command.c

   1 /*
   2  * Copyright (C) 1997-2007 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file command.c Client authentication and server commands. */
   8
   9 #include <signal.h>
  10 #include <sys/time.h>
  11 #include <sys/types.h>
  12 #include <dirent.h>
  13 #include <openssl/rc4.h>
  14
  15 #include "para.h"
  16 #include "error.h"
  17 #include "server.cmdline.h"
  18 #include "string.h"
  19 #include "afh.h"
  20 #include "afs.h"
  21 #include "server.h"
  22 #include "vss.h"
  23 #include "send.h"
  24 #include "rc4.h"
  25 #include "net.h"
  26 #include "daemon.h"
  27 #include "fd.h"
  28 #include "list.h"
  29 #include "user_list.h"
  30 #include "server_command_list.h"
  31 #include "afs_command_list.h"
  32
  33 /** Commands including options must be shorter than this. */
  34 #define MAX_COMMAND_LEN 32768
  35
  36 static RC4_KEY rc4_recv_key;
  37 static RC4_KEY rc4_send_key;
  38 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  39
  40 extern const char *status_item_list[NUM_STAT_ITEMS];
  41 extern struct misc_meta_data *mmd;
  42 extern struct sender senders[];
  43
  44 static void dummy(__a_unused int s)
  45 {}
  46
  47 static void mmd_dup(struct misc_meta_data *new_mmd)
  48 {
  49         mmd_lock();
  50         *new_mmd = *mmd;
  51         mmd_unlock();
  52 }
  53
  54 /*
  55  * compute human readable string containing
  56  * vss status for given integer value
  57  */
  58 static char *vss_status_tohuman(unsigned int flags)
  59 {
  60         if (flags & VSS_PLAYING)
  61                 return para_strdup("playing");
  62         else if (flags & VSS_NEXT)
  63                 return para_strdup("stopped");
  64         else
  65                 return para_strdup("paused");
  66 }
  67
  68 /*
  69  * return human readable permission string. Never returns NULL.
  70  */
  71 static char *cmd_perms_itohuman(unsigned int perms)
  72 {
  73         char *msg = para_malloc(5 * sizeof(char));
  74
  75         msg[0] = perms & AFS_READ? 'a' : '-';
  76         msg[1] = perms & AFS_WRITE? 'A' : '-';
  77         msg[2] = perms & VSS_READ? 'v' : '-';
  78         msg[3] = perms & VSS_WRITE? 'V' : '-';
  79         msg[4] = '\0';
  80         return msg;
  81 }
  82
  83 /*
  84  * Never returns NULL.
  85  */
  86 static char *vss_get_status_flags(unsigned int flags)
  87 {
  88         char *msg = para_malloc(5 * sizeof(char));
  89
  90         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  91         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
  92         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
  93         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
  94         msg[4] = '\0';
  95         return msg;
  96 }
  97
  98 static char *get_status(struct misc_meta_data *nmmd)
  99 {
 100         char *basename, *dirname, *ret, mtime[30] = "";
 101         char *status, *flags; /* vss status info */
 102         char *ut = uptime_str();
 103         long offset = (nmmd->offset + 500) / 1000;
 104         struct timeval now;
 105         struct tm mtime_tm;
 106
 107         /* report real status */
 108         status = vss_status_tohuman(nmmd->vss_status_flags);
 109         flags = vss_get_status_flags(nmmd->vss_status_flags);
 110         basename = para_basename(nmmd->afd.path);
 111         dirname = para_dirname(nmmd->afd.path);
 112         if (basename) {
 113                 localtime_r(&nmmd->mtime, &mtime_tm);
 114                 strftime(mtime, 29, "%a %b %d %Y", &mtime_tm);
 115         }
 116         gettimeofday(&now, NULL);
 117         ret = make_message(
 118                 "%s:%zu\n"      "%s:%s\n"               "%s:%lu\n"      "%s:%u\n"
 119                 "%s:%s\n"       "%s:%s\n"       "%s:%s\n"       "%s:%u\n"
 120                 "%s:%li\n"      "%s:%s\n"       "%s:%s\n" "%s"
 121                 "%s:%s\n"       "%s:%lu.%lu\n"  "%s:%lu.%lu\n" "%s:%s\n"
 122                 "%s:%s\n"       "%s:%u\n",
 123                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 124                 status_item_list[SI_MTIME], mtime,
 125                 status_item_list[SI_LENGTH], nmmd->afd.afhi.seconds_total,
 126                 status_item_list[SI_NUM_PLAYED], nmmd->num_played,
 127
 128                 status_item_list[SI_BASENAME], basename ? basename : "(none)",
 129                 status_item_list[SI_STATUS], status,
 130                 status_item_list[SI_STATUS_FLAGS], flags,
 131                 status_item_list[SI_IMAGE_ID], nmmd->afd.afsi.image_id,
 132
 133                 status_item_list[SI_OFFSET], offset,
 134                 status_item_list[SI_FORMAT], basename?
 135                         audio_format_name(nmmd->afd.afsi.audio_format_id)
 136                         : "",
 137                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 138                 nmmd->afd.afhi.info_string,
 139
 140                 status_item_list[SI_UPTIME], ut,
 141                 status_item_list[SI_STREAM_START],
 142                         (long unsigned)nmmd->stream_start.tv_sec,
 143                         (long unsigned)nmmd->stream_start.tv_usec,
 144                 status_item_list[SI_CURRENT_TIME],
 145                         (long unsigned)now.tv_sec,
 146                         (long unsigned)now.tv_usec,
 147                 status_item_list[SI_ATTRIBUTES], mmd->afd.attributes_string,
 148
 149                 status_item_list[SI_DIRECTORY], dirname? dirname : "(none)",
 150                 status_item_list[SI_LYRICS_ID], nmmd->afd.afsi.lyrics_id
 151
 152         );
 153         free(basename);
 154         free(dirname);
 155         free(flags);
 156         free(status);
 157         free(ut);
 158         return ret;
 159 }
 160
 161 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 162 {
 163         int i;
 164         /* this has to match sender.h */
 165         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 166
 167         scd->sender_num = -1;
 168         if (argc < 2)
 169                 return -E_COMMAND_SYNTAX;
 170         for (i = 0; senders[i].name; i++)
 171                 if (!strcmp(senders[i].name, argv[1]))
 172                         break;
 173         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 174         if (!senders[i].name)
 175                 return -E_COMMAND_SYNTAX;
 176         scd->sender_num = i;
 177         for (i = 0; subcmds[i]; i++)
 178                 if (!strcmp(subcmds[i], argv[2]))
 179                         break;
 180         if (!subcmds[i])
 181                 return -E_COMMAND_SYNTAX;
 182         scd->cmd_num = i;
 183         mmd_lock();
 184         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 185                 mmd_unlock();
 186                 return -E_SENDER_CMD;
 187         }
 188         mmd_unlock();
 189         switch (scd->cmd_num) {
 190         case SENDER_ON:
 191         case SENDER_OFF:
 192                 if (argc != 3)
 193                         return -E_COMMAND_SYNTAX;
 194                 break;
 195         case SENDER_DENY:
 196         case SENDER_ALLOW:
 197                 if (argc != 4 && argc != 5)
 198                         return -E_COMMAND_SYNTAX;
 199                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 200                         return -E_COMMAND_SYNTAX;
 201                 scd->netmask = 32;
 202                 if (argc == 5) {
 203                         scd->netmask = atoi(argv[4]);
 204                         if (scd->netmask < 0 || scd->netmask > 32)
 205                                 return -E_COMMAND_SYNTAX;
 206                 }
 207                 break;
 208         case SENDER_ADD:
 209         case SENDER_DELETE:
 210                 if (argc != 4 && argc != 5)
 211                         return -E_COMMAND_SYNTAX;
 212                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 213                         return -E_COMMAND_SYNTAX;
 214                 scd->port = -1;
 215                 if (argc == 5) {
 216                         scd->port = atoi(argv[4]);
 217                         if (scd->port < 0 || scd->port > 65535)
 218                                 return -E_COMMAND_SYNTAX;
 219                 }
 220                 break;
 221         default:
 222                 return -E_COMMAND_SYNTAX;
 223         }
 224         return 1;
 225 }
 226
 227 int com_sender(int fd, int argc, char * const * argv)
 228 {
 229         int i, ret;
 230         struct sender_command_data scd;
 231
 232         if (argc < 2) {
 233                 char *msg = NULL;
 234                 for (i = 0; senders[i].name; i++) {
 235                         char *tmp = make_message("%s%s\n",
 236                                 msg? msg : "", senders[i].name);
 237                         free(msg);
 238                         msg = tmp;
 239                 }
 240                 ret = send_buffer(fd, msg);
 241                 free(msg);
 242                 return ret;
 243         }
 244         ret = check_sender_args(argc, argv, &scd);
 245         if (ret < 0) {
 246                 char *msg;
 247                 if (scd.sender_num < 0)
 248                         return ret;
 249                 msg = senders[scd.sender_num].help();
 250                 send_buffer(fd, msg);
 251                 free(msg);
 252                 return 1;
 253         }
 254         for (i = 0; i < 10; i++) {
 255                 mmd_lock();
 256                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 257                         mmd_unlock();
 258                         usleep(100 * 1000);
 259                         continue;
 260                 }
 261                 mmd->sender_cmd_data = scd;
 262                 mmd_unlock();
 263                 break;
 264         }
 265         return (i < 10)? 1 : -E_LOCK;
 266 }
 267
 268 /* server info */
 269 int com_si(int fd, int argc, __a_unused char * const * argv)
 270 {
 271         int i, ret;
 272         char *ut;
 273         char *sender_info = NULL, *sender_list = NULL;
 274
 275         if (argc != 1)
 276                 return -E_COMMAND_SYNTAX;
 277         mmd_lock();
 278         for (i = 0; senders[i].name; i++) {
 279                 char *info = senders[i].info();
 280                 sender_info = para_strcat(sender_info, info);
 281                 free(info);
 282                 sender_list = para_strcat(sender_list, senders[i].name);
 283                 sender_list = para_strcat(sender_list, " ");
 284         }
 285         ut = uptime_str();
 286         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 287                 "pid: %d\n"
 288                 "connections (active/accepted/total): %u/%u/%u\n"
 289                 "current loglevel: %i\n"
 290                 "supported audio formats: %s\n"
 291                 "supported senders: %s\n"
 292                 "%s",
 293                 ut, mmd->num_played,
 294                 getppid(),
 295                 mmd->active_connections,
 296                 mmd->num_commands,
 297                 mmd->num_connects,
 298                 conf.loglevel_arg,
 299                 supported_audio_formats(),
 300                 sender_list,
 301                 sender_info
 302         );
 303         mmd_unlock();
 304         free(ut);
 305         free(sender_list);
 306         free(sender_info);
 307         return ret;
 308 }
 309
 310 /* version */
 311 int com_version(int fd, int argc, __a_unused char * const * argv)
 312 {
 313         if (argc != 1)
 314                 return -E_COMMAND_SYNTAX;
 315         return send_buffer(fd, VERSION_TEXT("server")
 316                 "built: " BUILD_DATE "\n"
 317                 SYSTEM ", " CC_VERSION "\n"
 318         );
 319 }
 320
 321 /* stat */
 322 int com_stat(int fd, int argc, char * const * argv)
 323 {
 324         int ret, num = 0;/* status will be printed that many
 325                           * times. num <= 0 means: print forever
 326                           */
 327         struct misc_meta_data tmp, *nmmd = &tmp;
 328         char *s;
 329
 330         signal(SIGUSR1, dummy);
 331
 332         if (argc > 1)
 333                 num = atoi(argv[1]);
 334         for (;;) {
 335
 336                 mmd_dup(nmmd);
 337                 s = get_status(nmmd);
 338                 ret = send_buffer(fd, s);
 339                 free(s);
 340                 if (ret < 0)
 341                         goto out;
 342                 ret = 1;
 343                 if (num == 1)
 344                         goto out;
 345                 sleep(50);
 346                 if (getppid() == 1)
 347                         return -E_SERVER_CRASH;
 348         }
 349 out:
 350         return ret;
 351 }
 352
 353 static int send_list_of_commands(int fd, struct server_command *cmd,
 354                 const char *handler)
 355 {
 356         int ret, i;
 357
 358         for (i = 1; cmd->name; cmd++, i++) {
 359                 char *perms = cmd_perms_itohuman(cmd->perms);
 360                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 361                         handler,
 362                         perms,
 363                         cmd->description);
 364                 free(perms);
 365                 if (ret < 0)
 366                         return ret;
 367         }
 368         return 1;
 369 }
 370
 371 /* returns string that must be freed by the caller */
 372 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 373 {
 374         struct server_command *cmd;
 375
 376         for (cmd = server_cmds; cmd->name; cmd++)
 377                 if (!strcmp(cmd->name, name)) {
 378                         if (handler)
 379                                 *handler = para_strdup("server"); /* server commands */
 380                         return cmd;
 381                 }
 382         /* not found, look for commands supported by afs */
 383         for (cmd = afs_cmds; cmd->name; cmd++)
 384                 if (!strcmp(cmd->name, name)) {
 385                         if (handler)
 386                                 *handler = para_strdup("afs");
 387                         return cmd;
 388                 }
 389         return NULL;
 390 }
 391
 392 /* help */
 393 int com_help(int fd, int argc, char * const * argv)
 394 {
 395         struct server_command *cmd;
 396         char *perms, *handler;
 397         int ret;
 398
 399         if (argc < 2) {
 400                 /* no argument given, print list of commands */
 401                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 402                         return ret;
 403                 return send_list_of_commands(fd, afs_cmds, "afs");
 404         }
 405         /* argument given for help */
 406         cmd = get_cmd_ptr(argv[1], &handler);
 407         if (!cmd) {
 408                 free(handler);
 409                 return -E_BAD_CMD;
 410         }
 411         perms = cmd_perms_itohuman(cmd->perms);
 412         ret = send_va_buffer(fd,
 413                 "%s - %s\n\n"
 414                 "handler: %s\n"
 415                 "permissions: %s\n"
 416                 "usage: %s\n\n"
 417                 "%s\n",
 418                 argv[1],
 419                 cmd->description,
 420                 handler,
 421                 perms,
 422                 cmd->usage,
 423                 cmd->help
 424         );
 425         free(perms);
 426         free(handler);
 427         return ret;
 428 }
 429
 430 /* hup */
 431 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 432 {
 433         if (argc != 1)
 434                 return -E_COMMAND_SYNTAX;
 435         kill(getppid(), SIGHUP);
 436         return 1;
 437 }
 438
 439 /* term */
 440 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 441 {
 442         if (argc != 1)
 443                 return -E_COMMAND_SYNTAX;
 444         kill(getppid(), SIGTERM);
 445         return 1;
 446 }
 447
 448 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 449 {
 450         if (argc != 1)
 451                 return -E_COMMAND_SYNTAX;
 452         mmd_lock();
 453         mmd->new_vss_status_flags |= VSS_PLAYING;
 454         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 455         mmd_unlock();
 456         return 1;
 457
 458 }
 459
 460 /* stop */
 461 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 462 {
 463         if (argc != 1)
 464                 return -E_COMMAND_SYNTAX;
 465         mmd_lock();
 466         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 467         mmd->new_vss_status_flags &= ~VSS_REPOS;
 468         mmd->new_vss_status_flags |= VSS_NEXT;
 469         mmd_unlock();
 470         return 1;
 471 }
 472
 473 /* pause */
 474 int com_pause(__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         if (!vss_paused())
 480                 mmd->events++;
 481         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 482         mmd->new_vss_status_flags &= ~VSS_NEXT;
 483         mmd_unlock();
 484         return 1;
 485 }
 486
 487 /* next */
 488 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 489 {
 490         if (argc != 1)
 491                 return -E_COMMAND_SYNTAX;
 492         mmd_lock();
 493         mmd->events++;
 494         mmd->new_vss_status_flags |= VSS_NEXT;
 495         mmd_unlock();
 496         return 1;
 497 }
 498
 499 /* nomore */
 500 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 501 {
 502         if (argc != 1)
 503                 return -E_COMMAND_SYNTAX;
 504         mmd_lock();
 505         if (vss_playing() || vss_paused())
 506                 mmd->new_vss_status_flags |= VSS_NOMORE;
 507         mmd_unlock();
 508         return 1;
 509 }
 510
 511 /* ff */
 512 int com_ff(__a_unused int fd, int argc, char * const * argv)
 513 {
 514         long promille;
 515         int ret, backwards = 0;
 516         unsigned i;
 517         char c;
 518
 519         if (argc != 2)
 520                 return -E_COMMAND_SYNTAX;
 521         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 522                 return -E_COMMAND_SYNTAX;
 523         if (ret > 1 && c == '-')
 524                 backwards = 1; /* jmp backwards */
 525         mmd_lock();
 526         ret = -E_NO_AUDIO_FILE;
 527         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 528                 goto out;
 529         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 530         if (backwards)
 531                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 532         else
 533                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 534         if (promille < 0)
 535                 promille = 0;
 536         if (promille >  1000) {
 537                 mmd->new_vss_status_flags |= VSS_NEXT;
 538                 goto out;
 539         }
 540         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 541         mmd->new_vss_status_flags |= VSS_REPOS;
 542         mmd->new_vss_status_flags &= ~VSS_NEXT;
 543         mmd->events++;
 544         ret = 1;
 545 out:
 546         mmd_unlock();
 547         return ret;
 548 }
 549
 550 /* jmp */
 551 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 552 {
 553         long unsigned int i;
 554         int ret;
 555
 556         if (argc != 2)
 557                 return -E_COMMAND_SYNTAX;
 558         if (sscanf(argv[1], "%lu", &i) <= 0)
 559                 return -E_COMMAND_SYNTAX;
 560         mmd_lock();
 561         ret = -E_NO_AUDIO_FILE;
 562         if (!mmd->afd.afhi.chunks_total)
 563                 goto out;
 564         if (i > 100)
 565                 i = 100;
 566         PARA_INFO_LOG("jumping to %lu%%\n", i);
 567         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 568         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 569                 mmd->chunks_sent, mmd->offset);
 570         mmd->new_vss_status_flags |= VSS_REPOS;
 571         mmd->new_vss_status_flags &= ~VSS_NEXT;
 572         ret = 1;
 573         mmd->events++;
 574 out:
 575         mmd_unlock();
 576         return ret;
 577 }
 578
 579 /*
 580  * check if perms are sufficient to exec a command having perms cmd_perms.
 581  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 582  */
 583 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 584 {
 585         PARA_DEBUG_LOG("%s", "checking permissions\n");
 586         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 587 }
 588
 589 /*
 590  * Parse first string from *cmd and lookup in table of valid commands.
 591  * On error, NULL is returned.
 592  */
 593 static struct server_command *parse_cmd(const char *cmdstr)
 594 {
 595         char buf[255];
 596         int n = 0;
 597
 598         sscanf(cmdstr, "%200s%n", buf, &n);
 599         if (!n)
 600                 return NULL;
 601         buf[n] = '\0';
 602         return get_cmd_ptr(buf, NULL);
 603 }
 604
 605 static void init_rc4_keys(void)
 606 {
 607         int i;
 608
 609         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 610                 rc4_buf[i] = para_random(256);
 611         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 612                 (unsigned char) rc4_buf[0],
 613                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 614         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 615         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 616 }
 617
 618 static void rc4_recv(unsigned long len, const unsigned char *indata,
 619                 unsigned char *outdata, __a_unused void *private_data)
 620 {
 621         RC4(&rc4_recv_key, len, indata, outdata);
 622 }
 623
 624 static void rc4_send(unsigned long len, const unsigned char *indata,
 625                 unsigned char *outdata, __a_unused void *private_data)
 626 {
 627         RC4(&rc4_send_key, len, indata, outdata);
 628 }
 629
 630 static int read_command(int fd, char **result)
 631 {
 632         int ret;
 633         char buf[4096];
 634         char *command = NULL;
 635
 636         for (;;) {
 637                 size_t numbytes;
 638                 char *p;
 639
 640                 ret = recv_buffer(fd, buf, sizeof(buf));
 641                 if (ret < 0)
 642                         goto out;
 643                 if (!ret)
 644                         break;
 645                 numbytes = ret;
 646                 ret = -E_COMMAND_SYNTAX;
 647                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 648                         goto out;
 649                 command = para_strcat(command, buf);
 650                 p = strstr(command, EOC_MSG);
 651                 if (p) {
 652                         *p = '\0';
 653                         break;
 654                 }
 655         }
 656         ret = command? 1 : -E_COMMAND_SYNTAX;
 657 out:
 658         if (ret < 0)
 659                 free(command);
 660         else
 661                 *result = command;
 662         return ret;
 663
 664 }
 665
 666 /**
 667  * perform user authentication and execute a command
 668  *
 669  * \param fd the file descriptor to send output to
 670  * \param addr socket address info of peer
 671  *
 672  * \return EXIT_SUCCESS or EXIT_FAILURE
 673  *
 674  * Whenever para_server accepts an incoming tcp connection on
 675  * the port it listens on, it forks and the resulting child
 676  * calls this function.
 677  *
 678  * An RSA-based challenge/response is used to authenticate
 679  * the peer. It that authentication succeeds, a random RC4
 680  * session key is generated and sent back to the peer,
 681  * encrypted with its RSA public key.  From this point on,
 682  * all transfers are crypted with this session key.
 683  *
 684  * Next it is checked if the peer supplied  a valid server command or a command
 685  * for the audio file selector.  If yes, and if the user has sufficient
 686  * permissions to execute that command, the function calls the corresponding
 687  * command handler which does argument checking and further processing.
 688  *
 689  * In order to cope with a DOS attacks, a timeout is set up
 690  * which terminates the function if the connection was not
 691  * authenticated when the timeout expires.
 692  *
 693  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 694  */
 695 int handle_connect(int fd, struct sockaddr_in *addr)
 696 {
 697         int ret, argc, use_rc4 = 0;
 698         char buf[4096];
 699         unsigned char crypt_buf[MAXLINE];
 700         struct user *u;
 701         struct server_command *cmd = NULL;
 702         long unsigned challenge_nr, chall_response;
 703         char **argv = NULL;
 704         char *p, *command = NULL;
 705         size_t numbytes;
 706
 707         signal(SIGCHLD, SIG_IGN);
 708         signal(SIGINT, SIG_DFL);
 709         signal(SIGTERM, SIG_DFL);
 710         signal(SIGHUP, SIG_DFL);
 711         signal(SIGUSR1, SIG_IGN);
 712
 713         challenge_nr = random();
 714         /* send Welcome message */
 715         ret = send_va_buffer(fd, "This is para_server, version "
 716                 PACKAGE_VERSION  ".\n" );
 717         if (ret < 0)
 718                 goto err_out;
 719         /* recv auth request line */
 720         ret = recv_buffer(fd, buf, sizeof(buf));
 721         if (ret < 0)
 722                 goto err_out;
 723         if (ret <= 6) {
 724                 ret = -E_AUTH;
 725                 goto err_out;
 726         }
 727         numbytes = ret;
 728         ret = -E_AUTH;
 729         if (strncmp(buf, "auth ", 5))
 730                 goto err_out;
 731
 732         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 733                 p = buf + 5; /* client version < 0.2.6 */
 734         else {
 735                 p = buf + 9; /* client version >= 0.2.6 */
 736                 use_rc4 = 1;
 737         }
 738         PARA_DEBUG_LOG("received %s request for user %s\n",
 739                 use_rc4? "rc4" : "auth", p);
 740         ret = -E_BAD_USER;
 741         u = lookup_user(p);
 742         if (!u)
 743                 goto err_out;
 744         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 745         if (ret <= 0)
 746                 goto err_out;
 747         numbytes = ret;
 748         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 749         /* We can't use send_buffer here since buf may contain null bytes */
 750         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 751         if (ret < 0)
 752                 goto err_out;
 753         /* recv decrypted number */
 754         ret = recv_buffer(fd, buf, sizeof(buf));
 755         if (ret < 0)
 756                 goto err_out;
 757         numbytes = ret;
 758         ret = -E_AUTH;
 759         if (!numbytes)
 760                 goto err_out;
 761         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 762                         || chall_response != challenge_nr)
 763                 goto err_out;
 764         /* auth successful, send 'Proceed' message */
 765         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 766         sprintf(buf, "%s", PROCEED_MSG);
 767         if (use_rc4) {
 768                 init_rc4_keys();
 769                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 770                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 771                 if (ret <= 0)
 772                         goto err_out;
 773                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 774         } else
 775                 numbytes = strlen(buf);
 776         ret = send_bin_buffer(fd, buf, numbytes);
 777         if (ret < 0)
 778                 goto err_out;
 779         if (use_rc4)
 780                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 781         ret = read_command(fd, &command);
 782         if (ret < 0)
 783                 goto err_out;
 784         ret = -E_BAD_CMD;
 785         cmd = parse_cmd(command);
 786         if (!cmd)
 787                 goto err_out;
 788         /* valid command, check permissions */
 789         ret = check_perms(u->perms, cmd);
 790         if (ret < 0)
 791                 goto err_out;
 792         /* valid command and sufficient perms */
 793         alarm(0);
 794         argc = split_args(command, &argv, "\n");
 795         mmd_lock();
 796         mmd->num_commands++;
 797         mmd_unlock();
 798         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 799                 inet_ntoa(addr->sin_addr));
 800         ret = cmd->handler(fd, argc, argv);
 801         if (ret >= 0) {
 802                 ret = EXIT_SUCCESS;
 803                 goto out;
 804         }
 805 err_out:
 806         PARA_NOTICE_LOG("%s\n", PARA_STRERROR(-ret));
 807         if (ret != -E_SEND && ret != -E_RECV)
 808                 send_va_buffer(fd, "%s\n", PARA_STRERROR(-ret));
 809         ret = EXIT_FAILURE;
 810 out:
 811         free(command);
 812         free(argv);
 813         mmd_lock();
 814         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 815                 mmd->events++;
 816         mmd->active_connections--;
 817         mmd_unlock();
 818         return ret;
 819 }