command.c

   1 /*
   2  * Copyright (C) 1997-2009 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 (!is_valid_ipv4_address(argv[3]))
 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                 strncpy(scd->host, argv[3], sizeof(scd->host));
 204                 break;
 205         case SENDER_ADD:
 206         case SENDER_DELETE:
 207                 if (argc != 4)
 208                         return -E_COMMAND_SYNTAX;
 209                 return parse_fec_url(argv[3], scd);
 210         default:
 211                 return -E_COMMAND_SYNTAX;
 212         }
 213         return 1;
 214 }
 215
 216 int com_sender(int fd, int argc, char * const * argv)
 217 {
 218         int i, ret;
 219         struct sender_command_data scd;
 220
 221         if (argc < 2) {
 222                 char *msg = NULL;
 223                 for (i = 0; senders[i].name; i++) {
 224                         char *tmp = make_message("%s%s\n",
 225                                 msg? msg : "", senders[i].name);
 226                         free(msg);
 227                         msg = tmp;
 228                 }
 229                 ret = send_buffer(fd, msg);
 230                 free(msg);
 231                 return ret;
 232         }
 233         ret = check_sender_args(argc, argv, &scd);
 234         if (ret < 0) {
 235                 char *msg;
 236                 if (scd.sender_num < 0)
 237                         return ret;
 238                 msg = senders[scd.sender_num].help();
 239                 ret = send_buffer(fd, msg);
 240                 free(msg);
 241                 return ret;
 242         }
 243         for (i = 0; i < 10; i++) {
 244                 mutex_lock(mmd_mutex);
 245                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 246                         mutex_unlock(mmd_mutex);
 247                         usleep(100 * 1000);
 248                         continue;
 249                 }
 250                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 251                 mutex_unlock(mmd_mutex);
 252                 break;
 253         }
 254         return (i < 10)? 1 : -E_LOCK;
 255 }
 256
 257 /* server info */
 258 int com_si(int fd, int argc, __a_unused char * const * argv)
 259 {
 260         int i, ret;
 261         char *ut;
 262         char *sender_info = NULL, *sender_list = NULL;
 263
 264         if (argc != 1)
 265                 return -E_COMMAND_SYNTAX;
 266         mutex_lock(mmd_mutex);
 267         for (i = 0; senders[i].name; i++) {
 268                 char *info = senders[i].info();
 269                 sender_info = para_strcat(sender_info, info);
 270                 free(info);
 271                 sender_list = para_strcat(sender_list, senders[i].name);
 272                 sender_list = para_strcat(sender_list, " ");
 273         }
 274         ut = uptime_str();
 275         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 276                 "server_pid: %d\n"
 277                 "afs_pid: %d\n"
 278                 "connections (active/accepted/total): %u/%u/%u\n"
 279                 "current loglevel: %s\n"
 280                 "supported audio formats: %s\n"
 281                 "supported senders: %s\n"
 282                 "%s",
 283                 ut, mmd->num_played,
 284                 (int)getppid(),
 285                 (int)mmd->afs_pid,
 286                 mmd->active_connections,
 287                 mmd->num_commands,
 288                 mmd->num_connects,
 289                 conf.loglevel_arg,
 290                 supported_audio_formats(),
 291                 sender_list,
 292                 sender_info
 293         );
 294         mutex_unlock(mmd_mutex);
 295         free(ut);
 296         free(sender_list);
 297         free(sender_info);
 298         return ret;
 299 }
 300
 301 /* version */
 302 int com_version(int fd, int argc, __a_unused char * const * argv)
 303 {
 304         if (argc != 1)
 305                 return -E_COMMAND_SYNTAX;
 306         return send_buffer(fd, VERSION_TEXT("server")
 307                 "built: " BUILD_DATE "\n"
 308                 UNAME_RS ", " CC_VERSION "\n"
 309         );
 310 }
 311
 312 /* stat */
 313 int com_stat(int fd, int argc, char * const * argv)
 314 {
 315         int ret, num = 0;/* status will be printed that many
 316                           * times. num <= 0 means: print forever
 317                           */
 318         struct misc_meta_data tmp, *nmmd = &tmp;
 319         char *s;
 320
 321         signal(SIGUSR1, dummy);
 322
 323         if (argc > 1)
 324                 num = atoi(argv[1]);
 325         for (;;) {
 326
 327                 mmd_dup(nmmd);
 328                 s = get_status(nmmd);
 329                 ret = send_buffer(fd, s);
 330                 free(s);
 331                 if (ret < 0)
 332                         goto out;
 333                 ret = 1;
 334                 if (num > 0 && !--num)
 335                         goto out;
 336                 sleep(50);
 337                 if (getppid() == 1)
 338                         return -E_SERVER_CRASH;
 339         }
 340 out:
 341         return ret;
 342 }
 343
 344 static int send_list_of_commands(int fd, struct server_command *cmd,
 345                 const char *handler)
 346 {
 347         int ret, i;
 348
 349         for (i = 1; cmd->name; cmd++, i++) {
 350                 char *perms = cmd_perms_itohuman(cmd->perms);
 351                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 352                         handler,
 353                         perms,
 354                         cmd->description);
 355                 free(perms);
 356                 if (ret < 0)
 357                         return ret;
 358         }
 359         return 1;
 360 }
 361
 362 /* returns string that must be freed by the caller */
 363 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 364 {
 365         struct server_command *cmd;
 366
 367         for (cmd = server_cmds; cmd->name; cmd++)
 368                 if (!strcmp(cmd->name, name)) {
 369                         if (handler)
 370                                 *handler = para_strdup("server"); /* server commands */
 371                         return cmd;
 372                 }
 373         /* not found, look for commands supported by afs */
 374         for (cmd = afs_cmds; cmd->name; cmd++)
 375                 if (!strcmp(cmd->name, name)) {
 376                         if (handler)
 377                                 *handler = para_strdup("afs");
 378                         return cmd;
 379                 }
 380         return NULL;
 381 }
 382
 383 /* help */
 384 int com_help(int fd, int argc, char * const * argv)
 385 {
 386         struct server_command *cmd;
 387         char *perms, *handler;
 388         int ret;
 389
 390         if (argc < 2) {
 391                 /* no argument given, print list of commands */
 392                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 393                         return ret;
 394                 return send_list_of_commands(fd, afs_cmds, "afs");
 395         }
 396         /* argument given for help */
 397         cmd = get_cmd_ptr(argv[1], &handler);
 398         if (!cmd) {
 399                 free(handler);
 400                 return -E_BAD_CMD;
 401         }
 402         perms = cmd_perms_itohuman(cmd->perms);
 403         ret = send_va_buffer(fd,
 404                 "%s - %s\n\n"
 405                 "handler: %s\n"
 406                 "permissions: %s\n"
 407                 "usage: %s\n\n"
 408                 "%s\n",
 409                 argv[1],
 410                 cmd->description,
 411                 handler,
 412                 perms,
 413                 cmd->usage,
 414                 cmd->help
 415         );
 416         free(perms);
 417         free(handler);
 418         return ret;
 419 }
 420
 421 /* hup */
 422 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 423 {
 424         if (argc != 1)
 425                 return -E_COMMAND_SYNTAX;
 426         kill(getppid(), SIGHUP);
 427         return 1;
 428 }
 429
 430 /* term */
 431 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 432 {
 433         if (argc != 1)
 434                 return -E_COMMAND_SYNTAX;
 435         kill(getppid(), SIGTERM);
 436         return 1;
 437 }
 438
 439 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 440 {
 441         if (argc != 1)
 442                 return -E_COMMAND_SYNTAX;
 443         mutex_lock(mmd_mutex);
 444         mmd->new_vss_status_flags |= VSS_PLAYING;
 445         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 446         mutex_unlock(mmd_mutex);
 447         return 1;
 448
 449 }
 450
 451 /* stop */
 452 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 453 {
 454         if (argc != 1)
 455                 return -E_COMMAND_SYNTAX;
 456         mutex_lock(mmd_mutex);
 457         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 458         mmd->new_vss_status_flags &= ~VSS_REPOS;
 459         mmd->new_vss_status_flags |= VSS_NEXT;
 460         mutex_unlock(mmd_mutex);
 461         return 1;
 462 }
 463
 464 /* pause */
 465 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 466 {
 467         if (argc != 1)
 468                 return -E_COMMAND_SYNTAX;
 469         mutex_lock(mmd_mutex);
 470         if (!vss_paused() && !vss_stopped()) {
 471                 mmd->events++;
 472                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 473                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 474         }
 475         mutex_unlock(mmd_mutex);
 476         return 1;
 477 }
 478
 479 /* next */
 480 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 481 {
 482         if (argc != 1)
 483                 return -E_COMMAND_SYNTAX;
 484         mutex_lock(mmd_mutex);
 485         mmd->events++;
 486         mmd->new_vss_status_flags |= VSS_NEXT;
 487         mutex_unlock(mmd_mutex);
 488         return 1;
 489 }
 490
 491 /* nomore */
 492 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 493 {
 494         if (argc != 1)
 495                 return -E_COMMAND_SYNTAX;
 496         mutex_lock(mmd_mutex);
 497         if (vss_playing() || vss_paused())
 498                 mmd->new_vss_status_flags |= VSS_NOMORE;
 499         mutex_unlock(mmd_mutex);
 500         return 1;
 501 }
 502
 503 /* ff */
 504 int com_ff(__a_unused int fd, int argc, char * const * argv)
 505 {
 506         long promille;
 507         int ret, backwards = 0;
 508         unsigned i;
 509         char c;
 510
 511         if (argc != 2)
 512                 return -E_COMMAND_SYNTAX;
 513         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 514                 return -E_COMMAND_SYNTAX;
 515         if (ret > 1 && c == '-')
 516                 backwards = 1; /* jmp backwards */
 517         mutex_lock(mmd_mutex);
 518         ret = -E_NO_AUDIO_FILE;
 519         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 520                 goto out;
 521         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 522         if (backwards)
 523                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 524         else
 525                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 526         if (promille < 0)
 527                 promille = 0;
 528         if (promille >  1000) {
 529                 mmd->new_vss_status_flags |= VSS_NEXT;
 530                 goto out;
 531         }
 532         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 533         mmd->new_vss_status_flags |= VSS_REPOS;
 534         mmd->new_vss_status_flags &= ~VSS_NEXT;
 535         mmd->events++;
 536         ret = 1;
 537 out:
 538         mutex_unlock(mmd_mutex);
 539         return ret;
 540 }
 541
 542 /* jmp */
 543 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 544 {
 545         long unsigned int i;
 546         int ret;
 547
 548         if (argc != 2)
 549                 return -E_COMMAND_SYNTAX;
 550         if (sscanf(argv[1], "%lu", &i) <= 0)
 551                 return -E_COMMAND_SYNTAX;
 552         mutex_lock(mmd_mutex);
 553         ret = -E_NO_AUDIO_FILE;
 554         if (!mmd->afd.afhi.chunks_total)
 555                 goto out;
 556         if (i > 100)
 557                 i = 100;
 558         PARA_INFO_LOG("jumping to %lu%%\n", i);
 559         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 560         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 561                 mmd->chunks_sent, mmd->offset);
 562         mmd->new_vss_status_flags |= VSS_REPOS;
 563         mmd->new_vss_status_flags &= ~VSS_NEXT;
 564         ret = 1;
 565         mmd->events++;
 566 out:
 567         mutex_unlock(mmd_mutex);
 568         return ret;
 569 }
 570
 571 /*
 572  * check if perms are sufficient to exec a command having perms cmd_perms.
 573  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 574  */
 575 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 576 {
 577         PARA_DEBUG_LOG("checking permissions\n");
 578         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 579 }
 580
 581 /*
 582  * Parse first string from *cmd and lookup in table of valid commands.
 583  * On error, NULL is returned.
 584  */
 585 static struct server_command *parse_cmd(const char *cmdstr)
 586 {
 587         char buf[255];
 588         int n = 0;
 589
 590         sscanf(cmdstr, "%200s%n", buf, &n);
 591         if (!n)
 592                 return NULL;
 593         buf[n] = '\0';
 594         return get_cmd_ptr(buf, NULL);
 595 }
 596
 597 static void init_rc4_keys(void)
 598 {
 599         int i;
 600
 601         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 602                 rc4_buf[i] = para_random(256);
 603         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 604                 (unsigned char) rc4_buf[0],
 605                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 606         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 607         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 608 }
 609
 610 static void rc4_recv(unsigned long len, const unsigned char *indata,
 611                 unsigned char *outdata, __a_unused void *private_data)
 612 {
 613         RC4(&rc4_recv_key, len, indata, outdata);
 614 }
 615
 616 static void rc4_send(unsigned long len, const unsigned char *indata,
 617                 unsigned char *outdata, __a_unused void *private_data)
 618 {
 619         RC4(&rc4_send_key, len, indata, outdata);
 620 }
 621
 622 static int read_command(int fd, char **result)
 623 {
 624         int ret;
 625         char buf[4096];
 626         char *command = NULL;
 627
 628         for (;;) {
 629                 size_t numbytes;
 630                 char *p;
 631
 632                 ret = recv_buffer(fd, buf, sizeof(buf));
 633                 if (ret < 0)
 634                         goto out;
 635                 if (!ret)
 636                         break;
 637                 numbytes = ret;
 638                 ret = -E_COMMAND_SYNTAX;
 639                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 640                         goto out;
 641                 command = para_strcat(command, buf);
 642                 p = strstr(command, EOC_MSG);
 643                 if (p) {
 644                         *p = '\0';
 645                         break;
 646                 }
 647         }
 648         ret = command? 1 : -E_COMMAND_SYNTAX;
 649 out:
 650         if (ret < 0)
 651                 free(command);
 652         else
 653                 *result = command;
 654         return ret;
 655
 656 }
 657
 658 /**
 659  * Perform user authentication and execute a command.
 660  *
 661  * \param fd The file descriptor to send output to.
 662  * \param peername Identifies the connecting peer.
 663  *
 664  * Whenever para_server accepts an incoming tcp connection on
 665  * the port it listens on, it forks and the resulting child
 666  * calls this function.
 667  *
 668  * An RSA-based challenge/response is used to authenticate
 669  * the peer. It that authentication succeeds, a random RC4
 670  * session key is generated and sent back to the peer,
 671  * encrypted with its RSA public key.  From this point on,
 672  * all transfers are crypted with this session key.
 673  *
 674  * Next it is checked if the peer supplied  a valid server command or a command
 675  * for the audio file selector.  If yes, and if the user has sufficient
 676  * permissions to execute that command, the function calls the corresponding
 677  * command handler which does argument checking and further processing.
 678  *
 679  * In order to cope with a DOS attacks, a timeout is set up
 680  * which terminates the function if the connection was not
 681  * authenticated when the timeout expires.
 682  *
 683  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 684  */
 685 __noreturn void handle_connect(int fd, const char *peername)
 686 {
 687         int ret, argc, use_rc4 = 0;
 688         char buf[4096];
 689         unsigned char crypt_buf[MAXLINE];
 690         struct user *u;
 691         struct server_command *cmd = NULL;
 692         long unsigned challenge_nr, chall_response;
 693         char **argv = NULL;
 694         char *p, *command = NULL;
 695         size_t numbytes;
 696
 697         signal(SIGCHLD, SIG_IGN);
 698         signal(SIGINT, SIG_DFL);
 699         signal(SIGTERM, SIG_DFL);
 700         signal(SIGHUP, SIG_DFL);
 701
 702         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 703         ret = mark_fd_blocking(fd);
 704         if (ret < 0)
 705                 goto err_out;
 706         challenge_nr = random();
 707         /* send Welcome message */
 708         ret = send_va_buffer(fd, "This is para_server, version "
 709                 PACKAGE_VERSION  ".\n" );
 710         if (ret < 0)
 711                 goto err_out;
 712         /* recv auth request line */
 713         ret = recv_buffer(fd, buf, sizeof(buf));
 714         if (ret < 0)
 715                 goto err_out;
 716         if (ret <= 6) {
 717                 ret = -E_AUTH;
 718                 goto err_out;
 719         }
 720         numbytes = ret;
 721         ret = -E_AUTH;
 722         if (strncmp(buf, "auth ", 5))
 723                 goto err_out;
 724
 725         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 726                 p = buf + 5; /* client version < 0.2.6 */
 727         else {
 728                 p = buf + 9; /* client version >= 0.2.6 */
 729                 use_rc4 = 1;
 730         }
 731         PARA_DEBUG_LOG("received %s request for user %s\n",
 732                 use_rc4? "rc4" : "auth", p);
 733         ret = -E_BAD_USER;
 734         u = lookup_user(p);
 735         if (!u)
 736                 goto err_out;
 737         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 738         if (ret <= 0)
 739                 goto err_out;
 740         numbytes = ret;
 741         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 742         /* We can't use send_buffer here since buf may contain null bytes */
 743         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 744         if (ret < 0)
 745                 goto net_err;
 746         /* recv decrypted number */
 747         ret = recv_buffer(fd, buf, sizeof(buf));
 748         if (ret < 0)
 749                 goto net_err;
 750         numbytes = ret;
 751         ret = -E_AUTH;
 752         if (!numbytes)
 753                 goto net_err;
 754         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 755                         || chall_response != challenge_nr)
 756                 goto err_out;
 757         /* auth successful, send 'Proceed' message */
 758         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 759         sprintf(buf, "%s", PROCEED_MSG);
 760         if (use_rc4) {
 761                 init_rc4_keys();
 762                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 763                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 764                 if (ret <= 0)
 765                         goto err_out;
 766                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 767         } else
 768                 numbytes = strlen(buf);
 769         ret = send_bin_buffer(fd, buf, numbytes);
 770         if (ret < 0)
 771                 goto net_err;
 772         if (use_rc4)
 773                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 774         ret = read_command(fd, &command);
 775         if (ret == -E_COMMAND_SYNTAX)
 776                 goto err_out;
 777         if (ret < 0)
 778                 goto net_err;
 779         ret = -E_BAD_CMD;
 780         cmd = parse_cmd(command);
 781         if (!cmd)
 782                 goto err_out;
 783         /* valid command, check permissions */
 784         ret = check_perms(u->perms, cmd);
 785         if (ret < 0)
 786                 goto err_out;
 787         /* valid command and sufficient perms */
 788         alarm(0);
 789         argc = split_args(command, &argv, "\n");
 790         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 791                         peername);
 792         ret = cmd->handler(fd, argc, argv);
 793         mutex_lock(mmd_mutex);
 794         mmd->num_commands++;
 795         free(mmd->afd.afhi.info_string);
 796         free(mmd->afd.afhi.chunk_table);
 797         mutex_unlock(mmd_mutex);
 798         if (ret >= 0)
 799                 goto out;
 800 err_out:
 801         send_va_buffer(fd, "%s\n", para_strerror(-ret));
 802 net_err:
 803         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 804 out:
 805         free(command);
 806         free(argv);
 807         mutex_lock(mmd_mutex);
 808         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 809                 mmd->events++;
 810         mmd->active_connections--;
 811         mutex_unlock(mmd_mutex);
 812         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 813 }