2 * Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file command.c Client authentication and server commands. */
9 #include <netinet/in.h>
10 #include <sys/socket.h>
13 #include <sys/types.h>
15 #include <arpa/inet.h>
25 #include "server.cmdline.h"
38 #include "server_cmd.lsg.h"
39 #include "user_list.h"
40 #include "afs.command_list.h"
44 #define SERVER_CMD_AUX_INFO(_arg) _arg,
45 static const unsigned server_command_perms[] = {LSG_SERVER_CMD_AUX_INFOS};
46 #undef SERVER_CMD_AUX_INFO
47 #define SERVER_CMD_AUX_INFO(_arg) #_arg,
48 static const char * const server_command_perms_txt[] = {LSG_SERVER_CMD_AUX_INFOS};
49 #undef SERVER_CMD_AUX_INFO
51 typedef int server_command_handler_t(struct command_context *);
52 server_command_handler_t AFS_COMMAND_HANDLERS;
54 /* Defines one command of para_server. */
55 struct server_command {
56 /* The name of the command. */
58 /* Pointer to the function that handles the command. */
59 server_command_handler_t *handler;
60 /* The privileges a user must have to execute this command. */
62 /* One-line description of the command. */
63 const char *description;
64 /* Summary of the command line options. */
66 /* The long help text. */
70 static struct server_command afs_cmds[] = {DEFINE_AFS_CMD_ARRAY};
72 /** Commands including options must be shorter than this. */
73 #define MAX_COMMAND_LEN 32768
76 extern struct misc_meta_data *mmd;
77 extern struct sender senders[];
78 int send_afs_status(struct command_context *cc, int parser_friendly);
80 static void dummy(__a_unused int s)
85 * Compute human readable vss status text.
87 * We can't call vss_playing() and friends here because those functions read
88 * the flags from the primary mmd structure, so calling them from command
89 * handler context would require to take the mmd lock. At the time the function
90 * is called we already took a copy of the mmd structure and want to use the
91 * flags value of the copy for computing the vss status text.
93 static char *vss_status_tohuman(unsigned int flags)
95 if (flags & VSS_PLAYING)
96 return para_strdup("playing");
98 return para_strdup("stopped");
99 return para_strdup("paused");
103 * Never returns NULL.
105 static char *vss_get_status_flags(unsigned int flags)
107 char *msg = para_malloc(5 * sizeof(char));
109 msg[0] = (flags & VSS_PLAYING)? 'P' : '_';
110 msg[1] = (flags & VSS_NOMORE)? 'O' : '_';
111 msg[2] = (flags & VSS_NEXT)? 'N' : '_';
112 msg[3] = (flags & VSS_REPOS)? 'R' : '_';
117 static unsigned get_status(struct misc_meta_data *nmmd, bool parser_friendly,
120 char *status, *flags; /* vss status info */
121 /* nobody updates our version of "now" */
122 long offset = (nmmd->offset + 500) / 1000;
123 struct timeval current_time;
124 struct para_buffer b = {.flags = parser_friendly? PBF_SIZE_PREFIX : 0};
126 /* report real status */
127 status = vss_status_tohuman(nmmd->vss_status_flags);
128 flags = vss_get_status_flags(nmmd->vss_status_flags);
129 clock_get_realtime(¤t_time);
131 * The calls to WRITE_STATUS_ITEM() below never fail because
132 * b->max_size is zero (unlimited), see para_printf(). However, clang
133 * is not smart enough to prove this and complains nevertheless.
134 * Casting the return value to void silences clang.
136 (void)WRITE_STATUS_ITEM(&b, SI_STATUS, "%s\n", status);
137 (void)WRITE_STATUS_ITEM(&b, SI_STATUS_FLAGS, "%s\n", flags);
138 (void)WRITE_STATUS_ITEM(&b, SI_OFFSET, "%li\n", offset);
139 (void)WRITE_STATUS_ITEM(&b, SI_AFS_MODE, "%s\n", mmd->afs_mode_string);
140 (void)WRITE_STATUS_ITEM(&b, SI_STREAM_START, "%lu.%lu\n",
141 (long unsigned)nmmd->stream_start.tv_sec,
142 (long unsigned)nmmd->stream_start.tv_usec);
143 (void)WRITE_STATUS_ITEM(&b, SI_CURRENT_TIME, "%lu.%lu\n",
144 (long unsigned)current_time.tv_sec,
145 (long unsigned)current_time.tv_usec);
153 * Send a sideband packet through a blocking file descriptor.
155 * \param scc fd and crypto keys.
156 * \param buf The buffer to send.
157 * \param numbytes The size of \a buf.
158 * \param band The sideband designator of this packet.
159 * \param dont_free If true, never deallocate \a buf.
161 * The nonblock flag must be disabled for the file descriptor given by \a scc.
163 * Stream cipher encryption is automatically activated if necessary via the
164 * sideband transformation, depending on the value of \a band.
168 * \sa \ref send_sb_va().
170 int send_sb(struct stream_cipher_context *scc, void *buf, size_t numbytes,
171 int band, bool dont_free)
174 struct sb_context *sbc;
176 sb_transformation trafo = band < SBD_PROCEED? NULL : sc_trafo;
177 struct sb_buffer sbb = SBB_INIT(band, buf, numbytes);
179 sbc = sb_new_send(&sbb, dont_free, trafo, scc->send);
181 ret = sb_get_send_buffers(sbc, iov);
182 ret = xwritev(scc->fd, iov, ret);
185 } while (sb_sent(sbc, ret) == false);
193 * Create a variable sized buffer and send it as a sideband packet.
195 * \param scc Passed to \ref send_sb.
196 * \param band See \ref send_sb.
197 * \param fmt The format string.
199 * \return The return value of the underlying call to \ref send_sb.
201 __printf_3_4 int send_sb_va(struct stream_cipher_context *scc, int band,
202 const char *fmt, ...)
209 ret = xvasprintf(&msg, fmt, ap);
211 return send_sb(scc, msg, ret, band, false);
215 * Send an error message to a client.
217 * \param cc Client info.
218 * \param err The (positive) error code.
220 * \return The return value of the underlying call to send_sb_va().
222 int send_strerror(struct command_context *cc, int err)
224 return send_sb_va(&cc->scc, SBD_ERROR_LOG, "%s\n", para_strerror(err));
228 * Send an error context to a client,
230 * \param cc Client info.
231 * \param errctx The error context string.
233 * \return The return value of the underlying call to send_sb_va().
235 * This function frees the error context string after it was sent.
237 int send_errctx(struct command_context *cc, char *errctx)
243 ret = send_sb_va(&cc->scc, SBD_ERROR_LOG, "%s\n", errctx);
248 static int check_sender_args(struct command_context *cc,
249 struct lls_parse_result *lpr, struct sender_command_data *scd)
252 const char *subcmds[] = {SENDER_SUBCOMMANDS};
255 unsigned num_inputs = lls_num_inputs(lpr);
257 scd->sender_num = -1;
258 ret = lls(lls_check_arg_count(lpr, 2, INT_MAX, &errctx));
260 send_errctx(cc, errctx);
263 arg = lls_input(0, lpr);
264 for (i = 0; senders[i].name; i++)
265 if (!strcmp(senders[i].name, arg))
267 if (!senders[i].name)
268 return -E_COMMAND_SYNTAX;
270 arg = lls_input(1, lpr);
271 for (i = 0; subcmds[i]; i++)
272 if (!strcmp(subcmds[i], arg))
275 return -E_COMMAND_SYNTAX;
277 if (!senders[scd->sender_num].client_cmds[scd->cmd_num])
278 return -E_SENDER_CMD;
279 switch (scd->cmd_num) {
283 return -E_COMMAND_SYNTAX;
287 if (num_inputs != 3 || parse_cidr(lls_input(2, lpr), scd->host,
288 sizeof(scd->host), &scd->netmask) == NULL)
289 return -E_COMMAND_SYNTAX;
294 return -E_COMMAND_SYNTAX;
295 return parse_fec_url(lls_input(2, lpr), scd);
297 return -E_COMMAND_SYNTAX;
303 * Send a sideband packet through a blocking file descriptor.
305 * \param scc fd and crypto keys.
306 * \param expected_band The expected band designator.
307 * \param max_size Passed to \ref sb_new_recv().
308 * \param result Body of the sideband packet is returned here.
310 * If \a expected_band is not \p SBD_ANY, the band designator of the received
311 * sideband packet is compared to \a expected_band and a mismatch is considered
316 int recv_sb(struct stream_cipher_context *scc,
317 enum sb_designator expected_band,
318 size_t max_size, struct iovec *result)
321 struct sb_context *sbc;
323 struct sb_buffer sbb;
324 sb_transformation trafo;
326 trafo = expected_band != SBD_ANY && expected_band < SBD_PROCEED?
328 sbc = sb_new_recv(max_size, trafo, scc->recv);
330 sb_get_recv_buffer(sbc, &iov);
331 ret = recv_bin_buffer(scc->fd, iov.iov_base, iov.iov_len);
336 ret = sb_received(sbc, ret, &sbb);
343 if (expected_band != SBD_ANY && sbb.band != expected_band)
352 static int com_sender(struct command_context *cc, struct lls_parse_result *lpr)
356 struct sender_command_data scd;
358 if (lls_num_inputs(lpr) == 0) {
359 for (i = 0; senders[i].name; i++) {
361 ret = xasprintf(&tmp, "%s%s\n", msg? msg : "",
366 return send_sb(&cc->scc, msg, ret, SBD_OUTPUT, false);
368 ret = check_sender_args(cc, lpr, &scd);
370 if (scd.sender_num < 0)
372 if (strcmp(lls_input(1, lpr), "status") == 0)
373 msg = senders[scd.sender_num].status();
375 msg = senders[scd.sender_num].help();
376 return send_sb(&cc->scc, msg, strlen(msg), SBD_OUTPUT, false);
379 switch (scd.cmd_num) {
382 assert(senders[scd.sender_num].resolve_target);
383 ret = senders[scd.sender_num].resolve_target(lls_input(2, lpr),
389 for (i = 0; i < 10; i++) {
390 mutex_lock(mmd_mutex);
391 if (mmd->sender_cmd_data.cmd_num >= 0) {
392 /* another sender command is active, retry in 100ms */
393 struct timespec ts = {.tv_nsec = 100 * 1000 * 1000};
394 mutex_unlock(mmd_mutex);
395 nanosleep(&ts, NULL);
398 mmd->sender_cmd_data = scd;
399 mutex_unlock(mmd_mutex);
402 return (i < 10)? 1 : -E_LOCK;
404 EXPORT_SERVER_CMD_HANDLER(sender);
406 static int com_si(struct command_context *cc,
407 __a_unused struct lls_parse_result *lpr)
412 ut = daemon_get_uptime_str(now);
413 mutex_lock(mmd_mutex);
414 ret = xasprintf(&msg,
415 "up: %s\nplayed: %u\n"
418 "connections (active/accepted/total): %u/%u/%u\n"
419 "current loglevel: %s\n"
420 "supported audio formats: %s\n",
424 mmd->active_connections,
428 AUDIO_FORMAT_HANDLERS
430 mutex_unlock(mmd_mutex);
432 return send_sb(&cc->scc, msg, ret, SBD_OUTPUT, false);
434 EXPORT_SERVER_CMD_HANDLER(si);
436 static int com_version(struct command_context *cc, struct lls_parse_result *lpr)
441 if (SERVER_CMD_OPT_GIVEN(VERSION, VERBOSE, lpr))
442 len = xasprintf(&msg, "%s", version_text("server"));
444 len = xasprintf(&msg, "%s\n", version_single_line("server"));
445 return send_sb(&cc->scc, msg, len, SBD_OUTPUT, false);
447 EXPORT_SERVER_CMD_HANDLER(version);
449 /** These status items are cleared if no audio file is currently open. */
450 #define EMPTY_STATUS_ITEMS \
455 ITEM(ATTRIBUTES_BITMAP) \
456 ITEM(ATTRIBUTES_TXT) \
467 ITEM(SECONDS_TOTAL) \
480 ITEM(AMPLIFICATION) \
483 * Write a list of audio-file related status items with empty values.
485 * This is used by vss when currently no audio file is open.
487 static unsigned empty_status_items(bool parser_friendly, char **result)
493 len = xasprintf(&esi,
494 #define ITEM(x) "0004 %02x:\n"
497 #define ITEM(x) , (unsigned) SI_ ## x
502 len = xasprintf(&esi,
503 #define ITEM(x) "%s:\n"
506 #define ITEM(x) ,status_item_list[SI_ ## x]
513 #undef EMPTY_STATUS_ITEMS
515 static int com_stat(struct command_context *cc, struct lls_parse_result *lpr)
518 struct misc_meta_data tmp, *nmmd = &tmp;
520 bool parser_friendly = SERVER_CMD_OPT_GIVEN(STAT, PARSER_FRIENDLY,
522 uint32_t num = SERVER_CMD_UINT32_VAL(STAT, NUM, lpr);
524 para_sigaction(SIGUSR1, dummy);
527 * Copy the mmd structure to minimize the time we hold the mmd
530 mutex_lock(mmd_mutex);
532 mutex_unlock(mmd_mutex);
533 ret = get_status(nmmd, parser_friendly, &s);
534 ret = send_sb(&cc->scc, s, ret, SBD_OUTPUT, false);
537 if (nmmd->vss_status_flags & VSS_NEXT) {
539 ret = empty_status_items(parser_friendly, &esi);
540 ret = send_sb(&cc->scc, esi, ret, SBD_OUTPUT, false);
544 send_afs_status(cc, parser_friendly);
546 if (num > 0 && !--num)
549 ret = -E_SERVER_CRASH;
556 EXPORT_SERVER_CMD_HANDLER(stat);
558 /* fixed-length, human readable permission string */
559 const char *server_cmd_perms_str(unsigned int perms)
561 static char result[5];
563 result[0] = perms & AFS_READ? 'a' : '-';
564 result[1] = perms & AFS_WRITE? 'A' : '-';
565 result[2] = perms & VSS_READ? 'v' : '-';
566 result[3] = perms & VSS_WRITE? 'V' : '-';
571 static int send_list_of_commands(struct command_context *cc)
574 const struct lls_command *cmd;
575 char *msg = para_strdup("");
577 for (i = 1; (cmd = lls_cmd(i, server_cmd_suite)); i++) {
578 const char *perms = server_cmd_perms_str(server_command_perms[i]);
579 char *tmp = make_message("%s%s\t%s\t%s\n", msg,
580 lls_command_name(cmd), perms, lls_purpose(cmd));
584 return send_sb(&cc->scc, msg, strlen(msg), SBD_OUTPUT, false);
587 /* returns string that must be freed by the caller */
588 static struct server_command *get_cmd_ptr(const char *name, char **handler)
590 struct server_command *cmd;
592 /* not found, look for commands supported by afs */
593 for (cmd = afs_cmds; cmd->name; cmd++)
594 if (!strcmp(cmd->name, name)) {
596 *handler = para_strdup("afs");
602 static int com_help(struct command_context *cc, struct lls_parse_result *lpr)
605 char *long_help, *buf, *errctx;
607 const struct lls_command *cmd;
609 ret = lls(lls_check_arg_count(lpr, 0, 1, &errctx));
611 send_errctx(cc, errctx);
614 if (lls_num_inputs(lpr) == 0)
615 return send_list_of_commands(cc);
616 /* argument given for help */
617 ret = lls(lls_lookup_subcmd(lls_input(0, lpr), server_cmd_suite,
620 send_errctx(cc, errctx);
623 cmd = lls_cmd(ret, server_cmd_suite);
624 perms = server_command_perms_txt[ret];
625 long_help = lls_long_help(cmd);
627 ret = xasprintf(&buf, "%spermissions: %s\n", long_help, perms);
629 return send_sb(&cc->scc, buf, ret, SBD_OUTPUT, false);
631 EXPORT_SERVER_CMD_HANDLER(help);
633 static int com_hup(__a_unused struct command_context *cc,
634 __a_unused struct lls_parse_result *lpr)
636 kill(getppid(), SIGHUP);
639 EXPORT_SERVER_CMD_HANDLER(hup);
641 static int com_term(__a_unused struct command_context *cc,
642 __a_unused struct lls_parse_result *lpr)
644 kill(getppid(), SIGTERM);
647 EXPORT_SERVER_CMD_HANDLER(term);
649 static int com_play(__a_unused struct command_context *cc,
650 __a_unused struct lls_parse_result *lpr)
652 mutex_lock(mmd_mutex);
653 mmd->new_vss_status_flags |= VSS_PLAYING;
654 mmd->new_vss_status_flags &= ~VSS_NOMORE;
655 mutex_unlock(mmd_mutex);
658 EXPORT_SERVER_CMD_HANDLER(play);
660 static int com_stop(__a_unused struct command_context *cc,
661 __a_unused struct lls_parse_result *lpr)
663 mutex_lock(mmd_mutex);
664 mmd->new_vss_status_flags &= ~VSS_PLAYING;
665 mmd->new_vss_status_flags &= ~VSS_REPOS;
666 mmd->new_vss_status_flags |= VSS_NEXT;
667 mutex_unlock(mmd_mutex);
670 EXPORT_SERVER_CMD_HANDLER(stop);
672 static int com_pause(__a_unused struct command_context *cc,
673 __a_unused struct lls_parse_result *lpr)
675 mutex_lock(mmd_mutex);
676 if (!vss_paused() && !vss_stopped()) {
678 mmd->new_vss_status_flags &= ~VSS_PLAYING;
679 mmd->new_vss_status_flags &= ~VSS_NEXT;
681 mutex_unlock(mmd_mutex);
684 EXPORT_SERVER_CMD_HANDLER(pause);
686 static int com_next(__a_unused struct command_context *cc,
687 __a_unused struct lls_parse_result *lpr)
689 mutex_lock(mmd_mutex);
691 mmd->new_vss_status_flags |= VSS_NEXT;
692 mutex_unlock(mmd_mutex);
695 EXPORT_SERVER_CMD_HANDLER(next);
697 static int com_nomore(__a_unused struct command_context *cc,
698 __a_unused struct lls_parse_result *lpr)
700 mutex_lock(mmd_mutex);
701 if (vss_playing() || vss_paused())
702 mmd->new_vss_status_flags |= VSS_NOMORE;
703 mutex_unlock(mmd_mutex);
706 EXPORT_SERVER_CMD_HANDLER(nomore);
708 static int com_ff(__a_unused struct command_context *cc,
709 struct lls_parse_result *lpr)
712 int ret, backwards = 0;
716 ret = lls(lls_check_arg_count(lpr, 1, 1, &errctx));
718 send_errctx(cc, errctx);
721 if (!(ret = sscanf(lls_input(0, lpr), "%u%c", &i, &c)))
722 return -E_COMMAND_SYNTAX;
723 if (ret > 1 && c == '-')
724 backwards = 1; /* jmp backwards */
725 mutex_lock(mmd_mutex);
726 ret = -E_NO_AUDIO_FILE;
727 if (!mmd->afd.afhi.chunks_total || !mmd->afd.afhi.seconds_total)
729 promille = (1000 * mmd->current_chunk) / mmd->afd.afhi.chunks_total;
731 promille -= 1000 * i / mmd->afd.afhi.seconds_total;
733 promille += 1000 * i / mmd->afd.afhi.seconds_total;
736 if (promille > 1000) {
737 mmd->new_vss_status_flags |= VSS_NEXT;
740 mmd->repos_request = (mmd->afd.afhi.chunks_total * promille) / 1000;
741 mmd->new_vss_status_flags |= VSS_REPOS;
742 mmd->new_vss_status_flags &= ~VSS_NEXT;
746 mutex_unlock(mmd_mutex);
749 EXPORT_SERVER_CMD_HANDLER(ff);
751 static int com_jmp(__a_unused struct command_context *cc,
752 struct lls_parse_result *lpr)
758 ret = lls(lls_check_arg_count(lpr, 1, 1, &errctx));
760 send_errctx(cc, errctx);
763 if (sscanf(lls_input(0, lpr), "%lu", &i) <= 0)
764 return -ERRNO_TO_PARA_ERROR(EINVAL);
765 mutex_lock(mmd_mutex);
766 ret = -E_NO_AUDIO_FILE;
767 if (!mmd->afd.afhi.chunks_total)
771 PARA_INFO_LOG("jumping to %lu%%\n", i);
772 mmd->repos_request = (mmd->afd.afhi.chunks_total * i + 50) / 100;
773 PARA_INFO_LOG("sent: %lu, offset before jmp: %li\n",
774 mmd->chunks_sent, mmd->offset);
775 mmd->new_vss_status_flags |= VSS_REPOS;
776 mmd->new_vss_status_flags &= ~VSS_NEXT;
780 mutex_unlock(mmd_mutex);
783 EXPORT_SERVER_CMD_HANDLER(jmp);
785 static int com_tasks(struct command_context *cc,
786 __a_unused struct lls_parse_result *lpr)
788 char *tl = server_get_tasks();
790 return send_sb(&cc->scc, tl, strlen(tl), SBD_OUTPUT, false);
792 EXPORT_SERVER_CMD_HANDLER(tasks);
795 * check if perms are sufficient to exec a command having perms cmd_perms.
796 * Returns 0 if perms are sufficient, -E_PERM otherwise.
798 static int check_perms(unsigned int perms, const struct server_command *cmd_ptr)
800 PARA_DEBUG_LOG("checking permissions\n");
801 return (cmd_ptr->perms & perms) < cmd_ptr->perms ? -E_PERM : 0;
804 static void reset_signals(void)
806 para_sigaction(SIGCHLD, SIG_IGN);
807 para_sigaction(SIGINT, SIG_DFL);
808 para_sigaction(SIGTERM, SIG_DFL);
809 para_sigaction(SIGHUP, SIG_DFL);
812 struct connection_features {
813 bool aes_ctr128_requested;
816 static int parse_auth_request(char *buf, int len, struct user **u,
817 struct connection_features *cf)
820 char *p, *username, **features = NULL;
821 size_t auth_rq_len = strlen(AUTH_REQUEST_MSG);
824 memset(cf, 0, sizeof(*cf));
825 if (len < auth_rq_len + 2)
826 return -E_AUTH_REQUEST;
827 if (strncmp(buf, AUTH_REQUEST_MSG, auth_rq_len) != 0)
828 return -E_AUTH_REQUEST;
829 username = buf + auth_rq_len;
830 p = strchr(username, ' ');
834 return -E_AUTH_REQUEST;
837 create_argv(p, ",", &features);
838 for (i = 0; features[i]; i++) {
839 if (strcmp(features[i], "sideband") == 0)
841 if (strcmp(features[i], "aes_ctr128") == 0)
842 cf->aes_ctr128_requested = true;
844 ret = -E_BAD_FEATURE;
849 PARA_DEBUG_LOG("received auth request for user %s\n", username);
850 *u = lookup_user(username);
857 #define HANDSHAKE_BUFSIZE 4096
859 static int run_command(struct command_context *cc, struct iovec *iov,
860 const char *peername)
864 struct server_command *cmd = NULL;
865 const struct lls_command *lcmd = NULL;
867 struct lls_parse_result *lpr;
870 if (iov->iov_base == NULL || iov->iov_len == 0)
871 return -ERRNO_TO_PARA_ERROR(EINVAL);
873 p[iov->iov_len - 1] = '\0'; /* just to be sure */
875 ret = lls(lls_lookup_subcmd(p, server_cmd_suite, &errctx));
876 if (ret >= 0 && !strcmp(p, lls_command_name(lls_cmd(ret,
877 server_cmd_suite)))) {
878 perms = server_command_perms[ret];
879 if ((perms & cc->u->perms) != perms)
881 lcmd = lls_cmd(ret, server_cmd_suite);
883 cmd = get_cmd_ptr(p, NULL);
885 send_errctx(cc, errctx);
889 ret = check_perms(cc->u->perms, cmd);
893 end = iov->iov_base + iov->iov_len;
894 for (i = 0; p < end; i++)
897 cc->argv = para_malloc((cc->argc + 1) * sizeof(char *));
898 for (i = 0, p = iov->iov_base; p < end; i++) {
899 cc->argv[i] = para_strdup(p);
902 cc->argv[cc->argc] = NULL;
903 PARA_NOTICE_LOG("calling com_%s() for %s@%s\n", lcmd?
904 lls_command_name(lcmd) : cmd->name, cc->u->name, peername);
906 ret = lls(lls_parse(cc->argc, cc->argv, lcmd, &lpr, &errctx));
908 const struct server_cmd_user_data *ud = lls_user_data(lcmd);
909 ret = ud->handler(cc, lpr);
910 lls_free_parse_result(lpr, lcmd);
912 send_errctx(cc, errctx);
914 ret = cmd->handler(cc);
917 mutex_lock(mmd_mutex);
919 if (ret >= 0 && (perms & AFS_WRITE))
921 mutex_unlock(mmd_mutex);
926 * Perform user authentication and execute a command.
928 * \param fd The file descriptor to send output to.
929 * \param peername Identifies the connecting peer.
931 * Whenever para_server accepts an incoming tcp connection on the port it
932 * listens on, it forks and the resulting child calls this function.
934 * An RSA-based challenge/response is used to authenticate the peer. It that
935 * authentication succeeds, a random session key is generated and sent back to
936 * the peer, encrypted with its RSA public key. From this point on, all
937 * transfers are crypted with this session key.
939 * Next it is checked if the peer supplied a valid server command or a command
940 * for the audio file selector. If yes, and if the user has sufficient
941 * permissions to execute that command, the function calls the corresponding
942 * command handler which does argument checking and further processing.
944 * In order to cope with a DOS attacks, a timeout is set up which terminates
945 * the function if the connection was not authenticated when the timeout
948 * \sa alarm(2), crypt.c, crypt.h
950 __noreturn void handle_connect(int fd, const char *peername)
953 unsigned char rand_buf[CHALLENGE_SIZE + 2 * SESSION_KEY_LEN];
954 unsigned char challenge_hash[HASH_SIZE];
955 char *command = NULL, *buf = para_malloc(HANDSHAKE_BUFSIZE) /* must be on the heap */;
957 struct command_context cc_struct = {.peer = peername}, *cc = &cc_struct;
959 struct connection_features cf;
963 /* we need a blocking fd here as recv() might return EAGAIN otherwise. */
964 ret = mark_fd_blocking(fd);
967 /* send Welcome message */
968 ret = write_va_buffer(fd, "This is para_server, version "
969 PACKAGE_VERSION ".\n"
970 "Features: sideband,aes_ctr128\n"
974 /* recv auth request line */
975 ret = recv_buffer(fd, buf, HANDSHAKE_BUFSIZE);
978 ret = parse_auth_request(buf, ret, &cc->u, &cf);
982 get_random_bytes_or_die(rand_buf, sizeof(rand_buf));
983 ret = pub_encrypt(cc->u->pubkey, rand_buf, sizeof(rand_buf),
984 (unsigned char *)buf);
990 * We don't want to reveal our user names, so we send a
991 * challenge to the client even if the user does not exist, and
992 * fail the authentication later.
995 get_random_bytes_or_die((unsigned char *)buf, numbytes);
997 PARA_DEBUG_LOG("sending %d byte challenge + session key (%zu bytes)\n",
998 CHALLENGE_SIZE, numbytes);
999 ret = send_sb(&cc->scc, buf, numbytes, SBD_CHALLENGE, false);
1003 ret = recv_sb(&cc->scc, SBD_CHALLENGE_RESPONSE,
1004 HANDSHAKE_BUFSIZE, &iov);
1008 numbytes = iov.iov_len;
1009 PARA_DEBUG_LOG("received %zu bytes challenge response\n", numbytes);
1014 * The correct response is the hash of the first CHALLENGE_SIZE bytes
1015 * of the random data.
1018 if (numbytes != HASH_SIZE)
1020 hash_function((char *)rand_buf, CHALLENGE_SIZE, challenge_hash);
1021 if (memcmp(challenge_hash, buf, HASH_SIZE))
1023 /* auth successful */
1025 PARA_INFO_LOG("good auth for %s\n", cc->u->name);
1026 /* init stream cipher keys with the second part of the random buffer */
1027 cc->scc.recv = sc_new(rand_buf + CHALLENGE_SIZE, SESSION_KEY_LEN,
1028 cf.aes_ctr128_requested);
1029 cc->scc.send = sc_new(rand_buf + CHALLENGE_SIZE + SESSION_KEY_LEN,
1030 SESSION_KEY_LEN, cf.aes_ctr128_requested);
1031 ret = send_sb(&cc->scc, NULL, 0, SBD_PROCEED, false);
1034 ret = recv_sb(&cc->scc, SBD_COMMAND, MAX_COMMAND_LEN, &iov);
1037 ret = run_command(cc, &iov, peername);
1044 if (send_strerror(cc, -ret) >= 0)
1045 send_sb(&cc->scc, NULL, 0, SBD_EXIT__FAILURE, true);
1047 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
1051 mutex_lock(mmd_mutex);
1052 mmd->active_connections--;
1053 mutex_unlock(mmd_mutex);
1055 ret = send_sb(&cc->scc, NULL, 0, SBD_EXIT__SUCCESS, true);
1057 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
1059 sc_free(cc->scc.recv);
1060 sc_free(cc->scc.send);
1061 exit(ret < 0? EXIT_FAILURE : EXIT_SUCCESS);