1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "httpd.h"
18#include "http_core.h"
19#include "http_config.h"
20#include "http_protocol.h"
21#include "http_request.h"
22#include "http_log.h"
23#include "apr_strings.h"
24
25/**
26 * This module makes it easy to restrict what HTTP methods can be ran against
27 * a server.
28 *
29 * It provides one comand:
30 *    AllowMethods
31 * This command takes a list of HTTP methods to allow.
32 *
33 *  The most common configuration should be like this:
34 *   <Directory />
35 *    AllowMethods GET HEAD OPTIONS
36 *   </Directory>
37 *   <Directory /special/cgi-bin>
38 *      AllowMethods GET HEAD OPTIONS POST
39 *   </Directory>
40 *  Non-matching methods will be returned a status 405 (method not allowed)
41 *
42 *  To allow all methods, and effectively turn off mod_allowmethods, use:
43 *    AllowMethods reset
44 */
45
46typedef struct am_conf_t {
47  int allowed_set;
48  apr_int64_t allowed;
49} am_conf_t;
50
51module AP_MODULE_DECLARE_DATA allowmethods_module;
52
53static int am_check_access(request_rec *r)
54{
55  int method = r->method_number;
56  am_conf_t *conf;
57
58  conf = (am_conf_t *) ap_get_module_config(r->per_dir_config,
59                                            &allowmethods_module);
60  if (!conf || conf->allowed == 0) {
61    return DECLINED;
62  }
63
64  r->allowed = conf->allowed;
65
66  if (conf->allowed & (AP_METHOD_BIT << method)) {
67    return DECLINED;
68  }
69
70  ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01623)
71                  "client method denied by server configuration: '%s' to %s%s",
72                  r->method,
73                  r->filename ? "" : "uri ",
74                  r->filename ? r->filename : r->uri);
75
76  return HTTP_METHOD_NOT_ALLOWED;
77}
78
79static void *am_create_conf(apr_pool_t * p, char *dummy)
80{
81  am_conf_t *conf = apr_pcalloc(p, sizeof(am_conf_t));
82
83  conf->allowed = 0;
84  conf->allowed_set = 0;
85  return conf;
86}
87
88static void* am_merge_conf(apr_pool_t* pool, void* a, void* b) {
89  am_conf_t* base = (am_conf_t*) a;
90  am_conf_t* add = (am_conf_t*) b;
91  am_conf_t* conf = apr_palloc(pool, sizeof(am_conf_t));
92
93  if (add->allowed_set) {
94      conf->allowed = add->allowed;
95      conf->allowed_set = add->allowed_set;
96  } else {
97      conf->allowed = base->allowed;
98      conf->allowed_set = base->allowed_set;
99  }
100
101  return conf;
102}
103
104static const char *am_allowmethods(cmd_parms *cmd, void *d, int argc, char *const argv[])
105{
106  int i;
107  am_conf_t* conf = (am_conf_t*) d;
108  if (argc == 0) {
109      return "AllowMethods: No method or 'reset' keyword given";
110  }
111  if (argc == 1) {
112    if (strcasecmp("reset", argv[0]) == 0) {
113      conf->allowed = 0;
114      conf->allowed_set = 1;
115      return NULL;
116    }
117  }
118
119  for (i = 0; i < argc; i++) {
120    int m = 0;
121    m = ap_method_number_of(argv[i]);
122    if (m == M_INVALID) {
123      return apr_pstrcat(cmd->pool, "AllowMethods: Invalid Method '", argv[i], "'", NULL);
124    }
125
126    conf->allowed |= (AP_METHOD_BIT << m);
127  }
128  conf->allowed_set = 1;
129  return NULL;
130}
131
132static void am_register_hooks(apr_pool_t * p)
133{
134  ap_hook_access_checker(am_check_access, NULL, NULL, APR_HOOK_REALLY_FIRST);
135}
136
137static const command_rec am_cmds[] = {
138  AP_INIT_TAKE_ARGV("AllowMethods", am_allowmethods, NULL,
139              ACCESS_CONF,
140              "only allow specific methods"),
141  {NULL}
142};
143
144AP_DECLARE_MODULE(allowmethods) = {
145  STANDARD20_MODULE_STUFF,
146  am_create_conf,
147  am_merge_conf,
148  NULL,
149  NULL,
150  am_cmds,
151  am_register_hooks,
152};
153
154