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 #include <osl.h>
  15
  16 #include "para.h"
  17 #include "error.h"
  18 #include "crypt.h"
  19 #include "command.h"
  20 #include "server.cmdline.h"
  21 #include "string.h"
  22 #include "afh.h"
  23 #include "afs.h"
  24 #include "server.h"
  25 #include "vss.h"
  26 #include "list.h"
  27 #include "send.h"
  28 #include "rc4.h"
  29 #include "net.h"
  30 #include "daemon.h"
  31 #include "fd.h"
  32 #include "ipc.h"
  33 #include "user_list.h"
  34 #include "server_command_list.h"
  35 #include "afs_command_list.h"
  36 #include "sched.h"
  37 #include "signal.h"
  38
  39 /** Commands including options must be shorter than this. */
  40 #define MAX_COMMAND_LEN 32768
  41
  42 extern int mmd_mutex;
  43 extern struct misc_meta_data *mmd;
  44 extern struct sender senders[];
  45 int send_afs_status(struct rc4_context *rc4c, int parser_friendly);
  46
  47 const char *status_item_list[] = {STATUS_ITEM_ARRAY};
  48
  49 static void dummy(__a_unused int s)
  50 {
  51 }
  52
  53 static void mmd_dup(struct misc_meta_data *new_mmd)
  54 {
  55         mutex_lock(mmd_mutex);
  56         *new_mmd = *mmd;
  57         mutex_unlock(mmd_mutex);
  58 }
  59
  60 /*
  61  * Compute human readable string containing vss status for given integer value.
  62  *
  63  * We don't want to use vss_playing() and friends here because we take a
  64  * snapshot of the mmd struct and use the copy for computing the state of the
  65  * vss. If the real data were used, we would take the mmd lock for a rather
  66  * long time or risk to get an inconsistent view.
  67  */
  68 static char *vss_status_tohuman(unsigned int flags)
  69 {
  70         if (flags & VSS_PLAYING)
  71                 return para_strdup("playing");
  72         if (flags & VSS_NEXT)
  73                 return para_strdup("stopped");
  74         return para_strdup("paused");
  75 }
  76
  77 /*
  78  * return human readable permission string. Never returns NULL.
  79  */
  80 static char *cmd_perms_itohuman(unsigned int perms)
  81 {
  82         char *msg = para_malloc(5 * sizeof(char));
  83
  84         msg[0] = perms & AFS_READ? 'a' : '-';
  85         msg[1] = perms & AFS_WRITE? 'A' : '-';
  86         msg[2] = perms & VSS_READ? 'v' : '-';
  87         msg[3] = perms & VSS_WRITE? 'V' : '-';
  88         msg[4] = '\0';
  89         return msg;
  90 }
  91
  92 /*
  93  * Never returns NULL.
  94  */
  95 static char *vss_get_status_flags(unsigned int flags)
  96 {
  97         char *msg = para_malloc(5 * sizeof(char));
  98
  99         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
 100         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
 101         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 102         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 103         msg[4] = '\0';
 104         return msg;
 105 }
 106
 107 static char *get_status(struct misc_meta_data *nmmd, int parser_friendly)
 108 {
 109         char mtime[30] = "";
 110         char *status, *flags; /* vss status info */
 111         char *ut = uptime_str();
 112         long offset = (nmmd->offset + 500) / 1000;
 113         struct timeval current_time;
 114         struct tm mtime_tm;
 115         struct para_buffer b = {.flags = parser_friendly? PBF_SIZE_PREFIX : 0};
 116
 117         /* report real status */
 118         status = vss_status_tohuman(nmmd->vss_status_flags);
 119         flags = vss_get_status_flags(nmmd->vss_status_flags);
 120         if (nmmd->size) { /* parent currently has an audio file open */
 121                 localtime_r(&nmmd->mtime, &mtime_tm);
 122                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 123         }
 124         gettimeofday(&current_time, NULL);
 125         WRITE_STATUS_ITEM(&b, SI_FILE_SIZE, "%zu\n", nmmd->size / 1024);
 126         WRITE_STATUS_ITEM(&b, SI_MTIME, "%s\n", mtime);
 127         WRITE_STATUS_ITEM(&b, SI_STATUS, "%s\n", status);
 128         WRITE_STATUS_ITEM(&b, SI_STATUS_FLAGS, "%s\n", flags);
 129         WRITE_STATUS_ITEM(&b, SI_OFFSET, "%li\n", offset);
 130         WRITE_STATUS_ITEM(&b, SI_AFS_MODE, "%s\n", mmd->afs_mode_string);
 131         WRITE_STATUS_ITEM(&b, SI_STREAM_START, "%lu.%lu\n",
 132                 (long unsigned)nmmd->stream_start.tv_sec,
 133                 (long unsigned)nmmd->stream_start.tv_usec);
 134         WRITE_STATUS_ITEM(&b, SI_CURRENT_TIME, "%lu.%lu\n",
 135                 (long unsigned)current_time.tv_sec,
 136                 (long unsigned)current_time.tv_usec);
 137         free(flags);
 138         free(status);
 139         free(ut);
 140         return b.buf;
 141 }
 142
 143 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 144 {
 145         int i;
 146         /* this has to match sender.h */
 147         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 148
 149         scd->sender_num = -1;
 150         if (argc < 2)
 151                 return -E_COMMAND_SYNTAX;
 152         for (i = 0; senders[i].name; i++)
 153                 if (!strcmp(senders[i].name, argv[1]))
 154                         break;
 155         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 156         if (!senders[i].name)
 157                 return -E_COMMAND_SYNTAX;
 158         scd->sender_num = i;
 159         for (i = 0; subcmds[i]; i++)
 160                 if (!strcmp(subcmds[i], argv[2]))
 161                         break;
 162         if (!subcmds[i])
 163                 return -E_COMMAND_SYNTAX;
 164         scd->cmd_num = i;
 165         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 166                 return -E_SENDER_CMD;
 167         switch (scd->cmd_num) {
 168         case SENDER_ON:
 169         case SENDER_OFF:
 170                 if (argc != 3)
 171                         return -E_COMMAND_SYNTAX;
 172                 break;
 173         case SENDER_DENY:
 174         case SENDER_ALLOW:
 175                 if (argc != 4 || parse_cidr(argv[3], scd->host,
 176                                 sizeof(scd->host), &scd->netmask) == NULL)
 177                         return -E_COMMAND_SYNTAX;
 178                 break;
 179         case SENDER_ADD:
 180         case SENDER_DELETE:
 181                 if (argc != 4)
 182                         return -E_COMMAND_SYNTAX;
 183                 return parse_fec_url(argv[3], scd);
 184         default:
 185                 return -E_COMMAND_SYNTAX;
 186         }
 187         return 1;
 188 }
 189
 190 int com_sender(struct rc4_context *rc4c, int argc, char * const * argv)
 191 {
 192         int i, ret;
 193         struct sender_command_data scd;
 194
 195         if (argc < 2) {
 196                 char *msg = NULL;
 197                 for (i = 0; senders[i].name; i++) {
 198                         char *tmp = make_message("%s%s\n",
 199                                 msg? msg : "", senders[i].name);
 200                         free(msg);
 201                         msg = tmp;
 202                 }
 203                 ret = rc4_send_buffer(rc4c, msg);
 204                 free(msg);
 205                 return ret;
 206         }
 207         ret = check_sender_args(argc, argv, &scd);
 208         if (ret < 0) {
 209                 char *msg;
 210                 if (scd.sender_num < 0)
 211                         return ret;
 212                 msg = senders[scd.sender_num].help();
 213                 ret = rc4_send_buffer(rc4c, msg);
 214                 free(msg);
 215                 return ret;
 216         }
 217         for (i = 0; i < 10; i++) {
 218                 mutex_lock(mmd_mutex);
 219                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 220                         mutex_unlock(mmd_mutex);
 221                         usleep(100 * 1000);
 222                         continue;
 223                 }
 224                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 225                 mutex_unlock(mmd_mutex);
 226                 break;
 227         }
 228         return (i < 10)? 1 : -E_LOCK;
 229 }
 230
 231 /* server info */
 232 int com_si(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 233 {
 234         int i, ret;
 235         char *ut;
 236         char *sender_info = NULL, *sender_list = NULL;
 237
 238         if (argc != 1)
 239                 return -E_COMMAND_SYNTAX;
 240         mutex_lock(mmd_mutex);
 241         for (i = 0; senders[i].name; i++) {
 242                 char *info = senders[i].info();
 243                 sender_info = para_strcat(sender_info, info);
 244                 free(info);
 245                 sender_list = para_strcat(sender_list, senders[i].name);
 246                 sender_list = para_strcat(sender_list, " ");
 247         }
 248         ut = uptime_str();
 249         ret = rc4_send_va_buffer(rc4c, "up: %s\nplayed: %u\n"
 250                 "server_pid: %d\n"
 251                 "afs_pid: %d\n"
 252                 "connections (active/accepted/total): %u/%u/%u\n"
 253                 "current loglevel: %s\n"
 254                 "supported audio formats: %s\n"
 255                 "supported senders: %s\n"
 256                 "%s",
 257                 ut, mmd->num_played,
 258                 (int)getppid(),
 259                 (int)mmd->afs_pid,
 260                 mmd->active_connections,
 261                 mmd->num_commands,
 262                 mmd->num_connects,
 263                 conf.loglevel_arg,
 264                 supported_audio_formats(),
 265                 sender_list,
 266                 sender_info
 267         );
 268         mutex_unlock(mmd_mutex);
 269         free(ut);
 270         free(sender_list);
 271         free(sender_info);
 272         return ret;
 273 }
 274
 275 /* version */
 276 int com_version(struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 277 {
 278         if (argc != 1)
 279                 return -E_COMMAND_SYNTAX;
 280         return rc4_send_buffer(rc4c, VERSION_TEXT("server")
 281                 "built: " BUILD_DATE "\n"
 282                 UNAME_RS ", " CC_VERSION "\n"
 283         );
 284 }
 285
 286 #define EMPTY_STATUS_ITEMS \
 287         ITEM(PATH) \
 288         ITEM(DIRECTORY) \
 289         ITEM(BASENAME) \
 290         ITEM(SCORE) \
 291         ITEM(ATTRIBUTES_BITMAP) \
 292         ITEM(ATTRIBUTES_TXT) \
 293         ITEM(HASH) \
 294         ITEM(IMAGE_ID) \
 295         ITEM(IMAGE_NAME) \
 296         ITEM(LYRICS_ID) \
 297         ITEM(LYRICS_NAME) \
 298         ITEM(BITRATE) \
 299         ITEM(FORMAT) \
 300         ITEM(FREQUENCY) \
 301         ITEM(CHANNELS) \
 302         ITEM(DURATION) \
 303         ITEM(SECONDS_TOTAL) \
 304         ITEM(NUM_PLAYED) \
 305         ITEM(LAST_PLAYED) \
 306         ITEM(TECHINFO) \
 307         ITEM(ARTIST) \
 308         ITEM(TITLE) \
 309         ITEM(YEAR) \
 310         ITEM(ALBUM) \
 311         ITEM(COMMENT) \
 312         ITEM(AMPLIFICATION)
 313
 314 /**
 315  * Write a list of audio-file related status items with empty values.
 316  *
 317  * This is used by vss when currently no audio file is open.
 318  */
 319 static char *empty_status_items(int parser_friendly)
 320 {
 321         if (parser_friendly)
 322                 return make_message(
 323                         #define ITEM(x) "0004 %02x:\n"
 324                         EMPTY_STATUS_ITEMS
 325                         #undef ITEM
 326                         #define ITEM(x) , SI_ ## x
 327                         EMPTY_STATUS_ITEMS
 328                         #undef ITEM
 329                 );
 330         return make_message(
 331                 #define ITEM(x) "%s:\n"
 332                 EMPTY_STATUS_ITEMS
 333                 #undef ITEM
 334                 #define ITEM(x) ,status_item_list[SI_ ## x]
 335                 EMPTY_STATUS_ITEMS
 336                 #undef ITEM
 337         );
 338 }
 339 #undef EMPTY_STATUS_ITEMS
 340
 341 /* stat */
 342 int com_stat(struct rc4_context *rc4c, int argc, char * const * argv)
 343 {
 344         int i, ret;
 345         struct misc_meta_data tmp, *nmmd = &tmp;
 346         char *s;
 347         int32_t num = 0;
 348         int parser_friendly = 0;
 349
 350         para_sigaction(SIGUSR1, dummy);
 351
 352         for (i = 1; i < argc; i++) {
 353                 const char *arg = argv[i];
 354                 if (arg[0] != '-')
 355                         break;
 356                 if (!strcmp(arg, "--")) {
 357                         i++;
 358                         break;
 359                 }
 360                 if (!strncmp(arg, "-n=", 3)) {
 361                         ret = para_atoi32(arg + 3, &num);
 362                         if (ret < 0)
 363                                 return ret;
 364                         continue;
 365                 }
 366                 if (!strcmp(arg, "-p")) {
 367                         parser_friendly = 1;
 368                         continue;
 369                 }
 370         }
 371         if (i != argc)
 372                 return -E_COMMAND_SYNTAX;
 373         for (;;) {
 374                 mmd_dup(nmmd);
 375                 s = get_status(nmmd, parser_friendly);
 376                 ret = rc4_send_buffer(rc4c, s);
 377                 free(s);
 378                 if (ret < 0)
 379                         goto out;
 380                 if (nmmd->vss_status_flags & VSS_NEXT) {
 381                         static char *esi;
 382                         if (!esi)
 383                                 esi = empty_status_items(parser_friendly);
 384                         ret = rc4_send_buffer(rc4c, esi);
 385                         if (ret < 0)
 386                                 goto out;
 387                 } else
 388                         send_afs_status(rc4c, parser_friendly);
 389                 ret = 1;
 390                 if (num > 0 && !--num)
 391                         goto out;
 392                 sleep(50);
 393                 if (getppid() == 1)
 394                         return -E_SERVER_CRASH;
 395         }
 396 out:
 397         return ret;
 398 }
 399
 400 static int send_list_of_commands(struct rc4_context *rc4c, struct server_command *cmd,
 401                 const char *handler)
 402 {
 403         int ret, i;
 404
 405         for (i = 1; cmd->name; cmd++, i++) {
 406                 char *perms = cmd_perms_itohuman(cmd->perms);
 407                 ret = rc4_send_va_buffer(rc4c, "%s\t%s\t%s\t%s\n", cmd->name,
 408                         handler,
 409                         perms,
 410                         cmd->description);
 411                 free(perms);
 412                 if (ret < 0)
 413                         return ret;
 414         }
 415         return 1;
 416 }
 417
 418 /* returns string that must be freed by the caller */
 419 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 420 {
 421         struct server_command *cmd;
 422
 423         for (cmd = server_cmds; cmd->name; cmd++)
 424                 if (!strcmp(cmd->name, name)) {
 425                         if (handler)
 426                                 *handler = para_strdup("server"); /* server commands */
 427                         return cmd;
 428                 }
 429         /* not found, look for commands supported by afs */
 430         for (cmd = afs_cmds; cmd->name; cmd++)
 431                 if (!strcmp(cmd->name, name)) {
 432                         if (handler)
 433                                 *handler = para_strdup("afs");
 434                         return cmd;
 435                 }
 436         return NULL;
 437 }
 438
 439 /* help */
 440 int com_help(struct rc4_context *rc4c, int argc, char * const * argv)
 441 {
 442         struct server_command *cmd;
 443         char *perms, *handler;
 444         int ret;
 445
 446         if (argc < 2) {
 447                 /* no argument given, print list of commands */
 448                 if ((ret = send_list_of_commands(rc4c, server_cmds, "server")) < 0)
 449                         return ret;
 450                 return send_list_of_commands(rc4c, afs_cmds, "afs");
 451         }
 452         /* argument given for help */
 453         cmd = get_cmd_ptr(argv[1], &handler);
 454         if (!cmd) {
 455                 free(handler);
 456                 return -E_BAD_CMD;
 457         }
 458         perms = cmd_perms_itohuman(cmd->perms);
 459         ret = rc4_send_va_buffer(rc4c,
 460                 "%s - %s\n\n"
 461                 "handler: %s\n"
 462                 "permissions: %s\n"
 463                 "usage: %s\n\n"
 464                 "%s\n",
 465                 argv[1],
 466                 cmd->description,
 467                 handler,
 468                 perms,
 469                 cmd->usage,
 470                 cmd->help
 471         );
 472         free(perms);
 473         free(handler);
 474         return ret;
 475 }
 476
 477 /* hup */
 478 int com_hup(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 479 {
 480         if (argc != 1)
 481                 return -E_COMMAND_SYNTAX;
 482         kill(getppid(), SIGHUP);
 483         return 1;
 484 }
 485
 486 /* term */
 487 int com_term(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 488 {
 489         if (argc != 1)
 490                 return -E_COMMAND_SYNTAX;
 491         kill(getppid(), SIGTERM);
 492         return 1;
 493 }
 494
 495 int com_play(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 496 {
 497         if (argc != 1)
 498                 return -E_COMMAND_SYNTAX;
 499         mutex_lock(mmd_mutex);
 500         mmd->new_vss_status_flags |= VSS_PLAYING;
 501         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 502         mutex_unlock(mmd_mutex);
 503         return 1;
 504
 505 }
 506
 507 /* stop */
 508 int com_stop(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 509 {
 510         if (argc != 1)
 511                 return -E_COMMAND_SYNTAX;
 512         mutex_lock(mmd_mutex);
 513         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 514         mmd->new_vss_status_flags &= ~VSS_REPOS;
 515         mmd->new_vss_status_flags |= VSS_NEXT;
 516         mutex_unlock(mmd_mutex);
 517         return 1;
 518 }
 519
 520 /* pause */
 521 int com_pause(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 522 {
 523         if (argc != 1)
 524                 return -E_COMMAND_SYNTAX;
 525         mutex_lock(mmd_mutex);
 526         if (!vss_paused() && !vss_stopped()) {
 527                 mmd->events++;
 528                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 529                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 530         }
 531         mutex_unlock(mmd_mutex);
 532         return 1;
 533 }
 534
 535 /* next */
 536 int com_next(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 537 {
 538         if (argc != 1)
 539                 return -E_COMMAND_SYNTAX;
 540         mutex_lock(mmd_mutex);
 541         mmd->events++;
 542         mmd->new_vss_status_flags |= VSS_NEXT;
 543         mutex_unlock(mmd_mutex);
 544         return 1;
 545 }
 546
 547 /* nomore */
 548 int com_nomore(__a_unused struct rc4_context *rc4c, int argc, __a_unused char * const * argv)
 549 {
 550         if (argc != 1)
 551                 return -E_COMMAND_SYNTAX;
 552         mutex_lock(mmd_mutex);
 553         if (vss_playing() || vss_paused())
 554                 mmd->new_vss_status_flags |= VSS_NOMORE;
 555         mutex_unlock(mmd_mutex);
 556         return 1;
 557 }
 558
 559 /* ff */
 560 int com_ff(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 561 {
 562         long promille;
 563         int ret, backwards = 0;
 564         unsigned i;
 565         char c;
 566
 567         if (argc != 2)
 568                 return -E_COMMAND_SYNTAX;
 569         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 570                 return -E_COMMAND_SYNTAX;
 571         if (ret > 1 && c == '-')
 572                 backwards = 1; /* jmp backwards */
 573         mutex_lock(mmd_mutex);
 574         ret = -E_NO_AUDIO_FILE;
 575         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 576                 goto out;
 577         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 578         if (backwards)
 579                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 580         else
 581                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 582         if (promille < 0)
 583                 promille = 0;
 584         if (promille >  1000) {
 585                 mmd->new_vss_status_flags |= VSS_NEXT;
 586                 goto out;
 587         }
 588         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 589         mmd->new_vss_status_flags |= VSS_REPOS;
 590         mmd->new_vss_status_flags &= ~VSS_NEXT;
 591         mmd->events++;
 592         ret = 1;
 593 out:
 594         mutex_unlock(mmd_mutex);
 595         return ret;
 596 }
 597
 598 /* jmp */
 599 int com_jmp(__a_unused struct rc4_context *rc4c, int argc, char * const * argv)
 600 {
 601         long unsigned int i;
 602         int ret;
 603
 604         if (argc != 2)
 605                 return -E_COMMAND_SYNTAX;
 606         if (sscanf(argv[1], "%lu", &i) <= 0)
 607                 return -E_COMMAND_SYNTAX;
 608         mutex_lock(mmd_mutex);
 609         ret = -E_NO_AUDIO_FILE;
 610         if (!mmd->afd.afhi.chunks_total)
 611                 goto out;
 612         if (i > 100)
 613                 i = 100;
 614         PARA_INFO_LOG("jumping to %lu%%\n", i);
 615         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 616         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 617                 mmd->chunks_sent, mmd->offset);
 618         mmd->new_vss_status_flags |= VSS_REPOS;
 619         mmd->new_vss_status_flags &= ~VSS_NEXT;
 620         ret = 1;
 621         mmd->events++;
 622 out:
 623         mutex_unlock(mmd_mutex);
 624         return ret;
 625 }
 626
 627 /*
 628  * check if perms are sufficient to exec a command having perms cmd_perms.
 629  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 630  */
 631 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 632 {
 633         PARA_DEBUG_LOG("checking permissions\n");
 634         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 635 }
 636
 637 /*
 638  * Parse first string from *cmd and lookup in table of valid commands.
 639  * On error, NULL is returned.
 640  */
 641 static struct server_command *parse_cmd(const char *cmdstr)
 642 {
 643         char buf[255];
 644         int n = 0;
 645
 646         sscanf(cmdstr, "%200s%n", buf, &n);
 647         if (!n)
 648                 return NULL;
 649         buf[n] = '\0';
 650         return get_cmd_ptr(buf, NULL);
 651 }
 652
 653 static int read_command(struct rc4_context *rc4c, char **result)
 654 {
 655         int ret;
 656         char buf[4096];
 657         char *command = NULL;
 658
 659         for (;;) {
 660                 size_t numbytes;
 661                 char *p;
 662
 663                 ret = rc4_recv_buffer(rc4c, buf, sizeof(buf));
 664                 if (ret < 0)
 665                         goto out;
 666                 if (!ret)
 667                         break;
 668                 numbytes = ret;
 669                 ret = -E_COMMAND_SYNTAX;
 670                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 671                         goto out;
 672                 command = para_strcat(command, buf);
 673                 p = strstr(command, EOC_MSG);
 674                 if (p) {
 675                         *p = '\0';
 676                         break;
 677                 }
 678         }
 679         ret = command? 1 : -E_COMMAND_SYNTAX;
 680 out:
 681         if (ret < 0)
 682                 free(command);
 683         else
 684                 *result = command;
 685         return ret;
 686
 687 }
 688
 689 static void reset_signals(void)
 690 {
 691         para_sigaction(SIGCHLD, SIG_IGN);
 692         para_sigaction(SIGINT, SIG_DFL);
 693         para_sigaction(SIGTERM, SIG_DFL);
 694         para_sigaction(SIGHUP, SIG_DFL);
 695 }
 696
 697 /**
 698  * Perform user authentication and execute a command.
 699  *
 700  * \param fd The file descriptor to send output to.
 701  * \param peername Identifies the connecting peer.
 702  *
 703  * Whenever para_server accepts an incoming tcp connection on
 704  * the port it listens on, it forks and the resulting child
 705  * calls this function.
 706  *
 707  * An RSA-based challenge/response is used to authenticate
 708  * the peer. It that authentication succeeds, a random RC4
 709  * session key is generated and sent back to the peer,
 710  * encrypted with its RSA public key.  From this point on,
 711  * all transfers are crypted with this session key.
 712  *
 713  * Next it is checked if the peer supplied  a valid server command or a command
 714  * for the audio file selector.  If yes, and if the user has sufficient
 715  * permissions to execute that command, the function calls the corresponding
 716  * command handler which does argument checking and further processing.
 717  *
 718  * In order to cope with a DOS attacks, a timeout is set up
 719  * which terminates the function if the connection was not
 720  * authenticated when the timeout expires.
 721  *
 722  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 723  */
 724 __noreturn void handle_connect(int fd, const char *peername)
 725 {
 726         int ret, argc;
 727         char buf[4096];
 728         unsigned char rand_buf[CHALLENGE_SIZE + 2 * RC4_KEY_LEN];
 729         unsigned char challenge_sha1[HASH_SIZE];
 730         struct user *u;
 731         struct server_command *cmd = NULL;
 732         char **argv = NULL;
 733         char *p, *command = NULL;
 734         size_t numbytes;
 735         struct rc4_context rc4c = {.fd = fd};
 736
 737         reset_signals();
 738         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 739         ret = mark_fd_blocking(fd);
 740         if (ret < 0)
 741                 goto err_out;
 742         /* send Welcome message */
 743         ret = send_va_buffer(fd, "This is para_server, version "
 744                 PACKAGE_VERSION  ".\n" );
 745         if (ret < 0)
 746                 goto err_out;
 747         /* recv auth request line */
 748         ret = recv_buffer(fd, buf, sizeof(buf));
 749         if (ret < 0)
 750                 goto err_out;
 751         if (ret < 10) {
 752                 ret = -E_AUTH_REQUEST;
 753                 goto err_out;
 754         }
 755         numbytes = ret;
 756         ret = -E_AUTH_REQUEST;
 757         if (strncmp(buf, AUTH_REQUEST_MSG, strlen(AUTH_REQUEST_MSG)))
 758                 goto err_out;
 759         p = buf + strlen(AUTH_REQUEST_MSG);
 760         PARA_DEBUG_LOG("received auth request for user %s\n", p);
 761         ret = -E_BAD_USER;
 762         u = lookup_user(p);
 763         if (u) {
 764                 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
 765                 ret = para_encrypt_buffer(u->rsa, rand_buf, sizeof(rand_buf),
 766                         (unsigned char *)buf);
 767                 if (ret < 0)
 768                         goto err_out;
 769                 numbytes = ret;
 770         } else {
 771                 /*
 772                  * We don't want to reveal our user names, so we send a
 773                  * challenge to the client even if the user does not exist, and
 774                  * fail the authentication later.
 775                  */
 776                 numbytes = 256;
 777                 get_random_bytes_or_die((unsigned char *)buf, numbytes);
 778         }
 779         PARA_DEBUG_LOG("sending %zu byte challenge + rc4 keys (%u bytes)\n",
 780                 CHALLENGE_SIZE, numbytes);
 781         ret = send_bin_buffer(fd, buf, numbytes);
 782         if (ret < 0)
 783                 goto net_err;
 784         /* recv challenge response */
 785         ret = recv_bin_buffer(fd, buf, HASH_SIZE);
 786         if (ret < 0)
 787                 goto net_err;
 788         numbytes = ret;
 789         PARA_DEBUG_LOG("received %zu bytes challenge response\n", ret);
 790         ret = -E_BAD_USER;
 791         if (!u)
 792                 goto net_err;
 793         /*
 794          * The correct response is the sha1 of the first CHALLENGE_SIZE bytes
 795          * of the random data.
 796          */
 797         ret = -E_BAD_AUTH;
 798         if (numbytes != HASH_SIZE)
 799                 goto net_err;
 800         sha1_hash((char *)rand_buf, CHALLENGE_SIZE, challenge_sha1);
 801         if (memcmp(challenge_sha1, buf, HASH_SIZE))
 802                 goto net_err;
 803         /* auth successful */
 804         alarm(0);
 805         PARA_INFO_LOG("good auth for %s\n", u->name);
 806         /* init rc4 keys with the second part of the random buffer */
 807         RC4_set_key(&rc4c.recv_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE);
 808         RC4_set_key(&rc4c.send_key, RC4_KEY_LEN, rand_buf + CHALLENGE_SIZE
 809                 + RC4_KEY_LEN);
 810         ret = rc4_send_buffer(&rc4c, PROCEED_MSG);
 811         if (ret < 0)
 812                 goto net_err;
 813         ret = read_command(&rc4c, &command);
 814         if (ret == -E_COMMAND_SYNTAX)
 815                 goto err_out;
 816         if (ret < 0)
 817                 goto net_err;
 818         ret = -E_BAD_CMD;
 819         cmd = parse_cmd(command);
 820         if (!cmd)
 821                 goto err_out;
 822         /* valid command, check permissions */
 823         ret = check_perms(u->perms, cmd);
 824         if (ret < 0)
 825                 goto err_out;
 826         /* valid command and sufficient perms */
 827         argc = split_args(command, &argv, "\n");
 828         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 829                         peername);
 830         ret = cmd->handler(&rc4c, argc, argv);
 831         mutex_lock(mmd_mutex);
 832         mmd->num_commands++;
 833         mutex_unlock(mmd_mutex);
 834         if (ret >= 0)
 835                 goto out;
 836 err_out:
 837         rc4_send_va_buffer(&rc4c, "%s\n", para_strerror(-ret));
 838 net_err:
 839         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 840 out:
 841         free(command);
 842         free(argv);
 843         mutex_lock(mmd_mutex);
 844         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 845                 mmd->events++;
 846         mmd->active_connections--;
 847         mutex_unlock(mmd_mutex);
 848         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 849 }