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