source: branches/3.2/mindi-busybox/networking/tcpudp.c @ 3186

Last change on this file since 3186 was 2725, checked in by bruno, 8 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
  • Property svn:eol-style set to native
File size: 18.2 KB
Line 
1/* Based on ipsvd utilities written by Gerrit Pape <pape@smarden.org>
2 * which are released into public domain by the author.
3 * Homepage: http://smarden.sunsite.dk/ipsvd/
4 *
5 * Copyright (C) 2007 Denys Vlasenko.
6 *
7 * Licensed under GPLv2, see file LICENSE in this source tree.
8 */
9
10/* Based on ipsvd-0.12.1. This tcpsvd accepts all options
11 * which are supported by one from ipsvd-0.12.1, but not all are
12 * functional. See help text at the end of this file for details.
13 *
14 * Code inside "#ifdef SSLSVD" is for sslsvd and is currently unused.
15 *
16 * Busybox version exports TCPLOCALADDR instead of
17 * TCPLOCALIP + TCPLOCALPORT pair. ADDR more closely matches reality
18 * (which is "struct sockaddr_XXX". Port is not a separate entity,
19 * it's just a part of (AF_INET[6]) sockaddr!).
20 *
21 * TCPORIGDSTADDR is Busybox-specific addition.
22 *
23 * udp server is hacked up by reusing TCP code. It has the following
24 * limitation inherent in Unix DGRAM sockets implementation:
25 * - local IP address is retrieved (using recvmsg voodoo) but
26 *   child's socket is not bound to it (bind cannot be called on
27 *   already bound socket). Thus it still can emit outgoing packets
28 *   with wrong source IP...
29 * - don't know how to retrieve ORIGDST for udp.
30 */
31
32#include "libbb.h"
33
34/* Wants <limits.h> etc, thus included after libbb.h: */
35#ifdef __linux__
36#include <linux/types.h> /* for __be32 etc */
37#include <linux/netfilter_ipv4.h>
38#endif
39
40// TODO: move into this file:
41#include "tcpudp_perhost.h"
42
43#ifdef SSLSVD
44#include "matrixSsl.h"
45#include "ssl_io.h"
46#endif
47
48struct globals {
49    unsigned verbose;
50    unsigned max_per_host;
51    unsigned cur_per_host;
52    unsigned cnum;
53    unsigned cmax;
54    char **env_cur;
55    char *env_var[1]; /* actually bigger */
56} FIX_ALIASING;
57#define G (*(struct globals*)&bb_common_bufsiz1)
58#define verbose      (G.verbose     )
59#define max_per_host (G.max_per_host)
60#define cur_per_host (G.cur_per_host)
61#define cnum         (G.cnum        )
62#define cmax         (G.cmax        )
63#define env_cur      (G.env_cur     )
64#define env_var      (G.env_var     )
65#define INIT_G() do { \
66    cmax = 30; \
67    env_cur = &env_var[0]; \
68} while (0)
69
70
71/* We have to be careful about leaking memory in repeated setenv's */
72static void xsetenv_plain(const char *n, const char *v)
73{
74    char *var = xasprintf("%s=%s", n, v);
75    *env_cur++ = var;
76    putenv(var);
77}
78
79static void xsetenv_proto(const char *proto, const char *n, const char *v)
80{
81    char *var = xasprintf("%s%s=%s", proto, n, v);
82    *env_cur++ = var;
83    putenv(var);
84}
85
86static void undo_xsetenv(void)
87{
88    char **pp = env_cur = &env_var[0];
89    while (*pp) {
90        char *var = *pp;
91        bb_unsetenv_and_free(var);
92        *pp++ = NULL;
93    }
94}
95
96static void sig_term_handler(int sig)
97{
98    if (verbose)
99        bb_error_msg("got signal %u, exit", sig);
100    kill_myself_with_sig(sig);
101}
102
103/* Little bloated, but tries to give accurate info how child exited.
104 * Makes easier to spot segfaulting children etc... */
105static void print_waitstat(unsigned pid, int wstat)
106{
107    unsigned e = 0;
108    const char *cause = "?exit";
109
110    if (WIFEXITED(wstat)) {
111        cause++;
112        e = WEXITSTATUS(wstat);
113    } else if (WIFSIGNALED(wstat)) {
114        cause = "signal";
115        e = WTERMSIG(wstat);
116    }
117    bb_error_msg("end %d %s %d", pid, cause, e);
118}
119
120/* Must match getopt32 in main! */
121enum {
122    OPT_c = (1 << 0),
123    OPT_C = (1 << 1),
124    OPT_i = (1 << 2),
125    OPT_x = (1 << 3),
126    OPT_u = (1 << 4),
127    OPT_l = (1 << 5),
128    OPT_E = (1 << 6),
129    OPT_b = (1 << 7),
130    OPT_h = (1 << 8),
131    OPT_p = (1 << 9),
132    OPT_t = (1 << 10),
133    OPT_v = (1 << 11),
134    OPT_V = (1 << 12),
135    OPT_U = (1 << 13), /* from here: sslsvd only */
136    OPT_slash = (1 << 14),
137    OPT_Z = (1 << 15),
138    OPT_K = (1 << 16),
139};
140
141static void connection_status(void)
142{
143    /* "only 1 client max" desn't need this */
144    if (cmax > 1)
145        bb_error_msg("status %u/%u", cnum, cmax);
146}
147
148static void sig_child_handler(int sig UNUSED_PARAM)
149{
150    int wstat;
151    pid_t pid;
152
153    while ((pid = wait_any_nohang(&wstat)) > 0) {
154        if (max_per_host)
155            ipsvd_perhost_remove(pid);
156        if (cnum)
157            cnum--;
158        if (verbose)
159            print_waitstat(pid, wstat);
160    }
161    if (verbose)
162        connection_status();
163}
164
165int tcpudpsvd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
166int tcpudpsvd_main(int argc UNUSED_PARAM, char **argv)
167{
168    char *str_C, *str_t;
169    char *user;
170    struct hcc *hccp;
171    const char *instructs;
172    char *msg_per_host = NULL;
173    unsigned len_per_host = len_per_host; /* gcc */
174#ifndef SSLSVD
175    struct bb_uidgid_t ugid;
176#endif
177    bool tcp;
178    uint16_t local_port;
179    char *preset_local_hostname = NULL;
180    char *remote_hostname = remote_hostname; /* for compiler */
181    char *remote_addr = remote_addr; /* for compiler */
182    len_and_sockaddr *lsa;
183    len_and_sockaddr local, remote;
184    socklen_t sa_len;
185    int pid;
186    int sock;
187    int conn;
188    unsigned backlog = 20;
189    unsigned opts;
190
191    INIT_G();
192
193    tcp = (applet_name[0] == 't');
194
195    /* 3+ args, -i at most once, -p implies -h, -v is counter, -b N, -c N */
196    opt_complementary = "-3:i--i:ph:vv:b+:c+";
197#ifdef SSLSVD
198    opts = getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:vU:/:Z:K:",
199        &cmax, &str_C, &instructs, &instructs, &user, &preset_local_hostname,
200        &backlog, &str_t, &ssluser, &root, &cert, &key, &verbose
201    );
202#else
203    /* "+": stop on first non-option */
204    opts = getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:v",
205        &cmax, &str_C, &instructs, &instructs, &user, &preset_local_hostname,
206        &backlog, &str_t, &verbose
207    );
208#endif
209    if (opts & OPT_C) { /* -C n[:message] */
210        max_per_host = bb_strtou(str_C, &str_C, 10);
211        if (str_C[0]) {
212            if (str_C[0] != ':')
213                bb_show_usage();
214            msg_per_host = str_C + 1;
215            len_per_host = strlen(msg_per_host);
216        }
217    }
218    if (max_per_host > cmax)
219        max_per_host = cmax;
220    if (opts & OPT_u) {
221        xget_uidgid(&ugid, user);
222    }
223#ifdef SSLSVD
224    if (opts & OPT_U) ssluser = optarg;
225    if (opts & OPT_slash) root = optarg;
226    if (opts & OPT_Z) cert = optarg;
227    if (opts & OPT_K) key = optarg;
228#endif
229    argv += optind;
230    if (!argv[0][0] || LONE_CHAR(argv[0], '0'))
231        argv[0] = (char*)"0.0.0.0";
232
233    /* Per-IP flood protection is not thought-out for UDP */
234    if (!tcp)
235        max_per_host = 0;
236
237    bb_sanitize_stdio(); /* fd# 0,1,2 must be opened */
238
239#ifdef SSLSVD
240    sslser = user;
241    client = 0;
242    if ((getuid() == 0) && !(opts & OPT_u)) {
243        xfunc_exitcode = 100;
244        bb_error_msg_and_die(bb_msg_you_must_be_root);
245    }
246    if (opts & OPT_u)
247        if (!uidgid_get(&sslugid, ssluser, 1)) {
248            if (errno) {
249                bb_perror_msg_and_die("can't get user/group: %s", ssluser);
250            }
251            bb_error_msg_and_die("unknown user/group %s", ssluser);
252        }
253    if (!cert) cert = "./cert.pem";
254    if (!key) key = cert;
255    if (matrixSslOpen() < 0)
256        fatal("can't initialize ssl");
257    if (matrixSslReadKeys(&keys, cert, key, 0, ca) < 0) {
258        if (client)
259            fatal("can't read cert, key, or ca file");
260        fatal("can't read cert or key file");
261    }
262    if (matrixSslNewSession(&ssl, keys, 0, SSL_FLAGS_SERVER) < 0)
263        fatal("can't create ssl session");
264#endif
265
266    sig_block(SIGCHLD);
267    signal(SIGCHLD, sig_child_handler);
268    bb_signals(BB_FATAL_SIGS, sig_term_handler);
269    signal(SIGPIPE, SIG_IGN);
270
271    if (max_per_host)
272        ipsvd_perhost_init(cmax);
273
274    local_port = bb_lookup_port(argv[1], tcp ? "tcp" : "udp", 0);
275    lsa = xhost2sockaddr(argv[0], local_port);
276    argv += 2;
277
278    sock = xsocket(lsa->u.sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
279    setsockopt_reuseaddr(sock);
280    sa_len = lsa->len; /* I presume sockaddr len stays the same */
281    xbind(sock, &lsa->u.sa, sa_len);
282    if (tcp) {
283        xlisten(sock, backlog);
284        close_on_exec_on(sock);
285    } else { /* udp: needed for recv_from_to to work: */
286        socket_want_pktinfo(sock);
287    }
288    /* ndelay_off(sock); - it is the default I think? */
289
290#ifndef SSLSVD
291    if (opts & OPT_u) {
292        /* drop permissions */
293        xsetgid(ugid.gid);
294        xsetuid(ugid.uid);
295    }
296#endif
297
298    if (verbose) {
299        char *addr = xmalloc_sockaddr2dotted(&lsa->u.sa);
300        if (opts & OPT_u)
301            bb_error_msg("listening on %s, starting, uid %u, gid %u", addr,
302                (unsigned)ugid.uid, (unsigned)ugid.gid);
303        else
304            bb_error_msg("listening on %s, starting", addr);
305        free(addr);
306    }
307
308    /* Main accept() loop */
309
310 again:
311    hccp = NULL;
312
313    while (cnum >= cmax)
314        wait_for_any_sig(); /* expecting SIGCHLD */
315
316    /* Accept a connection to fd #0 */
317 again1:
318    close(0);
319 again2:
320    sig_unblock(SIGCHLD);
321    local.len = remote.len = sa_len;
322    if (tcp) {
323        conn = accept(sock, &remote.u.sa, &remote.len);
324    } else {
325        /* In case recv_from_to won't be able to recover local addr.
326         * Also sets port - recv_from_to is unable to do it. */
327        local = *lsa;
328        conn = recv_from_to(sock, NULL, 0, MSG_PEEK,
329                &remote.u.sa, &local.u.sa, sa_len);
330    }
331    sig_block(SIGCHLD);
332    if (conn < 0) {
333        if (errno != EINTR)
334            bb_perror_msg(tcp ? "accept" : "recv");
335        goto again2;
336    }
337    xmove_fd(tcp ? conn : sock, 0);
338
339    if (max_per_host) {
340        /* Drop connection immediately if cur_per_host > max_per_host
341         * (minimizing load under SYN flood) */
342        remote_addr = xmalloc_sockaddr2dotted_noport(&remote.u.sa);
343        cur_per_host = ipsvd_perhost_add(remote_addr, max_per_host, &hccp);
344        if (cur_per_host > max_per_host) {
345            /* ipsvd_perhost_add detected that max is exceeded
346             * (and did not store ip in connection table) */
347            free(remote_addr);
348            if (msg_per_host) {
349                /* don't block or test for errors */
350                send(0, msg_per_host, len_per_host, MSG_DONTWAIT);
351            }
352            goto again1;
353        }
354        /* NB: remote_addr is not leaked, it is stored in conn table */
355    }
356
357    if (!tcp) {
358        /* Voodoo magic: making udp sockets each receive its own
359         * packets is not trivial, and I still not sure
360         * I do it 100% right.
361         * 1) we have to do it before fork()
362         * 2) order is important - is it right now? */
363
364        /* Open new non-connected UDP socket for further clients... */
365        sock = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0);
366        setsockopt_reuseaddr(sock);
367        /* Make plain write/send work for old socket by supplying default
368         * destination address. This also restricts incoming packets
369         * to ones coming from this remote IP. */
370        xconnect(0, &remote.u.sa, sa_len);
371    /* hole? at this point we have no wildcard udp socket...
372     * can this cause clients to get "port unreachable" icmp?
373     * Yup, time window is very small, but it exists (is it?) */
374        /* ..."open new socket", continued */
375        xbind(sock, &lsa->u.sa, sa_len);
376        socket_want_pktinfo(sock);
377
378        /* Doesn't work:
379         * we cannot replace fd #0 - we will lose pending packet
380         * which is already buffered for us! And we cannot use fd #1
381         * instead - it will "intercept" all following packets, but child
382         * does not expect data coming *from fd #1*! */
383#if 0
384        /* Make it so that local addr is fixed to localp->u.sa
385         * and we don't accidentally accept packets to other local IPs. */
386        /* NB: we possibly bind to the _very_ same_ address & port as the one
387         * already bound in parent! This seems to work in Linux.
388         * (otherwise we can move socket to fd #0 only if bind succeeds) */
389        close(0);
390        set_nport(localp, htons(local_port));
391        xmove_fd(xsocket(localp->u.sa.sa_family, SOCK_DGRAM, 0), 0);
392        setsockopt_reuseaddr(0); /* crucial */
393        xbind(0, &localp->u.sa, localp->len);
394#endif
395    }
396
397    pid = vfork();
398    if (pid == -1) {
399        bb_perror_msg("vfork");
400        goto again;
401    }
402
403    if (pid != 0) {
404        /* Parent */
405        cnum++;
406        if (verbose)
407            connection_status();
408        if (hccp)
409            hccp->pid = pid;
410        /* clean up changes done by vforked child */
411        undo_xsetenv();
412        goto again;
413    }
414
415    /* Child: prepare env, log, and exec prog */
416
417    { /* vfork alert! every xmalloc in this block should be freed! */
418        char *local_hostname = local_hostname; /* for compiler */
419        char *local_addr = NULL;
420        char *free_me0 = NULL;
421        char *free_me1 = NULL;
422        char *free_me2 = NULL;
423
424        if (verbose || !(opts & OPT_E)) {
425            if (!max_per_host) /* remote_addr is not yet known */
426                free_me0 = remote_addr = xmalloc_sockaddr2dotted(&remote.u.sa);
427            if (opts & OPT_h) {
428                free_me1 = remote_hostname = xmalloc_sockaddr2host_noport(&remote.u.sa);
429                if (!remote_hostname) {
430                    bb_error_msg("can't look up hostname for %s", remote_addr);
431                    remote_hostname = remote_addr;
432                }
433            }
434            /* Find out local IP peer connected to.
435             * Errors ignored (I'm not paranoid enough to imagine kernel
436             * which doesn't know local IP). */
437            if (tcp)
438                getsockname(0, &local.u.sa, &local.len);
439            /* else: for UDP it is done earlier by parent */
440            local_addr = xmalloc_sockaddr2dotted(&local.u.sa);
441            if (opts & OPT_h) {
442                local_hostname = preset_local_hostname;
443                if (!local_hostname) {
444                    free_me2 = local_hostname = xmalloc_sockaddr2host_noport(&local.u.sa);
445                    if (!local_hostname)
446                        bb_error_msg_and_die("can't look up hostname for %s", local_addr);
447                }
448                /* else: local_hostname is not NULL, but is NOT malloced! */
449            }
450        }
451        if (verbose) {
452            pid = getpid();
453            if (max_per_host) {
454                bb_error_msg("concurrency %s %u/%u",
455                    remote_addr,
456                    cur_per_host, max_per_host);
457            }
458            bb_error_msg((opts & OPT_h)
459                ? "start %u %s-%s (%s-%s)"
460                : "start %u %s-%s",
461                pid,
462                local_addr, remote_addr,
463                local_hostname, remote_hostname);
464        }
465
466        if (!(opts & OPT_E)) {
467            /* setup ucspi env */
468            const char *proto = tcp ? "TCP" : "UDP";
469
470#ifdef SO_ORIGINAL_DST
471            /* Extract "original" destination addr:port
472             * from Linux firewall. Useful when you redirect
473             * an outbond connection to local handler, and it needs
474             * to know where it originally tried to connect */
475            if (tcp && getsockopt(0, SOL_IP, SO_ORIGINAL_DST, &local.u.sa, &local.len) == 0) {
476                char *addr = xmalloc_sockaddr2dotted(&local.u.sa);
477                xsetenv_plain("TCPORIGDSTADDR", addr);
478                free(addr);
479            }
480#endif
481            xsetenv_plain("PROTO", proto);
482            xsetenv_proto(proto, "LOCALADDR", local_addr);
483            xsetenv_proto(proto, "REMOTEADDR", remote_addr);
484            if (opts & OPT_h) {
485                xsetenv_proto(proto, "LOCALHOST", local_hostname);
486                xsetenv_proto(proto, "REMOTEHOST", remote_hostname);
487            }
488            //compat? xsetenv_proto(proto, "REMOTEINFO", "");
489            /* additional */
490            if (cur_per_host > 0) /* can not be true for udp */
491                xsetenv_plain("TCPCONCURRENCY", utoa(cur_per_host));
492        }
493        free(local_addr);
494        free(free_me0);
495        free(free_me1);
496        free(free_me2);
497    }
498
499    xdup2(0, 1);
500
501    signal(SIGPIPE, SIG_DFL); /* this one was SIG_IGNed */
502    /* Non-ignored signals revert to SIG_DFL on exec anyway */
503    /*signal(SIGCHLD, SIG_DFL);*/
504    sig_unblock(SIGCHLD);
505
506#ifdef SSLSVD
507    strcpy(id, utoa(pid));
508    ssl_io(0, argv);
509    bb_perror_msg_and_die("can't execute '%s'", argv[0]);
510#else
511    BB_EXECVP_or_die(argv);
512#endif
513}
514
515/*
516tcpsvd [-hpEvv] [-c n] [-C n:msg] [-b n] [-u user] [-l name]
517    [-i dir|-x cdb] [ -t sec] host port prog
518
519tcpsvd creates a TCP/IP socket, binds it to the address host:port,
520and listens on the socket for incoming connections.
521
522On each incoming connection, tcpsvd conditionally runs a program,
523with standard input reading from the socket, and standard output
524writing to the socket, to handle this connection. tcpsvd keeps
525listening on the socket for new connections, and can handle
526multiple connections simultaneously.
527
528tcpsvd optionally checks for special instructions depending
529on the IP address or hostname of the client that initiated
530the connection, see ipsvd-instruct(5).
531
532host
533    host either is a hostname, or a dotted-decimal IP address,
534    or 0. If host is 0, tcpsvd accepts connections to any local
535    IP address.
536    * busybox accepts IPv6 addresses and host:port pairs too
537      In this case second parameter is ignored
538port
539    tcpsvd accepts connections to host:port. port may be a name
540    from /etc/services or a number.
541prog
542    prog consists of one or more arguments. For each connection,
543    tcpsvd normally runs prog, with file descriptor 0 reading from
544    the network, and file descriptor 1 writing to the network.
545    By default it also sets up TCP-related environment variables,
546    see tcp-environ(5)
547-i dir
548    read instructions for handling new connections from the instructions
549    directory dir. See ipsvd-instruct(5) for details.
550    * ignored by busyboxed version
551-x cdb
552    read instructions for handling new connections from the constant database
553    cdb. The constant database normally is created from an instructions
554    directory by running ipsvd-cdb(8).
555    * ignored by busyboxed version
556-t sec
557    timeout. This option only takes effect if the -i option is given.
558    While checking the instructions directory, check the time of last access
559    of the file that matches the clients address or hostname if any, discard
560    and remove the file if it wasn't accessed within the last sec seconds;
561    tcpsvd does not discard or remove a file if the user's write permission
562    is not set, for those files the timeout is disabled. Default is 0,
563    which means that the timeout is disabled.
564    * ignored by busyboxed version
565-l name
566    local hostname. Do not look up the local hostname in DNS, but use name
567    as hostname. This option must be set if tcpsvd listens on port 53
568    to avoid loops.
569-u user[:group]
570    drop permissions. Switch user ID to user's UID, and group ID to user's
571    primary GID after creating and binding to the socket. If user is followed
572    by a colon and a group name, the group ID is switched to the GID of group
573    instead. All supplementary groups are removed.
574-c n
575    concurrency. Handle up to n connections simultaneously. Default is 30.
576    If there are n connections active, tcpsvd defers acceptance of a new
577    connection until an active connection is closed.
578-C n[:msg]
579    per host concurrency. Allow only up to n connections from the same IP
580    address simultaneously. If there are n active connections from one IP
581    address, new incoming connections from this IP address are closed
582    immediately. If n is followed by :msg, the message msg is written
583    to the client if possible, before closing the connection. By default
584    msg is empty. See ipsvd-instruct(5) for supported escape sequences in msg.
585
586    For each accepted connection, the current per host concurrency is
587    available through the environment variable TCPCONCURRENCY. n and msg
588    can be overwritten by ipsvd(7) instructions, see ipsvd-instruct(5).
589    By default tcpsvd doesn't keep track of connections.
590-h
591    Look up the client's hostname in DNS.
592-p
593    paranoid. After looking up the client's hostname in DNS, look up the IP
594    addresses in DNS for that hostname, and forget about the hostname
595    if none of the addresses match the client's IP address. You should
596    set this option if you use hostname based instructions. The -p option
597    implies the -h option.
598    * ignored by busyboxed version
599-b n
600    backlog. Allow a backlog of approximately n TCP SYNs. On some systems n
601    is silently limited. Default is 20.
602-E
603    no special environment. Do not set up TCP-related environment variables.
604-v
605    verbose. Print verbose messsages to standard output.
606-vv
607    more verbose. Print more verbose messages to standard output.
608    * no difference between -v and -vv in busyboxed version
609*/
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