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