain = NULL;
 
        assert(selected_cert != NULL);
        assert(cert != NULL);
 
        /* With PKIX validation explicitly turned off (pkix_validation_store
         *  == NULL), treat the "CA constraint" and "Service certificate
         * constraint" the same as "Trust anchor assertion" and "Domain issued
         * certificate" respectively.
         */
        if (pkix_validation_store == NULL) {
                switch (cert_usage) {
 
                case LDNS_TLSA_USAGE_CA_CONSTRAINT:
 
                        cert_usage = LDNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION;
                        break;
 
                case LDNS_TLSA_USAGE_SERVICE_CERTIFICATE_CONSTRAINT:
 
                        cert_usage = LDNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE;
                        break;
 
                default:
                        break;
                }
        }
 
        /* Now what to do with each Certificate usage...
         */
        switch (cert_usage) {
 
        case LDNS_TLSA_USAGE_CA_CONSTRAINT:
 
                s = ldns_dane_pkix_validate_and_get_chain(
                                &pkix_validation_chain,
                                cert, extra_certs,
                                pkix_validation_store);
                if (! pkix_validation_chain) {
                        return s;
                }
                if (s == LDNS_STATUS_OK) {
                        if (offset == -1) {
                                offset = 0;
                        }
                        s = ldns_dane_get_nth_cert_from_validation_chain(
                                        selected_cert, pkix_validation_chain,
                                        offset, true);
                }
                sk_X509_pop_free(pkix_validation_chain, X509_free);
                return s;
                break;
 
 
        case LDNS_TLSA_USAGE_SERVICE_CERTIFICATE_CONSTRAINT:
 
                *selected_cert = cert;
                return ldns_dane_pkix_validate(cert, extra_certs,
                                pkix_validation_store);
                break;
 
 
        case LDNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION:
 
                if (offset == -1) {
                        s = ldns_dane_pkix_get_last_self_signed(
                                        selected_cert, cert, extra_certs);
                        return s;
                } else {
                        s = ldns_dane_pkix_get_chain(
                                        &pkix_validation_chain,
                                        cert, extra_certs);
                        if (s == LDNS_STATUS_OK) {
                                s =
                                ldns_dane_get_nth_cert_from_validation_chain(
                                        selected_cert, pkix_validation_chain,
                                        offset, false);
                        } else if (! pkix_validation_chain) {
                                return s;
                        }
                        sk_X509_pop_free(pkix_validation_chain, X509_free);
                        return s;
                }
                break;
 
 
        case LDNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE:
 
                *selected_cert = cert;
                return LDNS_STATUS_OK;
                break;
        
        default:
                return LDNS_STATUS_DANE_UNKNOWN_CERTIFICATE_USAGE;
                break;
        }
}
 
 
ldns_status
ldns_dane_create_tlsa_rr(ldns_rr** tlsa,
                ldns_tlsa_certificate_usage certificate_usage,
                ldns_tlsa_selector          selector,
                ldns_tlsa_matching_type     matching_type,
                X509* cert)
{
        ldns_rdf* rdf;
        ldns_status s;
 
        assert(tlsa != NULL);
        assert(cert != NULL);
 
        /* create rr */
        *tlsa = ldns_rr_new_frm_type(LDNS_RR_TYPE_TLSA);
        if (*tlsa == NULL) {
                return LDNS_STATUS_MEM_ERR;
        }
 
        rdf = ldns_native2rdf_int8(LDNS_RDF_TYPE_INT8,
                        (uint8_t)certificate_usage);
        if (rdf == NULL) {
                goto memerror;
        }
        (void) ldns_rr_set_rdf(*tlsa, rdf, 0);
 
        rdf = ldns_native2rdf_int8(LDNS_RDF_TYPE_INT8, (uint8_t)selector);
        if (rdf == NULL) {
                goto memerror;
        }
        (void) ldns_rr_set_rdf(*tlsa, rdf, 1);
 
        rdf = ldns_native2rdf_int8(LDNS_RDF_TYPE_INT8, (uint8_t)matching_type);
        if (rdf == NULL) {
                goto memerror;
        }
        (void) ldns_rr_set_rdf(*tlsa, rdf, 2);
 
        s = ldns_dane_cert2rdf(&rdf, cert, selector, matching_type);
        if (s == LDNS_STATUS_OK) {
                (void) ldns_rr_set_rdf(*tlsa, rdf, 3);
                return LDNS_STATUS_OK;
        }
        ldns_rr_free(*tlsa);
        *tlsa = NULL;
        return s;
 
memerror:
        ldns_rr_free(*tlsa);
        *tlsa = NULL;
        return LDNS_STATUS_MEM_ERR;
}
 
 
#ifdef USE_DANE_VERIFY
/* Return tlsas that actually are TLSA resource records with known values
 * for the Certificate usage, Selector and Matching type rdata fields.
 */
static ldns_rr_list*
ldns_dane_filter_unusable_records(const ldns_rr_list* tlsas)
{
        size_t i;
        ldns_rr_list* r = ldns_rr_list_new();
        ldns_rr* tlsa_rr;
 
        if (! r) {
                return NULL;
        }
        for (i = 0; i < ldns_rr_list_rr_count(tlsas); i++) {
                tlsa_rr = ldns_rr_list_rr(tlsas, i);
                if (ldns_rr_get_type(tlsa_rr) == LDNS_RR_TYPE_TLSA &&
                    ldns_rr_rd_count(tlsa_rr) == 4 &&
                    ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 0)) <= 3 &&
                    ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 1)) <= 1 &&
                    ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 2)) <= 2) {
 
                        if (! ldns_rr_list_push_rr(r, tlsa_rr)) {
                                ldns_rr_list_free(r);
                                return NULL;
                        }
                }
        }
        return r;
}
 
 
#if !defined(USE_DANE_TA_USAGE)
/* Return whether cert/selector/matching_type matches data.
 */
static ldns_status
ldns_dane_match_cert_with_data(X509* cert, ldns_tlsa_selector selector,
                ldns_tlsa_matching_type matching_type, ldns_rdf* data)
{
        ldns_status s;
        ldns_rdf* match_data;
 
        s = ldns_dane_cert2rdf(&match_data, cert, selector, matching_type);
        if (s == LDNS_STATUS_OK) {
                if (ldns_rdf_compare(data, match_data) != 0) {
                        s = LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH;
                }
                ldns_rdf_free(match_data);
        }
        return s;
}
 
 
/* Return whether any certificate from the chain with selector/matching_type
 * matches data.
 * ca should be true if the certificate has to be a CA certificate too.
 */
static ldns_status
ldns_dane_match_any_cert_with_data(STACK_OF(X509)* chain,
                ldns_tlsa_selector      selector,
                ldns_tlsa_matching_type matching_type,
                ldns_rdf* data, bool ca)
{
        ldns_status s = LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH;
        size_t n, i;
        X509* cert;
 
        n = (size_t)sk_X509_num(chain);
        for (i = 0; i < n; i++) {
                cert = sk_X509_pop(chain);
                if (! cert) {
                        s = LDNS_STATUS_SSL_ERR;
                        break;
                }
                s = ldns_dane_match_cert_with_data(cert,
                                selector, matching_type, data);
                if (ca && s == LDNS_STATUS_OK && ! X509_check_ca(cert)) {
                        s = LDNS_STATUS_DANE_NON_CA_CERTIFICATE;
                }
                X509_free(cert);
                if (s != LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH) {
                        break;
                }
                /* when s == LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH,
                 * try to match the next certificate
                 */
        }
        return s;
}
#endif /* !defined(USE_DANE_TA_USAGE) */
#endif /* USE_DANE_VERIFY */
 
#ifdef USE_DANE_VERIFY
ldns_status
ldns_dane_verify_rr(const ldns_rr* tlsa_rr,
                X509* cert, STACK_OF(X509)* extra_certs,
                X509_STORE* pkix_validation_store)
{
#if defined(USE_DANE_TA_USAGE)
        SSL_CTX *ssl_ctx = NULL;
        SSL *ssl = NULL;
        X509_STORE_CTX *store_ctx = NULL;
#else
        STACK_OF(X509)* pkix_validation_chain = NULL;
#endif
        ldns_status s = LDNS_STATUS_OK;
 
        ldns_tlsa_certificate_usage usage;
        ldns_tlsa_selector          selector;
        ldns_tlsa_matching_type     mtype;
        ldns_rdf*                   data;
 
        if (! tlsa_rr || ldns_rr_get_type(tlsa_rr) != LDNS_RR_TYPE_TLSA ||
                        ldns_rr_rd_count(tlsa_rr) != 4 ||
                        ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 0)) > 3 ||
                        ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 1)) > 1 ||
                        ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 2)) > 2 ) {
                /* No (usable) TLSA, so regular PKIX validation
                 */
                return ldns_dane_pkix_validate(cert, extra_certs,
                                pkix_validation_store);
        }
        usage    = ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 0));
        selector = ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 1));
        mtype    = ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr, 2));
        data     =                      ldns_rr_rdf(tlsa_rr, 3) ;
 
#if defined(USE_DANE_TA_USAGE)
        /* Rely on OpenSSL dane functions.
         *
         * OpenSSL does not provide offline dane verification.  The dane unit
         * tests within openssl use the undocumented SSL_get0_dane() and 
         * X509_STORE_CTX_set0_dane() to convey dane parameters set on SSL and
         * SSL_CTX to a X509_STORE_CTX that can be used to do offline
         * verification.  We use these undocumented means with the ldns
         * dane function prototypes which did only offline dane verification.
         */
        if (!(ssl_ctx = ldns_dane_new_ssl_context()))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (SSL_CTX_dane_enable(ssl_ctx) <= 0)
                s = LDNS_STATUS_SSL_ERR;
 
        else if (SSL_CTX_dane_set_flags(
                                ssl_ctx, DANE_FLAG_NO_DANE_EE_NAMECHECKS),
                        !(ssl = SSL_new(ssl_ctx)))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (SSL_set_connect_state(ssl),
                        (SSL_dane_enable(ssl, NULL) <= 0))
                s = LDNS_STATUS_SSL_ERR;
 
        else if (SSL_dane_tlsa_add(ssl, usage, selector, mtype,
                                ldns_rdf_data(data), ldns_rdf_size(data)) <= 0)
                s = LDNS_STATUS_SSL_ERR;
 
        else if (!(store_ctx =  X509_STORE_CTX_new()))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (!X509_STORE_CTX_init(store_ctx, pkix_validation_store, cert, extra_certs))
                s = LDNS_STATUS_SSL_ERR;
 
        else {
                int ret;
 
                X509_STORE_CTX_set_default(store_ctx,
                                SSL_is_server(ssl) ? "ssl_client" : "ssl_server");
                X509_VERIFY_PARAM_set1(X509_STORE_CTX_get0_param(store_ctx),
                                SSL_get0_param(ssl));
                X509_STORE_CTX_set0_dane(store_ctx, SSL_get0_dane(ssl));
                if (SSL_get_verify_callback(ssl))
                        X509_STORE_CTX_set_verify_cb(store_ctx, SSL_get_verify_callback(ssl));
 
                ret = X509_verify_cert(store_ctx);
                if (!ret) {
                        if (X509_STORE_CTX_get_error(store_ctx) == X509_V_ERR_DANE_NO_MATCH)
                                s = LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH;
                        else
                                s = LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
                }
                X509_STORE_CTX_cleanup(store_ctx);
        }
        if (store_ctx)
                X509_STORE_CTX_free(store_ctx);
        if (ssl)
                SSL_free(ssl);
        if (ssl_ctx)
                SSL_CTX_free(ssl_ctx);
        return s;
#else
        switch (usage) {
        case LDNS_TLSA_USAGE_CA_CONSTRAINT:
                s = ldns_dane_pkix_validate_and_get_chain(
                                &pkix_validation_chain, 
                                cert, extra_certs,
                                pkix_validation_store);
                if (! pkix_validation_chain) {
                        return s;
                }
                if (s == LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE) {
                        /*
                         * NO PKIX validation. We still try to match *any*
                         * certificate from the chain, so we return
                         * TLSA errors over PKIX errors.
                         *
                         * i.e. When the TLSA matches no certificate, we return
                         * TLSA_DID_NOT_MATCH and not PKIX_DID_NOT_VALIDATE
                         */
                        s = ldns_dane_match_any_cert_with_data(
                                        pkix_validation_chain,
                                        selector, mtype, data, true);
 
                        if (s == LDNS_STATUS_OK) {
                                /* A TLSA record did match a cert from the
                                 * chain, thus the error is failed PKIX
                                 * validation.
                                 */
                                s = LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
                        }
 
                } else if (s == LDNS_STATUS_OK) { 
                        /* PKIX validated, does the TLSA match too? */
 
                        s = ldns_dane_match_any_cert_with_data(
                                        pkix_validation_chain,
                                        selector, mtype, data, true);
                }
                sk_X509_pop_free(pkix_validation_chain, X509_free);
                return s;
                break;
 
        case LDNS_TLSA_USAGE_SERVICE_CERTIFICATE_CONSTRAINT:
 
                s = ldns_dane_match_cert_with_data(cert,
                                selector, mtype, data);
 
                if (s == LDNS_STATUS_OK) {
                        return ldns_dane_pkix_validate(cert, extra_certs,
                                        pkix_validation_store);
                }
                return s;
                break;
 
        case LDNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION:
#if 0
                s = ldns_dane_pkix_get_chain(&pkix_validation_chain,
                                cert, extra_certs);
 
                if (s == LDNS_STATUS_OK) {
                        s = ldns_dane_match_any_cert_with_data(
                                        pkix_validation_chain,
                                        selector, mtype, data, false);
 
                } else if (! pkix_validation_chain) {
                        return s;
                }
                sk_X509_pop_free(pkix_validation_chain, X509_free);
                return s;
#else
                return LDNS_STATUS_DANE_NEED_OPENSSL_GE_1_1_FOR_DANE_TA;
#endif
                break;
 
        case LDNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE:
                return ldns_dane_match_cert_with_data(cert,
                                selector, mtype, data);
                break;
 
        default:
                break;
        }
#endif
        return LDNS_STATUS_DANE_UNKNOWN_CERTIFICATE_USAGE;
}
 
 
ldns_status
ldns_dane_verify(const ldns_rr_list* tlsas,
                X509* cert, STACK_OF(X509)* extra_certs,
                X509_STORE* pkix_validation_store)
{
#if defined(USE_DANE_TA_USAGE)
        SSL_CTX *ssl_ctx = NULL;
        ldns_rdf *basename_rdf = NULL;
        char *basename = NULL;
        SSL *ssl = NULL;
        X509_STORE_CTX *store_ctx = NULL;
#else
        ldns_status ps;
#endif
        size_t i;
        ldns_rr* tlsa_rr;
        ldns_rr_list *usable_tlsas;
        ldns_status s = LDNS_STATUS_OK;
 
        assert(cert != NULL);
 
        if (! tlsas || ldns_rr_list_rr_count(tlsas) == 0)
                /* No TLSA's, so regular PKIX validation
                 */
                return ldns_dane_pkix_validate(cert, extra_certs,
                                pkix_validation_store);
 
/* To enable name checks (which we don't) */
#if defined(USE_DANE_TA_USAGE) && 0
        else if (!(basename_rdf = ldns_dname_clone_from(
                                        ldns_rr_list_owner(tlsas), 2)))
                /* Could nog get DANE base name */
                s = LDNS_STATUS_ERR;
 
        else if (!(basename = ldns_rdf2str(basename_rdf)))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (strlen(basename) && (basename[strlen(basename)-1]  = 0))
                s = LDNS_STATUS_ERR; /* Intended to be unreachable */
#endif
 
        else if (!(usable_tlsas = ldns_dane_filter_unusable_records(tlsas)))
                return LDNS_STATUS_MEM_ERR;
 
        else if (ldns_rr_list_rr_count(usable_tlsas) == 0) {
                /* No TLSA's, so regular PKIX validation
                 */
                ldns_rr_list_free(usable_tlsas);
                return ldns_dane_pkix_validate(cert, extra_certs,
                                pkix_validation_store);
        }
#if defined(USE_DANE_TA_USAGE)
        /* Rely on OpenSSL dane functions.
         *
         * OpenSSL does not provide offline dane verification.  The dane unit
         * tests within openssl use the undocumented SSL_get0_dane() and 
         * X509_STORE_CTX_set0_dane() to convey dane parameters set on SSL and
         * SSL_CTX to a X509_STORE_CTX that can be used to do offline
         * verification.  We use these undocumented means with the ldns
         * dane function prototypes which did only offline dane verification.
         */
        if (!(ssl_ctx = ldns_dane_new_ssl_context()))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (SSL_CTX_dane_enable(ssl_ctx) <= 0)
                s = LDNS_STATUS_SSL_ERR;
 
        else if (SSL_CTX_dane_set_flags(
                                ssl_ctx, DANE_FLAG_NO_DANE_EE_NAMECHECKS),
                        !(ssl = SSL_new(ssl_ctx)))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (SSL_set_connect_state(ssl),
                        (SSL_dane_enable(ssl, basename) <= 0))
                s = LDNS_STATUS_SSL_ERR;
 
        else for (i = 0; i < ldns_rr_list_rr_count(usable_tlsas); i++) {
                ldns_tlsa_certificate_usage usage;
                ldns_tlsa_selector          selector;
                ldns_tlsa_matching_type     mtype;
                ldns_rdf*                   data;
 
                tlsa_rr = ldns_rr_list_rr(usable_tlsas, i);
                usage   = ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr,0));
                selector= ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr,1));
                mtype   = ldns_rdf2native_int8(ldns_rr_rdf(tlsa_rr,2));
                data    =                      ldns_rr_rdf(tlsa_rr,3) ;
 
                if (SSL_dane_tlsa_add(ssl, usage, selector, mtype,
                                        ldns_rdf_data(data),
                                        ldns_rdf_size(data)) <= 0) {
                        s = LDNS_STATUS_SSL_ERR;
                        break;
                }
        }
        if (!s && !(store_ctx =  X509_STORE_CTX_new()))
                s = LDNS_STATUS_MEM_ERR;
 
        else if (!X509_STORE_CTX_init(store_ctx, pkix_validation_store, cert, extra_certs))
                s = LDNS_STATUS_SSL_ERR;
 
        else {
                int ret;
 
                X509_STORE_CTX_set_default(store_ctx,
                                SSL_is_server(ssl) ? "ssl_client" : "ssl_server");
                X509_VERIFY_PARAM_set1(X509_STORE_CTX_get0_param(store_ctx),
                                SSL_get0_param(ssl));
                X509_STORE_CTX_set0_dane(store_ctx, SSL_get0_dane(ssl));
                if (SSL_get_verify_callback(ssl))
                        X509_STORE_CTX_set_verify_cb(store_ctx, SSL_get_verify_callback(ssl));
 
                ret = X509_verify_cert(store_ctx);
                if (!ret) {
                        if (X509_STORE_CTX_get_error(store_ctx) == X509_V_ERR_DANE_NO_MATCH)
                                s = LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH;
                        else
                                s = LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE;
                }
                X509_STORE_CTX_cleanup(store_ctx);
        }
        if (store_ctx)
                X509_STORE_CTX_free(store_ctx);
        if (ssl)
                SSL_free(ssl);
        if (ssl_ctx)
                SSL_CTX_free(ssl_ctx);
        if (basename)
                free(basename);
        ldns_rdf_deep_free(basename_rdf);
#else
        for (i = 0; i < ldns_rr_list_rr_count(usable_tlsas); i++) {
                tlsa_rr = ldns_rr_list_rr(usable_tlsas, i);
                ps = s;
                s = ldns_dane_verify_rr(tlsa_rr, cert, extra_certs,
                                pkix_validation_store);
 
                if (s != LDNS_STATUS_DANE_TLSA_DID_NOT_MATCH &&
                    s != LDNS_STATUS_DANE_PKIX_DID_NOT_VALIDATE &&
                    s != LDNS_STATUS_DANE_NEED_OPENSSL_GE_1_1_FOR_DANE_TA) {
 
                        /* which would be LDNS_STATUS_OK (match)
                         * or some fatal error preventing use from
                         * trying the next TLSA record.
                         */
                        break;
                }
                s = (s > ps ? s : ps); /* pref NEED_OPENSSL_GE_1_1_FOR_DANE_TA
                                        * over PKIX_DID_NOT_VALIDATE
                                        * over TLSA_DID_NOT_MATCH
                                        */
        }
#endif
        ldns_rr_list_free(usable_tlsas);
        return s;
}
#endif /* USE_DANE_VERIFY */
#endif /* HAVE_SSL */
#endif /* USE_DANE */