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"
 119                 "%s:%s\n"       "%s:%s\n"       "%s:%s\n"
 120                 "%s:%li\n"      "%s:%s\n"
 121                 "%s:%s\n"       "%s:%lu.%lu\n"  "%s:%lu.%lu\n"
 122                 "%s:%s\n"       "%s\n",
 123                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 124                 status_item_list[SI_MTIME], mtime,
 125
 126                 status_item_list[SI_BASENAME], basename ? basename : "(none)",
 127                 status_item_list[SI_STATUS], status,
 128                 status_item_list[SI_STATUS_FLAGS], flags,
 129
 130                 status_item_list[SI_OFFSET], offset,
 131                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 132
 133                 status_item_list[SI_UPTIME], ut,
 134                 status_item_list[SI_STREAM_START],
 135                         (long unsigned)nmmd->stream_start.tv_sec,
 136                         (long unsigned)nmmd->stream_start.tv_usec,
 137                 status_item_list[SI_CURRENT_TIME],
 138                         (long unsigned)now.tv_sec,
 139                         (long unsigned)now.tv_usec,
 140
 141                 status_item_list[SI_DIRECTORY], dirname? dirname : "(none)",
 142                 nmmd->afd.afs_status_info
 143
 144         );
 145         free(basename);
 146         free(dirname);
 147         free(flags);
 148         free(status);
 149         free(ut);
 150         return ret;
 151 }
 152
 153 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 154 {
 155         int i;
 156         /* this has to match sender.h */
 157         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 158
 159         scd->sender_num = -1;
 160         if (argc < 2)
 161                 return -E_COMMAND_SYNTAX;
 162         for (i = 0; senders[i].name; i++)
 163                 if (!strcmp(senders[i].name, argv[1]))
 164                         break;
 165         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 166         if (!senders[i].name)
 167                 return -E_COMMAND_SYNTAX;
 168         scd->sender_num = i;
 169         for (i = 0; subcmds[i]; i++)
 170                 if (!strcmp(subcmds[i], argv[2]))
 171                         break;
 172         if (!subcmds[i])
 173                 return -E_COMMAND_SYNTAX;
 174         scd->cmd_num = i;
 175         mmd_lock();
 176         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 177                 mmd_unlock();
 178                 return -E_SENDER_CMD;
 179         }
 180         mmd_unlock();
 181         switch (scd->cmd_num) {
 182         case SENDER_ON:
 183         case SENDER_OFF:
 184                 if (argc != 3)
 185                         return -E_COMMAND_SYNTAX;
 186                 break;
 187         case SENDER_DENY:
 188         case SENDER_ALLOW:
 189                 if (argc != 4 && argc != 5)
 190                         return -E_COMMAND_SYNTAX;
 191                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 192                         return -E_COMMAND_SYNTAX;
 193                 scd->netmask = 32;
 194                 if (argc == 5) {
 195                         scd->netmask = atoi(argv[4]);
 196                         if (scd->netmask < 0 || scd->netmask > 32)
 197                                 return -E_COMMAND_SYNTAX;
 198                 }
 199                 break;
 200         case SENDER_ADD:
 201         case SENDER_DELETE:
 202                 if (argc != 4 && argc != 5)
 203                         return -E_COMMAND_SYNTAX;
 204                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 205                         return -E_COMMAND_SYNTAX;
 206                 scd->port = -1;
 207                 if (argc == 5) {
 208                         scd->port = atoi(argv[4]);
 209                         if (scd->port < 0 || scd->port > 65535)
 210                                 return -E_COMMAND_SYNTAX;
 211                 }
 212                 break;
 213         default:
 214                 return -E_COMMAND_SYNTAX;
 215         }
 216         return 1;
 217 }
 218
 219 int com_sender(int fd, int argc, char * const * argv)
 220 {
 221         int i, ret;
 222         struct sender_command_data scd;
 223
 224         if (argc < 2) {
 225                 char *msg = NULL;
 226                 for (i = 0; senders[i].name; i++) {
 227                         char *tmp = make_message("%s%s\n",
 228                                 msg? msg : "", senders[i].name);
 229                         free(msg);
 230                         msg = tmp;
 231                 }
 232                 ret = send_buffer(fd, msg);
 233                 free(msg);
 234                 return ret;
 235         }
 236         ret = check_sender_args(argc, argv, &scd);
 237         if (ret < 0) {
 238                 char *msg;
 239                 if (scd.sender_num < 0)
 240                         return ret;
 241                 msg = senders[scd.sender_num].help();
 242                 send_buffer(fd, msg);
 243                 free(msg);
 244                 return 1;
 245         }
 246         for (i = 0; i < 10; i++) {
 247                 mmd_lock();
 248                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 249                         mmd_unlock();
 250                         usleep(100 * 1000);
 251                         continue;
 252                 }
 253                 mmd->sender_cmd_data = scd;
 254                 mmd_unlock();
 255                 break;
 256         }
 257         return (i < 10)? 1 : -E_LOCK;
 258 }
 259
 260 /* server info */
 261 int com_si(int fd, int argc, __a_unused char * const * argv)
 262 {
 263         int i, ret;
 264         char *ut;
 265         char *sender_info = NULL, *sender_list = NULL;
 266
 267         if (argc != 1)
 268                 return -E_COMMAND_SYNTAX;
 269         mmd_lock();
 270         for (i = 0; senders[i].name; i++) {
 271                 char *info = senders[i].info();
 272                 sender_info = para_strcat(sender_info, info);
 273                 free(info);
 274                 sender_list = para_strcat(sender_list, senders[i].name);
 275                 sender_list = para_strcat(sender_list, " ");
 276         }
 277         ut = uptime_str();
 278         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 279                 "pid: %d\n"
 280                 "connections (active/accepted/total): %u/%u/%u\n"
 281                 "current loglevel: %i\n"
 282                 "supported audio formats: %s\n"
 283                 "supported senders: %s\n"
 284                 "%s",
 285                 ut, mmd->num_played,
 286                 getppid(),
 287                 mmd->active_connections,
 288                 mmd->num_commands,
 289                 mmd->num_connects,
 290                 conf.loglevel_arg,
 291                 supported_audio_formats(),
 292                 sender_list,
 293                 sender_info
 294         );
 295         mmd_unlock();
 296         free(ut);
 297         free(sender_list);
 298         free(sender_info);
 299         return ret;
 300 }
 301
 302 /* version */
 303 int com_version(int fd, int argc, __a_unused char * const * argv)
 304 {
 305         if (argc != 1)
 306                 return -E_COMMAND_SYNTAX;
 307         return send_buffer(fd, VERSION_TEXT("server")
 308                 "built: " BUILD_DATE "\n"
 309                 SYSTEM ", " CC_VERSION "\n"
 310         );
 311 }
 312
 313 /* stat */
 314 int com_stat(int fd, int argc, char * const * argv)
 315 {
 316         int ret, num = 0;/* status will be printed that many
 317                           * times. num <= 0 means: print forever
 318                           */
 319         struct misc_meta_data tmp, *nmmd = &tmp;
 320         char *s;
 321
 322         signal(SIGUSR1, dummy);
 323
 324         if (argc > 1)
 325                 num = atoi(argv[1]);
 326         for (;;) {
 327
 328                 mmd_dup(nmmd);
 329                 s = get_status(nmmd);
 330                 ret = send_buffer(fd, s);
 331                 free(s);
 332                 if (ret < 0)
 333                         goto out;
 334                 ret = 1;
 335                 if (num == 1)
 336                         goto out;
 337                 sleep(50);
 338                 if (getppid() == 1)
 339                         return -E_SERVER_CRASH;
 340         }
 341 out:
 342         return ret;
 343 }
 344
 345 static int send_list_of_commands(int fd, struct server_command *cmd,
 346                 const char *handler)
 347 {
 348         int ret, i;
 349
 350         for (i = 1; cmd->name; cmd++, i++) {
 351                 char *perms = cmd_perms_itohuman(cmd->perms);
 352                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 353                         handler,
 354                         perms,
 355                         cmd->description);
 356                 free(perms);
 357                 if (ret < 0)
 358                         return ret;
 359         }
 360         return 1;
 361 }
 362
 363 /* returns string that must be freed by the caller */
 364 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 365 {
 366         struct server_command *cmd;
 367
 368         for (cmd = server_cmds; cmd->name; cmd++)
 369                 if (!strcmp(cmd->name, name)) {
 370                         if (handler)
 371                                 *handler = para_strdup("server"); /* server commands */
 372                         return cmd;
 373                 }
 374         /* not found, look for commands supported by afs */
 375         for (cmd = afs_cmds; cmd->name; cmd++)
 376                 if (!strcmp(cmd->name, name)) {
 377                         if (handler)
 378                                 *handler = para_strdup("afs");
 379                         return cmd;
 380                 }
 381         return NULL;
 382 }
 383
 384 /* help */
 385 int com_help(int fd, int argc, char * const * argv)
 386 {
 387         struct server_command *cmd;
 388         char *perms, *handler;
 389         int ret;
 390
 391         if (argc < 2) {
 392                 /* no argument given, print list of commands */
 393                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 394                         return ret;
 395                 return send_list_of_commands(fd, afs_cmds, "afs");
 396         }
 397         /* argument given for help */
 398         cmd = get_cmd_ptr(argv[1], &handler);
 399         if (!cmd) {
 400                 free(handler);
 401                 return -E_BAD_CMD;
 402         }
 403         perms = cmd_perms_itohuman(cmd->perms);
 404         ret = send_va_buffer(fd,
 405                 "%s - %s\n\n"
 406                 "handler: %s\n"
 407                 "permissions: %s\n"
 408                 "usage: %s\n\n"
 409                 "%s\n",
 410                 argv[1],
 411                 cmd->description,
 412                 handler,
 413                 perms,
 414                 cmd->usage,
 415                 cmd->help
 416         );
 417         free(perms);
 418         free(handler);
 419         return ret;
 420 }
 421
 422 /* hup */
 423 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 424 {
 425         if (argc != 1)
 426                 return -E_COMMAND_SYNTAX;
 427         kill(getppid(), SIGHUP);
 428         return 1;
 429 }
 430
 431 /* term */
 432 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 433 {
 434         if (argc != 1)
 435                 return -E_COMMAND_SYNTAX;
 436         kill(getppid(), SIGTERM);
 437         return 1;
 438 }
 439
 440 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 441 {
 442         if (argc != 1)
 443                 return -E_COMMAND_SYNTAX;
 444         mmd_lock();
 445         mmd->new_vss_status_flags |= VSS_PLAYING;
 446         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 447         mmd_unlock();
 448         return 1;
 449
 450 }
 451
 452 /* stop */
 453 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 454 {
 455         if (argc != 1)
 456                 return -E_COMMAND_SYNTAX;
 457         mmd_lock();
 458         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 459         mmd->new_vss_status_flags &= ~VSS_REPOS;
 460         mmd->new_vss_status_flags |= VSS_NEXT;
 461         mmd_unlock();
 462         return 1;
 463 }
 464
 465 /* pause */
 466 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 467 {
 468         if (argc != 1)
 469                 return -E_COMMAND_SYNTAX;
 470         mmd_lock();
 471         if (!vss_paused())
 472                 mmd->events++;
 473         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 474         mmd->new_vss_status_flags &= ~VSS_NEXT;
 475         mmd_unlock();
 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         mmd_lock();
 485         mmd->events++;
 486         mmd->new_vss_status_flags |= VSS_NEXT;
 487         mmd_unlock();
 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         mmd_lock();
 497         if (vss_playing() || vss_paused())
 498                 mmd->new_vss_status_flags |= VSS_NOMORE;
 499         mmd_unlock();
 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         mmd_lock();
 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         mmd_unlock();
 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         mmd_lock();
 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         mmd_unlock();
 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("%s", "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 addr socket address info of peer
 663  *
 664  * \return EXIT_SUCCESS or EXIT_FAILURE
 665  *
 666  * Whenever para_server accepts an incoming tcp connection on
 667  * the port it listens on, it forks and the resulting child
 668  * calls this function.
 669  *
 670  * An RSA-based challenge/response is used to authenticate
 671  * the peer. It that authentication succeeds, a random RC4
 672  * session key is generated and sent back to the peer,
 673  * encrypted with its RSA public key.  From this point on,
 674  * all transfers are crypted with this session key.
 675  *
 676  * Next it is checked if the peer supplied  a valid server command or a command
 677  * for the audio file selector.  If yes, and if the user has sufficient
 678  * permissions to execute that command, the function calls the corresponding
 679  * command handler which does argument checking and further processing.
 680  *
 681  * In order to cope with a DOS attacks, a timeout is set up
 682  * which terminates the function if the connection was not
 683  * authenticated when the timeout expires.
 684  *
 685  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 686  */
 687 int handle_connect(int fd, struct sockaddr_in *addr)
 688 {
 689         int ret, argc, use_rc4 = 0;
 690         char buf[4096];
 691         unsigned char crypt_buf[MAXLINE];
 692         struct user *u;
 693         struct server_command *cmd = NULL;
 694         long unsigned challenge_nr, chall_response;
 695         char **argv = NULL;
 696         char *p, *command = NULL;
 697         size_t numbytes;
 698
 699         signal(SIGCHLD, SIG_IGN);
 700         signal(SIGINT, SIG_DFL);
 701         signal(SIGTERM, SIG_DFL);
 702         signal(SIGHUP, SIG_DFL);
 703         signal(SIGUSR1, SIG_IGN);
 704
 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 err_out;
 745         /* recv decrypted number */
 746         ret = recv_buffer(fd, buf, sizeof(buf));
 747         if (ret < 0)
 748                 goto err_out;
 749         numbytes = ret;
 750         ret = -E_AUTH;
 751         if (!numbytes)
 752                 goto err_out;
 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 err_out;
 771         if (use_rc4)
 772                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 773         ret = read_command(fd, &command);
 774         if (ret < 0)
 775                 goto err_out;
 776         ret = -E_BAD_CMD;
 777         cmd = parse_cmd(command);
 778         if (!cmd)
 779                 goto err_out;
 780         /* valid command, check permissions */
 781         ret = check_perms(u->perms, cmd);
 782         if (ret < 0)
 783                 goto err_out;
 784         /* valid command and sufficient perms */
 785         alarm(0);
 786         argc = split_args(command, &argv, "\n");
 787         mmd_lock();
 788         mmd->num_commands++;
 789         mmd_unlock();
 790         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 791                 inet_ntoa(addr->sin_addr));
 792         ret = cmd->handler(fd, argc, argv);
 793         if (ret >= 0) {
 794                 ret = EXIT_SUCCESS;
 795                 goto out;
 796         }
 797 err_out:
 798         PARA_NOTICE_LOG("%s\n", PARA_STRERROR(-ret));
 799         if (ret != -E_SEND && ret != -E_RECV)
 800                 send_va_buffer(fd, "%s\n", PARA_STRERROR(-ret));
 801         ret = EXIT_FAILURE;
 802 out:
 803         free(command);
 804         free(argv);
 805         mmd_lock();
 806         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 807                 mmd->events++;
 808         mmd->active_connections--;
 809         mmd_unlock();
 810         return ret;
 811 }