Adding upstream version 2.4.57.upstream/2.4.57

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 697 insertions, 0 deletions

diff --git a/modules/md/md_acme_authz.c b/modules/md/md_acme_authz.c
new file mode 100644
index 0000000..a55804e
--- /dev/null
+++ b/modules/md/md_acme_authz.c
@@ -0,0 +1,697 @@
+/* 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 <stdio.h>
+
+#include <apr_lib.h>
+#include <apr_buckets.h>
+#include <apr_file_info.h>
+#include <apr_file_io.h>
+#include <apr_fnmatch.h>
+#include <apr_hash.h>
+#include <apr_strings.h>
+#include <apr_tables.h>
+
+#include "md.h"
+#include "md_crypt.h"
+#include "md_json.h"
+#include "md_http.h"
+#include "md_log.h"
+#include "md_jws.h"
+#include "md_result.h"
+#include "md_store.h"
+#include "md_util.h"
+
+#include "md_acme.h"
+#include "md_acme_authz.h"
+
+md_acme_authz_t *md_acme_authz_create(apr_pool_t *p)
+{
+    md_acme_authz_t *authz;
+    authz = apr_pcalloc(p, sizeof(*authz));
+    
+    return authz;
+}
+
+/**************************************************************************************************/
+/* Register a new authorization */
+
+typedef struct {
+    size_t index;
+    const char *type;
+    const char *uri;
+    const char *token;
+    const char *key_authz;
+} md_acme_authz_cha_t;
+
+typedef struct {
+    apr_pool_t *p;
+    md_acme_t *acme;
+    const char *domain;
+    md_acme_authz_t *authz;
+    md_acme_authz_cha_t *challenge;
+} authz_req_ctx;
+
+static void authz_req_ctx_init(authz_req_ctx *ctx, md_acme_t *acme, 
+                               const char *domain, md_acme_authz_t *authz, apr_pool_t *p)
+{
+    memset(ctx, 0, sizeof(*ctx));
+    ctx->p = p;
+    ctx->acme = acme;
+    ctx->domain = domain;
+    ctx->authz = authz;
+}
+
+/**************************************************************************************************/
+/* Update an existing authorization */
+
+apr_status_t md_acme_authz_retrieve(md_acme_t *acme, apr_pool_t *p, const char *url, 
+                                    md_acme_authz_t **pauthz)
+{
+    md_acme_authz_t *authz;
+    apr_status_t rv;
+    
+    authz = apr_pcalloc(p, sizeof(*authz));
+    authz->url = apr_pstrdup(p, url);
+    rv = md_acme_authz_update(authz, acme, p);
+    
+    *pauthz = (APR_SUCCESS == rv)? authz : NULL;
+    return rv;
+}
+
+typedef struct {
+    apr_pool_t *p;
+    md_acme_authz_t *authz;
+} error_ctx_t;
+
+static int copy_challenge_error(void *baton, size_t index, md_json_t *json)
+{
+    error_ctx_t *ctx = baton;
+    
+    (void)index;
+    if (md_json_has_key(json, MD_KEY_ERROR, NULL)) {
+        ctx->authz->error_type = md_json_dups(ctx->p, json, MD_KEY_ERROR, MD_KEY_TYPE, NULL);
+        ctx->authz->error_detail = md_json_dups(ctx->p, json, MD_KEY_ERROR, MD_KEY_DETAIL, NULL);
+        ctx->authz->error_subproblems = md_json_dupj(ctx->p, json, MD_KEY_ERROR, MD_KEY_SUBPROBLEMS, NULL);
+    }
+    return 1;
+}
+
+apr_status_t md_acme_authz_update(md_acme_authz_t *authz, md_acme_t *acme, apr_pool_t *p)
+{
+    md_json_t *json;
+    const char *s, *err;
+    md_log_level_t log_level;
+    apr_status_t rv;
+    error_ctx_t ctx;
+    
+    assert(acme);
+    assert(acme->http);
+    assert(authz);
+    assert(authz->url);
+
+    authz->state = MD_ACME_AUTHZ_S_UNKNOWN;
+    json = NULL;
+    authz->error_type = authz->error_detail = NULL;
+    authz->error_subproblems = NULL;
+    err = "unable to parse response";
+    log_level = MD_LOG_ERR;
+    
+    if (APR_SUCCESS == (rv = md_acme_get_json(&json, acme, authz->url, p))
+        && (s = md_json_gets(json, MD_KEY_STATUS, NULL))) {
+            
+        authz->domain = md_json_gets(json, MD_KEY_IDENTIFIER, MD_KEY_VALUE, NULL); 
+        authz->resource = json;
+        if (!strcmp(s, "pending")) {
+            authz->state = MD_ACME_AUTHZ_S_PENDING;
+            err = "challenge 'pending'";
+            log_level = MD_LOG_DEBUG;
+        }
+        else if (!strcmp(s, "valid")) {
+            authz->state = MD_ACME_AUTHZ_S_VALID;
+            err = "challenge 'valid'";
+            log_level = MD_LOG_DEBUG;
+        }
+        else if (!strcmp(s, "invalid")) {
+            ctx.p = p;
+            ctx.authz = authz;
+            authz->state = MD_ACME_AUTHZ_S_INVALID;
+            md_json_itera(copy_challenge_error, &ctx, json, MD_KEY_CHALLENGES, NULL);
+            err = "challenge 'invalid'";
+        }
+    }
+
+    if (json && authz->state == MD_ACME_AUTHZ_S_UNKNOWN) {
+        err = "unable to understand response";
+        rv = APR_EINVAL;
+    }
+    
+    if (md_log_is_level(p, log_level)) {
+        md_log_perror(MD_LOG_MARK, log_level, rv, p, "ACME server authz: %s for %s at %s. "
+                      "Exact response was: %s", err, authz->domain, authz->url,
+                      json? md_json_writep(json, p, MD_JSON_FMT_COMPACT) : "not available");
+    }
+    
+    return rv;
+}
+
+/**************************************************************************************************/
+/* response to a challenge */
+
+static md_acme_authz_cha_t *cha_from_json(apr_pool_t *p, size_t index, md_json_t *json)
+{
+    md_acme_authz_cha_t * cha;
+    
+    cha = apr_pcalloc(p, sizeof(*cha));
+    cha->index = index;
+    cha->type = md_json_dups(p, json, MD_KEY_TYPE, NULL);
+    if (md_json_has_key(json, MD_KEY_URL, NULL)) { /* ACMEv2 */
+        cha->uri = md_json_dups(p, json, MD_KEY_URL, NULL);
+    }
+    else {                                         /* ACMEv1 */
+        cha->uri = md_json_dups(p, json, MD_KEY_URI, NULL);
+    }
+    cha->token = md_json_dups(p, json, MD_KEY_TOKEN, NULL);
+    cha->key_authz = md_json_dups(p, json, MD_KEY_KEYAUTHZ, NULL);
+
+    return cha;
+}
+
+static apr_status_t on_init_authz_resp(md_acme_req_t *req, void *baton)
+{
+    md_json_t *jpayload;
+
+    (void)baton;
+    jpayload = md_json_create(req->p);
+    return md_acme_req_body_init(req, jpayload);
+} 
+
+static apr_status_t authz_http_set(md_acme_t *acme, apr_pool_t *p, const apr_table_t *hdrs, 
+                                   md_json_t *body, void *baton)
+{
+    authz_req_ctx *ctx = baton;
+    
+    (void)acme;
+    (void)p;
+    (void)hdrs;
+    (void)body;
+    md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, 0, ctx->p, "updated authz %s", ctx->authz->url);
+    return APR_SUCCESS;
+}
+
+static apr_status_t setup_key_authz(md_acme_authz_cha_t *cha, md_acme_authz_t *authz,
+                                    md_acme_t *acme, apr_pool_t *p, int *pchanged)
+{
+    const char *thumb64, *key_authz;
+    apr_status_t rv;
+    
+    (void)authz;
+    assert(cha);
+    assert(cha->token);
+    
+    *pchanged = 0;
+    if (APR_SUCCESS == (rv = md_jws_pkey_thumb(&thumb64, p, acme->acct_key))) {
+        key_authz = apr_psprintf(p, "%s.%s", cha->token, thumb64);
+        if (cha->key_authz) {
+            if (strcmp(key_authz, cha->key_authz)) {
+                /* Hu? Did the account change key? */
+                cha->key_authz = NULL;
+            }
+        }
+        if (!cha->key_authz) {
+            cha->key_authz = key_authz;
+            *pchanged = 1;
+        }
+    }
+    return rv;
+}
+
+static apr_status_t cha_http_01_setup(md_acme_authz_cha_t *cha, md_acme_authz_t *authz,
+                                      md_acme_t *acme, md_store_t *store, 
+                                      md_pkeys_spec_t *key_specs,
+                                      apr_array_header_t *acme_tls_1_domains, const md_t *md,
+                                      apr_table_t *env, md_result_t *result, apr_pool_t *p)
+{
+    const char *data;
+    apr_status_t rv;
+    int notify_server;
+    
+    (void)key_specs;
+    (void)env;
+    (void)acme_tls_1_domains;
+    (void)md;
+
+    if (APR_SUCCESS != (rv = setup_key_authz(cha, authz, acme, p, &notify_server))) {
+        goto out;
+    }
+    
+    rv = md_store_load(store, MD_SG_CHALLENGES, authz->domain, MD_FN_HTTP01,
+                       MD_SV_TEXT, (void**)&data, p);
+    if ((APR_SUCCESS == rv && strcmp(cha->key_authz, data)) || APR_STATUS_IS_ENOENT(rv)) {
+        const char *content = apr_psprintf(p, "%s\n", cha->key_authz);
+        rv = md_store_save(store, p, MD_SG_CHALLENGES, authz->domain, MD_FN_HTTP01,
+                           MD_SV_TEXT, (void*)content, 0);
+        notify_server = 1;
+    }
+    
+    if (APR_SUCCESS == rv && notify_server) {
+        authz_req_ctx ctx;
+        const char *event;
+
+        /* Raise event that challenge data has been set up before we tell the
+           ACME server. Clusters might want to distribute it. */
+        event = apr_psprintf(p, "challenge-setup:%s:%s", MD_AUTHZ_TYPE_HTTP01, authz->domain);
+        rv = md_result_raise(result, event, p);
+        if (APR_SUCCESS != rv) {
+            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p,
+                          "%s: event '%s' failed. aborting challenge setup",
+                          authz->domain, event);
+            goto out;
+        }
+        /* challenge is setup or was changed from previous data, tell ACME server
+         * so it may (re)try verification */        
+        authz_req_ctx_init(&ctx, acme, NULL, authz, p);
+        ctx.challenge = cha;
+        rv = md_acme_POST(acme, cha->uri, on_init_authz_resp, authz_http_set, NULL, NULL, &ctx);
+    }
+out:
+    return rv;
+}
+
+void tls_alpn01_fnames(apr_pool_t *p, md_pkey_spec_t *kspec, char **keyfn, char **certfn )
+{
+    *keyfn  = apr_pstrcat(p, "acme-tls-alpn-01-", md_pkey_filename(kspec, p), NULL);
+    *certfn = apr_pstrcat(p, "acme-tls-alpn-01-", md_chain_filename(kspec, p), NULL);
+}
+
+static apr_status_t cha_tls_alpn_01_setup(md_acme_authz_cha_t *cha, md_acme_authz_t *authz, 
+                                          md_acme_t *acme, md_store_t *store, 
+                                          md_pkeys_spec_t *key_specs,
+                                          apr_array_header_t *acme_tls_1_domains, const md_t *md,
+                                          apr_table_t *env, md_result_t *result, apr_pool_t *p)
+{
+    const char *acme_id, *token;
+    apr_status_t rv;
+    int notify_server;
+    md_data_t data;
+    int i;
+
+    (void)env;
+    (void)md;
+    if (md_array_str_index(acme_tls_1_domains, authz->domain, 0, 0) < 0) {
+        rv = APR_ENOTIMPL;
+        if (acme_tls_1_domains->nelts) {
+            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, p,
+                          "%s: protocol 'acme-tls/1' seems not enabled for this domain, "
+                          "but is enabled for other associated domains. "
+                          "Continuing with fingers crossed.", authz->domain);
+        }
+        else {
+            md_log_perror(MD_LOG_MARK, MD_LOG_INFO, 0, p,
+                          "%s: protocol 'acme-tls/1' seems not enabled for this or "
+                          "any other associated domain. Not attempting challenge "
+                          "type tls-alpn-01.", authz->domain);
+            goto out;
+        }
+    }
+    if (APR_SUCCESS != (rv = setup_key_authz(cha, authz, acme, p, &notify_server))) {
+        goto out;
+    }
+
+    /* Create a "tls-alpn-01" certificate for the domain we want to authenticate.
+     * The server will need to answer a TLS connection with SNI == authz->domain
+     * and ALPN protocol "acme-tls/1" with this certificate.
+     */
+    md_data_init_str(&data, cha->key_authz);
+    rv = md_crypt_sha256_digest_hex(&token, p, &data);
+    if (APR_SUCCESS != rv) {
+        md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, p, "%s: create tls-alpn-01 validation token",
+                      authz->domain);
+        goto out;
+    }
+    acme_id = apr_psprintf(p, "critical,DER:04:20:%s", token);
+
+    /* Each configured key type must be generated to ensure:
+     * that any fallback certs already given to mod_ssl are replaced.
+     * We expect that the validation client (at the CA) can deal with at
+     * least one of them.
+     */
+
+    for (i = 0; i < md_pkeys_spec_count(key_specs); ++i) {
+        char *kfn, *cfn;
+        md_cert_t *cha_cert;
+        md_pkey_t *cha_key;
+        md_pkey_spec_t *key_spec;
+
+        key_spec = md_pkeys_spec_get(key_specs, i);
+        tls_alpn01_fnames(p, key_spec, &kfn, &cfn);
+
+        rv = md_store_load(store, MD_SG_CHALLENGES, authz->domain, cfn,
+                           MD_SV_CERT, (void**)&cha_cert, p);
+        if ((APR_SUCCESS == rv && !md_cert_covers_domain(cha_cert, authz->domain))
+            || APR_STATUS_IS_ENOENT(rv)) {
+            if (APR_SUCCESS != (rv = md_pkey_gen(&cha_key, p, key_spec))) {
+                md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, p, "%s: create tls-alpn-01 %s challenge key",
+                              authz->domain, md_pkey_spec_name(key_spec));
+                goto out;
+            }
+
+            if (APR_SUCCESS != (rv = md_cert_make_tls_alpn_01(&cha_cert, authz->domain, acme_id, cha_key,
+                                                              apr_time_from_sec(7 * MD_SECS_PER_DAY), p))) {
+                md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, p, "%s: create tls-alpn-01 %s challenge cert",
+                              authz->domain, md_pkey_spec_name(key_spec));
+                goto out;
+            }
+        
+            if (APR_SUCCESS == (rv = md_store_save(store, p, MD_SG_CHALLENGES, authz->domain, kfn,
+                                                   MD_SV_PKEY, (void*)cha_key, 0))) {
+                rv = md_store_save(store, p, MD_SG_CHALLENGES, authz->domain, cfn,
+                                   MD_SV_CERT, (void*)cha_cert, 0);
+            }
+            ++notify_server;
+        }
+    }
+    
+    if (APR_SUCCESS == rv && notify_server) {
+        authz_req_ctx ctx;
+        const char *event;
+
+        /* Raise event that challenge data has been set up before we tell the
+           ACME server. Clusters might want to distribute it. */
+        event = apr_psprintf(p, "challenge-setup:%s:%s", MD_AUTHZ_TYPE_TLSALPN01, authz->domain);
+        rv = md_result_raise(result, event, p);
+        if (APR_SUCCESS != rv) {
+            md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p,
+                          "%s: event '%s' failed. aborting challenge setup",
+                          authz->domain, event);
+            goto out;
+        }
+        /* challenge is setup or was changed from previous data, tell ACME server
+         * so it may (re)try verification */        
+        authz_req_ctx_init(&ctx, acme, NULL, authz, p);
+        ctx.challenge = cha;
+        rv = md_acme_POST(acme, cha->uri, on_init_authz_resp, authz_http_set, NULL, NULL, &ctx);
+    }
+out:    
+    return rv;
+}
+
+static apr_status_t cha_dns_01_setup(md_acme_authz_cha_t *cha, md_acme_authz_t *authz, 
+                                     md_acme_t *acme, md_store_t *store, 
+                                     md_pkeys_spec_t *key_specs,
+                                     apr_array_header_t *acme_tls_1_domains, const md_t *md,
+                                     apr_table_t *env, md_result_t *result, apr_pool_t *p)
+{
+    const char *token;
+    const char * const *argv;
+    const char *cmdline, *dns01_cmd;
+    apr_status_t rv;
+    int exit_code, notify_server;
+    authz_req_ctx ctx;
+    md_data_t data;
+    const char *event;
+
+    (void)store;
+    (void)key_specs;
+    (void)acme_tls_1_domains;
+
+    dns01_cmd = md->dns01_cmd;
+    if (!dns01_cmd)
+      dns01_cmd = apr_table_get(env, MD_KEY_CMD_DNS01);
+    if (!dns01_cmd) {
+        rv = APR_ENOTIMPL;
+        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p, "%s: dns-01 command not set", 
+                      authz->domain);
+        goto out;
+    }
+    
+    if (APR_SUCCESS != (rv = setup_key_authz(cha, authz, acme, p, &notify_server))) {
+        goto out;
+    }
+    
+    md_data_init_str(&data, cha->key_authz);
+    rv = md_crypt_sha256_digest64(&token, p, &data);
+    if (APR_SUCCESS != rv) {
+        md_log_perror(MD_LOG_MARK, MD_LOG_ERR, rv, p, "%s: create dns-01 token for %s",
+                      md->name, authz->domain);
+        goto out;
+    }
+
+    cmdline = apr_psprintf(p, "%s setup %s %s", dns01_cmd, authz->domain, token); 
+    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, p, 
+                  "%s: dns-01 setup command: %s", authz->domain, cmdline);
+
+    apr_tokenize_to_argv(cmdline, (char***)&argv, p);
+    if (APR_SUCCESS != (rv = md_util_exec(p, argv[0], argv, NULL, &exit_code))) {
+        md_log_perror(MD_LOG_MARK, MD_LOG_WARNING, rv, p, 
+                      "%s: dns-01 setup command failed to execute for %s", md->name, authz->domain);
+        goto out;
+    }
+    if (exit_code) {
+        rv = APR_EGENERAL;
+        md_log_perror(MD_LOG_MARK, MD_LOG_INFO, rv, p, 
+                      "%s: dns-01 setup command returns %d for %s", md->name, exit_code, authz->domain);
+        goto out;
+    }
+    
+    /* Raise event that challenge data has been set up before we tell the
+       ACME server. Clusters might want to distribute it. */
+    event = apr_psprintf(p, "challenge-setup:%s:%s", MD_AUTHZ_TYPE_DNS01, authz->domain);
+    rv = md_result_raise(result, event, p);
+    if (APR_SUCCESS != rv) {
+        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p,
+                      "%s: event '%s' failed. aborting challenge setup",
+                      authz->domain, event);
+        goto out;
+    }
+    /* challenge is setup, tell ACME server so it may (re)try verification */
+    md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p, "%s: dns-01 setup succeeded for %s",
+       md->name, authz->domain);
+    authz_req_ctx_init(&ctx, acme, NULL, authz, p);
+    ctx.challenge = cha;
+    rv = md_acme_POST(acme, cha->uri, on_init_authz_resp, authz_http_set, NULL, NULL, &ctx);
+    
+out:    
+    return rv;
+}
+
+static apr_status_t cha_dns_01_teardown(md_store_t *store, const char *domain, const md_t *md,
+                                        apr_table_t *env, apr_pool_t *p)
+{
+    const char * const *argv;
+    const char *cmdline, *dns01_cmd;
+    apr_status_t rv;
+    int exit_code;
+    
+    (void)store;
+
+    dns01_cmd = md->dns01_cmd;
+    if (!dns01_cmd)
+      dns01_cmd = apr_table_get(env, MD_KEY_CMD_DNS01);
+    if (!dns01_cmd) {
+        rv = APR_ENOTIMPL;
+        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, 0, p, "%s: dns-01 command not set for %s",
+            md->name, domain);
+        goto out;
+    }
+    
+    cmdline = apr_psprintf(p, "%s teardown %s", dns01_cmd, domain); 
+    apr_tokenize_to_argv(cmdline, (char***)&argv, p);
+    if (APR_SUCCESS != (rv = md_util_exec(p, argv[0], argv, NULL, &exit_code)) || exit_code) {
+        md_log_perror(MD_LOG_MARK, MD_LOG_WARNING, rv, p, 
+                      "%s: dns-01 teardown command failed (exit code=%d) for %s",
+                      md->name, exit_code, domain);
+    }
+out:    
+    return rv;
+}
+
+static apr_status_t cha_teardown_dir(md_store_t *store, const char *domain, const md_t *md,
+                                     apr_table_t *env, apr_pool_t *p)
+{
+    (void)md;
+    (void)env;
+    return md_store_purge(store, p, MD_SG_CHALLENGES, domain);
+}
+
+typedef apr_status_t cha_setup(md_acme_authz_cha_t *cha, md_acme_authz_t *authz, 
+                               md_acme_t *acme, md_store_t *store, 
+                               md_pkeys_spec_t *key_specs,
+                               apr_array_header_t *acme_tls_1_domains, const md_t *md,
+                               apr_table_t *env, md_result_t *result, apr_pool_t *p);
+                               
+typedef apr_status_t cha_teardown(md_store_t *store, const char *domain, const md_t *md,
+                                  apr_table_t *env, apr_pool_t *p);
+                                 
+typedef struct {
+    const char *name;
+    cha_setup *setup;
+    cha_teardown *teardown;
+} cha_type;
+
+static const cha_type CHA_TYPES[] = {
+    { MD_AUTHZ_TYPE_HTTP01,     cha_http_01_setup,      cha_teardown_dir },
+    { MD_AUTHZ_TYPE_TLSALPN01,  cha_tls_alpn_01_setup,  cha_teardown_dir },
+    { MD_AUTHZ_TYPE_DNS01,      cha_dns_01_setup,       cha_dns_01_teardown },
+};
+static const apr_size_t CHA_TYPES_LEN = (sizeof(CHA_TYPES)/sizeof(CHA_TYPES[0]));
+
+typedef struct {
+    apr_pool_t *p;
+    const char *type;
+    md_acme_authz_cha_t *accepted;
+    apr_array_header_t *offered;
+} cha_find_ctx;
+
+static apr_status_t collect_offered(void *baton, size_t index, md_json_t *json)
+{
+    cha_find_ctx *ctx = baton;
+    const char *ctype;
+    
+    (void)index;
+    if ((ctype = md_json_gets(json, MD_KEY_TYPE, NULL))) {
+        APR_ARRAY_PUSH(ctx->offered, const char*) = apr_pstrdup(ctx->p, ctype);
+    }
+    return 1;
+}
+
+static apr_status_t find_type(void *baton, size_t index, md_json_t *json)
+{
+    cha_find_ctx *ctx = baton;
+    
+    const char *ctype = md_json_gets(json, MD_KEY_TYPE, NULL);
+    if (ctype && !apr_strnatcasecmp(ctx->type, ctype)) {
+        ctx->accepted = cha_from_json(ctx->p, index, json);
+        return 0;
+    }
+    return 1;
+}
+
+apr_status_t md_acme_authz_respond(md_acme_authz_t *authz, md_acme_t *acme, md_store_t *store, 
+                                   apr_array_header_t *challenges, md_pkeys_spec_t *key_specs,
+                                   apr_array_header_t *acme_tls_1_domains, const md_t *md,
+                                   apr_table_t *env, apr_pool_t *p, const char **psetup_token,
+                                   md_result_t *result)
+{
+    apr_status_t rv;
+    int i, j;
+    cha_find_ctx fctx;
+    const char *challenge_setup;
+    
+    assert(acme);
+    assert(authz);
+    assert(authz->resource);
+
+    fctx.p = p;
+    fctx.accepted = NULL;
+    
+    /* Look in the order challenge types are defined:
+     * - if they are offered by the CA, try to set it up
+     * - if setup was successful, we are done and the CA will evaluate us
+     * - if setup failed, continue to look for another supported challenge type
+     * - if there is no overlap in types, tell the user that she has to configure
+     *   either more types (dns, tls-alpn-01), make ports available or refrain
+     *   from using wildcard domains when dns is not available. etc.
+     * - if there was an overlap, but no setup was successful, report that. We
+     *   will retry this, maybe the failure is temporary (e.g. command to setup DNS
+     */
+     md_result_printf(result, 0, "%s: selecting suitable authorization challenge "
+                      "type, this domain supports %s",
+                      authz->domain, apr_array_pstrcat(p, challenges, ' '));
+    rv = APR_ENOTIMPL;
+    challenge_setup = NULL;
+    for (i = 0; i < challenges->nelts; ++i) {
+        fctx.type = APR_ARRAY_IDX(challenges, i, const char *);
+        fctx.accepted = NULL;
+        md_json_itera(find_type, &fctx, authz->resource, MD_KEY_CHALLENGES, NULL);
+        md_log_perror(MD_LOG_MARK, MD_LOG_TRACE1, 0, p,
+                      "%s: challenge type '%s' for %s: %s",
+                      authz->domain, fctx.type, md->name,
+                      fctx.accepted? "maybe acceptable" : "not applicable");
+
+        if (fctx.accepted) {
+            for (j = 0; j < (int)CHA_TYPES_LEN; ++j) {
+                if (!apr_strnatcasecmp(CHA_TYPES[j].name, fctx.accepted->type)) {
+                    md_result_activity_printf(result, "Setting up challenge '%s' for domain %s", 
+                                              fctx.accepted->type, authz->domain);
+                    rv = CHA_TYPES[j].setup(fctx.accepted, authz, acme, store, key_specs,
+                                            acme_tls_1_domains, md, env, result, p);
+                    if (APR_SUCCESS == rv) {
+                        md_log_perror(MD_LOG_MARK, MD_LOG_DEBUG, rv, p, 
+                                      "%s: set up challenge '%s' for %s", 
+                                      authz->domain, fctx.accepted->type, md->name);
+                        challenge_setup = CHA_TYPES[j].name;
+                        goto out;
+                    }
+                    md_result_printf(result, rv, "error setting up challenge '%s' for %s, "
+                                     "for domain %s, looking for other option",
+                                     fctx.accepted->type, authz->domain, md->name);
+                    md_result_log(result, MD_LOG_INFO);
+                }
+            }
+        }
+    }
+    
+out:
+    *psetup_token = (APR_SUCCESS == rv)? apr_psprintf(p, "%s:%s", challenge_setup, authz->domain) : NULL;
+    if (!fctx.accepted || APR_ENOTIMPL == rv) {
+        rv = APR_EINVAL;
+        fctx.offered = apr_array_make(p, 5, sizeof(const char*));
+        md_json_itera(collect_offered, &fctx, authz->resource, MD_KEY_CHALLENGES, NULL);
+        md_result_printf(result, rv, "None of offered challenge types for domain %s are supported. "
+                      "The server offered '%s' and available are: '%s'.",
+                      authz->domain, 
+                      apr_array_pstrcat(p, fctx.offered, ' '),
+                      apr_array_pstrcat(p, challenges, ' '));
+        result->problem = "challenge-mismatch";
+        md_result_log(result, MD_LOG_ERR);
+    }
+    else if (APR_SUCCESS != rv) {
+        fctx.offered = apr_array_make(p, 5, sizeof(const char*));
+        md_json_itera(collect_offered, &fctx, authz->resource, MD_KEY_CHALLENGES, NULL);
+        md_result_printf(result, rv, "None of the offered challenge types %s offered "
+                         "for domain %s could be setup successfully. Please check the "
+                         "log for errors.", authz->domain, 
+                         apr_array_pstrcat(p, fctx.offered, ' '));
+        result->problem = "challenge-setup-failure";
+        md_result_log(result, MD_LOG_ERR);
+    }
+    return rv;
+}
+
+apr_status_t md_acme_authz_teardown(struct md_store_t *store, const char *token,
+                                    const md_t *md, apr_table_t *env, apr_pool_t *p)
+{
+    char *challenge, *domain;
+    int i;
+    
+    if (strchr(token, ':')) {
+        challenge = apr_pstrdup(p, token);
+        domain = strchr(challenge, ':');
+        *domain = '\0'; domain++;
+        for (i = 0; i < (int)CHA_TYPES_LEN; ++i) {
+            if (!apr_strnatcasecmp(CHA_TYPES[i].name, challenge)) {
+                if (CHA_TYPES[i].teardown) {
+                    return CHA_TYPES[i].teardown(store, domain, md, env, p);
+                }
+                break;
+            }
+        }
+    }
+    return APR_SUCCESS;
+}
+