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 && argc != 5)
 187                         return -E_COMMAND_SYNTAX;
 188                 if (!is_valid_ipv4_address(argv[3]))
 189                         return -E_COMMAND_SYNTAX;
 190                 scd->netmask = 32;
 191                 if (argc == 5) {
 192                         scd->netmask = atoi(argv[4]);
 193                         if (scd->netmask < 0 || scd->netmask > 32)
 194                                 return -E_COMMAND_SYNTAX;
 195                 }
 196                 strncpy(scd->host, argv[3], sizeof(scd->host));
 197                 break;
 198         case SENDER_ADD:
 199         case SENDER_DELETE:
 200                 if (argc != 4)
 201                         return -E_COMMAND_SYNTAX;
 202                 return parse_fec_url(argv[3], scd);
 203         default:
 204                 return -E_COMMAND_SYNTAX;
 205         }
 206         return 1;
 207 }
 208
 209 int com_sender(struct rc4_context *rc4c, int argc, char * const * argv)
 210 {
 211         int i, ret;
 212         struct sender_command_data scd;
 213
 214         if (argc < 2) {
 215                 char *msg = NULL;
 216                 for (i = 0; senders[i].name; i++) {
 217                         char *tmp = make_message("%s%s\n",
 218                                 msg? msg : "", senders[i].name);
 219                         free(msg);
 220                         msg = tmp;
 221                 }
 222                 ret = rc4_send_buffer(rc4c, msg);
 223                 free(msg);
 224                 return ret;
 225         }
 226         ret = check_sender_args(argc, argv, &scd);
 227         if (ret < 0) {
 228                 char *msg;
 229                 if (scd.sender_num < 0)
 230                         return ret;
 231                 msg = senders[scd.sender_num].help();
 232                 ret = rc4_send_buffer(rc4c, msg);
 233                 free(msg);
 234                 return ret;
 235         }
 236         for (i = 0; i < 10; i++) {
 237                 mutex_lock(mmd_mutex);
 238                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 239                         mutex_unlock(mmd_mutex);
 240                         usleep(100 * 1000);
 241                         continue;
 242                 }
 243                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 244                 mutex_unlock(mmd_mutex);
 245                 break;
 246         }
 247         return (i < 10)? 1 : -E_LOCK;
 248 }
 249
 250 /* server info */
 251 int com_si(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 252 {
 253         int i, ret;
 254         char *ut;
 255         char *sender_info = NULL, *sender_list = NULL;
 256
 257         if (argc != 1)
 258                 return -E_COMMAND_SYNTAX;
 259         mutex_lock(mmd_mutex);
 260         for (i = 0; senders[i].name; i++) {
 261                 char *info = senders[i].info();
 262                 sender_info = para_strcat(sender_info, info);
 263                 free(info);
 264                 sender_list = para_strcat(sender_list, senders[i].name);
 265                 sender_list = para_strcat(sender_list, " ");
 266         }
 267         ut = uptime_str();
 268         ret = rc4_send_va_buffer(rc4c, "up: %s\nplayed: %u\n"
 269                 "server_pid: %d\n"
 270                 "afs_pid: %d\n"
 271                 "connections (active/accepted/total): %u/%u/%u\n"
 272                 "current loglevel: %s\n"
 273                 "supported audio formats: %s\n"
 274                 "supported senders: %s\n"
 275                 "%s",
 276                 ut, mmd->num_played,
 277                 (int)getppid(),
 278                 (int)mmd->afs_pid,
 279                 mmd->active_connections,
 280                 mmd->num_commands,
 281                 mmd->num_connects,
 282                 conf.loglevel_arg,
 283                 supported_audio_formats(),
 284                 sender_list,
 285                 sender_info
 286         );
 287         mutex_unlock(mmd_mutex);
 288         free(ut);
 289         free(sender_list);
 290         free(sender_info);
 291         return ret;
 292 }
 293
 294 /* version */
 295 int com_version(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 296 {
 297         if (argc != 1)
 298                 return -E_COMMAND_SYNTAX;
 299         return rc4_send_buffer(rc4c, VERSION_TEXT("server")
 300                 "built: " BUILD_DATE "\n"
 301                 UNAME_RS ", " CC_VERSION "\n"
 302         );
 303 }
 304
 305 /* stat */
 306 int com_stat(struct rc4_context *rc4c, int argc, char * const * argv)
 307 {
 308         int ret, num = 0;/* status will be printed that many
 309                           * times. num <= 0 means: print forever
 310                           */
 311         struct misc_meta_data tmp, *nmmd = &tmp;
 312         char *s;
 313
 314         para_sigaction(SIGUSR1, dummy);
 315
 316         if (argc > 1)
 317                 num = atoi(argv[1]);
 318         for (;;) {
 319
 320                 mmd_dup(nmmd);
 321                 s = get_status(nmmd);
 322                 ret = rc4_send_buffer(rc4c, s);
 323                 free(s);
 324                 if (ret < 0)
 325                         goto out;
 326                 ret = 1;
 327                 if (num > 0 && !--num)
 328                         goto out;
 329                 sleep(50);
 330                 if (getppid() == 1)
 331                         return -E_SERVER_CRASH;
 332         }
 333 out:
 334         return ret;
 335 }
 336
 337 static int send_list_of_commands(struct rc4_context *rc4c, struct server_command *cmd,
 338                 const char *handler)
 339 {
 340         int ret, i;
 341
 342         for (i = 1; cmd->name; cmd++, i++) {
 343                 char *perms = cmd_perms_itohuman(cmd->perms);
 344                 ret = rc4_send_va_buffer(rc4c, "%s\t%s\t%s\t%s\n", cmd->name,
 345                         handler,
 346                         perms,
 347                         cmd->description);
 348                 free(perms);
 349                 if (ret < 0)
 350                         return ret;
 351         }
 352         return 1;
 353 }
 354
 355 /* returns string that must be freed by the caller */
 356 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 357 {
 358         struct server_command *cmd;
 359
 360         for (cmd = server_cmds; cmd->name; cmd++)
 361                 if (!strcmp(cmd->name, name)) {
 362                         if (handler)
 363                                 *handler = para_strdup("server"); /* server commands */
 364                         return cmd;
 365                 }
 366         /* not found, look for commands supported by afs */
 367         for (cmd = afs_cmds; cmd->name; cmd++)
 368                 if (!strcmp(cmd->name, name)) {
 369                         if (handler)
 370                                 *handler = para_strdup("afs");
 371                         return cmd;
 372                 }
 373         return NULL;
 374 }
 375
 376 /* help */
 377 int com_help(struct rc4_context *rc4c, int argc, char * const * argv)
 378 {
 379         struct server_command *cmd;
 380         char *perms, *handler;
 381         int ret;
 382
 383         if (argc < 2) {
 384                 /* no argument given, print list of commands */
 385                 if ((ret = send_list_of_commands(rc4c, server_cmds, "server")) < 0)
 386                         return ret;
 387                 return send_list_of_commands(rc4c, afs_cmds, "afs");
 388         }
 389         /* argument given for help */
 390         cmd = get_cmd_ptr(argv[1], &handler);
 391         if (!cmd) {
 392                 free(handler);
 393                 return -E_BAD_CMD;
 394         }
 395         perms = cmd_perms_itohuman(cmd->perms);
 396         ret = rc4_send_va_buffer(rc4c,
 397                 "%s - %s\n\n"
 398                 "handler: %s\n"
 399                 "permissions: %s\n"
 400                 "usage: %s\n\n"
 401                 "%s\n",
 402                 argv[1],
 403                 cmd->description,
 404                 handler,
 405                 perms,
 406                 cmd->usage,
 407                 cmd->help
 408         );
 409         free(perms);
 410         free(handler);
 411         return ret;
 412 }
 413
 414 /* hup */
 415 int com_hup(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 416 {
 417         if (argc != 1)
 418                 return -E_COMMAND_SYNTAX;
 419         kill(getppid(), SIGHUP);
 420         return 1;
 421 }
 422
 423 /* term */
 424 int com_term(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 425 {
 426         if (argc != 1)
 427                 return -E_COMMAND_SYNTAX;
 428         kill(getppid(), SIGTERM);
 429         return 1;
 430 }
 431
 432 int com_play(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 433 {
 434         if (argc != 1)
 435                 return -E_COMMAND_SYNTAX;
 436         mutex_lock(mmd_mutex);
 437         mmd->new_vss_status_flags |= VSS_PLAYING;
 438         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 439         mutex_unlock(mmd_mutex);
 440         return 1;
 441
 442 }
 443
 444 /* stop */
 445 int com_stop(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 446 {
 447         if (argc != 1)
 448                 return -E_COMMAND_SYNTAX;
 449         mutex_lock(mmd_mutex);
 450         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 451         mmd->new_vss_status_flags &= ~VSS_REPOS;
 452         mmd->new_vss_status_flags |= VSS_NEXT;
 453         mutex_unlock(mmd_mutex);
 454         return 1;
 455 }
 456
 457 /* pause */
 458 int com_pause(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 459 {
 460         if (argc != 1)
 461                 return -E_COMMAND_SYNTAX;
 462         mutex_lock(mmd_mutex);
 463         if (!vss_paused() && !vss_stopped()) {
 464                 mmd->events++;
 465                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 466                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 467         }
 468         mutex_unlock(mmd_mutex);
 469         return 1;
 470 }
 471
 472 /* next */
 473 int com_next(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 474 {
 475         if (argc != 1)
 476                 return -E_COMMAND_SYNTAX;
 477         mutex_lock(mmd_mutex);
 478         mmd->events++;
 479         mmd->new_vss_status_flags |= VSS_NEXT;
 480         mutex_unlock(mmd_mutex);
 481         return 1;
 482 }
 483
 484 /* nomore */
 485 int com_nomore(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 486 {
 487         if (argc != 1)
 488                 return -E_COMMAND_SYNTAX;
 489         mutex_lock(mmd_mutex);
 490         if (vss_playing() || vss_paused())
 491                 mmd->new_vss_status_flags |= VSS_NOMORE;
 492         mutex_unlock(mmd_mutex);
 493         return 1;
 494 }
 495
 496 /* ff */
 497 int com_ff(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 498 {
 499         long promille;
 500         int ret, backwards = 0;
 501         unsigned i;
 502         char c;
 503
 504         if (argc != 2)
 505                 return -E_COMMAND_SYNTAX;
 506         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 507                 return -E_COMMAND_SYNTAX;
 508         if (ret > 1 && c == '-')
 509                 backwards = 1; /* jmp backwards */
 510         mutex_lock(mmd_mutex);
 511         ret = -E_NO_AUDIO_FILE;
 512         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 513                 goto out;
 514         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 515         if (backwards)
 516                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 517         else
 518                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 519         if (promille < 0)
 520                 promille = 0;
 521         if (promille >  1000) {
 522                 mmd->new_vss_status_flags |= VSS_NEXT;
 523                 goto out;
 524         }
 525         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 526         mmd->new_vss_status_flags |= VSS_REPOS;
 527         mmd->new_vss_status_flags &= ~VSS_NEXT;
 528         mmd->events++;
 529         ret = 1;
 530 out:
 531         mutex_unlock(mmd_mutex);
 532         return ret;
 533 }
 534
 535 /* jmp */
 536 int com_jmp(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 537 {
 538         long unsigned int i;
 539         int ret;
 540
 541         if (argc != 2)
 542                 return -E_COMMAND_SYNTAX;
 543         if (sscanf(argv[1], "%lu", &i) <= 0)
 544                 return -E_COMMAND_SYNTAX;
 545         mutex_lock(mmd_mutex);
 546         ret = -E_NO_AUDIO_FILE;
 547         if (!mmd->afd.afhi.chunks_total)
 548                 goto out;
 549         if (i > 100)
 550                 i = 100;
 551         PARA_INFO_LOG("jumping to %lu%%\n", i);
 552         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 553         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 554                 mmd->chunks_sent, mmd->offset);
 555         mmd->new_vss_status_flags |= VSS_REPOS;
 556         mmd->new_vss_status_flags &= ~VSS_NEXT;
 557         ret = 1;
 558         mmd->events++;
 559 out:
 560         mutex_unlock(mmd_mutex);
 561         return ret;
 562 }
 563
 564 /*
 565  * check if perms are sufficient to exec a command having perms cmd_perms.
 566  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 567  */
 568 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 569 {
 570         PARA_DEBUG_LOG("checking permissions\n");
 571         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 572 }
 573
 574 /*
 575  * Parse first string from *cmd and lookup in table of valid commands.
 576  * On error, NULL is returned.
 577  */
 578 static struct server_command *parse_cmd(const char *cmdstr)
 579 {
 580         char buf[255];
 581         int n = 0;
 582
 583         sscanf(cmdstr, "%200s%n", buf, &n);
 584         if (!n)
 585                 return NULL;
 586         buf[n] = '\0';
 587         return get_cmd_ptr(buf, NULL);
 588 }
 589
 590 static int read_command(struct rc4_context *rc4c, char **result)
 591 {
 592         int ret;
 593         char buf[4096];
 594         char *command = NULL;
 595
 596         for (;;) {
 597                 size_t numbytes;
 598                 char *p;
 599
 600                 ret = rc4_recv_buffer(rc4c, buf, sizeof(buf));
 601                 if (ret < 0)
 602                         goto out;
 603                 if (!ret)
 604                         break;
 605                 numbytes = ret;
 606                 ret = -E_COMMAND_SYNTAX;
 607                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 608                         goto out;
 609                 command = para_strcat(command, buf);
 610                 p = strstr(command, EOC_MSG);
 611                 if (p) {
 612                         *p = '\0';
 613                         break;
 614                 }
 615         }
 616         ret = command? 1 : -E_COMMAND_SYNTAX;
 617 out:
 618         if (ret < 0)
 619                 free(command);
 620         else
 621                 *result = command;
 622         return ret;
 623
 624 }
 625
 626 static void reset_signals(void)
 627 {
 628         para_sigaction(SIGCHLD, SIG_IGN);
 629         para_sigaction(SIGINT, SIG_DFL);
 630         para_sigaction(SIGTERM, SIG_DFL);
 631         para_sigaction(SIGHUP, SIG_DFL);
 632 }
 633
 634 /**
 635  * Perform user authentication and execute a command.
 636  *
 637  * \param fd The file descriptor to send output to.
 638  * \param peername Identifies the connecting peer.
 639  *
 640  * Whenever para_server accepts an incoming tcp connection on
 641  * the port it listens on, it forks and the resulting child
 642  * calls this function.
 643  *
 644  * An RSA-based challenge/response is used to authenticate
 645  * the peer. It that authentication succeeds, a random RC4
 646  * session key is generated and sent back to the peer,
 647  * encrypted with its RSA public key.  From this point on,
 648  * all transfers are crypted with this session key.
 649  *
 650  * Next it is checked if the peer supplied  a valid server command or a command
 651  * for the audio file selector.  If yes, and if the user has sufficient
 652  * permissions to execute that command, the function calls the corresponding
 653  * command handler which does argument checking and further processing.
 654  *
 655  * In order to cope with a DOS attacks, a timeout is set up
 656  * which terminates the function if the connection was not
 657  * authenticated when the timeout expires.
 658  *
 659  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 660  */
 661 __noreturn void handle_connect(int fd, const char *peername)
 662 {
 663         int ret, argc;
 664         char buf[4096];
 665         unsigned char rand_buf[CHALLENGE_SIZE + 2 * RC4_KEY_LEN];
 666         unsigned char challenge_sha1[HASH_SIZE];
 667         struct user *u;
 668         struct server_command *cmd = NULL;
 669         char **argv = NULL;
 670         char *p, *command = NULL;
 671         size_t numbytes;
 672         struct rc4_context rc4c = {.fd = fd};
 673
 674         reset_signals();
 675         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 676         ret = mark_fd_blocking(fd);
 677         if (ret < 0)
 678                 goto err_out;
 679         /* send Welcome message */
 680         ret = send_va_buffer(fd, "This is para_server, version "
 681                 PACKAGE_VERSION  ".\n" );
 682         if (ret < 0)
 683                 goto err_out;
 684         /* recv auth request line */
 685         ret = recv_buffer(fd, buf, sizeof(buf));
 686         if (ret < 0)
 687                 goto err_out;
 688         if (ret < 10) {
 689                 ret = -E_AUTH_REQUEST;
 690                 goto err_out;
 691         }
 692         numbytes = ret;
 693         ret = -E_AUTH_REQUEST;
 694         if (strncmp(buf, AUTH_REQUEST_MSG, strlen(AUTH_REQUEST_MSG)))
 695                 goto err_out;
 696         p = buf + strlen(AUTH_REQUEST_MSG);
 697         PARA_DEBUG_LOG("received auth request for user %s\n", p);
 698         ret = -E_BAD_USER;
 699         u = lookup_user(p);
 700         if (u) {
 701                 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
 702                 ret = para_encrypt_buffer(u->rsa, rand_buf, sizeof(rand_buf),
 703                         (unsigned char *)buf);
 704                 if (ret < 0)
 705                         goto err_out;
 706                 numbytes = ret;
 707         } else {
 708                 /*
 709                  * We don't want to reveal our user names, so we send a
 710                  * challenge to the client even if the user does not exist, and
 711                  * fail the authentication later.
 712                  */
 713                 numbytes = 256;
 714                 get_random_bytes_or_die((unsigned char *)buf, numbytes);
 715         }
 716         PARA_DEBUG_LOG("sending %zu byte challenge + rc4 keys (%u bytes)\n",
 717                 CHALLENGE_SIZE, numbytes);
 718         ret = send_bin_buffer(fd, buf, numbytes);
 719         if (ret < 0)
 720                 goto net_err;
 721         /* recv challenge response */
 722         ret = recv_bin_buffer(fd, buf, HASH_SIZE);
 723         if (ret < 0)
 724                 goto net_err;
 725         numbytes = ret;
 726         PARA_DEBUG_LOG("received %zu bytes challenge response\n", ret);
 727         ret = -E_BAD_USER;
 728         if (!u)
 729                 goto net_err;
 730         /*
 731          * The correct response is the sha1 of the first CHALLENGE_SIZE bytes
 732          * of the random data.
 733          */
 734         ret = -E_BAD_AUTH;
 735         if (numbytes != HASH_SIZE)
 736                 goto net_err;
 737         sha1_hash((char *)rand_buf, CHALLENGE_SIZE, challenge_sha1);
 738         if (memcmp(challenge_sha1, buf, HASH_SIZE))
 739                 goto net_err;
 740         /* auth successful */
 741         alarm(0);
 742         PARA_INFO_LOG("good auth for %s\n", u->name);
 743         /* init rc4 keys with the second part of the random buffer */
 744         RC4_set_key(&rc4c.recv_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE);
 745         RC4_set_key(&rc4c.send_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE
 746                 + RC4_KEY_LEN);
 747         ret = rc4_send_buffer(&rc4c, PROCEED_MSG);
 748         if (ret < 0)
 749                 goto net_err;
 750         ret = read_command(&rc4c, &command);
 751         if (ret == -E_COMMAND_SYNTAX)
 752                 goto err_out;
 753         if (ret < 0)
 754                 goto net_err;
 755         ret = -E_BAD_CMD;
 756         cmd = parse_cmd(command);
 757         if (!cmd)
 758                 goto err_out;
 759         /* valid command, check permissions */
 760         ret = check_perms(u->perms, cmd);
 761         if (ret < 0)
 762                 goto err_out;
 763         /* valid command and sufficient perms */
 764         argc = split_args(command, &argv, "\n");
 765         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 766                         peername);
 767         ret = cmd->handler(&rc4c, argc, argv);
 768         mutex_lock(mmd_mutex);
 769         mmd->num_commands++;
 770         mutex_unlock(mmd_mutex);
 771         if (ret >= 0)
 772                 goto out;
 773 err_out:
 774         rc4_send_va_buffer(&rc4c, "%s\n", para_strerror(-ret));
 775 net_err:
 776         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 777 out:
 778         free(command);
 779         free(argv);
 780         mutex_lock(mmd_mutex);
 781         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 782                 mmd->events++;
 783         mmd->active_connections--;
 784         mutex_unlock(mmd_mutex);
 785         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 786 }