command.c

   1 /*
   2  * Copyright (C) 1997-2012 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 <osl.h>
  14
  15 #include "para.h"
  16 #include "error.h"
  17 #include "crypt.h"
  18 #include "command.h"
  19 #include "server.cmdline.h"
  20 #include "string.h"
  21 #include "afh.h"
  22 #include "afs.h"
  23 #include "server.h"
  24 #include "list.h"
  25 #include "send.h"
  26 #include "sched.h"
  27 #include "vss.h"
  28 #include "net.h"
  29 #include "daemon.h"
  30 #include "fd.h"
  31 #include "ipc.h"
  32 #include "user_list.h"
  33 #include "server_command_list.h"
  34 #include "afs_command_list.h"
  35 #include "signal.h"
  36 #include "version.h"
  37
  38 /** Commands including options must be shorter than this. */
  39 #define MAX_COMMAND_LEN 32768
  40
  41 extern int mmd_mutex;
  42 extern struct misc_meta_data *mmd;
  43 extern struct sender senders[];
  44 int send_afs_status(struct command_context *cc, int parser_friendly);
  45
  46 const char *status_item_list[] = {STATUS_ITEM_ARRAY};
  47
  48 static void dummy(__a_unused int s)
  49 {
  50 }
  51
  52 static void mmd_dup(struct misc_meta_data *new_mmd)
  53 {
  54         mutex_lock(mmd_mutex);
  55         *new_mmd = *mmd;
  56         mutex_unlock(mmd_mutex);
  57 }
  58
  59 /*
  60  * Compute human readable string containing vss status for given integer value.
  61  *
  62  * We don't want to use vss_playing() and friends here because we take a
  63  * snapshot of the mmd struct and use the copy for computing the state of the
  64  * vss. If the real data were used, we would take the mmd lock for a rather
  65  * long time or risk to get an inconsistent view.
  66  */
  67 static char *vss_status_tohuman(unsigned int flags)
  68 {
  69         if (flags & VSS_PLAYING)
  70                 return para_strdup("playing");
  71         if (flags & VSS_NEXT)
  72                 return para_strdup("stopped");
  73         return para_strdup("paused");
  74 }
  75
  76 /*
  77  * return human readable permission string. Never returns NULL.
  78  */
  79 static char *cmd_perms_itohuman(unsigned int perms)
  80 {
  81         char *msg = para_malloc(5 * sizeof(char));
  82
  83         msg[0] = perms & AFS_READ? 'a' : '-';
  84         msg[1] = perms & AFS_WRITE? 'A' : '-';
  85         msg[2] = perms & VSS_READ? 'v' : '-';
  86         msg[3] = perms & VSS_WRITE? 'V' : '-';
  87         msg[4] = '\0';
  88         return msg;
  89 }
  90
  91 /*
  92  * Never returns NULL.
  93  */
  94 static char *vss_get_status_flags(unsigned int flags)
  95 {
  96         char *msg = para_malloc(5 * sizeof(char));
  97
  98         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  99         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
 100         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 101         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 102         msg[4] = '\0';
 103         return msg;
 104 }
 105
 106 static char *get_status(struct misc_meta_data *nmmd, int parser_friendly)
 107 {
 108         char mtime[30] = "";
 109         char *status, *flags; /* vss status info */
 110         /* nobody updates our version of "now" */
 111         char *ut = get_server_uptime_str(NULL);
 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         /*
 126          * The calls to WRITE_STATUS_ITEM() below never fail because
 127          * b->max_size is zero (unlimited), see para_printf(). However, clang
 128          * is not smart enough to prove this and complains nevertheless.
 129          * Casting the return value to void silences clang.
 130          */
 131         (void)WRITE_STATUS_ITEM(&b, SI_FILE_SIZE, "%zu\n", nmmd->size / 1024);
 132         (void)WRITE_STATUS_ITEM(&b, SI_MTIME, "%s\n", mtime);
 133         (void)WRITE_STATUS_ITEM(&b, SI_STATUS, "%s\n", status);
 134         (void)WRITE_STATUS_ITEM(&b, SI_STATUS_FLAGS, "%s\n", flags);
 135         (void)WRITE_STATUS_ITEM(&b, SI_OFFSET, "%li\n", offset);
 136         (void)WRITE_STATUS_ITEM(&b, SI_AFS_MODE, "%s\n", mmd->afs_mode_string);
 137         (void)WRITE_STATUS_ITEM(&b, SI_STREAM_START, "%lu.%lu\n",
 138                 (long unsigned)nmmd->stream_start.tv_sec,
 139                 (long unsigned)nmmd->stream_start.tv_usec);
 140         (void)WRITE_STATUS_ITEM(&b, SI_CURRENT_TIME, "%lu.%lu\n",
 141                 (long unsigned)current_time.tv_sec,
 142                 (long unsigned)current_time.tv_usec);
 143         free(flags);
 144         free(status);
 145         free(ut);
 146         return b.buf;
 147 }
 148
 149 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 150 {
 151         int i;
 152         /* this has to match sender.h */
 153         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 154
 155         scd->sender_num = -1;
 156         if (argc < 2)
 157                 return -E_COMMAND_SYNTAX;
 158         for (i = 0; senders[i].name; i++)
 159                 if (!strcmp(senders[i].name, argv[1]))
 160                         break;
 161         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 162         if (!senders[i].name)
 163                 return -E_COMMAND_SYNTAX;
 164         scd->sender_num = i;
 165         for (i = 0; subcmds[i]; i++)
 166                 if (!strcmp(subcmds[i], argv[2]))
 167                         break;
 168         if (!subcmds[i])
 169                 return -E_COMMAND_SYNTAX;
 170         scd->cmd_num = i;
 171         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 172                 return -E_SENDER_CMD;
 173         switch (scd->cmd_num) {
 174         case SENDER_ON:
 175         case SENDER_OFF:
 176                 if (argc != 3)
 177                         return -E_COMMAND_SYNTAX;
 178                 break;
 179         case SENDER_DENY:
 180         case SENDER_ALLOW:
 181                 if (argc != 4 || parse_cidr(argv[3], scd->host,
 182                                 sizeof(scd->host), &scd->netmask) == NULL)
 183                         return -E_COMMAND_SYNTAX;
 184                 break;
 185         case SENDER_ADD:
 186         case SENDER_DELETE:
 187                 if (argc != 4)
 188                         return -E_COMMAND_SYNTAX;
 189                 return parse_fec_url(argv[3], scd);
 190         default:
 191                 return -E_COMMAND_SYNTAX;
 192         }
 193         return 1;
 194 }
 195
 196 int com_sender(struct command_context *cc)
 197 {
 198         int i, ret;
 199         char *msg = NULL;
 200         struct sender_command_data scd;
 201
 202         if (cc->argc < 2) {
 203                 for (i = 0; senders[i].name; i++) {
 204                         char *tmp = make_message("%s%s\n",
 205                                 msg? msg : "", senders[i].name);
 206                         free(msg);
 207                         msg = tmp;
 208                 }
 209                 ret = sc_send_buffer(&cc->scc, msg);
 210                 free(msg);
 211                 return ret;
 212         }
 213         ret = check_sender_args(cc->argc, cc->argv, &scd);
 214         if (ret < 0) {
 215                 if (scd.sender_num < 0)
 216                         return ret;
 217                 msg = senders[scd.sender_num].help();
 218                 ret = sc_send_buffer(&cc->scc, msg);
 219                 free(msg);
 220                 return ret;
 221         }
 222
 223         switch (scd.cmd_num) {
 224         case SENDER_ADD:
 225         case SENDER_DELETE:
 226                 assert(senders[scd.sender_num].resolve_target);
 227                 ret = senders[scd.sender_num].resolve_target(cc->argv[3], &scd);
 228                 if (ret < 0)
 229                         return ret;
 230         }
 231
 232         for (i = 0; i < 10; i++) {
 233                 mutex_lock(mmd_mutex);
 234                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 235                         mutex_unlock(mmd_mutex);
 236                         usleep(100 * 1000);
 237                         continue;
 238                 }
 239                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 240                 mutex_unlock(mmd_mutex);
 241                 break;
 242         }
 243         return (i < 10)? 1 : -E_LOCK;
 244 }
 245
 246 /* server info */
 247 int com_si(struct command_context *cc)
 248 {
 249         int i, ret;
 250         char *ut;
 251         char *sender_info = NULL;
 252
 253         if (cc->argc != 1)
 254                 return -E_COMMAND_SYNTAX;
 255         mutex_lock(mmd_mutex);
 256         for (i = 0; senders[i].name; i++) {
 257                 char *info = senders[i].info();
 258                 sender_info = para_strcat(sender_info, info);
 259                 free(info);
 260         }
 261         ut = get_server_uptime_str(now);
 262         ret = sc_send_va_buffer(&cc->scc, "version: " GIT_VERSION "\n"
 263                 "up: %s\nplayed: %u\n"
 264                 "server_pid: %d\n"
 265                 "afs_pid: %d\n"
 266                 "connections (active/accepted/total): %u/%u/%u\n"
 267                 "current loglevel: %s\n"
 268                 "supported audio formats: %s\n"
 269                 "%s",
 270                 ut, mmd->num_played,
 271                 (int)getppid(),
 272                 (int)mmd->afs_pid,
 273                 mmd->active_connections,
 274                 mmd->num_commands,
 275                 mmd->num_connects,
 276                 conf.loglevel_arg,
 277                 SERVER_AUDIO_FORMATS,
 278                 sender_info
 279         );
 280         mutex_unlock(mmd_mutex);
 281         free(ut);
 282         free(sender_info);
 283         return ret;
 284 }
 285
 286 /* version */
 287 int com_version(struct command_context *cc)
 288 {
 289         if (cc->argc != 1)
 290                 return -E_COMMAND_SYNTAX;
 291         return sc_send_buffer(&cc->scc, VERSION_TEXT("server")
 292                 "built: " BUILD_DATE "\n"
 293                 UNAME_RS ", " CC_VERSION "\n"
 294         );
 295 }
 296
 297 #define EMPTY_STATUS_ITEMS \
 298         ITEM(PATH) \
 299         ITEM(DIRECTORY) \
 300         ITEM(BASENAME) \
 301         ITEM(SCORE) \
 302         ITEM(ATTRIBUTES_BITMAP) \
 303         ITEM(ATTRIBUTES_TXT) \
 304         ITEM(HASH) \
 305         ITEM(IMAGE_ID) \
 306         ITEM(IMAGE_NAME) \
 307         ITEM(LYRICS_ID) \
 308         ITEM(LYRICS_NAME) \
 309         ITEM(BITRATE) \
 310         ITEM(FORMAT) \
 311         ITEM(FREQUENCY) \
 312         ITEM(CHANNELS) \
 313         ITEM(DURATION) \
 314         ITEM(SECONDS_TOTAL) \
 315         ITEM(NUM_PLAYED) \
 316         ITEM(LAST_PLAYED) \
 317         ITEM(TECHINFO) \
 318         ITEM(ARTIST) \
 319         ITEM(TITLE) \
 320         ITEM(YEAR) \
 321         ITEM(ALBUM) \
 322         ITEM(COMMENT) \
 323         ITEM(AMPLIFICATION)
 324
 325 /**
 326  * Write a list of audio-file related status items with empty values.
 327  *
 328  * This is used by vss when currently no audio file is open.
 329  */
 330 static char *empty_status_items(int parser_friendly)
 331 {
 332         if (parser_friendly)
 333                 return make_message(
 334                         #define ITEM(x) "0004 %02x:\n"
 335                         EMPTY_STATUS_ITEMS
 336                         #undef ITEM
 337                         #define ITEM(x) , SI_ ## x
 338                         EMPTY_STATUS_ITEMS
 339                         #undef ITEM
 340                 );
 341         return make_message(
 342                 #define ITEM(x) "%s:\n"
 343                 EMPTY_STATUS_ITEMS
 344                 #undef ITEM
 345                 #define ITEM(x) ,status_item_list[SI_ ## x]
 346                 EMPTY_STATUS_ITEMS
 347                 #undef ITEM
 348         );
 349 }
 350 #undef EMPTY_STATUS_ITEMS
 351
 352 /* stat */
 353 int com_stat(struct command_context *cc)
 354 {
 355         int i, ret;
 356         struct misc_meta_data tmp, *nmmd = &tmp;
 357         char *s;
 358         int32_t num = 0;
 359         int parser_friendly = 0;
 360
 361         para_sigaction(SIGUSR1, dummy);
 362
 363         for (i = 1; i < cc->argc; i++) {
 364                 const char *arg = cc->argv[i];
 365                 if (arg[0] != '-')
 366                         break;
 367                 if (!strcmp(arg, "--")) {
 368                         i++;
 369                         break;
 370                 }
 371                 if (!strncmp(arg, "-n=", 3)) {
 372                         ret = para_atoi32(arg + 3, &num);
 373                         if (ret < 0)
 374                                 return ret;
 375                         continue;
 376                 }
 377                 if (!strcmp(arg, "-p")) {
 378                         parser_friendly = 1;
 379                         continue;
 380                 }
 381                 return -E_COMMAND_SYNTAX;
 382         }
 383         if (i != cc->argc)
 384                 return -E_COMMAND_SYNTAX;
 385         for (;;) {
 386                 mmd_dup(nmmd);
 387                 s = get_status(nmmd, parser_friendly);
 388                 ret = sc_send_buffer(&cc->scc, s);
 389                 free(s);
 390                 if (ret < 0)
 391                         goto out;
 392                 if (nmmd->vss_status_flags & VSS_NEXT) {
 393                         static char *esi;
 394                         if (!esi)
 395                                 esi = empty_status_items(parser_friendly);
 396                         ret = sc_send_buffer(&cc->scc, esi);
 397                         if (ret < 0)
 398                                 goto out;
 399                 } else
 400                         send_afs_status(cc, parser_friendly);
 401                 ret = 1;
 402                 if (num > 0 && !--num)
 403                         goto out;
 404                 sleep(50);
 405                 if (getppid() == 1)
 406                         return -E_SERVER_CRASH;
 407         }
 408 out:
 409         return ret;
 410 }
 411
 412 static int send_list_of_commands(struct stream_cipher_context *scc, struct server_command *cmd,
 413                 const char *handler)
 414 {
 415         int ret, i;
 416
 417         for (i = 1; cmd->name; cmd++, i++) {
 418                 char *perms = cmd_perms_itohuman(cmd->perms);
 419                 ret = sc_send_va_buffer(scc, "%s\t%s\t%s\t%s\n", cmd->name,
 420                         handler,
 421                         perms,
 422                         cmd->description);
 423                 free(perms);
 424                 if (ret < 0)
 425                         return ret;
 426         }
 427         return 1;
 428 }
 429
 430 /* returns string that must be freed by the caller */
 431 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 432 {
 433         struct server_command *cmd;
 434
 435         for (cmd = server_cmds; cmd->name; cmd++)
 436                 if (!strcmp(cmd->name, name)) {
 437                         if (handler)
 438                                 *handler = para_strdup("server"); /* server commands */
 439                         return cmd;
 440                 }
 441         /* not found, look for commands supported by afs */
 442         for (cmd = afs_cmds; cmd->name; cmd++)
 443                 if (!strcmp(cmd->name, name)) {
 444                         if (handler)
 445                                 *handler = para_strdup("afs");
 446                         return cmd;
 447                 }
 448         return NULL;
 449 }
 450
 451 /* help */
 452 int com_help(struct command_context *cc)
 453 {
 454         struct server_command *cmd;
 455         char *perms, *handler;
 456         int ret;
 457
 458         if (cc->argc < 2) {
 459                 /* no argument given, print list of commands */
 460                 if ((ret = send_list_of_commands(&cc->scc, server_cmds, "server")) < 0)
 461                         return ret;
 462                 return send_list_of_commands(&cc->scc, afs_cmds, "afs");
 463         }
 464         /* argument given for help */
 465         cmd = get_cmd_ptr(cc->argv[1], &handler);
 466         if (!cmd)
 467                 return -E_BAD_CMD;
 468         perms = cmd_perms_itohuman(cmd->perms);
 469         ret = sc_send_va_buffer(&cc->scc,
 470                 "%s - %s\n\n"
 471                 "handler: %s\n"
 472                 "permissions: %s\n"
 473                 "usage: %s\n\n"
 474                 "%s\n",
 475                 cc->argv[1],
 476                 cmd->description,
 477                 handler,
 478                 perms,
 479                 cmd->usage,
 480                 cmd->help
 481         );
 482         free(perms);
 483         free(handler);
 484         return ret;
 485 }
 486
 487 /* hup */
 488 int com_hup(struct command_context *cc)
 489 {
 490         if (cc->argc != 1)
 491                 return -E_COMMAND_SYNTAX;
 492         kill(getppid(), SIGHUP);
 493         return 1;
 494 }
 495
 496 /* term */
 497 int com_term(struct command_context *cc)
 498 {
 499         if (cc->argc != 1)
 500                 return -E_COMMAND_SYNTAX;
 501         kill(getppid(), SIGTERM);
 502         return 1;
 503 }
 504
 505 int com_play(struct command_context *cc)
 506 {
 507         if (cc->argc != 1)
 508                 return -E_COMMAND_SYNTAX;
 509         mutex_lock(mmd_mutex);
 510         mmd->new_vss_status_flags |= VSS_PLAYING;
 511         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 512         mutex_unlock(mmd_mutex);
 513         return 1;
 514 }
 515
 516 /* stop */
 517 int com_stop(struct command_context *cc)
 518 {
 519         if (cc->argc != 1)
 520                 return -E_COMMAND_SYNTAX;
 521         mutex_lock(mmd_mutex);
 522         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 523         mmd->new_vss_status_flags &= ~VSS_REPOS;
 524         mmd->new_vss_status_flags |= VSS_NEXT;
 525         mutex_unlock(mmd_mutex);
 526         return 1;
 527 }
 528
 529 /* pause */
 530 int com_pause(struct command_context *cc)
 531 {
 532         if (cc->argc != 1)
 533                 return -E_COMMAND_SYNTAX;
 534         mutex_lock(mmd_mutex);
 535         if (!vss_paused() && !vss_stopped()) {
 536                 mmd->events++;
 537                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 538                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 539         }
 540         mutex_unlock(mmd_mutex);
 541         return 1;
 542 }
 543
 544 /* next */
 545 int com_next(struct command_context *cc)
 546 {
 547         if (cc->argc != 1)
 548                 return -E_COMMAND_SYNTAX;
 549         mutex_lock(mmd_mutex);
 550         mmd->events++;
 551         mmd->new_vss_status_flags |= VSS_NEXT;
 552         mutex_unlock(mmd_mutex);
 553         return 1;
 554 }
 555
 556 /* nomore */
 557 int com_nomore(struct command_context *cc)
 558 {
 559         if (cc->argc != 1)
 560                 return -E_COMMAND_SYNTAX;
 561         mutex_lock(mmd_mutex);
 562         if (vss_playing() || vss_paused())
 563                 mmd->new_vss_status_flags |= VSS_NOMORE;
 564         mutex_unlock(mmd_mutex);
 565         return 1;
 566 }
 567
 568 /* ff */
 569 int com_ff(struct command_context *cc)
 570 {
 571         long promille;
 572         int ret, backwards = 0;
 573         unsigned i;
 574         char c;
 575
 576         if (cc->argc != 2)
 577                 return -E_COMMAND_SYNTAX;
 578         if (!(ret = sscanf(cc->argv[1], "%u%c", &i, &c)))
 579                 return -E_COMMAND_SYNTAX;
 580         if (ret > 1 && c == '-')
 581                 backwards = 1; /* jmp backwards */
 582         mutex_lock(mmd_mutex);
 583         ret = -E_NO_AUDIO_FILE;
 584         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 585                 goto out;
 586         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 587         if (backwards)
 588                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 589         else
 590                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 591         if (promille < 0)
 592                 promille = 0;
 593         if (promille >  1000) {
 594                 mmd->new_vss_status_flags |= VSS_NEXT;
 595                 goto out;
 596         }
 597         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 598         mmd->new_vss_status_flags |= VSS_REPOS;
 599         mmd->new_vss_status_flags &= ~VSS_NEXT;
 600         mmd->events++;
 601         ret = 1;
 602 out:
 603         mutex_unlock(mmd_mutex);
 604         return ret;
 605 }
 606
 607 /* jmp */
 608 int com_jmp(struct command_context *cc)
 609 {
 610         long unsigned int i;
 611         int ret;
 612
 613         if (cc->argc != 2)
 614                 return -E_COMMAND_SYNTAX;
 615         if (sscanf(cc->argv[1], "%lu", &i) <= 0)
 616                 return -E_COMMAND_SYNTAX;
 617         mutex_lock(mmd_mutex);
 618         ret = -E_NO_AUDIO_FILE;
 619         if (!mmd->afd.afhi.chunks_total)
 620                 goto out;
 621         if (i > 100)
 622                 i = 100;
 623         PARA_INFO_LOG("jumping to %lu%%\n", i);
 624         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 625         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 626                 mmd->chunks_sent, mmd->offset);
 627         mmd->new_vss_status_flags |= VSS_REPOS;
 628         mmd->new_vss_status_flags &= ~VSS_NEXT;
 629         ret = 1;
 630         mmd->events++;
 631 out:
 632         mutex_unlock(mmd_mutex);
 633         return ret;
 634 }
 635
 636 /*
 637  * check if perms are sufficient to exec a command having perms cmd_perms.
 638  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 639  */
 640 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 641 {
 642         PARA_DEBUG_LOG("checking permissions\n");
 643         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 644 }
 645
 646 /*
 647  * Parse first string from *cmd and lookup in table of valid commands.
 648  * On error, NULL is returned.
 649  */
 650 static struct server_command *parse_cmd(const char *cmdstr)
 651 {
 652         char buf[255];
 653         int n = 0;
 654
 655         sscanf(cmdstr, "%200s%n", buf, &n);
 656         if (!n)
 657                 return NULL;
 658         buf[n] = '\0';
 659         return get_cmd_ptr(buf, NULL);
 660 }
 661
 662 static int read_command(struct stream_cipher_context *scc, char **result)
 663 {
 664         int ret;
 665         char buf[4096];
 666         char *command = NULL;
 667
 668         for (;;) {
 669                 size_t numbytes;
 670                 char *p;
 671
 672                 ret = sc_recv_buffer(scc, buf, sizeof(buf));
 673                 if (ret < 0)
 674                         goto out;
 675                 if (!ret)
 676                         break;
 677                 numbytes = ret;
 678                 ret = -E_COMMAND_SYNTAX;
 679                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 680                         goto out;
 681                 command = para_strcat(command, buf);
 682                 p = strstr(command, EOC_MSG);
 683                 if (p) {
 684                         *p = '\0';
 685                         break;
 686                 }
 687         }
 688         ret = command? 1 : -E_COMMAND_SYNTAX;
 689 out:
 690         if (ret < 0)
 691                 free(command);
 692         else
 693                 *result = command;
 694         return ret;
 695
 696 }
 697
 698 static void reset_signals(void)
 699 {
 700         para_sigaction(SIGCHLD, SIG_IGN);
 701         para_sigaction(SIGINT, SIG_DFL);
 702         para_sigaction(SIGTERM, SIG_DFL);
 703         para_sigaction(SIGHUP, SIG_DFL);
 704 }
 705
 706 /**
 707  * Perform user authentication and execute a command.
 708  *
 709  * \param fd The file descriptor to send output to.
 710  * \param peername Identifies the connecting peer.
 711  *
 712  * Whenever para_server accepts an incoming tcp connection on
 713  * the port it listens on, it forks and the resulting child
 714  * calls this function.
 715  *
 716  * An RSA-based challenge/response is used to authenticate
 717  * the peer. It that authentication succeeds, a random
 718  * session key is generated and sent back to the peer,
 719  * encrypted with its RSA public key.  From this point on,
 720  * all transfers are crypted with this session key.
 721  *
 722  * Next it is checked if the peer supplied  a valid server command or a command
 723  * for the audio file selector.  If yes, and if the user has sufficient
 724  * permissions to execute that command, the function calls the corresponding
 725  * command handler which does argument checking and further processing.
 726  *
 727  * In order to cope with a DOS attacks, a timeout is set up
 728  * which terminates the function if the connection was not
 729  * authenticated when the timeout expires.
 730  *
 731  * \sa alarm(2), crypt.c, crypt.h
 732  */
 733 __noreturn void handle_connect(int fd, const char *peername)
 734 {
 735         int ret;
 736         char buf[4096];
 737         unsigned char rand_buf[CHALLENGE_SIZE + 2 * SESSION_KEY_LEN];
 738         unsigned char challenge_hash[HASH_SIZE];
 739         char *p, *command = NULL;
 740         size_t numbytes;
 741         struct command_context cc_struct = {.peer = peername}, *cc = &cc_struct;
 742
 743         cc->scc.fd = fd;
 744         reset_signals();
 745         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 746         ret = mark_fd_blocking(fd);
 747         if (ret < 0)
 748                 goto net_err;
 749         /* send Welcome message */
 750         ret = write_va_buffer(fd, "This is para_server, version "
 751                 PACKAGE_VERSION  ".\n" );
 752         if (ret < 0)
 753                 goto net_err;
 754         /* recv auth request line */
 755         ret = recv_buffer(fd, buf, sizeof(buf));
 756         if (ret < 0)
 757                 goto net_err;
 758         if (ret < 10) {
 759                 ret = -E_AUTH_REQUEST;
 760                 goto net_err;
 761         }
 762         ret = -E_AUTH_REQUEST;
 763         if (strncmp(buf, AUTH_REQUEST_MSG, strlen(AUTH_REQUEST_MSG)))
 764                 goto net_err;
 765         p = buf + strlen(AUTH_REQUEST_MSG);
 766         PARA_DEBUG_LOG("received auth request for user %s\n", p);
 767         cc->u = lookup_user(p);
 768         if (cc->u) {
 769                 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
 770                 ret = pub_encrypt(cc->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 = write_all(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 (!cc->u)
 797                 goto net_err;
 798         /*
 799          * The correct response is the hash 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         hash_function((char *)rand_buf, CHALLENGE_SIZE, challenge_hash);
 806         if (memcmp(challenge_hash, buf, HASH_SIZE))
 807                 goto net_err;
 808         /* auth successful */
 809         alarm(0);
 810         PARA_INFO_LOG("good auth for %s\n", cc->u->name);
 811         /* init stream cipher keys with the second part of the random buffer */
 812         cc->scc.recv = sc_new(rand_buf + CHALLENGE_SIZE, SESSION_KEY_LEN);
 813         cc->scc.send = sc_new(rand_buf + CHALLENGE_SIZE + SESSION_KEY_LEN, SESSION_KEY_LEN);
 814         ret = sc_send_buffer(&cc->scc, PROCEED_MSG);
 815         if (ret < 0)
 816                 goto net_err;
 817         ret = read_command(&cc->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         cc->cmd = parse_cmd(command);
 824         if (!cc->cmd)
 825                 goto err_out;
 826         /* valid command, check permissions */
 827         ret = check_perms(cc->u->perms, cc->cmd);
 828         if (ret < 0)
 829                 goto err_out;
 830         /* valid command and sufficient perms */
 831         ret = create_argv(command, "\n", &cc->argv);
 832         if (ret < 0)
 833                 goto err_out;
 834         cc->argc = ret;
 835         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cc->cmd->name,
 836                 cc->u->name, peername);
 837         ret = cc->cmd->handler(cc);
 838         free_argv(cc->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(&cc->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(cc->scc.recv);
 851         sc_free(cc->scc.send);
 852         mutex_lock(mmd_mutex);
 853         if (cc->cmd && (cc->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 }