1 /* $OpenBSD: privsep.c,v 1.22 2016/01/16 03:17:48 canacar Exp $ */ 2 3 /* 4 * Copyright (c) 2003 Can Erkin Acar 5 * Copyright (c) 2003 Anil Madhavapeddy <anil@recoil.org> 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 #include <sys/types.h> 20 #include <sys/time.h> 21 #include <sys/socket.h> 22 #include <sys/ioctl.h> 23 24 #include <net/if.h> 25 #include <net/bpf.h> 26 27 #include <err.h> 28 #include <errno.h> 29 #include <fcntl.h> 30 #include <limits.h> 31 #include <pcap.h> 32 #include <pcap-int.h> 33 #include <pwd.h> 34 #include <signal.h> 35 #include <stdio.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <syslog.h> 39 #include <unistd.h> 40 #include "pflogd.h" 41 42 enum cmd_types { 43 PRIV_SET_SNAPLEN, /* set the snaplength */ 44 PRIV_MOVE_LOG, /* move logfile away */ 45 PRIV_OPEN_LOG, /* open logfile for appending */ 46 }; 47 48 static int priv_fd = -1; 49 static volatile pid_t child_pid = -1; 50 51 volatile sig_atomic_t gotsig_chld = 0; 52 53 static void sig_pass_to_chld(int); 54 static void sig_chld(int); 55 static int may_read(int, void *, size_t); 56 static void must_read(int, void *, size_t); 57 static void must_write(int, void *, size_t); 58 static int set_snaplen(int snap); 59 static int move_log(const char *name); 60 61 extern char *filename; 62 extern pcap_t *hpcap; 63 64 /* based on syslogd privsep */ 65 int 66 priv_init(void) 67 { 68 int i, bpfd = -1, socks[2], cmd; 69 int snaplen, ret, olderrno; 70 struct passwd *pw; 71 72 for (i = 1; i < _NSIG; i++) 73 signal(i, SIG_DFL); 74 75 /* Create sockets */ 76 if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1) 77 err(1, "socketpair() failed"); 78 79 pw = getpwnam("_pflogd"); 80 if (pw == NULL) 81 errx(1, "unknown user _pflogd"); 82 endpwent(); 83 84 child_pid = fork(); 85 if (child_pid < 0) 86 err(1, "fork() failed"); 87 88 if (!child_pid) { 89 gid_t gidset[1]; 90 91 /* Child - drop privileges and return */ 92 if (chroot(pw->pw_dir) != 0) 93 err(1, "unable to chroot"); 94 if (chdir("/") != 0) 95 err(1, "unable to chdir"); 96 97 gidset[0] = pw->pw_gid; 98 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) 99 err(1, "setresgid() failed"); 100 if (setgroups(1, gidset) == -1) 101 err(1, "setgroups() failed"); 102 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) 103 err(1, "setresuid() failed"); 104 close(socks[0]); 105 priv_fd = socks[1]; 106 return 0; 107 } 108 109 /* Father */ 110 /* Pass ALRM/TERM/HUP/INT/QUIT through to child, and accept CHLD */ 111 signal(SIGALRM, sig_pass_to_chld); 112 signal(SIGTERM, sig_pass_to_chld); 113 signal(SIGHUP, sig_pass_to_chld); 114 signal(SIGINT, sig_pass_to_chld); 115 signal(SIGQUIT, sig_pass_to_chld); 116 signal(SIGCHLD, sig_chld); 117 118 setproctitle("[priv]"); 119 close(socks[1]); 120 121 122 #if notyet 123 /* This needs to do bpf ioctl */ 124 if (pledge("stdio rpath wpath cpath ioctl sendfd", NULL) == -1) 125 err(1, "pledge"); 126 #endif 127 while (!gotsig_chld) { 128 if (may_read(socks[0], &cmd, sizeof(int))) 129 break; 130 switch (cmd) { 131 case PRIV_SET_SNAPLEN: 132 logmsg(LOG_DEBUG, 133 "[priv]: msg PRIV_SET_SNAPLENGTH received"); 134 must_read(socks[0], &snaplen, sizeof(int)); 135 136 ret = set_snaplen(snaplen); 137 if (ret) { 138 logmsg(LOG_NOTICE, 139 "[priv]: set_snaplen failed for snaplen %d", 140 snaplen); 141 } 142 143 must_write(socks[0], &ret, sizeof(int)); 144 break; 145 146 case PRIV_OPEN_LOG: 147 logmsg(LOG_DEBUG, 148 "[priv]: msg PRIV_OPEN_LOG received"); 149 /* create or append logs but do not follow symlinks */ 150 if (bpfd != -1) { 151 close(bpfd); 152 bpfd = -1; 153 } 154 bpfd = open(filename, 155 O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW, 156 0600); 157 olderrno = errno; 158 send_fd(socks[0], bpfd); 159 if (bpfd < 0) 160 logmsg(LOG_NOTICE, 161 "[priv]: failed to open %s: %s", 162 filename, strerror(olderrno)); 163 break; 164 165 case PRIV_MOVE_LOG: 166 logmsg(LOG_DEBUG, 167 "[priv]: msg PRIV_MOVE_LOG received"); 168 ret = move_log(filename); 169 must_write(socks[0], &ret, sizeof(int)); 170 break; 171 172 default: 173 logmsg(LOG_ERR, "[priv]: unknown command %d", cmd); 174 _exit(1); 175 /* NOTREACHED */ 176 } 177 } 178 179 _exit(1); 180 } 181 182 /* this is called from parent */ 183 static int 184 set_snaplen(int snap) 185 { 186 if (hpcap == NULL) 187 return (1); 188 189 hpcap->snapshot = snap; 190 set_pcap_filter(); 191 192 return 0; 193 } 194 195 static int 196 move_log(const char *name) 197 { 198 char ren[PATH_MAX]; 199 int len; 200 201 for (;;) { 202 int fd; 203 204 len = snprintf(ren, sizeof(ren), "%s.bad.XXXXXXXX", name); 205 if (len >= sizeof(ren)) { 206 logmsg(LOG_ERR, "[priv] new name too long"); 207 return (1); 208 } 209 210 /* lock destination */ 211 fd = mkstemp(ren); 212 if (fd >= 0) { 213 close(fd); 214 break; 215 } 216 if (errno != EINTR) { 217 logmsg(LOG_ERR, "[priv] failed to create new name: %s", 218 strerror(errno)); 219 return (1); 220 } 221 } 222 223 if (rename(name, ren)) { 224 logmsg(LOG_ERR, "[priv] failed to rename %s to %s: %s", 225 name, ren, strerror(errno)); 226 unlink(ren); 227 return (1); 228 } 229 230 logmsg(LOG_NOTICE, 231 "[priv]: log file %s moved to %s", name, ren); 232 233 return (0); 234 } 235 236 /* 237 * send the snaplength to privileged process 238 */ 239 int 240 priv_set_snaplen(int snaplen) 241 { 242 int cmd, ret; 243 244 if (priv_fd < 0) 245 errx(1, "%s: called from privileged portion", __func__); 246 247 cmd = PRIV_SET_SNAPLEN; 248 249 must_write(priv_fd, &cmd, sizeof(int)); 250 must_write(priv_fd, &snaplen, sizeof(int)); 251 252 must_read(priv_fd, &ret, sizeof(int)); 253 254 /* also set hpcap->snapshot in child */ 255 if (ret == 0) 256 hpcap->snapshot = snaplen; 257 258 return (ret); 259 } 260 261 /* Open log-file */ 262 int 263 priv_open_log(void) 264 { 265 int cmd, fd; 266 267 if (priv_fd < 0) 268 errx(1, "%s: called from privileged portion", __func__); 269 270 cmd = PRIV_OPEN_LOG; 271 must_write(priv_fd, &cmd, sizeof(int)); 272 fd = receive_fd(priv_fd); 273 274 return (fd); 275 } 276 277 /* Move-away and reopen log-file */ 278 int 279 priv_move_log(void) 280 { 281 int cmd, ret; 282 283 if (priv_fd < 0) 284 errx(1, "%s: called from privileged portion", __func__); 285 286 cmd = PRIV_MOVE_LOG; 287 must_write(priv_fd, &cmd, sizeof(int)); 288 must_read(priv_fd, &ret, sizeof(int)); 289 290 return (ret); 291 } 292 293 /* If priv parent gets a TERM or HUP, pass it through to child instead */ 294 static void 295 sig_pass_to_chld(int sig) 296 { 297 int oerrno = errno; 298 299 if (child_pid != -1) 300 kill(child_pid, sig); 301 errno = oerrno; 302 } 303 304 /* if parent gets a SIGCHLD, it will exit */ 305 static void 306 sig_chld(int sig) 307 { 308 gotsig_chld = 1; 309 } 310 311 /* Read all data or return 1 for error. */ 312 static int 313 may_read(int fd, void *buf, size_t n) 314 { 315 char *s = buf; 316 ssize_t res, pos = 0; 317 318 while (n > pos) { 319 res = read(fd, s + pos, n - pos); 320 switch (res) { 321 case -1: 322 if (errno == EINTR || errno == EAGAIN) 323 continue; 324 case 0: 325 return (1); 326 default: 327 pos += res; 328 } 329 } 330 return (0); 331 } 332 333 /* Read data with the assertion that it all must come through, or 334 * else abort the process. Based on atomicio() from openssh. */ 335 static void 336 must_read(int fd, void *buf, size_t n) 337 { 338 char *s = buf; 339 ssize_t res, pos = 0; 340 341 while (n > pos) { 342 res = read(fd, s + pos, n - pos); 343 switch (res) { 344 case -1: 345 if (errno == EINTR || errno == EAGAIN) 346 continue; 347 case 0: 348 _exit(0); 349 default: 350 pos += res; 351 } 352 } 353 } 354 355 /* Write data with the assertion that it all has to be written, or 356 * else abort the process. Based on atomicio() from openssh. */ 357 static void 358 must_write(int fd, void *buf, size_t n) 359 { 360 char *s = buf; 361 ssize_t res, pos = 0; 362 363 while (n > pos) { 364 res = write(fd, s + pos, n - pos); 365 switch (res) { 366 case -1: 367 if (errno == EINTR || errno == EAGAIN) 368 continue; 369 case 0: 370 _exit(0); 371 default: 372 pos += res; 373 } 374 } 375 } 376