/* $OpenBSD: tftp-proxy.c,v 1.1 2005/12/28 19:07:07 jcs Exp $ * * Copyright (c) 2005 DLS Internet Services * Copyright (c) 2004, 2005 Camiel Dobbelaar, * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "filter.h" #define CHROOT_DIR "/var/empty" #define NOPRIV_USER "proxy" #define PF_NAT_PROXY_PORT_LOW 50001 #define PF_NAT_PROXY_PORT_HIGH 65535 #define DEFTRANSWAIT 2 #define NTOP_BUFS 4 #define PKTSIZE SEGSIZE+4 const char *opcode(int); const char *sock_ntop(struct sockaddr *); u_int16_t pick_proxy_port(void); static void usage(void); extern char *__progname; char ntop_buf[NTOP_BUFS][INET6_ADDRSTRLEN]; int verbose = 0; int main(int argc, char *argv[]) { int c, fd = 0, on = 1, out_fd = 0, peer, reqsize = 0; int transwait = DEFTRANSWAIT; char *p; struct tftphdr *tp; struct passwd *pw; char cbuf[CMSG_SPACE(sizeof(struct sockaddr_storage))]; char req[PKTSIZE]; struct cmsghdr *cmsg; struct msghdr msg; struct iovec iov; struct sockaddr_storage from, proxy, server, proxy_to_server, s_in; struct sockaddr_in sock_out; socklen_t j; in_port_t bindport; openlog(__progname, LOG_PID | LOG_NDELAY, LOG_DAEMON); while ((c = getopt(argc, argv, "vw:")) != -1) switch (c) { case 'v': verbose++; break; case 'w': transwait = strtoll(optarg, &p, 10); if (transwait < 1) { syslog(LOG_ERR, "invalid -w value"); exit(1); } break; default: usage(); break; } /* open /dev/pf */ init_filter(NULL, verbose); tzset(); pw = getpwnam(NOPRIV_USER); if (!pw) { syslog(LOG_ERR, "no such user %s: %m", NOPRIV_USER); exit(1); } if (chroot(CHROOT_DIR) || chdir("/")) { syslog(LOG_ERR, "chroot %s: %m", CHROOT_DIR); exit(1); } if (setgroups(1, &pw->pw_gid) || setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) || setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid)) { syslog(LOG_ERR, "can't revoke privs: %m"); exit(1); } /* non-blocking io */ if (ioctl(fd, FIONBIO, &on) < 0) { syslog(LOG_ERR, "ioctl(FIONBIO): %m"); exit(1); } if (setsockopt(fd, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on)) == -1) { syslog(LOG_ERR, "setsockopt(IP_RECVDSTADDR): %m"); exit(1); } j = sizeof(s_in); if (getsockname(fd, (struct sockaddr *)&s_in, &j) == -1) { syslog(LOG_ERR, "getsockname: %m"); exit(1); } bindport = ((struct sockaddr_in *)&s_in)->sin_port; /* req will be pushed back out at the end, unchanged */ j = sizeof(from); if ((reqsize = recvfrom(fd, req, sizeof(req), MSG_PEEK, (struct sockaddr *)&from, &j)) < 0) { syslog(LOG_ERR, "recvfrom: %m"); exit(1); } bzero(&msg, sizeof(msg)); iov.iov_base = req; iov.iov_len = sizeof(req); msg.msg_name = &from; msg.msg_namelen = sizeof(from); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = cbuf; msg.msg_controllen = CMSG_LEN(sizeof(struct sockaddr_storage)); if (recvmsg(fd, &msg, 0) < 0) { syslog(LOG_ERR, "recvmsg: %m"); exit(1); } close(fd); close(1); peer = socket(from.ss_family, SOCK_DGRAM, 0); if (peer < 0) { syslog(LOG_ERR, "socket: %m"); exit(1); } memset(&s_in, 0, sizeof(s_in)); s_in.ss_family = from.ss_family; s_in.ss_len = from.ss_len; /* get local address if possible */ for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg)) { if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == IP_RECVDSTADDR) { memcpy(&((struct sockaddr_in *)&s_in)->sin_addr, CMSG_DATA(cmsg), sizeof(struct in_addr)); break; } } if (bind(peer, (struct sockaddr *)&s_in, s_in.ss_len) < 0) { syslog(LOG_ERR, "bind: %m"); exit(1); } if (connect(peer, (struct sockaddr *)&from, from.ss_len) < 0) { syslog(LOG_ERR, "connect: %m"); exit(1); } tp = (struct tftphdr *)req; if (!(ntohs(tp->th_opcode) == RRQ || ntohs(tp->th_opcode) == WRQ)) { /* not a tftp request, bail */ if (verbose) { syslog(LOG_WARNING, "not a valid tftp request"); exit(1); } else /* exit 0 so inetd doesn't log anything */ exit(0); } j = sizeof(struct sockaddr_storage); if (getsockname(fd, (struct sockaddr *)&proxy, &j) == -1) { syslog(LOG_ERR, "getsockname: %m"); exit(1); } ((struct sockaddr_in *)&proxy)->sin_port = bindport; /* find the un-rdr'd server and port the client wanted */ if (server_lookup((struct sockaddr *)&from, (struct sockaddr *)&proxy, (struct sockaddr *)&server, IPPROTO_UDP) != 0) { syslog(LOG_ERR, "pf connection lookup failed (no rdr?)"); exit(1); } /* establish a new outbound connection to the remote server */ if ((out_fd = socket(((struct sockaddr *)&from)->sa_family, SOCK_DGRAM, IPPROTO_UDP)) < 0) { syslog(LOG_ERR, "couldn't create new socket"); exit(1); } bzero((char *)&sock_out, sizeof(sock_out)); sock_out.sin_family = from.ss_family; sock_out.sin_port = htons(pick_proxy_port()); if (bind(out_fd, (struct sockaddr *)&sock_out, sizeof(sock_out)) < 0) { syslog(LOG_ERR, "couldn't bind to new socket: %m"); exit(1); } if (connect(out_fd, (struct sockaddr *)&server, ((struct sockaddr *)&server)->sa_len) < 0 && errno != EINPROGRESS) { syslog(LOG_ERR, "couldn't connect to remote server: %m"); exit(1); } j = sizeof(struct sockaddr_storage); if ((getsockname(out_fd, (struct sockaddr *)&proxy_to_server, &j)) < 0) { syslog(LOG_ERR, "getsockname: %m"); exit(1); } if (verbose) syslog(LOG_INFO, "%s:%d -> %s:%d/%s:%d -> %s:%d \"%s %s\"", sock_ntop((struct sockaddr *)&from), ntohs(((struct sockaddr_in *)&from)->sin_port), sock_ntop((struct sockaddr *)&proxy), ntohs(((struct sockaddr_in *)&proxy)->sin_port), sock_ntop((struct sockaddr *)&proxy_to_server), ntohs(((struct sockaddr_in *)&proxy_to_server)->sin_port), sock_ntop((struct sockaddr *)&server), ntohs(((struct sockaddr_in *)&server)->sin_port), opcode(ntohs(tp->th_opcode)), tp->th_stuff); /* get ready to add rdr and pass rules */ if (prepare_commit(1) == -1) { syslog(LOG_ERR, "couldn't prepare pf commit"); exit(1); } /* rdr from server to us on our random port -> client on its port */ if (add_rdr(1, (struct sockaddr *)&server, (struct sockaddr *)&proxy_to_server, ntohs(sock_out.sin_port), (struct sockaddr *)&from, ntohs(((struct sockaddr_in *)&from)->sin_port), IPPROTO_UDP) == -1) { syslog(LOG_ERR, "couldn't add rdr"); exit(1); } /* explicitly allow the packets to return back to the client (which pf * will see post-rdr) */ if (add_filter(1, PF_IN, (struct sockaddr *)&server, (struct sockaddr *)&from, ntohs(((struct sockaddr_in *)&from)->sin_port), IPPROTO_UDP) == -1) { syslog(LOG_ERR, "couldn't add pass in"); exit(1); } /* and just in case, to pass out from us to the server */ if (add_filter(1, PF_OUT, (struct sockaddr *)&proxy_to_server, (struct sockaddr *)&server, ntohs(((struct sockaddr_in *)&server)->sin_port), IPPROTO_UDP) == -1) { syslog(LOG_ERR, "couldn't add pass out"); exit(1); } if (do_commit() == -1) { syslog(LOG_ERR, "couldn't commit pf rules"); exit(1); } /* forward the initial tftp request and start the insanity */ if (send(out_fd, tp, reqsize, 0) < 0) { syslog(LOG_ERR, "couldn't forward tftp packet: %m"); exit(1); } /* allow the transfer to start to establish a state */ sleep(transwait); /* delete our rdr rule and clean up */ prepare_commit(1); do_commit(); return(0); } const char * opcode(int code) { static char str[6]; switch (code) { case 1: (void)snprintf(str, sizeof(str), "RRQ"); break; case 2: (void)snprintf(str, sizeof(str), "WRQ"); break; default: (void)snprintf(str, sizeof(str), "(%d)", code); break; } return (str); } const char * sock_ntop(struct sockaddr *sa) { static int n = 0; /* Cycle to next buffer. */ n = (n + 1) % NTOP_BUFS; ntop_buf[n][0] = '\0'; if (sa->sa_family == AF_INET) { struct sockaddr_in *sin = (struct sockaddr_in *)sa; return (inet_ntop(AF_INET, &sin->sin_addr, ntop_buf[n], sizeof ntop_buf[0])); } if (sa->sa_family == AF_INET6) { struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa; return (inet_ntop(AF_INET6, &sin6->sin6_addr, ntop_buf[n], sizeof ntop_buf[0])); } return (NULL); } u_int16_t pick_proxy_port(void) { return (IPPORT_HIFIRSTAUTO + (arc4random() % (IPPORT_HILASTAUTO - IPPORT_HIFIRSTAUTO))); } static void usage(void) { syslog(LOG_ERR, "usage: %s [-v] [-w transwait]", __progname); exit(1); }