command.c

   1 /*
   2  * Copyright (C) 1997-2008 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file command.c Client authentication and server commands. */
   8
   9 #include <signal.h>
  10 #include <sys/time.h>
  11 #include <sys/types.h>
  12 #include <dirent.h>
  13 #include <openssl/rc4.h>
  14
  15 #include "para.h"
  16 #include "error.h"
  17 #include "server.cmdline.h"
  18 #include "string.h"
  19 #include "afh.h"
  20 #include "afs.h"
  21 #include "server.h"
  22 #include "vss.h"
  23 #include "list.h"
  24 #include "send.h"
  25 #include "rc4.h"
  26 #include "net.h"
  27 #include "daemon.h"
  28 #include "fd.h"
  29 #include "ipc.h"
  30 #include "user_list.h"
  31 #include "server_command_list.h"
  32 #include "afs_command_list.h"
  33
  34 /** Commands including options must be shorter than this. */
  35 #define MAX_COMMAND_LEN 32768
  36
  37 static RC4_KEY rc4_recv_key;
  38 static RC4_KEY rc4_send_key;
  39 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  40
  41 extern int mmd_mutex;
  42 extern struct misc_meta_data *mmd;
  43 extern struct sender senders[];
  44
  45 static void dummy(int s)
  46 {
  47         /*
  48          * At least on Solaris, SIGUSR1 is one-shot, i.e. the signal action is
  49          * restored to the default state once the signal handler has been
  50          * called.
  51          */
  52         if (s == SIGUSR1)
  53                 signal(SIGUSR1, dummy);
  54 }
  55
  56 static void mmd_dup(struct misc_meta_data *new_mmd)
  57 {
  58         mutex_lock(mmd_mutex);
  59         *new_mmd = *mmd;
  60         mutex_unlock(mmd_mutex);
  61 }
  62
  63 /*
  64  * Compute human readable string containing vss status for given integer value.
  65  *
  66  * We don't want to use vss_playing() and friends here because we take a
  67  * snapshot of the mmd struct and use the copy for computing the state of the
  68  * vss. If the real data were used, we would take the mmd lock for a rather
  69  * long time or risk to get an inconsistent view.
  70  */
  71 static char *vss_status_tohuman(unsigned int flags)
  72 {
  73         if (flags & VSS_PLAYING)
  74                 return para_strdup("playing");
  75         if (flags & VSS_NEXT)
  76                 return para_strdup("stopped");
  77         return para_strdup("paused");
  78 }
  79
  80 /*
  81  * return human readable permission string. Never returns NULL.
  82  */
  83 static char *cmd_perms_itohuman(unsigned int perms)
  84 {
  85         char *msg = para_malloc(5 * sizeof(char));
  86
  87         msg[0] = perms & AFS_READ? 'a' : '-';
  88         msg[1] = perms & AFS_WRITE? 'A' : '-';
  89         msg[2] = perms & VSS_READ? 'v' : '-';
  90         msg[3] = perms & VSS_WRITE? 'V' : '-';
  91         msg[4] = '\0';
  92         return msg;
  93 }
  94
  95 /*
  96  * Never returns NULL.
  97  */
  98 static char *vss_get_status_flags(unsigned int flags)
  99 {
 100         char *msg = para_malloc(5 * sizeof(char));
 101
 102         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
 103         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
 104         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 105         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 106         msg[4] = '\0';
 107         return msg;
 108 }
 109
 110 static char *get_status(struct misc_meta_data *nmmd)
 111 {
 112         char *ret, mtime[30] = "";
 113         char *status, *flags; /* vss status info */
 114         char *ut = uptime_str();
 115         long offset = (nmmd->offset + 500) / 1000;
 116         struct timeval now;
 117         struct tm mtime_tm;
 118
 119         /* report real status */
 120         status = vss_status_tohuman(nmmd->vss_status_flags);
 121         flags = vss_get_status_flags(nmmd->vss_status_flags);
 122         if (nmmd->size) { /* parent currently has an audio file open */
 123                 localtime_r(&nmmd->mtime, &mtime_tm);
 124                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 125         }
 126         gettimeofday(&now, NULL);
 127         ret = make_message(
 128                 "%s: %zu\n" /* file size */
 129                 "%s: %s\n" /* mtime */
 130                 "%s: %s\n" /* status */
 131                 "%s: %s\n" /* status flags */
 132                 "%s: %li\n" /* offset */
 133                 "%s: %s\n" /* afs mode */
 134                 "%s: %lu.%lu\n" /* stream start */
 135                 "%s: %lu.%lu\n" /* current server time */
 136                 "%s", /* afs status info */
 137                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 138                 status_item_list[SI_MTIME], mtime,
 139                 status_item_list[SI_STATUS], status,
 140                 status_item_list[SI_STATUS_FLAGS], flags,
 141
 142                 status_item_list[SI_OFFSET], offset,
 143                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 144
 145                 status_item_list[SI_STREAM_START],
 146                         (long unsigned)nmmd->stream_start.tv_sec,
 147                         (long unsigned)nmmd->stream_start.tv_usec,
 148                 status_item_list[SI_CURRENT_TIME],
 149                         (long unsigned)now.tv_sec,
 150                         (long unsigned)now.tv_usec,
 151
 152                 nmmd->afd.verbose_ls_output
 153
 154         );
 155         free(flags);
 156         free(status);
 157         free(ut);
 158         return ret;
 159 }
 160
 161 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 162 {
 163         int i;
 164         /* this has to match sender.h */
 165         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 166
 167         scd->sender_num = -1;
 168         if (argc < 2)
 169                 return -E_COMMAND_SYNTAX;
 170         for (i = 0; senders[i].name; i++)
 171                 if (!strcmp(senders[i].name, argv[1]))
 172                         break;
 173         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 174         if (!senders[i].name)
 175                 return -E_COMMAND_SYNTAX;
 176         scd->sender_num = i;
 177         for (i = 0; subcmds[i]; i++)
 178                 if (!strcmp(subcmds[i], argv[2]))
 179                         break;
 180         if (!subcmds[i])
 181                 return -E_COMMAND_SYNTAX;
 182         scd->cmd_num = i;
 183         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 184                 return -E_SENDER_CMD;
 185         switch (scd->cmd_num) {
 186         case SENDER_ON:
 187         case SENDER_OFF:
 188                 if (argc != 3)
 189                         return -E_COMMAND_SYNTAX;
 190                 break;
 191         case SENDER_DENY:
 192         case SENDER_ALLOW:
 193                 if (argc != 4 && argc != 5)
 194                         return -E_COMMAND_SYNTAX;
 195                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 196                         return -E_COMMAND_SYNTAX;
 197                 scd->netmask = 32;
 198                 if (argc == 5) {
 199                         scd->netmask = atoi(argv[4]);
 200                         if (scd->netmask < 0 || scd->netmask > 32)
 201                                 return -E_COMMAND_SYNTAX;
 202                 }
 203                 break;
 204         case SENDER_ADD:
 205         case SENDER_DELETE:
 206                 if (argc != 4 && argc != 5)
 207                         return -E_COMMAND_SYNTAX;
 208                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 209                         return -E_COMMAND_SYNTAX;
 210                 scd->port = -1;
 211                 if (argc == 5) {
 212                         scd->port = atoi(argv[4]);
 213                         if (scd->port < 0 || scd->port > 65535)
 214                                 return -E_COMMAND_SYNTAX;
 215                 }
 216                 break;
 217         default:
 218                 return -E_COMMAND_SYNTAX;
 219         }
 220         return 1;
 221 }
 222
 223 int com_sender(int fd, int argc, char * const * argv)
 224 {
 225         int i, ret;
 226         struct sender_command_data scd;
 227
 228         if (argc < 2) {
 229                 char *msg = NULL;
 230                 for (i = 0; senders[i].name; i++) {
 231                         char *tmp = make_message("%s%s\n",
 232                                 msg? msg : "", senders[i].name);
 233                         free(msg);
 234                         msg = tmp;
 235                 }
 236                 ret = send_buffer(fd, msg);
 237                 free(msg);
 238                 return ret;
 239         }
 240         ret = check_sender_args(argc, argv, &scd);
 241         if (ret < 0) {
 242                 char *msg;
 243                 if (scd.sender_num < 0)
 244                         return ret;
 245                 msg = senders[scd.sender_num].help();
 246                 ret = send_buffer(fd, msg);
 247                 free(msg);
 248                 return ret;
 249         }
 250         for (i = 0; i < 10; i++) {
 251                 mutex_lock(mmd_mutex);
 252                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 253                         mutex_unlock(mmd_mutex);
 254                         usleep(100 * 1000);
 255                         continue;
 256                 }
 257                 mmd->sender_cmd_data = scd;
 258                 mutex_unlock(mmd_mutex);
 259                 break;
 260         }
 261         return (i < 10)? 1 : -E_LOCK;
 262 }
 263
 264 /* server info */
 265 int com_si(int fd, int argc, __a_unused char * const * argv)
 266 {
 267         int i, ret;
 268         char *ut;
 269         char *sender_info = NULL, *sender_list = NULL;
 270
 271         if (argc != 1)
 272                 return -E_COMMAND_SYNTAX;
 273         mutex_lock(mmd_mutex);
 274         for (i = 0; senders[i].name; i++) {
 275                 char *info = senders[i].info();
 276                 sender_info = para_strcat(sender_info, info);
 277                 free(info);
 278                 sender_list = para_strcat(sender_list, senders[i].name);
 279                 sender_list = para_strcat(sender_list, " ");
 280         }
 281         ut = uptime_str();
 282         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 283                 "pid: %d\n"
 284                 "connections (active/accepted/total): %u/%u/%u\n"
 285                 "current loglevel: %i\n"
 286                 "supported audio formats: %s\n"
 287                 "supported senders: %s\n"
 288                 "%s",
 289                 ut, mmd->num_played,
 290                 (int)getppid(),
 291                 mmd->active_connections,
 292                 mmd->num_commands,
 293                 mmd->num_connects,
 294                 conf.loglevel_arg,
 295                 supported_audio_formats(),
 296                 sender_list,
 297                 sender_info
 298         );
 299         mutex_unlock(mmd_mutex);
 300         free(ut);
 301         free(sender_list);
 302         free(sender_info);
 303         return ret;
 304 }
 305
 306 /* version */
 307 int com_version(int fd, int argc, __a_unused char * const * argv)
 308 {
 309         if (argc != 1)
 310                 return -E_COMMAND_SYNTAX;
 311         return send_buffer(fd, VERSION_TEXT("server")
 312                 "built: " BUILD_DATE "\n"
 313                 UNAME_RS ", " CC_VERSION "\n"
 314         );
 315 }
 316
 317 /* stat */
 318 int com_stat(int fd, int argc, char * const * argv)
 319 {
 320         int ret, num = 0;/* status will be printed that many
 321                           * times. num <= 0 means: print forever
 322                           */
 323         struct misc_meta_data tmp, *nmmd = &tmp;
 324         char *s;
 325
 326         signal(SIGUSR1, dummy);
 327
 328         if (argc > 1)
 329                 num = atoi(argv[1]);
 330         for (;;) {
 331
 332                 mmd_dup(nmmd);
 333                 s = get_status(nmmd);
 334                 ret = send_buffer(fd, s);
 335                 free(s);
 336                 if (ret < 0)
 337                         goto out;
 338                 ret = 1;
 339                 if (num > 0 && !--num)
 340                         goto out;
 341                 sleep(50);
 342                 if (getppid() == 1)
 343                         return -E_SERVER_CRASH;
 344         }
 345 out:
 346         return ret;
 347 }
 348
 349 static int send_list_of_commands(int fd, struct server_command *cmd,
 350                 const char *handler)
 351 {
 352         int ret, i;
 353
 354         for (i = 1; cmd->name; cmd++, i++) {
 355                 char *perms = cmd_perms_itohuman(cmd->perms);
 356                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 357                         handler,
 358                         perms,
 359                         cmd->description);
 360                 free(perms);
 361                 if (ret < 0)
 362                         return ret;
 363         }
 364         return 1;
 365 }
 366
 367 /* returns string that must be freed by the caller */
 368 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 369 {
 370         struct server_command *cmd;
 371
 372         for (cmd = server_cmds; cmd->name; cmd++)
 373                 if (!strcmp(cmd->name, name)) {
 374                         if (handler)
 375                                 *handler = para_strdup("server"); /* server commands */
 376                         return cmd;
 377                 }
 378         /* not found, look for commands supported by afs */
 379         for (cmd = afs_cmds; cmd->name; cmd++)
 380                 if (!strcmp(cmd->name, name)) {
 381                         if (handler)
 382                                 *handler = para_strdup("afs");
 383                         return cmd;
 384                 }
 385         return NULL;
 386 }
 387
 388 /* help */
 389 int com_help(int fd, int argc, char * const * argv)
 390 {
 391         struct server_command *cmd;
 392         char *perms, *handler;
 393         int ret;
 394
 395         if (argc < 2) {
 396                 /* no argument given, print list of commands */
 397                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 398                         return ret;
 399                 return send_list_of_commands(fd, afs_cmds, "afs");
 400         }
 401         /* argument given for help */
 402         cmd = get_cmd_ptr(argv[1], &handler);
 403         if (!cmd) {
 404                 free(handler);
 405                 return -E_BAD_CMD;
 406         }
 407         perms = cmd_perms_itohuman(cmd->perms);
 408         ret = send_va_buffer(fd,
 409                 "%s - %s\n\n"
 410                 "handler: %s\n"
 411                 "permissions: %s\n"
 412                 "usage: %s\n\n"
 413                 "%s\n",
 414                 argv[1],
 415                 cmd->description,
 416                 handler,
 417                 perms,
 418                 cmd->usage,
 419                 cmd->help
 420         );
 421         free(perms);
 422         free(handler);
 423         return ret;
 424 }
 425
 426 /* hup */
 427 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 428 {
 429         if (argc != 1)
 430                 return -E_COMMAND_SYNTAX;
 431         kill(getppid(), SIGHUP);
 432         return 1;
 433 }
 434
 435 /* term */
 436 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 437 {
 438         if (argc != 1)
 439                 return -E_COMMAND_SYNTAX;
 440         kill(getppid(), SIGTERM);
 441         return 1;
 442 }
 443
 444 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 445 {
 446         if (argc != 1)
 447                 return -E_COMMAND_SYNTAX;
 448         mutex_lock(mmd_mutex);
 449         mmd->new_vss_status_flags |= VSS_PLAYING;
 450         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 451         mutex_unlock(mmd_mutex);
 452         return 1;
 453
 454 }
 455
 456 /* stop */
 457 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 458 {
 459         if (argc != 1)
 460                 return -E_COMMAND_SYNTAX;
 461         mutex_lock(mmd_mutex);
 462         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 463         mmd->new_vss_status_flags &= ~VSS_REPOS;
 464         mmd->new_vss_status_flags |= VSS_NEXT;
 465         mutex_unlock(mmd_mutex);
 466         return 1;
 467 }
 468
 469 /* pause */
 470 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 471 {
 472         if (argc != 1)
 473                 return -E_COMMAND_SYNTAX;
 474         mutex_lock(mmd_mutex);
 475         if (!vss_paused() && !vss_stopped()) {
 476                 mmd->events++;
 477                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 478                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 479         }
 480         mutex_unlock(mmd_mutex);
 481         return 1;
 482 }
 483
 484 /* next */
 485 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 486 {
 487         if (argc != 1)
 488                 return -E_COMMAND_SYNTAX;
 489         mutex_lock(mmd_mutex);
 490         mmd->events++;
 491         mmd->new_vss_status_flags |= VSS_NEXT;
 492         mutex_unlock(mmd_mutex);
 493         return 1;
 494 }
 495
 496 /* nomore */
 497 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 498 {
 499         if (argc != 1)
 500                 return -E_COMMAND_SYNTAX;
 501         mutex_lock(mmd_mutex);
 502         if (vss_playing() || vss_paused())
 503                 mmd->new_vss_status_flags |= VSS_NOMORE;
 504         mutex_unlock(mmd_mutex);
 505         return 1;
 506 }
 507
 508 /* ff */
 509 int com_ff(__a_unused int fd, int argc, char * const * argv)
 510 {
 511         long promille;
 512         int ret, backwards = 0;
 513         unsigned i;
 514         char c;
 515
 516         if (argc != 2)
 517                 return -E_COMMAND_SYNTAX;
 518         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 519                 return -E_COMMAND_SYNTAX;
 520         if (ret > 1 && c == '-')
 521                 backwards = 1; /* jmp backwards */
 522         mutex_lock(mmd_mutex);
 523         ret = -E_NO_AUDIO_FILE;
 524         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 525                 goto out;
 526         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 527         if (backwards)
 528                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 529         else
 530                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 531         if (promille < 0)
 532                 promille = 0;
 533         if (promille >  1000) {
 534                 mmd->new_vss_status_flags |= VSS_NEXT;
 535                 goto out;
 536         }
 537         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 538         mmd->new_vss_status_flags |= VSS_REPOS;
 539         mmd->new_vss_status_flags &= ~VSS_NEXT;
 540         mmd->events++;
 541         ret = 1;
 542 out:
 543         mutex_unlock(mmd_mutex);
 544         return ret;
 545 }
 546
 547 /* jmp */
 548 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 549 {
 550         long unsigned int i;
 551         int ret;
 552
 553         if (argc != 2)
 554                 return -E_COMMAND_SYNTAX;
 555         if (sscanf(argv[1], "%lu", &i) <= 0)
 556                 return -E_COMMAND_SYNTAX;
 557         mutex_lock(mmd_mutex);
 558         ret = -E_NO_AUDIO_FILE;
 559         if (!mmd->afd.afhi.chunks_total)
 560                 goto out;
 561         if (i > 100)
 562                 i = 100;
 563         PARA_INFO_LOG("jumping to %lu%%\n", i);
 564         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 565         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 566                 mmd->chunks_sent, mmd->offset);
 567         mmd->new_vss_status_flags |= VSS_REPOS;
 568         mmd->new_vss_status_flags &= ~VSS_NEXT;
 569         ret = 1;
 570         mmd->events++;
 571 out:
 572         mutex_unlock(mmd_mutex);
 573         return ret;
 574 }
 575
 576 /*
 577  * check if perms are sufficient to exec a command having perms cmd_perms.
 578  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 579  */
 580 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 581 {
 582         PARA_DEBUG_LOG("checking permissions\n");
 583         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 584 }
 585
 586 /*
 587  * Parse first string from *cmd and lookup in table of valid commands.
 588  * On error, NULL is returned.
 589  */
 590 static struct server_command *parse_cmd(const char *cmdstr)
 591 {
 592         char buf[255];
 593         int n = 0;
 594
 595         sscanf(cmdstr, "%200s%n", buf, &n);
 596         if (!n)
 597                 return NULL;
 598         buf[n] = '\0';
 599         return get_cmd_ptr(buf, NULL);
 600 }
 601
 602 static void init_rc4_keys(void)
 603 {
 604         int i;
 605
 606         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 607                 rc4_buf[i] = para_random(256);
 608         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 609                 (unsigned char) rc4_buf[0],
 610                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 611         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 612         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 613 }
 614
 615 static void rc4_recv(unsigned long len, const unsigned char *indata,
 616                 unsigned char *outdata, __a_unused void *private_data)
 617 {
 618         RC4(&rc4_recv_key, len, indata, outdata);
 619 }
 620
 621 static void rc4_send(unsigned long len, const unsigned char *indata,
 622                 unsigned char *outdata, __a_unused void *private_data)
 623 {
 624         RC4(&rc4_send_key, len, indata, outdata);
 625 }
 626
 627 static int read_command(int fd, char **result)
 628 {
 629         int ret;
 630         char buf[4096];
 631         char *command = NULL;
 632
 633         for (;;) {
 634                 size_t numbytes;
 635                 char *p;
 636
 637                 ret = recv_buffer(fd, buf, sizeof(buf));
 638                 if (ret < 0)
 639                         goto out;
 640                 if (!ret)
 641                         break;
 642                 numbytes = ret;
 643                 ret = -E_COMMAND_SYNTAX;
 644                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 645                         goto out;
 646                 command = para_strcat(command, buf);
 647                 p = strstr(command, EOC_MSG);
 648                 if (p) {
 649                         *p = '\0';
 650                         break;
 651                 }
 652         }
 653         ret = command? 1 : -E_COMMAND_SYNTAX;
 654 out:
 655         if (ret < 0)
 656                 free(command);
 657         else
 658                 *result = command;
 659         return ret;
 660
 661 }
 662
 663 /**
 664  * Perform user authentication and execute a command.
 665  *
 666  * \param fd The file descriptor to send output to.
 667  * \param peername Identifies the connecting peer.
 668  *
 669  * Whenever para_server accepts an incoming tcp connection on
 670  * the port it listens on, it forks and the resulting child
 671  * calls this function.
 672  *
 673  * An RSA-based challenge/response is used to authenticate
 674  * the peer. It that authentication succeeds, a random RC4
 675  * session key is generated and sent back to the peer,
 676  * encrypted with its RSA public key.  From this point on,
 677  * all transfers are crypted with this session key.
 678  *
 679  * Next it is checked if the peer supplied  a valid server command or a command
 680  * for the audio file selector.  If yes, and if the user has sufficient
 681  * permissions to execute that command, the function calls the corresponding
 682  * command handler which does argument checking and further processing.
 683  *
 684  * In order to cope with a DOS attacks, a timeout is set up
 685  * which terminates the function if the connection was not
 686  * authenticated when the timeout expires.
 687  *
 688  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 689  */
 690 __noreturn void handle_connect(int fd, const char *peername)
 691 {
 692         int ret, argc, use_rc4 = 0;
 693         char buf[4096];
 694         unsigned char crypt_buf[MAXLINE];
 695         struct user *u;
 696         struct server_command *cmd = NULL;
 697         long unsigned challenge_nr, chall_response;
 698         char **argv = NULL;
 699         char *p, *command = NULL;
 700         size_t numbytes;
 701
 702         signal(SIGCHLD, SIG_IGN);
 703         signal(SIGINT, SIG_DFL);
 704         signal(SIGTERM, SIG_DFL);
 705         signal(SIGHUP, SIG_DFL);
 706
 707         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 708         ret = mark_fd_blocking(fd);
 709         if (ret < 0)
 710                 goto err_out;
 711         challenge_nr = random();
 712         /* send Welcome message */
 713         ret = send_va_buffer(fd, "This is para_server, version "
 714                 PACKAGE_VERSION  ".\n" );
 715         if (ret < 0)
 716                 goto err_out;
 717         /* recv auth request line */
 718         ret = recv_buffer(fd, buf, sizeof(buf));
 719         if (ret < 0)
 720                 goto err_out;
 721         if (ret <= 6) {
 722                 ret = -E_AUTH;
 723                 goto err_out;
 724         }
 725         numbytes = ret;
 726         ret = -E_AUTH;
 727         if (strncmp(buf, "auth ", 5))
 728                 goto err_out;
 729
 730         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 731                 p = buf + 5; /* client version < 0.2.6 */
 732         else {
 733                 p = buf + 9; /* client version >= 0.2.6 */
 734                 use_rc4 = 1;
 735         }
 736         PARA_DEBUG_LOG("received %s request for user %s\n",
 737                 use_rc4? "rc4" : "auth", p);
 738         ret = -E_BAD_USER;
 739         u = lookup_user(p);
 740         if (!u)
 741                 goto err_out;
 742         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 743         if (ret <= 0)
 744                 goto err_out;
 745         numbytes = ret;
 746         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 747         /* We can't use send_buffer here since buf may contain null bytes */
 748         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 749         if (ret < 0)
 750                 goto net_err;
 751         /* recv decrypted number */
 752         ret = recv_buffer(fd, buf, sizeof(buf));
 753         if (ret < 0)
 754                 goto net_err;
 755         numbytes = ret;
 756         ret = -E_AUTH;
 757         if (!numbytes)
 758                 goto net_err;
 759         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 760                         || chall_response != challenge_nr)
 761                 goto err_out;
 762         /* auth successful, send 'Proceed' message */
 763         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 764         sprintf(buf, "%s", PROCEED_MSG);
 765         if (use_rc4) {
 766                 init_rc4_keys();
 767                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 768                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 769                 if (ret <= 0)
 770                         goto err_out;
 771                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 772         } else
 773                 numbytes = strlen(buf);
 774         ret = send_bin_buffer(fd, buf, numbytes);
 775         if (ret < 0)
 776                 goto net_err;
 777         if (use_rc4)
 778                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 779         ret = read_command(fd, &command);
 780         if (ret == -E_COMMAND_SYNTAX)
 781                 goto err_out;
 782         if (ret < 0)
 783                 goto net_err;
 784         ret = -E_BAD_CMD;
 785         cmd = parse_cmd(command);
 786         if (!cmd)
 787                 goto err_out;
 788         /* valid command, check permissions */
 789         ret = check_perms(u->perms, cmd);
 790         if (ret < 0)
 791                 goto err_out;
 792         /* valid command and sufficient perms */
 793         alarm(0);
 794         argc = split_args(command, &argv, "\n");
 795         mutex_lock(mmd_mutex);
 796         mmd->num_commands++;
 797         mutex_unlock(mmd_mutex);
 798         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 799                         peername);
 800         ret = cmd->handler(fd, argc, argv);
 801         if (ret >= 0)
 802                 goto out;
 803 err_out:
 804         send_va_buffer(fd, "%s\n", para_strerror(-ret));
 805 net_err:
 806         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 807 out:
 808         free(command);
 809         free(argv);
 810         mutex_lock(mmd_mutex);
 811         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 812                 mmd->events++;
 813         mmd->active_connections--;
 814         mutex_unlock(mmd_mutex);
 815         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 816 }