diff options
Diffstat (limited to 'networking/tcpudp.c')
| -rw-r--r-- | networking/tcpudp.c | 609 |
1 files changed, 609 insertions, 0 deletions
diff --git a/networking/tcpudp.c b/networking/tcpudp.c new file mode 100644 index 0000000..f977874 --- /dev/null +++ b/networking/tcpudp.c @@ -0,0 +1,609 @@ +/* Based on ipsvd utilities written by Gerrit Pape <pape@smarden.org> + * which are released into public domain by the author. + * Homepage: http://smarden.sunsite.dk/ipsvd/ + * + * Copyright (C) 2007 Denys Vlasenko. + * + * Licensed under GPLv2, see file LICENSE in this tarball for details. + */ + +/* Based on ipsvd-0.12.1. This tcpsvd accepts all options + * which are supported by one from ipsvd-0.12.1, but not all are + * functional. See help text at the end of this file for details. + * + * Code inside "#ifdef SSLSVD" is for sslsvd and is currently unused. + * + * Busybox version exports TCPLOCALADDR instead of + * TCPLOCALIP + TCPLOCALPORT pair. ADDR more closely matches reality + * (which is "struct sockaddr_XXX". Port is not a separate entity, + * it's just a part of (AF_INET[6]) sockaddr!). + * + * TCPORIGDSTADDR is Busybox-specific addition. + * + * udp server is hacked up by reusing TCP code. It has the following + * limitation inherent in Unix DGRAM sockets implementation: + * - local IP address is retrieved (using recvmsg voodoo) but + * child's socket is not bound to it (bind cannot be called on + * already bound socket). Thus it still can emit outgoing packets + * with wrong source IP... + * - don't know how to retrieve ORIGDST for udp. + */ + +#include <limits.h> +#include <linux/netfilter_ipv4.h> /* wants <limits.h> */ + +#include "libbb.h" +// TODO: move into this file: +#include "tcpudp_perhost.h" + +#ifdef SSLSVD +#include "matrixSsl.h" +#include "ssl_io.h" +#endif + +struct globals { + unsigned verbose; + unsigned max_per_host; + unsigned cur_per_host; + unsigned cnum; + unsigned cmax; + char **env_cur; + char *env_var[1]; /* actually bigger */ +}; +#define G (*(struct globals*)&bb_common_bufsiz1) +#define verbose (G.verbose ) +#define max_per_host (G.max_per_host) +#define cur_per_host (G.cur_per_host) +#define cnum (G.cnum ) +#define cmax (G.cmax ) +#define env_cur (G.env_cur ) +#define env_var (G.env_var ) +#define INIT_G() \ + do { \ + cmax = 30; \ + env_cur = &env_var[0]; \ + } while (0) + + +/* We have to be careful about leaking memory in repeated setenv's */ +static void xsetenv_plain(const char *n, const char *v) +{ + char *var = xasprintf("%s=%s", n, v); + *env_cur++ = var; + putenv(var); +} + +static void xsetenv_proto(const char *proto, const char *n, const char *v) +{ + char *var = xasprintf("%s%s=%s", proto, n, v); + *env_cur++ = var; + putenv(var); +} + +static void undo_xsetenv(void) +{ + char **pp = env_cur = &env_var[0]; + while (*pp) { + char *var = *pp; + *strchrnul(var, '=') = '\0'; + unsetenv(var); + free(var); + *pp++ = NULL; + } +} + +static void sig_term_handler(int sig) +{ + if (verbose) + bb_error_msg("got signal %u, exit", sig); + kill_myself_with_sig(sig); +} + +/* Little bloated, but tries to give accurate info how child exited. + * Makes easier to spot segfaulting children etc... */ +static void print_waitstat(unsigned pid, int wstat) +{ + unsigned e = 0; + const char *cause = "?exit"; + + if (WIFEXITED(wstat)) { + cause++; + e = WEXITSTATUS(wstat); + } else if (WIFSIGNALED(wstat)) { + cause = "signal"; + e = WTERMSIG(wstat); + } + bb_error_msg("end %d %s %d", pid, cause, e); +} + +/* Must match getopt32 in main! */ +enum { + OPT_c = (1 << 0), + OPT_C = (1 << 1), + OPT_i = (1 << 2), + OPT_x = (1 << 3), + OPT_u = (1 << 4), + OPT_l = (1 << 5), + OPT_E = (1 << 6), + OPT_b = (1 << 7), + OPT_h = (1 << 8), + OPT_p = (1 << 9), + OPT_t = (1 << 10), + OPT_v = (1 << 11), + OPT_V = (1 << 12), + OPT_U = (1 << 13), /* from here: sslsvd only */ + OPT_slash = (1 << 14), + OPT_Z = (1 << 15), + OPT_K = (1 << 16), +}; + +static void connection_status(void) +{ + /* "only 1 client max" desn't need this */ + if (cmax > 1) + bb_error_msg("status %u/%u", cnum, cmax); +} + +static void sig_child_handler(int sig ATTRIBUTE_UNUSED) +{ + int wstat; + int pid; + + while ((pid = wait_any_nohang(&wstat)) > 0) { + if (max_per_host) + ipsvd_perhost_remove(pid); + if (cnum) + cnum--; + if (verbose) + print_waitstat(pid, wstat); + } + if (verbose) + connection_status(); +} + +int tcpudpsvd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; +int tcpudpsvd_main(int argc ATTRIBUTE_UNUSED, char **argv) +{ + char *str_C, *str_t; + char *user; + struct hcc *hccp; + const char *instructs; + char *msg_per_host = NULL; + unsigned len_per_host = len_per_host; /* gcc */ +#ifndef SSLSVD + struct bb_uidgid_t ugid; +#endif + bool tcp; + uint16_t local_port; + char *preset_local_hostname = NULL; + char *remote_hostname = remote_hostname; /* for compiler */ + char *remote_addr = remote_addr; /* for compiler */ + len_and_sockaddr *lsa; + len_and_sockaddr local, remote; + socklen_t sa_len; + int pid; + int sock; + int conn; + unsigned backlog = 20; + + INIT_G(); + + tcp = (applet_name[0] == 't'); + + /* 3+ args, -i at most once, -p implies -h, -v is counter, -b N, -c N */ + opt_complementary = "-3:i--i:ph:vv:b+:c+"; +#ifdef SSLSVD + getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:vU:/:Z:K:", + &cmax, &str_C, &instructs, &instructs, &user, &preset_local_hostname, + &backlog, &str_t, &ssluser, &root, &cert, &key, &verbose + ); +#else + /* "+": stop on first non-option */ + getopt32(argv, "+c:C:i:x:u:l:Eb:hpt:v", + &cmax, &str_C, &instructs, &instructs, &user, &preset_local_hostname, + &backlog, &str_t, &verbose + ); +#endif + if (option_mask32 & OPT_C) { /* -C n[:message] */ + max_per_host = bb_strtou(str_C, &str_C, 10); + if (str_C[0]) { + if (str_C[0] != ':') + bb_show_usage(); + msg_per_host = str_C + 1; + len_per_host = strlen(msg_per_host); + } + } + if (max_per_host > cmax) + max_per_host = cmax; + if (option_mask32 & OPT_u) { + if (!get_uidgid(&ugid, user, 1)) + bb_error_msg_and_die("unknown user/group: %s", user); + } +#ifdef SSLSVD + if (option_mask32 & OPT_U) ssluser = optarg; + if (option_mask32 & OPT_slash) root = optarg; + if (option_mask32 & OPT_Z) cert = optarg; + if (option_mask32 & OPT_K) key = optarg; +#endif + argv += optind; + if (!argv[0][0] || LONE_CHAR(argv[0], '0')) + argv[0] = (char*)"0.0.0.0"; + + /* Per-IP flood protection is not thought-out for UDP */ + if (!tcp) + max_per_host = 0; + + bb_sanitize_stdio(); /* fd# 0,1,2 must be opened */ + +#ifdef SSLSVD + sslser = user; + client = 0; + if ((getuid() == 0) && !(option_mask32 & OPT_u)) { + xfunc_exitcode = 100; + bb_error_msg_and_die("-U ssluser must be set when running as root"); + } + if (option_mask32 & OPT_u) + if (!uidgid_get(&sslugid, ssluser, 1)) { + if (errno) { + bb_perror_msg_and_die("fatal: cannot get user/group: %s", ssluser); + } + bb_error_msg_and_die("unknown user/group '%s'", ssluser); + } + if (!cert) cert = "./cert.pem"; + if (!key) key = cert; + if (matrixSslOpen() < 0) + fatal("cannot initialize ssl"); + if (matrixSslReadKeys(&keys, cert, key, 0, ca) < 0) { + if (client) + fatal("cannot read cert, key, or ca file"); + fatal("cannot read cert or key file"); + } + if (matrixSslNewSession(&ssl, keys, 0, SSL_FLAGS_SERVER) < 0) + fatal("cannot create ssl session"); +#endif + + sig_block(SIGCHLD); + signal(SIGCHLD, sig_child_handler); + bb_signals(BB_SIGS_FATAL, sig_term_handler); + signal(SIGPIPE, SIG_IGN); + + if (max_per_host) + ipsvd_perhost_init(cmax); + + local_port = bb_lookup_port(argv[1], tcp ? "tcp" : "udp", 0); + lsa = xhost2sockaddr(argv[0], local_port); + argv += 2; + + sock = xsocket(lsa->u.sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0); + setsockopt_reuseaddr(sock); + sa_len = lsa->len; /* I presume sockaddr len stays the same */ + xbind(sock, &lsa->u.sa, sa_len); + if (tcp) + xlisten(sock, backlog); + else /* udp: needed for recv_from_to to work: */ + socket_want_pktinfo(sock); + /* ndelay_off(sock); - it is the default I think? */ + +#ifndef SSLSVD + if (option_mask32 & OPT_u) { + /* drop permissions */ + xsetgid(ugid.gid); + xsetuid(ugid.uid); + } +#endif + + if (verbose) { + char *addr = xmalloc_sockaddr2dotted(&lsa->u.sa); + bb_error_msg("listening on %s, starting", addr); + free(addr); +#ifndef SSLSVD + if (option_mask32 & OPT_u) + printf(", uid %u, gid %u", + (unsigned)ugid.uid, (unsigned)ugid.gid); +#endif + } + + /* Main accept() loop */ + + again: + hccp = NULL; + + while (cnum >= cmax) + wait_for_any_sig(); /* expecting SIGCHLD */ + + /* Accept a connection to fd #0 */ + again1: + close(0); + again2: + sig_unblock(SIGCHLD); + local.len = remote.len = sa_len; + if (tcp) { + conn = accept(sock, &remote.u.sa, &remote.len); + } else { + /* In case recv_from_to won't be able to recover local addr. + * Also sets port - recv_from_to is unable to do it. */ + local = *lsa; + conn = recv_from_to(sock, NULL, 0, MSG_PEEK, + &remote.u.sa, &local.u.sa, sa_len); + } + sig_block(SIGCHLD); + if (conn < 0) { + if (errno != EINTR) + bb_perror_msg(tcp ? "accept" : "recv"); + goto again2; + } + xmove_fd(tcp ? conn : sock, 0); + + if (max_per_host) { + /* Drop connection immediately if cur_per_host > max_per_host + * (minimizing load under SYN flood) */ + remote_addr = xmalloc_sockaddr2dotted_noport(&remote.u.sa); + cur_per_host = ipsvd_perhost_add(remote_addr, max_per_host, &hccp); + if (cur_per_host > max_per_host) { + /* ipsvd_perhost_add detected that max is exceeded + * (and did not store ip in connection table) */ + free(remote_addr); + if (msg_per_host) { + /* don't block or test for errors */ + send(0, msg_per_host, len_per_host, MSG_DONTWAIT); + } + goto again1; + } + /* NB: remote_addr is not leaked, it is stored in conn table */ + } + + if (!tcp) { + /* Voodoo magic: making udp sockets each receive its own + * packets is not trivial, and I still not sure + * I do it 100% right. + * 1) we have to do it before fork() + * 2) order is important - is it right now? */ + + /* Open new non-connected UDP socket for further clients... */ + sock = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0); + setsockopt_reuseaddr(sock); + /* Make plain write/send work for old socket by supplying default + * destination address. This also restricts incoming packets + * to ones coming from this remote IP. */ + xconnect(0, &remote.u.sa, sa_len); + /* hole? at this point we have no wildcard udp socket... + * can this cause clients to get "port unreachable" icmp? + * Yup, time window is very small, but it exists (is it?) */ + /* ..."open new socket", continued */ + xbind(sock, &lsa->u.sa, sa_len); + socket_want_pktinfo(sock); + + /* Doesn't work: + * we cannot replace fd #0 - we will lose pending packet + * which is already buffered for us! And we cannot use fd #1 + * instead - it will "intercept" all following packets, but child + * does not expect data coming *from fd #1*! */ +#if 0 + /* Make it so that local addr is fixed to localp->u.sa + * and we don't accidentally accept packets to other local IPs. */ + /* NB: we possibly bind to the _very_ same_ address & port as the one + * already bound in parent! This seems to work in Linux. + * (otherwise we can move socket to fd #0 only if bind succeeds) */ + close(0); + set_nport(localp, htons(local_port)); + xmove_fd(xsocket(localp->u.sa.sa_family, SOCK_DGRAM, 0), 0); + setsockopt_reuseaddr(0); /* crucial */ + xbind(0, &localp->u.sa, localp->len); +#endif + } + + pid = vfork(); + if (pid == -1) { + bb_perror_msg("vfork"); + goto again; + } + + if (pid != 0) { + /* Parent */ + cnum++; + if (verbose) + connection_status(); + if (hccp) + hccp->pid = pid; + /* clean up changes done by vforked child */ + undo_xsetenv(); + goto again; + } + + /* Child: prepare env, log, and exec prog */ + + /* Closing tcp listening socket */ + if (tcp) + close(sock); + + { /* vfork alert! every xmalloc in this block should be freed! */ + char *local_hostname = local_hostname; /* for compiler */ + char *local_addr = NULL; + char *free_me0 = NULL; + char *free_me1 = NULL; + char *free_me2 = NULL; + + if (verbose || !(option_mask32 & OPT_E)) { + if (!max_per_host) /* remote_addr is not yet known */ + free_me0 = remote_addr = xmalloc_sockaddr2dotted(&remote.u.sa); + if (option_mask32 & OPT_h) { + free_me1 = remote_hostname = xmalloc_sockaddr2host_noport(&remote.u.sa); + if (!remote_hostname) { + bb_error_msg("cannot look up hostname for %s", remote_addr); + remote_hostname = remote_addr; + } + } + /* Find out local IP peer connected to. + * Errors ignored (I'm not paranoid enough to imagine kernel + * which doesn't know local IP). */ + if (tcp) + getsockname(0, &local.u.sa, &local.len); + /* else: for UDP it is done earlier by parent */ + local_addr = xmalloc_sockaddr2dotted(&local.u.sa); + if (option_mask32 & OPT_h) { + local_hostname = preset_local_hostname; + if (!local_hostname) { + free_me2 = local_hostname = xmalloc_sockaddr2host_noport(&local.u.sa); + if (!local_hostname) + bb_error_msg_and_die("cannot look up hostname for %s", local_addr); + } + /* else: local_hostname is not NULL, but is NOT malloced! */ + } + } + if (verbose) { + pid = getpid(); + if (max_per_host) { + bb_error_msg("concurrency %s %u/%u", + remote_addr, + cur_per_host, max_per_host); + } + bb_error_msg((option_mask32 & OPT_h) + ? "start %u %s-%s (%s-%s)" + : "start %u %s-%s", + pid, + local_addr, remote_addr, + local_hostname, remote_hostname); + } + + if (!(option_mask32 & OPT_E)) { + /* setup ucspi env */ + const char *proto = tcp ? "TCP" : "UDP"; + + /* Extract "original" destination addr:port + * from Linux firewall. Useful when you redirect + * an outbond connection to local handler, and it needs + * to know where it originally tried to connect */ + if (tcp && getsockopt(0, SOL_IP, SO_ORIGINAL_DST, &local.u.sa, &local.len) == 0) { + char *addr = xmalloc_sockaddr2dotted(&local.u.sa); + xsetenv_plain("TCPORIGDSTADDR", addr); + free(addr); + } + xsetenv_plain("PROTO", proto); + xsetenv_proto(proto, "LOCALADDR", local_addr); + xsetenv_proto(proto, "REMOTEADDR", remote_addr); + if (option_mask32 & OPT_h) { + xsetenv_proto(proto, "LOCALHOST", local_hostname); + xsetenv_proto(proto, "REMOTEHOST", remote_hostname); + } + //compat? xsetenv_proto(proto, "REMOTEINFO", ""); + /* additional */ + if (cur_per_host > 0) /* can not be true for udp */ + xsetenv_plain("TCPCONCURRENCY", utoa(cur_per_host)); + } + free(local_addr); + free(free_me0); + free(free_me1); + free(free_me2); + } + + xdup2(0, 1); + + signal(SIGTERM, SIG_DFL); + signal(SIGPIPE, SIG_DFL); + signal(SIGCHLD, SIG_DFL); + sig_unblock(SIGCHLD); + +#ifdef SSLSVD + strcpy(id, utoa(pid)); + ssl_io(0, argv); +#else + BB_EXECVP(argv[0], argv); +#endif + bb_perror_msg_and_die("exec '%s'", argv[0]); +} + +/* +tcpsvd [-hpEvv] [-c n] [-C n:msg] [-b n] [-u user] [-l name] + [-i dir|-x cdb] [ -t sec] host port prog + +tcpsvd creates a TCP/IP socket, binds it to the address host:port, +and listens on the socket for incoming connections. + +On each incoming connection, tcpsvd conditionally runs a program, +with standard input reading from the socket, and standard output +writing to the socket, to handle this connection. tcpsvd keeps +listening on the socket for new connections, and can handle +multiple connections simultaneously. + +tcpsvd optionally checks for special instructions depending +on the IP address or hostname of the client that initiated +the connection, see ipsvd-instruct(5). + +host + host either is a hostname, or a dotted-decimal IP address, + or 0. If host is 0, tcpsvd accepts connections to any local + IP address. + * busybox accepts IPv6 addresses and host:port pairs too + In this case second parameter is ignored +port + tcpsvd accepts connections to host:port. port may be a name + from /etc/services or a number. +prog + prog consists of one or more arguments. For each connection, + tcpsvd normally runs prog, with file descriptor 0 reading from + the network, and file descriptor 1 writing to the network. + By default it also sets up TCP-related environment variables, + see tcp-environ(5) +-i dir + read instructions for handling new connections from the instructions + directory dir. See ipsvd-instruct(5) for details. + * ignored by busyboxed version +-x cdb + read instructions for handling new connections from the constant database + cdb. The constant database normally is created from an instructions + directory by running ipsvd-cdb(8). + * ignored by busyboxed version +-t sec + timeout. This option only takes effect if the -i option is given. + While checking the instructions directory, check the time of last access + of the file that matches the clients address or hostname if any, discard + and remove the file if it wasn't accessed within the last sec seconds; + tcpsvd does not discard or remove a file if the user's write permission + is not set, for those files the timeout is disabled. Default is 0, + which means that the timeout is disabled. + * ignored by busyboxed version +-l name + local hostname. Do not look up the local hostname in DNS, but use name + as hostname. This option must be set if tcpsvd listens on port 53 + to avoid loops. +-u user[:group] + drop permissions. Switch user ID to user's UID, and group ID to user's + primary GID after creating and binding to the socket. If user is followed + by a colon and a group name, the group ID is switched to the GID of group + instead. All supplementary groups are removed. +-c n + concurrency. Handle up to n connections simultaneously. Default is 30. + If there are n connections active, tcpsvd defers acceptance of a new + connection until an active connection is closed. +-C n[:msg] + per host concurrency. Allow only up to n connections from the same IP + address simultaneously. If there are n active connections from one IP + address, new incoming connections from this IP address are closed + immediately. If n is followed by :msg, the message msg is written + to the client if possible, before closing the connection. By default + msg is empty. See ipsvd-instruct(5) for supported escape sequences in msg. + + For each accepted connection, the current per host concurrency is + available through the environment variable TCPCONCURRENCY. n and msg + can be overwritten by ipsvd(7) instructions, see ipsvd-instruct(5). + By default tcpsvd doesn't keep track of connections. +-h + Look up the client's hostname in DNS. +-p + paranoid. After looking up the client's hostname in DNS, look up the IP + addresses in DNS for that hostname, and forget about the hostname + if none of the addresses match the client's IP address. You should + set this option if you use hostname based instructions. The -p option + implies the -h option. + * ignored by busyboxed version +-b n + backlog. Allow a backlog of approximately n TCP SYNs. On some systems n + is silently limited. Default is 20. +-E + no special environment. Do not set up TCP-related environment variables. +-v + verbose. Print verbose messsages to standard output. +-vv + more verbose. Print more verbose messages to standard output. + * no difference between -v and -vv in busyboxed version +*/ |