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 *bar, *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         localtime_r(&nmmd->mtime, &mtime_tm);
 108         strftime(mtime, 29, "%a %b %d %Y", &mtime_tm);
 109         /* report real status */
 110         status = vss_status_tohuman(nmmd->vss_status_flags);
 111         flags = vss_get_status_flags(nmmd->vss_status_flags);
 112         bar = para_basename(nmmd->filename);
 113         gettimeofday(&now, NULL);
 114         ret = make_message(
 115                 "%s:%zu\n"      "%s:%s\n"               "%s:%lu\n"      "%s:%u\n"
 116                 "%s:%s\n"       "%s:%s\n"       "%s:%s\n"       "%s:%s\n"
 117                 "%s:%li\n"      "%s:%s\n"       "%s:%s\n" "%s"
 118                 "%s:%s\n"       "%s:%lu.%lu\n"  "%s:%lu.%lu\n",
 119                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 120                 status_item_list[SI_MTIME], mtime,
 121                 status_item_list[SI_LENGTH], nmmd->afd.afhi.seconds_total,
 122                 status_item_list[SI_NUM_PLAYED], nmmd->num_played,
 123
 124                 status_item_list[SI_STATUS_BAR], bar ? bar : "(none)",
 125                 status_item_list[SI_STATUS], status,
 126                 status_item_list[SI_STATUS_FLAGS], flags,
 127                 status_item_list[SI_SELECTOR], "FIXME",
 128
 129                 status_item_list[SI_OFFSET], offset,
 130                 status_item_list[SI_FORMAT], audio_format_name(nmmd->afd.afsi.audio_format_id),
 131                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 132                 nmmd->afd.afhi.info_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         );
 143         free(bar);
 144         free(flags);
 145         free(status);
 146         free(ut);
 147         return ret;
 148 }
 149
 150 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 151 {
 152         int i;
 153         /* this has to match sender.h */
 154         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 155
 156         scd->sender_num = -1;
 157         if (argc < 2)
 158                 return -E_COMMAND_SYNTAX;
 159         for (i = 0; senders[i].name; i++)
 160                 if (!strcmp(senders[i].name, argv[1]))
 161                         break;
 162         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 163         if (!senders[i].name)
 164                 return -E_COMMAND_SYNTAX;
 165         scd->sender_num = i;
 166         for (i = 0; subcmds[i]; i++)
 167                 if (!strcmp(subcmds[i], argv[2]))
 168                         break;
 169         if (!subcmds[i])
 170                 return -E_COMMAND_SYNTAX;
 171         scd->cmd_num = i;
 172         mmd_lock();
 173         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 174                 mmd_unlock();
 175                 return -E_SENDER_CMD;
 176         }
 177         mmd_unlock();
 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 (!inet_pton(AF_INET, argv[3], &scd->addr))
 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                 break;
 197         case SENDER_ADD:
 198         case SENDER_DELETE:
 199                 if (argc != 4 && argc != 5)
 200                         return -E_COMMAND_SYNTAX;
 201                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 202                         return -E_COMMAND_SYNTAX;
 203                 scd->port = -1;
 204                 if (argc == 5) {
 205                         scd->port = atoi(argv[4]);
 206                         if (scd->port < 0 || scd->port > 65535)
 207                                 return -E_COMMAND_SYNTAX;
 208                 }
 209                 break;
 210         default:
 211                 return -E_COMMAND_SYNTAX;
 212         }
 213         return 1;
 214 }
 215
 216 int com_sender(int fd, int argc, char * const * argv)
 217 {
 218         int i, ret;
 219         struct sender_command_data scd;
 220
 221         if (argc < 2) {
 222                 char *msg = NULL;
 223                 for (i = 0; senders[i].name; i++) {
 224                         char *tmp = make_message("%s%s\n",
 225                                 msg? msg : "", senders[i].name);
 226                         free(msg);
 227                         msg = tmp;
 228                 }
 229                 ret = send_buffer(fd, msg);
 230                 free(msg);
 231                 return ret;
 232         }
 233         ret = check_sender_args(argc, argv, &scd);
 234         if (ret < 0) {
 235                 char *msg;
 236                 if (scd.sender_num < 0)
 237                         return ret;
 238                 msg = senders[scd.sender_num].help();
 239                 send_buffer(fd, msg);
 240                 free(msg);
 241                 return 1;
 242         }
 243         for (i = 0; i < 10; i++) {
 244                 mmd_lock();
 245                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 246                         mmd_unlock();
 247                         usleep(100 * 1000);
 248                         continue;
 249                 }
 250                 mmd->sender_cmd_data = scd;
 251                 mmd_unlock();
 252                 break;
 253         }
 254         return (i < 10)? 1 : -E_LOCK;
 255 }
 256
 257 /* server info */
 258 int com_si(int fd, int argc, __a_unused char * const * argv)
 259 {
 260         int i, ret;
 261         char *ut;
 262         char *sender_info = NULL, *sender_list = NULL;
 263
 264         if (argc != 1)
 265                 return -E_COMMAND_SYNTAX;
 266         mmd_lock();
 267         for (i = 0; senders[i].name; i++) {
 268                 char *info = senders[i].info();
 269                 sender_info = para_strcat(sender_info, info);
 270                 free(info);
 271                 sender_list = para_strcat(sender_list, senders[i].name);
 272                 sender_list = para_strcat(sender_list, " ");
 273         }
 274         ut = uptime_str();
 275         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 276                 "pid: %d\n"
 277                 "connections (active/accepted/total): %u/%u/%u\n"
 278                 "current loglevel: %i\n"
 279                 "supported audio formats: %s\n"
 280                 "supported senders: %s\n"
 281                 "%s",
 282                 ut, mmd->num_played,
 283                 getppid(),
 284                 mmd->active_connections,
 285                 mmd->num_commands,
 286                 mmd->num_connects,
 287                 conf.loglevel_arg,
 288                 supported_audio_formats(),
 289                 sender_list,
 290                 sender_info
 291         );
 292         mmd_unlock();
 293         free(ut);
 294         free(sender_list);
 295         free(sender_info);
 296         return ret;
 297 }
 298
 299 /* version */
 300 int com_version(int fd, int argc, __a_unused char * const * argv)
 301 {
 302         if (argc != 1)
 303                 return -E_COMMAND_SYNTAX;
 304         return send_buffer(fd, VERSION_TEXT("server")
 305                 "built: " BUILD_DATE "\n"
 306                 SYSTEM ", " CC_VERSION "\n"
 307         );
 308 }
 309
 310 /* stat */
 311 int com_stat(int fd, int argc, char * const * argv)
 312 {
 313         int ret, num = 0;/* status will be printed that many
 314                           * times. num <= 0 means: print forever
 315                           */
 316         struct misc_meta_data tmp, *nmmd = &tmp;
 317         char *s;
 318
 319         signal(SIGUSR1, dummy);
 320
 321         if (argc > 1)
 322                 num = atoi(argv[1]);
 323         for (;;) {
 324
 325                 mmd_dup(nmmd);
 326                 s = get_status(nmmd);
 327                 ret = send_buffer(fd, s);
 328                 free(s);
 329                 if (ret < 0)
 330                         goto out;
 331                 ret = 1;
 332                 if (num == 1)
 333                         goto out;
 334                 sleep(50);
 335                 if (getppid() == 1)
 336                         return -E_SERVER_CRASH;
 337         }
 338 out:
 339         return ret;
 340 }
 341
 342 static int send_list_of_commands(int fd, struct server_command *cmd,
 343                 const char *handler)
 344 {
 345         int ret, i;
 346
 347         for (i = 1; cmd->name; cmd++, i++) {
 348                 char *perms = cmd_perms_itohuman(cmd->perms);
 349                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 350                         handler,
 351                         perms,
 352                         cmd->description);
 353                 free(perms);
 354                 if (ret < 0)
 355                         return ret;
 356         }
 357         return 1;
 358 }
 359
 360 /* returns string that must be freed by the caller */
 361 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 362 {
 363         struct server_command *cmd;
 364
 365         for (cmd = server_cmds; cmd->name; cmd++)
 366                 if (!strcmp(cmd->name, name)) {
 367                         if (handler)
 368                                 *handler = para_strdup("para_server"); /* server commands */
 369                         return cmd;
 370                 }
 371         /* not found, look for commands supported by afs */
 372         for (cmd = afs_cmds; cmd->name; cmd++)
 373                 if (!strcmp(cmd->name, name))
 374                         return cmd;
 375         return NULL;
 376 }
 377
 378 /* help */
 379 int com_help(int fd, int argc, char * const * argv)
 380 {
 381         struct server_command *cmd;
 382         char *perms, *handler;
 383         int ret;
 384
 385         if (argc < 2) {
 386                 /* no argument given, print list of commands */
 387                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 388                         return ret;
 389                 return send_list_of_commands(fd, afs_cmds, "afs");
 390         }
 391         /* argument given for help */
 392         cmd = get_cmd_ptr(argv[1], &handler);
 393         if (!cmd) {
 394                 free(handler);
 395                 return -E_BAD_CMD;
 396         }
 397         perms = cmd_perms_itohuman(cmd->perms);
 398         ret = send_va_buffer(fd,
 399                 "%s - %s\n\n"
 400                 "handler: %s\n"
 401                 "permissions: %s\n"
 402                 "usage: %s\n\n"
 403                 "%s\n",
 404                 argv[1],
 405                 cmd->description,
 406                 handler,
 407                 perms,
 408                 cmd->usage,
 409                 cmd->help
 410         );
 411         free(perms);
 412         free(handler);
 413         return ret;
 414 }
 415
 416 /* hup */
 417 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 418 {
 419         if (argc != 1)
 420                 return -E_COMMAND_SYNTAX;
 421         kill(getppid(), SIGHUP);
 422         return 1;
 423 }
 424
 425 /* term */
 426 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 427 {
 428         if (argc != 1)
 429                 return -E_COMMAND_SYNTAX;
 430         kill(getppid(), SIGTERM);
 431         return 1;
 432 }
 433
 434 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 435 {
 436         if (argc != 1)
 437                 return -E_COMMAND_SYNTAX;
 438         mmd_lock();
 439         mmd->new_vss_status_flags |= VSS_PLAYING;
 440         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 441         mmd_unlock();
 442         return 1;
 443
 444 }
 445
 446 /* stop */
 447 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 448 {
 449         if (argc != 1)
 450                 return -E_COMMAND_SYNTAX;
 451         mmd_lock();
 452         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 453         mmd->new_vss_status_flags &= ~VSS_REPOS;
 454         mmd->new_vss_status_flags |= VSS_NEXT;
 455         mmd_unlock();
 456         return 1;
 457 }
 458
 459 /* pause */
 460 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 461 {
 462         if (argc != 1)
 463                 return -E_COMMAND_SYNTAX;
 464         mmd_lock();
 465         if (!vss_paused())
 466                 mmd->events++;
 467         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 468         mmd->new_vss_status_flags &= ~VSS_NEXT;
 469         mmd_unlock();
 470         return 1;
 471 }
 472
 473 /* next */
 474 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 475 {
 476         if (argc != 1)
 477                 return -E_COMMAND_SYNTAX;
 478         mmd_lock();
 479         mmd->events++;
 480         mmd->new_vss_status_flags |= VSS_NEXT;
 481         mmd_unlock();
 482         return 1;
 483 }
 484
 485 /* nomore */
 486 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 487 {
 488         if (argc != 1)
 489                 return -E_COMMAND_SYNTAX;
 490         mmd_lock();
 491         if (vss_playing() || vss_paused())
 492                 mmd->new_vss_status_flags |= VSS_NOMORE;
 493         mmd_unlock();
 494         return 1;
 495 }
 496
 497 /* ff */
 498 int com_ff(__a_unused int fd, int argc, char * const * argv)
 499 {
 500         long promille;
 501         int ret, backwards = 0;
 502         unsigned i;
 503         char c;
 504
 505         if (argc != 2)
 506                 return -E_COMMAND_SYNTAX;
 507         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 508                 return -E_COMMAND_SYNTAX;
 509         if (ret > 1 && c == '-')
 510                 backwards = 1; /* jmp backwards */
 511         mmd_lock();
 512         ret = -E_NO_AUDIO_FILE;
 513         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 514                 goto out;
 515         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 516         if (backwards)
 517                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 518         else
 519                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 520         if (promille < 0)
 521                 promille = 0;
 522         if (promille >  1000) {
 523                 mmd->new_vss_status_flags |= VSS_NEXT;
 524                 goto out;
 525         }
 526         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 527         mmd->new_vss_status_flags |= VSS_REPOS;
 528         mmd->new_vss_status_flags &= ~VSS_NEXT;
 529         mmd->events++;
 530         ret = 1;
 531 out:
 532         mmd_unlock();
 533         return ret;
 534 }
 535
 536 /* jmp */
 537 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 538 {
 539         long unsigned int i;
 540         int ret;
 541
 542         if (argc != 2)
 543                 return -E_COMMAND_SYNTAX;
 544         if (sscanf(argv[1], "%lu", &i) <= 0)
 545                 return -E_COMMAND_SYNTAX;
 546         mmd_lock();
 547         ret = -E_NO_AUDIO_FILE;
 548         if (!mmd->afd.afhi.chunks_total)
 549                 goto out;
 550         if (i > 100)
 551                 i = 100;
 552         PARA_INFO_LOG("jumping to %lu%%\n", i);
 553         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 554         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 555                 mmd->chunks_sent, mmd->offset);
 556         mmd->new_vss_status_flags |= VSS_REPOS;
 557         mmd->new_vss_status_flags &= ~VSS_NEXT;
 558         ret = 1;
 559         mmd->events++;
 560 out:
 561         mmd_unlock();
 562         return ret;
 563 }
 564
 565 /*
 566  * check if perms are sufficient to exec a command having perms cmd_perms.
 567  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 568  */
 569 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 570 {
 571         PARA_DEBUG_LOG("%s", "checking permissions\n");
 572         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 573 }
 574
 575 /*
 576  * Parse first string from *cmd and lookup in table of valid commands.
 577  * On error, NULL is returned.
 578  */
 579 static struct server_command *parse_cmd(const char *cmdstr)
 580 {
 581         char buf[255];
 582         int n = 0;
 583
 584         sscanf(cmdstr, "%200s%n", buf, &n);
 585         if (!n)
 586                 return NULL;
 587         buf[n] = '\0';
 588         return get_cmd_ptr(buf, NULL);
 589 }
 590
 591 static long int para_rand(long unsigned max)
 592 {
 593         return (long int) ((max + 0.0) * (random() / (RAND_MAX + 1.0)));
 594 }
 595
 596 static void init_rc4_keys(void)
 597 {
 598         int i;
 599
 600         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 601                 rc4_buf[i] = para_rand(256);
 602         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 603                 (unsigned char) rc4_buf[0],
 604                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 605         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 606         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 607 }
 608
 609 static void rc4_recv(unsigned long len, const unsigned char *indata,
 610                 unsigned char *outdata, __a_unused void *private_data)
 611 {
 612         RC4(&rc4_recv_key, len, indata, outdata);
 613 }
 614
 615 static void rc4_send(unsigned long len, const unsigned char *indata,
 616                 unsigned char *outdata, __a_unused void *private_data)
 617 {
 618         RC4(&rc4_send_key, len, indata, outdata);
 619 }
 620
 621 static int read_command(int fd, char **result)
 622 {
 623         int ret;
 624         char buf[4096];
 625         char *command = NULL;
 626
 627         for (;;) {
 628                 size_t numbytes;
 629                 char *p;
 630
 631                 ret = recv_buffer(fd, buf, sizeof(buf));
 632                 if (ret < 0)
 633                         goto out;
 634                 if (!ret)
 635                         break;
 636                 numbytes = ret;
 637                 ret = -E_COMMAND_SYNTAX;
 638                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 639                         goto out;
 640                 command = para_strcat(command, buf);
 641                 p = strstr(command, EOC_MSG);
 642                 if (p) {
 643                         *p = '\0';
 644                         break;
 645                 }
 646         }
 647         ret = command? 1 : -E_COMMAND_SYNTAX;
 648 out:
 649         if (ret < 0)
 650                 free(command);
 651         else
 652                 *result = command;
 653         return ret;
 654
 655 }
 656
 657 /**
 658  * perform user authentication and execute a command
 659  *
 660  * \param fd the file descriptor to send output to
 661  * \param addr socket address info of peer
 662  *
 663  * \return EXIT_SUCCESS or EXIT_FAILURE
 664  *
 665  * Whenever para_server accepts an incoming tcp connection on
 666  * the port it listens on, it forks and the resulting child
 667  * calls this function.
 668  *
 669  * An RSA-based challenge/response is used to authenticate
 670  * the peer. It that authentication succeeds, a random RC4
 671  * session key is generated and sent back to the peer,
 672  * encrypted with its RSA public key.  From this point on,
 673  * all transfers are crypted with this session key.
 674  *
 675  * Next it is checked if the peer supplied  a valid server command or a command
 676  * for the audio file selector.  If yes, and if the user has sufficient
 677  * permissions to execute that command, the function calls the corresponding
 678  * command handler which does argument checking and further processing.
 679  *
 680  * In order to cope with a DOS attacks, a timeout is set up
 681  * which terminates the function if the connection was not
 682  * authenticated when the timeout expires.
 683  *
 684  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 685  */
 686 int handle_connect(int fd, struct sockaddr_in *addr)
 687 {
 688         int ret, argc, use_rc4 = 0;
 689         char buf[4096];
 690         unsigned char crypt_buf[MAXLINE];
 691         struct user *u;
 692         struct server_command *cmd = NULL;
 693         long unsigned challenge_nr, chall_response;
 694         char **argv = NULL;
 695         char *p, *command = NULL;
 696         size_t numbytes;
 697
 698         signal(SIGCHLD, SIG_IGN);
 699         signal(SIGINT, SIG_DFL);
 700         signal(SIGTERM, SIG_DFL);
 701         signal(SIGHUP, SIG_DFL);
 702         signal(SIGUSR1, SIG_IGN);
 703
 704         challenge_nr = random();
 705         /* send Welcome message */
 706         ret = send_va_buffer(fd, "This is para_server, version "
 707                 PACKAGE_VERSION  ".\n" );
 708         if (ret < 0)
 709                 goto err_out;
 710         /* recv auth request line */
 711         ret = recv_buffer(fd, buf, sizeof(buf));
 712         if (ret < 0)
 713                 goto err_out;
 714         if (ret <= 6) {
 715                 ret = -E_AUTH;
 716                 goto err_out;
 717         }
 718         numbytes = ret;
 719         ret = -E_AUTH;
 720         if (strncmp(buf, "auth ", 5))
 721                 goto err_out;
 722
 723         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 724                 p = buf + 5; /* client version < 0.2.6 */
 725         else {
 726                 p = buf + 9; /* client version >= 0.2.6 */
 727                 use_rc4 = 1;
 728         }
 729         PARA_DEBUG_LOG("received %s request for user %s\n",
 730                 use_rc4? "rc4" : "auth", p);
 731         ret = -E_BAD_USER;
 732         u = lookup_user(p);
 733         if (!u)
 734                 goto err_out;
 735         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 736         if (ret <= 0)
 737                 goto err_out;
 738         numbytes = ret;
 739         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 740         /* We can't use send_buffer here since buf may contain null bytes */
 741         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 742         if (ret < 0)
 743                 goto err_out;
 744         /* recv decrypted number */
 745         ret = recv_buffer(fd, buf, sizeof(buf));
 746         if (ret < 0)
 747                 goto err_out;
 748         numbytes = ret;
 749         ret = -E_AUTH;
 750         if (!numbytes)
 751                 goto err_out;
 752         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 753                         || chall_response != challenge_nr)
 754                 goto err_out;
 755         /* auth successful, send 'Proceed' message */
 756         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 757         sprintf(buf, "%s", PROCEED_MSG);
 758         if (use_rc4) {
 759                 init_rc4_keys();
 760                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 761                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 762                 if (ret <= 0)
 763                         goto err_out;
 764                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 765         } else
 766                 numbytes = strlen(buf);
 767         ret = send_bin_buffer(fd, buf, numbytes);
 768         if (ret < 0)
 769                 goto err_out;
 770         if (use_rc4)
 771                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 772         ret = read_command(fd, &command);
 773         if (ret < 0)
 774                 goto err_out;
 775         ret = -E_BAD_CMD;
 776         cmd = parse_cmd(command);
 777         if (!cmd)
 778                 goto err_out;
 779         /* valid command, check permissions */
 780         ret = check_perms(u->perms, cmd);
 781         if (ret < 0)
 782                 goto err_out;
 783         /* valid command and sufficient perms */
 784         alarm(0);
 785         argc = split_args(command, &argv, "\n");
 786         mmd_lock();
 787         mmd->num_commands++;
 788         mmd_unlock();
 789         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 790                 inet_ntoa(addr->sin_addr));
 791         ret = cmd->handler(fd, argc, argv);
 792         if (ret >= 0) {
 793                 ret = EXIT_SUCCESS;
 794                 goto out;
 795         }
 796 err_out:
 797         PARA_NOTICE_LOG("%s\n", PARA_STRERROR(-ret));
 798         if (ret != -E_SEND && ret != -E_RECV)
 799                 send_va_buffer(fd, "%s\n", PARA_STRERROR(-ret));
 800         ret = EXIT_FAILURE;
 801 out:
 802         free(command);
 803         free(argv);
 804         mmd_lock();
 805         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 806                 mmd->events++;
 807         mmd->active_connections--;
 808         mmd_unlock();
 809         return ret;
 810 }