webcit/context_loop.c

   1 /*
   2  * context_loop.c
   3  *
   4  * This is the other half of the webserver.  It handles the task of hooking
   5  * up HTTP requests with the sessions they belong to, using HTTP cookies to
   6  * keep track of things.  If the HTTP request doesn't belong to any currently
   7  * active session, a new session is started.
   8  *
   9  * $Id$
  10  */
  11
  12 #include <ctype.h>
  13 #include <stdlib.h>
  14 #ifdef HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17 #include <stdio.h>
  18 #ifdef HAVE_FCNTL_H
  19 #include <fcntl.h>
  20 #endif
  21 #include <signal.h>
  22 #include <sys/types.h>
  23 #include <sys/wait.h>
  24 #include <sys/socket.h>
  25 #ifdef HAVE_SYS_TIME_H
  26 #include <sys/time.h>
  27 #endif
  28 #ifdef HAVE_LIMITS_H
  29 #include <limits.h>
  30 #endif
  31 #include <netinet/in.h>
  32 #include <netdb.h>
  33 #include <string.h>
  34 #include <errno.h>
  35 #include <stdarg.h>
  36 #include <pthread.h>
  37 #include <signal.h>
  38 #include "webcit.h"
  39 #include "webserver.h"
  40
  41 /* Only one thread may manipulate SessionList at a time... */
  42 pthread_mutex_t SessionListMutex;
  43
  44 struct wcsession *SessionList = NULL;
  45
  46 pthread_key_t MyConKey;                         /* TSD key for MySession() */
  47
  48
  49 void free_attachments(struct wcsession *sess) {
  50         struct wc_attachment *att;
  51
  52         while (sess->first_attachment != NULL) {
  53                 att = sess->first_attachment;
  54                 sess->first_attachment = sess->first_attachment->next;
  55                 free(att->data);
  56                 free(att);
  57         }
  58 }
  59
  60
  61 void do_housekeeping(void)
  62 {
  63         struct wcsession *sptr, *ss, *session_to_kill;
  64         int num_sessions = 0;
  65         static int num_threads = MIN_WORKER_THREADS;
  66
  67         do {
  68                 session_to_kill = NULL;
  69                 pthread_mutex_lock(&SessionListMutex);
  70                 num_sessions = 0;
  71                 for (sptr = SessionList; sptr != NULL; sptr = sptr->next) {
  72                         ++num_sessions;
  73
  74                         /* Kill idle sessions */
  75                         if ((time(NULL) - (sptr->lastreq)) >
  76                            (time_t) WEBCIT_TIMEOUT) {
  77                                 sptr->killthis = 1;
  78                         }
  79
  80                         /* Remove sessions flagged for kill */
  81                         if (sptr->killthis) {
  82
  83                                 lprintf(3, "Destroying session %d\n",
  84                                         sptr->wc_session);
  85
  86                                 /* remove session from linked list */
  87                                 if (sptr == SessionList) {
  88                                         SessionList = SessionList->next;
  89                                 }
  90                                 else for (ss=SessionList;ss!=NULL;ss=ss->next) {
  91                                         if (ss->next == sptr) {
  92                                                 ss->next = ss->next->next;
  93                                         }
  94                                 }
  95
  96                                 session_to_kill = sptr;
  97                                 goto BREAKOUT;
  98                         }
  99                 }
 100 BREAKOUT:       pthread_mutex_unlock(&SessionListMutex);
 101
 102                 if (session_to_kill != NULL) {
 103                         pthread_mutex_lock(&session_to_kill->SessionMutex);
 104                         close(session_to_kill->serv_sock);
 105                         close(session_to_kill->chat_sock);
 106                         if (session_to_kill->preferences != NULL) {
 107                                 free(session_to_kill->preferences);
 108                         }
 109                         free_attachments(session_to_kill);
 110                         pthread_mutex_unlock(&session_to_kill->SessionMutex);
 111                         free(session_to_kill);
 112                 }
 113
 114         } while (session_to_kill != NULL);
 115
 116         /*
 117          * See if we need more worker threads
 118          */
 119         while ( (num_sessions > num_threads)
 120               && (num_threads <= MAX_WORKER_THREADS) ) {
 121                 spawn_another_worker_thread();
 122                 ++num_threads;
 123                 lprintf(3, "There are %d sessions and %d threads active.\n",
 124                         num_sessions, num_threads);
 125         }
 126 }
 127
 128
 129 /*
 130  * Wake up occasionally and clean house
 131  */
 132 void housekeeping_loop(void)
 133 {
 134         while (1) {
 135                 sleeeeeeeeeep(HOUSEKEEPING);
 136                 do_housekeeping();
 137         }
 138 }
 139
 140
 141 /*
 142  * Generate a unique WebCit session ID (which is not the same thing as the
 143  * Citadel session ID).
 144  *
 145  * FIXME ... ensure that session number is truly unique
 146  *
 147  */
 148 int GenerateSessionID(void)
 149 {
 150         static int seq = (-1);
 151
 152         if (seq < 0) {
 153                 seq = (int) time(NULL);
 154         }
 155
 156         return ++seq;
 157 }
 158
 159
 160 /*
 161  * Collapse multiple cookies on one line
 162  */
 163 int req_gets(int sock, char *buf, char *hold)
 164 {
 165         int a;
 166
 167         if (strlen(hold) == 0) {
 168                 strcpy(buf, "");
 169                 a = client_gets(sock, buf);
 170                 if (a<1) return(-1);
 171         } else {
 172                 safestrncpy(buf, hold, SIZ);
 173         }
 174         strcpy(hold, "");
 175
 176         if (!strncasecmp(buf, "Cookie: ", 8)) {
 177                 for (a = 0; a < strlen(buf); ++a)
 178                         if (buf[a] == ';') {
 179                                 sprintf(hold, "Cookie: %s", &buf[a + 1]);
 180                                 buf[a] = 0;
 181                                 while (isspace(hold[8]))
 182                                         strcpy(&hold[8], &hold[9]);
 183                                 return(0);
 184                         }
 185         }
 186
 187         return(0);
 188 }
 189
 190 /*
 191  * lingering_close() a`la Apache. see
 192  * http://www.apache.org/docs/misc/fin_wait_2.html for rationale
 193  */
 194
 195 int lingering_close(int fd)
 196 {
 197         char buf[SIZ];
 198         int i;
 199         fd_set set;
 200         struct timeval tv, start;
 201
 202         gettimeofday(&start, NULL);
 203         shutdown(fd, 1);
 204         do {
 205                 do {
 206                         gettimeofday(&tv, NULL);
 207                         tv.tv_sec = SLEEPING - (tv.tv_sec - start.tv_sec);
 208                         tv.tv_usec = start.tv_usec - tv.tv_usec;
 209                         if (tv.tv_usec < 0) {
 210                                 tv.tv_sec--;
 211                                 tv.tv_usec += 1000000;
 212                         }
 213                         FD_ZERO(&set);
 214                         FD_SET(fd, &set);
 215                         i = select(fd + 1, &set, NULL, NULL, &tv);
 216                 } while (i == -1 && errno == EINTR);
 217
 218                 if (i <= 0)
 219                         break;
 220
 221                 i = read(fd, buf, sizeof buf);
 222         } while (i != 0 && (i != -1 || errno == EINTR));
 223
 224         return close(fd);
 225 }
 226
 227
 228
 229 /*
 230  * Check for bogus requests coming from (for example) brain-dead
 231  * Windoze boxes that are infected with the latest worm-of-the-week.
 232  * If we detect one of these, bail out without bothering our Citadel
 233  * server.
 234  */
 235 int is_bogus(char *http_cmd) {
 236
 237         if (!strncasecmp(http_cmd, "GET /scripts/root.exe", 21)) return(1);
 238         if (!strncasecmp(http_cmd, "GET /c/winnt", 12)) return(2);
 239         if (!strncasecmp(http_cmd, "GET /MSADC/", 11)) return(3);
 240
 241         return(0);      /* probably ok */
 242 }
 243
 244
 245
 246 /*
 247  * This loop gets called once for every HTTP connection made to WebCit.  At
 248  * this entry point we have an HTTP socket with a browser allegedly on the
 249  * other end, but we have not yet bound to a WebCit session.
 250  *
 251  * The job of this function is to locate the correct session and bind to it,
 252  * or create a session if necessary and bind to it, then run the WebCit
 253  * transaction loop.  Afterwards, we unbind from the session.  When this
 254  * function returns, the worker thread is then free to handle another
 255  * transaction.
 256  */
 257 void context_loop(int sock)
 258 {
 259         struct httprequest *req = NULL;
 260         struct httprequest *last = NULL;
 261         struct httprequest *hptr;
 262         char buf[SIZ], hold[SIZ];
 263         int desired_session = 0;
 264         int got_cookie = 0;
 265         struct wcsession *TheSession, *sptr;
 266         char httpauth_string[SIZ];
 267         char httpauth_user[SIZ];
 268         char httpauth_pass[SIZ];
 269
 270         strcpy(httpauth_string, "");
 271         strcpy(httpauth_user, "");
 272         strcpy(httpauth_pass, "");
 273
 274         /*
 275          * Find out what it is that the web browser is asking for
 276          */
 277         memset(hold, 0, sizeof(hold));
 278         do {
 279                 if (req_gets(sock, buf, hold) < 0) return;
 280
 281                 /*
 282                  * Browser-based sessions use cookies for session authentication
 283                  */
 284                 if (!strncasecmp(buf, "Cookie: webcit=", 15)) {
 285                         cookie_to_stuff(&buf[15], &desired_session,
 286                                 NULL, NULL, NULL);
 287                         got_cookie = 1;
 288                 }
 289
 290                 /*
 291                  * GroupDAV-based sessions use HTTP authentication
 292                  */
 293                 if (!strncasecmp(buf, "Authorization: Basic ", 21)) {
 294                         CtdlDecodeBase64(httpauth_string, &buf[21], strlen(&buf[21]));
 295                         extract_token(httpauth_user, httpauth_string, 0, ':');
 296                         extract_token(httpauth_pass, httpauth_string, 1, ':');
 297                 }
 298
 299                 /*
 300                  * Read in the request
 301                  */
 302                 hptr = (struct httprequest *)
 303                         malloc(sizeof(struct httprequest));
 304                 if (req == NULL)
 305                         req = hptr;
 306                 else
 307                         last->next = hptr;
 308                 hptr->next = NULL;
 309                 last = hptr;
 310
 311                 safestrncpy(hptr->line, buf, sizeof hptr->line);
 312
 313         } while (strlen(buf) > 0);
 314
 315         safestrncpy(buf, req->line, sizeof buf);
 316         lprintf(5, "HTTP: %s\n", buf);
 317
 318         /* Check for bogus requests */
 319         if (is_bogus(buf)) goto bail;
 320
 321         /*
 322          * If requesting a non-root page, there should already be a cookie
 323          * set.  If there isn't, the client browser has cookies turned off
 324          * (or doesn't support them) and we have to barf & bail.
 325          */
 326         remove_token(buf, 0, ' ');
 327         if (buf[1]==' ') buf[1]=0;
 328
 329         /*
 330          * While we're at it, gracefully handle requests for the
 331          * robots.txt and favicon.ico files.
 332          */
 333         if (!strncasecmp(buf, "/robots.txt", 11)) {
 334                 strcpy(req->line, "GET /static/robots.txt"
 335                                 "?force_close_session=yes HTTP/1.0");
 336         }
 337         else if (!strncasecmp(buf, "/favicon.ico", 12)) {
 338                 strcpy(req->line, "GET /static/favicon.ico");
 339         }
 340
 341         /* These are the URL's which may be executed without a
 342          * session cookie already set.  If it's not one of these,
 343          * force the session to close because cookies are
 344          * probably disabled on the client browser.
 345          */
 346         else if ( (strcmp(buf, "/"))
 347                 && (strncasecmp(buf, "/listsub", 8))
 348                 && (strncasecmp(buf, "/freebusy", 9))
 349                 && (strncasecmp(buf, "/do_logout", 10))
 350                 && (strncasecmp(buf, "/groupdav", 9))
 351                 && (got_cookie == 0)) {
 352                 strcpy(req->line, "GET /static/nocookies.html"
 353                                 "?force_close_session=yes HTTP/1.0");
 354         }
 355
 356         /*
 357          * See if there's an existing session open with the desired ID or user/pass
 358          */
 359         TheSession = NULL;
 360
 361         if ( (TheSession == NULL) && (strlen(httpauth_user) > 0) ) {
 362                 pthread_mutex_lock(&SessionListMutex);
 363                 for (sptr = SessionList; sptr != NULL; sptr = sptr->next) {
 364                         if ( (!strcasecmp(sptr->httpauth_user, httpauth_user))
 365                            &&(!strcasecmp(sptr->httpauth_pass, httpauth_pass)) ) {
 366                                 TheSession = sptr;
 367                         }
 368                 }
 369                 pthread_mutex_unlock(&SessionListMutex);
 370         }
 371
 372         if ( (TheSession == NULL) && (desired_session != 0) ) {
 373                 pthread_mutex_lock(&SessionListMutex);
 374                 for (sptr = SessionList; sptr != NULL; sptr = sptr->next) {
 375                         if (sptr->wc_session == desired_session) {
 376                                 TheSession = sptr;
 377                         }
 378                 }
 379                 pthread_mutex_unlock(&SessionListMutex);
 380         }
 381
 382         /*
 383          * Create a new session if we have to
 384          */
 385         if (TheSession == NULL) {
 386                 lprintf(3, "Creating a new session\n");
 387                 TheSession = (struct wcsession *)
 388                         malloc(sizeof(struct wcsession));
 389                 memset(TheSession, 0, sizeof(struct wcsession));
 390                 TheSession->serv_sock = (-1);
 391                 TheSession->chat_sock = (-1);
 392                 TheSession->wc_session = GenerateSessionID();
 393                 strcpy(TheSession->httpauth_user, httpauth_user);
 394                 strcpy(TheSession->httpauth_pass, httpauth_pass);
 395                 pthread_mutex_init(&TheSession->SessionMutex, NULL);
 396
 397                 pthread_mutex_lock(&SessionListMutex);
 398                 TheSession->next = SessionList;
 399                 SessionList = TheSession;
 400                 pthread_mutex_unlock(&SessionListMutex);
 401         }
 402
 403         /*
 404          * A future improvement might be to check the session integrity
 405          * at this point before continuing.
 406          */
 407
 408         /*
 409          * Bind to the session and perform the transaction
 410          */
 411         pthread_mutex_lock(&TheSession->SessionMutex);          /* bind */
 412         pthread_setspecific(MyConKey, (void *)TheSession);
 413         TheSession->http_sock = sock;
 414         TheSession->lastreq = time(NULL);                       /* log */
 415         session_loop(req);                              /* do transaction */
 416         pthread_mutex_unlock(&TheSession->SessionMutex);        /* unbind */
 417
 418         /* Free the request buffer */
 419 bail:   while (req != NULL) {
 420                 hptr = req->next;
 421                 free(req);
 422                 req = hptr;
 423         }
 424
 425         /* Free up any session-local substitution variables which
 426          * were set during this transaction
 427          */
 428         clear_local_substs();
 429 }