command.c

   1 /*
   2  * Copyright (C) 1997-2007 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 "send.h"
  24 #include "rc4.h"
  25 #include "net.h"
  26 #include "daemon.h"
  27 #include "fd.h"
  28 #include "list.h"
  29 #include "user_list.h"
  30 #include "server_command_list.h"
  31 #include "afs_command_list.h"
  32
  33 /** Commands including options must be shorter than this. */
  34 #define MAX_COMMAND_LEN 32768
  35
  36 static RC4_KEY rc4_recv_key;
  37 static RC4_KEY rc4_send_key;
  38 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  39
  40 extern const char *status_item_list[NUM_STAT_ITEMS];
  41 extern struct misc_meta_data *mmd;
  42 extern struct sender senders[];
  43
  44 static void dummy(__a_unused int s)
  45 {}
  46
  47 static void mmd_dup(struct misc_meta_data *new_mmd)
  48 {
  49         mmd_lock();
  50         *new_mmd = *mmd;
  51         mmd_unlock();
  52 }
  53
  54 /*
  55  * compute human readable string containing
  56  * vss status for given integer value
  57  */
  58 static char *vss_status_tohuman(unsigned int flags)
  59 {
  60         if (flags & VSS_PLAYING)
  61                 return para_strdup("playing");
  62         else if (flags & VSS_NEXT)
  63                 return para_strdup("stopped");
  64         else
  65                 return para_strdup("paused");
  66 }
  67
  68 /*
  69  * return human readable permission string. Never returns NULL.
  70  */
  71 static char *cmd_perms_itohuman(unsigned int perms)
  72 {
  73         char *msg = para_malloc(5 * sizeof(char));
  74
  75         msg[0] = perms & AFS_READ? 'a' : '-';
  76         msg[1] = perms & AFS_WRITE? 'A' : '-';
  77         msg[2] = perms & VSS_READ? 'v' : '-';
  78         msg[3] = perms & VSS_WRITE? 'V' : '-';
  79         msg[4] = '\0';
  80         return msg;
  81 }
  82
  83 /*
  84  * Never returns NULL.
  85  */
  86 static char *vss_get_status_flags(unsigned int flags)
  87 {
  88         char *msg = para_malloc(5 * sizeof(char));
  89
  90         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  91         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
  92         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
  93         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
  94         msg[4] = '\0';
  95         return msg;
  96 }
  97
  98 static char *get_status(struct misc_meta_data *nmmd)
  99 {
 100         char *basename, *dirname, *ret, mtime[30] = "";
 101         char *status, *flags; /* vss status info */
 102         char *ut = uptime_str();
 103         long offset = (nmmd->offset + 500) / 1000;
 104         struct timeval now;
 105         struct tm mtime_tm;
 106
 107         /* report real status */
 108         status = vss_status_tohuman(nmmd->vss_status_flags);
 109         flags = vss_get_status_flags(nmmd->vss_status_flags);
 110         basename = para_basename(nmmd->afd.path);
 111         dirname = para_dirname(nmmd->afd.path);
 112         if (basename) {
 113                 localtime_r(&nmmd->mtime, &mtime_tm);
 114                 strftime(mtime, 29, "%a %b %d %Y", &mtime_tm);
 115         }
 116         gettimeofday(&now, NULL);
 117         ret = make_message(
 118                 "%s:%zu\n"      "%s:%s\n"               "%s:%lu\n"      "%s:%u\n"
 119                 "%s:%s\n"       "%s:%s\n"       "%s:%s\n"       "%s:%u\n"
 120                 "%s:%li\n"      "%s:%s\n" "%s"
 121                 "%s:%s\n"       "%s:%lu.%lu\n"  "%s:%lu.%lu\n"
 122                 "%s:%s\n"       "%s:%u\n"       "%s\n",
 123                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 124                 status_item_list[SI_MTIME], mtime,
 125                 status_item_list[SI_LENGTH], nmmd->afd.afhi.seconds_total,
 126                 status_item_list[SI_NUM_PLAYED], nmmd->num_played,
 127
 128                 status_item_list[SI_BASENAME], basename ? basename : "(none)",
 129                 status_item_list[SI_STATUS], status,
 130                 status_item_list[SI_STATUS_FLAGS], flags,
 131                 status_item_list[SI_IMAGE_ID], nmmd->afd.afsi.image_id,
 132
 133                 status_item_list[SI_OFFSET], offset,
 134                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 135                 nmmd->afd.afhi.info_string,
 136
 137                 status_item_list[SI_UPTIME], ut,
 138                 status_item_list[SI_STREAM_START],
 139                         (long unsigned)nmmd->stream_start.tv_sec,
 140                         (long unsigned)nmmd->stream_start.tv_usec,
 141                 status_item_list[SI_CURRENT_TIME],
 142                         (long unsigned)now.tv_sec,
 143                         (long unsigned)now.tv_usec,
 144
 145                 status_item_list[SI_DIRECTORY], dirname? dirname : "(none)",
 146                 status_item_list[SI_LYRICS_ID], nmmd->afd.afsi.lyrics_id,
 147                 nmmd->afd.afs_status_info
 148
 149         );
 150         free(basename);
 151         free(dirname);
 152         free(flags);
 153         free(status);
 154         free(ut);
 155         return ret;
 156 }
 157
 158 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 159 {
 160         int i;
 161         /* this has to match sender.h */
 162         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 163
 164         scd->sender_num = -1;
 165         if (argc < 2)
 166                 return -E_COMMAND_SYNTAX;
 167         for (i = 0; senders[i].name; i++)
 168                 if (!strcmp(senders[i].name, argv[1]))
 169                         break;
 170         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 171         if (!senders[i].name)
 172                 return -E_COMMAND_SYNTAX;
 173         scd->sender_num = i;
 174         for (i = 0; subcmds[i]; i++)
 175                 if (!strcmp(subcmds[i], argv[2]))
 176                         break;
 177         if (!subcmds[i])
 178                 return -E_COMMAND_SYNTAX;
 179         scd->cmd_num = i;
 180         mmd_lock();
 181         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 182                 mmd_unlock();
 183                 return -E_SENDER_CMD;
 184         }
 185         mmd_unlock();
 186         switch (scd->cmd_num) {
 187         case SENDER_ON:
 188         case SENDER_OFF:
 189                 if (argc != 3)
 190                         return -E_COMMAND_SYNTAX;
 191                 break;
 192         case SENDER_DENY:
 193         case SENDER_ALLOW:
 194                 if (argc != 4 && argc != 5)
 195                         return -E_COMMAND_SYNTAX;
 196                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 197                         return -E_COMMAND_SYNTAX;
 198                 scd->netmask = 32;
 199                 if (argc == 5) {
 200                         scd->netmask = atoi(argv[4]);
 201                         if (scd->netmask < 0 || scd->netmask > 32)
 202                                 return -E_COMMAND_SYNTAX;
 203                 }
 204                 break;
 205         case SENDER_ADD:
 206         case SENDER_DELETE:
 207                 if (argc != 4 && argc != 5)
 208                         return -E_COMMAND_SYNTAX;
 209                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 210                         return -E_COMMAND_SYNTAX;
 211                 scd->port = -1;
 212                 if (argc == 5) {
 213                         scd->port = atoi(argv[4]);
 214                         if (scd->port < 0 || scd->port > 65535)
 215                                 return -E_COMMAND_SYNTAX;
 216                 }
 217                 break;
 218         default:
 219                 return -E_COMMAND_SYNTAX;
 220         }
 221         return 1;
 222 }
 223
 224 int com_sender(int fd, int argc, char * const * argv)
 225 {
 226         int i, ret;
 227         struct sender_command_data scd;
 228
 229         if (argc < 2) {
 230                 char *msg = NULL;
 231                 for (i = 0; senders[i].name; i++) {
 232                         char *tmp = make_message("%s%s\n",
 233                                 msg? msg : "", senders[i].name);
 234                         free(msg);
 235                         msg = tmp;
 236                 }
 237                 ret = send_buffer(fd, msg);
 238                 free(msg);
 239                 return ret;
 240         }
 241         ret = check_sender_args(argc, argv, &scd);
 242         if (ret < 0) {
 243                 char *msg;
 244                 if (scd.sender_num < 0)
 245                         return ret;
 246                 msg = senders[scd.sender_num].help();
 247                 send_buffer(fd, msg);
 248                 free(msg);
 249                 return 1;
 250         }
 251         for (i = 0; i < 10; i++) {
 252                 mmd_lock();
 253                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 254                         mmd_unlock();
 255                         usleep(100 * 1000);
 256                         continue;
 257                 }
 258                 mmd->sender_cmd_data = scd;
 259                 mmd_unlock();
 260                 break;
 261         }
 262         return (i < 10)? 1 : -E_LOCK;
 263 }
 264
 265 /* server info */
 266 int com_si(int fd, int argc, __a_unused char * const * argv)
 267 {
 268         int i, ret;
 269         char *ut;
 270         char *sender_info = NULL, *sender_list = NULL;
 271
 272         if (argc != 1)
 273                 return -E_COMMAND_SYNTAX;
 274         mmd_lock();
 275         for (i = 0; senders[i].name; i++) {
 276                 char *info = senders[i].info();
 277                 sender_info = para_strcat(sender_info, info);
 278                 free(info);
 279                 sender_list = para_strcat(sender_list, senders[i].name);
 280                 sender_list = para_strcat(sender_list, " ");
 281         }
 282         ut = uptime_str();
 283         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 284                 "pid: %d\n"
 285                 "connections (active/accepted/total): %u/%u/%u\n"
 286                 "current loglevel: %i\n"
 287                 "supported audio formats: %s\n"
 288                 "supported senders: %s\n"
 289                 "%s",
 290                 ut, mmd->num_played,
 291                 getppid(),
 292                 mmd->active_connections,
 293                 mmd->num_commands,
 294                 mmd->num_connects,
 295                 conf.loglevel_arg,
 296                 supported_audio_formats(),
 297                 sender_list,
 298                 sender_info
 299         );
 300         mmd_unlock();
 301         free(ut);
 302         free(sender_list);
 303         free(sender_info);
 304         return ret;
 305 }
 306
 307 /* version */
 308 int com_version(int fd, int argc, __a_unused char * const * argv)
 309 {
 310         if (argc != 1)
 311                 return -E_COMMAND_SYNTAX;
 312         return send_buffer(fd, VERSION_TEXT("server")
 313                 "built: " BUILD_DATE "\n"
 314                 SYSTEM ", " CC_VERSION "\n"
 315         );
 316 }
 317
 318 /* stat */
 319 int com_stat(int fd, int argc, char * const * argv)
 320 {
 321         int ret, num = 0;/* status will be printed that many
 322                           * times. num <= 0 means: print forever
 323                           */
 324         struct misc_meta_data tmp, *nmmd = &tmp;
 325         char *s;
 326
 327         signal(SIGUSR1, dummy);
 328
 329         if (argc > 1)
 330                 num = atoi(argv[1]);
 331         for (;;) {
 332
 333                 mmd_dup(nmmd);
 334                 s = get_status(nmmd);
 335                 ret = send_buffer(fd, s);
 336                 free(s);
 337                 if (ret < 0)
 338                         goto out;
 339                 ret = 1;
 340                 if (num == 1)
 341                         goto out;
 342                 sleep(50);
 343                 if (getppid() == 1)
 344                         return -E_SERVER_CRASH;
 345         }
 346 out:
 347         return ret;
 348 }
 349
 350 static int send_list_of_commands(int fd, struct server_command *cmd,
 351                 const char *handler)
 352 {
 353         int ret, i;
 354
 355         for (i = 1; cmd->name; cmd++, i++) {
 356                 char *perms = cmd_perms_itohuman(cmd->perms);
 357                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 358                         handler,
 359                         perms,
 360                         cmd->description);
 361                 free(perms);
 362                 if (ret < 0)
 363                         return ret;
 364         }
 365         return 1;
 366 }
 367
 368 /* returns string that must be freed by the caller */
 369 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 370 {
 371         struct server_command *cmd;
 372
 373         for (cmd = server_cmds; cmd->name; cmd++)
 374                 if (!strcmp(cmd->name, name)) {
 375                         if (handler)
 376                                 *handler = para_strdup("server"); /* server commands */
 377                         return cmd;
 378                 }
 379         /* not found, look for commands supported by afs */
 380         for (cmd = afs_cmds; cmd->name; cmd++)
 381                 if (!strcmp(cmd->name, name)) {
 382                         if (handler)
 383                                 *handler = para_strdup("afs");
 384                         return cmd;
 385                 }
 386         return NULL;
 387 }
 388
 389 /* help */
 390 int com_help(int fd, int argc, char * const * argv)
 391 {
 392         struct server_command *cmd;
 393         char *perms, *handler;
 394         int ret;
 395
 396         if (argc < 2) {
 397                 /* no argument given, print list of commands */
 398                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 399                         return ret;
 400                 return send_list_of_commands(fd, afs_cmds, "afs");
 401         }
 402         /* argument given for help */
 403         cmd = get_cmd_ptr(argv[1], &handler);
 404         if (!cmd) {
 405                 free(handler);
 406                 return -E_BAD_CMD;
 407         }
 408         perms = cmd_perms_itohuman(cmd->perms);
 409         ret = send_va_buffer(fd,
 410                 "%s - %s\n\n"
 411                 "handler: %s\n"
 412                 "permissions: %s\n"
 413                 "usage: %s\n\n"
 414                 "%s\n",
 415                 argv[1],
 416                 cmd->description,
 417                 handler,
 418                 perms,
 419                 cmd->usage,
 420                 cmd->help
 421         );
 422         free(perms);
 423         free(handler);
 424         return ret;
 425 }
 426
 427 /* hup */
 428 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 429 {
 430         if (argc != 1)
 431                 return -E_COMMAND_SYNTAX;
 432         kill(getppid(), SIGHUP);
 433         return 1;
 434 }
 435
 436 /* term */
 437 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 438 {
 439         if (argc != 1)
 440                 return -E_COMMAND_SYNTAX;
 441         kill(getppid(), SIGTERM);
 442         return 1;
 443 }
 444
 445 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 446 {
 447         if (argc != 1)
 448                 return -E_COMMAND_SYNTAX;
 449         mmd_lock();
 450         mmd->new_vss_status_flags |= VSS_PLAYING;
 451         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 452         mmd_unlock();
 453         return 1;
 454
 455 }
 456
 457 /* stop */
 458 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 459 {
 460         if (argc != 1)
 461                 return -E_COMMAND_SYNTAX;
 462         mmd_lock();
 463         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 464         mmd->new_vss_status_flags &= ~VSS_REPOS;
 465         mmd->new_vss_status_flags |= VSS_NEXT;
 466         mmd_unlock();
 467         return 1;
 468 }
 469
 470 /* pause */
 471 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 472 {
 473         if (argc != 1)
 474                 return -E_COMMAND_SYNTAX;
 475         mmd_lock();
 476         if (!vss_paused())
 477                 mmd->events++;
 478         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 479         mmd->new_vss_status_flags &= ~VSS_NEXT;
 480         mmd_unlock();
 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         mmd_lock();
 490         mmd->events++;
 491         mmd->new_vss_status_flags |= VSS_NEXT;
 492         mmd_unlock();
 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         mmd_lock();
 502         if (vss_playing() || vss_paused())
 503                 mmd->new_vss_status_flags |= VSS_NOMORE;
 504         mmd_unlock();
 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         mmd_lock();
 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         mmd_unlock();
 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         mmd_lock();
 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         mmd_unlock();
 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("%s", "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 addr socket address info of peer
 668  *
 669  * \return EXIT_SUCCESS or EXIT_FAILURE
 670  *
 671  * Whenever para_server accepts an incoming tcp connection on
 672  * the port it listens on, it forks and the resulting child
 673  * calls this function.
 674  *
 675  * An RSA-based challenge/response is used to authenticate
 676  * the peer. It that authentication succeeds, a random RC4
 677  * session key is generated and sent back to the peer,
 678  * encrypted with its RSA public key.  From this point on,
 679  * all transfers are crypted with this session key.
 680  *
 681  * Next it is checked if the peer supplied  a valid server command or a command
 682  * for the audio file selector.  If yes, and if the user has sufficient
 683  * permissions to execute that command, the function calls the corresponding
 684  * command handler which does argument checking and further processing.
 685  *
 686  * In order to cope with a DOS attacks, a timeout is set up
 687  * which terminates the function if the connection was not
 688  * authenticated when the timeout expires.
 689  *
 690  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 691  */
 692 int handle_connect(int fd, struct sockaddr_in *addr)
 693 {
 694         int ret, argc, use_rc4 = 0;
 695         char buf[4096];
 696         unsigned char crypt_buf[MAXLINE];
 697         struct user *u;
 698         struct server_command *cmd = NULL;
 699         long unsigned challenge_nr, chall_response;
 700         char **argv = NULL;
 701         char *p, *command = NULL;
 702         size_t numbytes;
 703
 704         signal(SIGCHLD, SIG_IGN);
 705         signal(SIGINT, SIG_DFL);
 706         signal(SIGTERM, SIG_DFL);
 707         signal(SIGHUP, SIG_DFL);
 708         signal(SIGUSR1, SIG_IGN);
 709
 710         challenge_nr = random();
 711         /* send Welcome message */
 712         ret = send_va_buffer(fd, "This is para_server, version "
 713                 PACKAGE_VERSION  ".\n" );
 714         if (ret < 0)
 715                 goto err_out;
 716         /* recv auth request line */
 717         ret = recv_buffer(fd, buf, sizeof(buf));
 718         if (ret < 0)
 719                 goto err_out;
 720         if (ret <= 6) {
 721                 ret = -E_AUTH;
 722                 goto err_out;
 723         }
 724         numbytes = ret;
 725         ret = -E_AUTH;
 726         if (strncmp(buf, "auth ", 5))
 727                 goto err_out;
 728
 729         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 730                 p = buf + 5; /* client version < 0.2.6 */
 731         else {
 732                 p = buf + 9; /* client version >= 0.2.6 */
 733                 use_rc4 = 1;
 734         }
 735         PARA_DEBUG_LOG("received %s request for user %s\n",
 736                 use_rc4? "rc4" : "auth", p);
 737         ret = -E_BAD_USER;
 738         u = lookup_user(p);
 739         if (!u)
 740                 goto err_out;
 741         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 742         if (ret <= 0)
 743                 goto err_out;
 744         numbytes = ret;
 745         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 746         /* We can't use send_buffer here since buf may contain null bytes */
 747         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 748         if (ret < 0)
 749                 goto err_out;
 750         /* recv decrypted number */
 751         ret = recv_buffer(fd, buf, sizeof(buf));
 752         if (ret < 0)
 753                 goto err_out;
 754         numbytes = ret;
 755         ret = -E_AUTH;
 756         if (!numbytes)
 757                 goto err_out;
 758         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 759                         || chall_response != challenge_nr)
 760                 goto err_out;
 761         /* auth successful, send 'Proceed' message */
 762         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 763         sprintf(buf, "%s", PROCEED_MSG);
 764         if (use_rc4) {
 765                 init_rc4_keys();
 766                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 767                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 768                 if (ret <= 0)
 769                         goto err_out;
 770                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 771         } else
 772                 numbytes = strlen(buf);
 773         ret = send_bin_buffer(fd, buf, numbytes);
 774         if (ret < 0)
 775                 goto err_out;
 776         if (use_rc4)
 777                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 778         ret = read_command(fd, &command);
 779         if (ret < 0)
 780                 goto err_out;
 781         ret = -E_BAD_CMD;
 782         cmd = parse_cmd(command);
 783         if (!cmd)
 784                 goto err_out;
 785         /* valid command, check permissions */
 786         ret = check_perms(u->perms, cmd);
 787         if (ret < 0)
 788                 goto err_out;
 789         /* valid command and sufficient perms */
 790         alarm(0);
 791         argc = split_args(command, &argv, "\n");
 792         mmd_lock();
 793         mmd->num_commands++;
 794         mmd_unlock();
 795         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 796                 inet_ntoa(addr->sin_addr));
 797         ret = cmd->handler(fd, argc, argv);
 798         if (ret >= 0) {
 799                 ret = EXIT_SUCCESS;
 800                 goto out;
 801         }
 802 err_out:
 803         PARA_NOTICE_LOG("%s\n", PARA_STRERROR(-ret));
 804         if (ret != -E_SEND && ret != -E_RECV)
 805                 send_va_buffer(fd, "%s\n", PARA_STRERROR(-ret));
 806         ret = EXIT_FAILURE;
 807 out:
 808         free(command);
 809         free(argv);
 810         mmd_lock();
 811         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 812                 mmd->events++;
 813         mmd->active_connections--;
 814         mmd_unlock();
 815         return ret;
 816 }