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
  15 #include "para.h"
  16 #include "error.h"
  17 #include "server.cmdline.h"
  18 #include "string.h"
  19 #include "afh.h"
  20 #include "afs.h"
  21 #include "server.h"
  22 #include "vss.h"
  23 #include "list.h"
  24 #include "send.h"
  25 #include "rc4.h"
  26 #include "net.h"
  27 #include "daemon.h"
  28 #include "fd.h"
  29 #include "ipc.h"
  30 #include "user_list.h"
  31 #include "server_command_list.h"
  32 #include "afs_command_list.h"
  33
  34 /** Commands including options must be shorter than this. */
  35 #define MAX_COMMAND_LEN 32768
  36
  37 static RC4_KEY rc4_recv_key;
  38 static RC4_KEY rc4_send_key;
  39 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  40
  41 extern int mmd_mutex;
  42 extern struct misc_meta_data *mmd;
  43 extern struct sender senders[];
  44
  45 static void dummy(int s)
  46 {
  47         /*
  48          * At least on Solaris, SIGUSR1 is one-shot, i.e. the signal action is
  49          * restored to the default state once the signal handler has been
  50          * called.
  51          */
  52         if (s == SIGUSR1)
  53                 signal(SIGUSR1, dummy);
  54 }
  55
  56 static void mmd_dup(struct misc_meta_data *new_mmd)
  57 {
  58         mutex_lock(mmd_mutex);
  59         *new_mmd = *mmd;
  60         mutex_unlock(mmd_mutex);
  61 }
  62
  63 /*
  64  * Compute human readable string containing vss status for given integer value.
  65  *
  66  * We don't want to use vss_playing() and friends here because we take a
  67  * snapshot of the mmd struct and use the copy for computing the state of the
  68  * vss. If the real data were used, we would take the mmd lock for a rather
  69  * long time or risk to get an inconsistent view.
  70  */
  71 static char *vss_status_tohuman(unsigned int flags)
  72 {
  73         if (flags & VSS_PLAYING)
  74                 return para_strdup("playing");
  75         if (flags & VSS_NEXT)
  76                 return para_strdup("stopped");
  77         return para_strdup("paused");
  78 }
  79
  80 /*
  81  * return human readable permission string. Never returns NULL.
  82  */
  83 static char *cmd_perms_itohuman(unsigned int perms)
  84 {
  85         char *msg = para_malloc(5 * sizeof(char));
  86
  87         msg[0] = perms & AFS_READ? 'a' : '-';
  88         msg[1] = perms & AFS_WRITE? 'A' : '-';
  89         msg[2] = perms & VSS_READ? 'v' : '-';
  90         msg[3] = perms & VSS_WRITE? 'V' : '-';
  91         msg[4] = '\0';
  92         return msg;
  93 }
  94
  95 /*
  96  * Never returns NULL.
  97  */
  98 static char *vss_get_status_flags(unsigned int flags)
  99 {
 100         char *msg = para_malloc(5 * sizeof(char));
 101
 102         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
 103         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
 104         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 105         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 106         msg[4] = '\0';
 107         return msg;
 108 }
 109
 110 static char *get_status(struct misc_meta_data *nmmd)
 111 {
 112         char *ret, mtime[30] = "";
 113         char *status, *flags; /* vss status info */
 114         char *ut = uptime_str();
 115         long offset = (nmmd->offset + 500) / 1000;
 116         struct timeval now;
 117         struct tm mtime_tm;
 118
 119         /* report real status */
 120         status = vss_status_tohuman(nmmd->vss_status_flags);
 121         flags = vss_get_status_flags(nmmd->vss_status_flags);
 122         if (nmmd->size) { /* parent currently has an audio file open */
 123                 localtime_r(&nmmd->mtime, &mtime_tm);
 124                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 125         }
 126         gettimeofday(&now, NULL);
 127         ret = make_message(
 128                 "%s: %zu\n" /* file size */
 129                 "%s: %s\n" /* mtime */
 130                 "%s: %s\n" /* status */
 131                 "%s: %s\n" /* status flags */
 132                 "%s: %li\n" /* offset */
 133                 "%s: %s\n" /* afs mode */
 134                 "%s: %lu.%lu\n" /* stream start */
 135                 "%s: %lu.%lu\n" /* current server time */
 136                 "%s", /* afs status info */
 137                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 138                 status_item_list[SI_MTIME], mtime,
 139                 status_item_list[SI_STATUS], status,
 140                 status_item_list[SI_STATUS_FLAGS], flags,
 141
 142                 status_item_list[SI_OFFSET], offset,
 143                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 144
 145                 status_item_list[SI_STREAM_START],
 146                         (long unsigned)nmmd->stream_start.tv_sec,
 147                         (long unsigned)nmmd->stream_start.tv_usec,
 148                 status_item_list[SI_CURRENT_TIME],
 149                         (long unsigned)now.tv_sec,
 150                         (long unsigned)now.tv_usec,
 151
 152                 nmmd->afd.verbose_ls_output
 153
 154         );
 155         free(flags);
 156         free(status);
 157         free(ut);
 158         return ret;
 159 }
 160
 161 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 162 {
 163         int i;
 164         /* this has to match sender.h */
 165         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 166
 167         scd->sender_num = -1;
 168         if (argc < 2)
 169                 return -E_COMMAND_SYNTAX;
 170         for (i = 0; senders[i].name; i++)
 171                 if (!strcmp(senders[i].name, argv[1]))
 172                         break;
 173         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 174         if (!senders[i].name)
 175                 return -E_COMMAND_SYNTAX;
 176         scd->sender_num = i;
 177         for (i = 0; subcmds[i]; i++)
 178                 if (!strcmp(subcmds[i], argv[2]))
 179                         break;
 180         if (!subcmds[i])
 181                 return -E_COMMAND_SYNTAX;
 182         scd->cmd_num = i;
 183         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 184                 return -E_SENDER_CMD;
 185         switch (scd->cmd_num) {
 186         case SENDER_ON:
 187         case SENDER_OFF:
 188                 if (argc != 3)
 189                         return -E_COMMAND_SYNTAX;
 190                 break;
 191         case SENDER_DENY:
 192         case SENDER_ALLOW:
 193                 if (argc != 4 && argc != 5)
 194                         return -E_COMMAND_SYNTAX;
 195                 if (!is_valid_ipv4_address(argv[3]))
 196                         return -E_COMMAND_SYNTAX;
 197                 scd->netmask = 32;
 198                 if (argc == 5) {
 199                         scd->netmask = atoi(argv[4]);
 200                         if (scd->netmask < 0 || scd->netmask > 32)
 201                                 return -E_COMMAND_SYNTAX;
 202                 }
 203                 strncpy(scd->host, argv[3], sizeof(scd->host));
 204                 break;
 205         case SENDER_ADD:
 206         case SENDER_DELETE:
 207                 if (argc != 4 || parse_url(argv[3], scd->host,
 208                                 sizeof(scd->host), &scd->port) == NULL)
 209                         return -E_COMMAND_SYNTAX;
 210                 break;
 211         default:
 212                 return -E_COMMAND_SYNTAX;
 213         }
 214         return 1;
 215 }
 216
 217 int com_sender(int fd, int argc, char * const * argv)
 218 {
 219         int i, ret;
 220         struct sender_command_data scd;
 221
 222         if (argc < 2) {
 223                 char *msg = NULL;
 224                 for (i = 0; senders[i].name; i++) {
 225                         char *tmp = make_message("%s%s\n",
 226                                 msg? msg : "", senders[i].name);
 227                         free(msg);
 228                         msg = tmp;
 229                 }
 230                 ret = send_buffer(fd, msg);
 231                 free(msg);
 232                 return ret;
 233         }
 234         ret = check_sender_args(argc, argv, &scd);
 235         if (ret < 0) {
 236                 char *msg;
 237                 if (scd.sender_num < 0)
 238                         return ret;
 239                 msg = senders[scd.sender_num].help();
 240                 ret = send_buffer(fd, msg);
 241                 free(msg);
 242                 return ret;
 243         }
 244         for (i = 0; i < 10; i++) {
 245                 mutex_lock(mmd_mutex);
 246                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 247                         mutex_unlock(mmd_mutex);
 248                         usleep(100 * 1000);
 249                         continue;
 250                 }
 251                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 252                 mutex_unlock(mmd_mutex);
 253                 break;
 254         }
 255         return (i < 10)? 1 : -E_LOCK;
 256 }
 257
 258 /* server info */
 259 int com_si(int fd, int argc, __a_unused char * const * argv)
 260 {
 261         int i, ret;
 262         char *ut;
 263         char *sender_info = NULL, *sender_list = NULL;
 264
 265         if (argc != 1)
 266                 return -E_COMMAND_SYNTAX;
 267         mutex_lock(mmd_mutex);
 268         for (i = 0; senders[i].name; i++) {
 269                 char *info = senders[i].info();
 270                 sender_info = para_strcat(sender_info, info);
 271                 free(info);
 272                 sender_list = para_strcat(sender_list, senders[i].name);
 273                 sender_list = para_strcat(sender_list, " ");
 274         }
 275         ut = uptime_str();
 276         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 277                 "server_pid: %d\n"
 278                 "afs_pid: %d\n"
 279                 "connections (active/accepted/total): %u/%u/%u\n"
 280                 "current loglevel: %s\n"
 281                 "supported audio formats: %s\n"
 282                 "supported senders: %s\n"
 283                 "%s",
 284                 ut, mmd->num_played,
 285                 (int)getppid(),
 286                 (int)mmd->afs_pid,
 287                 mmd->active_connections,
 288                 mmd->num_commands,
 289                 mmd->num_connects,
 290                 conf.loglevel_arg,
 291                 supported_audio_formats(),
 292                 sender_list,
 293                 sender_info
 294         );
 295         mutex_unlock(mmd_mutex);
 296         free(ut);
 297         free(sender_list);
 298         free(sender_info);
 299         return ret;
 300 }
 301
 302 /* version */
 303 int com_version(int fd, int argc, __a_unused char * const * argv)
 304 {
 305         if (argc != 1)
 306                 return -E_COMMAND_SYNTAX;
 307         return send_buffer(fd, VERSION_TEXT("server")
 308                 "built: " BUILD_DATE "\n"
 309                 UNAME_RS ", " CC_VERSION "\n"
 310         );
 311 }
 312
 313 /* stat */
 314 int com_stat(int fd, int argc, char * const * argv)
 315 {
 316         int ret, num = 0;/* status will be printed that many
 317                           * times. num <= 0 means: print forever
 318                           */
 319         struct misc_meta_data tmp, *nmmd = &tmp;
 320         char *s;
 321
 322         signal(SIGUSR1, dummy);
 323
 324         if (argc > 1)
 325                 num = atoi(argv[1]);
 326         for (;;) {
 327
 328                 mmd_dup(nmmd);
 329                 s = get_status(nmmd);
 330                 ret = send_buffer(fd, s);
 331                 free(s);
 332                 if (ret < 0)
 333                         goto out;
 334                 ret = 1;
 335                 if (num > 0 && !--num)
 336                         goto out;
 337                 sleep(50);
 338                 if (getppid() == 1)
 339                         return -E_SERVER_CRASH;
 340         }
 341 out:
 342         return ret;
 343 }
 344
 345 static int send_list_of_commands(int fd, struct server_command *cmd,
 346                 const char *handler)
 347 {
 348         int ret, i;
 349
 350         for (i = 1; cmd->name; cmd++, i++) {
 351                 char *perms = cmd_perms_itohuman(cmd->perms);
 352                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 353                         handler,
 354                         perms,
 355                         cmd->description);
 356                 free(perms);
 357                 if (ret < 0)
 358                         return ret;
 359         }
 360         return 1;
 361 }
 362
 363 /* returns string that must be freed by the caller */
 364 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 365 {
 366         struct server_command *cmd;
 367
 368         for (cmd = server_cmds; cmd->name; cmd++)
 369                 if (!strcmp(cmd->name, name)) {
 370                         if (handler)
 371                                 *handler = para_strdup("server"); /* server commands */
 372                         return cmd;
 373                 }
 374         /* not found, look for commands supported by afs */
 375         for (cmd = afs_cmds; cmd->name; cmd++)
 376                 if (!strcmp(cmd->name, name)) {
 377                         if (handler)
 378                                 *handler = para_strdup("afs");
 379                         return cmd;
 380                 }
 381         return NULL;
 382 }
 383
 384 /* help */
 385 int com_help(int fd, int argc, char * const * argv)
 386 {
 387         struct server_command *cmd;
 388         char *perms, *handler;
 389         int ret;
 390
 391         if (argc < 2) {
 392                 /* no argument given, print list of commands */
 393                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 394                         return ret;
 395                 return send_list_of_commands(fd, afs_cmds, "afs");
 396         }
 397         /* argument given for help */
 398         cmd = get_cmd_ptr(argv[1], &handler);
 399         if (!cmd) {
 400                 free(handler);
 401                 return -E_BAD_CMD;
 402         }
 403         perms = cmd_perms_itohuman(cmd->perms);
 404         ret = send_va_buffer(fd,
 405                 "%s - %s\n\n"
 406                 "handler: %s\n"
 407                 "permissions: %s\n"
 408                 "usage: %s\n\n"
 409                 "%s\n",
 410                 argv[1],
 411                 cmd->description,
 412                 handler,
 413                 perms,
 414                 cmd->usage,
 415                 cmd->help
 416         );
 417         free(perms);
 418         free(handler);
 419         return ret;
 420 }
 421
 422 /* hup */
 423 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 424 {
 425         if (argc != 1)
 426                 return -E_COMMAND_SYNTAX;
 427         kill(getppid(), SIGHUP);
 428         return 1;
 429 }
 430
 431 /* term */
 432 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 433 {
 434         if (argc != 1)
 435                 return -E_COMMAND_SYNTAX;
 436         kill(getppid(), SIGTERM);
 437         return 1;
 438 }
 439
 440 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 441 {
 442         if (argc != 1)
 443                 return -E_COMMAND_SYNTAX;
 444         mutex_lock(mmd_mutex);
 445         mmd->new_vss_status_flags |= VSS_PLAYING;
 446         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 447         mutex_unlock(mmd_mutex);
 448         return 1;
 449
 450 }
 451
 452 /* stop */
 453 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 454 {
 455         if (argc != 1)
 456                 return -E_COMMAND_SYNTAX;
 457         mutex_lock(mmd_mutex);
 458         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 459         mmd->new_vss_status_flags &= ~VSS_REPOS;
 460         mmd->new_vss_status_flags |= VSS_NEXT;
 461         mutex_unlock(mmd_mutex);
 462         return 1;
 463 }
 464
 465 /* pause */
 466 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 467 {
 468         if (argc != 1)
 469                 return -E_COMMAND_SYNTAX;
 470         mutex_lock(mmd_mutex);
 471         if (!vss_paused() && !vss_stopped()) {
 472                 mmd->events++;
 473                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 474                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 475         }
 476         mutex_unlock(mmd_mutex);
 477         return 1;
 478 }
 479
 480 /* next */
 481 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 482 {
 483         if (argc != 1)
 484                 return -E_COMMAND_SYNTAX;
 485         mutex_lock(mmd_mutex);
 486         mmd->events++;
 487         mmd->new_vss_status_flags |= VSS_NEXT;
 488         mutex_unlock(mmd_mutex);
 489         return 1;
 490 }
 491
 492 /* nomore */
 493 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 494 {
 495         if (argc != 1)
 496                 return -E_COMMAND_SYNTAX;
 497         mutex_lock(mmd_mutex);
 498         if (vss_playing() || vss_paused())
 499                 mmd->new_vss_status_flags |= VSS_NOMORE;
 500         mutex_unlock(mmd_mutex);
 501         return 1;
 502 }
 503
 504 /* ff */
 505 int com_ff(__a_unused int fd, int argc, char * const * argv)
 506 {
 507         long promille;
 508         int ret, backwards = 0;
 509         unsigned i;
 510         char c;
 511
 512         if (argc != 2)
 513                 return -E_COMMAND_SYNTAX;
 514         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 515                 return -E_COMMAND_SYNTAX;
 516         if (ret > 1 && c == '-')
 517                 backwards = 1; /* jmp backwards */
 518         mutex_lock(mmd_mutex);
 519         ret = -E_NO_AUDIO_FILE;
 520         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 521                 goto out;
 522         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 523         if (backwards)
 524                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 525         else
 526                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 527         if (promille < 0)
 528                 promille = 0;
 529         if (promille >  1000) {
 530                 mmd->new_vss_status_flags |= VSS_NEXT;
 531                 goto out;
 532         }
 533         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 534         mmd->new_vss_status_flags |= VSS_REPOS;
 535         mmd->new_vss_status_flags &= ~VSS_NEXT;
 536         mmd->events++;
 537         ret = 1;
 538 out:
 539         mutex_unlock(mmd_mutex);
 540         return ret;
 541 }
 542
 543 /* jmp */
 544 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 545 {
 546         long unsigned int i;
 547         int ret;
 548
 549         if (argc != 2)
 550                 return -E_COMMAND_SYNTAX;
 551         if (sscanf(argv[1], "%lu", &i) <= 0)
 552                 return -E_COMMAND_SYNTAX;
 553         mutex_lock(mmd_mutex);
 554         ret = -E_NO_AUDIO_FILE;
 555         if (!mmd->afd.afhi.chunks_total)
 556                 goto out;
 557         if (i > 100)
 558                 i = 100;
 559         PARA_INFO_LOG("jumping to %lu%%\n", i);
 560         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 561         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 562                 mmd->chunks_sent, mmd->offset);
 563         mmd->new_vss_status_flags |= VSS_REPOS;
 564         mmd->new_vss_status_flags &= ~VSS_NEXT;
 565         ret = 1;
 566         mmd->events++;
 567 out:
 568         mutex_unlock(mmd_mutex);
 569         return ret;
 570 }
 571
 572 /*
 573  * check if perms are sufficient to exec a command having perms cmd_perms.
 574  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 575  */
 576 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 577 {
 578         PARA_DEBUG_LOG("checking permissions\n");
 579         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 580 }
 581
 582 /*
 583  * Parse first string from *cmd and lookup in table of valid commands.
 584  * On error, NULL is returned.
 585  */
 586 static struct server_command *parse_cmd(const char *cmdstr)
 587 {
 588         char buf[255];
 589         int n = 0;
 590
 591         sscanf(cmdstr, "%200s%n", buf, &n);
 592         if (!n)
 593                 return NULL;
 594         buf[n] = '\0';
 595         return get_cmd_ptr(buf, NULL);
 596 }
 597
 598 static void init_rc4_keys(void)
 599 {
 600         int i;
 601
 602         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 603                 rc4_buf[i] = para_random(256);
 604         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 605                 (unsigned char) rc4_buf[0],
 606                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 607         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 608         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 609 }
 610
 611 static void rc4_recv(unsigned long len, const unsigned char *indata,
 612                 unsigned char *outdata, __a_unused void *private_data)
 613 {
 614         RC4(&rc4_recv_key, len, indata, outdata);
 615 }
 616
 617 static void rc4_send(unsigned long len, const unsigned char *indata,
 618                 unsigned char *outdata, __a_unused void *private_data)
 619 {
 620         RC4(&rc4_send_key, len, indata, outdata);
 621 }
 622
 623 static int read_command(int fd, char **result)
 624 {
 625         int ret;
 626         char buf[4096];
 627         char *command = NULL;
 628
 629         for (;;) {
 630                 size_t numbytes;
 631                 char *p;
 632
 633                 ret = recv_buffer(fd, buf, sizeof(buf));
 634                 if (ret < 0)
 635                         goto out;
 636                 if (!ret)
 637                         break;
 638                 numbytes = ret;
 639                 ret = -E_COMMAND_SYNTAX;
 640                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 641                         goto out;
 642                 command = para_strcat(command, buf);
 643                 p = strstr(command, EOC_MSG);
 644                 if (p) {
 645                         *p = '\0';
 646                         break;
 647                 }
 648         }
 649         ret = command? 1 : -E_COMMAND_SYNTAX;
 650 out:
 651         if (ret < 0)
 652                 free(command);
 653         else
 654                 *result = command;
 655         return ret;
 656
 657 }
 658
 659 /**
 660  * Perform user authentication and execute a command.
 661  *
 662  * \param fd The file descriptor to send output to.
 663  * \param peername Identifies the connecting peer.
 664  *
 665  * Whenever para_server accepts an incoming tcp connection on
 666  * the port it listens on, it forks and the resulting child
 667  * calls this function.
 668  *
 669  * An RSA-based challenge/response is used to authenticate
 670  * the peer. It that authentication succeeds, a random RC4
 671  * session key is generated and sent back to the peer,
 672  * encrypted with its RSA public key.  From this point on,
 673  * all transfers are crypted with this session key.
 674  *
 675  * Next it is checked if the peer supplied  a valid server command or a command
 676  * for the audio file selector.  If yes, and if the user has sufficient
 677  * permissions to execute that command, the function calls the corresponding
 678  * command handler which does argument checking and further processing.
 679  *
 680  * In order to cope with a DOS attacks, a timeout is set up
 681  * which terminates the function if the connection was not
 682  * authenticated when the timeout expires.
 683  *
 684  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 685  */
 686 __noreturn void handle_connect(int fd, const char *peername)
 687 {
 688         int ret, argc, use_rc4 = 0;
 689         char buf[4096];
 690         unsigned char crypt_buf[MAXLINE];
 691         struct user *u;
 692         struct server_command *cmd = NULL;
 693         long unsigned challenge_nr, chall_response;
 694         char **argv = NULL;
 695         char *p, *command = NULL;
 696         size_t numbytes;
 697
 698         signal(SIGCHLD, SIG_IGN);
 699         signal(SIGINT, SIG_DFL);
 700         signal(SIGTERM, SIG_DFL);
 701         signal(SIGHUP, SIG_DFL);
 702
 703         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 704         ret = mark_fd_blocking(fd);
 705         if (ret < 0)
 706                 goto err_out;
 707         challenge_nr = random();
 708         /* send Welcome message */
 709         ret = send_va_buffer(fd, "This is para_server, version "
 710                 PACKAGE_VERSION  ".\n" );
 711         if (ret < 0)
 712                 goto err_out;
 713         /* recv auth request line */
 714         ret = recv_buffer(fd, buf, sizeof(buf));
 715         if (ret < 0)
 716                 goto err_out;
 717         if (ret <= 6) {
 718                 ret = -E_AUTH;
 719                 goto err_out;
 720         }
 721         numbytes = ret;
 722         ret = -E_AUTH;
 723         if (strncmp(buf, "auth ", 5))
 724                 goto err_out;
 725
 726         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 727                 p = buf + 5; /* client version < 0.2.6 */
 728         else {
 729                 p = buf + 9; /* client version >= 0.2.6 */
 730                 use_rc4 = 1;
 731         }
 732         PARA_DEBUG_LOG("received %s request for user %s\n",
 733                 use_rc4? "rc4" : "auth", p);
 734         ret = -E_BAD_USER;
 735         u = lookup_user(p);
 736         if (!u)
 737                 goto err_out;
 738         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 739         if (ret <= 0)
 740                 goto err_out;
 741         numbytes = ret;
 742         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 743         /* We can't use send_buffer here since buf may contain null bytes */
 744         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 745         if (ret < 0)
 746                 goto net_err;
 747         /* recv decrypted number */
 748         ret = recv_buffer(fd, buf, sizeof(buf));
 749         if (ret < 0)
 750                 goto net_err;
 751         numbytes = ret;
 752         ret = -E_AUTH;
 753         if (!numbytes)
 754                 goto net_err;
 755         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 756                         || chall_response != challenge_nr)
 757                 goto err_out;
 758         /* auth successful, send 'Proceed' message */
 759         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 760         sprintf(buf, "%s", PROCEED_MSG);
 761         if (use_rc4) {
 762                 init_rc4_keys();
 763                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 764                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 765                 if (ret <= 0)
 766                         goto err_out;
 767                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 768         } else
 769                 numbytes = strlen(buf);
 770         ret = send_bin_buffer(fd, buf, numbytes);
 771         if (ret < 0)
 772                 goto net_err;
 773         if (use_rc4)
 774                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 775         ret = read_command(fd, &command);
 776         if (ret == -E_COMMAND_SYNTAX)
 777                 goto err_out;
 778         if (ret < 0)
 779                 goto net_err;
 780         ret = -E_BAD_CMD;
 781         cmd = parse_cmd(command);
 782         if (!cmd)
 783                 goto err_out;
 784         /* valid command, check permissions */
 785         ret = check_perms(u->perms, cmd);
 786         if (ret < 0)
 787                 goto err_out;
 788         /* valid command and sufficient perms */
 789         alarm(0);
 790         argc = split_args(command, &argv, "\n");
 791         mutex_lock(mmd_mutex);
 792         mmd->num_commands++;
 793         mutex_unlock(mmd_mutex);
 794         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 795                         peername);
 796         ret = cmd->handler(fd, argc, argv);
 797         if (ret >= 0)
 798                 goto out;
 799 err_out:
 800         send_va_buffer(fd, "%s\n", para_strerror(-ret));
 801 net_err:
 802         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 803 out:
 804         free(command);
 805         free(argv);
 806         mutex_lock(mmd_mutex);
 807         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 808                 mmd->events++;
 809         mmd->active_connections--;
 810         mutex_unlock(mmd_mutex);
 811         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 812 }