monitor.c revision 1.12
1/* $OpenBSD: monitor.c,v 1.12 2006/01/20 16:51:38 moritz Exp $ */ 2 3/* 4 * Copyright (c) 2004 Moritz Jodeit <moritz@openbsd.org> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19#include <sys/types.h> 20#include <sys/socket.h> 21#include <sys/wait.h> 22#include <netinet/in.h> 23 24#include <errno.h> 25#include <fcntl.h> 26#include <limits.h> 27#include <paths.h> 28#include <pwd.h> 29#include <signal.h> 30#include <stdarg.h> 31#include <stdio.h> 32#include <stdlib.h> 33#include <string.h> 34#include <syslog.h> 35#include <unistd.h> 36 37#include "extern.h" 38#include "monitor.h" 39 40enum monitor_command { 41 CMD_USER, 42 CMD_PASS, 43 CMD_SOCKET, 44 CMD_BIND 45}; 46 47enum monitor_state { 48 PREAUTH, 49 POSTAUTH 50}; 51 52#ifdef HASSETPROCTITLE 53extern char remotehost[]; 54#endif 55extern char ttyline[20]; 56extern int debug; 57 58extern void set_slave_signals(void); 59 60int fd_monitor = -1; 61int fd_slave = -1; 62int nullfd; 63pid_t slave_pid = -1; 64enum monitor_state state = PREAUTH; 65 66void send_data(int, void *, size_t); 67void recv_data(int, void *, size_t); 68void handle_cmds(void); 69void set_monitor_signals(void); 70void sig_pass_to_slave(int); 71void sig_chld(int); 72void fatalx(char *, ...); 73void debugmsg(char *, ...); 74 75/* 76 * Send data over a socket and exit if something fails. 77 */ 78void 79send_data(int sock, void *buf, size_t len) 80{ 81 ssize_t n; 82 size_t pos = 0; 83 char *ptr = buf; 84 85 while (len > pos) { 86 switch (n = write(sock, ptr + pos, len - pos)) { 87 case 0: 88 kill_slave(); 89 _exit(0); 90 /* NOTREACHED */ 91 case -1: 92 if (errno != EINTR && errno != EAGAIN) 93 fatalx("send_data: %m"); 94 break; 95 default: 96 pos += n; 97 } 98 } 99} 100 101/* 102 * Receive data from socket and exit if something fails. 103 */ 104void 105recv_data(int sock, void *buf, size_t len) 106{ 107 ssize_t n; 108 size_t pos = 0; 109 char *ptr = buf; 110 111 while (len > pos) { 112 switch (n = read(sock, ptr + pos, len - pos)) { 113 case 0: 114 kill_slave(); 115 _exit(0); 116 /* NOTREACHED */ 117 case -1: 118 if (errno != EINTR && errno != EAGAIN) 119 fatalx("recv_data: %m"); 120 break; 121 default: 122 pos += n; 123 } 124 } 125} 126 127void 128set_monitor_signals(void) 129{ 130 struct sigaction act; 131 int i; 132 133 sigfillset(&act.sa_mask); 134 act.sa_flags = SA_RESTART; 135 136 act.sa_handler = SIG_DFL; 137 for (i = 1; i < _NSIG; i++) 138 sigaction(i, &act, NULL); 139 140 act.sa_handler = sig_chld; 141 sigaction(SIGCHLD, &act, NULL); 142 143 act.sa_handler = sig_pass_to_slave; 144 sigaction(SIGHUP, &act, NULL); 145 sigaction(SIGINT, &act, NULL); 146 sigaction(SIGQUIT, &act, NULL); 147 sigaction(SIGTERM, &act, NULL); 148} 149 150/* 151 * Creates the privileged monitor process. It returns twice. 152 * It returns 1 for the unprivileged slave process and 0 for the 153 * user-privileged slave process after successful authentication. 154 */ 155int 156monitor_init(void) 157{ 158 struct passwd *pw; 159 int pair[2]; 160 161 if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, pair) == -1) 162 fatalx("socketpair failed"); 163 164 fd_monitor = pair[0]; 165 fd_slave = pair[1]; 166 167 set_monitor_signals(); 168 169 slave_pid = fork(); 170 if (slave_pid == -1) 171 fatalx("fork of unprivileged slave failed"); 172 if (slave_pid == 0) { 173 /* Unprivileged slave */ 174 set_slave_signals(); 175 176 if ((pw = getpwnam(FTPD_PRIVSEP_USER)) == NULL) 177 fatalx("privilege separation user %s not found", 178 FTPD_PRIVSEP_USER); 179 180 if (chroot(pw->pw_dir) == -1) 181 fatalx("chroot %s: %m", pw->pw_dir); 182 if (chdir("/") == -1) 183 fatalx("chdir /: %m"); 184 185 if (setgroups(1, &pw->pw_gid) == -1) 186 fatalx("setgroups: %m"); 187 if (setegid(pw->pw_gid) == -1) 188 fatalx("setegid failed"); 189 if (setgid(pw->pw_gid) == -1) 190 fatalx("setgid failed"); 191 if (seteuid(pw->pw_uid) == -1) 192 fatalx("seteuid failed"); 193 if (setuid(pw->pw_uid) == -1) 194 fatalx("setuid failed"); 195 196 endpwent(); 197 close(fd_slave); 198 return (1); 199 } 200 201#ifdef HASSETPROCTITLE 202 setproctitle("%s: [priv pre-auth]", remotehost); 203#endif 204 205 handle_cmds(); 206 207 /* User-privileged slave */ 208 return (0); 209} 210 211/* 212 * Creates the user-privileged slave process. It is called 213 * from the privileged monitor process and returns twice. It returns 0 214 * for the user-privileged slave process and 1 for the monitor process. 215 */ 216int 217monitor_post_auth() 218{ 219 slave_pid = fork(); 220 if (slave_pid == -1) 221 fatalx("fork of user-privileged slave failed"); 222 223 snprintf(ttyline, sizeof(ttyline), "ftp%ld", 224 slave_pid == 0 ? (long)getpid() : (long)slave_pid); 225 226 if (slave_pid == 0) { 227 /* User privileged slave */ 228 close(fd_slave); 229 set_slave_signals(); 230 return (0); 231 } 232 233 /* We have to keep stdout open, because reply() needs it. */ 234 if ((nullfd = open(_PATH_DEVNULL, O_RDWR, 0)) == -1) 235 fatalx("cannot open %s: %m", _PATH_DEVNULL); 236 dup2(nullfd, STDIN_FILENO); 237 dup2(nullfd, STDERR_FILENO); 238 close(nullfd); 239 close(fd_monitor); 240 241 return (1); 242} 243 244/* 245 * Handles commands received from the slave process. It will not return 246 * except in one situation: After successful authentication it will 247 * return as the user-privileged slave process. 248 */ 249void 250handle_cmds(void) 251{ 252 enum monitor_command cmd; 253 enum auth_ret auth; 254 int err, s, slavequit, serrno, domain; 255 pid_t preauth_slave_pid; 256 size_t len; 257 struct sockaddr sa; 258 socklen_t salen; 259 char *name, *pw; 260 261 for (;;) { 262 recv_data(fd_slave, &cmd, sizeof(cmd)); 263 264 switch (cmd) { 265 case CMD_USER: 266 debugmsg("CMD_USER received"); 267 268 recv_data(fd_slave, &len, sizeof(len)); 269 if (len == 0 || len == SIZE_T_MAX) 270 fatalx("monitor received invalid user length"); 271 if ((name = malloc(len + 1)) == NULL) 272 fatalx("malloc: %m"); 273 recv_data(fd_slave, name, len); 274 name[len] = '\0'; 275 276 user(name); 277 free(name); 278 break; 279 case CMD_PASS: 280 debugmsg("CMD_PASS received"); 281 282 recv_data(fd_slave, &len, sizeof(len)); 283 if (len == 0 || len == SIZE_T_MAX) 284 fatalx("monitor received invalid pass length"); 285 if ((pw = malloc(len + 1)) == NULL) 286 fatalx("malloc: %m"); 287 recv_data(fd_slave, pw, len); 288 pw[len] = '\0'; 289 290 preauth_slave_pid = slave_pid; 291 292 auth = pass(pw); 293 bzero(pw, len); 294 free(pw); 295 296 switch (auth) { 297 case AUTH_FAILED: 298 /* Authentication failure */ 299 debugmsg("authentication failed"); 300 slavequit = 0; 301 send_data(fd_slave, &slavequit, 302 sizeof(slavequit)); 303 break; 304 case AUTH_SLAVE: 305 /* User-privileged slave */ 306 debugmsg("user-privileged slave started"); 307 return; 308 /* NOTREACHED */ 309 case AUTH_MONITOR: 310 /* Post-auth monitor */ 311 debugmsg("monitor went into post-auth phase"); 312 state = POSTAUTH; 313#ifdef HASSETPROCTITLE 314 setproctitle("%s: [priv post-auth]", 315 remotehost); 316#endif 317 slavequit = 1; 318 319 send_data(fd_slave, &slavequit, 320 sizeof(slavequit)); 321 322 while (waitpid(preauth_slave_pid, NULL, 0) < 0 323 && errno == EINTR) 324 ; 325 break; 326 default: 327 fatalx("bad return value from pass()"); 328 /* NOTREACHED */ 329 } 330 break; 331 case CMD_SOCKET: 332 debugmsg("CMD_SOCKET received"); 333 334 if (state != POSTAUTH) 335 fatalx("CMD_SOCKET received in invalid state"); 336 337 recv_data(fd_slave, &domain, sizeof(domain)); 338 if (domain != AF_INET && domain != AF_INET6) 339 fatalx("monitor received invalid addr family"); 340 341 s = socket(domain, SOCK_STREAM, 0); 342 serrno = errno; 343 344 send_fd(fd_slave, s); 345 if (s == -1) 346 send_data(fd_slave, &serrno, sizeof(serrno)); 347 else 348 close(s); 349 break; 350 case CMD_BIND: 351 debugmsg("CMD_BIND received"); 352 353 if (state != POSTAUTH) 354 fatalx("CMD_BIND received in invalid state"); 355 356 s = recv_fd(fd_slave); 357 358 recv_data(fd_slave, &salen, sizeof(salen)); 359 if (salen == 0 || salen > sizeof(sa)) 360 fatalx("monitor received invalid sockaddr len"); 361 362 bzero(&sa, sizeof(sa)); 363 recv_data(fd_slave, &sa, salen); 364 365 if (sa.sa_len != salen) 366 fatalx("monitor received invalid sockaddr len"); 367 368 if (sa.sa_family != AF_INET && sa.sa_family != AF_INET6) 369 fatalx("monitor received invalid addr family"); 370 371 err = bind(s, &sa, salen); 372 serrno = errno; 373 374 if (s >= 0) 375 close(s); 376 377 send_data(fd_slave, &err, sizeof(err)); 378 if (err == -1) 379 send_data(fd_slave, &serrno, sizeof(serrno)); 380 break; 381 default: 382 fatalx("monitor received unknown command %d", cmd); 383 /* NOTREACHED */ 384 } 385 } 386 /* NOTREACHED */ 387} 388 389void 390sig_pass_to_slave(int signo) 391{ 392 int olderrno = errno; 393 394 if (slave_pid > 0) 395 kill(slave_pid, signo); 396 397 errno = olderrno; 398} 399 400/* ARGSUSED */ 401void 402sig_chld(int signo) 403{ 404 pid_t pid; 405 int stat, olderrno = errno; 406 407 do { 408 pid = waitpid(slave_pid, &stat, WNOHANG); 409 if (pid > 0) 410 _exit(0); 411 } while (pid == -1 && errno == EINTR); 412 413 errno = olderrno; 414} 415 416void 417kill_slave(void) 418{ 419 if (slave_pid > 0) 420 kill(slave_pid, SIGQUIT); 421} 422 423void 424fatalx(char *fmt, ...) 425{ 426 va_list ap; 427 428 va_start(ap, fmt); 429 vsyslog(LOG_ERR, fmt, ap); 430 va_end(ap); 431 432 kill_slave(); 433 434 _exit(0); 435} 436 437void 438debugmsg(char *fmt, ...) 439{ 440 va_list ap; 441 442 if (debug) { 443 va_start(ap, fmt); 444 vsyslog(LOG_DEBUG, fmt, ap); 445 va_end(ap); 446 } 447} 448 449void 450monitor_user(char *name) 451{ 452 enum monitor_command cmd; 453 size_t len; 454 455 cmd = CMD_USER; 456 send_data(fd_monitor, &cmd, sizeof(cmd)); 457 458 len = strlen(name); 459 send_data(fd_monitor, &len, sizeof(len)); 460 if (len > 0) 461 send_data(fd_monitor, name, len); 462} 463 464int 465monitor_pass(char *pass) 466{ 467 enum monitor_command cmd; 468 int quitnow; 469 size_t len; 470 471 cmd = CMD_PASS; 472 send_data(fd_monitor, &cmd, sizeof(cmd)); 473 474 len = strlen(pass); 475 send_data(fd_monitor, &len, sizeof(len)); 476 if (len > 0) 477 send_data(fd_monitor, pass, len); 478 479 recv_data(fd_monitor, &quitnow, sizeof(quitnow)); 480 481 return (quitnow); 482} 483 484int 485monitor_socket(int domain) 486{ 487 enum monitor_command cmd; 488 int s, serrno; 489 490 cmd = CMD_SOCKET; 491 send_data(fd_monitor, &cmd, sizeof(cmd)); 492 send_data(fd_monitor, &domain, sizeof(domain)); 493 494 s = recv_fd(fd_monitor); 495 if (s == -1) { 496 recv_data(fd_monitor, &serrno, sizeof(serrno)); 497 errno = serrno; 498 } 499 500 return (s); 501} 502 503int 504monitor_bind(int s, struct sockaddr *name, socklen_t namelen) 505{ 506 enum monitor_command cmd; 507 int ret, serrno; 508 509 cmd = CMD_BIND; 510 send_data(fd_monitor, &cmd, sizeof(cmd)); 511 512 send_fd(fd_monitor, s); 513 send_data(fd_monitor, &namelen, sizeof(namelen)); 514 send_data(fd_monitor, name, namelen); 515 516 recv_data(fd_monitor, &ret, sizeof(ret)); 517 if (ret == -1) { 518 recv_data(fd_monitor, &serrno, sizeof(serrno)); 519 errno = serrno; 520 } 521 522 return (ret); 523} 524