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 "crypt.h"
  18 #include "command.h"
  19 #include "server.cmdline.h"
  20 #include "string.h"
  21 #include "afh.h"
  22 #include "afs.h"
  23 #include "server.h"
  24 #include "vss.h"
  25 #include "list.h"
  26 #include "send.h"
  27 #include "rc4.h"
  28 #include "net.h"
  29 #include "daemon.h"
  30 #include "fd.h"
  31 #include "ipc.h"
  32 #include "user_list.h"
  33 #include "server_command_list.h"
  34 #include "afs_command_list.h"
  35 #include "sched.h"
  36 #include "signal.h"
  37
  38 /** Commands including options must be shorter than this. */
  39 #define MAX_COMMAND_LEN 32768
  40
  41 extern int mmd_mutex;
  42 extern struct misc_meta_data *mmd;
  43 extern struct sender senders[];
  44
  45 static void dummy(__a_unused int s)
  46 {
  47 }
  48
  49 static void mmd_dup(struct misc_meta_data *new_mmd)
  50 {
  51         mutex_lock(mmd_mutex);
  52         *new_mmd = *mmd;
  53         mutex_unlock(mmd_mutex);
  54 }
  55
  56 /*
  57  * Compute human readable string containing vss status for given integer value.
  58  *
  59  * We don't want to use vss_playing() and friends here because we take a
  60  * snapshot of the mmd struct and use the copy for computing the state of the
  61  * vss. If the real data were used, we would take the mmd lock for a rather
  62  * long time or risk to get an inconsistent view.
  63  */
  64 static char *vss_status_tohuman(unsigned int flags)
  65 {
  66         if (flags & VSS_PLAYING)
  67                 return para_strdup("playing");
  68         if (flags & VSS_NEXT)
  69                 return para_strdup("stopped");
  70         return para_strdup("paused");
  71 }
  72
  73 /*
  74  * return human readable permission string. Never returns NULL.
  75  */
  76 static char *cmd_perms_itohuman(unsigned int perms)
  77 {
  78         char *msg = para_malloc(5 * sizeof(char));
  79
  80         msg[0] = perms & AFS_READ? 'a' : '-';
  81         msg[1] = perms & AFS_WRITE? 'A' : '-';
  82         msg[2] = perms & VSS_READ? 'v' : '-';
  83         msg[3] = perms & VSS_WRITE? 'V' : '-';
  84         msg[4] = '\0';
  85         return msg;
  86 }
  87
  88 /*
  89  * Never returns NULL.
  90  */
  91 static char *vss_get_status_flags(unsigned int flags)
  92 {
  93         char *msg = para_malloc(5 * sizeof(char));
  94
  95         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  96         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
  97         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
  98         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
  99         msg[4] = '\0';
 100         return msg;
 101 }
 102
 103 static char *get_status(struct misc_meta_data *nmmd)
 104 {
 105         char *ret, mtime[30] = "";
 106         char *status, *flags; /* vss status info */
 107         char *ut = uptime_str();
 108         long offset = (nmmd->offset + 500) / 1000;
 109         struct timeval current_time;
 110         struct tm mtime_tm;
 111
 112         /* report real status */
 113         status = vss_status_tohuman(nmmd->vss_status_flags);
 114         flags = vss_get_status_flags(nmmd->vss_status_flags);
 115         if (nmmd->size) { /* parent currently has an audio file open */
 116                 localtime_r(&nmmd->mtime, &mtime_tm);
 117                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 118         }
 119         gettimeofday(&current_time, NULL);
 120         ret = make_message(
 121                 "%s: %zu\n" /* file size */
 122                 "%s: %s\n" /* mtime */
 123                 "%s: %s\n" /* status */
 124                 "%s: %s\n" /* status flags */
 125                 "%s: %li\n" /* offset */
 126                 "%s: %s\n" /* afs mode */
 127                 "%s: %lu.%lu\n" /* stream start */
 128                 "%s: %lu.%lu\n" /* current server time */
 129                 "%s", /* afs status info */
 130                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 131                 status_item_list[SI_MTIME], mtime,
 132                 status_item_list[SI_STATUS], status,
 133                 status_item_list[SI_STATUS_FLAGS], flags,
 134
 135                 status_item_list[SI_OFFSET], offset,
 136                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 137
 138                 status_item_list[SI_STREAM_START],
 139                         (long unsigned)nmmd->stream_start.tv_sec,
 140                         (long unsigned)nmmd->stream_start.tv_usec,
 141                 status_item_list[SI_CURRENT_TIME],
 142                         (long unsigned)current_time.tv_sec,
 143                         (long unsigned)current_time.tv_usec,
 144
 145                 nmmd->afd.verbose_ls_output
 146
 147         );
 148         free(flags);
 149         free(status);
 150         free(ut);
 151         return ret;
 152 }
 153
 154 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 155 {
 156         int i;
 157         /* this has to match sender.h */
 158         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 159
 160         scd->sender_num = -1;
 161         if (argc < 2)
 162                 return -E_COMMAND_SYNTAX;
 163         for (i = 0; senders[i].name; i++)
 164                 if (!strcmp(senders[i].name, argv[1]))
 165                         break;
 166         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 167         if (!senders[i].name)
 168                 return -E_COMMAND_SYNTAX;
 169         scd->sender_num = i;
 170         for (i = 0; subcmds[i]; i++)
 171                 if (!strcmp(subcmds[i], argv[2]))
 172                         break;
 173         if (!subcmds[i])
 174                 return -E_COMMAND_SYNTAX;
 175         scd->cmd_num = i;
 176         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 177                 return -E_SENDER_CMD;
 178         switch (scd->cmd_num) {
 179         case SENDER_ON:
 180         case SENDER_OFF:
 181                 if (argc != 3)
 182                         return -E_COMMAND_SYNTAX;
 183                 break;
 184         case SENDER_DENY:
 185         case SENDER_ALLOW:
 186                 if (argc != 4 || parse_cidr(argv[3], scd->host,
 187                                 sizeof(scd->host), &scd->netmask) == NULL)
 188                         return -E_COMMAND_SYNTAX;
 189                 break;
 190         case SENDER_ADD:
 191         case SENDER_DELETE:
 192                 if (argc != 4)
 193                         return -E_COMMAND_SYNTAX;
 194                 return parse_fec_url(argv[3], scd);
 195         default:
 196                 return -E_COMMAND_SYNTAX;
 197         }
 198         return 1;
 199 }
 200
 201 int com_sender(struct rc4_context *rc4c, int argc, char * const * argv)
 202 {
 203         int i, ret;
 204         struct sender_command_data scd;
 205
 206         if (argc < 2) {
 207                 char *msg = NULL;
 208                 for (i = 0; senders[i].name; i++) {
 209                         char *tmp = make_message("%s%s\n",
 210                                 msg? msg : "", senders[i].name);
 211                         free(msg);
 212                         msg = tmp;
 213                 }
 214                 ret = rc4_send_buffer(rc4c, msg);
 215                 free(msg);
 216                 return ret;
 217         }
 218         ret = check_sender_args(argc, argv, &scd);
 219         if (ret < 0) {
 220                 char *msg;
 221                 if (scd.sender_num < 0)
 222                         return ret;
 223                 msg = senders[scd.sender_num].help();
 224                 ret = rc4_send_buffer(rc4c, msg);
 225                 free(msg);
 226                 return ret;
 227         }
 228         for (i = 0; i < 10; i++) {
 229                 mutex_lock(mmd_mutex);
 230                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 231                         mutex_unlock(mmd_mutex);
 232                         usleep(100 * 1000);
 233                         continue;
 234                 }
 235                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 236                 mutex_unlock(mmd_mutex);
 237                 break;
 238         }
 239         return (i < 10)? 1 : -E_LOCK;
 240 }
 241
 242 /* server info */
 243 int com_si(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 244 {
 245         int i, ret;
 246         char *ut;
 247         char *sender_info = NULL, *sender_list = NULL;
 248
 249         if (argc != 1)
 250                 return -E_COMMAND_SYNTAX;
 251         mutex_lock(mmd_mutex);
 252         for (i = 0; senders[i].name; i++) {
 253                 char *info = senders[i].info();
 254                 sender_info = para_strcat(sender_info, info);
 255                 free(info);
 256                 sender_list = para_strcat(sender_list, senders[i].name);
 257                 sender_list = para_strcat(sender_list, " ");
 258         }
 259         ut = uptime_str();
 260         ret = rc4_send_va_buffer(rc4c, "up: %s\nplayed: %u\n"
 261                 "server_pid: %d\n"
 262                 "afs_pid: %d\n"
 263                 "connections (active/accepted/total): %u/%u/%u\n"
 264                 "current loglevel: %s\n"
 265                 "supported audio formats: %s\n"
 266                 "supported senders: %s\n"
 267                 "%s",
 268                 ut, mmd->num_played,
 269                 (int)getppid(),
 270                 (int)mmd->afs_pid,
 271                 mmd->active_connections,
 272                 mmd->num_commands,
 273                 mmd->num_connects,
 274                 conf.loglevel_arg,
 275                 supported_audio_formats(),
 276                 sender_list,
 277                 sender_info
 278         );
 279         mutex_unlock(mmd_mutex);
 280         free(ut);
 281         free(sender_list);
 282         free(sender_info);
 283         return ret;
 284 }
 285
 286 /* version */
 287 int com_version(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 288 {
 289         if (argc != 1)
 290                 return -E_COMMAND_SYNTAX;
 291         return rc4_send_buffer(rc4c, VERSION_TEXT("server")
 292                 "built: " BUILD_DATE "\n"
 293                 UNAME_RS ", " CC_VERSION "\n"
 294         );
 295 }
 296
 297 /* stat */
 298 int com_stat(struct rc4_context *rc4c, int argc, char * const * argv)
 299 {
 300         int ret, num = 0;/* status will be printed that many
 301                           * times. num <= 0 means: print forever
 302                           */
 303         struct misc_meta_data tmp, *nmmd = &tmp;
 304         char *s;
 305
 306         para_sigaction(SIGUSR1, dummy);
 307
 308         if (argc > 1)
 309                 num = atoi(argv[1]);
 310         for (;;) {
 311
 312                 mmd_dup(nmmd);
 313                 s = get_status(nmmd);
 314                 ret = rc4_send_buffer(rc4c, s);
 315                 free(s);
 316                 if (ret < 0)
 317                         goto out;
 318                 ret = 1;
 319                 if (num > 0 && !--num)
 320                         goto out;
 321                 sleep(50);
 322                 if (getppid() == 1)
 323                         return -E_SERVER_CRASH;
 324         }
 325 out:
 326         return ret;
 327 }
 328
 329 static int send_list_of_commands(struct rc4_context *rc4c, struct server_command *cmd,
 330                 const char *handler)
 331 {
 332         int ret, i;
 333
 334         for (i = 1; cmd->name; cmd++, i++) {
 335                 char *perms = cmd_perms_itohuman(cmd->perms);
 336                 ret = rc4_send_va_buffer(rc4c, "%s\t%s\t%s\t%s\n", cmd->name,
 337                         handler,
 338                         perms,
 339                         cmd->description);
 340                 free(perms);
 341                 if (ret < 0)
 342                         return ret;
 343         }
 344         return 1;
 345 }
 346
 347 /* returns string that must be freed by the caller */
 348 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 349 {
 350         struct server_command *cmd;
 351
 352         for (cmd = server_cmds; cmd->name; cmd++)
 353                 if (!strcmp(cmd->name, name)) {
 354                         if (handler)
 355                                 *handler = para_strdup("server"); /* server commands */
 356                         return cmd;
 357                 }
 358         /* not found, look for commands supported by afs */
 359         for (cmd = afs_cmds; cmd->name; cmd++)
 360                 if (!strcmp(cmd->name, name)) {
 361                         if (handler)
 362                                 *handler = para_strdup("afs");
 363                         return cmd;
 364                 }
 365         return NULL;
 366 }
 367
 368 /* help */
 369 int com_help(struct rc4_context *rc4c, int argc, char * const * argv)
 370 {
 371         struct server_command *cmd;
 372         char *perms, *handler;
 373         int ret;
 374
 375         if (argc < 2) {
 376                 /* no argument given, print list of commands */
 377                 if ((ret = send_list_of_commands(rc4c, server_cmds, "server")) < 0)
 378                         return ret;
 379                 return send_list_of_commands(rc4c, afs_cmds, "afs");
 380         }
 381         /* argument given for help */
 382         cmd = get_cmd_ptr(argv[1], &handler);
 383         if (!cmd) {
 384                 free(handler);
 385                 return -E_BAD_CMD;
 386         }
 387         perms = cmd_perms_itohuman(cmd->perms);
 388         ret = rc4_send_va_buffer(rc4c,
 389                 "%s - %s\n\n"
 390                 "handler: %s\n"
 391                 "permissions: %s\n"
 392                 "usage: %s\n\n"
 393                 "%s\n",
 394                 argv[1],
 395                 cmd->description,
 396                 handler,
 397                 perms,
 398                 cmd->usage,
 399                 cmd->help
 400         );
 401         free(perms);
 402         free(handler);
 403         return ret;
 404 }
 405
 406 /* hup */
 407 int com_hup(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 408 {
 409         if (argc != 1)
 410                 return -E_COMMAND_SYNTAX;
 411         kill(getppid(), SIGHUP);
 412         return 1;
 413 }
 414
 415 /* term */
 416 int com_term(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 417 {
 418         if (argc != 1)
 419                 return -E_COMMAND_SYNTAX;
 420         kill(getppid(), SIGTERM);
 421         return 1;
 422 }
 423
 424 int com_play(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 425 {
 426         if (argc != 1)
 427                 return -E_COMMAND_SYNTAX;
 428         mutex_lock(mmd_mutex);
 429         mmd->new_vss_status_flags |= VSS_PLAYING;
 430         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 431         mutex_unlock(mmd_mutex);
 432         return 1;
 433
 434 }
 435
 436 /* stop */
 437 int com_stop(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 438 {
 439         if (argc != 1)
 440                 return -E_COMMAND_SYNTAX;
 441         mutex_lock(mmd_mutex);
 442         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 443         mmd->new_vss_status_flags &= ~VSS_REPOS;
 444         mmd->new_vss_status_flags |= VSS_NEXT;
 445         mutex_unlock(mmd_mutex);
 446         return 1;
 447 }
 448
 449 /* pause */
 450 int com_pause(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 451 {
 452         if (argc != 1)
 453                 return -E_COMMAND_SYNTAX;
 454         mutex_lock(mmd_mutex);
 455         if (!vss_paused() && !vss_stopped()) {
 456                 mmd->events++;
 457                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 458                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 459         }
 460         mutex_unlock(mmd_mutex);
 461         return 1;
 462 }
 463
 464 /* next */
 465 int com_next(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 466 {
 467         if (argc != 1)
 468                 return -E_COMMAND_SYNTAX;
 469         mutex_lock(mmd_mutex);
 470         mmd->events++;
 471         mmd->new_vss_status_flags |= VSS_NEXT;
 472         mutex_unlock(mmd_mutex);
 473         return 1;
 474 }
 475
 476 /* nomore */
 477 int com_nomore(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 478 {
 479         if (argc != 1)
 480                 return -E_COMMAND_SYNTAX;
 481         mutex_lock(mmd_mutex);
 482         if (vss_playing() || vss_paused())
 483                 mmd->new_vss_status_flags |= VSS_NOMORE;
 484         mutex_unlock(mmd_mutex);
 485         return 1;
 486 }
 487
 488 /* ff */
 489 int com_ff(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 490 {
 491         long promille;
 492         int ret, backwards = 0;
 493         unsigned i;
 494         char c;
 495
 496         if (argc != 2)
 497                 return -E_COMMAND_SYNTAX;
 498         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 499                 return -E_COMMAND_SYNTAX;
 500         if (ret > 1 && c == '-')
 501                 backwards = 1; /* jmp backwards */
 502         mutex_lock(mmd_mutex);
 503         ret = -E_NO_AUDIO_FILE;
 504         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 505                 goto out;
 506         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 507         if (backwards)
 508                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 509         else
 510                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 511         if (promille < 0)
 512                 promille = 0;
 513         if (promille >  1000) {
 514                 mmd->new_vss_status_flags |= VSS_NEXT;
 515                 goto out;
 516         }
 517         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 518         mmd->new_vss_status_flags |= VSS_REPOS;
 519         mmd->new_vss_status_flags &= ~VSS_NEXT;
 520         mmd->events++;
 521         ret = 1;
 522 out:
 523         mutex_unlock(mmd_mutex);
 524         return ret;
 525 }
 526
 527 /* jmp */
 528 int com_jmp(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 529 {
 530         long unsigned int i;
 531         int ret;
 532
 533         if (argc != 2)
 534                 return -E_COMMAND_SYNTAX;
 535         if (sscanf(argv[1], "%lu", &i) <= 0)
 536                 return -E_COMMAND_SYNTAX;
 537         mutex_lock(mmd_mutex);
 538         ret = -E_NO_AUDIO_FILE;
 539         if (!mmd->afd.afhi.chunks_total)
 540                 goto out;
 541         if (i > 100)
 542                 i = 100;
 543         PARA_INFO_LOG("jumping to %lu%%\n", i);
 544         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 545         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 546                 mmd->chunks_sent, mmd->offset);
 547         mmd->new_vss_status_flags |= VSS_REPOS;
 548         mmd->new_vss_status_flags &= ~VSS_NEXT;
 549         ret = 1;
 550         mmd->events++;
 551 out:
 552         mutex_unlock(mmd_mutex);
 553         return ret;
 554 }
 555
 556 /*
 557  * check if perms are sufficient to exec a command having perms cmd_perms.
 558  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 559  */
 560 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 561 {
 562         PARA_DEBUG_LOG("checking permissions\n");
 563         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 564 }
 565
 566 /*
 567  * Parse first string from *cmd and lookup in table of valid commands.
 568  * On error, NULL is returned.
 569  */
 570 static struct server_command *parse_cmd(const char *cmdstr)
 571 {
 572         char buf[255];
 573         int n = 0;
 574
 575         sscanf(cmdstr, "%200s%n", buf, &n);
 576         if (!n)
 577                 return NULL;
 578         buf[n] = '\0';
 579         return get_cmd_ptr(buf, NULL);
 580 }
 581
 582 static int read_command(struct rc4_context *rc4c, char **result)
 583 {
 584         int ret;
 585         char buf[4096];
 586         char *command = NULL;
 587
 588         for (;;) {
 589                 size_t numbytes;
 590                 char *p;
 591
 592                 ret = rc4_recv_buffer(rc4c, buf, sizeof(buf));
 593                 if (ret < 0)
 594                         goto out;
 595                 if (!ret)
 596                         break;
 597                 numbytes = ret;
 598                 ret = -E_COMMAND_SYNTAX;
 599                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 600                         goto out;
 601                 command = para_strcat(command, buf);
 602                 p = strstr(command, EOC_MSG);
 603                 if (p) {
 604                         *p = '\0';
 605                         break;
 606                 }
 607         }
 608         ret = command? 1 : -E_COMMAND_SYNTAX;
 609 out:
 610         if (ret < 0)
 611                 free(command);
 612         else
 613                 *result = command;
 614         return ret;
 615
 616 }
 617
 618 static void reset_signals(void)
 619 {
 620         para_sigaction(SIGCHLD, SIG_IGN);
 621         para_sigaction(SIGINT, SIG_DFL);
 622         para_sigaction(SIGTERM, SIG_DFL);
 623         para_sigaction(SIGHUP, SIG_DFL);
 624 }
 625
 626 /**
 627  * Perform user authentication and execute a command.
 628  *
 629  * \param fd The file descriptor to send output to.
 630  * \param peername Identifies the connecting peer.
 631  *
 632  * Whenever para_server accepts an incoming tcp connection on
 633  * the port it listens on, it forks and the resulting child
 634  * calls this function.
 635  *
 636  * An RSA-based challenge/response is used to authenticate
 637  * the peer. It that authentication succeeds, a random RC4
 638  * session key is generated and sent back to the peer,
 639  * encrypted with its RSA public key.  From this point on,
 640  * all transfers are crypted with this session key.
 641  *
 642  * Next it is checked if the peer supplied  a valid server command or a command
 643  * for the audio file selector.  If yes, and if the user has sufficient
 644  * permissions to execute that command, the function calls the corresponding
 645  * command handler which does argument checking and further processing.
 646  *
 647  * In order to cope with a DOS attacks, a timeout is set up
 648  * which terminates the function if the connection was not
 649  * authenticated when the timeout expires.
 650  *
 651  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 652  */
 653 __noreturn void handle_connect(int fd, const char *peername)
 654 {
 655         int ret, argc;
 656         char buf[4096];
 657         unsigned char rand_buf[CHALLENGE_SIZE + 2 * RC4_KEY_LEN];
 658         unsigned char challenge_sha1[HASH_SIZE];
 659         struct user *u;
 660         struct server_command *cmd = NULL;
 661         char **argv = NULL;
 662         char *p, *command = NULL;
 663         size_t numbytes;
 664         struct rc4_context rc4c = {.fd = fd};
 665
 666         reset_signals();
 667         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 668         ret = mark_fd_blocking(fd);
 669         if (ret < 0)
 670                 goto err_out;
 671         /* send Welcome message */
 672         ret = send_va_buffer(fd, "This is para_server, version "
 673                 PACKAGE_VERSION  ".\n" );
 674         if (ret < 0)
 675                 goto err_out;
 676         /* recv auth request line */
 677         ret = recv_buffer(fd, buf, sizeof(buf));
 678         if (ret < 0)
 679                 goto err_out;
 680         if (ret < 10) {
 681                 ret = -E_AUTH_REQUEST;
 682                 goto err_out;
 683         }
 684         numbytes = ret;
 685         ret = -E_AUTH_REQUEST;
 686         if (strncmp(buf, AUTH_REQUEST_MSG, strlen(AUTH_REQUEST_MSG)))
 687                 goto err_out;
 688         p = buf + strlen(AUTH_REQUEST_MSG);
 689         PARA_DEBUG_LOG("received auth request for user %s\n", p);
 690         ret = -E_BAD_USER;
 691         u = lookup_user(p);
 692         if (u) {
 693                 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
 694                 ret = para_encrypt_buffer(u->rsa, rand_buf, sizeof(rand_buf),
 695                         (unsigned char *)buf);
 696                 if (ret < 0)
 697                         goto err_out;
 698                 numbytes = ret;
 699         } else {
 700                 /*
 701                  * We don't want to reveal our user names, so we send a
 702                  * challenge to the client even if the user does not exist, and
 703                  * fail the authentication later.
 704                  */
 705                 numbytes = 256;
 706                 get_random_bytes_or_die((unsigned char *)buf, numbytes);
 707         }
 708         PARA_DEBUG_LOG("sending %zu byte challenge + rc4 keys (%u bytes)\n",
 709                 CHALLENGE_SIZE, numbytes);
 710         ret = send_bin_buffer(fd, buf, numbytes);
 711         if (ret < 0)
 712                 goto net_err;
 713         /* recv challenge response */
 714         ret = recv_bin_buffer(fd, buf, HASH_SIZE);
 715         if (ret < 0)
 716                 goto net_err;
 717         numbytes = ret;
 718         PARA_DEBUG_LOG("received %zu bytes challenge response\n", ret);
 719         ret = -E_BAD_USER;
 720         if (!u)
 721                 goto net_err;
 722         /*
 723          * The correct response is the sha1 of the first CHALLENGE_SIZE bytes
 724          * of the random data.
 725          */
 726         ret = -E_BAD_AUTH;
 727         if (numbytes != HASH_SIZE)
 728                 goto net_err;
 729         sha1_hash((char *)rand_buf, CHALLENGE_SIZE, challenge_sha1);
 730         if (memcmp(challenge_sha1, buf, HASH_SIZE))
 731                 goto net_err;
 732         /* auth successful */
 733         alarm(0);
 734         PARA_INFO_LOG("good auth for %s\n", u->name);
 735         /* init rc4 keys with the second part of the random buffer */
 736         RC4_set_key(&rc4c.recv_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE);
 737         RC4_set_key(&rc4c.send_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE
 738                 + RC4_KEY_LEN);
 739         ret = rc4_send_buffer(&rc4c, PROCEED_MSG);
 740         if (ret < 0)
 741                 goto net_err;
 742         ret = read_command(&rc4c, &command);
 743         if (ret == -E_COMMAND_SYNTAX)
 744                 goto err_out;
 745         if (ret < 0)
 746                 goto net_err;
 747         ret = -E_BAD_CMD;
 748         cmd = parse_cmd(command);
 749         if (!cmd)
 750                 goto err_out;
 751         /* valid command, check permissions */
 752         ret = check_perms(u->perms, cmd);
 753         if (ret < 0)
 754                 goto err_out;
 755         /* valid command and sufficient perms */
 756         argc = split_args(command, &argv, "\n");
 757         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 758                         peername);
 759         ret = cmd->handler(&rc4c, argc, argv);
 760         mutex_lock(mmd_mutex);
 761         mmd->num_commands++;
 762         mutex_unlock(mmd_mutex);
 763         if (ret >= 0)
 764                 goto out;
 765 err_out:
 766         rc4_send_va_buffer(&rc4c, "%s\n", para_strerror(-ret));
 767 net_err:
 768         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 769 out:
 770         free(command);
 771         free(argv);
 772         mutex_lock(mmd_mutex);
 773         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 774                 mmd->events++;
 775         mmd->active_connections--;
 776         mutex_unlock(mmd_mutex);
 777         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 778 }