/* 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.
 */

/*
 * Adapted to allow anonymous logins, just like with Anon-FTP, when
 * one gives the magic user name 'anonymous' and ones email address
 * as the password.
 *
 * Just add the following tokes to your <directory> setup:
 *
 * Anonymous                    magic-userid [magic-userid]...
 *
 * Anonymous_MustGiveEmail      [ on | off ] default = on
 * Anonymous_LogEmail           [ on | off ] default = on
 * Anonymous_VerifyEmail        [ on | off ] default = off
 * Anonymous_NoUserId           [ on | off ] default = off
 *
 * The magic user id is something like 'anonymous', it is NOT case sensitive.
 *
 * The MustGiveEmail flag can be used to force users to enter something
 * in the password field (like an email address). Default is on.
 *
 * Furthermore the 'NoUserID' flag can be set to allow completely empty
 * usernames in as well; this can be is convenient as a single return
 * in broken GUIs like W95 is often given by the user. The Default is off.
 *
 * Dirk.vanGulik@jrc.it; http://ewse.ceo.org; http://me-www.jrc.it/~dirkx
 *
 */

#include "apr_strings.h"

#define APR_WANT_STRFUNC
#include "apr_want.h"

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

#include "mod_auth.h"

typedef struct anon_auth_user {
    const char *user;
    struct anon_auth_user *next;
} anon_auth_user;

typedef struct {
    anon_auth_user *users;
    int nouserid;
    int logemail;
    int verifyemail;
    int mustemail;
    int anyuserid;
} authn_anon_config_rec;

static void *create_authn_anon_dir_config(apr_pool_t *p, char *d)
{
    authn_anon_config_rec *conf = apr_palloc(p, sizeof(*conf));

    /* just to illustrate the defaults really. */
    conf->users = NULL;

    conf->nouserid = 0;
    conf->anyuserid = 0;
    conf->logemail = 1;
    conf->verifyemail = 0;
    conf->mustemail = 1;
    return conf;
}

static const char *anon_set_string_slots(cmd_parms *cmd,
                                         void *my_config, const char *arg)
{
    authn_anon_config_rec *conf = my_config;
    anon_auth_user *first;

    if (!*arg) {
        return "Anonymous string cannot be empty, use Anonymous_NoUserId";
    }

    /* squeeze in a record */
    if (!conf->anyuserid) {
        if (!strcmp(arg, "*")) {
            conf->anyuserid = 1;
        }
        else {
            first = conf->users;
            conf->users = apr_palloc(cmd->pool, sizeof(*conf->users));
            conf->users->user = arg;
            conf->users->next = first;
        }
    }

    return NULL;
}

static const command_rec authn_anon_cmds[] =
{
    AP_INIT_ITERATE("Anonymous", anon_set_string_slots, NULL, OR_AUTHCFG,
     "a space-separated list of user IDs"),
    AP_INIT_FLAG("Anonymous_MustGiveEmail", ap_set_flag_slot,
     (void *)APR_OFFSETOF(authn_anon_config_rec, mustemail),
     OR_AUTHCFG, "Limited to 'on' or 'off'"),
    AP_INIT_FLAG("Anonymous_NoUserId", ap_set_flag_slot,
     (void *)APR_OFFSETOF(authn_anon_config_rec, nouserid),
     OR_AUTHCFG, "Limited to 'on' or 'off'"),
    AP_INIT_FLAG("Anonymous_VerifyEmail", ap_set_flag_slot,
     (void *)APR_OFFSETOF(authn_anon_config_rec, verifyemail),
     OR_AUTHCFG, "Limited to 'on' or 'off'"),
    AP_INIT_FLAG("Anonymous_LogEmail", ap_set_flag_slot,
     (void *)APR_OFFSETOF(authn_anon_config_rec, logemail),
     OR_AUTHCFG, "Limited to 'on' or 'off'"),
    {NULL}
};

module AP_MODULE_DECLARE_DATA authn_anon_module;

static authn_status check_anonymous(request_rec *r, const char *user,
                                    const char *sent_pw)
{
    authn_anon_config_rec *conf = ap_get_module_config(r->per_dir_config,
                                                      &authn_anon_module);
    authn_status res = AUTH_USER_NOT_FOUND;

    /* Ignore if we are not configured */
    if (!conf->users && !conf->anyuserid) {
        return AUTH_USER_NOT_FOUND;
    }

    /* Do we allow an empty userID and/or is it the magic one
     */
    if (!*user) {
        if (conf->nouserid) {
            res = AUTH_USER_FOUND;
        }
    }
    else if (conf->anyuserid) {
        res = AUTH_USER_FOUND;
    }
    else {
        anon_auth_user *p = conf->users;

        while (p) {
            if (!strcasecmp(user, p->user)) {
                res = AUTH_USER_FOUND;
                break;
            }
            p = p->next;
        }
    }

    /* Now if the supplied user-ID was ok, grant access if:
     * (a) no passwd was sent and no password and no verification
     *     were configured.
     * (b) password was sent and no verification was configured
     * (c) verification was configured and the password (sent or not)
     *     looks like an email address
     */
    if (   (res == AUTH_USER_FOUND)
        && (!conf->mustemail || *sent_pw)
        && (   !conf->verifyemail
            || (ap_strchr_c(sent_pw, '@') && ap_strchr_c(sent_pw, '.'))))
    {
        if (conf->logemail && ap_is_initial_req(r)) {
            ap_log_rerror(APLOG_MARK, APLOG_INFO, APR_SUCCESS, r, APLOGNO(01672)
                          "Anonymous: Passwd <%s> Accepted",
                          sent_pw ? sent_pw : "\'none\'");
        }

        return AUTH_GRANTED;
    }

    return (res == AUTH_USER_NOT_FOUND ? res : AUTH_DENIED);
}

static const authn_provider authn_anon_provider =
{
    &check_anonymous,
    NULL
};

static void register_hooks(apr_pool_t *p)
{
    ap_register_auth_provider(p, AUTHN_PROVIDER_GROUP, "anon",
                              AUTHN_PROVIDER_VERSION,
                              &authn_anon_provider, AP_AUTH_INTERNAL_PER_CONF);
}

AP_DECLARE_MODULE(authn_anon) =
{
    STANDARD20_MODULE_STUFF,
    create_authn_anon_dir_config, /* dir config creater */
    NULL,                         /* dir merger ensure strictness */
    NULL,                         /* server config */
    NULL,                         /* merge server config */
    authn_anon_cmds,              /* command apr_table_t */
    register_hooks                /* register hooks */
};