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 #include "sched.h"
  34 #include "signal.h"
  35
  36 /** Commands including options must be shorter than this. */
  37 #define MAX_COMMAND_LEN 32768
  38
  39 static RC4_KEY rc4_recv_key;
  40 static RC4_KEY rc4_send_key;
  41 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  42
  43 extern int mmd_mutex;
  44 extern struct misc_meta_data *mmd;
  45 extern struct sender senders[];
  46
  47 static void dummy(__a_unused int s)
  48 {
  49 }
  50
  51 static void mmd_dup(struct misc_meta_data *new_mmd)
  52 {
  53         mutex_lock(mmd_mutex);
  54         *new_mmd = *mmd;
  55         mutex_unlock(mmd_mutex);
  56 }
  57
  58 /*
  59  * Compute human readable string containing vss status for given integer value.
  60  *
  61  * We don't want to use vss_playing() and friends here because we take a
  62  * snapshot of the mmd struct and use the copy for computing the state of the
  63  * vss. If the real data were used, we would take the mmd lock for a rather
  64  * long time or risk to get an inconsistent view.
  65  */
  66 static char *vss_status_tohuman(unsigned int flags)
  67 {
  68         if (flags & VSS_PLAYING)
  69                 return para_strdup("playing");
  70         if (flags & VSS_NEXT)
  71                 return para_strdup("stopped");
  72         return para_strdup("paused");
  73 }
  74
  75 /*
  76  * return human readable permission string. Never returns NULL.
  77  */
  78 static char *cmd_perms_itohuman(unsigned int perms)
  79 {
  80         char *msg = para_malloc(5 * sizeof(char));
  81
  82         msg[0] = perms & AFS_READ? 'a' : '-';
  83         msg[1] = perms & AFS_WRITE? 'A' : '-';
  84         msg[2] = perms & VSS_READ? 'v' : '-';
  85         msg[3] = perms & VSS_WRITE? 'V' : '-';
  86         msg[4] = '\0';
  87         return msg;
  88 }
  89
  90 /*
  91  * Never returns NULL.
  92  */
  93 static char *vss_get_status_flags(unsigned int flags)
  94 {
  95         char *msg = para_malloc(5 * sizeof(char));
  96
  97         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  98         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
  99         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
 100         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
 101         msg[4] = '\0';
 102         return msg;
 103 }
 104
 105 static char *get_status(struct misc_meta_data *nmmd)
 106 {
 107         char *ret, mtime[30] = "";
 108         char *status, *flags; /* vss status info */
 109         char *ut = uptime_str();
 110         long offset = (nmmd->offset + 500) / 1000;
 111         struct timeval current_time;
 112         struct tm mtime_tm;
 113
 114         /* report real status */
 115         status = vss_status_tohuman(nmmd->vss_status_flags);
 116         flags = vss_get_status_flags(nmmd->vss_status_flags);
 117         if (nmmd->size) { /* parent currently has an audio file open */
 118                 localtime_r(&nmmd->mtime, &mtime_tm);
 119                 strftime(mtime, 29, "%b %d %Y", &mtime_tm);
 120         }
 121         gettimeofday(&current_time, NULL);
 122         ret = make_message(
 123                 "%s: %zu\n" /* file size */
 124                 "%s: %s\n" /* mtime */
 125                 "%s: %s\n" /* status */
 126                 "%s: %s\n" /* status flags */
 127                 "%s: %li\n" /* offset */
 128                 "%s: %s\n" /* afs mode */
 129                 "%s: %lu.%lu\n" /* stream start */
 130                 "%s: %lu.%lu\n" /* current server time */
 131                 "%s", /* afs status info */
 132                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 133                 status_item_list[SI_MTIME], mtime,
 134                 status_item_list[SI_STATUS], status,
 135                 status_item_list[SI_STATUS_FLAGS], flags,
 136
 137                 status_item_list[SI_OFFSET], offset,
 138                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 139
 140                 status_item_list[SI_STREAM_START],
 141                         (long unsigned)nmmd->stream_start.tv_sec,
 142                         (long unsigned)nmmd->stream_start.tv_usec,
 143                 status_item_list[SI_CURRENT_TIME],
 144                         (long unsigned)current_time.tv_sec,
 145                         (long unsigned)current_time.tv_usec,
 146
 147                 nmmd->afd.verbose_ls_output
 148
 149         );
 150         free(flags);
 151         free(status);
 152         free(ut);
 153         return ret;
 154 }
 155
 156 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 157 {
 158         int i;
 159         /* this has to match sender.h */
 160         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 161
 162         scd->sender_num = -1;
 163         if (argc < 2)
 164                 return -E_COMMAND_SYNTAX;
 165         for (i = 0; senders[i].name; i++)
 166                 if (!strcmp(senders[i].name, argv[1]))
 167                         break;
 168         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 169         if (!senders[i].name)
 170                 return -E_COMMAND_SYNTAX;
 171         scd->sender_num = i;
 172         for (i = 0; subcmds[i]; i++)
 173                 if (!strcmp(subcmds[i], argv[2]))
 174                         break;
 175         if (!subcmds[i])
 176                 return -E_COMMAND_SYNTAX;
 177         scd->cmd_num = i;
 178         if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
 179                 return -E_SENDER_CMD;
 180         switch (scd->cmd_num) {
 181         case SENDER_ON:
 182         case SENDER_OFF:
 183                 if (argc != 3)
 184                         return -E_COMMAND_SYNTAX;
 185                 break;
 186         case SENDER_DENY:
 187         case SENDER_ALLOW:
 188                 if (argc != 4 || parse_cidr(argv[3], scd->host,
 189                                 sizeof(scd->host), &scd->netmask) == NULL)
 190                         return -E_COMMAND_SYNTAX;
 191                 break;
 192         case SENDER_ADD:
 193         case SENDER_DELETE:
 194                 if (argc != 4)
 195                         return -E_COMMAND_SYNTAX;
 196                 return parse_fec_url(argv[3], scd);
 197         default:
 198                 return -E_COMMAND_SYNTAX;
 199         }
 200         return 1;
 201 }
 202
 203 int com_sender(int fd, int argc, char * const * argv)
 204 {
 205         int i, ret;
 206         struct sender_command_data scd;
 207
 208         if (argc < 2) {
 209                 char *msg = NULL;
 210                 for (i = 0; senders[i].name; i++) {
 211                         char *tmp = make_message("%s%s\n",
 212                                 msg? msg : "", senders[i].name);
 213                         free(msg);
 214                         msg = tmp;
 215                 }
 216                 ret = send_buffer(fd, msg);
 217                 free(msg);
 218                 return ret;
 219         }
 220         ret = check_sender_args(argc, argv, &scd);
 221         if (ret < 0) {
 222                 char *msg;
 223                 if (scd.sender_num < 0)
 224                         return ret;
 225                 msg = senders[scd.sender_num].help();
 226                 ret = send_buffer(fd, msg);
 227                 free(msg);
 228                 return ret;
 229         }
 230         for (i = 0; i < 10; i++) {
 231                 mutex_lock(mmd_mutex);
 232                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 233                         mutex_unlock(mmd_mutex);
 234                         usleep(100 * 1000);
 235                         continue;
 236                 }
 237                 memcpy(&mmd->sender_cmd_data, &scd, sizeof(scd));
 238                 mutex_unlock(mmd_mutex);
 239                 break;
 240         }
 241         return (i < 10)? 1 : -E_LOCK;
 242 }
 243
 244 /* server info */
 245 int com_si(int fd, int argc, __a_unused char * const * argv)
 246 {
 247         int i, ret;
 248         char *ut;
 249         char *sender_info = NULL, *sender_list = NULL;
 250
 251         if (argc != 1)
 252                 return -E_COMMAND_SYNTAX;
 253         mutex_lock(mmd_mutex);
 254         for (i = 0; senders[i].name; i++) {
 255                 char *info = senders[i].info();
 256                 sender_info = para_strcat(sender_info, info);
 257                 free(info);
 258                 sender_list = para_strcat(sender_list, senders[i].name);
 259                 sender_list = para_strcat(sender_list, " ");
 260         }
 261         ut = uptime_str();
 262         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 263                 "server_pid: %d\n"
 264                 "afs_pid: %d\n"
 265                 "connections (active/accepted/total): %u/%u/%u\n"
 266                 "current loglevel: %s\n"
 267                 "supported audio formats: %s\n"
 268                 "supported senders: %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                 supported_audio_formats(),
 278                 sender_list,
 279                 sender_info
 280         );
 281         mutex_unlock(mmd_mutex);
 282         free(ut);
 283         free(sender_list);
 284         free(sender_info);
 285         return ret;
 286 }
 287
 288 /* version */
 289 int com_version(int fd, int argc, __a_unused char * const * argv)
 290 {
 291         if (argc != 1)
 292                 return -E_COMMAND_SYNTAX;
 293         return send_buffer(fd, VERSION_TEXT("server")
 294                 "built: " BUILD_DATE "\n"
 295                 UNAME_RS ", " CC_VERSION "\n"
 296         );
 297 }
 298
 299 /* stat */
 300 int com_stat(int fd, int argc, char * const * argv)
 301 {
 302         int ret, num = 0;/* status will be printed that many
 303                           * times. num <= 0 means: print forever
 304                           */
 305         struct misc_meta_data tmp, *nmmd = &tmp;
 306         char *s;
 307
 308         para_sigaction(SIGUSR1, dummy);
 309
 310         if (argc > 2)
 311                 return -E_COMMAND_SYNTAX;
 312         if (argc > 1) {
 313                 ret = para_atoi32(argv[1], &num);
 314                 if (ret < 0)
 315                         goto out;
 316         }
 317         for (;;) {
 318
 319                 mmd_dup(nmmd);
 320                 s = get_status(nmmd);
 321                 ret = send_buffer(fd, s);
 322                 free(s);
 323                 if (ret < 0)
 324                         goto out;
 325                 ret = 1;
 326                 if (num > 0 && !--num)
 327                         goto out;
 328                 sleep(50);
 329                 if (getppid() == 1)
 330                         return -E_SERVER_CRASH;
 331         }
 332 out:
 333         return ret;
 334 }
 335
 336 static int send_list_of_commands(int fd, struct server_command *cmd,
 337                 const char *handler)
 338 {
 339         int ret, i;
 340
 341         for (i = 1; cmd->name; cmd++, i++) {
 342                 char *perms = cmd_perms_itohuman(cmd->perms);
 343                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 344                         handler,
 345                         perms,
 346                         cmd->description);
 347                 free(perms);
 348                 if (ret < 0)
 349                         return ret;
 350         }
 351         return 1;
 352 }
 353
 354 /* returns string that must be freed by the caller */
 355 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 356 {
 357         struct server_command *cmd;
 358
 359         for (cmd = server_cmds; cmd->name; cmd++)
 360                 if (!strcmp(cmd->name, name)) {
 361                         if (handler)
 362                                 *handler = para_strdup("server"); /* server commands */
 363                         return cmd;
 364                 }
 365         /* not found, look for commands supported by afs */
 366         for (cmd = afs_cmds; cmd->name; cmd++)
 367                 if (!strcmp(cmd->name, name)) {
 368                         if (handler)
 369                                 *handler = para_strdup("afs");
 370                         return cmd;
 371                 }
 372         return NULL;
 373 }
 374
 375 /* help */
 376 int com_help(int fd, int argc, char * const * argv)
 377 {
 378         struct server_command *cmd;
 379         char *perms, *handler;
 380         int ret;
 381
 382         if (argc < 2) {
 383                 /* no argument given, print list of commands */
 384                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 385                         return ret;
 386                 return send_list_of_commands(fd, afs_cmds, "afs");
 387         }
 388         /* argument given for help */
 389         cmd = get_cmd_ptr(argv[1], &handler);
 390         if (!cmd) {
 391                 free(handler);
 392                 return -E_BAD_CMD;
 393         }
 394         perms = cmd_perms_itohuman(cmd->perms);
 395         ret = send_va_buffer(fd,
 396                 "%s - %s\n\n"
 397                 "handler: %s\n"
 398                 "permissions: %s\n"
 399                 "usage: %s\n\n"
 400                 "%s\n",
 401                 argv[1],
 402                 cmd->description,
 403                 handler,
 404                 perms,
 405                 cmd->usage,
 406                 cmd->help
 407         );
 408         free(perms);
 409         free(handler);
 410         return ret;
 411 }
 412
 413 /* hup */
 414 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 415 {
 416         if (argc != 1)
 417                 return -E_COMMAND_SYNTAX;
 418         kill(getppid(), SIGHUP);
 419         return 1;
 420 }
 421
 422 /* term */
 423 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 424 {
 425         if (argc != 1)
 426                 return -E_COMMAND_SYNTAX;
 427         kill(getppid(), SIGTERM);
 428         return 1;
 429 }
 430
 431 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 432 {
 433         if (argc != 1)
 434                 return -E_COMMAND_SYNTAX;
 435         mutex_lock(mmd_mutex);
 436         mmd->new_vss_status_flags |= VSS_PLAYING;
 437         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 438         mutex_unlock(mmd_mutex);
 439         return 1;
 440
 441 }
 442
 443 /* stop */
 444 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 445 {
 446         if (argc != 1)
 447                 return -E_COMMAND_SYNTAX;
 448         mutex_lock(mmd_mutex);
 449         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 450         mmd->new_vss_status_flags &= ~VSS_REPOS;
 451         mmd->new_vss_status_flags |= VSS_NEXT;
 452         mutex_unlock(mmd_mutex);
 453         return 1;
 454 }
 455
 456 /* pause */
 457 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 458 {
 459         if (argc != 1)
 460                 return -E_COMMAND_SYNTAX;
 461         mutex_lock(mmd_mutex);
 462         if (!vss_paused() && !vss_stopped()) {
 463                 mmd->events++;
 464                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 465                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 466         }
 467         mutex_unlock(mmd_mutex);
 468         return 1;
 469 }
 470
 471 /* next */
 472 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 473 {
 474         if (argc != 1)
 475                 return -E_COMMAND_SYNTAX;
 476         mutex_lock(mmd_mutex);
 477         mmd->events++;
 478         mmd->new_vss_status_flags |= VSS_NEXT;
 479         mutex_unlock(mmd_mutex);
 480         return 1;
 481 }
 482
 483 /* nomore */
 484 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 485 {
 486         if (argc != 1)
 487                 return -E_COMMAND_SYNTAX;
 488         mutex_lock(mmd_mutex);
 489         if (vss_playing() || vss_paused())
 490                 mmd->new_vss_status_flags |= VSS_NOMORE;
 491         mutex_unlock(mmd_mutex);
 492         return 1;
 493 }
 494
 495 /* ff */
 496 int com_ff(__a_unused int fd, int argc, char * const * argv)
 497 {
 498         long promille;
 499         int ret, backwards = 0;
 500         unsigned i;
 501         char c;
 502
 503         if (argc != 2)
 504                 return -E_COMMAND_SYNTAX;
 505         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 506                 return -E_COMMAND_SYNTAX;
 507         if (ret > 1 && c == '-')
 508                 backwards = 1; /* jmp backwards */
 509         mutex_lock(mmd_mutex);
 510         ret = -E_NO_AUDIO_FILE;
 511         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 512                 goto out;
 513         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 514         if (backwards)
 515                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 516         else
 517                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 518         if (promille < 0)
 519                 promille = 0;
 520         if (promille >  1000) {
 521                 mmd->new_vss_status_flags |= VSS_NEXT;
 522                 goto out;
 523         }
 524         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 525         mmd->new_vss_status_flags |= VSS_REPOS;
 526         mmd->new_vss_status_flags &= ~VSS_NEXT;
 527         mmd->events++;
 528         ret = 1;
 529 out:
 530         mutex_unlock(mmd_mutex);
 531         return ret;
 532 }
 533
 534 /* jmp */
 535 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 536 {
 537         long unsigned int i;
 538         int ret;
 539
 540         if (argc != 2)
 541                 return -E_COMMAND_SYNTAX;
 542         if (sscanf(argv[1], "%lu", &i) <= 0)
 543                 return -E_COMMAND_SYNTAX;
 544         mutex_lock(mmd_mutex);
 545         ret = -E_NO_AUDIO_FILE;
 546         if (!mmd->afd.afhi.chunks_total)
 547                 goto out;
 548         if (i > 100)
 549                 i = 100;
 550         PARA_INFO_LOG("jumping to %lu%%\n", i);
 551         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 552         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 553                 mmd->chunks_sent, mmd->offset);
 554         mmd->new_vss_status_flags |= VSS_REPOS;
 555         mmd->new_vss_status_flags &= ~VSS_NEXT;
 556         ret = 1;
 557         mmd->events++;
 558 out:
 559         mutex_unlock(mmd_mutex);
 560         return ret;
 561 }
 562
 563 /*
 564  * check if perms are sufficient to exec a command having perms cmd_perms.
 565  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 566  */
 567 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 568 {
 569         PARA_DEBUG_LOG("checking permissions\n");
 570         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 571 }
 572
 573 /*
 574  * Parse first string from *cmd and lookup in table of valid commands.
 575  * On error, NULL is returned.
 576  */
 577 static struct server_command *parse_cmd(const char *cmdstr)
 578 {
 579         char buf[255];
 580         int n = 0;
 581
 582         sscanf(cmdstr, "%200s%n", buf, &n);
 583         if (!n)
 584                 return NULL;
 585         buf[n] = '\0';
 586         return get_cmd_ptr(buf, NULL);
 587 }
 588
 589 static void init_rc4_keys(void)
 590 {
 591         int i;
 592
 593         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 594                 rc4_buf[i] = para_random(256);
 595         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 596                 (unsigned char) rc4_buf[0],
 597                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 598         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 599         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 600 }
 601
 602 static void rc4_recv(unsigned long len, const unsigned char *indata,
 603                 unsigned char *outdata, __a_unused void *private_data)
 604 {
 605         RC4(&rc4_recv_key, len, indata, outdata);
 606 }
 607
 608 static void rc4_send(unsigned long len, const unsigned char *indata,
 609                 unsigned char *outdata, __a_unused void *private_data)
 610 {
 611         RC4(&rc4_send_key, len, indata, outdata);
 612 }
 613
 614 static int read_command(int fd, char **result)
 615 {
 616         int ret;
 617         char buf[4096];
 618         char *command = NULL;
 619
 620         for (;;) {
 621                 size_t numbytes;
 622                 char *p;
 623
 624                 ret = recv_buffer(fd, buf, sizeof(buf));
 625                 if (ret < 0)
 626                         goto out;
 627                 if (!ret)
 628                         break;
 629                 numbytes = ret;
 630                 ret = -E_COMMAND_SYNTAX;
 631                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 632                         goto out;
 633                 command = para_strcat(command, buf);
 634                 p = strstr(command, EOC_MSG);
 635                 if (p) {
 636                         *p = '\0';
 637                         break;
 638                 }
 639         }
 640         ret = command? 1 : -E_COMMAND_SYNTAX;
 641 out:
 642         if (ret < 0)
 643                 free(command);
 644         else
 645                 *result = command;
 646         return ret;
 647
 648 }
 649
 650 static void reset_signals(void)
 651 {
 652         para_sigaction(SIGCHLD, SIG_IGN);
 653         para_sigaction(SIGINT, SIG_DFL);
 654         para_sigaction(SIGTERM, SIG_DFL);
 655         para_sigaction(SIGHUP, SIG_DFL);
 656 }
 657
 658 /**
 659  * Perform user authentication and execute a command.
 660  *
 661  * \param fd The file descriptor to send output to.
 662  * \param peername Identifies the connecting peer.
 663  *
 664  * Whenever para_server accepts an incoming tcp connection on
 665  * the port it listens on, it forks and the resulting child
 666  * calls this function.
 667  *
 668  * An RSA-based challenge/response is used to authenticate
 669  * the peer. It that authentication succeeds, a random RC4
 670  * session key is generated and sent back to the peer,
 671  * encrypted with its RSA public key.  From this point on,
 672  * all transfers are crypted with this session key.
 673  *
 674  * Next it is checked if the peer supplied  a valid server command or a command
 675  * for the audio file selector.  If yes, and if the user has sufficient
 676  * permissions to execute that command, the function calls the corresponding
 677  * command handler which does argument checking and further processing.
 678  *
 679  * In order to cope with a DOS attacks, a timeout is set up
 680  * which terminates the function if the connection was not
 681  * authenticated when the timeout expires.
 682  *
 683  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 684  */
 685 __noreturn void handle_connect(int fd, const char *peername)
 686 {
 687         int ret, argc, use_rc4 = 0;
 688         char buf[4096];
 689         unsigned char crypt_buf[MAXLINE];
 690         struct user *u;
 691         struct server_command *cmd = NULL;
 692         long unsigned challenge_nr, chall_response;
 693         char **argv = NULL;
 694         char *p, *command = NULL;
 695         size_t numbytes;
 696
 697         reset_signals();
 698         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 699         ret = mark_fd_blocking(fd);
 700         if (ret < 0)
 701                 goto err_out;
 702         challenge_nr = random();
 703         /* send Welcome message */
 704         ret = send_va_buffer(fd, "This is para_server, version "
 705                 PACKAGE_VERSION  ".\n" );
 706         if (ret < 0)
 707                 goto err_out;
 708         /* recv auth request line */
 709         ret = recv_buffer(fd, buf, sizeof(buf));
 710         if (ret < 0)
 711                 goto err_out;
 712         if (ret <= 6) {
 713                 ret = -E_AUTH;
 714                 goto err_out;
 715         }
 716         numbytes = ret;
 717         ret = -E_AUTH;
 718         if (strncmp(buf, "auth ", 5))
 719                 goto err_out;
 720
 721         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 722                 p = buf + 5; /* client version < 0.2.6 */
 723         else {
 724                 p = buf + 9; /* client version >= 0.2.6 */
 725                 use_rc4 = 1;
 726         }
 727         PARA_DEBUG_LOG("received %s request for user %s\n",
 728                 use_rc4? "rc4" : "auth", p);
 729         ret = -E_BAD_USER;
 730         u = lookup_user(p);
 731         if (!u)
 732                 goto err_out;
 733         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 734         if (ret <= 0)
 735                 goto err_out;
 736         numbytes = ret;
 737         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 738         /* We can't use send_buffer here since buf may contain null bytes */
 739         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 740         if (ret < 0)
 741                 goto net_err;
 742         /* recv decrypted number */
 743         ret = recv_buffer(fd, buf, sizeof(buf));
 744         if (ret < 0)
 745                 goto net_err;
 746         numbytes = ret;
 747         ret = -E_AUTH;
 748         if (!numbytes)
 749                 goto net_err;
 750         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 751                         || chall_response != challenge_nr)
 752                 goto err_out;
 753         /* auth successful, send 'Proceed' message */
 754         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 755         sprintf(buf, "%s", PROCEED_MSG);
 756         if (use_rc4) {
 757                 init_rc4_keys();
 758                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 759                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 760                 if (ret <= 0)
 761                         goto err_out;
 762                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 763         } else
 764                 numbytes = strlen(buf);
 765         ret = send_bin_buffer(fd, buf, numbytes);
 766         if (ret < 0)
 767                 goto net_err;
 768         if (use_rc4)
 769                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 770         ret = read_command(fd, &command);
 771         if (ret == -E_COMMAND_SYNTAX)
 772                 goto err_out;
 773         if (ret < 0)
 774                 goto net_err;
 775         ret = -E_BAD_CMD;
 776         cmd = parse_cmd(command);
 777         if (!cmd)
 778                 goto err_out;
 779         /* valid command, check permissions */
 780         ret = check_perms(u->perms, cmd);
 781         if (ret < 0)
 782                 goto err_out;
 783         /* valid command and sufficient perms */
 784         alarm(0);
 785         argc = split_args(command, &argv, "\n");
 786         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 787                         peername);
 788         ret = cmd->handler(fd, argc, argv);
 789         mutex_lock(mmd_mutex);
 790         mmd->num_commands++;
 791         mutex_unlock(mmd_mutex);
 792         if (ret >= 0)
 793                 goto out;
 794 err_out:
 795         send_va_buffer(fd, "%s\n", para_strerror(-ret));
 796 net_err:
 797         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 798 out:
 799         free(command);
 800         free(argv);
 801         mutex_lock(mmd_mutex);
 802         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 803                 mmd->events++;
 804         mmd->active_connections--;
 805         mutex_unlock(mmd_mutex);
 806         exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);
 807 }