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https://github.com/sheumann/hush.git
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558 lines
17 KiB
C
558 lines
17 KiB
C
/* Based on ipsvd utilities written by Gerrit Pape <pape@smarden.org>
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* which are released into public domain by the author.
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* Homepage: http://smarden.sunsite.dk/ipsvd/
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*
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* Copyright (C) 2007 Denis Vlasenko.
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*
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* Licensed under GPLv2, see file LICENSE in this tarball for details.
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*/
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/* Based on ipsvd ipsvd-0.12.1. This tcpsvd accepts all options
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* which are supported by one from ipsvd-0.12.1, but not all are
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* functional. See help text at the end of this file for details.
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*
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* Code inside "#ifdef SSLSVD" is for sslsvd and is currently unused.
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*
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* Output of verbose mode matches original (modulo bugs and
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* unimplemented stuff). Unnatural splitting of IP and PORT
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* is retained (personally I prefer one-value "IP:PORT" notation -
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* it is a natural string representation of struct sockaddr_XX).
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*
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* TCPORIGDST{IP,PORT} is busybox-specific addition
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*
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* udp server is hacked up by reusing TCP code. It has the following
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* limitation inherent in Unix DGRAM sockets implementation:
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* - local IP address is retrieved (using recvmsg voodoo) but
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* child's socket is not bound to it (bind cannot be called on
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* already bound socket). Thus it still can emit outgoing packets
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* with wrong source IP...
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* - don't know how to retrieve ORIGDST for udp.
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*/
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#include <limits.h>
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#include <linux/netfilter_ipv4.h> /* wants <limits.h> */
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#include "busybox.h"
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#include "ipsvd_perhost.h"
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#ifdef SSLSVD
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#include "matrixSsl.h"
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#include "ssl_io.h"
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#endif
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static unsigned verbose;
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static unsigned max_per_host;
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static unsigned cur_per_host;
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static unsigned cnum;
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static unsigned cmax = 30;
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static void xsetenv_proto(const char *proto, const char *n, const char *v)
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{
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putenv(xasprintf("%s%s=%s", proto, n, v));
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}
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static void sig_term_handler(int sig)
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{
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if (verbose)
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printf("%s: info: sigterm received, exit\n", applet_name);
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exit(0);
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}
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/* Little bloated, but tries to give accurate info how child exited.
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* Makes easier to spot segfaulting children etc... */
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static void print_waitstat(unsigned pid, int wstat)
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{
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unsigned e = 0;
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const char *cause = "?exit";
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if (WIFEXITED(wstat)) {
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cause++;
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e = WEXITSTATUS(wstat);
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} else if (WIFSIGNALED(wstat)) {
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cause = "signal";
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e = WTERMSIG(wstat);
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}
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printf("%s: info: end %d %s %d\n", applet_name, pid, cause, e);
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}
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/* Must match getopt32 in main! */
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enum {
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OPT_c = (1 << 0),
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OPT_C = (1 << 1),
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OPT_i = (1 << 2),
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OPT_x = (1 << 3),
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OPT_u = (1 << 4),
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OPT_l = (1 << 5),
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OPT_E = (1 << 6),
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OPT_b = (1 << 7),
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OPT_h = (1 << 8),
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OPT_p = (1 << 9),
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OPT_t = (1 << 10),
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OPT_v = (1 << 11),
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OPT_V = (1 << 12),
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OPT_U = (1 << 13), /* from here: sslsvd only */
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OPT_slash = (1 << 14),
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OPT_Z = (1 << 15),
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OPT_K = (1 << 16),
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};
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static void connection_status(void)
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{
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/* "only 1 client max" don't need this */
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if (cmax > 1)
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printf("%s: info: status %u/%u\n", applet_name, cnum, cmax);
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}
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static void sig_child_handler(int sig)
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{
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int wstat;
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int pid;
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while ((pid = wait_nohang(&wstat)) > 0) {
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if (max_per_host)
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ipsvd_perhost_remove(pid);
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if (cnum)
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cnum--;
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if (verbose)
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print_waitstat(pid, wstat);
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}
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if (verbose)
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connection_status();
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}
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int tcpudpsvd_main(int argc, char **argv);
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int tcpudpsvd_main(int argc, char **argv)
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{
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char *str_c, *str_C, *str_b, *str_t;
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char *user;
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struct hcc *hccp;
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const char *instructs;
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char *msg_per_host = NULL;
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unsigned len_per_host = len_per_host; /* gcc */
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#ifndef SSLSVD
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struct bb_uidgid_t ugid;
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#endif
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bool need_hostnames, need_remote_ip, tcp;
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uint16_t local_port;
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char *local_hostname = NULL;
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char *remote_hostname = (char*)""; /* "" used if no -h */
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char *local_addr = local_addr; /* gcc */
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char *remote_addr = remote_addr; /* gcc */
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char *remote_ip = remote_addr; /* gcc */
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len_and_sockaddr *lsa;
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len_and_sockaddr local, remote;
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socklen_t sa_len;
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int pid;
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int sock;
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int conn;
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unsigned backlog = 20;
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tcp = (applet_name[0] == 't');
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/* 3+ args, -i at most once, -p implies -h, -v is counter */
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opt_complementary = "-3:?:i--i:ph:vv";
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#ifdef SSLSVD
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getopt32(argc, argv, "+c:C:i:x:u:l:Eb:hpt:vU:/:Z:K:",
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&str_c, &str_C, &instructs, &instructs, &user, &local_hostname,
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&str_b, &str_t, &ssluser, &root, &cert, &key, &verbose
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);
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#else
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getopt32(argc, argv, "+c:C:i:x:u:l:Eb:hpt:v",
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&str_c, &str_C, &instructs, &instructs, &user, &local_hostname,
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&str_b, &str_t, &verbose
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);
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#endif
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if (option_mask32 & OPT_c)
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cmax = xatou_range(str_c, 1, INT_MAX);
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if (option_mask32 & OPT_C) { /* -C n[:message] */
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max_per_host = bb_strtou(str_C, &str_C, 10);
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if (str_C[0]) {
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if (str_C[0] != ':')
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bb_show_usage();
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msg_per_host = str_C + 1;
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len_per_host = strlen(msg_per_host);
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}
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}
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if (max_per_host > cmax)
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max_per_host = cmax;
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if (option_mask32 & OPT_u) {
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if (!get_uidgid(&ugid, user, 1))
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bb_error_msg_and_die("unknown user/group: %s", user);
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}
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if (option_mask32 & OPT_b)
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backlog = xatou(str_b);
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#ifdef SSLSVD
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if (option_mask32 & OPT_U) ssluser = optarg;
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if (option_mask32 & OPT_slash) root = optarg;
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if (option_mask32 & OPT_Z) cert = optarg;
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if (option_mask32 & OPT_K) key = optarg;
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#endif
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argv += optind;
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if (!argv[0][0] || LONE_CHAR(argv[0], '0'))
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argv[0] = (char*)"0.0.0.0";
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/* Per-IP flood protection is not thought-out for UDP */
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if (!tcp)
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max_per_host = 0;
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/* stdout is used for logging, don't buffer */
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setlinebuf(stdout);
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bb_sanitize_stdio(); /* fd# 0,1,2 must be opened */
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need_hostnames = verbose || !(option_mask32 & OPT_E);
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need_remote_ip = max_per_host || need_hostnames;
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#ifdef SSLSVD
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sslser = user;
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client = 0;
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if ((getuid() == 0) && !(option_mask32 & OPT_u)) {
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xfunc_exitcode = 100;
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bb_error_msg_and_die("fatal: -U ssluser must be set when running as root");
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}
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if (option_mask32 & OPT_u)
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if (!uidgid_get(&sslugid, ssluser, 1)) {
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if (errno) {
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bb_perror_msg_and_die("fatal: cannot get user/group: %s", ssluser);
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}
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bb_error_msg_and_die("fatal: unknown user/group '%s'", ssluser);
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}
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if (!cert) cert = "./cert.pem";
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if (!key) key = cert;
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if (matrixSslOpen() < 0)
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fatal("cannot initialize ssl");
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if (matrixSslReadKeys(&keys, cert, key, 0, ca) < 0) {
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if (client)
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fatal("cannot read cert, key, or ca file");
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fatal("cannot read cert or key file");
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}
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if (matrixSslNewSession(&ssl, keys, 0, SSL_FLAGS_SERVER) < 0)
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fatal("cannot create ssl session");
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#endif
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sig_block(SIGCHLD);
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signal(SIGCHLD, sig_child_handler);
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signal(SIGTERM, sig_term_handler);
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signal(SIGPIPE, SIG_IGN);
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if (max_per_host)
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ipsvd_perhost_init(cmax);
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local_port = bb_lookup_port(argv[1], tcp ? "tcp" : "udp", 0);
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lsa = xhost2sockaddr(argv[0], local_port);
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sock = xsocket(lsa->sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
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setsockopt_reuseaddr(sock);
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sa_len = lsa->len; /* I presume sockaddr len stays the same */
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xbind(sock, &lsa->sa, sa_len);
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if (tcp)
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xlisten(sock, backlog);
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else /* udp: needed for recv_from_to to work: */
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socket_want_pktinfo(sock);
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/* ndelay_off(sock); - it is the default I think? */
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#ifndef SSLSVD
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if (option_mask32 & OPT_u) {
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/* drop permissions */
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xsetgid(ugid.gid);
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xsetuid(ugid.uid);
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}
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#endif
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if (verbose) {
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char *addr = xmalloc_sockaddr2dotted(&lsa->sa, sa_len);
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printf("%s: info: listening on %s", applet_name, addr);
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free(addr);
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#ifndef SSLSVD
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if (option_mask32 & OPT_u)
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printf(", uid %u, gid %u",
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(unsigned)ugid.uid, (unsigned)ugid.gid);
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#endif
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puts(", starting");
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}
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/* Main accept() loop */
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again:
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hccp = NULL;
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while (cnum >= cmax)
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sig_pause(); /* wait for any signal (expecting SIGCHLD) */
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/* Accept a connection to fd #0 */
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again1:
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close(0);
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again2:
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sig_unblock(SIGCHLD);
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if (tcp) {
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remote.len = sa_len;
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conn = accept(sock, &remote.sa, &remote.len);
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} else {
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/* In case recv_from_to won't be able to recover local addr.
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* Also sets port - recv_from_to is unable to do it. */
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local = *lsa;
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conn = recv_from_to(sock, NULL, 0, MSG_PEEK, &remote.sa, &local.sa, sa_len);
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}
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sig_block(SIGCHLD);
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if (conn < 0) {
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if (errno != EINTR)
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bb_perror_msg(tcp ? "accept" : "recv");
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goto again2;
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}
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xmove_fd(tcp ? conn : sock, 0);
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if (max_per_host) {
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/* Drop connection immediately if cur_per_host > max_per_host
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* (minimizing load under SYN flood) */
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remote_ip = xmalloc_sockaddr2dotted_noport(&remote.sa, sa_len);
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cur_per_host = ipsvd_perhost_add(remote_ip, max_per_host, &hccp);
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if (cur_per_host > max_per_host) {
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/* ipsvd_perhost_add detected that max is exceeded
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* (and did not store ip in connection table) */
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free(remote_ip);
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if (msg_per_host) {
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/* don't block or test for errors */
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ndelay_on(0);
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write(0, msg_per_host, len_per_host);
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}
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goto again1;
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}
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}
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if (!tcp) {
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/* Voodoo magic: making udp sockets each receive its own
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* packets is not trivial, and I still not sure
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* I do it 100% right.
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* 1) we have to do it before fork()
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* 2) order is important - is it right now? */
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/* Make plain write/send work for this socket by supplying default
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* destination address. This also restricts incoming packets
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* to ones coming from this remote IP. */
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xconnect(0, &remote.sa, sa_len);
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/* hole? at this point we have no wildcard udp socket...
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* can this cause clients to get "port unreachable" icmp?
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* Yup, time window is very small, but it exists (is it?) */
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/* Open new non-connected UDP socket for further clients */
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sock = xsocket(lsa->sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
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setsockopt_reuseaddr(sock);
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xbind(sock, &lsa->sa, sa_len);
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socket_want_pktinfo(sock);
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/* Doesn't work:
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* we cannot replace fd #0 - we will lose pending packet
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* which is already buffered for us! And we cannot use fd #1
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* instead - it will "intercept" all following packets, but child
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* do not expect data coming *from fd #1*! */
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#if 0
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/* Make it so that local addr is fixed to localp->sa
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* and we don't accidentally accept packets to other local IPs. */
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/* NB: we possibly bind to the _very_ same_ address & port as the one
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* already bound in parent! This seems to work in Linux.
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* (otherwise we can move socket to fd #0 only if bind succeeds) */
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close(0);
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set_nport(localp, htons(local_port));
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xmove_fd(xsocket(localp->sa.sa_family, SOCK_DGRAM, 0), 0);
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setsockopt_reuseaddr(0); /* crucial */
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xbind(0, &localp->sa, localp->len);
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#endif
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}
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pid = fork();
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if (pid == -1) {
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bb_perror_msg("fork");
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goto again;
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}
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if (pid != 0) {
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/* parent */
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cnum++;
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if (verbose)
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connection_status();
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if (hccp)
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hccp->pid = pid;
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goto again;
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}
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/* Child: prepare env, log, and exec prog */
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/* Closing tcp listening socket */
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if (tcp)
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close(sock);
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if (need_remote_ip)
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remote_addr = xmalloc_sockaddr2dotted(&remote.sa, sa_len);
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if (need_hostnames) {
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if (option_mask32 & OPT_h) {
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remote_hostname = xmalloc_sockaddr2host_noport(&remote.sa, sa_len);
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if (!remote_hostname) {
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bb_error_msg("warning: cannot look up hostname for %s", remote_addr);
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remote_hostname = (char*)"";
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}
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}
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/* Find out local IP peer connected to.
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* Errors ignored (I'm not paranoid enough to imagine kernel
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* which doesn't know local IP). */
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if (tcp) {
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local.len = sa_len;
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getsockname(0, &local.sa, &local.len);
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}
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local_addr = xmalloc_sockaddr2dotted(&local.sa, sa_len);
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if (!local_hostname) {
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local_hostname = xmalloc_sockaddr2host_noport(&local.sa, sa_len);
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if (!local_hostname)
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bb_error_msg_and_die("warning: cannot look up hostname for %s"+9, local_addr);
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}
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}
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if (verbose) {
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pid = getpid();
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printf("%s: info: pid %u from %s\n", applet_name, pid, remote_addr);
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if (max_per_host)
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printf("%s: info: concurrency %u %s %u/%u\n",
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applet_name, pid, remote_ip, cur_per_host, max_per_host);
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printf("%s: info: start %u %s:%s :%s:%s\n",
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applet_name, pid,
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local_hostname, local_addr,
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remote_hostname, remote_addr);
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}
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if (!(option_mask32 & OPT_E)) {
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/* setup ucspi env */
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const char *proto = tcp ? "TCP" : "UDP";
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/* Extract "original" destination addr:port
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* from Linux firewall. Useful when you redirect
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* an outbond connection to local handler, and it needs
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* to know where it originally tried to connect */
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if (tcp && getsockopt(0, SOL_IP, SO_ORIGINAL_DST, &lsa->sa, &lsa->len) == 0) {
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char *addr = xmalloc_sockaddr2dotted(&lsa->sa, sa_len);
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xsetenv("TCPORIGDSTADDR", addr);
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free(addr);
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}
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xsetenv("PROTO", proto);
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xsetenv_proto(proto, "LOCALADDR", local_addr);
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xsetenv_proto(proto, "LOCALHOST", local_hostname);
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xsetenv_proto(proto, "REMOTEADDR", remote_addr);
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if (option_mask32 & OPT_h) {
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xsetenv_proto(proto, "REMOTEHOST", remote_hostname);
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}
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xsetenv_proto(proto, "REMOTEINFO", "");
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/* additional */
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if (cur_per_host > 0) /* can not be true for udp */
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xsetenv("TCPCONCURRENCY", utoa(cur_per_host));
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}
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dup2(0, 1);
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signal(SIGTERM, SIG_DFL);
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signal(SIGPIPE, SIG_DFL);
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signal(SIGCHLD, SIG_DFL);
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sig_unblock(SIGCHLD);
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argv += 2;
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#ifdef SSLSVD
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strcpy(id, utoa(pid);
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ssl_io(0, argv);
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#else
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BB_EXECVP(argv[0], argv);
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#endif
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bb_perror_msg_and_die("exec '%s'", argv[0]);
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}
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/*
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tcpsvd [-hpEvv] [-c n] [-C n:msg] [-b n] [-u user] [-l name]
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[-i dir|-x cdb] [ -t sec] host port prog
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tcpsvd creates a TCP/IP socket, binds it to the address host:port,
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and listens on the socket for incoming connections.
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On each incoming connection, tcpsvd conditionally runs a program,
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with standard input reading from the socket, and standard output
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writing to the socket, to handle this connection. tcpsvd keeps
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listening on the socket for new connections, and can handle
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multiple connections simultaneously.
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tcpsvd optionally checks for special instructions depending
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on the IP address or hostname of the client that initiated
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the connection, see ipsvd-instruct(5).
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host
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host either is a hostname, or a dotted-decimal IP address,
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or 0. If host is 0, tcpsvd accepts connections to any local
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IP address.
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* busybox accepts IPv6 addresses and host:port pairs too
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In this case second parameter is ignored
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port
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tcpsvd accepts connections to host:port. port may be a name
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from /etc/services or a number.
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prog
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prog consists of one or more arguments. For each connection,
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tcpsvd normally runs prog, with file descriptor 0 reading from
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the network, and file descriptor 1 writing to the network.
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By default it also sets up TCP-related environment variables,
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see tcp-environ(5)
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-i dir
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read instructions for handling new connections from the instructions
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directory dir. See ipsvd-instruct(5) for details.
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* ignored by busyboxed version
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-x cdb
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read instructions for handling new connections from the constant database
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cdb. The constant database normally is created from an instructions
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directory by running ipsvd-cdb(8).
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* ignored by busyboxed version
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-t sec
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timeout. This option only takes effect if the -i option is given.
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While checking the instructions directory, check the time of last access
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of the file that matches the clients address or hostname if any, discard
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and remove the file if it wasn't accessed within the last sec seconds;
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tcpsvd does not discard or remove a file if the user's write permission
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is not set, for those files the timeout is disabled. Default is 0,
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which means that the timeout is disabled.
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* ignored by busyboxed version
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-l name
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local hostname. Do not look up the local hostname in DNS, but use name
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as hostname. This option must be set if tcpsvd listens on port 53
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to avoid loops.
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-u user[:group]
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drop permissions. Switch user ID to user's UID, and group ID to user's
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primary GID after creating and binding to the socket. If user is followed
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by a colon and a group name, the group ID is switched to the GID of group
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instead. All supplementary groups are removed.
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-c n
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concurrency. Handle up to n connections simultaneously. Default is 30.
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If there are n connections active, tcpsvd defers acceptance of a new
|
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connection until an active connection is closed.
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-C n[:msg]
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per host concurrency. Allow only up to n connections from the same IP
|
|
address simultaneously. If there are n active connections from one IP
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address, new incoming connections from this IP address are closed
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immediately. If n is followed by :msg, the message msg is written
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to the client if possible, before closing the connection. By default
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msg is empty. See ipsvd-instruct(5) for supported escape sequences in msg.
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For each accepted connection, the current per host concurrency is
|
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available through the environment variable TCPCONCURRENCY. n and msg
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can be overwritten by ipsvd(7) instructions, see ipsvd-instruct(5).
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By default tcpsvd doesn't keep track of connections.
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-h
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Look up the client's hostname in DNS.
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-p
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paranoid. After looking up the client's hostname in DNS, look up the IP
|
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addresses in DNS for that hostname, and forget about the hostname
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if none of the addresses match the client's IP address. You should
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set this option if you use hostname based instructions. The -p option
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implies the -h option.
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* ignored by busyboxed version
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-b n
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backlog. Allow a backlog of approximately n TCP SYNs. On some systems n
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is silently limited. Default is 20.
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-E
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no special environment. Do not set up TCP-related environment variables.
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-v
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verbose. Print verbose messsages to standard output.
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-vv
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more verbose. Print more verbose messages to standard output.
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* no difference between -v and -vv in busyboxed version
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|
*/
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