command.c

   1 /*
   2  * Copyright (C) 1997-2008 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 "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(int s)
  44 {
  45         /*
  46          * At least on Solaris, SIGUSR1 is one-shot, i.e. the signal action is
  47          * restored to the default state once the signal handler has been
  48          * called.
  49          */
  50         if (s == SIGUSR1)
  51                 signal(SIGUSR1, dummy);
  52 }
  53
  54 static void mmd_dup(struct misc_meta_data *new_mmd)
  55 {
  56         mmd_lock();
  57         *new_mmd = *mmd;
  58         mmd_unlock();
  59 }
  60
  61 /*
  62  * compute human readable string containing
  63  * vss status for given integer value
  64  */
  65 static char *vss_status_tohuman(unsigned int flags)
  66 {
  67         if (flags & VSS_PLAYING)
  68                 return para_strdup("playing");
  69         else if (flags & VSS_NEXT)
  70                 return para_strdup("stopped");
  71         else
  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 now;
 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(&now, 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)now.tv_sec,
 145                         (long unsigned)now.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         mmd_lock();
 179         if (!senders[scd->sender_num].client_cmds[scd->cmd_num]) {
 180                 mmd_unlock();
 181                 return -E_SENDER_CMD;
 182         }
 183         mmd_unlock();
 184         switch (scd->cmd_num) {
 185         case SENDER_ON:
 186         case SENDER_OFF:
 187                 if (argc != 3)
 188                         return -E_COMMAND_SYNTAX;
 189                 break;
 190         case SENDER_DENY:
 191         case SENDER_ALLOW:
 192                 if (argc != 4 && argc != 5)
 193                         return -E_COMMAND_SYNTAX;
 194                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 195                         return -E_COMMAND_SYNTAX;
 196                 scd->netmask = 32;
 197                 if (argc == 5) {
 198                         scd->netmask = atoi(argv[4]);
 199                         if (scd->netmask < 0 || scd->netmask > 32)
 200                                 return -E_COMMAND_SYNTAX;
 201                 }
 202                 break;
 203         case SENDER_ADD:
 204         case SENDER_DELETE:
 205                 if (argc != 4 && argc != 5)
 206                         return -E_COMMAND_SYNTAX;
 207                 if (!inet_pton(AF_INET, argv[3], &scd->addr))
 208                         return -E_COMMAND_SYNTAX;
 209                 scd->port = -1;
 210                 if (argc == 5) {
 211                         scd->port = atoi(argv[4]);
 212                         if (scd->port < 0 || scd->port > 65535)
 213                                 return -E_COMMAND_SYNTAX;
 214                 }
 215                 break;
 216         default:
 217                 return -E_COMMAND_SYNTAX;
 218         }
 219         return 1;
 220 }
 221
 222 int com_sender(int fd, int argc, char * const * argv)
 223 {
 224         int i, ret;
 225         struct sender_command_data scd;
 226
 227         if (argc < 2) {
 228                 char *msg = NULL;
 229                 for (i = 0; senders[i].name; i++) {
 230                         char *tmp = make_message("%s%s\n",
 231                                 msg? msg : "", senders[i].name);
 232                         free(msg);
 233                         msg = tmp;
 234                 }
 235                 ret = send_buffer(fd, msg);
 236                 free(msg);
 237                 return ret;
 238         }
 239         ret = check_sender_args(argc, argv, &scd);
 240         if (ret < 0) {
 241                 char *msg;
 242                 if (scd.sender_num < 0)
 243                         return ret;
 244                 msg = senders[scd.sender_num].help();
 245                 ret = send_buffer(fd, msg);
 246                 free(msg);
 247                 return ret;
 248         }
 249         for (i = 0; i < 10; i++) {
 250                 mmd_lock();
 251                 if (mmd->sender_cmd_data.cmd_num >= 0) {
 252                         mmd_unlock();
 253                         usleep(100 * 1000);
 254                         continue;
 255                 }
 256                 mmd->sender_cmd_data = scd;
 257                 mmd_unlock();
 258                 break;
 259         }
 260         return (i < 10)? 1 : -E_LOCK;
 261 }
 262
 263 /* server info */
 264 int com_si(int fd, int argc, __a_unused char * const * argv)
 265 {
 266         int i, ret;
 267         char *ut;
 268         char *sender_info = NULL, *sender_list = NULL;
 269
 270         if (argc != 1)
 271                 return -E_COMMAND_SYNTAX;
 272         mmd_lock();
 273         for (i = 0; senders[i].name; i++) {
 274                 char *info = senders[i].info();
 275                 sender_info = para_strcat(sender_info, info);
 276                 free(info);
 277                 sender_list = para_strcat(sender_list, senders[i].name);
 278                 sender_list = para_strcat(sender_list, " ");
 279         }
 280         ut = uptime_str();
 281         ret = send_va_buffer(fd, "up: %s\nplayed: %u\n"
 282                 "pid: %d\n"
 283                 "connections (active/accepted/total): %u/%u/%u\n"
 284                 "current loglevel: %i\n"
 285                 "supported audio formats: %s\n"
 286                 "supported senders: %s\n"
 287                 "%s",
 288                 ut, mmd->num_played,
 289                 (int)getppid(),
 290                 mmd->active_connections,
 291                 mmd->num_commands,
 292                 mmd->num_connects,
 293                 conf.loglevel_arg,
 294                 supported_audio_formats(),
 295                 sender_list,
 296                 sender_info
 297         );
 298         mmd_unlock();
 299         free(ut);
 300         free(sender_list);
 301         free(sender_info);
 302         return ret;
 303 }
 304
 305 /* version */
 306 int com_version(int fd, int argc, __a_unused char * const * argv)
 307 {
 308         if (argc != 1)
 309                 return -E_COMMAND_SYNTAX;
 310         return send_buffer(fd, VERSION_TEXT("server")
 311                 "built: " BUILD_DATE "\n"
 312                 UNAME_RS ", " CC_VERSION "\n"
 313         );
 314 }
 315
 316 /* stat */
 317 int com_stat(int fd, int argc, char * const * argv)
 318 {
 319         int ret, num = 0;/* status will be printed that many
 320                           * times. num <= 0 means: print forever
 321                           */
 322         struct misc_meta_data tmp, *nmmd = &tmp;
 323         char *s;
 324
 325         signal(SIGUSR1, dummy);
 326
 327         if (argc > 1)
 328                 num = atoi(argv[1]);
 329         for (;;) {
 330
 331                 mmd_dup(nmmd);
 332                 s = get_status(nmmd);
 333                 ret = send_buffer(fd, s);
 334                 free(s);
 335                 if (ret < 0)
 336                         goto out;
 337                 ret = 1;
 338                 if (num == 1)
 339                         goto out;
 340                 sleep(50);
 341                 if (getppid() == 1)
 342                         return -E_SERVER_CRASH;
 343         }
 344 out:
 345         return ret;
 346 }
 347
 348 static int send_list_of_commands(int fd, struct server_command *cmd,
 349                 const char *handler)
 350 {
 351         int ret, i;
 352
 353         for (i = 1; cmd->name; cmd++, i++) {
 354                 char *perms = cmd_perms_itohuman(cmd->perms);
 355                 ret = send_va_buffer(fd, "%s\t%s\t%s\t%s\n", cmd->name,
 356                         handler,
 357                         perms,
 358                         cmd->description);
 359                 free(perms);
 360                 if (ret < 0)
 361                         return ret;
 362         }
 363         return 1;
 364 }
 365
 366 /* returns string that must be freed by the caller */
 367 static struct server_command *get_cmd_ptr(const char *name, char **handler)
 368 {
 369         struct server_command *cmd;
 370
 371         for (cmd = server_cmds; cmd->name; cmd++)
 372                 if (!strcmp(cmd->name, name)) {
 373                         if (handler)
 374                                 *handler = para_strdup("server"); /* server commands */
 375                         return cmd;
 376                 }
 377         /* not found, look for commands supported by afs */
 378         for (cmd = afs_cmds; cmd->name; cmd++)
 379                 if (!strcmp(cmd->name, name)) {
 380                         if (handler)
 381                                 *handler = para_strdup("afs");
 382                         return cmd;
 383                 }
 384         return NULL;
 385 }
 386
 387 /* help */
 388 int com_help(int fd, int argc, char * const * argv)
 389 {
 390         struct server_command *cmd;
 391         char *perms, *handler;
 392         int ret;
 393
 394         if (argc < 2) {
 395                 /* no argument given, print list of commands */
 396                 if ((ret = send_list_of_commands(fd, server_cmds, "server")) < 0)
 397                         return ret;
 398                 return send_list_of_commands(fd, afs_cmds, "afs");
 399         }
 400         /* argument given for help */
 401         cmd = get_cmd_ptr(argv[1], &handler);
 402         if (!cmd) {
 403                 free(handler);
 404                 return -E_BAD_CMD;
 405         }
 406         perms = cmd_perms_itohuman(cmd->perms);
 407         ret = send_va_buffer(fd,
 408                 "%s - %s\n\n"
 409                 "handler: %s\n"
 410                 "permissions: %s\n"
 411                 "usage: %s\n\n"
 412                 "%s\n",
 413                 argv[1],
 414                 cmd->description,
 415                 handler,
 416                 perms,
 417                 cmd->usage,
 418                 cmd->help
 419         );
 420         free(perms);
 421         free(handler);
 422         return ret;
 423 }
 424
 425 /* hup */
 426 int com_hup(__a_unused int fd, int argc, __a_unused char * const * argv)
 427 {
 428         if (argc != 1)
 429                 return -E_COMMAND_SYNTAX;
 430         kill(getppid(), SIGHUP);
 431         return 1;
 432 }
 433
 434 /* term */
 435 int com_term(__a_unused int fd, int argc, __a_unused char * const * argv)
 436 {
 437         if (argc != 1)
 438                 return -E_COMMAND_SYNTAX;
 439         kill(getppid(), SIGTERM);
 440         return 1;
 441 }
 442
 443 int com_play(__a_unused int fd, int argc, __a_unused char * const * argv)
 444 {
 445         if (argc != 1)
 446                 return -E_COMMAND_SYNTAX;
 447         mmd_lock();
 448         mmd->new_vss_status_flags |= VSS_PLAYING;
 449         mmd->new_vss_status_flags &= ~VSS_NOMORE;
 450         mmd_unlock();
 451         return 1;
 452
 453 }
 454
 455 /* stop */
 456 int com_stop(__a_unused int fd, int argc, __a_unused char * const * argv)
 457 {
 458         if (argc != 1)
 459                 return -E_COMMAND_SYNTAX;
 460         mmd_lock();
 461         mmd->new_vss_status_flags &= ~VSS_PLAYING;
 462         mmd->new_vss_status_flags &= ~VSS_REPOS;
 463         mmd->new_vss_status_flags |= VSS_NEXT;
 464         mmd_unlock();
 465         return 1;
 466 }
 467
 468 /* pause */
 469 int com_pause(__a_unused int fd, int argc, __a_unused char * const * argv)
 470 {
 471         if (argc != 1)
 472                 return -E_COMMAND_SYNTAX;
 473         mmd_lock();
 474         if (!vss_paused() && !vss_stopped()) {
 475                 mmd->events++;
 476                 mmd->new_vss_status_flags &= ~VSS_PLAYING;
 477                 mmd->new_vss_status_flags &= ~VSS_NEXT;
 478         }
 479         mmd_unlock();
 480         return 1;
 481 }
 482
 483 /* next */
 484 int com_next(__a_unused int fd, int argc, __a_unused char * const * argv)
 485 {
 486         if (argc != 1)
 487                 return -E_COMMAND_SYNTAX;
 488         mmd_lock();
 489         mmd->events++;
 490         mmd->new_vss_status_flags |= VSS_NEXT;
 491         mmd_unlock();
 492         return 1;
 493 }
 494
 495 /* nomore */
 496 int com_nomore(__a_unused int fd, int argc, __a_unused char * const * argv)
 497 {
 498         if (argc != 1)
 499                 return -E_COMMAND_SYNTAX;
 500         mmd_lock();
 501         if (vss_playing() || vss_paused())
 502                 mmd->new_vss_status_flags |= VSS_NOMORE;
 503         mmd_unlock();
 504         return 1;
 505 }
 506
 507 /* ff */
 508 int com_ff(__a_unused int fd, int argc, char * const * argv)
 509 {
 510         long promille;
 511         int ret, backwards = 0;
 512         unsigned i;
 513         char c;
 514
 515         if (argc != 2)
 516                 return -E_COMMAND_SYNTAX;
 517         if (!(ret = sscanf(argv[1], "%u%c", &i, &c)))
 518                 return -E_COMMAND_SYNTAX;
 519         if (ret > 1 && c == '-')
 520                 backwards = 1; /* jmp backwards */
 521         mmd_lock();
 522         ret = -E_NO_AUDIO_FILE;
 523         if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
 524                 goto out;
 525         promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
 526         if (backwards)
 527                 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
 528         else
 529                 promille += 1000 * i / mmd->afd.afhi.seconds_total;
 530         if (promille < 0)
 531                 promille = 0;
 532         if (promille >  1000) {
 533                 mmd->new_vss_status_flags |= VSS_NEXT;
 534                 goto out;
 535         }
 536         mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
 537         mmd->new_vss_status_flags |= VSS_REPOS;
 538         mmd->new_vss_status_flags &= ~VSS_NEXT;
 539         mmd->events++;
 540         ret = 1;
 541 out:
 542         mmd_unlock();
 543         return ret;
 544 }
 545
 546 /* jmp */
 547 int com_jmp(__a_unused int fd, int argc, char * const * argv)
 548 {
 549         long unsigned int i;
 550         int ret;
 551
 552         if (argc != 2)
 553                 return -E_COMMAND_SYNTAX;
 554         if (sscanf(argv[1], "%lu", &i) <= 0)
 555                 return -E_COMMAND_SYNTAX;
 556         mmd_lock();
 557         ret = -E_NO_AUDIO_FILE;
 558         if (!mmd->afd.afhi.chunks_total)
 559                 goto out;
 560         if (i > 100)
 561                 i = 100;
 562         PARA_INFO_LOG("jumping to %lu%%\n", i);
 563         mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50)/ 100;
 564         PARA_INFO_LOG("sent: %lu,  offset before jmp: %lu\n",
 565                 mmd->chunks_sent, mmd->offset);
 566         mmd->new_vss_status_flags |= VSS_REPOS;
 567         mmd->new_vss_status_flags &= ~VSS_NEXT;
 568         ret = 1;
 569         mmd->events++;
 570 out:
 571         mmd_unlock();
 572         return ret;
 573 }
 574
 575 /*
 576  * check if perms are sufficient to exec a command having perms cmd_perms.
 577  * Returns 0 if perms are sufficient, -E_PERM otherwise.
 578  */
 579 static int check_perms(unsigned int perms, struct server_command *cmd_ptr)
 580 {
 581         PARA_DEBUG_LOG("checking permissions\n");
 582         return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
 583 }
 584
 585 /*
 586  * Parse first string from *cmd and lookup in table of valid commands.
 587  * On error, NULL is returned.
 588  */
 589 static struct server_command *parse_cmd(const char *cmdstr)
 590 {
 591         char buf[255];
 592         int n = 0;
 593
 594         sscanf(cmdstr, "%200s%n", buf, &n);
 595         if (!n)
 596                 return NULL;
 597         buf[n] = '\0';
 598         return get_cmd_ptr(buf, NULL);
 599 }
 600
 601 static void init_rc4_keys(void)
 602 {
 603         int i;
 604
 605         for (i = 0; i < 2 * RC4_KEY_LEN; i++)
 606                 rc4_buf[i] = para_random(256);
 607         PARA_DEBUG_LOG("rc4 keys initialized (%u:%u)\n",
 608                 (unsigned char) rc4_buf[0],
 609                 (unsigned char) rc4_buf[RC4_KEY_LEN]);
 610         RC4_set_key(&rc4_recv_key, RC4_KEY_LEN, rc4_buf);
 611         RC4_set_key(&rc4_send_key, RC4_KEY_LEN, rc4_buf + RC4_KEY_LEN);
 612 }
 613
 614 static void rc4_recv(unsigned long len, const unsigned char *indata,
 615                 unsigned char *outdata, __a_unused void *private_data)
 616 {
 617         RC4(&rc4_recv_key, len, indata, outdata);
 618 }
 619
 620 static void rc4_send(unsigned long len, const unsigned char *indata,
 621                 unsigned char *outdata, __a_unused void *private_data)
 622 {
 623         RC4(&rc4_send_key, len, indata, outdata);
 624 }
 625
 626 static int read_command(int fd, char **result)
 627 {
 628         int ret;
 629         char buf[4096];
 630         char *command = NULL;
 631
 632         for (;;) {
 633                 size_t numbytes;
 634                 char *p;
 635
 636                 ret = recv_buffer(fd, buf, sizeof(buf));
 637                 if (ret < 0)
 638                         goto out;
 639                 if (!ret)
 640                         break;
 641                 numbytes = ret;
 642                 ret = -E_COMMAND_SYNTAX;
 643                 if (command && numbytes + strlen(command) > MAX_COMMAND_LEN) /* DOS */
 644                         goto out;
 645                 command = para_strcat(command, buf);
 646                 p = strstr(command, EOC_MSG);
 647                 if (p) {
 648                         *p = '\0';
 649                         break;
 650                 }
 651         }
 652         ret = command? 1 : -E_COMMAND_SYNTAX;
 653 out:
 654         if (ret < 0)
 655                 free(command);
 656         else
 657                 *result = command;
 658         return ret;
 659
 660 }
 661
 662 /**
 663  * perform user authentication and execute a command
 664  *
 665  * \param fd        The file descriptor to send output to
 666  * \param peername  Identifies the connecting peer.
 667  *
 668  * \return EXIT_SUCCESS or EXIT_FAILURE
 669  *
 670  * Whenever para_server accepts an incoming tcp connection on
 671  * the port it listens on, it forks and the resulting child
 672  * calls this function.
 673  *
 674  * An RSA-based challenge/response is used to authenticate
 675  * the peer. It that authentication succeeds, a random RC4
 676  * session key is generated and sent back to the peer,
 677  * encrypted with its RSA public key.  From this point on,
 678  * all transfers are crypted with this session key.
 679  *
 680  * Next it is checked if the peer supplied  a valid server command or a command
 681  * for the audio file selector.  If yes, and if the user has sufficient
 682  * permissions to execute that command, the function calls the corresponding
 683  * command handler which does argument checking and further processing.
 684  *
 685  * In order to cope with a DOS attacks, a timeout is set up
 686  * which terminates the function if the connection was not
 687  * authenticated when the timeout expires.
 688  *
 689  * \sa alarm(2), rc4(3), crypt.c, crypt.h
 690  */
 691 int handle_connect(int fd, const char *peername)
 692 {
 693         int ret, argc, use_rc4 = 0;
 694         char buf[4096];
 695         unsigned char crypt_buf[MAXLINE];
 696         struct user *u;
 697         struct server_command *cmd = NULL;
 698         long unsigned challenge_nr, chall_response;
 699         char **argv = NULL;
 700         char *p, *command = NULL;
 701         size_t numbytes;
 702
 703         signal(SIGCHLD, SIG_IGN);
 704         signal(SIGINT, SIG_DFL);
 705         signal(SIGTERM, SIG_DFL);
 706         signal(SIGHUP, SIG_DFL);
 707
 708         /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
 709         ret = mark_fd_blocking(fd);
 710         if (ret < 0)
 711                 goto err_out;
 712         challenge_nr = random();
 713         /* send Welcome message */
 714         ret = send_va_buffer(fd, "This is para_server, version "
 715                 PACKAGE_VERSION  ".\n" );
 716         if (ret < 0)
 717                 goto err_out;
 718         /* recv auth request line */
 719         ret = recv_buffer(fd, buf, sizeof(buf));
 720         if (ret < 0)
 721                 goto err_out;
 722         if (ret <= 6) {
 723                 ret = -E_AUTH;
 724                 goto err_out;
 725         }
 726         numbytes = ret;
 727         ret = -E_AUTH;
 728         if (strncmp(buf, "auth ", 5))
 729                 goto err_out;
 730
 731         if (numbytes < 9 || strncmp(buf, "auth rc4 ", 9))
 732                 p = buf + 5; /* client version < 0.2.6 */
 733         else {
 734                 p = buf + 9; /* client version >= 0.2.6 */
 735                 use_rc4 = 1;
 736         }
 737         PARA_DEBUG_LOG("received %s request for user %s\n",
 738                 use_rc4? "rc4" : "auth", p);
 739         ret = -E_BAD_USER;
 740         u = lookup_user(p);
 741         if (!u)
 742                 goto err_out;
 743         ret = para_encrypt_challenge(u->rsa, challenge_nr, crypt_buf);
 744         if (ret <= 0)
 745                 goto err_out;
 746         numbytes = ret;
 747         PARA_DEBUG_LOG("sending %zu byte challenge\n", numbytes);
 748         /* We can't use send_buffer here since buf may contain null bytes */
 749         ret = send_bin_buffer(fd,(char *) crypt_buf, numbytes);
 750         if (ret < 0)
 751                 goto net_err;
 752         /* recv decrypted number */
 753         ret = recv_buffer(fd, buf, sizeof(buf));
 754         if (ret < 0)
 755                 goto net_err;
 756         numbytes = ret;
 757         ret = -E_AUTH;
 758         if (!numbytes)
 759                 goto net_err;
 760         if (sscanf(buf, CHALLENGE_RESPONSE_MSG "%lu", &chall_response) < 1
 761                         || chall_response != challenge_nr)
 762                 goto err_out;
 763         /* auth successful, send 'Proceed' message */
 764         PARA_INFO_LOG("good auth for %s (%lu)\n", u->name, challenge_nr);
 765         sprintf(buf, "%s", PROCEED_MSG);
 766         if (use_rc4) {
 767                 init_rc4_keys();
 768                 ret = para_encrypt_buffer(u->rsa, rc4_buf, 2 * RC4_KEY_LEN,
 769                         (unsigned char *)buf + PROCEED_MSG_LEN + 1);
 770                 if (ret <= 0)
 771                         goto err_out;
 772                 numbytes = ret + strlen(PROCEED_MSG) + 1;
 773         } else
 774                 numbytes = strlen(buf);
 775         ret = send_bin_buffer(fd, buf, numbytes);
 776         if (ret < 0)
 777                 goto net_err;
 778         if (use_rc4)
 779                 enable_crypt(fd, rc4_recv, rc4_send, NULL);
 780         ret = read_command(fd, &command);
 781         if (ret == -E_COMMAND_SYNTAX)
 782                 goto err_out;
 783         if (ret < 0)
 784                 goto net_err;
 785         ret = -E_BAD_CMD;
 786         cmd = parse_cmd(command);
 787         if (!cmd)
 788                 goto err_out;
 789         /* valid command, check permissions */
 790         ret = check_perms(u->perms, cmd);
 791         if (ret < 0)
 792                 goto err_out;
 793         /* valid command and sufficient perms */
 794         alarm(0);
 795         argc = split_args(command, &argv, "\n");
 796         mmd_lock();
 797         mmd->num_commands++;
 798         mmd_unlock();
 799         PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", cmd->name, u->name,
 800                         peername);
 801         ret = cmd->handler(fd, argc, argv);
 802         if (ret >= 0) {
 803                 ret = EXIT_SUCCESS;
 804                 goto out;
 805         }
 806 err_out:
 807         send_va_buffer(fd, "%s\n", para_strerror(-ret));
 808 net_err:
 809         PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 810         ret = EXIT_FAILURE;
 811 out:
 812         free(command);
 813         free(argv);
 814         mmd_lock();
 815         if (cmd && (cmd->perms & AFS_WRITE) && ret >= 0)
 816                 mmd->events++;
 817         mmd->active_connections--;
 818         mmd_unlock();
 819         return ret;
 820 }