/* 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 "apr_strings.h"
#include "apr_file_info.h"
#include "apr_user.h"

#include "ap_config.h"
#include "ap_provider.h"
#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "http_log.h"
#include "http_protocol.h"
#include "http_request.h"

#include "mod_auth.h"     /* for AUTHZ_GROUP_NOTE */

APR_DECLARE_OPTIONAL_FN(char*, authz_owner_get_file_group, (request_rec *r));

static const command_rec authz_owner_cmds[] =
{
    {NULL}
};

module AP_MODULE_DECLARE_DATA authz_owner_module;

static authz_status fileowner_check_authorization(request_rec *r,
                                             const char *require_args)
{
    char *reason = NULL;
    apr_status_t status = 0;

#if !APR_HAS_USER
    reason = "'Require file-owner' is not supported on this platform.";
    ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                  "Authorization of user %s to access %s failed, reason: %s",
                  r->user, r->uri, reason ? reason : "unknown");
    return AUTHZ_DENIED;
#else  /* APR_HAS_USER */
    char *owner = NULL;
    apr_finfo_t finfo;

    if (!r->filename) {
        reason = "no filename available";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return AUTHZ_DENIED;
    }

    status = apr_stat(&finfo, r->filename, APR_FINFO_USER, r->pool);
    if (status != APR_SUCCESS) {
        reason = apr_pstrcat(r->pool, "could not stat file ",
                                r->filename, NULL);
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return AUTHZ_DENIED;
    }

    if (!(finfo.valid & APR_FINFO_USER)) {
        reason = "no file owner information available";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return AUTHZ_DENIED;
    }

    status = apr_uid_name_get(&owner, finfo.user, r->pool);
    if (status != APR_SUCCESS || !owner) {
        reason = "could not get name of file owner";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return AUTHZ_DENIED;
    }

    if (strcmp(owner, r->user)) {
        reason = apr_psprintf(r->pool, "file owner %s does not match.",
                                owner);
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return AUTHZ_DENIED;
    }

    /* this user is authorized */
    return AUTHZ_GRANTED;
#endif /* APR_HAS_USER */
}

static char *authz_owner_get_file_group(request_rec *r)
{
    char *reason = NULL;

    /* file-group only figures out the file's group and lets
    * other modules do the actual authorization (against a group file/db).
    * Thus, these modules have to hook themselves after
    * mod_authz_owner and of course recognize 'file-group', too.
    */
#if !APR_HAS_USER
    return NULL;
#else  /* APR_HAS_USER */
    char *group = NULL;
    apr_finfo_t finfo;
    apr_status_t status = 0;

    if (!r->filename) {
        reason = "no filename available";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return NULL;
    }

    status = apr_stat(&finfo, r->filename, APR_FINFO_GROUP, r->pool);
    if (status != APR_SUCCESS) {
        reason = apr_pstrcat(r->pool, "could not stat file ",
                                r->filename, NULL);
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return NULL;
    }

    if (!(finfo.valid & APR_FINFO_GROUP)) {
        reason = "no file group information available";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return NULL;
    }

    status = apr_gid_name_get(&group, finfo.group, r->pool);
    if (status != APR_SUCCESS || !group) {
        reason = "could not get name of file group";
        ap_log_rerror(APLOG_MARK, APLOG_ERR, status, r,
                      "Authorization of user %s to access %s failed, reason: %s",
                      r->user, r->uri, reason ? reason : "unknown");
        return NULL;
    }

    return group;
#endif /* APR_HAS_USER */
}

static const authz_provider authz_fileowner_provider =
{
    &fileowner_check_authorization,
};

static void register_hooks(apr_pool_t *p)
{
    APR_REGISTER_OPTIONAL_FN(authz_owner_get_file_group);

    ap_register_provider(p, AUTHZ_PROVIDER_GROUP, "file-owner", "0",
                         &authz_fileowner_provider);
}

module AP_MODULE_DECLARE_DATA authz_owner_module =
{
    STANDARD20_MODULE_STUFF,
    NULL,                          /* dir config creater */
    NULL,                          /* dir merger --- default is to override */
    NULL,                          /* server config */
    NULL,                          /* merge server config */
    authz_owner_cmds,              /* command apr_table_t */
    register_hooks                 /* register hooks */
};