command.c

   1 /*
   2  * Copyright (C) 1997-2007 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 "send.h"
  24 #include "rc4.h"
  25 #include "net.h"
  26 #include "daemon.h"
  27 #include "fd.h"
  28 #include "list.h"
  29 #include "user_list.h"
  30 #include "server_command_list.h"
  31 #include "afs_command_list.h"
  32
  33 /** Commands including options must be shorter than this. */
  34 #define MAX_COMMAND_LEN 32768
  35
  36 static RC4_KEY rc4_recv_key;
  37 static RC4_KEY rc4_send_key;
  38 static unsigned char rc4_buf[2 * RC4_KEY_LEN];
  39
  40 extern struct misc_meta_data *mmd;
  41 extern struct sender senders[];
  42
  43 static void dummy(__a_unused int s)
  44 {}
  45
  46 static void mmd_dup(struct misc_meta_data *new_mmd)
  47 {
  48         mmd_lock();
  49         *new_mmd = *mmd;
  50         mmd_unlock();
  51 }
  52
  53 /*
  54  * compute human readable string containing
  55  * vss status for given integer value
  56  */
  57 static char *vss_status_tohuman(unsigned int flags)
  58 {
  59         if (flags & VSS_PLAYING)
  60                 return para_strdup("playing");
  61         else if (flags & VSS_NEXT)
  62                 return para_strdup("stopped");
  63         else
  64                 return para_strdup("paused");
  65 }
  66
  67 /*
  68  * return human readable permission string. Never returns NULL.
  69  */
  70 static char *cmd_perms_itohuman(unsigned int perms)
  71 {
  72         char *msg = para_malloc(5 * sizeof(char));
  73
  74         msg[0] = perms & AFS_READ? 'a' : '-';
  75         msg[1] = perms & AFS_WRITE? 'A' : '-';
  76         msg[2] = perms & VSS_READ? 'v' : '-';
  77         msg[3] = perms & VSS_WRITE? 'V' : '-';
  78         msg[4] = '\0';
  79         return msg;
  80 }
  81
  82 /*
  83  * Never returns NULL.
  84  */
  85 static char *vss_get_status_flags(unsigned int flags)
  86 {
  87         char *msg = para_malloc(5 * sizeof(char));
  88
  89         msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
  90         msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
  91         msg[2] = (flags & VSS_NEXT)? 'N' : '_';
  92         msg[3] = (flags & VSS_REPOS)? 'R' : '_';
  93         msg[4] = '\0';
  94         return msg;
  95 }
  96
  97 static char *get_status(struct misc_meta_data *nmmd)
  98 {
  99         char *ret, mtime[30] = "";
 100         char *status, *flags; /* vss status info */
 101         char *ut = uptime_str();
 102         long offset = (nmmd->offset + 500) / 1000;
 103         struct timeval now;
 104         struct tm mtime_tm;
 105
 106         /* report real status */
 107         status = vss_status_tohuman(nmmd->vss_status_flags);
 108         flags = vss_get_status_flags(nmmd->vss_status_flags);
 109         if (nmmd->size) { /* parent currently has an audio file open */
 110                 localtime_r(&nmmd->mtime, &mtime_tm);
 111                 strftime(mtime, 29, "%a %b %d %Y", &mtime_tm);
 112         }
 113         gettimeofday(&now, NULL);
 114         ret = make_message(
 115                 "%s: %zu\n" /* file size */
 116                 "%s: %s\n" /* mtime */
 117                 "%s: %s\n" /* status */
 118                 "%s: %s\n" /* status flags */
 119                 "%s: %li\n" /* offset */
 120                 "%s: %s\n" /* afs mode */
 121                 "%s: %s\n" /* server uptime */
 122                 "%s: %lu.%lu\n" /* stream start */
 123                 "%s: %lu.%lu\n" /* current server time */
 124                 "%s\n", /* afs status info */
 125                 status_item_list[SI_FILE_SIZE], nmmd->size / 1024,
 126                 status_item_list[SI_MTIME], mtime,
 127                 status_item_list[SI_STATUS], status,
 128                 status_item_list[SI_STATUS_FLAGS], flags,
 129
 130                 status_item_list[SI_OFFSET], offset,
 131                 status_item_list[SI_AFS_MODE], mmd->afs_mode_string,
 132
 133                 status_item_list[SI_UPTIME], ut,
 134                 status_item_list[SI_STREAM_START],
 135                         (long unsigned)nmmd->stream_start.tv_sec,
 136                         (long unsigned)nmmd->stream_start.tv_usec,
 137                 status_item_list[SI_CURRENT_TIME],
 138                         (long unsigned)now.tv_sec,
 139                         (long unsigned)now.tv_usec,
 140
 141                 nmmd->afd.verbose_ls_output
 142
 143         );
 144         free(flags);
 145         free(status);
 146         free(ut);
 147         return ret;
 148 }
 149
 150 static int check_sender_args(int argc, char * const * argv, struct sender_command_data *scd)
 151 {
 152         int i;
 153         /* this has to match sender.h */
 154         const char *subcmds[] = {"add", "delete", "allow", "deny", "on", "off", NULL};
 155
 156         scd->sender_num = -1;
 157         if (argc < 2)
 158                 return -E_COMMAND_SYNTAX;
 159         for (i = 0; senders[i].name; i++)
 160                 if (!strcmp(senders[i].name, argv[1]))
 161                         break;
 162         PARA_DEBUG_LOG("%d:%s\n", argc, argv[1]);
 163         if (!senders[i].name)
 164                 return -E_COMMAND_SYNTAX;
 165         scd->sender_num = i;
 166         for (i = 0; subcmds[i]; i++)
 167                 if (!strcmp(subcmds[i], argv[2]))
 168                         break;
 169         if (!subcmds[i])
 170                 return -E_COMMAND_SYNTAX;
 171         scd->cmd_num = i;
 172         mmd_lock();
 173         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 174                 mmd_unlock();
 175                 return -E_SENDER_CMD;
 176         }
 177         mmd_unlock();
 178         switch (scd->cmd_num) {
 179         case SENDER_ON:
 180         case SENDER_OFF:
 181                 if (argc != 3)
 182                         return -E_COMMAND_SYNTAX;
 183                 break;
 184         case SENDER_DENY:
 185         case SENDER_ALLOW:
 186                 if (argc != 4 && argc != 5)
 187                         return -E_COMMAND_SYNTAX;
 188                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 189                         return -E_COMMAND_SYNTAX;
 190                 scd->netmask = 32;
 191                 if (argc == 5) {
 192                         scd->netmask = atoi(argv[4]);
 193                         if (scd->netmask < 0 || scd->netmask > 32)
 194                                 return -E_COMMAND_SYNTAX;
 195                 }
 196                 break;
 197         case SENDER_ADD:
 198         case SENDER_DELETE:
 199                 if (argc != 4 && argc != 5)
 200                         return -E_COMMAND_SYNTAX;
 201                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 202                         return -E_COMMAND_SYNTAX;
 203                 scd->port = -1;
 204                 if (argc == 5) {
 205                         scd->port = atoi(argv[4]);
 206                         if (scd->port < 0 || scd->port > 65535)
 207                                 return -E_COMMAND_SYNTAX;
 208                 }
 209                 break;
 210         default:
 211                 return -E_COMMAND_SYNTAX;
 212         }
 213         return 1;
 214 }
 215
 216 int com_sender(int fd, int argc, char * const * argv)
 217 {
 218         int i, ret;
 219         struct sender_command_data scd;
 220
 221         if (argc < 2) {
 222                 char *msg = NULL;
 223                 for (i = 0; senders[i].name; i++) {
 224                         char *tmp = make_message("%s%s\n",
 225                                 msg? msg : "", senders[i].name);
 226                         free(msg);
 227                         msg = tmp;
 228                 }
 229                 ret = send_buffer(fd, msg);
 230                 free(msg);
 231                 return ret;
 232         }
 233         ret = check_sender_args(argc, argv, &scd);
 234         if (ret < 0) {
 235                 char *msg;
 236                 if (scd.sender_num < 0)
 237                         return ret;
 238                 msg = senders[scd.sender_num].help();
 239                 send_buffer(fd, msg);
 240                 free(msg);
 241                 return 1;
 242         }
 243         for (i = 0; i < 10; i++) {
 244                 mmd_lock();
 245                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 246                         mmd_unlock();
 247                         usleep(100 * 1000);
 248                         continue;
 249                 }
 250                 mmd->sender_cmd_data = scd;
 251                 mmd_unlock();
 252                 break;
 253         }
 254         return (i < 10)? 1 : -E_LOCK;
 255 }
 256
 257 /* server info */
 258 int com_si(int fd, int argc, __a_unused char * const * argv)
 259 {
 260         int i, ret;
 261         char *ut;
 262         char *sender_info = NULL, *sender_list = NULL;
 263
 264         if (argc != 1)
 265                 return -E_COMMAND_SYNTAX;
 266         mmd_lock();
 267         for (i = 0; senders[i].name; i++) {
 268                 char *info = senders[i].info();
 269                 sender_info = para_strcat(sender_info, info);
 270                 free(info);
 271                 sender_list = para_strcat(sender_list, senders[i].name);
 272                 sender_list = para_strcat(sender_list, " ");
 273         }
 274         ut = uptime_str();
 275         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 276                 "pid: %d\n"
 277                 "connections (active/accepted/total): %u/%u/%u\n"
 278                 "current loglevel: %i\n"
 279                 "supported audio formats: %s\n"
 280                 "supported senders: %s\n"
 281                 "%s",
 282                 ut, mmd->num_played,
 283                 getppid(),
 284                 mmd->active_connections,
 285                 mmd->num_commands,
 286                 mmd->num_connects,
 287                 conf.loglevel_arg,
 288                 supported_audio_formats(),
 289                 sender_list,
 290                 sender_info
 291         );
 292         mmd_unlock();
 293         free(ut);
 294         free(sender_list);
 295         free(sender_info);
 296         return ret;
 297 }
 298
 299 /* version */
 300 int com_version(int fd, int argc, __a_unused char * const * argv)
 301 {
 302         if (argc != 1)
 303                 return -E_COMMAND_SYNTAX;
 304         return send_buffer(fd, VERSION_TEXT("server")
 305                 "built: " BUILD_DATE "\n"
 306                 SYSTEM ", " CC_VERSION "\n"
 307         );
 308 }
 309
 310 /* stat */
 311 int com_stat(int fd, int argc, char * const * argv)
 312 {
 313         int ret, num = 0;/* status will be printed that many
 314                           * times. num <= 0 means: print forever
 315                           */
 316         struct misc_meta_data tmp, *nmmd = &tmp;
 317         char *s;
 318
 319         signal(SIGUSR1, dummy);
 320
 321         if (argc > 1)
 322                 num = atoi(argv[1]);
 323         for (;;) {
 324
 325                 mmd_dup(nmmd);
 326                 s = get_status(nmmd);
 327                 ret = send_buffer(fd, s);
 328                 free(s);
 329                 if (ret < 0)
 330                         goto out;
 331                 ret = 1;
 332                 if (num == 1)
 333                         goto out;
 334                 sleep(50);
 335                 if (getppid() == 1)
 336                         return -E_SERVER_CRASH;
 337         }
 338 out:
 339         return ret;
 340 }
 341
 342 static int send_list_of_commands(int fd, struct server_command *cmd,
 343                 const char *handler)
 344 {
 345         int ret, i;
 346
 347         for (i = 1; cmd->name; cmd++, i++) {
 348                 char *perms = cmd_perms_itohuman(cmd->perms);
 349                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 350                         handler,
 351                         perms,
 352                         cmd->description);
 353                 free(perms);
 354                 if (ret < 0)
 355                         return ret;
 356         }
 357         return 1;
 358 }
 359
 360 /* returns string that must be freed by the caller */
 361 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 362 {
 363         struct server_command *cmd;
 364
 365         for (cmd = server_cmds; cmd->name; cmd++)
 366                 if (!strcmp(cmd->name, name)) {
 367                         if (handler)
 368                                 *handler = para_strdup("server"); /* server commands */
 369                         return cmd;
 370                 }
 371         /* not found, look for commands supported by afs */
 372         for (cmd = afs_cmds; cmd->name; cmd++)
 373                 if (!strcmp(cmd->name, name)) {
 374                         if (handler)
 375                                 *handler = para_strdup("afs");
 376                         return cmd;
 377                 }
 378         return NULL;
 379 }
 380
 381 /* help */
 382 int com_help(int fd, int argc, char * const * argv)
 383 {
 384         struct server_command *cmd;
 385         char *perms, *handler;
 386         int ret;
 387
 388         if (argc < 2) {
 389                 /* no argument given, print list of commands */
 390                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 391                         return ret;
 392                 return send_list_of_commands(fd, afs_cmds, "afs");
 393         }
 394         /* argument given for help */
 395         cmd = get_cmd_ptr(argv[1], &handler);
 396         if (!cmd) {
 397                 free(handler);
 398                 return -E_BAD_CMD;
 399         }
 400         perms = cmd_perms_itohuman(cmd->perms);
 401         ret = send_va_buffer(fd,
 402                 "%s - %s\n\n"
 403                 "handler: %s\n"
 404                 "permissions: %s\n"
 405                 "usage: %s\n\n"
 406                 "%s\n",
 407                 argv[1],
 408                 cmd->description,
 409                 handler,
 410                 perms,
 411                 cmd->usage,
 412                 cmd->help
 413         );
 414         free(perms);
 415         free(handler);
 416         return ret;
 417 }
 418
 419 /* hup */
 420 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 421 {
 422         if (argc != 1)
 423                 return -E_COMMAND_SYNTAX;
 424         kill(getppid(), SIGHUP);
 425         return 1;
 426 }
 427
 428 /* term */
 429 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 430 {
 431         if (argc != 1)
 432                 return -E_COMMAND_SYNTAX;
 433         kill(getppid(), SIGTERM);
 434         return 1;
 435 }
 436
 437 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 438 {
 439         if (argc != 1)
 440                 return -E_COMMAND_SYNTAX;
 441         mmd_lock();
 442         mmd->new_vss_status_flags |= VSS_PLAYING;
 443         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 444         mmd_unlock();
 445         return 1;
 446
 447 }
 448
 449 /* stop */
 450 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 451 {
 452         if (argc != 1)
 453                 return -E_COMMAND_SYNTAX;
 454         mmd_lock();
 455         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 456         mmd->new_vss_status_flags &= ~VSS_REPOS;
 457         mmd->new_vss_status_flags |= VSS_NEXT;
 458         mmd_unlock();
 459         return 1;
 460 }
 461
 462 /* pause */
 463 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 464 {
 465         if (argc != 1)
 466                 return -E_COMMAND_SYNTAX;
 467         mmd_lock();
 468         if (!vss_paused())
 469                 mmd->events++;
 470         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 471         mmd->new_vss_status_flags &= ~VSS_NEXT;
 472         mmd_unlock();
 473         return 1;
 474 }
 475
 476 /* next */
 477 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 478 {
 479         if (argc != 1)
 480                 return -E_COMMAND_SYNTAX;
 481         mmd_lock();
 482         mmd->events++;
 483         mmd->new_vss_status_flags |= VSS_NEXT;
 484         mmd_unlock();
 485         return 1;
 486 }
 487
 488 /* nomore */
 489 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 490 {
 491         if (argc != 1)
 492                 return -E_COMMAND_SYNTAX;
 493         mmd_lock();
 494         if (vss_playing() || vss_paused())
 495                 mmd->new_vss_status_flags |= VSS_NOMORE;
 496         mmd_unlock();
 497         return 1;
 498 }
 499
 500 /* ff */
 501 int com_ff(__a_unused int fd, int argc, char * const * argv)
 502 {
 503         long promille;
 504         int ret, backwards = 0;
 505         unsigned i;
 506         char c;
 507
 508         if (argc != 2)
 509                 return -E_COMMAND_SYNTAX;
 510         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 511                 return -E_COMMAND_SYNTAX;
 512         if (ret > 1 && c == '-')
 513                 backwards = 1; /* jmp backwards */
 514         mmd_lock();
 515         ret = -E_NO_AUDIO_FILE;
 516         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 517                 goto out;
 518         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 519         if (backwards)
 520                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 521         else
 522                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 523         if (promille < 0)
 524                 promille = 0;
 525         if (promille >  1000) {
 526                 mmd->new_vss_status_flags |= VSS_NEXT;
 527                 goto out;
 528         }
 529         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 530         mmd->new_vss_status_flags |= VSS_REPOS;
 531         mmd->new_vss_status_flags &= ~VSS_NEXT;
 532         mmd->events++;
 533         ret = 1;
 534 out:
 535         mmd_unlock();
 536         return ret;
 537 }
 538
 539 /* jmp */
 540 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 541 {
 542         long unsigned int i;
 543         int ret;
 544
 545         if (argc != 2)
 546                 return -E_COMMAND_SYNTAX;
 547         if (sscanf(argv[1], "%lu", &i) <= 0)
 548                 return -E_COMMAND_SYNTAX;
 549         mmd_lock();
 550         ret = -E_NO_AUDIO_FILE;
 551         if (!mmd->afd.afhi.chunks_total)
 552                 goto out;
 553         if (i > 100)
 554                 i = 100;
 555         PARA_INFO_LOG("jumping to %lu%%\n", i);
 556         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 557         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 558                 mmd->chunks_sent, mmd->offset);
 559         mmd->new_vss_status_flags |= VSS_REPOS;
 560         mmd->new_vss_status_flags &= ~VSS_NEXT;
 561         ret = 1;
 562         mmd->events++;
 563 out:
 564         mmd_unlock();
 565         return ret;
 566 }
 567
 568 /*
 569  * check if perms are sufficient to exec a command having perms cmd_perms.
 570  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 571  */
 572 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 573 {
 574         PARA_DEBUG_LOG("%s", "checking permissions\n");
 575         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 576 }
 577
 578 /*
 579  * Parse first string from *cmd and lookup in table of valid commands.
 580  * On error, NULL is returned.
 581  */
 582 static struct server_command *parse_cmd(const char *cmdstr)
 583 {
 584         char buf[255];
 585         int n = 0;
 586
 587         sscanf(cmdstr, "%200s%n", buf, &n);
 588         if (!n)
 589                 return NULL;
 590         buf[n] = '\0';
 591         return get_cmd_ptr(buf, NULL);
 592 }
 593
 594 static void init_rc4_keys(void)
 595 {
 596         int i;
 597
 598         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 599                 rc4_buf[i] = para_random(256);
 600         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 601                 (unsigned char) rc4_buf[0],
 602                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 603         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 604         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 605 }
 606
 607 static void rc4_recv(unsigned long len, const unsigned char *indata,
 608                 unsigned char *outdata, __a_unused void *private_data)
 609 {
 610         RC4(&rc4_recv_key, len, indata, outdata);
 611 }
 612
 613 static void rc4_send(unsigned long len, const unsigned char *indata,
 614                 unsigned char *outdata, __a_unused void *private_data)
 615 {
 616         RC4(&rc4_send_key, len, indata, outdata);
 617 }
 618
 619 static int read_command(int fd, char **result)
 620 {
 621         int ret;
 622         char buf[4096];
 623         char *command = NULL;
 624
 625         for (;;) {
 626                 size_t numbytes;
 627                 char *p;
 628
 629                 ret = recv_buffer(fd, buf, sizeof(buf));
 630                 if (ret < 0)
 631                         goto out;
 632                 if (!ret)
 633                         break;
 634                 numbytes = ret;
 635                 ret = -E_COMMAND_SYNTAX;
 636                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 637                         goto out;
 638                 command = para_strcat(command, buf);
 639                 p = strstr(command, EOC_MSG);
 640                 if (p) {
 641                         *p = '\0';
 642                         break;
 643                 }
 644         }
 645         ret = command? 1 : -E_COMMAND_SYNTAX;
 646 out:
 647         if (ret < 0)
 648                 free(command);
 649         else
 650                 *result = command;
 651         return ret;
 652
 653 }
 654
 655 /**
 656  * perform user authentication and execute a command
 657  *
 658  * \param fd the file descriptor to send output to
 659  * \param addr socket address info of peer
 660  *
 661  * \return EXIT_SUCCESS or EXIT_FAILURE
 662  *
 663  * Whenever para_server accepts an incoming tcp connection on
 664  * the port it listens on, it forks and the resulting child
 665  * calls this function.
 666  *
 667  * An RSA-based challenge/response is used to authenticate
 668  * the peer. It that authentication succeeds, a random RC4
 669  * session key is generated and sent back to the peer,
 670  * encrypted with its RSA public key.  From this point on,
 671  * all transfers are crypted with this session key.
 672  *
 673  * Next it is checked if the peer supplied  a valid server command or a command
 674  * for the audio file selector.  If yes, and if the user has sufficient
 675  * permissions to execute that command, the function calls the corresponding
 676  * command handler which does argument checking and further processing.
 677  *
 678  * In order to cope with a DOS attacks, a timeout is set up
 679  * which terminates the function if the connection was not
 680  * authenticated when the timeout expires.
 681  *
 682  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 683  */
 684 int handle_connect(int fd, struct sockaddr_in *addr)
 685 {
 686         int ret, argc, use_rc4 = 0;
 687         char buf[4096];
 688         unsigned char crypt_buf[MAXLINE];
 689         struct user *u;
 690         struct server_command *cmd = NULL;
 691         long unsigned challenge_nr, chall_response;
 692         char **argv = NULL;
 693         char *p, *command = NULL;
 694         size_t numbytes;
 695
 696         signal(SIGCHLD, SIG_IGN);
 697         signal(SIGINT, SIG_DFL);
 698         signal(SIGTERM, SIG_DFL);
 699         signal(SIGHUP, SIG_DFL);
 700         signal(SIGUSR1, SIG_IGN);
 701
 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 err_out;
 742         /* recv decrypted number */
 743         ret = recv_buffer(fd, buf, sizeof(buf));
 744         if (ret < 0)
 745                 goto err_out;
 746         numbytes = ret;
 747         ret = -E_AUTH;
 748         if (!numbytes)
 749                 goto err_out;
 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 err_out;
 768         if (use_rc4)
 769                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 770         ret = read_command(fd, &command);
 771         if (ret < 0)
 772                 goto err_out;
 773         ret = -E_BAD_CMD;
 774         cmd = parse_cmd(command);
 775         if (!cmd)
 776                 goto err_out;
 777         /* valid command, check permissions */
 778         ret = check_perms(u->perms, cmd);
 779         if (ret < 0)
 780                 goto err_out;
 781         /* valid command and sufficient perms */
 782         alarm(0);
 783         argc = split_args(command, &argv, "\n");
 784         mmd_lock();
 785         mmd->num_commands++;
 786         mmd_unlock();
 787         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 788                 inet_ntoa(addr->sin_addr));
 789         ret = cmd->handler(fd, argc, argv);
 790         if (ret >= 0) {
 791                 ret = EXIT_SUCCESS;
 792                 goto out;
 793         }
 794 err_out:
 795         PARA_NOTICE_LOG("%s\n", PARA_STRERROR(-ret));
 796         if (ret != -E_SEND && ret != -E_RECV)
 797                 send_va_buffer(fd, "%s\n", PARA_STRERROR(-ret));
 798         ret = EXIT_FAILURE;
 799 out:
 800         free(command);
 801         free(argv);
 802         mmd_lock();
 803         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 804                 mmd->events++;
 805         mmd->active_connections--;
 806         mmd_unlock();
 807         return ret;
 808 }