ctx.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: d08c0168ba1b6ca426e8b73f6413b16670058c93 $
 *
 * @file tls/ctx.c
 * @brief Initialise and configure SSL_CTX structures.
 *
 * @copyright 2001 hereUare Communications, Inc. (raghud@hereuare.com)
 * @copyright 2003 Alan DeKok (aland@freeradius.org)
 * @copyright 2006-2016 The FreeRADIUS server project
 */
RCSID("$Id: d08c0168ba1b6ca426e8b73f6413b16670058c93 $")
USES_APPLE_DEPRECATED_API       /* OpenSSL API has been deprecated by Apple */
 
#ifdef WITH_TLS
#define LOG_PREFIX "tls"
 
#include <freeradius-devel/tls/log.h>
#include <freeradius-devel/tls/strerror.h>
#include <freeradius-devel/util/base16.h>
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/misc.h>
#include <freeradius-devel/util/strerror.h>
#include <freeradius-devel/util/syserror.h>
 
#include "base.h"
#include "utils.h"
#include "log.h"
#include "cert.h"
 
#include <openssl/rand.h>
#include <openssl/dh.h>
#include <openssl/x509v3.h>
#include <openssl/provider.h>
 
#ifndef OPENSSL_NO_ECDH
static int ctx_ecdh_curve_set(SSL_CTX *ctx, char const *ecdh_curve, bool disable_single_dh_use)
{
        char *list;
 
        if (!disable_single_dh_use) {
                SSL_CTX_set_options(ctx, SSL_OP_SINGLE_ECDH_USE);
        }
 
        if (!ecdh_curve || !*ecdh_curve) return 0;
 
        list = strdup(ecdh_curve);
        if (SSL_CTX_set1_curves_list(ctx, list) == 0) {
                free(list);
                ERROR("Unknown ecdh_curve \"%s\"", ecdh_curve);
                return -1;
        }
        free(list);
        return 0;
}
#endif
 
/*
 *      TODO: Check for the type of key exchange * like conf->dh_key
 */
static int ctx_dh_params_load(SSL_CTX *ctx, char *file)
{
        BIO     *bio;
        int     ret;
 
        EVP_PKEY *dh = NULL;
 
        if (!file) return 0;
 
        /*
         * Prior to trying to load the file, check what OpenSSL will do with it.
         *
         * Certain downstreams (such as RHEL) will ignore user-provided dhparams
         * in FIPS mode, unless the specified parameters are FIPS-approved.
         * However, since OpenSSL >= 1.1.1 will automatically select parameters
         * anyways, there's no point in attempting to load them.
         *
         * Change suggested by @t8m
         */
        if (EVP_default_properties_is_fips_enabled(NULL)) {
                WARN(LOG_PREFIX ": Ignoring user-selected DH parameters in FIPS mode. Using defaults.");
                return 0;
        }
 
        if ((bio = BIO_new_file(file, "r")) == NULL) {
                ERROR("Unable to open DH file - %s", file);
                return -1;
        }
 
        dh = PEM_read_bio_Parameters(bio, &dh);
        BIO_free(bio);
        if (!dh) {
                WARN("Unable to set DH parameters.  DH cipher suites may not work!");
                WARN("Fix this by generating the DH parameter file");
                return 0;
        }
 
        ret = SSL_CTX_set0_tmp_dh_pkey(ctx, dh);
        if (ret < 0) {
                ERROR("Unable to set DH parameters");
                return -1;
        }
 
        return 0;
}
 
static int tls_ctx_verify_chain_member(fr_unix_time_t *expires_first, X509 **self_signed,
                                       SSL_CTX *ctx, X509 *to_verify,
                                       fr_tls_chain_verify_mode_t verify_mode)
{
        fr_unix_time_t  not_after;
 
        STACK_OF(X509)  *chain;
        X509            *leaf;
 
        leaf = SSL_CTX_get0_certificate(ctx);
        if (!leaf) {
                ERROR("Chain does not contain a valid leaf certificate");
                return -1;
        }
 
        if (!SSL_CTX_get0_chain_certs(ctx, &chain)) {
                fr_tls_log(NULL, "Failed retrieving chain certificates");
                return -1;
        }
 
        switch (fr_tls_cert_is_valid(NULL, &not_after, to_verify)) {
        case -1:
                fr_tls_chain_marker_log(NULL, L_ERR, chain, leaf, to_verify);
                PERROR("Malformed certificate");
                return -1;
 
        case -2:
        case -3:
                switch (verify_mode) {
                case FR_TLS_CHAIN_VERIFY_SOFT:
                        fr_tls_chain_marker_log(NULL, L_WARN, chain, leaf, to_verify);
                        PWARN("Certificate validation failed");
                        break;
 
                case FR_TLS_CHAIN_VERIFY_HARD:
                        fr_tls_chain_marker_log(NULL, L_ERR, chain, leaf, to_verify);
                        PERROR("Certificate validation failed");
                        return -1;
 
                default:
                        break;
                }
 
        }
 
        /*
         *      Check for self-signed certs
         */
        switch (verify_mode) {
        case FR_TLS_CHAIN_VERIFY_SOFT:
        case FR_TLS_CHAIN_VERIFY_HARD:
                /*
                 *      There can be only one... self signed
                 *      cert in a chain.
                 *
                 *      We have to do this check manually
                 *      because the OpenSSL functions will
                 *      only check to see if it can build
                 *      a chain, not that all certificates
                 *      in the chain are used.
                 *
                 *      Having multiple self-signed certificates
                 *      usually indicates someone has copied
                 *      the wrong certificates into the
                 *      server.pem file.
                 */
                if (X509_name_cmp(X509_get_subject_name(to_verify),
                                  X509_get_issuer_name(to_verify)) == 0) {
                        if (*self_signed) {
                                switch (verify_mode) {
                                case FR_TLS_CHAIN_VERIFY_SOFT:
                                        WARN("Found multiple self-signed certificates in chain");
                                        WARN("First certificate was:");
                                        fr_tls_chain_marker_log(NULL, L_WARN,
                                                                            chain, leaf, *self_signed);
 
                                        WARN("Second certificate was:");
                                        fr_tls_chain_marker_log(NULL, L_WARN,
                                                                            chain, leaf, to_verify);
                                        break;
 
                                case FR_TLS_CHAIN_VERIFY_HARD:
                                        ERROR("Found multiple self-signed certificates in chain");
                                        ERROR("First certificate was:");
                                        fr_tls_chain_marker_log(NULL, L_ERR,
                                                                            chain, leaf, *self_signed);
 
                                        ERROR("Second certificate was:");
                                        fr_tls_chain_marker_log(NULL, L_ERR,
                                                                            chain, leaf, to_verify);
                                        return -1;
 
                                default:
                                        break;
                                }
                        }
                        *self_signed = to_verify;
                }
                break;
 
        default:
                break;
        }
 
        /*
         *      Record the time the first certificate in
         *      the chain expires so we can use it for
         *      runtime checks.
         */
        if (!fr_unix_time_ispos(*expires_first) ||
            (fr_unix_time_gt(*expires_first, not_after))) *expires_first = not_after;
 
         return 0;
}
 
static int tls_ctx_load_cert_chain(SSL_CTX *ctx, fr_tls_chain_conf_t *chain, bool allow_multi_self_signed)
{
        char            *password;
 
        /*
         *      Conf parser should ensure they're both populated
         */
        fr_assert(chain->certificate_file && chain->private_key_file);
 
        /*
         *      Set the password (this should have been retrieved earlier)
         */
        memcpy(&password, &chain->password, sizeof(password));
        SSL_CTX_set_default_passwd_cb_userdata(ctx, password);
 
        /*
         *      Always set the callback as it provides useful debug
         *      output if the certificate isn't set.
         */
        SSL_CTX_set_default_passwd_cb(ctx, fr_tls_session_password_cb);
 
        switch (chain->file_format) {
        case SSL_FILETYPE_PEM:
                if (!(SSL_CTX_use_certificate_chain_file(ctx, chain->certificate_file))) {
                        fr_tls_log(NULL, "Failed reading certificate file \"%s\"",
                                      chain->certificate_file);
                        return -1;
                }
                break;
 
        case SSL_FILETYPE_ASN1:
                if (!(SSL_CTX_use_certificate_file(ctx, chain->certificate_file, chain->file_format))) {
                        fr_tls_log(NULL, "Failed reading certificate file \"%s\"",
                                      chain->certificate_file);
                        return -1;
                }
                break;
 
        default:
                fr_assert(0);
                break;
        }
 
        if (!(SSL_CTX_use_PrivateKey_file(ctx, chain->private_key_file, chain->file_format))) {
                fr_tls_log(NULL, "Failed reading private key file \"%s\"",
                              chain->private_key_file);
                return -1;
        }
 
        {
                size_t          extra_cnt, i;
                /*
                 *      Load additional chain certificates from other files
                 *      This allows us to specify chains in DER format as
                 *      well as PEM, and means we can keep the intermediaries
                 *      CAs and client/server certs in separate files.
                 */
                extra_cnt = talloc_array_length(chain->ca_files);
                for (i = 0; i < extra_cnt; i++) {
                        FILE            *fp;
                        X509            *cert;
                        char const      *filename = chain->ca_files[i];
 
                        fp = fopen(filename, "r");
                        if (!fp) {
                                ERROR("Failed opening ca_file \"%s\": %s", filename, fr_syserror(errno));
                                return -1;
                        }
 
                        /*
                         *      Load the PEM encoded X509 certificate
                         */
                        switch (chain->file_format) {
                        case SSL_FILETYPE_PEM:
                                cert = PEM_read_X509(fp, NULL, NULL, NULL);
                                break;
 
                        case SSL_FILETYPE_ASN1:
                                cert = d2i_X509_fp(fp, NULL);
                                break;
 
                        default:
                                fr_assert(0);
                                fclose(fp);
                                return -1;
                        }
                        fclose(fp);
 
                        if (!cert) {
                                fr_tls_log(NULL, "Failed reading certificate file \"%s\"", filename);
                                return -1;
                        }
                        SSL_CTX_add0_chain_cert(ctx, cert);
                }
        }
 
        /*
         *      Check if the last loaded private key matches the last
         *      loaded certificate.
         *
         *      Note: The call to SSL_CTX_use_certificate_chain_file
         *      can load in a private key too.
         */
        if (!SSL_CTX_check_private_key(ctx)) {
                ERROR("Private key does not match the certificate public key");
                return -1;
        }
 
        /*
         *      Loop over the certificates checking validity periods.
         *      SSL_CTX_build_cert_chain does this too, but we can
         *      produce significantly better errors here.
         *
         *      After looping over all the certs we figure out when
         *      the chain will next need refreshing.
         */
        {
                fr_unix_time_t  expires_first = fr_unix_time_wrap(0);
                X509            *self_signed = NULL;
                STACK_OF(X509)  *our_chain;
                int             i;
 
                if (tls_ctx_verify_chain_member(&expires_first, &self_signed,
                                                ctx, SSL_CTX_get0_certificate(ctx),
                                                chain->verify_mode) < 0) return -1;
 
                if (!SSL_CTX_get0_chain_certs(ctx, &our_chain)) {
                        fr_tls_log(NULL, "Failed retrieving chain certificates");
                        return -1;
                }
 
                if (allow_multi_self_signed) self_signed = NULL;
 
DIAG_OFF(DIAG_UNKNOWN_PRAGMAS)
DIAG_OFF(used-but-marked-unused)        /* fix spurious warnings for sk macros */
                for (i = sk_X509_num(our_chain); i > 0 ; i--) {
                        /*
                         *      SSL_CTX_use_certificate_chain_file set the
                         *      current cert to be the one loaded from
                         *      that pem file.
                         */
                        if (tls_ctx_verify_chain_member(&expires_first, &self_signed,
                                                        ctx, sk_X509_value(our_chain, i - 1),
                                                        chain->verify_mode) < 0) return -1;
 
                        if (allow_multi_self_signed) self_signed = NULL;
                }
DIAG_ON(used-but-marked-unused) /* fix spurious warnings for sk macros */
DIAG_ON(DIAG_UNKNOWN_PRAGMAS)
                /*
                 *      Record this as a unix timestamp as
                 *      internal time might not progress at
                 *      the same rate as wallclock time.
                 */
                chain->valid_until = expires_first;
        }
 
        {
                int mode = SSL_BUILD_CHAIN_FLAG_CHECK;
 
                if (!chain->include_root_ca) mode |= SSL_BUILD_CHAIN_FLAG_NO_ROOT;
 
                /*
                 *      Explicitly check that the certificate chain
                 *      we just loaded is sane.
                 *
                 *      This operates on the last loaded certificate.
                 */
                switch (chain->verify_mode) {
                case FR_TLS_CHAIN_VERIFY_NONE:
                        mode |= SSL_BUILD_CHAIN_FLAG_CLEAR_ERROR | SSL_BUILD_CHAIN_FLAG_IGNORE_ERROR;
                        (void)SSL_CTX_build_cert_chain(ctx, mode);
                        break;
 
                /*
                 *      Seems to be a bug where
                 *      SSL_BUILD_CHAIN_FLAG_IGNORE_ERROR trashes the error,
                 *      so have the function fail as normal.
                 */
                case FR_TLS_CHAIN_VERIFY_SOFT:
                        if (!SSL_CTX_build_cert_chain(ctx, mode)) {
                                fr_tls_strerror_printf(NULL);
                                PWARN("Failed verifying chain");
                        }
                        break;
 
                case FR_TLS_CHAIN_VERIFY_HARD:
                        if (!SSL_CTX_build_cert_chain(ctx, mode)) {
                                fr_tls_strerror_printf(NULL);
                                PERROR("Failed verifying chain");
                                return -1;
                        }
                        break;
 
                default:
                        break;
                }
        }
 
        return 0;
}
 
static inline CC_HINT(always_inline)
int tls_ctx_version_set(
                        UNUSED
                        int *ctx_options, SSL_CTX *ctx, fr_tls_conf_t const *conf)
{
        /*
         *      SSL_CTX_set_(min|max)_proto_version was included in OpenSSL 1.1.0
         *
         *      This version already defines macros for TLS1_2_VERSION and
         *      below, so we don't need to check for them explicitly.
         *
         *      TLS1_3_VERSION is available in OpenSSL 1.1.1.
         *
         *      TLS1_4_VERSION does not exist yet.  But we allow it
         *      only if it is explicitly permitted by the
         *      administrator.
         */
        if (conf->tls_max_version > (float) 0.0) {
                int max_version = 0;
 
                if (conf->tls_min_version > conf->tls_max_version) {
                        /*
                         *      %f is actually %lg now (double).  Compile complains about
                         *      implicit promotion unless we cast args to double.
                         */
                        ERROR("tls_min_version (%f) must be <= tls_max_version (%f)",
                              (double)conf->tls_min_version, (double)conf->tls_max_version);
                error:
                        return -1;
                }
 
                if (conf->tls_max_version < (float) 1.0) {
                        ERROR("tls_max_version must be >= 1.0 as SSLv2 and SSLv3 are permanently disabled");
                        goto error;
                }
 
#  ifdef TLS1_4_VERSION
                else if (conf->tls_max_version >= (float) 1.4) max_version = TLS1_4_VERSION;
#  endif
#  ifdef TLS1_3_VERSION
                else if (conf->tls_max_version >= (float) 1.3) max_version = TLS1_3_VERSION;
#  endif
                else if (conf->tls_max_version >= (float) 1.2) max_version = TLS1_2_VERSION;
                else if (conf->tls_max_version >= (float) 1.1) max_version = TLS1_1_VERSION;
                else max_version = TLS1_VERSION;
 
                /*
                 *      Complain about insecure TLS versions.
                 */
                if (max_version < TLS1_2_VERSION) {
                        WARN("TLS 1.0 and 1.1 are insecure and SHOULD NOT be used");
                        WARN("tls_max_version SHOULD be 1.2 or greater");
                }
 
                if (!SSL_CTX_set_max_proto_version(ctx, max_version)) {
                        fr_tls_log(NULL, "Failed setting TLS maximum version");
                        goto error;
                }
        }
 
        {
                int min_version;
 
                if (conf->tls_min_version < (float) 1.0) {
                        ERROR("tls_min_version must be >= 1.0 as SSLv2 and SSLv3 are permanently disabled");
                        goto error;
                }
#  ifdef TLS1_4_VERSION
                else if (conf->tls_min_version >= (float) 1.4) min_version = TLS1_4_VERSION;
#  endif
#  ifdef TLS1_3_VERSION
                else if (conf->tls_min_version >= (float) 1.3) min_version = TLS1_3_VERSION;
#  endif
                else if (conf->tls_min_version >= (float) 1.2) min_version = TLS1_2_VERSION;
                else if (conf->tls_min_version >= (float) 1.1) min_version = TLS1_1_VERSION;
                else min_version = TLS1_VERSION;
 
                /*
                 *      Complain about insecure TLS versions.
                 */
                if (min_version < TLS1_2_VERSION) {
                        WARN("TLS 1.0 and 1.1 are insecure and SHOULD NOT be used");
                        WARN("tls_min_version SHOULD be 1.2 or greater");
                }
 
                if (!SSL_CTX_set_min_proto_version(ctx, min_version)) {
                        fr_tls_log(NULL, "Failed setting TLS minimum version");
                        goto error;
                }
        }
 
        return 0;
}
 
/** Create SSL context
 *
 * - Load the trusted CAs
 * - Load the Private key & the certificate
 * - Set the Context options & Verify options
 *
 * @param conf to read settings from.
 * @param client If true SSL_CTX will be configured as a client context.
 * @return
 *      - A new SSL_CTX on success.
 *      - NULL on failure.
 */
SSL_CTX *fr_tls_ctx_alloc(fr_tls_conf_t const *conf, bool client)
{
        SSL_CTX         *ctx;
        X509_STORE      *cert_vpstore;
        X509_STORE      *verify_store;
        int             ctx_options = 0;
 
        ctx = SSL_CTX_new(TLS_method());
        if (!ctx) {
                fr_tls_log(NULL, "Failed creating TLS context");
                return NULL;
        }
 
        /*
         *      Save the config on the context so that callbacks which
         *      only get SSL_CTX* e.g. session persistence, can get at it.
         */
        SSL_CTX_set_ex_data(ctx, FR_TLS_EX_INDEX_CONF, UNCONST(void *, conf));
 
        /*
         *      Identify the type of certificates that needs to be loaded
         */
#ifdef PSK_MAX_IDENTITY_LEN
        /*
         *      A dynamic query exists.  There MUST NOT be a
         *      statically configured identity and password.
         */
        if (conf->psk_query) {
                if (!*conf->psk_query) {
                        ERROR("Invalid PSK Configuration: psk_query cannot be empty");
                error:
                        SSL_CTX_free(ctx);
                        return NULL;
                }
 
                if (conf->psk_identity && *conf->psk_identity) {
                        ERROR("Invalid PSK Configuration: psk_identity and psk_query cannot be used at the same time.");
                        goto error;
                }
 
                if (conf->psk_password && *conf->psk_password) {
                        ERROR("Invalid PSK Configuration: psk_hexphrase and psk_query cannot be used at the same time.");
                        goto error;
                }
 
                if (client) {
                        ERROR("Invalid PSK Configuration: psk_query cannot be used for outgoing connections");
                        goto error;
                }
 
                /*
                 *      Now check that if PSK is being used, that the config is valid.
                 */
        } else if (conf->psk_identity) {
                if (!*conf->psk_identity) {
                        ERROR("Invalid PSK Configuration: psk_identity is empty");
                        goto error;
                }
 
 
                if (!conf->psk_password || !*conf->psk_password) {
                        ERROR("Invalid PSK Configuration: psk_identity is set, but there is no psk_hexphrase");
                        goto error;
                }
 
        } else if (conf->psk_password) {
                ERROR("Invalid PSK Configuration: psk_hexphrase is set, but there is no psk_identity");
                goto error;
        }
 
        /*
         *      Set the server PSK callback if necessary.
         */
        if (!client && (conf->psk_identity || conf->psk_query)) {
                SSL_CTX_set_psk_server_callback(ctx, fr_tls_session_psk_server_cb);
        }
 
        /*
         *      Do more sanity checking if we have a PSK identity.  We
         *      check the password, and convert it to it's final form.
         */
        if (conf->psk_identity && *conf->psk_identity) {
                size_t psk_len, hex_len;
                uint8_t buffer[PSK_MAX_PSK_LEN];
 
                if (client) {
                        SSL_CTX_set_psk_client_callback(ctx, fr_tls_session_psk_client_cb);
                }
 
                if (!conf->psk_password) goto error; /* clang is too dumb to catch the above checks */
 
                psk_len = strlen(conf->psk_password);
                if (strlen(conf->psk_password) > (2 * PSK_MAX_PSK_LEN)) {
                        ERROR("psk_hexphrase is too long (max %d)", PSK_MAX_PSK_LEN);
                        goto error;
                }
 
                /*
                 *      Check the password now, so that we don't have
                 *      errors at run-time.
                 */
                hex_len = fr_base16_decode(NULL,
                                     &FR_DBUFF_TMP(buffer, sizeof(buffer)),
                                     &FR_SBUFF_IN(conf->psk_password, psk_len), false);
                if (psk_len != (2 * hex_len)) {
                        ERROR("psk_hexphrase is not all hex");
                        goto error;
                }
 
                goto post_ca;
        }
#else
        (void) client;  /* -Wunused */
#endif
 
        /*
         *      Set mode before processing any certifictes
         */
        {
                int mode = SSL_MODE_ASYNC;
 
                /*
                 *      OpenSSL will automatically create certificate chains,
                 *      unless we tell it to not do that.  The problem is that
                 *      it sometimes gets the chains right from a certificate
                 *      signature view, but wrong from the clients view.
                 *
                 *      It's better just to have users specify the complete
                 *      chains.
                 */
                mode |= SSL_MODE_NO_AUTO_CHAIN;
 
                if (client) {
                        mode |= SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER;
                        mode |= SSL_MODE_AUTO_RETRY;
                }
 
                if (mode) SSL_CTX_set_mode(ctx, mode);
        }
 
        /*
         *      Initialise a separate store for verifying user
         *      certificates.
         *
         *      This makes the configuration cleaner as there's
         *      no mixing of chain certs and user certs.
         */
        MEM(verify_store = X509_STORE_new());
 
        /* Sets OpenSSL's (CERT *)->verify_store, overring (SSL_CTX *)->cert_store */
        SSL_CTX_set0_verify_cert_store(ctx, verify_store);
 
        /* This isn't accessible to use later, i.e. there's no SSL_CTX_get0_verify_cert_store */
        SSL_CTX_set_ex_data(ctx, FR_TLS_EX_CTX_INDEX_VERIFY_STORE, verify_store);
 
        /*
         *      Load the CAs we trust
         */
        if (conf->ca_file || conf->ca_path) {
                /*
                 *      This adds all the certificates to the store for conf->ca_file
                 *      and adds a dynamic lookup for conf->ca_path.
                 *
                 *      It's also possible to add extra virtual server lookups
                 */
                if (!X509_STORE_load_locations(verify_store, conf->ca_file, conf->ca_path)) {
                        fr_tls_log(NULL, "Failed reading Trusted root CA list \"%s\"",
                                      conf->ca_file);
                        goto error;
                }
 
                /*
                 *      These set the default parameters of the store when the
                 *      store is involved in building chains.
                 *
                 *      - X509_PURPOSE_SSL_CLIENT ensure the purpose of the
                 *        client certificate is for peer authentication as
                 *        a client.
                 */
                X509_STORE_set_purpose(verify_store, X509_PURPOSE_SSL_CLIENT);
 
                /*
                 *      Sets the list of CAs we send to the peer if we're
                 *      requesting a certificate.
                 *
                 *      This does not change the trusted certificate authorities,
                 *      those are set above with SSL_CTX_load_verify_locations.
                 */
                if (conf->ca_file) SSL_CTX_set_client_CA_list(ctx, SSL_load_client_CA_file(conf->ca_file));
        } else {
                X509_STORE_set_default_paths(verify_store);
        }
 
        /*
         *      Load our certificate chains and keys
         */
        if (conf->chains) {
                size_t chains_conf = talloc_array_length(conf->chains);
 
                /*
                 *      Load our keys and certificates
                 *
                 *      If certificates are of type PEM then we can make use
                 *      of cert chain authentication using openssl api call
                 *      SSL_CTX_use_certificate_chain_file.  Please see how
                 *      the cert chain needs to be given in PEM from
                 *      openSSL.org
                 */
                {
                        size_t i;
 
                        for (i = 0; i < chains_conf; i++) {
                                if (tls_ctx_load_cert_chain(ctx, conf->chains[i], false) < 0) goto error;
                        }
                }
 
                /*
                 *      Print out our certificate chains.
                 *
                 *      There may be up to three, one for RSA, DH, DSA and EC.
                 *      OpenSSL internally and transparently stores completely
                 *      separate and distinct RSA/DSA/DH/ECC key pairs and chains.
                 */
                if (DEBUG_ENABLED2) {
                        size_t chains_set = 0;
                        int ret;
 
                        /*
                         *      Iterate over the different chain types we have
                         *      RSA, DSA, DH, EC etc...
                         */
                        for (ret = SSL_CTX_set_current_cert(ctx, SSL_CERT_SET_FIRST);
                             ret == 1;
                             ret = SSL_CTX_set_current_cert(ctx, SSL_CERT_SET_NEXT)) chains_set++;
 
                        /*
                         *      Check for discrepancies
                         */
 
                        DEBUG3("Found %zu server certificate chain(s)", chains_set);
 
                        if (chains_set != chains_conf) {
                                WARN("Number of chains configured (%zu) does not match chains set (%zu)",
                                      chains_conf, chains_set);
                                if (chains_conf > chains_set) WARN("Only one chain per key type is allowed, "
                                                                   "check config for duplicates");
                        }
 
                        for (ret = SSL_CTX_set_current_cert(ctx, SSL_CERT_SET_FIRST);
                             ret == 1;
                             ret = SSL_CTX_set_current_cert(ctx, SSL_CERT_SET_NEXT)) {
                                STACK_OF(X509)  *our_chain;
                                X509            *our_cert;
 
                                our_cert = SSL_CTX_get0_certificate(ctx);
 
                                /*
                                 *      The pkey type of the server certificate
                                 *      determines which pkey slot OpenSSL
                                 *      uses to store the chain.
                                 */
                                DEBUG3("%s chain", fr_tls_utils_x509_pkey_type(our_cert));
                                if (!SSL_CTX_get0_chain_certs(ctx, &our_chain)) {
                                        fr_tls_log(NULL, "Failed retrieving chain certificates");
                                        goto error;
                                }
 
                                if (DEBUG_ENABLED3) fr_tls_chain_log(NULL, L_DBG, our_chain, our_cert);
                        }
                        (void)SSL_CTX_set_current_cert(ctx, SSL_CERT_SET_FIRST);        /* Reset */
                }
        }
 
#ifdef PSK_MAX_IDENTITY_LEN
post_ca:
#endif
        if (tls_ctx_version_set(&ctx_options, ctx, conf) < 0) goto error;
 
        /*
         *      SSL_OP_SINGLE_DH_USE must be used in order to prevent
         *      small subgroup attacks and forward secrecy. Always
         *      using SSL_OP_SINGLE_DH_USE has an impact on the
         *      computer time needed during negotiation, but it is not
         *      very large.
         */
        if (!conf->disable_single_dh_use) {
                ctx_options |= SSL_OP_SINGLE_DH_USE;
        }
 
#ifdef SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS
        /*
         *      Note: This flag isn't honoured by all OpenSSL forks.
         */
        if (conf->allow_renegotiation) {
                ctx_options |= SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS;
        }
#endif
 
        /*
         *      SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS to work around issues
         *      in Windows Vista client.
         *      http://www.openssl.org/~bodo/tls-cbc.txt
         *      http://www.nabble.com/(RADIATOR)-Radiator-Version-3.16-released-t2600070.html
         */
        ctx_options |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
 
        /*
         *      SSL_OP_CIPHER_SERVER_PREFERENCE to follow best practice
         *      of nowday's TLS: do not allow poorly-selected ciphers from
         *      client to take preference
         */
        if (conf->cipher_server_preference) ctx_options |= SSL_OP_CIPHER_SERVER_PREFERENCE;
 
        SSL_CTX_set_options(ctx, ctx_options);
 
        /*
         *      TODO: Set the RSA & DH
         *      SSL_CTX_set_tmp_rsa_callback(ctx, cbtls_rsa);
         *      SSL_CTX_set_tmp_dh_callback(ctx, cbtls_dh);
         */
 
        /*
         *      Set the block size for record padding.  This is only
         *      used in TLS 1.3.
         */
        if (conf->padding_block_size) SSL_CTX_set_block_padding(ctx, conf->padding_block_size);
 
        /*
         *      Set elliptical curve crypto configuration.
         */
#ifndef OPENSSL_NO_ECDH
        if (ctx_ecdh_curve_set(ctx, conf->ecdh_curve, conf->disable_single_dh_use) < 0) goto error;
#endif
 
 
        /* Set Info callback */
        SSL_CTX_set_info_callback(ctx, fr_tls_session_info_cb);
 
        /*
         *      Check the certificates for revocation.
         */
#ifdef X509_V_FLAG_CRL_CHECK_ALL
        if (conf->verify.check_crl) {
                cert_vpstore = SSL_CTX_get_cert_store(ctx);
                if (cert_vpstore == NULL) {
                        fr_tls_log(NULL, "Error reading Certificate Store");
                        goto error;
                }
                X509_STORE_set_flags(cert_vpstore, X509_V_FLAG_CRL_CHECK | X509_V_FLAG_CRL_CHECK_ALL);
#ifdef X509_V_FLAG_USE_DELTAS
                /*
                 *      If set, delta CRLs (if present) are used to
                 *      determine certificate status. If not set
                 *      deltas are ignored.
                 *
                 *      So it's safe to always set this flag.
                 */
                X509_STORE_set_flags(cert_vpstore, X509_V_FLAG_USE_DELTAS);
#endif
        }
#endif
 
        /*
         *      SSL_ctx_set_verify is now called in the session
         *      alloc functions so they can set custom behaviour
         *      depending on the code area the SSL * will be used
         *      and whether we're acting as a client or server.
         */
        if (conf->verify_depth) {
                SSL_CTX_set_verify_depth(ctx, conf->verify_depth);
        }
 
#ifdef HAVE_OPENSSL_OCSP_H
        /*
         *      Configure OCSP stapling for the server cert
         */
        if (conf->staple.enable) {
                SSL_CTX_set_tlsext_status_cb(ctx, fr_tls_ocsp_staple_cb);
                SSL_CTX_set_tlsext_status_arg(ctx, UNCONST(fr_tls_ocsp_conf_t *, &(conf->staple)));
        }
#endif
 
        /*
         *      Set the cipher list if we were told to
         */
        if (conf->cipher_list) {
                if (!SSL_CTX_set_cipher_list(ctx, conf->cipher_list)) {
                        fr_tls_log(NULL, "Failed setting cipher list");
                        goto error;
                }
        }
 
        /*
         *      Print the actual cipher list
         */
        if (DEBUG_ENABLED3) {
                SSL             *ssl;
                unsigned int    i = 0;
                char const      *cipher;
 
                ssl = SSL_new(ctx);
                if (!ssl) {
                        fr_tls_log(NULL, "Failed creating temporary SSL session");
                        goto error;
                }
 
                DEBUG3("Configured ciphers (by priority)");
 
                while ((cipher = SSL_get_cipher_list(ssl, i))) {
                        DEBUG3("[%u] %s", i, cipher);
                        i++;            /* Print index starting at zero */
                }
 
                SSL_free(ssl);
        }
 
        /*
         *      Load dh params
         */
        if (conf->dh_file) {
                if (ctx_dh_params_load(ctx, UNCONST(char *, conf->dh_file)) < 0) goto error;
        } else {
                /*
                 *      Tell OpenSSL to automatically set the DH
                 *      parameters based on the the size of the key
                 *      associated with the certificate, or for PSK,
                 *      with the negotiated symmetric cipher key.
                 */
                SSL_CTX_set_dh_auto(ctx, 1);
        }
 
        /*
         *      Setup session caching
         */
        if (fr_tls_cache_ctx_init(ctx, &conf->cache) < 0) goto error;
 
        /*
         *      Set the keylog file if the admin requested it.
         */
        if ((getenv("SSLKEYLOGFILE") != NULL) || (conf->keylog_file && *conf->keylog_file)) {
                SSL_CTX_set_keylog_callback(ctx, fr_tls_session_keylog_cb);
        }
 
        return ctx;
}
#endif