1/* $OpenBSD: monitor.c,v 1.31 2023/03/08 04:43:05 guenther 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(void) 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)) == -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 freezero(pw, len); 288 289 switch (auth) { 290 case AUTH_FAILED: 291 /* Authentication failure */ 292 debugmsg("authentication failed"); 293 slavequit = 0; 294 send_data(fd_slave, &slavequit, 295 sizeof(slavequit)); 296 break; 297 case AUTH_SLAVE: 298 if (pledge("stdio rpath wpath cpath inet recvfd" 299 " sendfd proc tty getpw", NULL) == -1) 300 fatalx("pledge"); 301 /* User-privileged slave */ 302 debugmsg("user-privileged slave started"); 303 return; 304 /* NOTREACHED */ 305 case AUTH_MONITOR: 306 if (pledge("stdio inet sendfd recvfd proc", 307 NULL) == -1) 308 fatalx("pledge"); 309 /* Post-auth monitor */ 310 debugmsg("monitor went into post-auth phase"); 311 state = POSTAUTH; 312 setproctitle("%s: [priv post-auth]", 313 remotehost); 314 slavequit = 1; 315 316 send_data(fd_slave, &slavequit, 317 sizeof(slavequit)); 318 319 while (waitpid(preauth_slave_pid, NULL, 0) == -1 && 320 errno == EINTR) 321 ; 322 break; 323 default: 324 fatalx("bad return value from pass()"); 325 /* NOTREACHED */ 326 } 327 break; 328 case CMD_SOCKET: 329 debugmsg("CMD_SOCKET received"); 330 331 if (state != POSTAUTH) 332 fatalx("CMD_SOCKET received in invalid state"); 333 334 recv_data(fd_slave, &domain, sizeof(domain)); 335 if (domain != AF_INET && domain != AF_INET6) 336 fatalx("monitor received invalid addr family"); 337 338 s = socket(domain, SOCK_STREAM, 0); 339 serrno = errno; 340 341 send_fd(fd_slave, s); 342 if (s == -1) 343 send_data(fd_slave, &serrno, sizeof(serrno)); 344 else 345 close(s); 346 break; 347 case CMD_BIND: 348 debugmsg("CMD_BIND received"); 349 350 if (state != POSTAUTH) 351 fatalx("CMD_BIND received in invalid state"); 352 353 s = recv_fd(fd_slave); 354 355 recv_data(fd_slave, &salen, sizeof(salen)); 356 if (salen == 0 || salen > sizeof(sa)) 357 fatalx("monitor received invalid sockaddr len"); 358 359 bzero(&sa, sizeof(sa)); 360 recv_data(fd_slave, &sa, salen); 361 362 if (sa.su_si.si_len != salen) 363 fatalx("monitor received invalid sockaddr len"); 364 365 if (sa.su_si.si_family != AF_INET && 366 sa.su_si.si_family != AF_INET6) 367 fatalx("monitor received invalid addr family"); 368 369 err = bind(s, (struct sockaddr *)&sa, salen); 370 serrno = errno; 371 372 if (s >= 0) 373 close(s); 374 375 send_data(fd_slave, &err, sizeof(err)); 376 if (err == -1) 377 send_data(fd_slave, &serrno, sizeof(serrno)); 378 break; 379 default: 380 fatalx("monitor received unknown command %d", cmd); 381 /* NOTREACHED */ 382 } 383 } 384} 385 386void 387sig_pass_to_slave(int signo) 388{ 389 int olderrno = errno; 390 391 if (slave_pid > 0) 392 kill(slave_pid, signo); 393 394 errno = olderrno; 395} 396 397void 398sig_chld(int signo) 399{ 400 pid_t pid; 401 int stat, olderrno = errno; 402 403 do { 404 pid = waitpid(slave_pid, &stat, WNOHANG); 405 if (pid > 0) 406 _exit(0); 407 } while (pid == -1 && errno == EINTR); 408 409 errno = olderrno; 410} 411 412void 413kill_slave(char *reason) 414{ 415 if (slave_pid > 0) { 416 if (reason) 417 syslog(LOG_NOTICE, "kill slave %d: %s", 418 slave_pid, reason); 419 kill(slave_pid, SIGQUIT); 420 } 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("fatal error"); 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