path: root/modules/md/md_acme_drive.c

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#include <assert.h>
#include <stdlib.h>

#include <apr_lib.h>
#include <apr_strings.h>
#include <apr_buckets.h>
#include <apr_hash.h>
#include <apr_uri.h>

#include "md.h"
#include "md_crypt.h"
#include "md_json.h"
#include "md_jws.h"
#include "md_http.h"
#include "md_log.h"
#include "md_result.h"
#include "md_reg.h"
#include "md_store.h"
#include "md_util.h"

#include "md_acme.h"
#include "md_acme_acct.h"
#include "md_acme_authz.h"
#include "md_acme_order.h"

#include "md_acme_drive.h"
#include "md_acmev2_drive.h"

/**************************************************************************************************/
/* account setup */

static apr_status_t use_staged_acct(md_acme_t *acme, struct md_store_t *store,
                                    const md_t *md, apr_pool_t *p)
{
    md_acme_acct_t *acct;
    md_pkey_t *pkey;
    apr_status_t rv;
    
    if (APR_SUCCESS == (rv = md_acme_acct_load(&acct, &pkey, store, 
                                               MD_SG_STAGING, md->name, acme->p))) {
        acme->acct_id = NULL;
        acme->acct = acct;
        acme->acct_key = pkey;
        rv = md_acme_acct_validate(acme, NULL, p);
    }
    return rv;
}

static apr_status_t save_acct_staged(md_acme_t *acme, md_store_t *store, 
                                     const char *md_name, apr_pool_t *p)
{
    md_json_t *jacct;
    apr_status_t rv;
    
    jacct = md_acme_acct_to_json(acme->acct, p);
    
    rv = md_store_save(store, p, MD_SG_STAGING, md_name, MD_FN_ACCOUNT, MD_SV_JSON, jacct, 0);
    if (APR_SUCCESS == rv) {
        rv = md_store_save(store, p, MD_SG_STAGING, md_name, MD_FN_ACCT_KEY, 
                           MD_SV_PKEY, acme->acct_key, 0);
    }
    return rv;
}

apr_status_t md_acme_drive_set_acct(md_proto_driver_t *d, md_result_t *result) 
{
    md_acme_driver_t *ad = d->baton;
    md_t *md = ad->md;
    apr_status_t rv = APR_SUCCESS;
    int update_md = 0, update_acct = 0;
    
    md_result_activity_printf(result, "Selecting account to use for %s", d->md->name);
    md_acme_clear_acct(ad->acme);
    
    /* Do we have a staged (modified) account? */
    if (APR_SUCCESS == (rv = use_staged_acct(ad->acme, d->store, md, d->p))) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "re-using staged account");
    }
    else if (!APR_STATUS_IS_ENOENT(rv)) {
        goto leave;
    }
    
    /* Get an account for the ACME server for this MD */
    if (!ad->acme->acct && md->ca_account) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "re-use account '%s'", md->ca_account);
        rv = md_acme_use_acct_for_md(ad->acme, d->store, d->p, md->ca_account, md);
        if (APR_STATUS_IS_ENOENT(rv) || APR_STATUS_IS_EINVAL(rv)) {
            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "rejected %s", md->ca_account);
            md->ca_account = NULL;
            update_md = 1;
        }
        else if (APR_SUCCESS != rv) {
            goto leave;
        }
    }

    if (!ad->acme->acct && !md->ca_account) {
        /* Find a local account for server, store at MD */ 
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "%s: looking at existing accounts",
                      d->proto->protocol);
        if (APR_SUCCESS == (rv = md_acme_find_acct_for_md(ad->acme, d->store, md))) {
            md->ca_account = md_acme_acct_id_get(ad->acme);
            update_md = 1;
            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "%s: using account %s (id=%s)",
                          d->proto->protocol, ad->acme->acct->url, md->ca_account);
        }
    }
    
    if (!ad->acme->acct) {
        /* No account staged, no suitable found in store, register a new one */
        md_result_activity_printf(result, "Creating new ACME account for %s", d->md->name);
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "%s: creating new account", 
                      d->proto->protocol);
        
        if (!ad->md->contacts || apr_is_empty_array(md->contacts)) {
            rv = APR_EINVAL;
            md_result_printf(result, rv, "No contact information is available for MD %s. "
                             "Configure one using the MDContactEmail or ServerAdmin directive.", md->name);            
            md_result_log(result, MD_LOG_ERR);
            goto leave;
        }
        
        /* ACMEv1 allowed registration of accounts without accepted Terms-of-Service.
         * ACMEv2 requires it. Fail early in this case with a meaningful error message.
         */ 
        if (!md->ca_agreement) {
            md_result_printf(result, APR_EINVAL,
                  "the CA requires you to accept the terms-of-service "
                  "as specified in <%s>. "
                  "Please read the document that you find at that URL and, "
                  "if you agree to the conditions, configure "
                  "\"MDCertificateAgreement accepted\" "
                  "in your Apache. Then (graceful) restart the server to activate.", 
                  ad->acme->ca_agreement);
            md_result_log(result, MD_LOG_ERR);
            rv = result->status;
            goto leave;
        }
    
        if (ad->acme->eab_required && (!md->ca_eab_kid || !strcmp("none", md->ca_eab_kid))) {
            md_result_printf(result, APR_EINVAL,
                  "the CA requires 'External Account Binding' which is not "
                  "configured. This means you need to obtain a 'Key ID' and a "
                  "'HMAC' from the CA and configure that using the "
                  "MDExternalAccountBinding directive in your config. "
                  "The creation of a new ACME account will most likely fail, "
                  "but an attempt is made anyway.",
                  ad->acme->ca_agreement);
            md_result_log(result, MD_LOG_INFO);
        }

        rv = md_acme_acct_register(ad->acme, d->store, md, d->p);
        if (APR_SUCCESS != rv) {
            if (APR_SUCCESS != ad->acme->last->status) {
                md_result_dup(result, ad->acme->last);
                md_result_log(result, MD_LOG_ERR);
            }
            goto leave;
        }

        md->ca_account = NULL;
        update_md = 1;
        update_acct = 1;
    }
    
leave:
    /* Persist MD changes in STAGING, so we pick them up on next run */
    if (APR_SUCCESS == rv && update_md) {
        rv = md_save(d->store, d->p, MD_SG_STAGING, ad->md, 0);
    }
    /* Persist account changes in STAGING, so we pick them up on next run */
    if (APR_SUCCESS == rv && update_acct) {
        rv = save_acct_staged(ad->acme, d->store, md->name, d->p);
    }
    return rv;
}

/**************************************************************************************************/
/* poll cert */

static void get_up_link(md_proto_driver_t *d, apr_table_t *headers)
{
    md_acme_driver_t *ad = d->baton;

    ad->chain_up_link = md_link_find_relation(headers, d->p, "up");
    if (ad->chain_up_link) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, 
                      "server reports up link as %s", ad->chain_up_link);
    }
} 

static apr_status_t add_http_certs(apr_array_header_t *chain, apr_pool_t *p,
                                   const md_http_response_t *res)
{
    apr_status_t rv = APR_SUCCESS;
    const char *ct;
    
    ct = apr_table_get(res->headers, "Content-Type");
    ct = md_util_parse_ct(res->req->pool, ct);
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, rv, p,
                  "parse certs from %s -> %d (%s)", res->req->url, res->status, ct);
    if (ct && !strcmp("application/x-pkcs7-mime", ct)) {
        /* this looks like a root cert and we do not want those in our chain */
        goto out; 
    }

    /* Lets try to read one or more certificates */
    if (APR_SUCCESS != (rv = md_cert_chain_read_http(chain, p, res))
        && APR_STATUS_IS_ENOENT(rv)) {
        rv = APR_EAGAIN;
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p, 
                      "cert not in response from %s", res->req->url);
    }
out:
    return rv;
}

static apr_status_t on_add_cert(md_acme_t *acme, const md_http_response_t *res, void *baton)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    apr_status_t rv = APR_SUCCESS;
    int count;
    
    (void)acme;
    count = ad->cred->chain->nelts;
    if (APR_SUCCESS == (rv = add_http_certs(ad->cred->chain, d->p, res))) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "%d certs parsed", 
                      ad->cred->chain->nelts - count);
        get_up_link(d, res->headers);
    }
    return rv;
}

static apr_status_t get_cert(void *baton, int attempt)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    
    (void)attempt;
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, 0, d->p, "retrieving cert from %s",
                  ad->order->certificate);
    return md_acme_GET(ad->acme, ad->order->certificate, NULL, NULL, on_add_cert, NULL, d);
}

apr_status_t md_acme_drive_cert_poll(md_proto_driver_t *d, int only_once)
{
    md_acme_driver_t *ad = d->baton;
    apr_status_t rv;
    
    assert(ad->md);
    assert(ad->acme);
    assert(ad->order);
    assert(ad->order->certificate);
    
    if (only_once) {
        rv = get_cert(d, 0);
    }
    else {
        rv = md_util_try(get_cert, d, 1, ad->cert_poll_timeout, 0, 0, 1);
    }
    
    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, "poll for cert at %s", ad->order->certificate);
    return rv;
}

/**************************************************************************************************/
/* order finalization */

static apr_status_t on_init_csr_req(md_acme_req_t *req, void *baton)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    md_json_t *jpayload;

    jpayload = md_json_create(req->p);
    md_json_sets(ad->csr_der_64, jpayload, MD_KEY_CSR, NULL);
    
    return md_acme_req_body_init(req, jpayload);
} 

static apr_status_t csr_req(md_acme_t *acme, const md_http_response_t *res, void *baton)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    const char *location;
    md_cert_t *cert;
    apr_status_t rv = APR_SUCCESS;
    
    (void)acme;
    location = apr_table_get(res->headers, "location");
    if (!location) {
        md_log_perror(MD_LOG_MARK, MD_LOG_ERR, APR_EINVAL, d->p, 
                      "cert created without giving its location header");
        return APR_EINVAL;
    }
    ad->order->certificate = apr_pstrdup(d->p, location);
    if (APR_SUCCESS != (rv = md_acme_order_save(d->store, d->p, MD_SG_STAGING, 
                                                d->md->name, ad->order, 0))) { 
        md_log_perror(MD_LOG_MARK, MD_LOG_ERR, APR_EINVAL, d->p, 
                      "%s: saving cert url %s", d->md->name, location);
        return rv;
    }
    
    /* Check if it already was sent with this response */
    ad->chain_up_link = NULL;
    if (APR_SUCCESS == (rv = md_cert_read_http(&cert, d->p, res))) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "cert parsed");
        apr_array_clear(ad->cred->chain);
        APR_ARRAY_PUSH(ad->cred->chain, md_cert_t*) = cert;
        get_up_link(d, res->headers);
    }
    else if (APR_STATUS_IS_ENOENT(rv)) {
        rv = APR_SUCCESS;
        if (location) {
            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, 
                          "cert not in response, need to poll %s", location);
        }
    }
    
    return rv;
}

/**
 * Pre-Req: all domains have been validated by the ACME server, e.g. all have AUTHZ
 * resources that have status 'valid'
 *  - acme_driver->cred keeps the credentials to setup (key spec) 
 * - Setup private key, if not already there
 * - Generate a CSR with org, contact, etc
 * - Optionally enable must-staple OCSP extension
 * - Submit CSR, expect 201 with location
 * - POLL location for certificate
 * - store certificate
 * - retrieve cert chain information from cert
 * - GET cert chain
 * - store cert chain
 */
apr_status_t md_acme_drive_setup_cred_chain(md_proto_driver_t *d, md_result_t *result)
{
    md_acme_driver_t *ad = d->baton;
    md_pkey_spec_t *spec;
    md_pkey_t *privkey;
    apr_status_t rv;

    md_result_activity_printf(result, "Finalizing order for %s", ad->md->name);

    assert(ad->cred);
    spec = ad->cred->spec;
        
    rv = md_pkey_load(d->store, MD_SG_STAGING, d->md->name, spec, &privkey, d->p);
    if (APR_STATUS_IS_ENOENT(rv)) {
        if (APR_SUCCESS == (rv = md_pkey_gen(&privkey, d->p, spec))) {
            rv = md_pkey_save(d->store, d->p, MD_SG_STAGING, d->md->name, spec, privkey, 1);
        }
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, 
                      "%s: generate %s privkey", d->md->name, md_pkey_spec_name(spec));
    }
    if (APR_SUCCESS != rv) goto leave;
    
    md_result_activity_printf(result, "Creating %s CSR", md_pkey_spec_name(spec));
    rv = md_cert_req_create(&ad->csr_der_64, d->md->name, ad->domains, 
                            ad->md->must_staple, privkey, d->p);
    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "%s: create %s CSR", 
                  d->md->name, md_pkey_spec_name(spec));
    if (APR_SUCCESS != rv) goto leave;
    
    md_result_activity_printf(result, "Submitting %s CSR to CA", md_pkey_spec_name(spec));
    assert(ad->order->finalize);
    rv = md_acme_POST(ad->acme, ad->order->finalize, on_init_csr_req, NULL, csr_req, NULL, d);

leave:
    md_acme_report_result(ad->acme, rv, result);
    return rv;
}

/**************************************************************************************************/
/* cert chain retrieval */

static apr_status_t on_add_chain(md_acme_t *acme, const md_http_response_t *res, void *baton)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    apr_status_t rv = APR_SUCCESS;
    const char *ct;
    
    (void)acme;
    ct = apr_table_get(res->headers, "Content-Type");
    ct = md_util_parse_ct(res->req->pool, ct);
    if (ct && !strcmp("application/x-pkcs7-mime", ct)) {
        /* root cert most likely, end it here */
        return APR_SUCCESS;
    }
    
    if (APR_SUCCESS == (rv = add_http_certs(ad->cred->chain, d->p, res))) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "chain cert parsed");
        get_up_link(d, res->headers);
    }
    return rv;
}

static apr_status_t get_chain(void *baton, int attempt)
{
    md_proto_driver_t *d = baton;
    md_acme_driver_t *ad = d->baton;
    const char *prev_link = NULL;
    apr_status_t rv = APR_SUCCESS;

    while (APR_SUCCESS == rv && ad->cred->chain->nelts < 10) {
        int nelts = ad->cred->chain->nelts;
        
        if (ad->chain_up_link && (!prev_link || strcmp(prev_link, ad->chain_up_link))) {
            prev_link = ad->chain_up_link;

            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, 
                          "next chain cert at  %s", ad->chain_up_link);
            rv = md_acme_GET(ad->acme, ad->chain_up_link, NULL, NULL, on_add_chain, NULL, d);
            
            if (APR_SUCCESS == rv && nelts == ad->cred->chain->nelts) {
                break;
            }
            else if (APR_SUCCESS != rv) {
                md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, d->p,
                              "error retrieving certificate from %s", ad->chain_up_link);
                return rv;
            }
        }
        else if (ad->cred->chain->nelts <= 1) {
            /* This cannot be the complete chain (no one signs new web certs with their root)
             * and we did not see a "Link: ...rel=up", so we do not know how to continue. */
            md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, d->p, 
                          "no link header 'up' for new certificate, unable to retrieve chain");
            rv = APR_EINVAL;
            break;
        }
        else {
            rv = APR_SUCCESS;
            break;
        }
    }
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, rv, d->p, 
                  "got chain with %d certs (%d. attempt)", ad->cred->chain->nelts, attempt);
    return rv;
}

static apr_status_t ad_chain_retrieve(md_proto_driver_t *d)
{
    md_acme_driver_t *ad = d->baton;
    apr_status_t rv;
    
    /* This may be called repeatedly and needs to progress. The relevant state is in
     * ad->cred->chain          the certificate chain, starting with the new cert for the md
     * ad->order->certificate   the url where ACME offers us the new md certificate. This may
     *                          be a single one or even the complete chain
     * ad->chain_up_link         in case the last certificate retrieval did not end the chain,
     *                          the link header with relation "up" gives us the location
     *                          for the next cert in the chain
     */
    if (md_array_is_empty(ad->cred->chain)) {
        /* Need to start at the order */
        ad->chain_up_link = NULL;
        if (!ad->order) {
            rv = APR_EGENERAL;
            md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, d->p, 
                "%s: asked to retrieve chain, but no order in context", d->md->name);
            goto out;
        }
        if (!ad->order->certificate) {
            rv = APR_EGENERAL;
            md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, d->p, 
                "%s: asked to retrieve chain, but no certificate url part of order", d->md->name);
            goto out;
        }
        
        if (APR_SUCCESS != (rv = md_acme_drive_cert_poll(d, 0))) {
            goto out;
        }
    }
    
    rv = md_util_try(get_chain, d, 0, ad->cert_poll_timeout, 0, 0, 0);
    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, "chain retrieved");
    
out:
    return rv;
}

/**************************************************************************************************/
/* ACME driver init */

static apr_status_t acme_driver_preload_init(md_proto_driver_t *d, md_result_t *result)
{
    md_acme_driver_t *ad;
    md_credentials_t *cred;
    int i;
    
    md_result_set(result, APR_SUCCESS, NULL);
    
    ad = apr_pcalloc(d->p, sizeof(*ad));
    
    d->baton = ad;
    
    ad->driver = d;
    ad->authz_monitor_timeout = apr_time_from_sec(30);
    ad->cert_poll_timeout = apr_time_from_sec(30);
    ad->ca_challenges = apr_array_make(d->p, 3, sizeof(const char*));
    
    /* We want to obtain credentials (key+certificate) for every key spec in this MD */
    ad->creds = apr_array_make(d->p, md_pkeys_spec_count(d->md->pks), sizeof(md_credentials_t*));
    for (i = 0; i < md_pkeys_spec_count(d->md->pks); ++i) {
        cred = apr_pcalloc(d->p, sizeof(*cred));
        cred->spec = md_pkeys_spec_get(d->md->pks, i);
        cred->chain = apr_array_make(d->p, 5, sizeof(md_cert_t*));
        APR_ARRAY_PUSH(ad->creds, md_credentials_t*) = cred;
    }
    
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, result->status, d->p, 
                  "%s: init_base driver", d->md->name);
    return result->status;
}

static apr_status_t acme_driver_init(md_proto_driver_t *d, md_result_t *result)
{
    md_acme_driver_t *ad;
    int dis_http, dis_https, dis_alpn_acme, dis_dns;
    const char *challenge;

    acme_driver_preload_init(d, result);
    md_result_set(result, APR_SUCCESS, NULL);
    if (APR_SUCCESS != result->status) goto leave;
    
    ad = d->baton;

    /* We can only support challenges if the server is reachable from the outside
     * via port 80 and/or 443. These ports might be mapped for httpd to something
     * else, but a mapping needs to exist. */
    challenge = apr_table_get(d->env, MD_KEY_CHALLENGE); 
    if (challenge) {
        APR_ARRAY_PUSH(ad->ca_challenges, const char*) = apr_pstrdup(d->p, challenge);
    }
    else if (d->md->ca_challenges && d->md->ca_challenges->nelts > 0) {
        /* pre-configured set for this managed domain */
        apr_array_cat(ad->ca_challenges, d->md->ca_challenges);
    }
    else {
        /* free to chose. Add all we support and see what we get offered */
        APR_ARRAY_PUSH(ad->ca_challenges, const char*) = MD_AUTHZ_TYPE_TLSALPN01;
        APR_ARRAY_PUSH(ad->ca_challenges, const char*) = MD_AUTHZ_TYPE_HTTP01;
        APR_ARRAY_PUSH(ad->ca_challenges, const char*) = MD_AUTHZ_TYPE_DNS01;

        if (!d->can_http && !d->can_https 
            && md_array_str_index(ad->ca_challenges, MD_AUTHZ_TYPE_DNS01, 0, 0) < 0) {
            md_result_printf(result, APR_EGENERAL,
                             "the server seems neither reachable via http (port 80) nor https (port 443). "
                             "Please look at the MDPortMap configuration directive on how to correct this. "
                             "The ACME protocol needs at least one of those so the CA can talk to the server "
                             "and verify a domain ownership. Alternatively, you may configure support "
                             "for the %s challenge directive.", MD_AUTHZ_TYPE_DNS01);
            goto leave;
        }

        dis_http = dis_https = dis_alpn_acme = dis_dns = 0;
        if (!d->can_http && md_array_str_index(ad->ca_challenges, MD_AUTHZ_TYPE_HTTP01, 0, 1) >= 0) {
            ad->ca_challenges = md_array_str_remove(d->p, ad->ca_challenges, MD_AUTHZ_TYPE_HTTP01, 0);
            dis_http = 1;
        }
        if (!d->can_https && md_array_str_index(ad->ca_challenges, MD_AUTHZ_TYPE_TLSALPN01, 0, 1) >= 0) {
            ad->ca_challenges = md_array_str_remove(d->p, ad->ca_challenges, MD_AUTHZ_TYPE_TLSALPN01, 0);
            dis_https = 1;
        }
        if (apr_is_empty_array(d->md->acme_tls_1_domains)
            && md_array_str_index(ad->ca_challenges, MD_AUTHZ_TYPE_TLSALPN01, 0, 1) >= 0) {
            ad->ca_challenges = md_array_str_remove(d->p, ad->ca_challenges, MD_AUTHZ_TYPE_TLSALPN01, 0);
            dis_alpn_acme = 1;
        }
        if (!apr_table_get(d->env, MD_KEY_CMD_DNS01)
            && NULL == d->md->dns01_cmd
            && md_array_str_index(ad->ca_challenges, MD_AUTHZ_TYPE_DNS01, 0, 1) >= 0) {
            ad->ca_challenges = md_array_str_remove(d->p, ad->ca_challenges, MD_AUTHZ_TYPE_DNS01, 0);
            dis_dns = 1;
        }

        if (apr_is_empty_array(ad->ca_challenges)) {
            md_result_printf(result, APR_EGENERAL, 
                             "None of the ACME challenge methods configured for this domain are suitable.%s%s%s%s",
                             dis_http? " The http: challenge 'http-01' is disabled because the server seems not reachable on public port 80." : "",
                             dis_https? " The https: challenge 'tls-alpn-01' is disabled because the server seems not reachable on public port 443." : "",
                             dis_alpn_acme? " The https: challenge 'tls-alpn-01' is disabled because the Protocols configuration does not include the 'acme-tls/1' protocol." : "",
                             dis_dns? " The DNS challenge 'dns-01' is disabled because the directive 'MDChallengeDns01' is not configured." : ""
                             );
            goto leave;
        }
    }

    md_result_printf(result, 0, "MDomain %s initialized with support for ACME challenges %s",
              d->md->name, apr_array_pstrcat(d->p, ad->ca_challenges, ' '));

leave:    
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, result->status, d->p, "%s: init driver", d->md->name);
    return result->status;
}

/**************************************************************************************************/
/* ACME staging */

static apr_status_t load_missing_creds(md_proto_driver_t *d)
{
    md_acme_driver_t *ad = d->baton;
    md_credentials_t *cred;
    apr_array_header_t *chain;
    int i, complete;
    apr_status_t rv;
    
    complete = 1;
    for (i = 0; i < ad->creds->nelts; ++i) {
        rv = APR_SUCCESS;
        cred = APR_ARRAY_IDX(ad->creds, i, md_credentials_t*);
        if (!cred->pkey) {
            rv = md_pkey_load(d->store, MD_SG_STAGING, d->md->name, cred->spec, &cred->pkey, d->p);
        }
        if (APR_SUCCESS == rv && md_array_is_empty(cred->chain)) {
            rv = md_pubcert_load(d->store, MD_SG_STAGING, d->md->name, cred->spec, &chain, d->p);
            if (APR_SUCCESS == rv) {
                apr_array_cat(cred->chain, chain);
            }
        }
        if (APR_SUCCESS == rv) {
            md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, 0, d->p, "%s: credentials staged for %s certificate", 
                          d->md->name, md_pkey_spec_name(cred->spec));
        }
        else {
            complete = 0;
        }
    }
    return complete? APR_SUCCESS : APR_EAGAIN;
}

static apr_status_t acme_renew(md_proto_driver_t *d, md_result_t *result)
{
    md_acme_driver_t *ad = d->baton;
    int reset_staging = d->reset;
    apr_status_t rv = APR_SUCCESS;
    apr_time_t now, t, t2;
    md_credentials_t *cred;
    const char *ca_effective = NULL;
    char ts[APR_RFC822_DATE_LEN];
    int i, first = 0;

    if (!d->md->ca_urls || d->md->ca_urls->nelts <= 0) {
        /* No CA defined? This is checked in several other places, but lets be sure */
        md_result_printf(result, APR_INCOMPLETE,
            "The managed domain %s is missing MDCertificateAuthority", d->md->name);
        goto out;
    }

    /* When not explicitly told to reset, we check the existing data. If
     * it is incomplete or old, we trigger the reset for a clean start. */
    if (!reset_staging) {
        md_result_activity_setn(result, "Checking staging area");
        rv = md_load(d->store, MD_SG_STAGING, d->md->name, &ad->md, d->p);
        if (APR_SUCCESS == rv) {
            /* So, we have a copy in staging, but is it a recent or an old one? */
            if (md_is_newer(d->store, MD_SG_DOMAINS, MD_SG_STAGING, d->md->name, d->p)) {
                reset_staging = 1;
            }
        }
        else if (APR_STATUS_IS_ENOENT(rv)) {
            reset_staging = 1;
            rv = APR_SUCCESS;
        }
    }

    /* What CA are we using this time? */
    if (ad->md && ad->md->ca_effective) {
        /* There was one chosen on the previous run. Do we stick to it? */
        ca_effective = ad->md->ca_effective;
        if (d->md->ca_urls->nelts > 1 && d->attempt >= d->retry_failover) {
            /* We have more than one CA to choose from and this is the (at least)
             * third attempt with the same CA. Let's switch to the next one. */
            int last_idx = md_array_str_index(d->md->ca_urls, ca_effective, 0, 1);
            if (last_idx >= 0) {
                int next_idx = (last_idx+1) % d->md->ca_urls->nelts;
                ca_effective = APR_ARRAY_IDX(d->md->ca_urls, next_idx, const char*);
            }
            else {
                /* not part of current configuration? */
                ca_effective = NULL;
            }
            /* switching CA means we need to wipe the staging area */
            reset_staging = 1;
        }
    }

    if (!ca_effective) {
        /* None chosen yet, pick the first one configured */
        ca_effective = APR_ARRAY_IDX(d->md->ca_urls, 0, const char*);
    }

    if (md_log_is_level(d->p, MD_LOG_DEBUG)) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, "%s: staging started, "
                      "state=%d, attempt=%d, acme=%s, challenges='%s'",
                      d->md->name, d->md->state, d->attempt, ca_effective,
                      apr_array_pstrcat(d->p, ad->ca_challenges, ' '));
    }

    if (reset_staging) {
        md_result_activity_setn(result, "Resetting staging area");
        /* reset the staging area for this domain */
        rv = md_store_purge(d->store, d->p, MD_SG_STAGING, d->md->name);
        md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, rv, d->p, 
                      "%s: reset staging area", d->md->name);
        if (APR_SUCCESS != rv && !APR_STATUS_IS_ENOENT(rv)) {
            md_result_printf(result, rv, "resetting staging area");
            goto out;
        }
        rv = APR_SUCCESS;
        ad->md = NULL;
        ad->order = NULL;
    }
    
    md_result_activity_setn(result, "Assessing current status");
    if (ad->md && ad->md->state == MD_S_MISSING_INFORMATION) {
        /* ToS agreement is missing. It makes no sense to drive this MD further */
        md_result_printf(result, APR_INCOMPLETE, 
            "The managed domain %s is missing required information", d->md->name);
        goto out;
    }
    
    if (ad->md && APR_SUCCESS == load_missing_creds(d)) {
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, "%s: all credentials staged", d->md->name);
        goto ready;
    }
    
    /* Need to renew */
    if (!ad->md || !md_array_str_eq(ad->md->ca_urls, d->md->ca_urls, 1)) {
        md_result_activity_printf(result, "Resetting staging for %s", d->md->name);
        /* re-initialize staging */
        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, "%s: setup staging", d->md->name);
        md_store_purge(d->store, d->p, MD_SG_STAGING, d->md->name);
        ad->md = md_copy(d->p, d->md);
        ad->md->ca_effective = ca_effective;
        ad->md->ca_account = NULL;
        ad->order = NULL;
        rv = md_save(d->store, d->p, MD_SG_STAGING, ad->md, 0);
        if (APR_SUCCESS != rv) {
            md_result_printf(result, rv, "Saving MD information in staging area.");
            md_result_log(result, MD_LOG_ERR);
            goto out;
        }
    }
    if (!ad->domains) {
        ad->domains = md_dns_make_minimal(d->p, ad->md->domains);
    }
    
    md_result_activity_printf(result, "Contacting ACME server for %s at %s",
                              d->md->name, ca_effective);
    if (APR_SUCCESS != (rv = md_acme_create(&ad->acme, d->p, ca_effective,
                                            d->proxy_url, d->ca_file))) {
        md_result_printf(result, rv, "setup ACME communications");
        md_result_log(result, MD_LOG_ERR);
        goto out;
    }
    if (APR_SUCCESS != (rv = md_acme_setup(ad->acme, result))) {
        md_result_log(result, MD_LOG_ERR);
        goto out;
    }

    if (APR_SUCCESS != load_missing_creds(d)) {
        for (i = 0; i < ad->creds->nelts; ++i) {
            ad->cred = APR_ARRAY_IDX(ad->creds, i, md_credentials_t*);
            if (!ad->cred->pkey || md_array_is_empty(ad->cred->chain)) {
                md_result_activity_printf(result, "Driving ACME to renew %s certificate for %s", 
                                          md_pkey_spec_name(ad->cred->spec),d->md->name);
                /* The process of setting up challenges and verifying domain
                 * names differs between ACME versions. */
                switch (MD_ACME_VERSION_MAJOR(ad->acme->version)) {
                    case 1:
                        md_result_printf(result, APR_EINVAL,
                            "ACME server speaks version 1, an obsolete version of the ACME "
                            "protocol that is no longer supported.");
                        rv = result->status;
                        break;
                    default:
                        /* In principle, we only know ACME version 2. But we assume
                        that a new protocol which announces a directory with all members
                        from version 2 will act backward compatible.
                        This is, of course, an assumption...
                        */
                        rv = md_acmev2_drive_renew(ad, d, result);
                        break;
                }
                if (APR_SUCCESS != rv) goto out;
                
                if (md_array_is_empty(ad->cred->chain) || ad->chain_up_link) {
                    md_result_activity_printf(result, "Retrieving %s certificate chain for %s", 
                                              md_pkey_spec_name(ad->cred->spec), d->md->name);
                    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, 
                                  "%s: retrieving %s certificate chain", 
                                  d->md->name, md_pkey_spec_name(ad->cred->spec));
                    rv = ad_chain_retrieve(d);
                    if (APR_SUCCESS != rv) {
                        md_result_printf(result, rv, "Unable to retrieve %s certificate chain.", 
                                         md_pkey_spec_name(ad->cred->spec));
                        goto out;
                    }
                    
                    if (!md_array_is_empty(ad->cred->chain)) {

                        if (!ad->cred->pkey) {
                            rv = md_pkey_load(d->store, MD_SG_STAGING, d->md->name, ad->cred->spec, &ad->cred->pkey, d->p);
                            if (APR_SUCCESS != rv) {
                                md_result_printf(result, rv, "Loading the private key.");
                                goto out;
                            }
                        }

                        if (ad->cred->pkey) {
                            rv = md_check_cert_and_pkey(ad->cred->chain, ad->cred->pkey);
                            if (APR_SUCCESS != rv) {
                                md_result_printf(result, rv, "Certificate and private key do not match.");

                                /* Delete the order */
                                md_acme_order_purge(d->store, d->p, MD_SG_STAGING, d->md, d->env);

                                goto out;
                            }
                        }

                        rv = md_pubcert_save(d->store, d->p, MD_SG_STAGING, d->md->name, 
                                             ad->cred->spec, ad->cred->chain, 0);
                        if (APR_SUCCESS != rv) {
                            md_result_printf(result, rv, "Saving new %s certificate chain.", 
                                             md_pkey_spec_name(ad->cred->spec));
                            goto out;
                        }
                    }
                }
                
                /* Clean up the order, so the next pkey spec sets up a new one */
                md_acme_order_purge(d->store, d->p, MD_SG_STAGING, d->md, d->env);
            }
        }
    }
    
    
    /* As last step, cleanup any order we created so that challenge data
     * may be removed asap. */
    md_acme_order_purge(d->store, d->p, MD_SG_STAGING, d->md, d->env);
    
    /* first time this job ran through */
    first = 1;    
ready:
    md_result_activity_setn(result, NULL);
    /* we should have the complete cert chain now */
    assert(APR_SUCCESS == load_missing_creds(d));
    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, rv, d->p, 
                  "%s: certificates ready, activation delay set to %s", 
                  d->md->name, md_duration_format(d->p, d->activation_delay));
    
    /* determine when it should be activated */
    t = apr_time_now();
    for (i = 0; i < ad->creds->nelts; ++i) {
        cred = APR_ARRAY_IDX(ad->creds, i, md_credentials_t*);
        t2 = md_cert_get_not_before(APR_ARRAY_IDX(cred->chain, 0, md_cert_t*));
        if (t2 > t) t = t2;
    }
    md_result_delay_set(result, t);

    /* If the existing MD is complete and un-expired, delay the activation
     * to 24 hours after new cert is valid (if there is enough time left), so
     * that cients with skewed clocks do not see a problem. */
    now = apr_time_now();
    if (d->md->state == MD_S_COMPLETE) {
        apr_time_t valid_until, delay_activation;
        
        md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, rv, d->p, 
                      "%s: state is COMPLETE, checking existing certificates", d->md->name);
        valid_until = md_reg_valid_until(d->reg, d->md, d->p);
        if (d->activation_delay < 0) {
            /* special simulation for test case */
            if (first) {
                md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, d->p, 
                              "%s: delay ready_at to now+1s", d->md->name);
                md_result_delay_set(result, apr_time_now() + apr_time_from_sec(1));
            }
        }
        else if (valid_until > now) {            
            delay_activation = d->activation_delay;
            if (delay_activation > (valid_until - now)) {
                delay_activation = (valid_until - now);
            }
            md_result_delay_set(result, result->ready_at + delay_activation);
        }
    }
    
    /* There is a full set staged, to be loaded */
    apr_rfc822_date(ts, result->ready_at);
    if (result->ready_at > now) {
        md_result_printf(result, APR_SUCCESS, 
            "The certificate for the managed domain has been renewed successfully and can "
            "be used from %s on.", ts);
    }
    else {
        md_result_printf(result, APR_SUCCESS, 
            "The certificate for the managed domain has been renewed successfully and can "
            "be used (valid since %s). A graceful server restart now is recommended.", ts);
    }

out:
    return rv;
}

static apr_status_t acme_driver_renew(md_proto_driver_t *d, md_result_t *result)
{
    apr_status_t rv;

    rv = acme_renew(d, result);
    md_result_log(result, MD_LOG_DEBUG);
    return rv;
}

/**************************************************************************************************/
/* ACME preload */

static apr_status_t acme_preload(md_proto_driver_t *d, md_store_group_t load_group, 
                                 const char *name, md_result_t *result) 
{
    apr_status_t rv;
    md_pkey_t *acct_key;
    md_t *md;
    md_pkey_spec_t *pkspec;
    md_credentials_t *creds;
    apr_array_header_t *all_creds;
    struct md_acme_acct_t *acct;
    const char *id;
    int i;

    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, d->p, "%s: preload start", name);
    /* Load data from MD_SG_STAGING and save it into "load_group".
     * This serves several purposes:
     *  1. It's a format check on the input data. 
     *  2. We write back what we read, creating data with our own access permissions
     *  3. We ignore any other accumulated data in STAGING
     *  4. Once "load_group" is complete an ok, we can swap/archive groups with a rename
     *  5. Reading/Writing the data will apply/remove any group specific data encryption.
     */
    if (APR_SUCCESS != (rv = md_load(d->store, MD_SG_STAGING, name, &md, d->p))) {
        md_result_set(result, rv, "loading staged md.json");
        goto leave;
    }
    if (!md->ca_effective) {
        rv = APR_ENOENT;
        md_result_set(result, rv, "effective CA url not set");
        goto leave;
    }

    all_creds = apr_array_make(d->p, 5, sizeof(md_credentials_t*));
    for (i = 0; i < md_pkeys_spec_count(md->pks); ++i) {
        pkspec = md_pkeys_spec_get(md->pks, i);
        if (APR_SUCCESS != (rv = md_creds_load(d->store, MD_SG_STAGING, name, pkspec, &creds, d->p))) {
            md_result_printf(result, rv, "loading staged credentials #%d", i);
            goto leave;
        }
        if (!creds->chain) {
            rv = APR_ENOENT;
            md_result_printf(result, rv, "no certificate in staged credentials #%d", i);
            goto leave;
        }
        if (APR_SUCCESS != (rv = md_check_cert_and_pkey(creds->chain, creds->pkey))) {
            md_result_printf(result, rv, "certificate and private key do not match in staged credentials #%d", i);
            goto leave;
        }
        APR_ARRAY_PUSH(all_creds, md_credentials_t*) = creds;
    }
    
    /* See if staging holds a new or modified account data */
    rv = md_acme_acct_load(&acct, &acct_key, d->store, MD_SG_STAGING, name, d->p);
    if (APR_STATUS_IS_ENOENT(rv)) {
        acct = NULL;
        acct_key = NULL;
        rv = APR_SUCCESS;
    }
    else if (APR_SUCCESS != rv) {
        md_result_set(result, rv, "loading staged account");
        goto leave;
    }

    md_result_activity_setn(result, "purging order information");
    md_acme_order_purge(d->store, d->p, MD_SG_STAGING, md, d->env);

    md_result_activity_setn(result, "purging store tmp space");
    rv = md_store_purge(d->store, d->p, load_group, name);
    if (APR_SUCCESS != rv) {
        md_result_set(result, rv, NULL);
        goto leave;
    }
    
    if (acct) {
        md_acme_t *acme;

        /* We may have STAGED the same account several times. This happens when
         * several MDs are renewed at once and need a new account. They will all store
         * the new account in their own STAGING area. By checking for accounts with
         * the same url, we save them all into a single one.
         */
        md_result_activity_setn(result, "saving staged account");
        id = md->ca_account;
        if (!id) {
            rv = md_acme_acct_id_for_md(&id, d->store, MD_SG_ACCOUNTS, md, d->p);
            if (APR_STATUS_IS_ENOENT(rv)) {
                id = NULL;
            }
            else if (APR_SUCCESS != rv) {
                md_result_set(result, rv, "error searching for existing account by url");
                goto leave;
            }
        }
        
        if (APR_SUCCESS != (rv = md_acme_create(&acme, d->p, md->ca_effective,
                                                d->proxy_url, d->ca_file))) {
            md_result_set(result, rv, "error setting up acme");
            goto leave;
        }
        
        if (APR_SUCCESS != (rv = md_acme_acct_save(d->store, d->p, acme, &id, acct, acct_key))) {
            md_result_set(result, rv, "error saving account");
            goto leave;
        }
        md->ca_account = id;
    }
    else if (!md->ca_account) {
        /* staging reused another account and did not create a new one. find
         * the account, if it is already there */
        rv = md_acme_acct_id_for_md(&id, d->store, MD_SG_ACCOUNTS, md, d->p);
        if (APR_SUCCESS == rv) {
            md->ca_account = id;
        }
    }
    
    md_result_activity_setn(result, "saving staged md/privkey/pubcert");
    if (APR_SUCCESS != (rv = md_save(d->store, d->p, load_group, md, 1))) {
        md_result_set(result, rv, "writing md.json");
        goto leave;
    }

    for (i = 0; i < all_creds->nelts; ++i) {
        creds = APR_ARRAY_IDX(all_creds, i, md_credentials_t*);
        if (APR_SUCCESS != (rv = md_creds_save(d->store, d->p, load_group, name, creds, 1))) {
            md_result_printf(result, rv, "writing credentials #%d", i);
            goto leave;
        }
    }
    
    md_result_set(result, APR_SUCCESS, "saved staged data successfully");
    
leave:
    md_result_log(result, MD_LOG_DEBUG);
    return rv;
}

static apr_status_t acme_driver_preload(md_proto_driver_t *d, 
                                        md_store_group_t group, md_result_t *result)
{
    apr_status_t rv;

    rv = acme_preload(d, group, d->md->name, result);
    md_result_log(result, MD_LOG_DEBUG);
    return rv;
}

static apr_status_t acme_complete_md(md_t *md, apr_pool_t *p)
{
    (void)p;
    if (!md->ca_urls || apr_is_empty_array(md->ca_urls)) {
        md->ca_urls = apr_array_make(p, 3, sizeof(const char *));
        APR_ARRAY_PUSH(md->ca_urls, const char*) = MD_ACME_DEF_URL;
    }
    return APR_SUCCESS;
}

static md_proto_t ACME_PROTO = {
    MD_PROTO_ACME, acme_driver_init, acme_driver_renew, 
    acme_driver_preload_init, acme_driver_preload,
    acme_complete_md,
};
 
apr_status_t md_acme_protos_add(apr_hash_t *protos, apr_pool_t *p)
{
    (void)p;
    apr_hash_set(protos, MD_PROTO_ACME, sizeof(MD_PROTO_ACME)-1, &ACME_PROTO);
    return APR_SUCCESS;
}