monitor.c revision 1.24
1/* $OpenBSD: monitor.c,v 1.24 2016/04/25 15:43:34 deraadt 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 <paths.h> 27#include <pwd.h> 28#include <signal.h> 29#include <stdarg.h> 30#include <stdint.h> 31#include <stdio.h> 32#include <stdlib.h> 33#include <string.h> 34#include <syslog.h> 35#include <unistd.h> 36 37#include "monitor.h" 38#include "extern.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 52extern char remotehost[]; 53extern char ttyline[20]; 54extern int debug; 55 56extern void set_slave_signals(void); 57 58int fd_monitor = -1; 59int fd_slave = -1; 60int nullfd; 61pid_t slave_pid = -1; 62enum monitor_state state = PREAUTH; 63 64void send_data(int, void *, size_t); 65void recv_data(int, void *, size_t); 66void handle_cmds(void); 67void set_monitor_signals(void); 68void sig_pass_to_slave(int); 69void sig_chld(int); 70void fatalx(char *, ...); 71void debugmsg(char *, ...); 72 73/* 74 * Send data over a socket and exit if something fails. 75 */ 76void 77send_data(int sock, void *buf, size_t len) 78{ 79 ssize_t n; 80 size_t pos = 0; 81 char *ptr = buf; 82 83 while (len > pos) { 84 switch (n = write(sock, ptr + pos, len - pos)) { 85 case 0: 86 kill_slave("write failure"); 87 _exit(0); 88 /* NOTREACHED */ 89 case -1: 90 if (errno != EINTR && errno != EAGAIN) 91 fatalx("send_data: %m"); 92 break; 93 default: 94 pos += n; 95 } 96 } 97} 98 99/* 100 * Receive data from socket and exit if something fails. 101 */ 102void 103recv_data(int sock, void *buf, size_t len) 104{ 105 ssize_t n; 106 size_t pos = 0; 107 char *ptr = buf; 108 109 while (len > pos) { 110 switch (n = read(sock, ptr + pos, len - pos)) { 111 case 0: 112 kill_slave(NULL); 113 _exit(0); 114 /* NOTREACHED */ 115 case -1: 116 if (errno != EINTR && errno != EAGAIN) 117 fatalx("recv_data: %m"); 118 break; 119 default: 120 pos += n; 121 } 122 } 123} 124 125void 126set_monitor_signals(void) 127{ 128 struct sigaction act; 129 int i; 130 131 sigfillset(&act.sa_mask); 132 act.sa_flags = SA_RESTART; 133 134 act.sa_handler = SIG_DFL; 135 for (i = 1; i < _NSIG; i++) 136 sigaction(i, &act, NULL); 137 138 act.sa_handler = sig_chld; 139 sigaction(SIGCHLD, &act, NULL); 140 141 act.sa_handler = sig_pass_to_slave; 142 sigaction(SIGHUP, &act, NULL); 143 sigaction(SIGINT, &act, NULL); 144 sigaction(SIGQUIT, &act, NULL); 145 sigaction(SIGTERM, &act, NULL); 146} 147 148/* 149 * Creates the privileged monitor process. It returns twice. 150 * It returns 1 for the unprivileged slave process and 0 for the 151 * user-privileged slave process after successful authentication. 152 */ 153int 154monitor_init(void) 155{ 156 struct passwd *pw; 157 int pair[2]; 158 159 if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, pair) == -1) 160 fatalx("socketpair failed"); 161 162 fd_monitor = pair[0]; 163 fd_slave = pair[1]; 164 165 set_monitor_signals(); 166 167 slave_pid = fork(); 168 if (slave_pid == -1) 169 fatalx("fork of unprivileged slave failed"); 170 if (slave_pid == 0) { 171 /* Unprivileged slave */ 172 set_slave_signals(); 173 174 if ((pw = getpwnam(FTPD_PRIVSEP_USER)) == NULL) 175 fatalx("privilege separation user %s not found", 176 FTPD_PRIVSEP_USER); 177 178 if (chroot(pw->pw_dir) == -1) 179 fatalx("chroot %s: %m", pw->pw_dir); 180 if (chdir("/") == -1) 181 fatalx("chdir /: %m"); 182 183 if (setgroups(1, &pw->pw_gid) == -1) 184 fatalx("setgroups: %m"); 185 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) 186 fatalx("setresgid failed"); 187 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) 188 fatalx("setresuid failed"); 189 190 endpwent(); 191 close(fd_slave); 192 return (1); 193 } 194 195 setproctitle("%s: [priv pre-auth]", remotehost); 196 197 handle_cmds(); 198 199 /* User-privileged slave */ 200 return (0); 201} 202 203/* 204 * Creates the user-privileged slave process. It is called 205 * from the privileged monitor process and returns twice. It returns 0 206 * for the user-privileged slave process and 1 for the monitor process. 207 */ 208int 209monitor_post_auth() 210{ 211 slave_pid = fork(); 212 if (slave_pid == -1) 213 fatalx("fork of user-privileged slave failed"); 214 215 snprintf(ttyline, sizeof(ttyline), "ftp%ld", 216 slave_pid == 0 ? (long)getpid() : (long)slave_pid); 217 218 if (slave_pid == 0) { 219 /* User privileged slave */ 220 close(fd_slave); 221 set_slave_signals(); 222 return (0); 223 } 224 225 /* We have to keep stdout open, because reply() needs it. */ 226 if ((nullfd = open(_PATH_DEVNULL, O_RDWR, 0)) == -1) 227 fatalx("cannot open %s: %m", _PATH_DEVNULL); 228 dup2(nullfd, STDIN_FILENO); 229 dup2(nullfd, STDERR_FILENO); 230 close(nullfd); 231 close(fd_monitor); 232 233 return (1); 234} 235 236/* 237 * Handles commands received from the slave process. It will not return 238 * except in one situation: After successful authentication it will 239 * return as the user-privileged slave process. 240 */ 241void 242handle_cmds(void) 243{ 244 enum monitor_command cmd; 245 enum auth_ret auth; 246 int err, s, slavequit, serrno, domain; 247 pid_t preauth_slave_pid; 248 size_t len; 249 union sockunion sa; 250 socklen_t salen; 251 char *name, *pw; 252 253 for (;;) { 254 recv_data(fd_slave, &cmd, sizeof(cmd)); 255 256 switch (cmd) { 257 case CMD_USER: 258 debugmsg("CMD_USER received"); 259 260 recv_data(fd_slave, &len, sizeof(len)); 261 if (len == SIZE_MAX) 262 fatalx("monitor received invalid user length"); 263 if ((name = malloc(len + 1)) == NULL) 264 fatalx("malloc: %m"); 265 if (len > 0) 266 recv_data(fd_slave, name, len); 267 name[len] = '\0'; 268 269 user(name); 270 free(name); 271 break; 272 case CMD_PASS: 273 debugmsg("CMD_PASS received"); 274 275 recv_data(fd_slave, &len, sizeof(len)); 276 if (len == SIZE_MAX) 277 fatalx("monitor received invalid pass length"); 278 if ((pw = malloc(len + 1)) == NULL) 279 fatalx("malloc: %m"); 280 if (len > 0) 281 recv_data(fd_slave, pw, len); 282 pw[len] = '\0'; 283 284 preauth_slave_pid = slave_pid; 285 286 auth = pass(pw); 287 explicit_bzero(pw, len); 288 free(pw); 289 290 switch (auth) { 291 case AUTH_FAILED: 292 /* Authentication failure */ 293 debugmsg("authentication failed"); 294 slavequit = 0; 295 send_data(fd_slave, &slavequit, 296 sizeof(slavequit)); 297 break; 298 case AUTH_SLAVE: 299 /* User-privileged slave */ 300 debugmsg("user-privileged slave started"); 301 return; 302 /* NOTREACHED */ 303 case AUTH_MONITOR: 304 /* Post-auth monitor */ 305 debugmsg("monitor went into post-auth phase"); 306 state = POSTAUTH; 307 setproctitle("%s: [priv post-auth]", 308 remotehost); 309 slavequit = 1; 310 311 send_data(fd_slave, &slavequit, 312 sizeof(slavequit)); 313 314 while (waitpid(preauth_slave_pid, NULL, 0) < 0 && 315 errno == EINTR) 316 ; 317 break; 318 default: 319 fatalx("bad return value from pass()"); 320 /* NOTREACHED */ 321 } 322 break; 323 case CMD_SOCKET: 324 debugmsg("CMD_SOCKET received"); 325 326 if (state != POSTAUTH) 327 fatalx("CMD_SOCKET received in invalid state"); 328 329 recv_data(fd_slave, &domain, sizeof(domain)); 330 if (domain != AF_INET && domain != AF_INET6) 331 fatalx("monitor received invalid addr family"); 332 333 s = socket(domain, SOCK_STREAM, 0); 334 serrno = errno; 335 336 send_fd(fd_slave, s); 337 if (s == -1) 338 send_data(fd_slave, &serrno, sizeof(serrno)); 339 else 340 close(s); 341 break; 342 case CMD_BIND: 343 debugmsg("CMD_BIND received"); 344 345 if (state != POSTAUTH) 346 fatalx("CMD_BIND received in invalid state"); 347 348 s = recv_fd(fd_slave); 349 350 recv_data(fd_slave, &salen, sizeof(salen)); 351 if (salen == 0 || salen > sizeof(sa)) 352 fatalx("monitor received invalid sockaddr len"); 353 354 bzero(&sa, sizeof(sa)); 355 recv_data(fd_slave, &sa, salen); 356 357 if (sa.su_si.si_len != salen) 358 fatalx("monitor received invalid sockaddr len"); 359 360 if (sa.su_si.si_family != AF_INET && 361 sa.su_si.si_family != AF_INET6) 362 fatalx("monitor received invalid addr family"); 363 364 err = bind(s, (struct sockaddr *)&sa, salen); 365 serrno = errno; 366 367 if (s >= 0) 368 close(s); 369 370 send_data(fd_slave, &err, sizeof(err)); 371 if (err == -1) 372 send_data(fd_slave, &serrno, sizeof(serrno)); 373 break; 374 default: 375 fatalx("monitor received unknown command %d", cmd); 376 /* NOTREACHED */ 377 } 378 } 379} 380 381void 382sig_pass_to_slave(int signo) 383{ 384 int olderrno = errno; 385 386 if (slave_pid > 0) 387 kill(slave_pid, signo); 388 389 errno = olderrno; 390} 391 392/* ARGSUSED */ 393void 394sig_chld(int signo) 395{ 396 pid_t pid; 397 int stat, olderrno = errno; 398 399 do { 400 pid = waitpid(slave_pid, &stat, WNOHANG); 401 if (pid > 0) 402 _exit(0); 403 } while (pid == -1 && errno == EINTR); 404 405 errno = olderrno; 406} 407 408void 409kill_slave(char *reason) 410{ 411 if (slave_pid > 0) { 412 if (reason) 413 syslog(LOG_NOTICE, "kill slave %d: %s", 414 slave_pid, reason); 415 kill(slave_pid, SIGQUIT); 416 } 417} 418 419void 420fatalx(char *fmt, ...) 421{ 422 va_list ap; 423 424 va_start(ap, fmt); 425 vsyslog(LOG_ERR, fmt, ap); 426 va_end(ap); 427 428 kill_slave("fatal error"); 429 430 _exit(0); 431} 432 433void 434debugmsg(char *fmt, ...) 435{ 436 va_list ap; 437 438 if (debug) { 439 va_start(ap, fmt); 440 vsyslog(LOG_DEBUG, fmt, ap); 441 va_end(ap); 442 } 443} 444 445void 446monitor_user(char *name) 447{ 448 enum monitor_command cmd; 449 size_t len; 450 451 cmd = CMD_USER; 452 send_data(fd_monitor, &cmd, sizeof(cmd)); 453 454 len = strlen(name); 455 send_data(fd_monitor, &len, sizeof(len)); 456 if (len > 0) 457 send_data(fd_monitor, name, len); 458} 459 460int 461monitor_pass(char *pass) 462{ 463 enum monitor_command cmd; 464 int quitnow; 465 size_t len; 466 467 cmd = CMD_PASS; 468 send_data(fd_monitor, &cmd, sizeof(cmd)); 469 470 len = strlen(pass); 471 send_data(fd_monitor, &len, sizeof(len)); 472 if (len > 0) 473 send_data(fd_monitor, pass, len); 474 475 recv_data(fd_monitor, &quitnow, sizeof(quitnow)); 476 477 return (quitnow); 478} 479 480int 481monitor_socket(int domain) 482{ 483 enum monitor_command cmd; 484 int s, serrno; 485 486 cmd = CMD_SOCKET; 487 send_data(fd_monitor, &cmd, sizeof(cmd)); 488 send_data(fd_monitor, &domain, sizeof(domain)); 489 490 s = recv_fd(fd_monitor); 491 if (s == -1) { 492 recv_data(fd_monitor, &serrno, sizeof(serrno)); 493 errno = serrno; 494 } 495 496 return (s); 497} 498 499int 500monitor_bind(int s, struct sockaddr *name, socklen_t namelen) 501{ 502 enum monitor_command cmd; 503 int ret, serrno; 504 505 cmd = CMD_BIND; 506 send_data(fd_monitor, &cmd, sizeof(cmd)); 507 508 send_fd(fd_monitor, s); 509 send_data(fd_monitor, &namelen, sizeof(namelen)); 510 send_data(fd_monitor, name, namelen); 511 512 recv_data(fd_monitor, &ret, sizeof(ret)); 513 if (ret == -1) { 514 recv_data(fd_monitor, &serrno, sizeof(serrno)); 515 errno = serrno; 516 } 517 518 return (ret); 519} 520