command.c

   1 /*
   2  * Copyright (C) 1997-2011 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 <regex.h>
  10 #include <signal.h>
  11 #include <sys/time.h>
  12 #include <sys/types.h>
  13 #include <dirent.h>
  14 #include <osl.h>
  15 #include <stdbool.h>
  16
  17 #include "para.h"
  18 #include "error.h"
  19 #include "crypt.h"
  20 #include "command.h"
  21 #include "server.cmdline.h"
  22 #include "string.h"
  23 #include "afh.h"
  24 #include "afs.h"
  25 #include "server.h"
  26 #include "list.h"
  27 #include "send.h"
  28 #include "vss.h"
  29 #include "rc4.h"
  30 #include "net.h"
  31 #include "daemon.h"
  32 #include "fd.h"
  33 #include "ipc.h"
  34 #include "user_list.h"
  35 #include "server_command_list.h"
  36 #include "afs_command_list.h"
  37 #include "sched.h"
  38 #include "signal.h"
  39
  40 /** Commands including options must be shorter than this. */
  41 #define MAX_COMMAND_LEN 32768
  42
  43 extern int mmd_mutex;
  44 extern struct misc_meta_data *mmd;
  45 extern struct sender senders[];
  46 int send_afs_status(struct stream_cipher_context *scc, int parser_friendly);
  47
  48 const char *status_item_list[] = {STATUS_ITEM_ARRAY};
  49
  50 static void dummy(__a_unused int s)
  51 {
  52 }
  53
  54 static void mmd_dup(struct misc_meta_data *new_mmd)
  55 {
  56         mutex_lock(mmd_mutex);
  57         *new_mmd = *mmd;
  58         mutex_unlock(mmd_mutex);
  59 }
  60
  61 /*
  62  * Compute human readable string containing vss status for given integer value.
  63  *
  64  * We don't want to use vss_playing() and friends here because we take a
  65  * snapshot of the mmd struct and use the copy for computing the state of the
  66  * vss. If the real data were used, we would take the mmd lock for a rather
  67  * long time or risk to get an inconsistent view.
  68  */
  69 static char *vss_status_tohuman(unsigned int flags)
  70 {
  71         if (flags & VSS_PLAYING)
  72                 return para_strdup("playing");
  73         if (flags & VSS_NEXT)
  74                 return para_strdup("stopped");
  75         return para_strdup("paused");
  76 }
  77
  78 /*
  79  * return human readable permission string. Never returns NULL.
  80  */
  81 static char *cmd_perms_itohuman(unsigned int perms)
  82 {
  83         char *msg = para_malloc(5 * sizeof(char));
  84
  85         msg[0] = perms & AFS_READ? 'a' : '-';
  86         msg[1] = perms & AFS_WRITE? 'A' : '-';
  87         msg[2] = perms & VSS_READ? 'v' : '-';
  88         msg[3] = perms & VSS_WRITE? 'V' : '-';
  89         msg[4] = '\0';
  90         return msg;
  91 }
  92
  93 /*
  94  * Never returns NULL.
  95  */
  96 static char *vss_get_status_flags(unsigned int flags)
  97 {
  98         char *msg = para_malloc(5 * sizeof(char));
  99
 100         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
 101         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
 102         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 103         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 104         msg[4] = '\0';
 105         return msg;
 106 }
 107
 108 static char *get_status(struct misc_meta_data *nmmd, int parser_friendly)
 109 {
 110         char mtime[30] = "";
 111         char *status, *flags; /* vss status info */
 112         char *ut = uptime_str();
 113         long offset = (nmmd->offset + 500) / 1000;
 114         struct timeval current_time;
 115         struct tm mtime_tm;
 116         struct para_buffer b = {.flags = parser_friendly? PBF_SIZE_PREFIX : 0};
 117
 118         /* report real status */
 119         status = vss_status_tohuman(nmmd->vss_status_flags);
 120         flags = vss_get_status_flags(nmmd->vss_status_flags);
 121         if (nmmd->size) { /* parent currently has an audio file open */
 122                 localtime_r(&nmmd->mtime, &mtime_tm);
 123                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 124         }
 125         gettimeofday(&current_time, NULL);
 126         WRITE_STATUS_ITEM(&b, SI_FILE_SIZE, "%zu\n", nmmd->size / 1024);
 127         WRITE_STATUS_ITEM(&b, SI_MTIME, "%s\n", mtime);
 128         WRITE_STATUS_ITEM(&b, SI_STATUS, "%s\n", status);
 129         WRITE_STATUS_ITEM(&b, SI_STATUS_FLAGS, "%s\n", flags);
 130         WRITE_STATUS_ITEM(&b, SI_OFFSET, "%li\n", offset);
 131         WRITE_STATUS_ITEM(&b, SI_AFS_MODE, "%s\n", mmd->afs_mode_string);
 132         WRITE_STATUS_ITEM(&b, SI_STREAM_START, "%lu.%lu\n",
 133                 (long unsigned)nmmd->stream_start.tv_sec,
 134                 (long unsigned)nmmd->stream_start.tv_usec);
 135         WRITE_STATUS_ITEM(&b, SI_CURRENT_TIME, "%lu.%lu\n",
 136                 (long unsigned)current_time.tv_sec,
 137                 (long unsigned)current_time.tv_usec);
 138         free(flags);
 139         free(status);
 140         free(ut);
 141         return b.buf;
 142 }
 143
 144 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 145 {
 146         int i;
 147         /* this has to match sender.h */
 148         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 149
 150         scd->sender_num = -1;
 151         if (argc < 2)
 152                 return -E_COMMAND_SYNTAX;
 153         for (i = 0; senders[i].name; i++)
 154                 if (!strcmp(senders[i].name, argv[1]))
 155                         break;
 156         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 157         if (!senders[i].name)
 158                 return -E_COMMAND_SYNTAX;
 159         scd->sender_num = i;
 160         for (i = 0; subcmds[i]; i++)
 161                 if (!strcmp(subcmds[i], argv[2]))
 162                         break;
 163         if (!subcmds[i])
 164                 return -E_COMMAND_SYNTAX;
 165         scd->cmd_num = i;
 166         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 167                 return -E_SENDER_CMD;
 168         switch (scd->cmd_num) {
 169         case SENDER_ON:
 170         case SENDER_OFF:
 171                 if (argc != 3)
 172                         return -E_COMMAND_SYNTAX;
 173                 break;
 174         case SENDER_DENY:
 175         case SENDER_ALLOW:
 176                 if (argc != 4 || parse_cidr(argv[3], scd->host,
 177                                 sizeof(scd->host), &scd->netmask) == NULL)
 178                         return -E_COMMAND_SYNTAX;
 179                 break;
 180         case SENDER_ADD:
 181         case SENDER_DELETE:
 182                 if (argc != 4)
 183                         return -E_COMMAND_SYNTAX;
 184                 return parse_fec_url(argv[3], scd);
 185         default:
 186                 return -E_COMMAND_SYNTAX;
 187         }
 188         return 1;
 189 }
 190
 191 int com_sender(struct stream_cipher_context *scc, int argc, char * const * argv)
 192 {
 193         int i, ret;
 194         char *msg = NULL;
 195         struct sender_command_data scd;
 196
 197         if (argc < 2) {
 198                 for (i = 0; senders[i].name; i++) {
 199                         char *tmp = make_message("%s%s\n",
 200                                 msg? msg : "", senders[i].name);
 201                         free(msg);
 202                         msg = tmp;
 203                 }
 204                 ret = sc_send_buffer(scc, msg);
 205                 free(msg);
 206                 return ret;
 207         }
 208         ret = check_sender_args(argc, argv, &scd);
 209         if (ret < 0) {
 210                 if (scd.sender_num < 0)
 211                         return ret;
 212                 msg = senders[scd.sender_num].help();
 213                 ret = sc_send_buffer(scc, msg);
 214                 free(msg);
 215                 return ret;
 216         }
 217
 218         switch (scd.cmd_num) {
 219         case SENDER_ADD:
 220         case SENDER_DELETE:
 221                 assert(senders[scd.sender_num].resolve_target);
 222                 ret = senders[scd.sender_num].resolve_target(argv[3], &scd);
 223                 if (ret < 0)
 224                         return ret;
 225         }
 226
 227         for (i = 0; i < 10; i++) {
 228                 mutex_lock(mmd_mutex);
 229                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 230                         mutex_unlock(mmd_mutex);
 231                         usleep(100 * 1000);
 232                         continue;
 233                 }
 234                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 235                 mutex_unlock(mmd_mutex);
 236                 break;
 237         }
 238         return (i < 10)? 1 : -E_LOCK;
 239 }
 240
 241 /* server info */
 242 int com_si(struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 243 {
 244         int i, ret;
 245         char *ut;
 246         char *sender_info = NULL;
 247
 248         if (argc != 1)
 249                 return -E_COMMAND_SYNTAX;
 250         mutex_lock(mmd_mutex);
 251         for (i = 0; senders[i].name; i++) {
 252                 char *info = senders[i].info();
 253                 sender_info = para_strcat(sender_info, info);
 254                 free(info);
 255         }
 256         ut = uptime_str();
 257         ret = sc_send_va_buffer(scc, "version: " GIT_VERSION "\n"
 258                 "up: %s\nplayed: %u\n"
 259                 "server_pid: %d\n"
 260                 "afs_pid: %d\n"
 261                 "connections (active/accepted/total): %u/%u/%u\n"
 262                 "current loglevel: %s\n"
 263                 "supported audio formats: %s\n"
 264                 "%s",
 265                 ut, mmd->num_played,
 266                 (int)getppid(),
 267                 (int)mmd->afs_pid,
 268                 mmd->active_connections,
 269                 mmd->num_commands,
 270                 mmd->num_connects,
 271                 conf.loglevel_arg,
 272                 SERVER_AUDIO_FORMATS,
 273                 sender_info
 274         );
 275         mutex_unlock(mmd_mutex);
 276         free(ut);
 277         free(sender_info);
 278         return ret;
 279 }
 280
 281 /* version */
 282 int com_version(struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 283 {
 284         if (argc != 1)
 285                 return -E_COMMAND_SYNTAX;
 286         return sc_send_buffer(scc, VERSION_TEXT("server")
 287                 "built: " BUILD_DATE "\n"
 288                 UNAME_RS ", " CC_VERSION "\n"
 289         );
 290 }
 291
 292 #define EMPTY_STATUS_ITEMS \
 293         ITEM(PATH) \
 294         ITEM(DIRECTORY) \
 295         ITEM(BASENAME) \
 296         ITEM(SCORE) \
 297         ITEM(ATTRIBUTES_BITMAP) \
 298         ITEM(ATTRIBUTES_TXT) \
 299         ITEM(HASH) \
 300         ITEM(IMAGE_ID) \
 301         ITEM(IMAGE_NAME) \
 302         ITEM(LYRICS_ID) \
 303         ITEM(LYRICS_NAME) \
 304         ITEM(BITRATE) \
 305         ITEM(FORMAT) \
 306         ITEM(FREQUENCY) \
 307         ITEM(CHANNELS) \
 308         ITEM(DURATION) \
 309         ITEM(SECONDS_TOTAL) \
 310         ITEM(NUM_PLAYED) \
 311         ITEM(LAST_PLAYED) \
 312         ITEM(TECHINFO) \
 313         ITEM(ARTIST) \
 314         ITEM(TITLE) \
 315         ITEM(YEAR) \
 316         ITEM(ALBUM) \
 317         ITEM(COMMENT) \
 318         ITEM(AMPLIFICATION)
 319
 320 /**
 321  * Write a list of audio-file related status items with empty values.
 322  *
 323  * This is used by vss when currently no audio file is open.
 324  */
 325 static char *empty_status_items(int parser_friendly)
 326 {
 327         if (parser_friendly)
 328                 return make_message(
 329                         #define ITEM(x) "0004 %02x:\n"
 330                         EMPTY_STATUS_ITEMS
 331                         #undef ITEM
 332                         #define ITEM(x) , SI_ ## x
 333                         EMPTY_STATUS_ITEMS
 334                         #undef ITEM
 335                 );
 336         return make_message(
 337                 #define ITEM(x) "%s:\n"
 338                 EMPTY_STATUS_ITEMS
 339                 #undef ITEM
 340                 #define ITEM(x) ,status_item_list[SI_ ## x]
 341                 EMPTY_STATUS_ITEMS
 342                 #undef ITEM
 343         );
 344 }
 345 #undef EMPTY_STATUS_ITEMS
 346
 347 /* stat */
 348 int com_stat(struct stream_cipher_context *scc, int argc, char * const * argv)
 349 {
 350         int i, ret;
 351         struct misc_meta_data tmp, *nmmd = &tmp;
 352         char *s;
 353         int32_t num = 0;
 354         int parser_friendly = 0;
 355
 356         para_sigaction(SIGUSR1, dummy);
 357
 358         for (i = 1; i < argc; i++) {
 359                 const char *arg = argv[i];
 360                 if (arg[0] != '-')
 361                         break;
 362                 if (!strcmp(arg, "--")) {
 363                         i++;
 364                         break;
 365                 }
 366                 if (!strncmp(arg, "-n=", 3)) {
 367                         ret = para_atoi32(arg + 3, &num);
 368                         if (ret < 0)
 369                                 return ret;
 370                         continue;
 371                 }
 372                 if (!strcmp(arg, "-p")) {
 373                         parser_friendly = 1;
 374                         continue;
 375                 }
 376                 return -E_COMMAND_SYNTAX;
 377         }
 378         if (i != argc)
 379                 return -E_COMMAND_SYNTAX;
 380         for (;;) {
 381                 mmd_dup(nmmd);
 382                 s = get_status(nmmd, parser_friendly);
 383                 ret = sc_send_buffer(scc, s);
 384                 free(s);
 385                 if (ret < 0)
 386                         goto out;
 387                 if (nmmd->vss_status_flags & VSS_NEXT) {
 388                         static char *esi;
 389                         if (!esi)
 390                                 esi = empty_status_items(parser_friendly);
 391                         ret = sc_send_buffer(scc, esi);
 392                         if (ret < 0)
 393                                 goto out;
 394                 } else
 395                         send_afs_status(scc, parser_friendly);
 396                 ret = 1;
 397                 if (num > 0 && !--num)
 398                         goto out;
 399                 sleep(50);
 400                 if (getppid() == 1)
 401                         return -E_SERVER_CRASH;
 402         }
 403 out:
 404         return ret;
 405 }
 406
 407 static int send_list_of_commands(struct stream_cipher_context *scc, struct server_command *cmd,
 408                 const char *handler)
 409 {
 410         int ret, i;
 411
 412         for (i = 1; cmd->name; cmd++, i++) {
 413                 char *perms = cmd_perms_itohuman(cmd->perms);
 414                 ret = sc_send_va_buffer(scc, "%s\t%s\t%s\t%s\n", cmd->name,
 415                         handler,
 416                         perms,
 417                         cmd->description);
 418                 free(perms);
 419                 if (ret < 0)
 420                         return ret;
 421         }
 422         return 1;
 423 }
 424
 425 /* returns string that must be freed by the caller */
 426 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 427 {
 428         struct server_command *cmd;
 429
 430         for (cmd = server_cmds; cmd->name; cmd++)
 431                 if (!strcmp(cmd->name, name)) {
 432                         if (handler)
 433                                 *handler = para_strdup("server"); /* server commands */
 434                         return cmd;
 435                 }
 436         /* not found, look for commands supported by afs */
 437         for (cmd = afs_cmds; cmd->name; cmd++)
 438                 if (!strcmp(cmd->name, name)) {
 439                         if (handler)
 440                                 *handler = para_strdup("afs");
 441                         return cmd;
 442                 }
 443         return NULL;
 444 }
 445
 446 /* help */
 447 int com_help(struct stream_cipher_context *scc, int argc, char * const * argv)
 448 {
 449         struct server_command *cmd;
 450         char *perms, *handler;
 451         int ret;
 452
 453         if (argc < 2) {
 454                 /* no argument given, print list of commands */
 455                 if ((ret = send_list_of_commands(scc, server_cmds, "server")) < 0)
 456                         return ret;
 457                 return send_list_of_commands(scc, afs_cmds, "afs");
 458         }
 459         /* argument given for help */
 460         cmd = get_cmd_ptr(argv[1], &handler);
 461         if (!cmd)
 462                 return -E_BAD_CMD;
 463         perms = cmd_perms_itohuman(cmd->perms);
 464         ret = sc_send_va_buffer(scc,
 465                 "%s - %s\n\n"
 466                 "handler: %s\n"
 467                 "permissions: %s\n"
 468                 "usage: %s\n\n"
 469                 "%s\n",
 470                 argv[1],
 471                 cmd->description,
 472                 handler,
 473                 perms,
 474                 cmd->usage,
 475                 cmd->help
 476         );
 477         free(perms);
 478         free(handler);
 479         return ret;
 480 }
 481
 482 /* hup */
 483 int com_hup(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 484 {
 485         if (argc != 1)
 486                 return -E_COMMAND_SYNTAX;
 487         kill(getppid(), SIGHUP);
 488         return 1;
 489 }
 490
 491 /* term */
 492 int com_term(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 493 {
 494         if (argc != 1)
 495                 return -E_COMMAND_SYNTAX;
 496         kill(getppid(), SIGTERM);
 497         return 1;
 498 }
 499
 500 int com_play(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 501 {
 502         if (argc != 1)
 503                 return -E_COMMAND_SYNTAX;
 504         mutex_lock(mmd_mutex);
 505         mmd->new_vss_status_flags |= VSS_PLAYING;
 506         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 507         mutex_unlock(mmd_mutex);
 508         return 1;
 509
 510 }
 511
 512 /* stop */
 513 int com_stop(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 514 {
 515         if (argc != 1)
 516                 return -E_COMMAND_SYNTAX;
 517         mutex_lock(mmd_mutex);
 518         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 519         mmd->new_vss_status_flags &= ~VSS_REPOS;
 520         mmd->new_vss_status_flags |= VSS_NEXT;
 521         mutex_unlock(mmd_mutex);
 522         return 1;
 523 }
 524
 525 /* pause */
 526 int com_pause(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 527 {
 528         if (argc != 1)
 529                 return -E_COMMAND_SYNTAX;
 530         mutex_lock(mmd_mutex);
 531         if (!vss_paused() && !vss_stopped()) {
 532                 mmd->events++;
 533                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 534                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 535         }
 536         mutex_unlock(mmd_mutex);
 537         return 1;
 538 }
 539
 540 /* next */
 541 int com_next(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 542 {
 543         if (argc != 1)
 544                 return -E_COMMAND_SYNTAX;
 545         mutex_lock(mmd_mutex);
 546         mmd->events++;
 547         mmd->new_vss_status_flags |= VSS_NEXT;
 548         mutex_unlock(mmd_mutex);
 549         return 1;
 550 }
 551
 552 /* nomore */
 553 int com_nomore(__a_unused struct stream_cipher_context *scc, int argc, __a_unused char * const * argv)
 554 {
 555         if (argc != 1)
 556                 return -E_COMMAND_SYNTAX;
 557         mutex_lock(mmd_mutex);
 558         if (vss_playing() || vss_paused())
 559                 mmd->new_vss_status_flags |= VSS_NOMORE;
 560         mutex_unlock(mmd_mutex);
 561         return 1;
 562 }
 563
 564 /* ff */
 565 int com_ff(__a_unused struct stream_cipher_context *scc, int argc, char * const * argv)
 566 {
 567         long promille;
 568         int ret, backwards = 0;
 569         unsigned i;
 570         char c;
 571
 572         if (argc != 2)
 573                 return -E_COMMAND_SYNTAX;
 574         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 575                 return -E_COMMAND_SYNTAX;
 576         if (ret > 1 && c == '-')
 577                 backwards = 1; /* jmp backwards */
 578         mutex_lock(mmd_mutex);
 579         ret = -E_NO_AUDIO_FILE;
 580         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 581                 goto out;
 582         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 583         if (backwards)
 584                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 585         else
 586                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 587         if (promille < 0)
 588                 promille = 0;
 589         if (promille >  1000) {
 590                 mmd->new_vss_status_flags |= VSS_NEXT;
 591                 goto out;
 592         }
 593         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 594         mmd->new_vss_status_flags |= VSS_REPOS;
 595         mmd->new_vss_status_flags &= ~VSS_NEXT;
 596         mmd->events++;
 597         ret = 1;
 598 out:
 599         mutex_unlock(mmd_mutex);
 600         return ret;
 601 }
 602
 603 /* jmp */
 604 int com_jmp(__a_unused struct stream_cipher_context *scc, int argc, char * const * argv)
 605 {
 606         long unsigned int i;
 607         int ret;
 608
 609         if (argc != 2)
 610                 return -E_COMMAND_SYNTAX;
 611         if (sscanf(argv[1], "%lu", &i) <= 0)
 612                 return -E_COMMAND_SYNTAX;
 613         mutex_lock(mmd_mutex);
 614         ret = -E_NO_AUDIO_FILE;
 615         if (!mmd->afd.afhi.chunks_total)
 616                 goto out;
 617         if (i > 100)
 618                 i = 100;
 619         PARA_INFO_LOG("jumping to %lu%%\n", i);
 620         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 621         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 622                 mmd->chunks_sent, mmd->offset);
 623         mmd->new_vss_status_flags |= VSS_REPOS;
 624         mmd->new_vss_status_flags &= ~VSS_NEXT;
 625         ret = 1;
 626         mmd->events++;
 627 out:
 628         mutex_unlock(mmd_mutex);
 629         return ret;
 630 }
 631
 632 /*
 633  * check if perms are sufficient to exec a command having perms cmd_perms.
 634  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 635  */
 636 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 637 {
 638         PARA_DEBUG_LOG("checking permissions\n");
 639         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 640 }
 641
 642 /*
 643  * Parse first string from *cmd and lookup in table of valid commands.
 644  * On error, NULL is returned.
 645  */
 646 static struct server_command *parse_cmd(const char *cmdstr)
 647 {
 648         char buf[255];
 649         int n = 0;
 650
 651         sscanf(cmdstr, "%200s%n", buf, &n);
 652         if (!n)
 653                 return NULL;
 654         buf[n] = '\0';
 655         return get_cmd_ptr(buf, NULL);
 656 }
 657
 658 static int read_command(struct stream_cipher_context *scc, char **result)
 659 {
 660         int ret;
 661         char buf[4096];
 662         char *command = NULL;
 663
 664         for (;;) {
 665                 size_t numbytes;
 666                 char *p;
 667
 668                 ret = sc_recv_buffer(scc, buf, sizeof(buf));
 669                 if (ret < 0)
 670                         goto out;
 671                 if (!ret)
 672                         break;
 673                 numbytes = ret;
 674                 ret = -E_COMMAND_SYNTAX;
 675                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 676                         goto out;
 677                 command = para_strcat(command, buf);
 678                 p = strstr(command, EOC_MSG);
 679                 if (p) {
 680                         *p = '\0';
 681                         break;
 682                 }
 683         }
 684         ret = command? 1 : -E_COMMAND_SYNTAX;
 685 out:
 686         if (ret < 0)
 687                 free(command);
 688         else
 689                 *result = command;
 690         return ret;
 691
 692 }
 693
 694 static void reset_signals(void)
 695 {
 696         para_sigaction(SIGCHLD, SIG_IGN);
 697         para_sigaction(SIGINT, SIG_DFL);
 698         para_sigaction(SIGTERM, SIG_DFL);
 699         para_sigaction(SIGHUP, SIG_DFL);
 700 }
 701
 702 /**
 703  * Perform user authentication and execute a command.
 704  *
 705  * \param fd The file descriptor to send output to.
 706  * \param peername Identifies the connecting peer.
 707  *
 708  * Whenever para_server accepts an incoming tcp connection on
 709  * the port it listens on, it forks and the resulting child
 710  * calls this function.
 711  *
 712  * An RSA-based challenge/response is used to authenticate
 713  * the peer. It that authentication succeeds, a random RC4
 714  * session key is generated and sent back to the peer,
 715  * encrypted with its RSA public key.  From this point on,
 716  * all transfers are crypted with this session key.
 717  *
 718  * Next it is checked if the peer supplied  a valid server command or a command
 719  * for the audio file selector.  If yes, and if the user has sufficient
 720  * permissions to execute that command, the function calls the corresponding
 721  * command handler which does argument checking and further processing.
 722  *
 723  * In order to cope with a DOS attacks, a timeout is set up
 724  * which terminates the function if the connection was not
 725  * authenticated when the timeout expires.
 726  *
 727  * \sa alarm(2), crypt.c, crypt.h
 728  */
 729 __noreturn void handle_connect(int fd, const char *peername)
 730 {
 731         int ret, argc;
 732         char buf[4096];
 733         unsigned char rand_buf[CHALLENGE_SIZE + 2 * RC4_KEY_LEN];
 734         unsigned char challenge_sha1[HASH_SIZE];
 735         struct user *u;
 736         struct server_command *cmd = NULL;
 737         char **argv = NULL;
 738         char *p, *command = NULL;
 739         size_t numbytes;
 740         struct stream_cipher_context scc = {.fd = fd};
 741
 742         reset_signals();
 743         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 744         ret = mark_fd_blocking(fd);
 745         if (ret < 0)
 746                 goto net_err;
 747         /* send Welcome message */
 748         ret = send_va_buffer(fd, "This is para_server, version "
 749                 PACKAGE_VERSION  ".\n" );
 750         if (ret < 0)
 751                 goto net_err;
 752         /* recv auth request line */
 753         ret = recv_buffer(fd, buf, sizeof(buf));
 754         if (ret < 0)
 755                 goto net_err;
 756         if (ret < 10) {
 757                 ret = -E_AUTH_REQUEST;
 758                 goto net_err;
 759         }
 760         numbytes = ret;
 761         ret = -E_AUTH_REQUEST;
 762         if (strncmp(buf, AUTH_REQUEST_MSG, strlen(AUTH_REQUEST_MSG)))
 763                 goto net_err;
 764         p = buf + strlen(AUTH_REQUEST_MSG);
 765         PARA_DEBUG_LOG("received auth request for user %s\n", p);
 766         ret = -E_BAD_USER;
 767         u = lookup_user(p);
 768         if (u) {
 769                 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
 770                 ret = pub_encrypt(u->pubkey, rand_buf, sizeof(rand_buf),
 771                         (unsigned char *)buf);
 772                 if (ret < 0)
 773                         goto net_err;
 774                 numbytes = ret;
 775         } else {
 776                 /*
 777                  * We don't want to reveal our user names, so we send a
 778                  * challenge to the client even if the user does not exist, and
 779                  * fail the authentication later.
 780                  */
 781                 numbytes = 256;
 782                 get_random_bytes_or_die((unsigned char *)buf, numbytes);
 783         }
 784         PARA_DEBUG_LOG("sending %u byte challenge + rc4 keys (%zu bytes)\n",
 785                 CHALLENGE_SIZE, numbytes);
 786         ret = send_bin_buffer(fd, buf, numbytes);
 787         if (ret < 0)
 788                 goto net_err;
 789         /* recv challenge response */
 790         ret = recv_bin_buffer(fd, buf, HASH_SIZE);
 791         if (ret < 0)
 792                 goto net_err;
 793         numbytes = ret;
 794         PARA_DEBUG_LOG("received %d bytes challenge response\n", ret);
 795         ret = -E_BAD_USER;
 796         if (!u)
 797                 goto net_err;
 798         /*
 799          * The correct response is the sha1 of the first CHALLENGE_SIZE bytes
 800          * of the random data.
 801          */
 802         ret = -E_BAD_AUTH;
 803         if (numbytes != HASH_SIZE)
 804                 goto net_err;
 805         sha1_hash((char *)rand_buf, CHALLENGE_SIZE, challenge_sha1);
 806         if (memcmp(challenge_sha1, buf, HASH_SIZE))
 807                 goto net_err;
 808         /* auth successful */
 809         alarm(0);
 810         PARA_INFO_LOG("good auth for %s\n", u->name);
 811         /* init stream cipher keys with the second part of the random buffer */
 812         scc.recv = sc_new(rand_buf + CHALLENGE_SIZE, RC4_KEY_LEN);
 813         scc.send = sc_new(rand_buf + CHALLENGE_SIZE + RC4_KEY_LEN, RC4_KEY_LEN);
 814         ret = sc_send_buffer(&scc, PROCEED_MSG);
 815         if (ret < 0)
 816                 goto net_err;
 817         ret = read_command(&scc, &command);
 818         if (ret == -E_COMMAND_SYNTAX)
 819                 goto err_out;
 820         if (ret < 0)
 821                 goto net_err;
 822         ret = -E_BAD_CMD;
 823         cmd = parse_cmd(command);
 824         if (!cmd)
 825                 goto err_out;
 826         /* valid command, check permissions */
 827         ret = check_perms(u->perms, cmd);
 828         if (ret < 0)
 829                 goto err_out;
 830         /* valid command and sufficient perms */
 831         ret = create_argv(command, "\n", &argv);
 832         if (ret < 0)
 833                 goto err_out;
 834         argc = ret;
 835         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 836                         peername);
 837         ret = cmd->handler(&scc, argc, argv);
 838         free_argv(argv);
 839         mutex_lock(mmd_mutex);
 840         mmd->num_commands++;
 841         mutex_unlock(mmd_mutex);
 842         if (ret >= 0)
 843                 goto out;
 844 err_out:
 845         sc_send_va_buffer(&scc, "%s\n", para_strerror(-ret));
 846 net_err:
 847         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 848 out:
 849         free(command);
 850         sc_free(scc.recv);
 851         sc_free(scc.send);
 852         mutex_lock(mmd_mutex);
 853         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 854                 mmd->events++;
 855         mmd->active_connections--;
 856         mutex_unlock(mmd_mutex);
 857         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 858 }