privsep.c revision 1.1
1 /* $OpenBSD: privsep.c,v 1.8 2004/03/14 19:17:05 otto Exp $ */ 2 3 /* 4 * Copyright (c) 2003 Can Erkin Acar 5 * Copyright (c) 2003 Anil Madhavapeddy <anil (at) 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/ioctl.h> 20 #include <sys/types.h> 21 #include <sys/time.h> 22 #include <sys/socket.h> 23 #include <sys/ioctl.h> 24 25 #include <net/if.h> 26 #include <net/bpf.h> 27 28 #include <err.h> 29 #include <errno.h> 30 #include <fcntl.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_OPEN_LOG /* open logfile for appending */ 45 }; 46 47 static int priv_fd = -1; 48 static volatile pid_t child_pid = -1; 49 50 volatile sig_atomic_t gotsig_chld = 0; 51 52 static void sig_pass_to_chld(int); 53 static void sig_chld(int); 54 static int may_read(int, void *, size_t); 55 static void must_read(int, void *, size_t); 56 static void must_write(int, void *, size_t); 57 static int set_snaplen(int snap); 58 59 /* bpf filter expression common to parent and child */ 60 extern char *filter; 61 extern char *errbuf; 62 extern char *filename; 63 extern pcap_t *hpcap; 64 65 /* based on syslogd privsep */ 66 int 67 priv_init(void) 68 { 69 int i, fd, socks[2], cmd; 70 int snaplen, ret; 71 struct passwd *pw; 72 73 for (i = 1; i < _NSIG; i++) 74 signal(i, SIG_DFL); 75 76 /* Create sockets */ 77 if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1) 78 err(1, "socketpair() failed"); 79 80 pw = getpwnam("_pflogd"); 81 if (pw == NULL) 82 errx(1, "unknown user _pflogd"); 83 endpwent(); 84 85 child_pid = fork(); 86 if (child_pid < 0) 87 err(1, "fork() failed"); 88 89 if (!child_pid) { 90 gid_t gidset[1]; 91 92 /* Child - drop privileges and return */ 93 if (chroot(pw->pw_dir) != 0) 94 err(1, "unable to chroot"); 95 if (chdir("/") != 0) 96 err(1, "unable to chdir"); 97 98 gidset[0] = pw->pw_gid; 99 if (setgroups(1, gidset) == -1) 100 err(1, "setgroups() failed"); 101 if (setegid(pw->pw_gid) == -1) 102 err(1, "setegid() failed"); 103 if (setgid(pw->pw_gid) == -1) 104 err(1, "setgid() failed"); 105 if (seteuid(pw->pw_uid) == -1) 106 err(1, "seteuid() failed"); 107 if (setuid(pw->pw_uid) == -1) 108 err(1, "setuid() failed"); 109 close(socks[0]); 110 priv_fd = socks[1]; 111 return 0; 112 } 113 114 /* Father */ 115 /* Pass ALRM/TERM/HUP through to child, and accept CHLD */ 116 signal(SIGALRM, sig_pass_to_chld); 117 signal(SIGTERM, sig_pass_to_chld); 118 signal(SIGHUP, sig_pass_to_chld); 119 signal(SIGCHLD, sig_chld); 120 121 setproctitle("[priv]"); 122 close(socks[1]); 123 124 while (!gotsig_chld) { 125 if (may_read(socks[0], &cmd, sizeof(int))) 126 break; 127 switch (cmd) { 128 case PRIV_SET_SNAPLEN: 129 logmsg(LOG_DEBUG, 130 "[priv]: msg PRIV_SET_SNAPLENGTH received"); 131 must_read(socks[0], &snaplen, sizeof(int)); 132 133 ret = set_snaplen(snaplen); 134 if (ret) { 135 logmsg(LOG_NOTICE, 136 "[priv]: set_snaplen failed for snaplen %d", 137 snaplen); 138 } 139 140 must_write(socks[0], &ret, sizeof(int)); 141 break; 142 143 case PRIV_OPEN_LOG: 144 logmsg(LOG_DEBUG, 145 "[priv]: msg PRIV_OPEN_LOG received"); 146 /* create or append logs but do not follow symlinks */ 147 fd = open(filename, 148 O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW, 149 0600); 150 if (fd < 0) 151 logmsg(LOG_NOTICE, 152 "[priv]: failed to open %s: %s", 153 filename, strerror(errno)); 154 send_fd(socks[0], fd); 155 close(fd); 156 break; 157 158 default: 159 logmsg(LOG_ERR, "[priv]: unknown command %d", cmd); 160 _exit(1); 161 /* NOTREACHED */ 162 } 163 } 164 165 _exit(1); 166 } 167 168 /* this is called from parent */ 169 static int 170 set_snaplen(int snap) 171 { 172 if (hpcap == NULL) 173 return (1); 174 175 hpcap->snapshot = snap; 176 set_pcap_filter(); 177 178 return 0; 179 } 180 181 182 /* 183 * send the snaplength to privileged process 184 */ 185 int 186 priv_set_snaplen(int snaplen) 187 { 188 int cmd, ret; 189 190 if (priv_fd < 0) 191 errx(1, "%s: called from privileged portion", __func__); 192 193 cmd = PRIV_SET_SNAPLEN; 194 195 must_write(priv_fd, &cmd, sizeof(int)); 196 must_write(priv_fd, &snaplen, sizeof(int)); 197 198 must_read(priv_fd, &ret, sizeof(int)); 199 200 /* also set hpcap->snapshot in child */ 201 if (ret == 0) 202 hpcap->snapshot = snaplen; 203 204 return (ret); 205 } 206 207 /* Open log-file */ 208 int 209 priv_open_log(void) 210 { 211 int cmd, fd; 212 213 if (priv_fd < 0) 214 errx(1, "%s: called from privileged portion\n", __func__); 215 216 cmd = PRIV_OPEN_LOG; 217 must_write(priv_fd, &cmd, sizeof(int)); 218 fd = receive_fd(priv_fd); 219 220 return (fd); 221 } 222 223 /* If priv parent gets a TERM or HUP, pass it through to child instead */ 224 static void 225 sig_pass_to_chld(int sig) 226 { 227 int oerrno = errno; 228 229 if (child_pid != -1) 230 kill(child_pid, sig); 231 errno = oerrno; 232 } 233 234 /* if parent gets a SIGCHLD, it will exit */ 235 static void 236 sig_chld(int sig) 237 { 238 gotsig_chld = 1; 239 } 240 241 /* Read all data or return 1 for error. */ 242 static int 243 may_read(int fd, void *buf, size_t n) 244 { 245 char *s = buf; 246 ssize_t res, pos = 0; 247 248 while (n > pos) { 249 res = read(fd, s + pos, n - pos); 250 switch (res) { 251 case -1: 252 if (errno == EINTR || errno == EAGAIN) 253 continue; 254 case 0: 255 return (1); 256 default: 257 pos += res; 258 } 259 } 260 return (0); 261 } 262 263 /* Read data with the assertion that it all must come through, or 264 * else abort the process. Based on atomicio() from openssh. */ 265 static void 266 must_read(int fd, void *buf, size_t n) 267 { 268 char *s = buf; 269 ssize_t res, pos = 0; 270 271 while (n > pos) { 272 res = read(fd, s + pos, n - pos); 273 switch (res) { 274 case -1: 275 if (errno == EINTR || errno == EAGAIN) 276 continue; 277 case 0: 278 _exit(0); 279 default: 280 pos += res; 281 } 282 } 283 } 284 285 /* Write data with the assertion that it all has to be written, or 286 * else abort the process. Based on atomicio() from openssh. */ 287 static void 288 must_write(int fd, void *buf, size_t n) 289 { 290 char *s = buf; 291 ssize_t res, pos = 0; 292 293 while (n > pos) { 294 res = write(fd, s + pos, n - pos); 295 switch (res) { 296 case -1: 297 if (errno == EINTR || errno == EAGAIN) 298 continue; 299 case 0: 300 _exit(0); 301 default: 302 pos += res; 303 } 304 } 305 } 306
Indexes created Thu Oct 30 03:10:01 GMT 2025