git.r.bdr.sh - rbdr/ngx_http_office_hours_filter_module/blob - ngx_http_office_hours_filter_module.c

   1 /*
   2  * Copyright 2018 Rubén Beltrán del Río
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
   5  * License. You may obtain a copy of the License at
   6  *
   7  * http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
  10  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
  11  * specific language governing permissions and limitations under the License.
  12  */
  13
  14
  15 #include <ngx_config.h>
  16 #include <ngx_core.h>
  17 #include <ngx_http.h>
  18
  19 /*
  20  * Declarations
  21  */
  22
  23 /* Constants */
  24
  25 const ngx_uint_t WEEK_LENGTH = 7;
  26 const char * CLOSED_TOKEN = "closed";
  27 const ngx_str_t TIME_REGEX = ngx_string("([0-9]{1,2})(?:\\:([0-9]{2}))?\\-([0-9]{1,2})(?:\\:([0-9]{2}))?");
  28 const ngx_str_t OUTPUT_HTML = ngx_string("<!doctype html><html><head><title>This website is currently closed!</title></head><body><h1>This website is currently closed!</h1><p>This website has closed for the day, please check our office hours below</p></body></html>");
  29
  30 /* Main Configuration Structure */
  31
  32 typedef struct {
  33     ngx_array_t *office_hours;
  34 } ngx_http_office_hours_conf_t;
  35
  36 /* Lifecycle Functions For Module Context */
  37
  38 static void *ngx_http_office_hours_create_conf(ngx_conf_t * cf);
  39 static char *ngx_http_office_hours_merge_conf(ngx_conf_t * cf,
  40         void *parent, void *child);
  41 static ngx_int_t ngx_http_office_hours_init(ngx_conf_t * cf);
  42
  43 /* Configuration Handler */
  44
  45 static char *ngx_http_office_hours(ngx_conf_t * cf, ngx_command_t * cmd,
  46                                    void *conf);
  47
  48 /* Filter Storage */
  49
  50 static ngx_http_output_header_filter_pt ngx_http_next_header_filter;
  51 static ngx_http_output_body_filter_pt ngx_http_next_body_filter;
  52
  53 /* Utility Functions */
  54 static ngx_uint_t ** parse_office_hours(ngx_array_t * office_hours);
  55 static ngx_uint_t * parse_office_hours_string(ngx_str_t office_hours);
  56 static ngx_flag_t within_office_hours(ngx_uint_t ** office_hours);
  57 static ngx_uint_t get_day_of_week(time_t time);
  58 static ngx_uint_t get_seconds_of_day(time_t time);
  59 static ngx_uint_t parse_number(ngx_str_t string, ngx_uint_t start, ngx_uint_t end);
  60
  61 /* Compiled Regex */
  62 ngx_regex_compile_t rc;
  63
  64 /*
  65  * Module Definitions
  66  */
  67
  68 /* Module Directives */
  69
  70 static ngx_command_t ngx_http_office_hours_commands[] = {
  71     {
  72         ngx_string("office_hours"),
  73         NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF | NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1 | NGX_CONF_TAKE2 | NGX_CONF_TAKE3 | NGX_CONF_TAKE4 | NGX_CONF_TAKE5 | NGX_CONF_TAKE6 | NGX_CONF_TAKE7,
  74         ngx_http_office_hours,
  75         NGX_HTTP_LOC_CONF_OFFSET,
  76         offsetof(ngx_http_office_hours_conf_t, office_hours),
  77         NULL
  78     },
  79
  80     ngx_null_command
  81 };
  82
  83
  84 /* Module Context */
  85
  86 static ngx_http_module_t ngx_http_office_hours_filter_module_ctx = {
  87     NULL,                       /* Preconfiguration */
  88     ngx_http_office_hours_init, /* Postconfiguration */
  89
  90     NULL,                       /* Create main configuration */
  91     NULL,                       /* Initialize main configuration */
  92
  93     NULL,                       /* Create server configuration */
  94     NULL,                       /* Merge server configuration */
  95
  96     ngx_http_office_hours_create_conf,  /* Create location configuration */
  97     ngx_http_office_hours_merge_conf    /* Merge location configuration */
  98 };
  99
 100
 101 /* Module Definition */
 102
 103 ngx_module_t ngx_http_office_hours_filter_module = {
 104     NGX_MODULE_V1,              //Module Version
 105     &ngx_http_office_hours_filter_module_ctx,   //Module context
 106     ngx_http_office_hours_commands,     //Module commands
 107     NGX_HTTP_MODULE,            //Module Type
 108     NULL,                       //Initialize Master
 109     NULL,                       //Initialize Module
 110     NULL,                       //Initialize Process
 111     NULL,                       //Initialize Thread
 112     NULL,                       //Exit Thread
 113     NULL,                       //Exit Process
 114     NULL,                       //Exit Master
 115     NGX_MODULE_V1_PADDING
 116 };
 117
 118
 119 /*
 120  * Main Header Filter
 121  * If the current time is within office hours, it goes to the next
 122  * handler. Otherwise it sets the headers to 403
 123  */
 124
 125 static ngx_int_t
 126 ngx_http_office_hours_header_filter(ngx_http_request_t * r)
 127 {
 128
 129     ngx_uint_t ** parsed_office_hours;
 130     ngx_http_office_hours_conf_t *conf;
 131
 132     conf =
 133         ngx_http_get_module_loc_conf(r,
 134                                      ngx_http_office_hours_filter_module);
 135
 136
 137     if (conf->office_hours == NULL) {
 138         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 139                       "Office hours disabled");
 140         return ngx_http_next_header_filter(r);
 141     }
 142
 143     parsed_office_hours = parse_office_hours(conf->office_hours);
 144
 145     if (within_office_hours(parsed_office_hours)) {
 146         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 147                       "Within office hours");
 148         return ngx_http_next_header_filter(r);
 149     }
 150
 151     ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 152                   "Outside office hours");
 153
 154     r->headers_out.status = NGX_HTTP_FORBIDDEN;
 155     r->headers_out.content_length_n = OUTPUT_HTML.len;
 156
 157     return ngx_http_next_header_filter(r);
 158 }
 159
 160 /*
 161  * Main Body Filter
 162  * If the current time is within office hours, it goes to the next
 163  * handler. Otherwise it replaces the body with the office hours.
 164  */
 165
 166 static ngx_int_t
 167 ngx_http_office_hours_body_filter(ngx_http_request_t * r, ngx_chain_t *in)
 168 {
 169
 170     ngx_buf_t    *b;
 171     ngx_uint_t ** parsed_office_hours;
 172     ngx_chain_t   out;
 173     ngx_http_office_hours_conf_t *conf;
 174
 175     conf =
 176         ngx_http_get_module_loc_conf(r,
 177                                      ngx_http_office_hours_filter_module);
 178
 179
 180     if (conf->office_hours == NULL) {
 181         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 182                       "Office hours disabled");
 183         return ngx_http_next_body_filter(r, in);
 184     }
 185
 186     parsed_office_hours = parse_office_hours(conf->office_hours);
 187
 188     if (within_office_hours(parsed_office_hours)) {
 189         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 190                       "Within office hours");
 191         return ngx_http_next_body_filter(r, in);
 192     }
 193
 194     ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 195                   "Outside office hours");
 196
 197     b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
 198     if (b == NULL) {
 199         ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "Failed to allocate response buffer.");
 200         return NGX_HTTP_INTERNAL_SERVER_ERROR;
 201     }
 202
 203     out.buf = b;
 204     out.next = NULL;
 205
 206     b->start = OUTPUT_HTML.data;
 207     b->pos = b->start;
 208     b->end = OUTPUT_HTML.data + OUTPUT_HTML.len;
 209     b->last = b->end;
 210
 211     b->memory = 1;
 212     b->last_buf = 1;
 213
 214     return ngx_http_next_body_filter(r, &out);
 215 }
 216
 217 /*
 218  * Callback for `office_hours ` directive
 219  * Reads the configuration loaded from the config file(cf)
 220  * And writes it to the right place in the module configuration(conf)
 221  */
 222
 223 static char *ngx_http_office_hours(ngx_conf_t * cf, ngx_command_t * cmd,
 224                                    void *conf)
 225 {
 226
 227     char *conf_structure = conf;
 228
 229     ngx_str_t *hours, *value;
 230     ngx_array_t **office_hours;
 231     ngx_uint_t i;
 232
 233     /* Gets the array from the config structure using the defined
 234      * offset, and if the pointer is unset it creates a new one.
 235      * (The first element is the directive itself, so we should be
 236      * offset by 1)
 237      */
 238     office_hours = (ngx_array_t **) (conf_structure + cmd->offset);
 239
 240     if (*office_hours == NGX_CONF_UNSET_PTR) {
 241         *office_hours = ngx_array_create(cf->pool, cf->args->nelts - 1,
 242                                          sizeof(ngx_str_t));
 243
 244         if (*office_hours == NULL) {
 245             return NGX_CONF_ERROR;
 246         }
 247     }
 248     value = cf->args->elts;
 249
 250     for (i = 1; i < cf->args->nelts; ++i) {
 251         hours = ngx_array_push(*office_hours);
 252         if (hours == NULL) {
 253             return NGX_CONF_ERROR;
 254         }
 255         *hours = value[i];
 256     }
 257
 258     return NGX_CONF_OK;
 259 }
 260
 261
 262 /*
 263  * Config Creator
 264  * Initializes the configuration structure
 265  */
 266
 267 static void *ngx_http_office_hours_create_conf(ngx_conf_t * cf)
 268 {
 269
 270     ngx_http_office_hours_conf_t *conf;
 271
 272     conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_office_hours_conf_t));
 273
 274     if (conf == NULL) {
 275         return NULL;
 276     }
 277     conf->office_hours = NGX_CONF_UNSET_PTR;
 278
 279     return conf;
 280 }
 281
 282 /*
 283  * Merge Config Values
 284  * Sets the defaults for the configuration and merges
 285  * with other configurations
 286  */
 287
 288 static char *ngx_http_office_hours_merge_conf(ngx_conf_t * cf,
 289         void *parent, void *child)
 290 {
 291
 292     ngx_http_office_hours_conf_t *prev = parent;
 293     ngx_http_office_hours_conf_t *conf = child;
 294
 295     ngx_conf_merge_ptr_value(conf->office_hours, prev->office_hours, NULL);
 296
 297     return NGX_CONF_OK;
 298 }
 299
 300 /*
 301  * Parse the office hour strings in the configuration file
 302  * to fill out the hours array (in seconds)
 303  */
 304
 305 static ngx_uint_t ** parse_office_hours(ngx_array_t * office_hours)
 306 {
 307
 308     ngx_str_t *hours;
 309     ngx_uint_t ** parsed_office_hours;
 310     ngx_uint_t i, j;
 311
 312     parsed_office_hours = malloc(7 * sizeof(ngx_uint_t *));
 313
 314     hours = office_hours->elts;
 315
 316     /*
 317      * On the configuration file, the leftmost element
 318      * always applies to all remaining days, all others
 319      * are read from right to left. So first we will apply
 320      * the initial override, and then iterate based on the
 321      * number of overrides
 322      */
 323
 324     for (i = 0; i < WEEK_LENGTH + 1 - office_hours->nelts; ++i) {
 325         parsed_office_hours[i] = parse_office_hours_string(hours[0]);
 326     }
 327
 328     for (i = 1; i < office_hours->nelts; ++i) {
 329         j = WEEK_LENGTH - office_hours->nelts + i;
 330         parsed_office_hours[j] = parse_office_hours_string(hours[i]);
 331     }
 332
 333     return parsed_office_hours;
 334 }
 335
 336 /*
 337  * Given a time string or the closed token, return a tuple
 338  * of numbers representing opening and closing hours
 339  */
 340
 341 static ngx_uint_t * parse_office_hours_string(ngx_str_t office_hours)
 342 {
 343
 344     int captures[(1 + 4) * 3];
 345     ngx_int_t n;
 346     ngx_uint_t * parsed_hours;
 347
 348     parsed_hours = malloc(2 * sizeof(ngx_uint_t));
 349
 350     if(ngx_strcmp(office_hours.data, CLOSED_TOKEN) == 0) {
 351         parsed_hours[0] = 0;
 352         parsed_hours[1] = 0;
 353         return parsed_hours;
 354     }
 355
 356     n = ngx_regex_exec(rc.regex, &office_hours, captures, (1 + 4) * 3);
 357
 358     if (n >= 0) {
 359         /* Opening Hours */
 360
 361         parsed_hours[0] = 60 * 60 * parse_number(office_hours, captures[2], captures[3]);
 362         parsed_hours[0] = parsed_hours[0] + 60 * parse_number(office_hours, captures[4], captures[5]);
 363
 364         parsed_hours[1] = 60 * 60 * parse_number(office_hours, captures[6], captures[7]);
 365         parsed_hours[1] = parsed_hours[1] + 60 * parse_number(office_hours, captures[8], captures[9]);
 366
 367         return parsed_hours;
 368     }
 369
 370     /* Non-matching strings count as open */
 371
 372     parsed_hours[0] = 0;
 373     parsed_hours[1] = 86400;
 374     return parsed_hours;
 375 }
 376
 377 /*
 378  * Given an office hours array, it returns whether or not
 379  * it is currently within office hours.
 380  */
 381
 382 static ngx_flag_t within_office_hours(ngx_uint_t ** office_hours)
 383 {
 384
 385     time_t now;
 386     ngx_uint_t day_of_week, seconds_of_day;
 387     ngx_uint_t * current_hours;
 388
 389     ngx_time_update();
 390     now = ngx_time();
 391     day_of_week = get_day_of_week(now);
 392     seconds_of_day = get_seconds_of_day(now);
 393     current_hours = office_hours[day_of_week];
 394
 395     return seconds_of_day >= current_hours[0] && seconds_of_day <= current_hours[1];
 396 }
 397
 398 /*
 399  * Calculate the day of the week given a timestamp
 400  */
 401 static ngx_uint_t get_day_of_week(time_t time)
 402 {
 403
 404     /* Epoch was thursday, so add 3 so we start on monday */
 405     return (time / 86400 + 3) % 7;
 406 }
 407
 408 /*
 409  * Calculate the number of seconds elapsed today
 410  */
 411 static ngx_uint_t get_seconds_of_day(time_t time)
 412 {
 413
 414     return time - (time / 86400) * 86400;
 415 }
 416
 417 /*
 418  * Parses a string, returns 0 if match was not found
 419  */
 420 static ngx_uint_t parse_number(ngx_str_t string, ngx_uint_t start, ngx_uint_t end)
 421 {
 422
 423     if (end - start == 0) {
 424         return 0;
 425     }
 426
 427     return ngx_atoi(&string.data[start], end - start);
 428 }
 429
 430 /*
 431  * Postconfig Initialization Handler
 432  * Sets the request filter at the top of the chain
 433  */
 434
 435 static ngx_int_t ngx_http_office_hours_init(ngx_conf_t * cf)
 436 {
 437
 438     ngx_http_next_header_filter = ngx_http_top_header_filter;
 439     ngx_http_top_header_filter = ngx_http_office_hours_header_filter;
 440
 441     ngx_http_next_body_filter = ngx_http_top_body_filter;
 442     ngx_http_top_body_filter = ngx_http_office_hours_body_filter;
 443
 444     rc.pattern = TIME_REGEX;
 445     rc.pool = cf->pool;
 446     if (ngx_regex_compile(&rc) != NGX_OK) {
 447         return NGX_ERROR;
 448     }
 449
 450     return NGX_OK;
 451 }