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 #include <ngx_config.h>
  15 #include <ngx_core.h>
  16 #include <ngx_http.h>
  17
  18 /*
  19  * Declarations
  20  */
  21
  22 /* Constants */
  23
  24 const ngx_uint_t WEEK_LENGTH = 7;
  25 const char * CLOSED_TOKEN = "closed";
  26 const ngx_str_t TIME_REGEX = ngx_string("([0-9]{1,2})(?:\\:([0-9]{2}))?\\-([0-9]{1,2})(?:\\:([0-9]{2}))?");
  27 const ngx_str_t HEAD_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><ul>");
  28 const ngx_str_t MIDDLE_HTML = ngx_string("</ul><p><em>Current Server Time is: ");
  29 const ngx_str_t FOOT_HTML = ngx_string("</em></p></body></html>");
  30 const char * DAY_NAMES[7] = {
  31     "Monday",
  32     "Tuesday",
  33     "Wednesday",
  34     "Thursday",
  35     "Friday",
  36     "Saturday",
  37     "Sunday"
  38 };
  39
  40 /* Main Configuration Structure */
  41
  42 typedef struct {
  43     ngx_array_t *office_hours;
  44 } ngx_http_office_hours_conf_t;
  45
  46 /* Lifecycle Functions For Module Context */
  47
  48 static void *ngx_http_office_hours_create_conf(ngx_conf_t * cf);
  49 static char *ngx_http_office_hours_merge_conf(ngx_conf_t * cf,
  50     void *parent, void *child);
  51 static ngx_int_t ngx_http_office_hours_init(ngx_conf_t * cf);
  52
  53 /* Configuration Handler */
  54
  55 static char *ngx_http_office_hours(ngx_conf_t * cf, ngx_command_t * cmd,
  56                                    void *conf);
  57
  58 /* Filter Storage */
  59
  60 static ngx_http_output_header_filter_pt ngx_http_next_header_filter;
  61 static ngx_http_output_body_filter_pt ngx_http_next_body_filter;
  62
  63 /* Utility Functions */
  64 static ngx_uint_t ** parse_office_hours(ngx_array_t * office_hours);
  65 static ngx_uint_t * parse_office_hours_string(ngx_str_t office_hours);
  66 static ngx_flag_t within_office_hours(ngx_uint_t ** office_hours);
  67 static ngx_uint_t get_day_of_week(time_t time);
  68 static ngx_uint_t get_seconds_of_day(time_t time);
  69 static ngx_uint_t parse_number(ngx_str_t string, ngx_uint_t start, ngx_uint_t end);
  70 static ngx_str_t create_output_html(ngx_http_office_hours_conf_t * conf);
  71 static char * format_hours(ngx_uint_t * seconds, char * day);
  72 static char * format_seconds(ngx_uint_t seconds);
  73 static char * left_pad(unsigned int number);
  74
  75 /* Globals */
  76 ngx_regex_compile_t rc;
  77 ngx_str_t OUTPUT_HTML;
  78
  79 /*
  80  * Module Definitions
  81  */
  82
  83 /* Module Directives */
  84
  85 static ngx_command_t ngx_http_office_hours_commands[] = {
  86     {
  87         ngx_string("office_hours"),
  88         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,
  89         ngx_http_office_hours,
  90         NGX_HTTP_LOC_CONF_OFFSET,
  91         offsetof(ngx_http_office_hours_conf_t, office_hours),
  92         NULL
  93     },
  94
  95     ngx_null_command
  96 };
  97
  98 /* Module Context */
  99
 100 static ngx_http_module_t ngx_http_office_hours_filter_module_ctx = {
 101     NULL,                       /* Preconfiguration */
 102     ngx_http_office_hours_init, /* Postconfiguration */
 103
 104     NULL,                       /* Create main configuration */
 105     NULL,                       /* Initialize main configuration */
 106
 107     NULL,                       /* Create server configuration */
 108     NULL,                       /* Merge server configuration */
 109
 110     ngx_http_office_hours_create_conf,  /* Create location configuration */
 111     ngx_http_office_hours_merge_conf    /* Merge location configuration */
 112 };
 113
 114 /* Module Definition */
 115
 116 ngx_module_t ngx_http_office_hours_filter_module = {
 117     NGX_MODULE_V1,              //Module Version
 118     &ngx_http_office_hours_filter_module_ctx,   //Module context
 119     ngx_http_office_hours_commands,     //Module commands
 120     NGX_HTTP_MODULE,            //Module Type
 121     NULL,                       //Initialize Master
 122     NULL,                       //Initialize Module
 123     NULL,                       //Initialize Process
 124     NULL,                       //Initialize Thread
 125     NULL,                       //Exit Thread
 126     NULL,                       //Exit Process
 127     NULL,                       //Exit Master
 128     NGX_MODULE_V1_PADDING
 129 };
 130
 131 /*
 132  * Main Header Filter
 133  * If the current time is within office hours, it goes to the next
 134  * handler. Otherwise it sets the headers to 403
 135  */
 136
 137 static ngx_int_t
 138 ngx_http_office_hours_header_filter(ngx_http_request_t * r)
 139 {
 140
 141     ngx_uint_t ** parsed_office_hours;
 142     ngx_http_office_hours_conf_t *conf;
 143
 144     conf =
 145         ngx_http_get_module_loc_conf(r,
 146                                      ngx_http_office_hours_filter_module);
 147
 148     if (conf->office_hours == NULL) {
 149         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 150                       "Office hours disabled");
 151         return ngx_http_next_header_filter(r);
 152     }
 153
 154     parsed_office_hours = parse_office_hours(conf->office_hours);
 155
 156     if (within_office_hours(parsed_office_hours)) {
 157         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 158                       "Within office hours");
 159         return ngx_http_next_header_filter(r);
 160     }
 161
 162     ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 163                   "Outside office hours");
 164
 165     if (OUTPUT_HTML.data == NULL) {
 166         OUTPUT_HTML = create_output_html(conf);
 167     }
 168
 169     r->headers_out.status = NGX_HTTP_FORBIDDEN;
 170     r->headers_out.content_length_n = OUTPUT_HTML.len;
 171
 172     return ngx_http_next_header_filter(r);
 173 }
 174
 175 /*
 176  * Main Body Filter
 177  * If the current time is within office hours, it goes to the next
 178  * handler. Otherwise it replaces the body with the office hours.
 179  */
 180
 181 static ngx_int_t
 182 ngx_http_office_hours_body_filter(ngx_http_request_t * r, ngx_chain_t *in)
 183 {
 184
 185     ngx_buf_t    *b;
 186     ngx_uint_t ** parsed_office_hours;
 187     ngx_chain_t   out;
 188     ngx_http_office_hours_conf_t *conf;
 189
 190     conf =
 191         ngx_http_get_module_loc_conf(r,
 192                                      ngx_http_office_hours_filter_module);
 193
 194     if (conf->office_hours == NULL) {
 195         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 196                       "Office hours disabled");
 197         return ngx_http_next_body_filter(r, in);
 198     }
 199
 200     parsed_office_hours = parse_office_hours(conf->office_hours);
 201
 202     if (within_office_hours(parsed_office_hours)) {
 203         ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 204                       "Within office hours");
 205         return ngx_http_next_body_filter(r, in);
 206     }
 207
 208     ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
 209                   "Outside office hours");
 210
 211     if (OUTPUT_HTML.data == NULL) {
 212         OUTPUT_HTML = create_output_html(conf);
 213     }
 214
 215     b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
 216     if (b == NULL) {
 217         ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "Failed to allocate response buffer.");
 218         return NGX_HTTP_INTERNAL_SERVER_ERROR;
 219     }
 220
 221     out.buf = b;
 222     out.next = NULL;
 223
 224     b->start = OUTPUT_HTML.data;
 225     b->pos = b->start;
 226     b->end = OUTPUT_HTML.data + OUTPUT_HTML.len;
 227     b->last = b->end;
 228
 229     b->memory = 1;
 230     b->last_buf = 1;
 231
 232     return ngx_http_next_body_filter(r, &out);
 233 }
 234
 235 /*
 236  * Callback for `office_hours ` directive
 237  * Reads the configuration loaded from the config file(cf)
 238  * And writes it to the right place in the module configuration(conf)
 239  */
 240
 241 static char *ngx_http_office_hours(ngx_conf_t * cf, ngx_command_t * cmd,
 242                                    void *conf)
 243 {
 244
 245     char *conf_structure = conf;
 246
 247     ngx_str_t *hours, *value;
 248     ngx_array_t **office_hours;
 249     ngx_uint_t i;
 250
 251     /* Gets the array from the config structure using the defined
 252      * offset, and if the pointer is unset it creates a new one.
 253      * (The first element is the directive itself, so we should be
 254      * offset by 1)
 255      */
 256     office_hours = (ngx_array_t **) (conf_structure + cmd->offset);
 257
 258     if (*office_hours == NGX_CONF_UNSET_PTR) {
 259         *office_hours = ngx_array_create(cf->pool, cf->args->nelts - 1,
 260                                          sizeof(ngx_str_t));
 261
 262         if (*office_hours == NULL) {
 263             return NGX_CONF_ERROR;
 264         }
 265     }
 266     value = cf->args->elts;
 267
 268     for (i = 1; i < cf->args->nelts; ++i) {
 269         hours = ngx_array_push(*office_hours);
 270         if (hours == NULL) {
 271             return NGX_CONF_ERROR;
 272         }
 273         *hours = value[i];
 274     }
 275
 276     return NGX_CONF_OK;
 277 }
 278
 279 /*
 280  * Config Creator
 281  * Initializes the configuration structure
 282  */
 283
 284 static void *ngx_http_office_hours_create_conf(ngx_conf_t * cf)
 285 {
 286
 287     ngx_http_office_hours_conf_t *conf;
 288
 289     conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_office_hours_conf_t));
 290
 291     if (conf == NULL) {
 292         return NULL;
 293     }
 294     conf->office_hours = NGX_CONF_UNSET_PTR;
 295
 296     return conf;
 297 }
 298
 299 /*
 300  * Merge Config Values
 301  * Sets the defaults for the configuration and merges
 302  * with other configurations
 303  */
 304
 305 static char *ngx_http_office_hours_merge_conf(ngx_conf_t * cf,
 306     void *parent, void *child)
 307 {
 308
 309     ngx_http_office_hours_conf_t *prev = parent;
 310     ngx_http_office_hours_conf_t *conf = child;
 311
 312     ngx_conf_merge_ptr_value(conf->office_hours, prev->office_hours, NULL);
 313
 314     return NGX_CONF_OK;
 315 }
 316
 317 /*
 318  * Parse the office hour strings in the configuration file
 319  * to fill out the hours array (in seconds)
 320  */
 321
 322 static ngx_uint_t ** parse_office_hours(ngx_array_t * office_hours)
 323 {
 324
 325     ngx_str_t *hours;
 326     ngx_uint_t ** parsed_office_hours;
 327     ngx_uint_t i, j;
 328
 329     parsed_office_hours = malloc(7 * sizeof(ngx_uint_t *));
 330
 331     hours = office_hours->elts;
 332
 333     /*
 334      * On the configuration file, the leftmost element
 335      * always applies to all remaining days, all others
 336      * are read from right to left. So first we will apply
 337      * the initial override, and then iterate based on the
 338      * number of overrides
 339      */
 340
 341     for (i = 0; i < WEEK_LENGTH + 1 - office_hours->nelts; ++i) {
 342         parsed_office_hours[i] = parse_office_hours_string(hours[0]);
 343     }
 344
 345     for (i = 1; i < office_hours->nelts; ++i) {
 346         j = WEEK_LENGTH - office_hours->nelts + i;
 347         parsed_office_hours[j] = parse_office_hours_string(hours[i]);
 348     }
 349
 350     return parsed_office_hours;
 351 }
 352
 353 /*
 354  * Given a time string or the closed token, return a tuple
 355  * of numbers representing opening and closing hours
 356  */
 357
 358 static ngx_uint_t * parse_office_hours_string(ngx_str_t office_hours)
 359 {
 360
 361     int captures[(1 + 4) * 3];
 362     ngx_int_t n;
 363     ngx_uint_t * parsed_hours;
 364
 365     parsed_hours = malloc(2 * sizeof(ngx_uint_t));
 366
 367     if(ngx_strcmp(office_hours.data, CLOSED_TOKEN) == 0) {
 368         parsed_hours[0] = 0;
 369         parsed_hours[1] = 0;
 370         return parsed_hours;
 371     }
 372
 373     n = ngx_regex_exec(rc.regex, &office_hours, captures, (1 + 4) * 3);
 374
 375     if (n >= 0) {
 376         /* Opening Hours */
 377
 378         parsed_hours[0] = 60 * 60 * parse_number(office_hours, captures[2], captures[3]);
 379         parsed_hours[0] = parsed_hours[0] + 60 * parse_number(office_hours, captures[4], captures[5]);
 380
 381         parsed_hours[1] = 60 * 60 * parse_number(office_hours, captures[6], captures[7]);
 382         parsed_hours[1] = parsed_hours[1] + 60 * parse_number(office_hours, captures[8], captures[9]);
 383
 384         return parsed_hours;
 385     }
 386
 387     /* Non-matching strings count as open */
 388
 389     parsed_hours[0] = 0;
 390     parsed_hours[1] = 86400;
 391     return parsed_hours;
 392 }
 393
 394 /*
 395  * Given an office hours array, it returns whether or not
 396  * it is currently within office hours.
 397  */
 398
 399 static ngx_flag_t within_office_hours(ngx_uint_t ** office_hours)
 400 {
 401
 402     time_t now;
 403     ngx_uint_t day_of_week, seconds_of_day;
 404     ngx_uint_t * current_hours;
 405
 406     ngx_time_update();
 407     now = ngx_time();
 408     day_of_week = get_day_of_week(now);
 409     seconds_of_day = get_seconds_of_day(now);
 410     current_hours = office_hours[day_of_week];
 411
 412     return seconds_of_day >= current_hours[0] && seconds_of_day <= current_hours[1];
 413 }
 414
 415 /*
 416  * Calculate the day of the week given a timestamp
 417  */
 418
 419 static ngx_uint_t get_day_of_week(time_t time)
 420 {
 421
 422     /* Epoch was thursday, so add 3 so we start on monday */
 423     return (time / 86400 + 3) % 7;
 424 }
 425
 426 /*
 427  * Calculate the number of seconds elapsed today
 428  */
 429
 430 static ngx_uint_t get_seconds_of_day(time_t time)
 431 {
 432
 433     return time - (time / 86400) * 86400;
 434 }
 435
 436 /*
 437  * Parses a string, returns 0 if match was not found
 438  */
 439
 440 static ngx_uint_t parse_number(ngx_str_t string, ngx_uint_t start, ngx_uint_t end)
 441 {
 442
 443     if (end - start == 0) {
 444         return 0;
 445     }
 446
 447     return ngx_atoi(&string.data[start], end - start);
 448 }
 449
 450 /*
 451  * Given the current office hours configuration it creates the custom
 452  * HTML
 453  */
 454
 455 static ngx_str_t create_output_html(ngx_http_office_hours_conf_t * conf)
 456 {
 457
 458     char * output_buffer;
 459     time_t now;
 460     ngx_str_t output_html;
 461     ngx_uint_t i, seconds_of_day;
 462     ngx_uint_t ** parsed_office_hours;
 463
 464     output_buffer = malloc(1024 * sizeof(char));
 465     parsed_office_hours = parse_office_hours(conf->office_hours);
 466     now = ngx_time();
 467     seconds_of_day = get_seconds_of_day(now);
 468
 469     sprintf(output_buffer, "%s", (char *) HEAD_HTML.data);
 470
 471     for (i = 0; i < 7; ++i) {
 472         sprintf(output_buffer + strlen(output_buffer), "%s", format_hours(parsed_office_hours[i], (char *) DAY_NAMES[i]));
 473     }
 474
 475     sprintf(output_buffer + strlen(output_buffer), "%s", (char *) MIDDLE_HTML.data);
 476     sprintf(output_buffer + strlen(output_buffer), "%s", format_seconds(seconds_of_day));
 477     sprintf(output_buffer + strlen(output_buffer), "%s", (char *) FOOT_HTML.data);
 478
 479     output_html.data = (unsigned char *) output_buffer;
 480     output_html.len = strlen(output_buffer);
 481
 482     return output_html;
 483 }
 484
 485 /*
 486  * Given a tuple of seconds and a day name, outputs an HTML
 487  * string containing the formatted data as a list item
 488  */
 489
 490 static char * format_hours(ngx_uint_t * hours, char * day)
 491 {
 492
 493     char * output_html;
 494
 495     output_html = malloc(64 * sizeof(char));
 496     if (hours[0] == hours[1]) {
 497         sprintf(output_html, "<li><strong>%s</strong>: CLOSED</li>",
 498                 day
 499                );
 500         return output_html;
 501     }
 502
 503     sprintf(output_html, "<li><strong>%s</strong>: %s - %s</li>",
 504             day,
 505             (char *) format_seconds(hours[0]),
 506             (char *) format_seconds(hours[1])
 507            );
 508
 509     return output_html;
 510 }
 511
 512 /*
 513  * Given seconds of the day, it returns a string showing
 514  * HH:MM in 24 hour format
 515  */
 516
 517 static char * format_seconds(ngx_uint_t seconds)
 518 {
 519
 520     char * output_html;
 521     unsigned int hours, minutes;
 522
 523     output_html = malloc(6 * sizeof(char));
 524
 525     hours = seconds / 60 / 60;
 526     minutes = (seconds / 60) % 60;
 527
 528     sprintf(output_html, "%s:%s",
 529             left_pad(hours),
 530             left_pad(minutes)
 531            );
 532
 533     return output_html;
 534 }
 535
 536 /*
 537  * Returns a number as a string adding 0 if < 10
 538  */
 539
 540 static char * left_pad(unsigned int number)
 541 {
 542
 543     char * output_string;
 544     char * padding;
 545
 546     padding = "";
 547     output_string = malloc(4 * sizeof(char));
 548
 549     if (number < 10) {
 550         padding = "0";
 551     }
 552
 553     snprintf(output_string, 4, "%s%u", padding, number);
 554
 555     return output_string;
 556 }
 557
 558 /*
 559  * Postconfig Initialization Handler
 560  * Sets the request filter at the top of the chain
 561  */
 562
 563 static ngx_int_t ngx_http_office_hours_init(ngx_conf_t * cf)
 564 {
 565
 566     ngx_http_next_header_filter = ngx_http_top_header_filter;
 567     ngx_http_top_header_filter = ngx_http_office_hours_header_filter;
 568
 569     ngx_http_next_body_filter = ngx_http_top_body_filter;
 570     ngx_http_top_body_filter = ngx_http_office_hours_body_filter;
 571
 572     rc.pattern = TIME_REGEX;
 573     rc.pool = cf->pool;
 574     if (ngx_regex_compile(&rc) != NGX_OK) {
 575         return NGX_ERROR;
 576     }
 577
 578     return NGX_OK;
 579 }