/* 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 <apr_optional.h>
#include <apr_time.h>
#include <apr_date.h>
#include <apr_strings.h>

#include <httpd.h>
#include <http_core.h>
#include <http_log.h>
#include <http_ssl.h>

#include "mod_watchdog.h"

#include "md.h"
#include "md_crypt.h"
#include "md_http.h"
#include "md_json.h"
#include "md_ocsp.h"
#include "md_store.h"
#include "md_log.h"
#include "md_reg.h"
#include "md_time.h"
#include "md_util.h"

#include "mod_md.h"
#include "mod_md_config.h"
#include "mod_md_private.h"
#include "mod_md_ocsp.h"

static int staple_here(md_srv_conf_t *sc) 
{
    if (!sc || !sc->mc->ocsp) return 0;
    if (sc->assigned 
        && sc->assigned->nelts == 1
        && APR_ARRAY_IDX(sc->assigned, 0, const md_t*)->stapling) return 1;
    return (md_config_geti(sc, MD_CONFIG_STAPLING) 
            && md_config_geti(sc, MD_CONFIG_STAPLE_OTHERS));
}

int md_ocsp_prime_status(server_rec *s, apr_pool_t *p,
                         const char *id, apr_size_t id_len, const char *pem)
{
    md_srv_conf_t *sc;
    const md_t *md;
    apr_array_header_t *chain;
    apr_status_t rv = APR_ENOENT;

    sc = md_config_get(s);
    if (!staple_here(sc)) goto cleanup;

    md = ((sc->assigned && sc->assigned->nelts == 1)?
          APR_ARRAY_IDX(sc->assigned, 0, const md_t*) : NULL);
    chain = apr_array_make(p, 5, sizeof(md_cert_t*));
    rv = md_cert_read_chain(chain, p, pem, strlen(pem));
    if (APR_SUCCESS != rv) {
        ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(10268) "init stapling for: %s, "
                     "unable to parse PEM data", md? md->name : s->server_hostname);
        goto cleanup;
    }
    else if (chain->nelts < 2) {
        ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(10269) "init stapling for: %s, "
                     "need at least 2 certificates in PEM data", md? md->name : s->server_hostname);
        rv = APR_EINVAL;
        goto cleanup;
    }

    rv = md_ocsp_prime(sc->mc->ocsp, id, id_len,
                       APR_ARRAY_IDX(chain, 0, md_cert_t*),
                       APR_ARRAY_IDX(chain, 1, md_cert_t*), md);
    ap_log_error(APLOG_MARK, APLOG_TRACE1, rv, s, "init stapling for: %s",
                 md? md->name : s->server_hostname);

cleanup:
    return (APR_SUCCESS == rv)? OK : DECLINED;
}

typedef struct {
    unsigned char *der;
    apr_size_t der_len;
} ocsp_copy_ctx_t;

int md_ocsp_provide_status(server_rec *s, conn_rec *c,
                           const char *id, apr_size_t id_len,
                           ap_ssl_ocsp_copy_resp *cb, void *userdata)
{
    md_srv_conf_t *sc;
    const md_t *md;
    apr_status_t rv;

    sc = md_config_get(s);
    if (!staple_here(sc)) goto declined;

    md = ((sc->assigned && sc->assigned->nelts == 1)?
          APR_ARRAY_IDX(sc->assigned, 0, const md_t*) : NULL);
    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, c, "get stapling for: %s",
                  md? md->name : s->server_hostname);

    rv = md_ocsp_get_status(cb, userdata, sc->mc->ocsp, id, id_len, c->pool, md);
    if (APR_STATUS_IS_ENOENT(rv)) goto declined;
    return OK;

declined:
    return DECLINED;
}


/**************************************************************************************************/
/* watchdog based impl. */

#define MD_OCSP_WATCHDOG_NAME   "_md_ocsp_"

static APR_OPTIONAL_FN_TYPE(ap_watchdog_get_instance) *wd_get_instance;
static APR_OPTIONAL_FN_TYPE(ap_watchdog_register_callback) *wd_register_callback;
static APR_OPTIONAL_FN_TYPE(ap_watchdog_set_callback_interval) *wd_set_interval;

typedef struct md_ocsp_ctx_t md_ocsp_ctx_t;

struct md_ocsp_ctx_t {
    apr_pool_t *p;
    server_rec *s;
    md_mod_conf_t *mc;
    ap_watchdog_t *watchdog;
};

static apr_time_t next_run_default(void)
{
    /* we'd like to run at least hourly */
    return apr_time_now() + apr_time_from_sec(MD_SECS_PER_HOUR);
}

static apr_status_t run_watchdog(int state, void *baton, apr_pool_t *ptemp)
{
    md_ocsp_ctx_t *octx = baton;
    apr_time_t next_run, wait_time;
    
    /* mod_watchdog invoked us as a single thread inside the whole server (on this machine).
     * This might be a repeated run inside the same child (mod_watchdog keeps affinity as
     * long as the child lives) or another/new child.
     */
    switch (state) {
        case AP_WATCHDOG_STATE_STARTING:
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, octx->s, APLOGNO(10197)
                         "md ocsp watchdog start, ocsp stapling %d certificates", 
                         (int)md_ocsp_count(octx->mc->ocsp));
            break;
            
        case AP_WATCHDOG_STATE_RUNNING:
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, octx->s, APLOGNO(10198)
                         "md ocsp watchdog run, ocsp stapling %d certificates", 
                         (int)md_ocsp_count(octx->mc->ocsp));
                         
            /* Process all drive jobs. They will update their next_run property
             * and we schedule ourself at the earliest of all. A job may specify 0
             * as next_run to indicate that it wants to participate in the normal
             * regular runs. */
            next_run = next_run_default();
            
            md_ocsp_renew(octx->mc->ocsp, octx->p, ptemp, &next_run);
            
            wait_time = next_run - apr_time_now();
            if (APLOGdebug(octx->s)) {
                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, octx->s, APLOGNO(10199)
                             "md ocsp watchdog next run in %s", 
                             md_duration_print(ptemp, wait_time));
            }
            wd_set_interval(octx->watchdog, wait_time, octx, run_watchdog);
            break;
            
        case AP_WATCHDOG_STATE_STOPPING:
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, octx->s, APLOGNO(10200)
                         "md ocsp watchdog stopping");
            break;
    }
    
    return APR_SUCCESS;
}

static apr_status_t ocsp_remove_old_responses(md_mod_conf_t *mc, apr_pool_t *p)
{
    md_timeperiod_t keep_norm, keep;
    
    keep_norm.end = apr_time_now();
    keep_norm.start = keep_norm.end - MD_TIME_OCSP_KEEP_NORM;
    keep = md_timeperiod_slice_before_end(&keep_norm, mc->ocsp_keep_window);
    /* remove any ocsp response older than keep.start */
    return md_ocsp_remove_responses_older_than(mc->ocsp, p, keep.start);
}

apr_status_t md_ocsp_start_watching(md_mod_conf_t *mc, server_rec *s, apr_pool_t *p)
{
    apr_allocator_t *allocator;
    md_ocsp_ctx_t *octx;
    apr_pool_t *octxp;
    apr_status_t rv;
    
    wd_get_instance = APR_RETRIEVE_OPTIONAL_FN(ap_watchdog_get_instance);
    wd_register_callback = APR_RETRIEVE_OPTIONAL_FN(ap_watchdog_register_callback);
    wd_set_interval = APR_RETRIEVE_OPTIONAL_FN(ap_watchdog_set_callback_interval);
    
    if (!wd_get_instance || !wd_register_callback || !wd_set_interval) {
        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, APLOGNO(10201) 
                     "mod_watchdog is required for OCSP stapling");
        return APR_EGENERAL;
    }
    
    /* We want our own pool with own allocator to keep data across watchdog invocations.
     * Since we'll run in a single watchdog thread, using our own allocator will prevent 
     * any confusion in the parent pool. */
    apr_allocator_create(&allocator);
    apr_allocator_max_free_set(allocator, 1);
    rv = apr_pool_create_ex(&octxp, p, NULL, allocator);
    if (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, APLOGNO(10205) "md_ocsp_watchdog: create pool");
        return rv;
    }
    apr_allocator_owner_set(allocator, octxp);
    apr_pool_tag(octxp, "md_ocsp_watchdog");

    octx = apr_pcalloc(octxp, sizeof(*octx));
    octx->p = octxp;
    octx->s = s;
    octx->mc = mc;
    
    /* Time for some house keeping, before the server goes live (again):
     * - we store OCSP responses for each certificate individually by its SHA-1 id
     * - this means, as long as certificate do not change, the number of response
     *   files remains stable.
     * - But when a certificate changes (is replaced), the response is obsolete
     * - we do not get notified when a certificate is no longer used. An admin
     *   might just reconfigure or change the content of a file (backup/restore etc.)
     * - also, certificates might be added by some openssl config commands or other
     *   modules that we do not immediately see right at startup. We cannot assume
     *   that any OCSP response we cannot relate to a certificate RIGHT NOW, is no
     *   longer needed.
     * - since the response files are relatively small, we have no problem with
     *   keeping them around for a while. We just do not want an ever growing store. 
     * - The simplest and effective way seems to be to just remove files older
     *   a certain amount of time. Take a 7 day default and let the admin configure
     *   it for very special setups. 
     */ 
    ocsp_remove_old_responses(mc, octx->p);
    
    rv = wd_get_instance(&octx->watchdog, MD_OCSP_WATCHDOG_NAME, 0, 1, octx->p);
    if (APR_SUCCESS != rv) {
        ap_log_error(APLOG_MARK, APLOG_CRIT, rv, s, APLOGNO(10202) 
                     "create md ocsp watchdog(%s)", MD_OCSP_WATCHDOG_NAME);
        return rv;
    }
    rv = wd_register_callback(octx->watchdog, 0, octx, run_watchdog);
    ap_log_error(APLOG_MARK, rv? APLOG_CRIT : APLOG_DEBUG, rv, s, APLOGNO(10203) 
                 "register md ocsp watchdog(%s)", MD_OCSP_WATCHDOG_NAME);
    return rv;
}